,illustration3 ,,boiling ,,water ,,in ,a ,,paper ,,case4 ,illustration3 ,,drawing ,a ,,slip ,,of ,,paper ,,from ,,beneath ,a ,,coin4 ,illustration3 ,,the ,,talking ,,head4 ,,popular ,,scientific ,,recreations ,,in ,,natural ,,philosophy1 ,,astronomy1 ,,geology1 ,,chemistry1 ,,etc41 ,,etc41 ,,etc4 ,translated and ,enlarged from 8,les ,rcrations ,scientifiques0 ,,of ,,gaston ,,tissandier4 7,editor of 8,la ,nature407 ,,profusely ,,illustrated4 ,london3 ,,ward1 ,,lock1 ,,and ,,co41 ,,warwick ,,house1 ,,salisbury ,,square1 ,e4,c4 ,,new ,,york3 #aj1 ,,bond ,,street4 ,,preface4 ,a learned mathematician of the seventeenth century1 ,ozanam by name1 a member of the ,academy of ,sciences and author of several distinguished works1 did not think it derogatory to his dignity to write1 under the title of 8,mathematical and ,physical ,recreations10 a book designed for the amusement of youth1 in which science lends itself to every pastime1 even jugglery and tricks of legerdemain4 8,jeux d'esprit0 says ,ozanam1 8are for all seasons and all ages2 they instruct the young1 they amuse the old1 they are welcomed by the rich1 and are not above the reach of the poor40 ,the object of the book now presented to the reader is also to instruct while it amuses1 but we have not thought proper to make use1 as ,ozanam did1 of any physical feats1 so called amusing4 ,such do not constitute experiments1 and are but ingenious deceptions1 intended to disguise the true mode of operation1 and we have not desired to make use of or popularise such methods4 ,we wish1 on the contrary1 that every game we describe1 every pastime or amusement of which we give the exposition1 should be rigorously based on the scientific method1 and looked upon as a genuine exercise in physics1 chemistry1 mechanics1 or natural science4 ,it does not appear to us desirable to teach deception1 even in play4 ,science in the open air1 in the fields1 in the sunshine1 is our first study2 we point out how1 in the country1 it is possible1 pleasantly and unceasingly1 to occupy one's leisure in observing nature1 in capturing insects or aquatic animals1 or in noting atmospheric phenomena4 ,we next teach a complete course of physics without any apparatus1 and point out the methods for studying the different phenomena of heat1 light1 optics1 and electricity1 by means of a simple water-bottle1 tumbler1 stick of sealing-wax1 and other ordinary objects1 such as everyone has at hand4 ,a series of chemical experiments1 performed by means of some phials and inexpensive appliances1 completes that part of the book relating to the physical sciences4 ,another kind of recreation1 both intelligent and useful1 consists in collecting the ingenious inventions which are constantly being supplied to our requirements by the applied sciences1 and learning how to use them4 ,we have collected a number of mechanical inventions and appliances1 with which most ingenious and skilful people will wish to supply themselves1 from ,edison's electric pen1 or the chromograph1 which will produce a large number of copies of a letter1 drawing1 etc41 to the more complicated1 but not less valuable contrivances1 for making science useful in the house4 ,having described some scientific toys for the young1 we have endeavoured to point out those interesting to persons of riper years1 and have grouped together curious systems of locomotion1 and ingenious mechanical appliances1 such as small steam-boats1 ice-boats1 swimming apparatus1 etc41 under proper heads4 ,in addition to the foregoing subjects1 we have included some of the experimental details of ,chemical ,science1 with illustrations4 ,we have added a chapter upon ,arial ,navigation and ,ballooning1 with anecdotes of some of our celebrated aronauts4 ,we have also enlarged upon ,light1 ,sound1 ,heat1 ,physical ,geography1 ,mineralogy1 ,geology1 ,electrical ,appliances1 the ,electric ,light1 and most of the latest adaptations of electricity4 ,it will be seen1 therefore1 that the present work is not only intended for the young2 everyone1 it is hoped1 will find in it something interesting and also profitable1 which1 if not desired for self-instruction1 may at any rate be turned to account as a means of teaching others that science1 which is universal1 can1 when rightly apprehended1 preside even over our pleasures and amusements4 ,,the ,,editor4 ,,contents4 ,,chapter ,i4--,,introductory4 ,,page ,science and ,recreation--,the ,book of ,nature--,the ,senses--,natural ,history--,natural ,philosophy--,matter--,objects--,propert ies of ,matter #a ,,chapter ,,ii4--,,open-,,air ,,science4 ,science in the ,open ,air--,aphides--,evaporation by ,leaves--,an ,aquarium--,the ,cataleptic ,fowl--,needle ,points and ,thorns--,microscopic ,aquarium--,cape ,grisnez--,crystals--,ice on the ,gas ,lamps #f ,,chapter ,,iii4--,,physics4 ,physics--,the ,meaning of ,physics--,forces of ,nature--,gravity--,cohesion--,chemical ,attraction--,centre of ,gravity--,experiments--,automaton ,tumblers #bb ,,chapter ,,iv4--,,physics 7,continued74 ,some ,properties of ,solid ,bodies--,inertia--,motion--,friction--, the ,pendulum--,equilibrium #ce ,,chapter ,v4--,,gases4 ,gases and ,liquids--,pressure of the ,air--,experiments #dd ,,chapter ,,vi4--,,water4 ,about ,water--,hydrostatics and ,hydraulics--,law of ,archimedes--,the ,bramah ,press--,the ,syphon #ei ,,chapter ,,vii4--,,heat4 ,heat--,what it is--,theory of ,heat--,the ,thermometer--,expansion by ,heat--,ebullition and ,distillation #gb ,,chapter ,,viii4--,,heat 7,continued74 ,specific ,heat--,fusion--,latent ,heat--,conduction and ,convection of ,heat--,calorescence #hh ,,chapter ,,ix4--,,light4 ,light and its ,sources--,what is ,light8--,velocity of ,light--,reflection and ,refraction--,relative ,value of ,lights #ic ,,chapter ,x4--,,light 7,continued74 ,vision and ,optical ,illusions--,the ,eye ,described--,accommodation of the ,eye--,chromatic ,aberration--,spinning ,tops #ajb ,,chapter ,,xi4--,,optics4 ,optical ,illusions--,zollner's ,designs--,the ,thaumatrope--,phenokistoscope--,the ,zootrope--,the ,praxinoscope--,the ,dazzling ,top #aaf ,,chapter ,,xii4--,,optics 7,continued74 ,optical ,illusions ,continued--,experiments--,the ,talking ,head--,ghost ,illusions #abi ,,chapter ,,xiii4--,,optics 7,continued74 ,vision--,the ,eye--,the ,stereoscope--,spectrum ,analysis--,the ,spectroscope--,the ,telescope and ,microscope--,photography--,dissolving ,views--,luminous ,paint #adj ,,chapter ,,xiv4--,,spectral ,,illusions4 ,a ,spectre ,visible--,curious ,illusions--,ghosts #afa ,,chapter ,,xv4--,,acoustics4 ,the ,ear and ,hearing--,physiology of ,hearing and ,sound--,sound as ,compared with ,light--,what is ,sound8--,velocity of ,sound--,conductibility--,the ,harmonograph #aff ,,chapter ,,xvi4--,,acoustics 7,continued74 ,the ,topophone--,the ,megaphone--,the ,autophone--,the ,audiphone--,the ,telephone--,the ,phonograph--,the ,microphone #ahj ,,chapter ,,xvii4--,,acoustics 7,continued74 ,the ,tuning-,fork--,the ,syren--,sound ,figures--,singing ,flames #aic ,,chapter ,,xviii4--,,electricity4 ,derivation of ,electricity--,sealing ,wax ,experiment--,the ,electrophorus--,leyden ,jar--,positive and ,negative--,the ,electroscope--,electric ,machines #aig ,,chapter ,,xix4 ,velocity of ,electricity--,experiments--,the ,electric ,egg--,force of the ,electric ,spark #bab ,,chapter ,,xx4--,,galvanism4 ,galvani's ,discovery--,the ,frogs ,electrified--,experiments--,volta's ,pile--,the ,test--,its ,usefulness--,faraday's 8,researches40 #bag ,,chapter ,,xxi4--,,magnetism4 ,the ,loadstone--,magnetic ,curves--,the ,magnetic ,needle--,the ,mariner's ,compass--,magneto-,electricity #bed ,,chapter ,,xxii4--,,applied ,,electricity4 ,sundry ,electrical ,appliances--,mr4 ,edison's ,inventions--,the ,electric ,light--,the ,gyroscope--,a ,new ,electrophorus--,electric ,toys #bfb ,,chapter ,,xxiii4--,,aeronautics4 ,pressure of ,air in ,bodies--,early ,attempts to fly in the ,air--,discovery of ,hydrogen--,the ,montgolfier ,balloons--,first ,experiments in ,paris--,noted ,ascents #bic ,,chapter ,,xxiv4--,,chemistry4 ,what ,chemistry is--,the ,elements--,metallic and ,non-,metallic--,atomic ,weight--,acids--,alkalis--,bases--,salt s--,chemical ,combination and ,study #cjg ,,chapter ,,xxv4--,,chemistry 7,continued74 ,chemistry without a ,laboratory #cac ,,chapter ,,xxvi4--,,chemistry 7,continued74 ,chemistry and ,alchemy--,chemical ,combinations--,the ,atmospheric ,air #ccf ,,chapter ,,xxvii4--,,the ,,elements4 ,non-,metallic ,elements #cdh ,,chapter ,,xxviii4--,,non-,,metallic ,,elements 7,continued74 ,chlorine--,bromine--,iodine--,fluorine- -,carbon--,sulphur--,phosphorus--,silico n-- ,boron--,tellurium--,arsenic #cff ,,chapter ,,xxix4--,,the ,,metals4 ,what ,metals are--,characteristics and ,general ,properties of ,metals--,classification--,specific ,gravity--,descriptions #chf ,,chapter ,,xxx4--,,organic ,,chemistry4 ,radicals--,acids--,bases--,neutrals #daj ,,chapter ,,xxxi4--,,mineralogy ,,and ,,crystallography4 ,the ,minerals--,characteristics--,crystals and their ,forms--,descriptions of ,minerals #dbd ,,chapter ,,xxxii4--,,new ,,locomotive ,,appliances4 ,the ,kite--,the ,aerophane--,ice ,yachts--,sailing ,trucks--,water ,velocipedes #ddh ,,chapter ,,xxxiii4--,,astronomy4 ,introductory--,history of ,astronomy--,nomenclature #dff ,,chapter ,,xxxiv4--,,angles ,,and ,,measurement ,,of ,,angles4 ,the ,quadrant--,transit ,instrument--,clocks--,stellar ,time--,solar ,time--8,mean ,time0 #dgd ,,chapter ,,xxxv4--,,the ,,solar ,,system4 ,gravitation--,the ,planets--,size and ,measurement of the ,planets--,satellites--,falling ,stars--,comets--,aerolites #dhf ,,chapter ,,xxxvi4--,,the ,,sun4 ,motion of the ,sun--,the ,seasons--,character of the ,sun--,sun-,spots--,zodiacal ,light #dif ,,chapter ,,xxxvii4--,,the ,,earth4 ,form of the ,earth--,motion of the ,globe--,rate and ,manner of ,progression--,latitude and ,longitude--,the ,seasons #ejd ,,chapter ,,xxxviii4--,,the ,,moon4 ,what is it ,like8--,moon ,superstitions--,description of the ,moon--,phases--,tides--,eclipses #eaj ,,chapter ,,xxxix4--,,the ,,stars4 ,the ,planets and ,asteroids #eba ,,chapter ,,xl4--,,the ,,fixed ,,stars4 ,fixed-,stars--,magnitude of the ,stars--,constellations--,descriptions of the ,zodiacal ,constellations--,northern and ,southern ,star ,groups--,distance of ,stars #ece ,,chapter ,,xli4--,,the ,,stars 7,continued74 ,double and ,multiple ,stars--,coloured and ,variable ,stars--,clusters1 ,groups1 and ,nebul--,the ,galaxy1 or ,milky ,way--,how to ,find out the ,principal ,stars #edf ,,chapter ,,xlii4--,,new ,,astronomical ,,appliances4 ,a ,celestial ,indicator--,astronomical or ,cosmographical ,clock--,a ,simple ,globe--,a ,solar ,chronometer #eeg ,,chapter ,,xliii4--,,physical ,,geography ,,and ,,geology4 ,geography and ,geology--,the ,earth's ,crust--,origin of the ,earth--,denudation and ,excavation by ,water--,rocks1 ,gravel1 and ,sand--,classes of ,rocks #efd ,,chapter ,,xliv4--,,geology4 ,crust of the ,earth--,geological ,systems--,eozoic1 ,primary1 ,secondary1 ,tertiary1 ,pre-,historic ,formations #egc ,,chapter ,,xlv4--,,geology 7,continued74 ,the ,mesozoic ,system--,the ,triassic1 ,oolitic1 and ,cretaceous ,formations--,the ,eocene1 ,miocene1 and ,pliocene--,the ,glacial ,period--,pre-,historic ,man #ehd ,,chapter ,,xlvi4--,,physical ,,geography4 ,igneous ,rocks--,land and ,water--,springs1 ,wells1 and ,geysers--,snow and ,ice--,their ,effects #fja ,,chapter ,,xlvii4--,,the ,,sea ,,and ,,the ,,sky4 ,the ,sea--,salt ,water--,waves and their ,effects--,under ,water--,the ,floor of the ,ocean #faj ,,chapter ,,xlviii4--,,physical ,,geography4 ,,meteorology4 ,the ,atmosphere--,winds and ,air ,currents--,wind ,pressure--,storms--,rain-clouds-- ,water-,spouts--,atmospherical ,phenomena #fbh ,,chapter ,,xlix4--,,physical ,,geography4 ,,meteorology 7,continued74 ,atmospheric ,phenomena--,thunder and ,lightning--,aurora ,borealis--,the ,rainbow--,mock-,suns and ,mock-,moons--,halos--,fata ,morgana--,reflection and ,refraction--,mirage--,spectre of the ,brocken #fdb ,,chapter ,l4--,,physical ,,geography4 ,,climatology4 ,weather2 ,climate1 and ,temperature--,isothermal ,lines--,isobars1 ,weather ,forecasts1 and ,signs of the ,sky #fea ,,chapter ,,li4--,,biology4 ,,part ,i43 ,,botany4 ,plants and ,animals--,structure of ,plants--,flowering ,plants--,the ,stem--,the ,leaves--,forms of ,leaves #feh ,,chapter ,,lii4--,,flowering ,,plants4 ,organs of ,increase and ,reproduction--,the ,flower--,the ,calyx--,the ,corolla--,the ,stamen--,the ,pistil #fge ,,chapter ,,liii4--,,flowering ,,plants 7,continued74 ,the ,floral ,axis--,inflorescence--,fruit--,seed--,n utrition of ,plants--,absorbtion of ,constituents #fgi ,,chapter ,,liv4--,,zoology4 ,classification of ,animals--,vertebrates and ,invertebrates--,protozoa--,hydrozoa--,a ctinozoa #gjj ,,chapter ,,lv4--,,echinodermata--,,annulosa--,,en tozoa--,,insecta4 ,sea-,urchins--,star-,fishes--,feathery ,stars--,sea-,cucumbers--,worms--,leeche s-- ,rotifers--,tape ,worms--,insects #gab ,,chapter ,,lvi4--,,the ,,analysis ,,of ,,chance ,,and ,,mathematical ,,games4 ,magic ,squares--,the ,sixteen ,puzzle--,solitaire--,equivalents #gbf ,,chapter ,,lvii4--,,games 7,continued74 ,the ,magic ,top--,the ,gyroscope and ,scientific ,games #gdj ,,chapter ,,lviii4--,,science ,,at ,,home4 ,scientific ,objects for the ,household #gdg ,,chapter ,,lix4--,,domestic ,,science4 ,science and ,domestic ,economy #geg ,,chapter ,,lx4--,,curious ,,inventions4 ,some ,curious ,modes of ,transit #ggj ,,scientific ,,recreations4 ,,chapter ,i4--,,introductory4 ,,science ,,and ,,recreation--,,the ,,book ,,of ,,nature--,,the ,,senses--,,natural ,,history--,,natural ,,philosophy--,,matter--,,objects--,,pro perties ,,of ,,matter4 ,it may at the first glance appear paradoxical to combine ,science and ,recreation1 but we hope to show that true scientific recreation is anything but the dry bones of learning4 ,to those who study science with us1 we will point out first how easy and pleasant it is to watch the sky and the plants and ,nature generally in the open air4 ,then we will carry our readers along with us1 and by means of illustrations and diagrams instruct them pleasantly in the reasons for things4 8,how80 and 8,why80 will be questions fully answered4 ,not only will the usual scientific courses be touched upon1 but we will show how ,science is applied to ,domestic ,economy4 ,we will have ,chemistry put before us without needing a laboratory1 and we will experiment in ,physics without elaborate apparatus4 ,we will have1 in short1 a complete ,encyclopdia of ,science free from dryness and technicalities--an amusing volume suited to old and young who wish to find out what is going on around them in their daily life in earth and sea and sky4 ,bernard ,palissy used to say that he wished 8no other book than the earth and the sky10 and that 8it was given to all to read this wonderful book40 ,it is indeed by the study of the material world that discoveries are accomplished4 ,let an attentive observer watch a ray of light passing from the air into water1 and he will see it deviate from the straight line by refraction2 let him seek the origin of a sound1 and he will discover that it results from a shock or a vibration4 ,this is physical science in its infancy4 ,it is said that ,newton was led to discover the laws of universal gravitation by beholding an apple fall to the ground1 and that ,montgolfier first dreamt of air-balloons while watching fogs floating in the atmosphere4 ,the idea of the inner chamber of the eye may1 in like manner1 be developed in the mind of any observer1 who1 seated beneath the shade of a tree1 looks fixedly at the round form of the sun through the openings in the leaves4 ,illustration3 ,luminous ,cross seen at ,havre1 ,may #gth1 #ahgg4 ,sketched from ,nature4 ,every one1 of course1 may not possess the ambition to make such discoveries1 but there is no one who cannot compel himself to learn to enjoy the pleasure that can be derived from the observation of ,nature4 ,it must not be imagined that in order to cultivate science it is absolutely necessary to have laboratories and scientific work-rooms4 ,the book of which ,palissy spoke is ever present2 its pages are always open1 wherever we turn our eyes or direct our steps4 ,so we may hope to introduce all our friends to a pleasant and lasting acquaintance with ,dame ,nature4 8,but what is ,nature80 ,we are fond of admiring ,nature1 and the effects of certain causes in the world1 and we want to know why things are so4 ,very well--so you shall2 and as to the question 8,what is ,nature80 we will endeavour to answer you at once4 ,nature is the united totality of all that the various ,senses can perceive4 ,in fact1 all that cannot be made by man is termed 8,nature02 i4e41 ,god's creation4 ,from the earliest ages man has sought to read the open leaves of the ,book of ,nature1 and even now1 with all our attainments1 we cannot grasp all1 or nearly all4 ,one discovery only leads up to another4 ,cause and ,effect are followed up step by step till we lose ourselves in the search4 ,every effect must have a cause4 ,one thing depends upon another in the world1 and it does not need ,divine revelation to tell us that4 ,nothing happens by 8mere chance40 8,chance60 said a ,professor to us at the ,university1 8,chance6--,remember1 there is no such thing in the world as chance40 ,between our minds or consciousness and ,nature are our ,senses4 ,we feel1 we see1 we hear1 we taste1 we smell1--so it is only through the ,senses that we can come to any knowledge of the outer world4 ,these attributes1 or ,senses1 act directly upon a certain 8primary faculty0 called ,consciousness1 and thus we are enabled to understand what is going on around us4 ,the more this great existing faculty is educated and trained1 the more useful it will become4 ,so if we accustom our minds to observation of ,nature1 we shall find out certain causes and effects1 and discover ,objects4 ,now an ,object is a thing perceptible both to feeling and sight1 and an ,object occupies space4 ,therefore there are objects ,artificial as well as ,natural4 ,the former are created by man from one or more ,natural products4 ,natural ,objects are those such as trees1 rocks1 plants1 and animals4 ,we may also class the heavenly bodies1 etc41 as ,objects1 though we cannot touch them1 but we can feel their effects1 and see them4 ,the ,,phenomena of ,nature include those results which are perceptible by only one sense1 as thunder2 light and sound may also be classed as ,phenomena4 ,take a familiar instance4 ,a stone is a ,natural ,object4 ,we take it up1 open our fingers1 and it falls4 ,the motion of that object is a ,phenomenon4 ,we know it falls because we see it fall1 and it possesses what we term weight2 but we cannot tell why it possesses weight4 ,professor ,huxley says3 8,stones do not fall to the ground in consequence of a law of nature10 for a law is not a cause4 8,a law of nature merely tells us what we may expect natural objects will do under certain circumstances40 ,a cause of a ,phenomenon being independent of human will is called a ,force1 and the stone falls by the force of ,gravitation1 or that natural law which compels every material object to approach every other material object4 ,a single ,force may produce a great number of ,phenomena4 ,nature being revealed to us by ,objects1 and by means of ,phenomena1 we have got already two ,branches of ,science extending from such ,roots2 viz41 ,,natural ,,history1 the ,science of ,objects2 and ,,natural ,,philosophy1 the ,science of ,phenomena4 ,both of these ,branches have been subdivided thus3 ,zoology1 referring to ,animals ,biology4 ,natural ,history ,botany1 referring to ,plants ,mineralogy referring to ,minerals1 etc4 ,geology ,physics4 ,phenomena without essential change ,natural ,philosophy of the ,objects4 ,chemistry4 ,phenomena with change of the ,objects4 ,physiology4 ,phenomena of animated ,objects4 ,these two great divisions comprehend1 in their extended senses1 all that is known respecting the material world4 ,we have spoken of ,objects4 ,objects occupy ,space4 ,what is ,space8 ,space is magnitude which can be conceived as extending in three directions--,length1 ,breadth1 and ,depth4 ,,matter occupies portions of ,space1 which is infinite4 ,matter1 when finite1 is termed a body or object4 ,the general properties of ,matter are ,magnitude1 ,form1 ,impenetrability1 ,inertia1 ,divisibility1 ,porosity1 ,elasticity1 ,compressibility1 ,expansibility4 ,matter is present in ,nature in three conditions4 ,we find it as a ,,solid1 a ,,liquid1 and a ,,gas4 ,we shall explain the various properties of ,solids1 ,liquids1 and ,gases in their proper places 7in ,physics74 ,to test the actual existence of ,matter in one or other of these forms our ,senses help us4 ,we can touch a ,solid1 or taste it and see it4 ,but touch is the test4 ,we have said that ,matter possesses certain properties4 ,we will examine these briefly4 ,the two which belong to all material bodies are ,impenetrability and ,magnitude4 ,you cannot1 strictly speaking1 penetrate ,matter4 ,you can find the form of an object by touch or sight1 but you cannot penetrate it4 ,you will think you can drive a nail or a screw into a board1 but you cannot2 you only displace the fibres of the wood by the screw4 ,take water as a very common instance4 ,water is ,matter1 for it occupies a certain space4 ,water is impenetrable1 for if you put your hand or foot into a basin full of it1 it will overflow1 thus proving that you displace1 and do not penetrate it4 ,it is almost impossible to compress water4 ,divisibility is another quality of ,matter2 and when we attempt to show how far ,matter can be divided1 the brain refuses to grasp the infinity4 ,a pin's head is a small object1 but it is gigantic compared to some animals1 of which millions would occupy a space no larger than the head of a pin4 ,these tiny animals must contain organs and veins1 etc41 and those veins are full of blood globules4 ,professor ,tyndall informs us that a drop of blood contains three millions of red globules4 ,so these infinitesimally small animals must have millions of globules in their blood also4 ,thus we see to what an extent1 far beyond our ,senses' power to grasp1 ,matter can be divided4 ,but there is something even more astonishing than this4 ,it is stated that there are more animals in the milt of a single codfish than there are men in the world2 and that one grain of sand is larger than four millions of these animals6 each of which must be possessed of life germs of an equal amount1 which would grow up as it grew to maturity4 ,this carries us back again1 and 8,imagination's utmost stretch ,in wonder dies away40 ,or take other interesting facts4 ,one hundred threads of the silkworm must be placed side by side to make up the thickness of a line 7--7 about #a_/beth of an inch2 and metals can be drawn out to such exceeding fineness that twelve hundred of the fine wires will occupy only the space of one hundred silkworms' threads1 or one millimetre4 ,porosity is another attribute of ,matter1 for in all ,matter there are pores1 or spaces1 between the particles4 ,sometimes such openings are plainly visible2 in very 8solid0 bodies they are1 to a great extent1 indistinguishable4 ,but we know that the spaces exist1 because we can compress the particles together4 ,inertia is also a general property of ,matter1 and the meaning of the term is 8inactivity10 or passiveness--a want of power in an object to move1 or when moving1 to stop of itself4 ,it will come to rest apparently by itself1 but the resistance of the air and the friction of the ground1 or the attraction of the earth1 will really occasion the stoppage of the object4 ,we will speak more fully of ,inertia presently4 ,elasticity and ,expansibility are evident in fluids and gases4 ,we have thus introduced our readers to some of the most evident facts connected with ,matter4 ,the various ,forces and ,phenomena of attraction will be fully considered farther on2 at present we are about to show our readers how they may first profitably study ,science in the open air for themselves1 and we will give them our experience of the ,book of ,nature4 ,,chapter ,,ii4 ,,science ,,in ,,the ,,open ,,air--,,aphides--,,evaporation ,,by ,,leaves--,,an ,,aquarium--,,the ,,cataleptic ,,fowl--,,needle ,,points ,,and ,,thorns--,,microscopic ,,aquarium--,,cape ,,grisnez--,,crystals--,,ice ,,on ,,the ,,gas ,,lamps4 ,illustration3 ,fig4 #a4--;,ants engaged in extracting aphides from a rose-tree 7highly magnified7 ,some years ago we were staying in ,normandy1 not far from the town of ,c----1 enjoying1 in the midst of most cordial hospitality1 the peacefulness of country life2 and my kind hosts1 with me1 took great pleasure in having what we called 8a course of science in the open air40 ,the recollections of that time are some of the pleasantest in the whole course of my life1 because all our leisure was intelligently occupied4 ,each of us set himself to provide the subject of some curious observation or instructive experiment2 one made a collection of insects1 another studied botany4 ,in the daytime we might have been seen examining1 under a magnifying glass1 the branch of a rose-tree1 from which the ants were endeavouring to extract the aphides#a 7fig4 #a74 ,at night we admired through the telescope the stars and planets that were visible2 or if the sky was not clear1 we examined under a strong magnifier grains of pollen from flowers1 or the infusoria in a drop of stagnant water4 ,frequently some very insignificant object became the occasion for some scientific discussion1 which terminated with an experimental verification4 ,i recollect that one day one of us remarked that after a week of dry weather a stream of water had nearly dried up1 although sheltered by thick trees1 which necessarily impeded the calorific action of the sun2 and he expressed surprise at the rapid evaporation4 ,an agriculturist among the company1 however1 drew his attention to the fact that the roots of the trees were buried in the course of the stream1 and that1 far from preventing the evaporation of the water1 the leaves had contributed to accelerate it4 ,as the first speaker was not convinced1 the agriculturist1 on our return to the house1 prepared an experiment represented in fig4 #b4 ,he placed the branch of a tree covered with foliage in a ,u-shaped tube1 the two branches of unequal diameter1 and filled with water4 ,he placed the vegetable stem in the water1 and secured it to the tube by means of a cork covered with a piece of india-rubber1 and tied tightly to make it hermetically closed4 ,illustration3 ,fig4 #b4--;,experiment showing evaporation of water by leaves4 ,at the commencement of the experiment the water was level with ,a in the larger branch of the tube1 and level with ,b in the smaller1 rising by capillarity to a higher point in the more slender of the two4 ,the evaporation of the water caused by the leaves was so active that in a very short time we beheld the water sink to the points ,c and ,c4 ,illustration3 ,fig4 #c4--;,aquarium formed by means of a melon glass4 ,thus did the excellent method of seeking the cause of phenomena by experiments often lead us to interesting results4 ,we had among us many children and young people who had reached the age of ardent curiosity4 ,we took pleasure in pointing out to them the means of studying natural science2 and we were not long before feeling convinced that our lessons out in the fields had much greater success than those given between the four walls of a class-room4 ,insects were collected1 and preserved by being carefully placed in a small bottle1 into which was let fall a drop of sulphuret of carbon2#b the insect was immediately asphyxiated1 and we thus avoided the cruelty of passing a pin through a living body4 ,having chased butterflies and insects1 we next desired to study the aquatic creatures which swarmed in the pools of the neighbourhood4 ,for this purpose ,i constructed a fishing-net fitted to an iron ring1 and firmly secured to a wooden handle4 ,when this was plunged under the water and drawn quickly out again1 it came back full of slime4 ,in the midst of this muddy substance one generally succeeded in finding the hydrophilus1 tadpoles1 coleoptera1 many curious kinds of caddis-worms1 tritons1 and sometimes frogs1 completely astounded by the rapidity of their capture4 ,all these creatures were transported in a bottle to the house1 and ,i then constructed1 at small expense1 a glass aquarium1 by means of the bell of a melon-glass turned upside down1 thus forming a transparent receptacle of considerable size4 ,four wooden stakes were then fixed in the ground1 and a plank with a circular hole nailed on the top1 in which the glass bell was placed4 ,i next scattered some large pebbles and shells at the bottom of the vase to form a stony bed1 poured in some water1 placed a few reeds and water plants among the pebbles1 and then threw a handful of water lentils on the surface2 thus a comfortable home was contrived for all the captured animals4#c ,the aquarium1 when placed under the shade of a fine tree in a rustic spot abounding with field flowers1 became a favourite rendezvous1 and we often took pleasure in watching the antics of the little inmates 7fig4 #c74 ,sometimes we beheld very sanguinary scenes2 the voracious hydrophilus would seize a poor defenceless tadpole1 and rend him in pieces for a meal without any compunction4 ,the more robust tritons defended themselves better1 but sometimes they also succumbed in the struggle4 ,illustration3 ,fig4 #d4--;,cage for preserving living insects4 ,illustration3 ,fig4 #e4--,small aquarium1 with frogs' ladder4 ,the success of the aquarium was so complete that one of us resolved to continue this museum in miniature1 and one day provided himself with an insects palace1 which nearly made us forget the tadpoles and tritons4 ,it was a charming little cage1 having the form of a house1 covered with a roof2 wires placed at equal distances forming the sides4 ,in it was a large cricket beside a leaf of lettuce1 which served as his food 7fig4 #d74 ,the little creature moved up and down his prison1 which was suspended from the branch of a tree1 and when one approached him very closely gave vent to his lively chirps4 ,illustration3 ,fig4 #f4--;,frog lying in wait for a fly4 ,the menagerie was soon further augmented by a hitherto unthought-of object2 namely1 a frogs' ladder4 ,it was made with much skill4 ,a large bottle served for the base of the structure4 ,the ladder which was fixed in it was composed of the twigs of very small branches1 recently cut from a tree1 and undivested of their bark1 which gave to the little edifice a more picturesque and rustic appearance4 ,the pieces of wood1 cleverly fixed into two posts1 conducted the green frogs 7tree-frogs7 on to a platform1 whence they ascended the steps of a genuine ladder4 ,there they could disport themselves at pleasure1 or climb up further to a branch of birch-tree placed upright in the centre of the bottle 7fig4 #e74 ,a net with fine meshes prevented the little animals from escaping4 ,we gave the tree-frogs flies for their food1 and sometimes they caught them with remarkable dexterity4 ,i have often seen a frog when at liberty watching a fly1 on which it pounces as a cat does on a bird 7fig4 #f74 ,the observations that we made on the animals of our menagerie led us to undertake others of a very different nature2 ,i recollect particularly a case of catalepsy produced in a cock4 ,i will describe this remarkable experiment1 certainly one of the most curious we ever performed4 ,illustration3 ,fig4 #g4--;,experiment of the cataleptic cock4 ,we place a cock on a table of dark colour1 rest its beak on the surface1 where it is firmly held1 and with a piece of chalk slowly draw a white line in continuation from the beak1 as shown in our engraving4 ,if the crest is thick1 it is necessary to draw it back1 so that the animal may follow with his eyes the tracing of the line4 ,when the line has reached a length of about two feet the cock has become cataleptic4 ,he is absolutely motionless1 his eyes are fixed1 and he will remain from thirty to sixty seconds in the same posture in which he had at first only been held by force4 ,his head remains resting on the table in the position shown in fig4 #g4 ,this experiment1 which we have successfully performed on different animals1 can also be accomplished by drawing a straight line with a piece of chalk on a slate4 ,m4 ,azam declares that the same result is also produced by drawing a black line on a table of white wood4 ,according to ,m4 ,balbiani1 ,german students had formerly a great predilection for this experiment1 which they always performed with marked success4 ,hens do not1 when operated on1 fall into a cataleptic condition so easily as cocks2 but they may often be rendered motionless by holding their heads fixed in the same position for several minutes4 ,the facts we have just cited come properly under the little studied phenomena1 designated by ,m4 ,braid in #ahdc by the title of ,hypnotism4 ,,mm4 ,littr and ,ch4 ,robin have given a description of the hypnotic condition in their ,dictionnaire de ,mdecine4 ,illustration3 ,fig4 #h4--,ordinary pin and needle1 seen through a microscope 7magnified #ejj diameters74 ,illustration3 ,fig4 #i4--,thorn of a rose1 and wasp's sting through a microscope 7magnified #ejj diameters74 ,if any shining object1 such as a lancet1 or a disc of silver-paper gummed to a plate1 is placed at about the distance of a foot from the eyes of a person1 slightly above the head1 and the patient regards this object fixedly1 and without interruption for twenty or thirty minutes1 he will become gradually motionless1 and in a great number of cases will fall into a condition of torpor and genuine sleep4 ,dr4 ,braid affirms that under such circumstances he has been able to perform surgical operations1 without the patient having any consciousness of pain4 ,later also1 ,m4 ,azam has proved the complete insensibility to pricking on the part of individuals whom he has rendered cataleptic by the fixing of a brilliant object4 ,the experiment of the cataleptic cock was first described under the name of ,experimentum ,mirabile1 by ,p4 ,kircher1 in his ,ars ,magna1 published at ,rome in #afdf4 ,it evidently belongs to the class of experiments which were performed at the ,salptrire asylum at ,paris1 by ,m4 ,charcot1 on patients suffering from special disorders4 ,it must now be evident to our readers that our scientific occupations were sufficiently varied1 and that we easily found around us many objects of study4 ,when the weather was wet and cloudy we remained indoors1 and devoted ourselves to microscopical examinations4 ,everything that came under our hands1 insects1 vegetables1 etc41 were worthy of observation4 ,one day1 while engaged over a microscopical preparation1 ,i was making use of one of those steel points generally employed in such purposes1 when happening to pass it accidentally beneath the microscope1 ,i was astonished to see how rough and uneven it appeared when highly magnified4 ,the idea then occurred to me to have recourse to something still more pointed1 and ,i was thus led to make comparisons between the different objects represented in figs4 #h and #i4 ,it will here be seen how very coarse is the product of our industry when compared with the product of ,nature4 ,no4 #a of fig4 #h represents the point of a pin that has already been used1 magnified #ejj diameters4 ,the point is evidently slightly blunted and flattened4 ,the malleable metal has yielded a little under the pressure necessary to make it pass through a material4 ,no4 #b is a little more pointed2 it is a needle4 ,this1 too1 will be seen to be defective when regarded by the aid of the microscope4 ,on the other hand1 what fineness and delicacy do the rose thorn and wasp's sting present when examined under the same magnifier6 7,see the two points in fig4 #i47 ,an examination of this exact drawing has led me to make a calculation which leads to rather curious results3 at a half millimetre from the point1 the diameters of the four objects represented are in thousandths of a millimetre respectively1 #cd2 #bb2 #aa2 #jch4 ,the corresponding sections in millionths of a square millimetre are3 #ijgib2 #chjac2 #iejc2 #aacd2 or1 in round numbers1 #ijh2 #chj2 #ie2 #aa4 ,if one bears in mind1 which is much below the truth1 that the pressure exercised on the point must be proportional to the section1 and admitting that a pressure of #aa centigrams suffices to thrust in the sting of a wasp half a millimetre1 it will require more than #i grams of pressure to thrust in a needle to the same extent4 ,in fact1 this latter figure is much too small1 for we have not taken into account the advantage resulting from the elongated shape of the rose thorn1 which renders it more favourable for penetration than a needle through a drop of tallow4 ,it would be easy to extend observations of this kind to a number of other objects1 and the remarks ,i have just made on natural and artificial points will apply incontestably to textures for example4 ,there is no doubt that the thread of a spider's web would far surpass the thread of the finest lace1 and that art will always find itself completely distanced by nature4 ,we amused ourselves frequently by examining the infusoria which are so easily procured by taking from some stagnant water the mucilage adhering to the vegetation on the banks1 or attached to the lower part of water lentils4 ,in this way we easily captured infusoria1 which1 when placed under a strong magnifier1 presented the most remarkable spectacle that one can imagine4 ,they are animalcules1 having the form of transparent tulips attached to a long stem4 ,they form bunches which expand and lengthen2 then1 suddenly1 they are seen to contract with such considerable rapidity that the eye can scarcely follow the movement1 and all the stems and flower-bells are folded up into the form of a ball4 ,then1 in another moment1 the stems lengthen1 and the tulip-bells open once more4 ,one can easily encourage the production of infusoria by constructing a small microscopic aquarium1 in which one arranges the centre in a manner favourable to the development of the lowest organisms4 ,it suffices to put a few leaves 7a piece of parsley answers the purpose perfectly7#d in a small vase containing water 7fig4 #aj71 over which a glass cover is placed1 and it is then exposed to the rays of the sun4 ,in two or three days' time1 a drop of this water seen under the microscope will exhibit infusoria4 ,after a certain time1 too1 the different species will begin to show themselves4 ,microscopical observations can be made on a number of different objects4 ,expose to the air some flour moistened by water1 and before long a mouldiness will form on it2 it is the penicillium glaucum1 and when examined under a magnifier of #bjj to #cjj diameters1 cells are distinguishable1 branching out from an organism remarkable for its simplicity4 ,we often amused ourselves by examining1 almost at hazard1 everything that came within our reach1 and sometimes we were led to make very instructive investigations4 ,when the sky was clear1 and the weather favourable to walking1 we encouraged our young people to run about in the fields and chase butterflies4 ,the capture of butterflies is accomplished1 as every one knows1 by means of a gauze net1 with which we provided the children1 and the operation of chasing afforded them some very salutary exercise4 ,it sometimes happens that butterflies abound in such numbers1 that it is comparatively easy to capture them4 ,during the month of ,june #ahgi1 a large part of ,western ,europe was thronged with swarms of ,vanessa algina butterflies1 in such numbers that their appearance was regarded as an important event1 and attracted the lively attention of all entomologists 7fig4 #aa74 ,this passage of butterflies provided the occasion for many interesting studies on the part of naturalists4 ,illustration3 ,fig4 #aj4--;,arrangement of a microscopic aquarium for examining infusoria4 ,illustration3 ,fig4 #aa4--;,flight of butterflies seen near ,berne1 ,june #aeth1 #ahgi4 ,illustration3 ,fig4 #ab4--;,group of rock crystal4 ,we cannot point out too strongly to our readers that the essential condition for the student of natural science1 is the possession of that sacred fire which imparts the energy and perseverance necessary for acquiring and enlarging collections4 ,it is also necessary that the investigator should furnish himself with certain indispensable tools4 ,for collecting plants1 the botanist should be armed with a pickaxe set in a thoroughly strong handle1 a trowel1 of which there is a variety of shapes1 and a knife with a sharp blade4 ,a botanical case must also be included1 for carrying the plants4 ,the geologist1 or mineralogist1 needs no more elaborate instruments2 a hammer1 a chisel1 and a pickaxe with a sharp point for breaking the rocks1 and a bag for carrying the specimens1 will complete his outfit4 ,we amused ourselves by having these instruments made by the blacksmith1 sometimes even by manufacturing them ourselves2 they were simple1 but solid1 and admirably adapted to the requirements of research4 ,often we directed our walks to the seashore1 where we liked to collect shells on the sandy beach1 or fossils among the cliffs and rocks4 ,i recollect1 in a walk ,i had taken some years previously along the foot of the cliffs of ,cape ,blanc-,nez1 near ,calais1 having found an impression of an ammonite of remarkable size1 which has often excited the admiration of amateurs2 this ammonite measured no less than twelve inches in diameter4 ,the rocks of ,cape ,grisnez1 not far from ,boulogne1 also afford the geologian the opportunity of a number of curious investigations4 ,in the ,ardennes and the ,alps ,i have frequently procured some fine mineral specimens2 in the first locality crystallized pyrites1 in the second1 fine fragments of rock crystal 7fig4 #ab74 ,i did not fail to recount these successful expeditions to the young people who accompanied me1 and their ardour was thereby inflamed by the hope that they also should find something valuable4 ,it often happened when the sun was powerful1 and the air extremely calm1 that my young companions and ,i remarked some very beautiful effects of mirage on the beach1 due to the heating of the lower strata of the atmosphere4 ,the trees and houses appeared to be raised above a sheet of silver1 in which their reflections were visible as in a sheet of tranquil water4 ,it can hardly be believed how frequently the atmosphere affords interesting spectacles which pass unperceived before the eyes of those who know not how to observe4 ,i recollect having once beheld at ,jersey a magnificent phenomenon of this nature1 on the #bdth ,june1 #ahgg1 at eight o'clock in the evening3 it was a column of light which rose above the sinking sun like a sheaf of fire4 ,i was walking on the ,st4 ,helier pier1 where there were also many promenaders1 but there were not more than two or three who regarded with me this mighty spectacle4 ,columns and crosses of light are much more frequent than is commonly supposed1 but they often pass unperceived before indifferent spectators4 ,we will describe an example of this phenomenon observed at ,havre on the #gth ,may1 #ahgg4 ,the sun formed the centre of the cross1 which was of a yellow1 golden colour4 ,this cross had four branches4 ,the upper branch was much more brilliant than the others2 its height was about #ae4 ,the lower branch was smaller1 as seen in the sketch on page #b1 taken from nature by ,monsieur ,albert ,tissandier4 ,the two horizontal branches were at times scarcely visible1 and merged in a streak of reddish-yellow colour1 which covered a large part of the horizon4 ,a mass of cloud1 which the setting sun tinged with a deep violet colour1 formed the foreground of the picture4 ,the atmosphere over the sea was very foggy4 ,the phenomenon did not last more than a quarter of an hour1 but the conclusion of the spectacle was signalized by an interesting circumstance4 ,the two horizontal branches1 and the lower branch of the luminous cross1 completely disappeared1 whilst the upper branch remained alone for some minutes longer4 ,it had now the appearance of a vertical column rising from the sun1 like that which ,cassini studied on the #bast ,may1 #afgb1 and that which ,m4 ,renon#e and ,m4 ,a4 ,guillemin observed on the #abth ,july1 #ahgf4f ,vertical columns1 which1 it is well known1 are extremely rare phenomena1 may therefore indicate the existence of a luminous cross1 which certain atmospheric conditions have rendered but partially visible4 ,how often one sees along the roads little whirlwinds of dust raised by the wind accomplishing a rotatory movement1 thus producing the imitation of a waterspout6 ,how often halos encompass with a circle of fire the sun or the stars6 ,how often we see the rainbow develop its iridescent beauties in the midst of a body of air traversed by bright raindrops6 ,and there is not one of these great natural manifestations which may not give rise to instructive observations1 and become the object of study and research4 ,thus1 in walks and travels alike1 the study of ,science may always be exercised2 and this method of study and instruction in the open air contributes both to health of body and of mind4 ,as we consider the spectacles which ,nature spreads before us1--from the insect crawling on the blade of grass1 to the celestial bodies moving in the dome of the heavens1--we feel a vivifying and salutary influence awaken in the mind4 ,the habit of observation1 too1 may be everywhere exercised--even in towns1 where ,nature still asserts herself2 as1 for example1 in displays of meteorological phenomena4 ,we will give an example of such4 ,illustration3 ,fig4 #ac4--;,icicles on gas lamp4 ,the extraordinary abundance of snow which fell in ,paris for more than ten consecutive hours1 commencing on the afternoon of ,wednesday1 ,january #bbnd1 #ahhj1 will always be looked upon as memorable among the meteorological events of the city of ,paris4 ,it was stated that in the centre of ,paris1 the thickness of the snow that had fallen at different times exceeded fourteen inches4 ,the snow had been preceded by a fall of small transparent icicles1 of rather more than a millimetre in diameter1 some having crystalline facets4 ,they formed on the surface of the ground a very slippery glazed frost4 ,on the evening of the #bbnd ,january1 flakes of snow began to hover in the atmosphere like voluminous masses of wool4 ,the greater part of the gas-lamps were ornamented by frozen stalactites1 which continually attracted the attention of passers-by4 ,the formation of these stalactites1 of which we give a specimen 7fig4 #ac71 is easy of explanation4 ,the snow falling on the glass of the lamp became heated by the flame of gas1 melted1 and trickled down1 freezing anew into the shape of a stalactite below the lamp1 at a temperature of #j centigrade4 ,not only can meteorology be studied in towns1 but certain other branches of natural science--entomology1 for example4 ,we will quote what a young student in science1 ,m4 ,a4 ,dubois1 says on this very subject3 8,coleoptera10 he declares1 8are to be met with everywhere1 and ,i think it may be useful to notice this fact1 supporting it by examples4 ,i desire to prove that there are in the midst of our large towns spots that remain unexplored1 where some fine captures are to be made4 ,let us visit1 at certain times1 the approaches to the quays1 even at low tide1 and we shall be surprised to find there species which we have searched for far and near40 ,this opinion is confirmed by the enumeration of several interesting captures4 ,was not the great ,bacon right when he said1 8,for the keen observer1 nothing in ,nature is mute08 ,illustration3 ,the cliffs of ,cape ,grisnez4 ,,footnotes3 #a ,it is well known that ants1 by touching the skin of aphides1 extract therefrom a secretion of viscous matter1 which nourishes them4 ,they will frequently carry off the aphides to their habitations1 and keep them there2 thus one may say they keep a cow in their stable4 #b ,the preservation of insects1 and their preparation for collections1 necessitates some precaution4 ,entomologists are in the habit of spreading them out on a small board1 and arranging the legs and antenn by means of large pins4 ,the wings should be dried by placing them on strips of paper1 which preserves them4 ,these precautions are indispensable if it is wished that the insects in a collection should retain their distinctive characters4 ,worms and caterpillars can be raised in pots filled with earth1 if carefully covered over with muslin or wire gauze with very fine meshes4 ,the process of hatching may give rise to many interesting observations4 #c ,it frequently happens that in a small aquarium1 constructed after this fashion1 the animals escape4 ,this is avoided by covering the vase with a net4 #d ,the infusion of parsley has the advantage of not sensibly obscuring the water4 #e ,detailed accounts in ,vol4 lxxxiii41 pp4 #bdc and #bib of 8,la ,nature40 #f ,see 8,la ,nature10 #dth year1 #ahgf1 #bnd half-year1 p4 #afg4 ,m4 ,a4 ,guillemin mentions1 in connection with the phenomenon of ,july #abth1 #ahgf1 the presence of light masses of cloud of a greyish-blue colour1 similar to those perceived in the phenomena just described4 ,,chapter ,,iii4 ,,physics--,,the ,,meaning ,,of ,,physics--,,forces ,,of ,,nature--,,gravity--,,cohesion--,,chemi cal ,,attraction--,,centre ,,of ,,gravity--,,experiments--,,automaton ,,tumblers4 ,having now introduced our readers to ,science which they can find for themselves in the open air1 and the pursuit of which will both instruct and amuse1 we will proceed to investigate the ,branch of ,science called ,,physics4 ,,physics may be briefly described as the ,branch of ,natural ,science which treats of such phenomena as are unaccompanied by any important changes in the objects wherein such phenomena are observed4 ,for instance1 the sounding of a bell or the falling of a stone are physical phenomena1 for the objects which cause the sound1 or the fall1 undergo no change4 ,heat is set free when coal burns4 ,this disengagement of heat is a physical phenomenon2 but the change during combustion which coal undergoes is a chemical phenomenon4 ,so the objects may be the same1 but the circumstances in which they are placed1 and the forces which act upon them1 may change their appearance or position4 ,this brings us at once to the ,forces of ,nature1 which are three in number2 viz41 ,gravity1 ,cohesion1 and ,affinity1 or ,chemical ,attraction4 ,the phenomena connected with the last-named forms the ,science of ,chemistry4 ,we give these three ,forces these names4 ,but first we must see what is ,force1 for this is very important4 ,force is a ,,cause--the cause of ,motion or of ,rest4 ,this may appear paradoxical1 but a little reflection will prove it4 ,it requires force to set any object in motion1 and this body would never stop unless some other force or forces prevented its movement beyond a certain point4 ,force is therefore the cause of a change of 8state0 in matter4 ,we have said there are three forces in nature4 ,the first is ,gravity1 or the attraction of particles at a distance from each other4 ,we may say that ,gravity1 or ,gravitation1 is the mutual attraction between different portions of matter acting at all distances1--the force of attraction being1 of course1 in proportion to the mass of the bodies respectively4 ,the greatest body is the ,earth1 so far as our purposes are concerned4 ,so the attraction of the ,earth is ,gravity1 or what we call ,weight4 ,we can easily prove this4 ,we know if we jump from a chair we shall come to the floor2 and if there were nothing between us and the actual ground sufficient to sustain the force of the attracting power of the earth1 we should fall to the earth's surface4 ,in a teacup the spoon will attract air bubbles1 and large air bubbles will attract small ones1 till we find a small mass of bubbles formed in the centre of the cup of tea4 ,divide this bubble1 and the component parts will rush to the sides of the cup4 ,this form of attraction is illustrated by the accompanying diagrams4 ,illustration3 ,fig4 #ad4 ,suppose two balls of equal magnitude1 ,a and ,b 7fig4 #ad74 ,these being of equal magnitude1 attract each other with equal force1 and will meet1 if not opposed1 at a point 7,m7 half-way between the two4 ,but they do not meet1 because the attraction of the earth is greater than the attraction they relatively and collectively exercise towards each other4 ,but if the size of the balls be different1 the attraction of the greater will be more evident1 as shown below1 where the points of meeting are indicated respectively 7figs4 #ae and #af74 ,these experiments will illustrate the phenomena of falling bodies4 ,gravity is the cause of this1 because every object on the surface of the earth is very much smaller than the earth itself1 and therefore all bodies fall towards the centre of the earth4 ,a certain time is thus occupied1 and we can find the velocity or rapidity of a falling body very easily4 ,on the earth a body1 if let fall1 will pass through a space sixteen feet in the first second2 and as the attraction of the earth still continues and is exercised upon a body already in rapid motion1 this rate of progress must be proportionately increased4 ,just as when steam is kept up in an engine running down hill1 the velocity of the train will rapidly increase as it descends the gradient4 ,illustration3 ,figs4 #ae and #af4 ,a body falling1 then1 descends sixteen feet in the first second1 and for every succeeding second it assumes a greater velocity4 ,the distance the body travels has been calculated1 and the space it passes through has been found to increase in proportion to the square of the time it takes to fall4 ,for instance1 suppose you drop a stone from the top of a cliff to the beach1 and it occupies two seconds in falling1 if you multiply #b #b1 and the result by sixteen1 you will find how high the cliff is3 in this 7supposed7 case it is 7omitting decimals7 sixty-four feet high4 ,the depth of a well can also be ascertained in the same way1 leaving out the effect of air resistance4 ,but if we go up into the air1 the force of gravity will be diminished4 ,the attraction will be less1 because we are more distant from the centre of the earth4 ,this decrease is scarcely1 if at all1 perceptible1 even on very high mountains1 because their size is not great in comparison with the mass of the earth's surface4 ,the rule for this is that gravity decreases in proportion to the square of the distance4 ,so that if at a certain distance from the earth's surface the force of attraction be #a1 if the distance be doubled the attraction will be only one quarter as much as before--not one-half4 ,gravity has exactly the same influence upon all bodies1 and the force of the attraction is in proportion to the mass4 ,all bodies of equal mass will fall in the same time in a given distance4 ,two coins 7or a coin and a feather in vacuo7 will fall together4 ,but in the air the feather will remain far behind the coin1 because nearly all the atoms of the former are resisted by the air1 while in the coin only some particles are exposed to the resistance1 the density of the latter preventing the air from reaching more than a few atoms1 comparatively speaking4 ,the theory of weight and gravitation1 and experiments relating to the falling of bodies1 may be easily demonstrated with ordinary objects that we have at hand4 ,i take a halfpenny and a piece of paper1 which ,i cut in the shape of the coin1 and holding them side by side1 ,i drop them simultaneously2 the halfpenny reaches the ground some time before the paper1 a result quite in accordance with the laws of gravitation1 as one must bear in mind the presence of air1 and the different resistance it offers to two bodies differing in density4 ,i next place the paper disc on the upper surface of the piece of money1 and then drop them simultaneously4 ,the two objects now reach the ground at the same time1 the paper1 in contact with the halfpenny1 being preserved from the action of the air4 ,this experiment is so well known that we need not further discuss it2 but it must be plainly evident that it is capable of development in experiments on phenomena relating to falling bodies4#g ,when a body influenced by the action of a force acts1 in its turn1 upon another1 the latter reacts in an opposite manner upon the first1 and with the same intensity4 ,the ,attraction of ,cohesion is the attraction of particles of bodies to each other at very small distances apart4 ,cohesion has received various names in order to express its various degrees4 ,for instance1 we say a body is tough or brittle1 or soft or hard1 according to the degrees of cohesion the particles exercise4 ,we know if we break a glass we destroy the cohesion2 the particles cannot be reunited4 ,most ,liquid particles can be united1 but not all4 ,oil will not mix with water4 ,the force of cohesion depends upon heat4 ,heat expands everything1 and the cohesion diminishes as temperature increases4 ,there are some objects or substances upon the earth the particles of which adhere much more closely than others1 and can only1 with very great difficulty1 be separated4 ,these are termed ,solids4 ,there are other substances whose particles can easily be divided1 or their position altered4 ,these are called ,fluids4 ,a third class seem to have little or no cohesion at all4 ,these are termed ,gases4 ,adhesion is also a form of attraction1 and is cohesion existing on the surfaces of two bodies4 ,when a fluid adheres to a solid we say the solid is wet4 ,we turn this natural adhesion to our own purposes in many ways1--we whitewash our walls1 and paint our houses2 we paste our papers together1 etc4 ,on the other hand1 many fluids will hot adhere4 ,oil and water have already been instanced4 ,mercury will not stick to a glass tube1 nor will the oiled glass tube retain any water4 ,we can show the attraction and repulsion in the following manner3--,let one glass tube be dipped into water and another into mercury1 you will see that the water will ascend slightly at the side1 owing to the attraction of the glass1 while the mercury will be higher in the centre1 for it possesses no attraction for the glass 7fig4 #ag74 ,if small1 or what are termed capillary 7or hair7 tubes1 be used 7fig4 #ah71 the water will rise up in the one tube1 while in the other the mercury will remain lower than the mercury outside the tube4 7,see ,capillarity47 ,illustration3 ,fig4 #ag4 ,illustration3 ,fig4 #ah4 ,chemical ,attraction is the force by which two different bodies unite to form a new and different body from either4 ,this force will be fully considered in ,,chemistry1 in a future part4 ,it is needless for us to dwell upon the uses of these ,forces of ,nature4 ,gravity and ,cohesion being left out of our world1 we can imagine the result4 ,the earth and sun and planets would wander aimlessly about2 we should float away into space1 and everything would fall to pieces1 while our bodies would dissolve into their component parts4 ,the ,balance and ,centre of ,gravity4--,we have spoken at some length about ,gravity1 and now we must say something respecting that point called the ,centre of ,gravity1 and the ,balance1 and upon the latter we have a few remarks to make first1 for a well-adjusted balance is a most useful thing1 and we will show you how to make one1 and then proceed to our illustrations of the ,centre of ,gravity1 and explain it4 ,illustration3 ,fig4 #ai4--,torsion balance1 which can easily be constructed1 capable of weighing a milligram one-tenth of full size4 ,all those who cultivate experimental science are aware that it is useful to unite with theoretical ideas that manual dexterity which is acquired by the student accustoming himself to practical operations4 ,one cannot too strongly urge both chemists and physicists to exercise themselves in the construction of the appliances they require1 and also to modify those already existing1 which may be adapted to their wants4 ,in a large number of cases it is possible to manufacture1 at small expense1 delicate instruments1 capable of rendering the same service as the most elaborate apparatus4 ,important scientific labours have often been undertaken by men whose laboratories were most simple1 who1 by means of skill and perseverance1 knew how to do great things with small resources4 ,a delicate balance1 for instance1 indispensable alike to chemist and physicist1 can be manufactured at little cost in different ways4 ,a thin platinum wire and a piece of wood is all that is needed to make a balance capable of weighing a milligram2 and to make a very sensitive hydrostatic balance1 little is required besides a glass balloon4 ,fig4 #ai represents a small torsion balance of extreme simplicity4 ,a thin platinum wire is stretched horizontally through two staples1 from the wooden supports1 ,a ,b1 which are fixed in a deal board4 ,a very thin1 delicate lever1 ,c ,d1 cut in wood1 or made with a wisp of straw1 is fixed in the centre of the platinum wire by means of a small clip1 which secures it firmly4 ,this lever is placed in such a manner that it is raised perceptibly out of the horizontal line4 ,at ,d is fixed a paper scale1 on which is put the weight of a centigram4 ,the lever is lowered to a certain point1 slightly twisting the platinum wire4 ,near the end of the lever a piece of wood1 ,f1 is fixed1 on which is marked the extreme point of its movements4 ,ten equi-distant divisions are marked between these two points1 which represent the distance traversed by the lever under the weight of the milligram4 ,if a smaller weight than a centigram is placed on the paper scale the lever falls1 and balances itself after a few oscillations4 ,if it falls four divisions1 it is evident that the substance weighs four milligrams4 ,taking a rather thicker platinum wire1 to which a shorter lever must be adapted1 one can weigh the decigram1 and so on4 ,it would be an easy matter1 also1 to make1 on the same model1 balances for weighing considerable weights4 ,the platinum wire should be replaced by iron wires of larger diameter1 firmly stretched1 and the lever should be made of a piece of very resisting wood4 ,one can also1 by adaptation1 find the exact value of the most trifling weights4 ,by lengthening a very fine platinum wire several yards1 and adapting a long1 slender lever1 it will not be impossible to ascertain the tenth of a milligram4 ,in this latter case the balance can be set when it is wanted4 ,fig4 #bj represents ,nicholson's ,areometer1 which any one may construct for himself1 and which1 as it is here represented1 constitutes another kind of balance4 ,a glass balloon1 filled with air1 is hermetically closed with a cork1 through which is passed a cylinder of wood1 surmounted by a wooden disc1 ,d4 ,the apparatus is terminated at its lower end by a small tray1 ,c1 on which one can put pieces of lead in variable quantities4 ,it is then plunged into a glass filled with water4 ,the pieces of lead on the tray1 ,c1 are added by degrees1 until the stem of the areometer rises almost entirely above the level of the water2 it is next passed through a ring1 which keeps it in position1 and which is fastened to the upper part of the glass by means of four iron wires in the shape of a cross4 ,the stem is divided in such a way that the space comprised in each division represents the volume of a cubic centimetre4 ,thus arranged1 the apparatus constitutes a balance4 ,the object to be weighed is placed on the disc1 ,d1 and the areometer sinks in the water1 oscillates1 and then remains in equilibrium4 ,if the stem sinks five divisions1 it is evident that the weight of the object corresponds to that of five cubic centimetres of displaced water1 or five grams4 ,illustration3 ,fig4 #bj4--,nicholson's ,areometer1 contrived to serve as a balance4 ,it is obvious1 therefore1 from the preceding examples1 that it is not impossible to construct a weighing apparatus with ordinary and very inexpensive objects4 ,we can1 in the same way1 show that it is possible to perform instructive experiments with no appliances at all1 or1 at any rate1 with common things1 such as everyone has at hand4 ,the lamented ,balard1 whose loss science has had recently to deplore1 excelled in chemical experiments without a laboratory2 fragments of broken glass or earthenware were used by him for improvising retorts1 bottles and vases for forming precipitates1 and carrying on many important operations4 ,scheele also operated in like manner2 he knew how to make great discoveries with the humblest appliances and most slender resources4 ,one cannot too earnestly endeavour to imitate such leaders1 both in teaching others and instructing oneself4 ,the laws relating to the weight of bodies1 the centre of gravity1 and stable or unstable equilibrium1 may be easily taught and demonstrated by means of a number of very familiar objects4 ,by putting into the hands of a child a box of soldiers cut in elder-wood1 the end of each fixed into half a bullet1 we provide him with the means of making some easy experiments on the centre of gravity4 ,according to some authorities on equilibrium1 it is not impossible1 with a little patience and delicacy of manipulation1 to keep an egg balanced on one of its ends4 ,this experiment should be performed on a perfectly horizontal surface1 a marble chimney-piece1 for example4 ,if one can succeed in keeping the egg up1 it is1 according to the most elementary principles of physics1 because the vertical line of the centre of gravity passes through the point of contact between the end of the egg and the surface on which it rests4 ,illustration3 ,fig4 #ba4--;,experiment on 8centre of gravity40 ,fig4 #ba reproduces a curious experiment in equilibrium1 which is performed with great facility4 ,two forks are stuck into a cork1 and the cork is placed on the brim of the neck of a bottle4 ,the forks and the cork form a whole1 of which the centre of gravity is fixed over the point of support4 ,we can bend the bottle1 empty it even1 if it contains fluid1 without the little construction over its mouth being in the least disturbed from its balance4 ,the vertical line of the centre of gravity passes through the point of support1 and the forks oscillate with the cork1 which serves as their support1 thus forming a movable structure1 but much more stable than one is inclined to suppose4 ,this curious experiment is often performed by conjurors1 who inform their audience1 that they will undertake to empty the bottle without disturbing the cork4 ,if a woodcock has been served for dinner1 or any other bird with a long beak1 take off the head at the extreme end of the neck2 then split a cork so that you can insert into it the neck of the bird1 which must be tightly clipped to keep it in place2 two forks are then fixed into the cork1 exactly as in the preceding example1 and into the bottom of the cork a pin is inserted4 ,this little contrivance is next placed on a piece of money1 which has been put on the opening of the neck of the bottle1 and when it is fairly balanced1 we give it a rotatory movement1 by pushing one of the forks as rapidly as we please1 but as much as possible without any jerk 7fig4 #bb74 ,we then see the two forks1 and the cork surmounted by the woodcock's head1 turning on the slender pivot of a pin4 ,nothing can be more comical than to witness the long beak of the bird turning round and round1 successively facing all the company assembled round the table1 sometimes with a little oscillation1 which gives it an almost lifelike appearance4 ,this rotatory movement will last some time1 and wagers are often laid as to which of the company the beak will point at when it stops4 ,in laboratories1 wooden cylinders are often to be seen which will ascend an inclined plane without any impulsion4 ,this appears very surprising at first1 but astonishment ceases when we perceive that the centre of gravity is close to the end of the cylinder1 because of a piece of lead1 which has been fixed in it4 ,illustration3 ,fig4 #bb4--;,another experiment on the same subject4 ,illustration3 ,fig4 #bc4--;,automatic puppets4 ,fig4 #bc gives a very exact representation of a plaything which was sold extensively on the ,boulevards at ,paris at the beginning of the ,new ,year4 ,this little contrivance1 which has been known for some time1 is one of the most charming applications of the principles relating to the centre of gravity4 ,with a little skill1 any one may construct it for himself4 ,it consists of two little puppets1 which turn round axles adapted to two parallel tubes containing mercury4 ,when we place the little contrivance in the position of fig4 #bd1 the mercury being at a1 the two dolls remain motionless1 but if we lower the doll ,s1 so that it stands on the second step 7,no4 #b7 of the flight1 as indicated in fig4 #be1 the mercury descends to b at the other end of the tube2 the centre of gravity is suddenly displaced2 the doll ,r then accomplishes a rotatory movement1 as shown by the arrow in fig4 #be1 and finally alights on step ,no4 #c4 ,the same movement is also effected by the doll ,s1 and so on1 as many times as there are steps4 ,the dolls may be replaced by a hollow cylinder of cartridge paper closed at both ends1 and containing a marble2 the cylinder1 when placed vertically on an inclined plane1 descends in the same way as the puppets4 ,the laws of equilibrium and displacement of the centre of gravity1 are rigorously observed by jugglers1 who achieve many wonderful feats1 generally facilitated by the rotatory motion given to the bodies on which they operate1 which brings into play the centrifugal force4 ,the juggler who balances on his forehead a slender rod1 on the end of which a plate turns round1 would never succeed in the experiment if the plate did not turn on its axis with great rapidity4 ,but by quick rotation the centre of gravity is kept near the point of support4 ,we need hardly remark1 too1 that it is the motion of a top that tends to keep it in a vertical position4 ,illustration3 ,fig4 #bd4--;,first position of the puppets4 ,illustration3 ,fig4 #be4--,second position of the puppets4 ,many experiments in mechanical physics may occur to one's mind4 ,to conclude the enumeration of those we have collected on the subject1 ,i will describe the method of lifting a glass bottle full of water by means of a simple wisp of straw4 ,the straw is bent before being passed into the bottle of water1 so that1 when it is lifted1 the centre of gravity is displaced1 and brought directly under the point of suspension4 ,fig4 #bf shows the method of operation very plainly4 ,it is well to have at hand several pieces of straw perfectly intact1 and free from cracks1 in case the experiment does not succeed with the first attempt4 ,having now seen how this point we call the centre of gravity acts1 we may briefly explain it4 ,illustration3 ,fig4 #bf4--,lifting a bottle with a single straw4 ,the centre of gravity of a body is that point in which the sum of the forces of gravity1 acting upon all the particles1 may be said to be united4 ,we know the attraction of the earth causes bodies to have a property we call ,weight4 ,this property of weight presses upon every particle of the body1 and acts upon them as parallel forces4 ,for if a stone be broken all the portions will equal the weight of the stone2 and if some of them be suspended1 it will be seen that they hang parallel to each other1 so we may call these weights parallel forces united in the whole stone1 and equal to a single resultant4 ,now1 to find the centre of gravity1 we must suspend the body1 and it will hang in a certain direction4 ,draw a line from the point of suspension1 and suspend the body again3 a line drawn from that point of suspension will pass through the same place as the former line did1 and so on4 ,that point is the centre of gravity of that suspended body4 ,if the form of it be regular1 like a ball or cylinder1 the centre of gravity is the same as the mathematically central point4 ,in such forms as pyramids it will be found near the largest mass2 viz41 at the bases1 about one-fourth of the distance between the apex and the centre of gravity of the base4 ,when the centre of gravity of any body is supported1 that body cannot fall4 ,so the well-known leaning towers are perfectly safe1 because their lines of direction fall within the bases4 ,the centre of gravity is in the centre of the leaning figure4 ,the line of direction drawn vertically from that point falls within the base2 but if the tower were built up higher1 so that the centre of gravity were higher1 then the structure would fall1 because the line of direction would fall without the base4 ,we see that animals 7and men7 are continually altering the position of the centre of gravity2 for if a man bears a load he will lean forward1 and if he takes up a can of water in one hand he will extend the other to preserve his balance or equilibrium4 ,illustration3 ,fig4 #bg4--;,balancing a weight on a nail and key4 ,the experiment shown in the accompanying illustration is apparently very difficult1 but it will be found easy enough in practice if the hand be steady4 ,take a key1 and by means of a crooked nail1 or 8holdfast10 attach it to a bar of wood by a string tied tightly round the bar1 as in the picture4 ,to the other extremity of the bar attach a weight1 and then drive a large-headed nail into the table4 ,it will be found that the key will balance1 and even move upon the head of the nail1 without falling4 ,the weight is under the table1 and the centre of gravity is exactly beneath the point of suspension4 ,another simple experiment may prove amusing4 ,into a piece of wood insert the points of two knives1 and at the centre of the end of the bar insert a needle between the knife handles4 ,the wood and the knives may then be balanced on another needle fixed in a cork at ,a4 ,illustration3 ,fig4 #bh4--;,another experiment4 ,we may conclude this chapter by summing up in a few words what the ,centre of ,gravity is4 ,we can define it as 8that point in a body upon which the body1 acted on solely by the force of gravity1 will balance itself in all positions40 ,such a point exists in every body1 and equally in a number of bodies fastened tightly together4 ,the ,centre of ,gravity has by some writers been denominated the ,centre of ,parallel ,forces1 or the ,centre of ,magnitude1 but the ,centre of ,gravity is the most usual and best understood term4 ,,footnotes3 #g ,m4 ,a4 ,g4 has written us an interesting letter on the subject of similar experiments1 which we here transcribe3-- 8,when a siphon of seltzer water has been opened some little time1 and the equilibrium of tension is nearly established between the escaped gas and the dissolved gas1 a vertical stream of bubbles is seen to rise from the bottom of the apparatus1 which present a very clear example of the law of ascension of bubbles2 that is to say 7putting out of the question the expansion of the bubbles in their passage upwards71 it is an inverse representation of the law of gravity affecting falling bodies4 ,the bubbles1 in fact1 detach themselves from their starting point with perfect regularity2 and as the interval varies in one file from another1 we have before us a multiplied representation of that terrible law which ,attwood's machine made such a bugbear to the commercial world4 ,i believe it is possible1 by counting the number of bubbles that detach themselves in a second1 in each file1 and the number which the whole stream contains at a given instant1 to carry the verification further2 but ,i must confess that ,i have not done so myself40 ,,chapter ,,iv4 ,,some ,,properties ,,of ,,solid ,,bodies--,,inertia--,,motion--,,frictio n--,,the ,,pendulum--,,equilibrium4 ,those who have followed us through the preceding pages have now1 we hope1 some ideas upon ,gravity and the ,forces of ,nature4 ,in speaking of ,forces we said 8,force was a cause of ,motion40 ,let us now consider ,inertia1 and ,motion with its accompanying opponent1 ,friction4 ,illustration3 ,fig4 #bi4--,shock communicated by elasticity4 ,,inertia is the passiveness of ,matter4 ,this perfect indifference to either rest or motion makes the great distinction between living and lifeless matter4 ,inertia1 or ,vis ,inertia1 is this passiveness4 ,now1 to overcome this indifference we must use force1 and when we have applied force to matter we set it in motion2 that is1 we move it4 ,when we move it we find a certain resistance which is always proportionate to the force applied4 ,in mechanics this is termed ,action1 and ,reaction1 which are always equal forces acting in opposite directions4 ,this is ,newton's law1 and may be explained by a 8weight0 on a table1 which presses against the table with the same force with which the table presses against the 8weight02 or when you strike a ball1 it strikes the hand with the same force4 ,we can communicate motion by elasticity4 ,for instance1 if we place a number of coins upon a table touching each other and in a straight line1 and strike the last coin of the line by pushing another sharply against it1 the piece at the opposite extremity will slip out of its place from the effect of the shock transmitted by the coin at the other end 7fig4 #bi74 ,illustration3 ,fig4 #cj4--;,experiment to illustrate inertia4 ,when two forces act upon a body at the same time1 it takes a direction intermediate4 ,this is known as the resultant4 ,the enormous forces exercised by the heavenly bodies will be treated of later4 ,we will first consider ,inertia4 ,there are several experiments relating to the subject of ,inertia which may be performed4 ,i once witnessed one quite accidentally when taking a walk4 ,illustration3 ,fig4 #ca4--;,another experiment on the same subject4 ,i was one day passing the ,observatory at ,paris1 when ,i noticed a number of people collected round a professor1 who after executing several juggling tricks1 proceeded to perform the curious experiment ,i am about to describe4 ,he took a broomstick and placed it horizontally1 passing the ends through two paper rings4 ,he then asked two children to hold the paper rings by means of two razors1 so that the rings rested on the blade4 ,this done1 the operator took a stout stick1 and1 with all his strength1 struck the broomstick in the centre2 it was broken into shivers1 but the paper rings were not torn in the least1 or even cut by the razors6 ,one of my friends1 ,m4 ,m----1 a painter1 showed me how to perform this experiment as represented in the illustration 7fig4 #cj74 ,a needle is fixed at each end of the broomstick1 and these needles are made to rest on two glasses1 placed on chairs2 the needles alone must be in contact with the glasses4 ,if the broomstick is then struck violently with another stout stick1 the former will be broken1 but the glasses will remain intact4 ,the experiment answers all the better the more energetic the action4 ,it is explained by the resistance of inertia in the broomstick4 ,the shock suddenly given1 the impulse has not time to pass on from the particles directly affected to the adjacent particles2 the former separate before the movement can be transmitted to the glasses serving as supports4#h ,illustration3 ,fig4 #cb4--;,extracting a 8man0 from a pile of draughts without overturning the pile4 ,the experiment represented in fig4 #ca is of the same nature4 ,a wooden ball is suspended from the ceiling by a rather slender thread1 and a similar thread is attached to the lower end of the ball4 ,if the lower thread is pulled forcibly it will break1 as shown in the illustration2 the movement communicated to it has not time to pass into the ball2 if1 on the contrary1 it is pulled very gradually and without any shock1 the upper thread instead will break1 because in this case it supports the weight of the ball4 ,motion is not imparted simultaneously to all parts of a body1 but only to the particles first exposed to a blow1 for instance4 ,one might multiply examples of this4 ,if a bullet be shot from a gun1 it will make a round hole in a piece of wood or glass1 whilst if thrown by the hand1--that is to say1 with much less force1-- it will shiver the wood or the pane of glass to pieces4 ,when the celerity of the motive force is very great1 the particles directly affected are disturbed so quickly that they separate from the adjacent particles before there is time for the movement to be communicated to the latter4 ,it is possible1 for the same reason1 to extract from a pile of money a piece placed in the middle of the pile without overturning the others4 ,it suffices to move them forcibly and quickly with a flat wooden ruler4 ,the experiment succeeds very well also if performed with draughtsmen piled up on the draught-board 7fig4 #cb74 ,illustration3 ,fig4 #cc4--;,calling out a sixpence from the glass4 ,fig4 #cc represents another experiment which belongs to the laws of resisting force4 ,a sixpence is placed on a table covered with a cloth or napkin4 ,it is covered with a glass1 turned over so that its brim rests on two penny pieces4 ,the problem to be solved is how to extract the sixpence from underneath the glass without touching it1 or slipping anything beneath it4 ,to do this it is necessary to scratch the cloth with the nail of the forefinger2 the elasticity of the material communicates the movement to the sixpence1 which slowly moves in the direction of the finger1 until it finally comes out completely from beneath the glass4 ,we may give another experiment concerning ,inertia4 ,take a strip of paper1 and upon it place a coin1 on a marble chimney-piece1 as in the illustration4 ,if1 holding the paper in the left hand1 you strike it rapidly and forcibly1 you will be enabled to draw away the paper without causing the coin 7say a five-shilling-piece7 to fall down 7fig4 #cd74 ,it is not impossible to draw away a napkin laid as a tablecloth for one person's dinner1 without disturbing the various articles laid upon it4 ,a quick motion is all that is necessary1 keeping the napkin tightly extended by the hands at the same time4 ,this latter experiment1 however1 is not recommended to boys home for the holidays1 as they may unwillingly practise a feat analogous to that executed by ,humpty-,dumpty1 and find equal difficulty to match the pieces4 ,illustration3 ,fig4 #cd4--;,drawing a slip of paper from beneath a coin4 ,we will now examine the term ,motion4 ,a body is said to be in motion when it changes its position in relation to surrounding objects4 ,to perceive motion the surrounding objects must be relatively at rest1 for if they all hurried along at the same rate no motion would be perceptible4 ,this is evident1 for when we stand still trees and houses appear stationary1 as do we ourselves1 but we know we all are rushing round with the earth1 though our relative positions are unchanged4 ,hence there is no absolute rest4 ,what are the causes of motion8--,gravity is one4 ,the influence of heat1 which is itself caused by the motion of atoms1 the effects of electricity1 etc41 and finally1 the power of force in men or animals--any of these causes will produce motion4 ,but a body at rest cannot put itself in motion1 nor can a body in motion stop itself1 or change its condition of motion4 ,but you may say a body will stop itself4 ,your ball on the ground1 or even upon ice1 will eventually come to a stop4 ,we fire a bullet1 and it will stop in time4 ,we reply it does not stop of itself4 ,the resistance of the ,air and ,friction tend to bring the body in motion to a state of rest4 ,in the case of a bullet gravity brings it down4 ,there is no need to insist upon the resistance offered by the air even when it is not rushing violently past to fill up a vacuum beyond us1 and called a breeze1 or high wind4 ,but we may say something of ,friction4 ,friction is derived from the ,latin frico1 to rub1 and expresses the resistance to motion which arises from uneven surfaces4 ,it is a passive resistance1 and depends upon the force which keeps the bodies together4 ,thus a train running upon a smooth iron rail would never be able to proceed but for friction1 which gives the necessary purchase or grip to the wheel and rail in contact4 ,no surface is perfectly smooth1 for we must push a body upon the smoothest surface we possess4 ,friction tends to resist motion always1 and is the cause of a great loss of power in mechanics1 though it is employed to stop motion by certain appliances1 such as 8brakes0 and 8drags10 for sliding friction is greater than rolling friction4 ,but without friction most structures would fall to pieces1 and all forward motion would cease4 ,so though it is an inconvenient force to overcome1 we could not do without it4 ,if a body is set in motion1 we see that the tendency of it is to go on for ever4 ,such1 indeed1 is the case with the stars2 but so long as we are within the influence of the earth's attraction1 we cannot expect such a result4 ,we know now what motion is2 we must also1 to understand it perfectly1 consider its direction and its velocity4 ,the line which indicates the way from the starting point to the end is the direction of the object in motion1 and the rate it moves at its velocity4 ,the latter is calculated at so many miles an hour1 as a train2 or so many feet in a second if the object be a shot1 or other very rapidly-moving body4 ,in equal velocity the same distance is traversed in the same time2 and so if a train run a mile in a minute1 we know it will travel sixty miles in an hour1 and is therefore during that minute going at the rate of sixty miles an hour4 ,we have already spoken of the velocity of a stone falling from a cliff as sixteen feet in a second1 and a stone thrown into the air to rise sixteen feet will be a second in going up1 and a second in descending4 ,but the velocity will be accelerated in the descent after the first second of time1 and retarded in the upward cast by gravity4 ,so we have two terms--accelerated and retarded velocity--used to express an increased or decreased force of attraction4 ,perpetual motion has often been sought1 but never discovered1 nor will it ever be till the elixir of life has been found4 ,it is quite impossible to construct any machine that will work without friction2 if any work be done energy will be expended and transformed into other energy1 so the total must be diminished by so much as was employed to transform the remainder4 ,no body can give unlimited work1 therefore the perpetual motion theory is untenable and impossible4 ,the pendulum is considered the nearest approach to perpetual motion4 ,this is so well known that no description is needed1 but we may say a few words concerning it4 ,by the diagram1 we see that if we lift the ball to b1 and let it fall1 it will descend to l1 and pass it to a opposite1 nearly as far from l as b is from it4 ,so the oscillations will continue1 each beat being less and less1 till rest is reached by the action of gravity 7page #bc74 ,were it not for friction and the pressure of the air1 the oscillations would continue for ever2 as it is1 it declines by shorter swings till it remains in equilibrium4 ,illustration3 ,fig4 #ce4--,the pendulum4 ,the seconds' pendulum oscillates sixty times an hour1 and must be of a certain length in certain places4 ,in ,london it is #ciacic inches1 and furnishes a certain standard of length1 and by an ,act of ,parliament the yard is divided into #cf parts1 and #ciacic such parts make the seconds' pendulum in the latitude of ,london 7in vacuo7 in a temperature of #fb4 ,illustration3 ,fig4 #cf4--;,centrifugal ,force4 ,but the same pendulum will not perform the same number of oscillations in one minute in all parts of the globe4 ,at the equator they will be less1 and at the pole more4 ,thus it was discovered that1 as the movements of the pendulum are dependent upon the force of gravity1 and as this force decreases the farther we get from the centre of the earth1 the equator must be farther from the earth's centre than the poles1 and therefore the poles must be depressed4 ,the decline of the pendulum at the equator is also1 in a measure1 due to ,centrifugal ,force4 ,centrifugal ,force1 which means 8flying from the centre10 is the force which causes an object to describe a circle with uniform velocity1 and fly away from the centre2 the force that counteracts it is called the centripetal force4 ,a very simple experiment will illustrate it4 ,illustration3 ,fig4 #cg4--;,another illustration of centrifugal force4 ,to represent its action1 we shall have recourse to an ordinary glass tumbler placed on a round piece of cardboard1 held firmly in place by cords4 ,some water is poured in the glass1 and we then show that it can be swung to and fro and round without the water being spilt1 even when the glass is upside down 7fig4 #cf74 ,another experiment on the same subject is as shown in the above illustration1 by which a napkin ring can be kept in revolution around the forefinger1 and by a continued force the ring may be even held suspended at the tip of the finger1 apparently in the air1 without support 7fig4 #cg74 ,,footnotes3 #h ,the experiment we have just described is a very old one4 ,m4 ,v4 ,sircoulon has told us that it was described at length in the works of ,rabelais4 ,the following remarks are in 8,pantagruel10 book ,,ii41 chap4 xvii4 8,panur then took two glasses of the same size1 filled them with water1 and put one on one stool1 and the other on another1 about five feet apart1 and placed the staff of a javelin about five-and-a-half feet long across1 so that the ends of the staff just touched the brim of the glasses4 ,that done1 he took a stout piece of wood1 and said to the others3 8,gentlemen1 this is how we shall conquer our enemies2 for in the same way that ,i shall break this staff between these two glasses1 without the glasses being broken or injured1 or spilling a single drop of water1 so shall we break the head of our ,dipsodes1 without any injury to ourselves1 and without getting wounded4 ,but that you may not think there is magic in it1 you1 ,eusthenes1 strike with this stick as hard as you can in the centre40 ,this ,eusthenes did1 and the staff broke in two pieces1 without a drop of water being spilt4 ,,chapter ,v4 ,,gases ,,and ,,liquids--,,pressure ,,of ,,the ,,air--,,experiments4 ,we have more than once referred to the pressure of the air which exerts a great influence upon bodies in motion1 but a few experiments will make this more obvious1 and clearly demonstrate the fact4 ,we have also told you some of the properties of ,solids1 such as ,weight1 ,inertia1 ,friction1 and ,resistance1 or ,strength4 ,solids also1 as we have seen1 occupy space1 and cannot be readily compressed1 nor bent to other shapes4 ,now the subject of the ,pressure of the ,air leads us to the other forms of ,matter2 namely1 ,gases and ,liquids1 which will be found very interesting to study4 ,illustration3 ,fig4 #ch4--;,blowing an egg from one glass to another4 ,the force of air can very soon be shown as acting with considerable pressure upon an egg in a glass4 ,by blowing in a claret glass containing a hard-boiled egg1 it is possible to cause the egg to jump out of the glass2 and with practice and strength of lungs it is not impossible to make it pass from one glass to another1 as per illustration 7fig4 #ch74 ,the force of heated air ascending can also be ascertained by cutting up a card into a spiral1 and holding it above the flame of a lamp 7fig4 #ci74 ,the spiral1 if lightly poised1 will turn round rapidly4 ,now let us turn to a few experiments with the air1 which is composed in two gases1 ,oxygen and ,nitrogen1 of which we shall hear more when we come to ,,chemistry4 ,illustration3 ,fig4 #ci4--,movement of heated air4 ,illustration3 ,fig4 #dj4--,pressure of the air4 ,it is not intended here to prosecute researches1 but rather to sketch a programme for instruction1 based on amusing experiments in ,physics1 performed without apparatus4 ,the greater part of these experiments are probably well known1 and we desire to say that we merely claim to have collected and arranged them for our descriptions4 ,we must also add that we have performed and verified these experiments2 the reader1 therefore1 can attempt them with every certainty of success4 ,we will suppose that we are addressing a young auditory1 and commence our course of ,physics with some facts relating to the pressure of air4 ,a wine glass1 a plate1 and water1 will serve for our first experiments4 ,pour some water on the plate1 light a piece of paper resting on a cork1 and cover the flame with the glass which ,i turn upside down 7fig4 #dj74 ,what follows8--,the water rises in the glass4 ,why8--,because the burning of the paper having absorbed a part of the oxygen1 and the volume of confined gas being diminished1 the pressure of the outer air has driven back the fluid4 ,i next fill a goblet with water up to the brim1 and cover it with a sheet of paper which touches both the edge of the glass and the surface of the water4 ,i turn the glass upside down1 and the sheet of paper prevents the water running out1 because it is held in place by atmospheric pressure 7fig4 #da74 ,it sometimes happens that this experiment does not succeed till after a few attempts on the part of the operator2 thus it is prudent to turn the glass over a basin1 so that1 in case of failure1 the water is not spilt4 ,having obtained a vase and a bottle1 both quite full of water1 take the bottle1 holding it round the neck so that the thumb can be used as a stopper1 then turn it upside down1 and pass the neck into the water in the vase4 ,remove your thumb1 or stopper1 keeping the bottle in a vertical position1 and you will see that the water it contains does not escape1 but remains in suspension4 ,it is atmospheric pressure which produces this phenomenon4 ,if1 instead of water1 we put milk in the bottle1 or some other fluid denser than water1 we shall see that the milk also remains suspended in the bottle1 only there is a movement of the fluid in the neck of the bottle1 and on careful examination we perceive very plainly that the milk descends to the bottom of the vase1 and the water rises into the bottle4 ,here1 again1 it is atmospheric pressure which maintains the fluid in the bottle1 but the milk descends1 because fluids are superposed according to their order of density1 and the densest liquid falls to the bottom4 ,this can be verified by means of the phial of the four elements1 which is a plain1 long1 and narrow bottle1 containing equal volumes of metallic mercury1 salt water1 alcohol1 and oil4 ,these four liquids will lie one on the top of the other without ever mixing1 even if shaken4 ,another experiment as to the pressure of the air may be made 7fig4 #db74 ,take a penny and press it against some oaken bookcase or press1 rub the coin against the wood for a few seconds1 then press it1 and withdraw the fingers4 ,the coin will continue to adhere to the wood4 ,the reason of this is1 because by the rubbing and the pressure you have dispersed the film of air which was between the penny and the wood1 and under those conditions the pressure of the atmospheric air was sufficient to keep the penny in its place4 ,illustration3 ,fig4 #da4--,pressure of the air4 ,or1 again1 let us now add a water-bottle and a hard-boiled egg to our appliances2 we will make use of the air-pump1 and easily perform another experiment4 ,i light a piece of paper1 and let it burn1 plunging it into a water-bottle full of air4 ,when the paper has been burning a few seconds ,i close the opening of the water-bottle by means of a hard-boiled egg1 which ,i have previously divested of its shell1 so that it forms a hermetic stopper4 ,the burning of the paper has now caused a vacuum of air in the bottle1 and the egg is gradually thrust in by the atmospheric pressure outside4 ,fig4 #dc exhibits it slowly lengthening and stretching out as it passes through the aperture2 then it is suddenly thrust completely into the bottle with a little explosive sound1 like that produced by striking a paper bag expanded with air4 ,this is atmospheric pressure demonstrated in the clearest manner1 and at little cost4 ,illustration3 ,fig4 #db4--;,coin adhering by pressure of air4 ,if it is desired to pursue a little further the experiments relating to atmospheric pressure1 it will be easy enough to add to the before-mentioned appliances a closed glass-tube and some mercury1 and one will then have the necessary elements for performing ,torricelli's and ,pascal's experiments1 and explaining the theory of the barometer 7page #eb74 ,an amusing toy1 well-known to schoolboys1 called the 8sucker10 may also be made the object of many dissertations on the vacuum and the pressure of air4 ,it is composed of a round piece of soft leather1 to the centre of which is attached a small cord4 ,this leather is placed on the ground and pressed under foot1 and when the cord is pulled it forms a cupping-glass1 and is only separated with difficulty from the pavement4 ,atmospheric air1 in common with other gases1 has a tendency to fill any space into which it may enter4 ,the mutual attraction of particles of air is nil2 on the contrary1 they appear to have a tendency to fly away from each other2 this property is called 8repulsion40 ,air also possesses an expansive property--a tendency to press against all the sides of any vessel in which it may be enclosed4 ,of course the larger the vessel containing a given quantity of air1 the less actual pressure it will exert on the sides of the vessel4 ,the elasticity of air therefore decreases with increasing expansion1 but it gains in elasticity or force when compressed4 ,there is a law in ,physics which expresses the relation between expansion and elasticity of gases1 which may be said to be as follows3-- ,the elasticity 7of a gas7 is in inverse ratio to the space it occupies1 and therefore by compressing air into a small space we can obtain a great force1 as in the air-gun and the pop-gun of our youthful days4 ,illustration3 ,fig4 #dc4--;,hard boiled egg1 divested of its shell1 passing through the neck of a glass bottle1 under the influence of atmospheric pressure4 ,in the cut below we can illustrate the principle of the pop-gun4 ,the chamber full of air is closed by a cork and by an air-tight piston 7,s7 at p and p4 ,when the piston is pushed into the chamber the air is compressed between it and the stopper1 which at length flies out forcibly with a loud report ,illustration3 ,fig4 #dd4--,the principle of the pop-gun4 ,we have said that the tendency of air particles is to fly away from each other1 and were it not for the earth's attraction the air might be dispersed4 ,the height of the atmosphere has been variously estimated from a height of #de miles to #bab miles in an attenuated form2 but perhaps #ajj miles high would be a fair estimate of the height to which our atmosphere extends4 ,illustration3 ,fig4 #de4--,weighing the air4 ,the pressure of such an enormous body of gas is very great4 ,it has been estimated that this pressure on the average human body amounts to fourteen tons1 but being balanced by elastic fluids in the body1 the inconvenience is not felt4 ,the ,weight of ,air can easily be ascertained1 though till the middle of the seventeenth century the air was believed to be without weight4 ,the accompanying illustration will prove the weight of air4 ,take an ordinary balance2 and suspend to one side a glass globe fitted with a stop-cock4 ,from this globe extract the air by means of the air-pump1 and weigh it4 ,when the exact weight is ascertained turn the stop-cock1 the air will rush in1 and the globe will then pull down the balance1 thus proving that air possesses weight4 ,the experiments of ,torricelli and ,otto von ,guerike1 however1 demonstrated that the air has weight and great pressure4 ,torricelli practically invented the barometer1 but ,otto von ,guerike1 by the cups known as ,magdeburg ,hemispheres1 proved the pressure of the outward air4 ,this apparatus is well known1 and consists of two hollow copper hemispheres which fit very closely4 ,by means of the air-pump which he invented in #afej1 ,otto von ,guerike exhausted the air from the closed hemispheres4 ,so long as air remained in them1 there was no great difficulty in separating them2 but when it had been finally exhausted1 the pressure of the surrounding atmosphere was so great that the hollow spheres could not be dragged asunder even by horses harnessed to rings which had been inserted in the globes4 ,illustration3 ,fig4 #df4--,magdeburg ,hemispheres4 ,the ,air-,pump is a very useful machine1 and we will now briefly explain its action4 ,the inventor was1 as remarked above1 ,otto von ,guerike1 of ,magdeburg4 ,the pump consists of a cylinder and piston and rod1 with two valves opening upwards--one valve being in the bottom of the cylinder1 the other in the piston4 ,this pump is attached by a tube to a plate with a hole in it1 one extremity of the tube being fixed in the centre of the plate1 and the other at the valve at the bottom of the cylinder4 ,a glass shade1 called the receiver1 is placed on the top of the plate1 and of course this shade will be full of air 7fig4 #dg74 ,illustration3 ,fig4 #dg4--,the air-pump4 ,when the receiver is in position1 we begin to work the pump4 ,we have said there are two valves4 ,so when the piston is drawn up1 the cylinder would be quite empty did not the valve at the bottom1 opening upwards1 admit some air from the glass shade through the tube to enter the cylinder4 ,now the lower part of the cylinder is full of air drawn from the glass shade4 ,when we press the piston down again1 we press against the air in it1 which1 being compressed1 tries to escape4 ,it cannot go back1 because the valve at the bottom of the cylinder won't open1 so it escapes by the valve in the piston1 and goes away4 ,thus a certain amount of air is got rid of at each stroke of the piston4 ,two cylinders and pistons can be used1 and so by means of cog-wheels1 etc41 the air may be rapidly exhausted from the receiver4 ,many experiments are made with the assistance of the air-pump and receiver1 though the air is never entirely exhausted from the glass4 ,the 8,sprengel0 air-pump is used to create an almost perfect vacuum1 by putting a vessel to be exhausted in connection with the vacuum at the top of a tube of mercury thirty inches high4 ,some air will bubble out1 and the mercury will fall4 ,by filling up again and repeating the process1 the air vessel will in time be completely exhausted4 ,this is done by ,mr4 ,sprengel's pump1 and a practically perfect vacuum is obtained1 like the ,torricellian vacuum4 ,the 8,torricellian vacuum0 is the empty space above the column of mercury in the barometer which we will proceed to describe4 ,air has a certain weight or pressure which is sufficient to raise a column of mercury thirty inches4 ,we will prove this by illustration4 ,take a bent tube and fill it with mercury2 the liquid will stand equally high in both arms1 in consequence of the ratio of equilibrium in fluids1 of which we shall read more when we come to consider ,water4 ,so the two columns of mercury are in equilibrium4 7,see ,a47 ,now stop the arm a with a cork1 and take out half the mercury4 ,it will remain in one arm only4 ,remove the cork1 and the fluid will fall in both arms1 and remain in equilibrio4 ,if a long bent glass tube be used1 the arms being thirty-six inches high1 the mercury will fall to a point c1 which measures #bii inches from the bottom4 ,if the tube be a square inch in bore1 we have #bii cubic inches of mercury1 weighing #ad lbs41 balancing a column of air one square inch thick and as high as the atmosphere4 ,so the mercury and the column of air must weigh the same4 ,thus every square inch on the earth supports a weight of 7nearly7 #ae lbs 7figs4 #dh and #ej74 ,illustration3 ,fig4 #dh4--;,air ,pressure4 ,illustration3 ,fig4 #di4--,the ,barometer4 ,the barometer invented by ,pascal1 working on the investigations of ,torricelli1 is a very simple and useful instrument4 ,fill a tube with mercury from which all moisture has been expelled1 and turn it over in a dish of mercury2 the mercury will rise to a certain height 7#cj inches71 and no higher in vacuo4 ,when the pressure of the air increases the mercury rises a little1 and falls when the pressure is removed4 ,air charged with aqueous vapour is lighter than dry air1 so a fall in the mercury indicates a certain amount of water-vapour in the air1 which may condense and become rain4 ,the action of mercury is therefore used as a weather-glass1 by which an index-point shows the movements of the fluid1 by means of a wheel over which a thread passes1 sustaining a float and a counterpoise4 ,when the mercury rises the float goes up1 and the weight falls1 and turns the wheel by means of the thread4 ,the wheel having a pointer on the dial tells us how the mercury moves4 ,this weather-glass is the usual syphon barometer with the float on the surface and a weight 7fig4 #ej74 ,illustration3 ,fig4 #ej4--,syphon barometer4 ,the ,syphon ,barometer is a bent tube like the one already shown1 with one limb much shorter than the other4 ,the ,aneroid ,barometer1 so called because it is 8without moisture10 is now in common use4 ,in these instruments the atmospheric pressure is held in equilibrium by an elastic metal spring or tube4 ,a metal box1 or tube1 is freed from air1 and then hermetically sealed4 ,this box has a flexible side1 the elasticity of which1 and the pressure of the air on it1 keep each other in equilibrium4 ,upon this elastic side the short arm of a lever is pressed1 while the longer arm works an index-point1 as in the circular barometer4 ,when pressure increases the elastic box 8gives02 when pressure diminishes it returns to its former place1 and the index moves in the opposite direction4 ,it is necessary to compare and 8set0 the aneroid with the mercurial barometer to ensure correctness4 ,a curved tube is sometimes used1 which coils and uncoils like a spring1 according to the pressure on it4 ,illustration3 ,fig4 #ea4--,the ,water ,barometer4 ,there are other barometers1 such as the ,water ,barometer1 which can be fixed against the side of a house1 and if the water be coloured1 it will prove a useful indicator4 ,as the name indicates1 water is used instead of mercury1 but as the latter is thirteen-and-half times heavier than water1 a much longer tube is necessary2 viz41 one about thirty-five feet in length4 ,the construction is easy enough4 ,a leaden pipe can be fixed against the house2 on the top is a funnel furnished with a stop-cock1 and placed in a vase of water4 ,the lower part of the tube is bent1 and a glass cylinder attached1 with another stop-cock--the glass being about three feet long1 and graduated4 ,fill the tube with water1 shut the upper stop-cock1 and open the lower one4 ,the vacuum will be formed in the top of the tube1 and the barometer will act on a larger scale than the mercury4 ,the ,glycerine ,barometer1 invented by ,mr4 ,jordan1 and in use at the ,times office1 registers as more than one inch movements which on the mercurial thermometer are only one-tenth of an inch1 and so are very distinctly visible4 ,the specific gravity of pure glycerine is less than one-tenth that of mercury1 so the mean height of the glycerine column is twenty-seven feet at sea level4 ,the glycerine has1 however1 a tendency to absorb moisture from the air1 but ,mr4 ,jordan1 by putting some petroleum oil upon the glycerine1 neutralized that tendency1 and the atmospheric pressure remains the same4 ,a full description of this instrument was given in the ,times of #beth ,october1 #ahhj4 ,illustration3 ,fig4 #eb4--,the principle of the diving-bell4 ,the uses of the barometer are various4 ,it is employed to calculate the heights of mountains2 for if a barometer at sea level stand at #cj1 it will be lower on a mountain top1 because the amount of air at an elevation of ten thousand feet is less than at the level of the sea1 and consequently exercises less pressure1 and the mercury descends4 ,the pressure is on the bulb of mercury at the bottom1 not on the top1 remember4 ,the pressure of the air at the tops of mountains sometimes decreases very much1 and it is not sufficiently dense for perfect respiration1 as many people find4 ,some climbers suffer from bleeding at the nose1 etc41 at great altitudes4 ,this is occasioned by the action of the heart1 which pumps with great force1 and the outward pressure upon the little veins being so much less than usual1 they give way4 ,illustration3 ,fig4 #ec4--;,diver under water4 ,many important instruments depend upon atmospheric pressure4 ,the most important of these is the pump1 which will carry us to the consideration of water and ,,fluids generally4 ,the fire-engine is another example1 but we will now proceed to explain the diving-bell already referred to4 ,fig4 #eb represents the experiment of the diving-bell1 which is so simple1 and is explained below4 ,it belongs to the same category of experiments as those relating to the pressure of air and compression of gas4 ,two or three flies have been introduced into the glass1 and they prove by their buzzing about that they are quite at their ease in the rather confined space4 ,the ,,diving-,,bell in a crude form appears to have been used as early as #aech4 ,it was used by two ,greeks in the presence of the ,emperor ,charles ,v41 and numerous spectators4 ,in the year #agbj ,doctor ,halley improved the diving-bell1 which was a wooden box or chamber open at the bottom4 ,air casks were used to keep the inmate supplied with air4 ,the modern diving-bell was used by ,smeaton in #aghh1 and was made of cast iron4 ,it sinks by its own weight4 ,the pressure of the air inside is sufficient to keep the water out4 ,air being easily compressed1 it is always pumped in to keep the hollow iron 8bell0 full1 and to supply the workmen4 ,there are inventions now in use by which the diver carries a supply of air with him on his back1 and by turning a tap can supply himself for a long time at a distance from the place of descent1 and thus is able to dispense with the air-tube from the boat at the surface4 ,this apparatus was exhibited at the ,crystal ,palace some years ago4 ,illustration3 ,fig4 #ed4--,the ,hand ,fire-,engine4 ,,the ,,pump4 ,we have seen in the case of the ,water ,barometer that the pressure of the air will sustain a column of water about thirty feet high4 ,so the distance between the lower valve and the reservoir or cistern must not be more than thirty-two feet1 practically the distance is about twenty-five feet in pumps4 ,we can see by the illustration that the working is much the same as in the air-pump4 ,the suction pipe ,b is closed by the valve ,c1 the cylinder ,d and spout ,e are above1 the piston rod ,f lifts the air-tight piston in which is a valve ,h4 ,when the piston is raised the valve ,c opens and admits the water into the cylinder4 ,when the piston is depressed the valve ,c is closed1 the water already in forces ,h open1 and passing through the piston1 reaches the cylinder and the spout 7fig4 #ee74 ,the hand fire-engine depends upon the action of compressed air1 which is so compressed by pumping water into the air chamber a4 ,the tube is closed at g1 and the pumps e e drive water into the air chamber4 ,at length the tap is opened1 and the air drives the water out as it is continually supplied 7fig4 #ed74 ,compressed air was also used for driving the boring machines in the ,mount ,cenis tunnel4 ,in this case also the air was compressed by water1 and then let loose1 like steam1 to drive a machine furnished with boring instruments4 ,a pretty little toy may be made1 and at the same time exemplify an interesting fact in ,physics4 ,it is called the ludion1 and it 8lies in a nut shell0 in every sense4 ,when the kernel has been extracted from the shell1 fasten the portions together with sealing wax1 so that no water can enter4 ,at one end ,o1 as in the illustration1 leave a small hole about as large as a pin's head2 fasten two threads to the sealing wax1 and to the threads a wooden doll4 ,let a weight be attached to his waist4 ,when the figure is in equilibrium1 and will float1 put it into a jar of water1 and tie a piece of bladder over the top4 ,if this covering be pressed with the finger1 the doll will descend and remount when the finger is removed4 ,by quick successive pressure the figure may be made to execute a pas seul4 ,the reason of the movement is because the slight cushion of air in the upper part of the vase is compressed1 and the little water thus caused to enter the nut shell makes it heavier1 and it descends with the figure 7fig4 #ef74 ,illustration3 ,fig4 #ee4--,the ,pump4 ,we have now seen that air is a gas1 that it exercises pressure1 that it possesses weight4 ,we know it can be applied to many useful purposes1 and that the air machines and inventions--such as the air-pump and the 8,pneumatic ,despatch0--are in daily use in our laboratories1 our steam engines1 our condensed milk manufactories1 and in many other industries1 and for our social benefit4 ,compressed air is a powerful motor for boring machinery in tunnels where steam cannot be used1 even if water could be supplied1 for smoke or fire would suffocate the workers4 ,to air we owe our life and our happiness on earth4 ,pneumatics1 then1 deals with the mechanical properties of elastic fluids represented by air4 ,a gas is an elastic fluid1 and differs very considerably1 from water2 for a gas will fill a large or small space with equal convenience1 like the genii which came out of the bottle and obligingly retired into it again to please the fisherman4 ,we have seen that the pressure of the air is #ad per square inch at a temperature of #cb4 ,it is not so easy to determine the pressure of air at various times as that of water4 ,we can always tell the pressure of a column of water when we find the height of the column1 as it is the weight of so many cubic inches of the liquid4 ,but the pressure of the atmosphere per square inch at any point is equal to the weight of a vertical column of air one inch square1 reaching from that point to the limit of the atmosphere above it4 ,still the density is not the same at all points1 so we have to calculate4 ,the average pressure at sea level is #adg per square inch1 and sustains a column of mercury #a square inch in thickness1 #biib1 or say #cj inches high4 ,these are the data upon which the barometer is based1 as we have seen4 ,illustration3 ,fig3 #ef4--,the 8,ludion40 ,in our article upon 8,chemistry0 we will speak more fully of the atmosphere and of its constituents1 etc4 ,,chapter ,,vi4 ,,about ,,water--,,hydrostatics ,,and ,,hydraulics--,,law ,,of ,,archimedes--,,the ,,bramah ,,press--,,the ,,syphon4 ,at present we will pass from ,air to ,water1 from ,pneumatics to ,hydrostatics and ,hydraulics4 ,we must remember that ,hydrostatics and ,hydraulics are very different4 ,the former treats of the weight and pressure of liquids when they are at rest1 the latter treats of them in motion4 ,we will now speak of the properties of ,liquids1 of which ,water may be taken as the most familiar example4 ,we have already seen that ,matter exists in the form of ,solids1 ,liquids1 and ,gases1 and of course ,water is one form of ,matter4 ,it occupies a certain space1 is slightly compressible2 it possesses weight1 and exercises force when in motion4 ,it is a fluid1 but also a liquid4 ,there are fluids not liquid1 such as air or steam1 to take equally familiar examples4 ,these are elastic fluids and compressible1 while water is inelastic1 and termed incompressible4 ,the chemical composition of water will be considered hereafter1 but at present we may state that water is composed of oxygen and hydrogen1 and proportions of eight of the former to one of the latter by weight2 in volume the hydrogen is as two to one4 ,from these facts1 as regards water1 we learn that volume and weight are very different things1--that equal volumes of various things may have different weights1 and that volume 7or bulk7 by no means indicates weight ,equal volumes of feathers and sand will weigh very differently4 ,the old 8catch0 question of the 8difference in weight between a pound of lead and a pound of feathers0 here comes to the mind4 ,the answer generally given is that 8feathers make the heavier #8pound' because they are weighed by avoirdupois1 and lead by troy weight40 ,this is an error4 ,they are both weighed in the same way1 and pound for pound are the same weight1 though different in volume4 ,fluids in equilibrium have all their particles at the same distance from the centre of the earth1 and although within small distances liquids appear perfectly level 7in a direct line71 they must1 as the sea does1 conform to the shape of the earth1 though in small levels the space is too limited to admit of any deviation from the plane at right angle to the direction of gravity4 ,liquids always fall to a perfectly level surface1 and water will seek to find its original level1 whether it be in one side of a bent tube1 in a watering pot and its spout1 or as a fountain4 ,the surface of the water will be on the same level in the arms of a bent tube1 and the fountain will rise to a height corresponding with the elevation of the parent spring whence it issues4 ,the waterworks companies first pump the water to a high reservoir1 and then it rises equally high in our high-level cisterns4 ,as an example of the force of water1 a pretty little experiment may be easily tried1 and1 as many of our readers have seen in a shop in the ,strand in ,london1 it always is attractive4 ,a good-sized glass shade should be procured and placed over a water tap and basin1 as per the illustration herewith4 ,within the glass put a number of balls of cork or other light material4 ,let a stop-cock1 with a small aperture1 be fixed upon the tube leading into the glass4 ,another tube to carry away the water should1 of course1 be provided1 but it may be used over again4 ,when the tap is properly fixed1 if the pressure of the water be sufficient1 it will rush out with some force1 and catching the balls as they fall to the bottom of the glass shade bear them up as a juggler would throw oranges from hand to hand4 ,if coloured balls be used the effect may be enhanced1 and much variety imparted to the experiment1 which is very easy to make4 ,illustration3 ,fig4 #eg4--,water jet and balls4 ,water exercises an enormous pressure1 but the pressure does not depend upon the amount of water in the vessel4 ,it depends upon the vessel's height1 and the dimensions of the base4 ,this has been proved by filling vessels whose bases and heights are equal1 but whose shapes are different1 each holding a different quantity of water4 ,the pressure at the bottom of each vessel is the same1 and depends upon the depth of the water4 ,if we subject a portion of the liquid surface to certain force1 this pressure will be dispersed equally in all directions1 and from an acquaintance with this fact the ,hydraulic ,press was brought into notice4 ,if a vessel with a horizontal bottom be filled with water to a depth of one foot1 every square foot will sustain a pressure of #fbcg lbs41 and each square inch of #jdcc lbs4 ,illustration3 ,figs4 #eh1 #ei1 #fj1 #fa4--,pressure of ,water4 ,we will now explain the principle of this ,,water ,,press4 ,in the small diagram1 the letters ,a ,b represent the bottom of a cylinder which has a piston fitted in it 7,p74 ,into the opposite side a pipe is let in1 which leads from a force-pump ,d1 which is fitted with a valve ,e1 opening upwards4 ,when the piston in ,d is pulled up water enters through the valve2 when the piston is forced down the valve shuts1 and the water rushes into the chamber ,a ,b4 ,the pressure pushes up the large piston with a force multiplied as many times as the area of the small piston is contained in the large one4 ,so if the large one be ten times as great as the small one1 and the latter be forced down with a #aj lb4 pressure1 the pressure on the large one will be #ajj lbs41 and so on4 ,illustration3 ,fig4 #fb4--,water ,press4 ,the accompanying illustration shows the form of the ,hydraulic or ,bramah ,press4 ,a ,b ,c ,d is a strong frame1 ,f the force-pump worked by means of a lever fixed at ,g1 and ,h is the counterprise4 ,e is the stop-cock to admit the water 7fig4 #fc74 ,illustration3 ,fig4 #fc4--;,bramah ,press4 ,the principles of hydrostatics will be easily explained4 ,the ,lectures of ,m4 ,aim ,schuster1 ,professor and ,librarian at ,metz1 have taught us in a very simple manner the principle of ,archimedes1 in which it is laid down that 8a body immersed in a liquid loses a portion of its weight equal to the weight of the liquid displaced by it40 ,we take a body of as irregular form as we please2 a stone1 for example4 ,a thread is attached to the stone1 and it is then placed in a glass of water full up to the brim4 ,the water overflows2 a volume of the liquid equal to that of the stone runs over4 ,the glass thus partially emptied is then dried1 and placed on the scale of a balance1 beneath which we suspend the stone2 equilibrium is established by placing some pieces of lead in the other scale4 ,we then take a vase full of water1 into which we plunge the stone suspended from the scale1 supporting the vase by means of bricks4 ,the equilibrium is now broken2 to re-establish it1 it is necessary to fill up with water the glass placed on the scale2 that is to say1 we put back in the glass the weight of a volume of water precisely equal to that of the stone4 ,illustration3 ,fig4 #fd4--;,demonstration of the upward pressure of liquids4 ,if it is desired to investigate the principles relating to connected vessels1 springs of water1 artesian wells1 etc41 two funnels1 connected by means of an india-rubber tube of certain length1 will serve for the demonstration2 and by placing the first funnel at a higher level1 and pouring in water abundantly1 we shall see that it overflows from the second4 ,a disc of cardboard and a lamp-glass will be all that is required to show the upward pressure of liquids4 ,i apply to the opening of the lamp-glass a round piece of cardboard1 which ,i hold in place by means of a string2 the tube thus closed ,i plunge into a vessel filled with water4 ,the piece of cardboard is held by the pressure of the water upwards4 ,to separate it from the opening it suffices to pour some water into the tube up to the level of the water outside 7fig4 #fd74 ,the outer pressure exercised on the disc1 as well as the pressure beneath1 is now equal to the weight of a body of water having for its base the surface of the opening of the tube1 its depth being the distance from the cardboard to the level of the water4 ,syringes1 pumps1 etc41 are the effects of atmospheric pressure4 ,balloons rise in the air by means of the pressure of gas2 a balloon being a body plunged in gas1 is consequently submitted to the same laws as a body plunged in water4 ,boats float because of the pressure of liquid1 and water spurts from a fountain for the same reason4 ,i recollect having read a very useful application of the principles of fluid pressure4 ,illustration3 ,fig #fe4--;,experiment on the convexity of a meniscus4 ,a horse was laden with two tubs for carrying a supply of water1 and in the bottom of the tubs a valve was fixed4 ,when the horse entered the stream the tubs were partly immersed2 the water then exercised its upward pressure1 the valve opened1 and the tubs slowly filled4 ,when they were nearly full the horse turned round and came out of the water2 the pressure had ceased4 ,thus the action of the water first opened the valve1 and then closed it4 ,the particular phenomena observable in the water level in narrow spaces1 as of a fine glass tube1 or the level of two adjoining waves1 capillary phenomena1 etc41 do not need any special appliance for demonstration1 and it is the same with the convexity or concavity of meniscuses4 ,fig4 #fe represents a pretty experiment in connection with these phenomena4 ,i take a glass1 which ,i fill up to the brim1 taking care that the meniscus be concave1 and near it ,i place a pile of pennies4 ,i then ask my young friends how many pennies can be thrown into the glass without the water overflowing4 ,everyone who is not familiar with the experiment will answer that it will only be possible to put in one or two1 whereas it is possible to put in a considerable number1 even ten or twelve4 ,as the pennies are carefully and slowly dropped in1 the surface of the liquid will be seen to become more and more convex1 and one is surprised to what an extent this convexity increases before the water overflows4 ,the common syphon may be mentioned here4 ,it consists of a bent tube with limbs of unequal length4 ,we give an illustration of the syphon 7fig4 #ff74 ,the shorter leg being put into the mixture1 the air is exhausted from the tube at o1 the aperture at g being closed with the finger4 ,when the finger is removed the liquid will run out4 ,if the water were equally high in both legs the pressure of the atmosphere would hold the fluid in equilibrium1 but one leg being longer1 the column of water in it preponderates1 and as it falls1 the pressure on the water in the vessel keeps up the supply4 ,illustration3 ,fig4 #ff4--,the ,syphon4 ,apropos of the syphon1 we may mention a very simple application of the principle4 ,cut off a strip of cloth1 and arrange it so that one end shall remain in a glass of water while the other hangs down1 as in the illustration4 ,in a short time the water from the upper glass will have passed through the cloth-fibres to the lower one 7fig4 #fg74 ,this attribute of porous substances is called capillarity1 and shows itself by capillary attraction in very fine pores or tubes4 ,the same phenomenon is exhibited in blotting paper1 sugar1 wood1 sand1 and lamp-wicks1 all of which give familiar instances of capillarity4 ,the cook makes use of this property by using thin paper to absorb grease from the surface of soups4 ,capillarity 7referred to on page #be7 is the term used to define capillary force1 and is derived from the word capillus1 a hair2 and so very small bore tubes are called capillary tubes4 ,we know that when we plunge a glass tube into water the liquid will rise up in it1 and the narrower the tube the higher the water will go2 moreover1 the water inside will be higher than at the outside4 ,this is in accordance with a well-known law of adhesion1 which induces concave or convex surfaces#i in the liquids in the tubes1 according as the tube is wetted with the liquid or not4 ,for instance1 water1 as we have said1 will be higher in the tube1 and concave in form2 but mercury will be depressed below the outside level1 and convex1 because mercury will not adhere to glass4 ,when the force of cohesion to the sides of the tube is more than twice as great as the adhesion of the particles of the liquid1 it will rise up the sides1 and if the forces be reversed1 the rounded appearance will follow4 ,this accounts for the convex appearance1 or 8meniscus10 in the column of mercury in a barometer4 ,amongst the complicated experiments to demonstrate molecular attraction1 the following is very simple and very pretty3--,take two small balls of cork1 and having placed them in a basin half-filled with water1 let them come close to each other4 ,when they have approached within a certain distance they will rush together4 ,if you fix one of them on the blade of your penknife1 it will attract the other as a magnet1 so that you can lead it round the basin 7fig4 #fh74 ,but if the balls of cork are covered with grease they will repel each other1 which fact is accounted for by the form of the menisques1 which are convex or concave1 according as they are moistened1 or preserved from action of the water by the grease4 ,illustration3 ,fig4 #fg4--;,an improvised syphon4 ,this attribute is of great use in the animal and vegetable kingdoms4 ,the rising of the sap is one instance of the latter4 ,experience in hydrostatics can be easily applied to amusing little experiments4 ,for instance1 as regards the syphon1 we may make an image of ,tantalus as per illustration 7fig4 #fi74 ,a wooden figure may be cut in a stooping posture1 and placed in the centre of a wide vase1 as if about to drink4 ,if water be poured slowly into the vase it will never rise to the mouth of the figure1 and the unhappy ,tantalus will remain in expectancy4 ,this result is obtained by the aid of a syphon hidden in the figure1 the shorter limb of which is in the chest4 ,the longer limb descends through a hole in the table1 and carries off the water4 ,these vases are called vases of ,tantalus4 ,the principle of the syphon may also be adapted to our domestic filters4 ,charcoal1 as we know1 makes an excellent filter1 and if we have a block of charcoal in one of those filters1--now so common1--we can fix a tube into it1 and clear any water we may require4 ,it sometimes 7in the country7 happens that drinking-water may become turgid1 and in such a case the syphon filter will be found useful4 ,illustration3 ,fig4 #fh4--,molecular attraction4 ,the old 8deception0 jugs have often puzzled people4 ,we give an illustration of one1 and also a sketch of the 8deceptive0 portion 7figs4 #gj and #ga74 ,this deception is very well managed1 and will create much amusement if a jug can be procured2 they were fashionable in the eighteenth century1 and previously4 ,a cursory inspection of these curious utensils will lead one to vote them utterly useless4 ,they are1 however1 very quaint1 and if not exactly useful are ornamental4 ,they are so constructed1 that if an inexperienced person wish to pour out the wine or water contained in them1 the liquid will run out through the holes cut in the jug4 ,to use them with safety it is necessary to put the spout ,a in one's mouth1 and close the opening ,b with the finger1 and then by drawing in the breath1 cause the water to mount to the lips by the tube which runs around the jug4 ,the specimens herein delineated have been copied from some now existent in the museum of the ,svres china manufactory4 ,the ,buoyancy of ,water is a very interesting subject1 and a great deal may be written respecting it4 ,the swimmer will tell us that it is easier to float in salt water than in fresh4 ,he knows by experience how difficult it is to sink in the sea2 and yet hundreds of people are drowned in the water1 which1 if they permitted it to exercise its power of buoyancy1 would help to save life4 ,illustration3 ,fig4 #fi4--,vase of ,tantalus4 ,the sea-water holds a considerable quantity of salt in solution1 and this adds to its resistance1 or floating power4 ,it is heavier than fresh water1 and the ,dead ,sea is so salt that a man cannot possibly sink in it4 ,this means that the man's body1 bulk for bulk1 is much lighter than the water of the ,dead ,sea4 ,a man will sink in fresh1 or ordinary salt water if the air in his lungs be exhausted1 because without the air he is much heavier than water1 bulk for bulk4 ,so if anything is weighed in water1 it apparently loses in weight exactly equal to its own bulk of water4 ,water is the means by which the ,specific ,gravity of liquids or solids is found1 and by it we can determine the relative densities of matter in proportion4 ,air is the standard for gases and vapours4 ,let us examine this1 and see what is meant by ,,specific ,,gravity4 ,we have already mentioned the difference existing between two equal volumes of different substances1 and their weight1 which proves that they may contain a different number of atoms in the same space4 ,we also know1 from the principle of ,archimedes1 that if a body be immersed in a fluid1 a portion of its weight will be sustained by the fluid equal to the weight of the fluid displaced4 ,illustration3 ,fig4 #gj4--;,deception jugs of old pattern4 ,this theorem is easily proved by filling a bucket with water1 and moving it about in water1 when it will be easy to lift2 and likewise the human body may be easily sustained in water by a finger under the chin4 ,the manner in which ,archimedes discovered the displacement of liquids is well known1 but is always interesting4 ,king ,hiero1 of ,syracuse1 ordered a crown of gold to be made1 and when it had been completed and delivered to ,his ,majesty1 he had his doubts about the honesty of the goldsmith1 and called to ,archimedes to tell him whether or not the crown was of gold1 pure and simple4 ,archimedes was puzzled1 and went home deep in thought4 ,still considering the problem he went to the bath1 and in his abstraction filled it to the brim4 ,stepping in he spilt a considerable quantity of water1 and at once the idea struck him that any body put into water would displace its own weight of the liquid4 ,he did not wait to dress1 but ran half-naked to the palace1 crying out1 8,eureka1 ,eureka6 ,i have found it1 ,i have found it6 8,what had he found8--,he had solved the problem4 ,illustration3 ,fig4 #ga4--,section of jug4 ,he got a lump of gold the same weight as the crown1 and immersed it in water4 ,he found it weighed nineteen times as much as its own bulk of water4 ,but when he weighed the kings crown he found it displaced more water than the pure gold had done1 and consequently it had been adulterated by a lighter metal4 ,he assumed that the alloy was silver1 and by immersing lumps of silver and gold of equal weight with the crown1 and weighing the water that overflowed from each dip1 he was able to tell the king how far he had been cheated by the goldsmith4 ,it is by this method now that we can ascertain the specific gravity of bodies4 ,one cubic inch of water weighs about half an ounce 7or to be exact1 #beb grains74 ,take a piece of lead and weigh it in air2 it weighs1 say1 eleven ounces4 ,then weigh it in a vase of water1 and it will be only ten ounces in weight4 ,so lead is eleven times heavier than water1 or eleven ounces of lead occupy the same space as one ounce of water4 ,illustration3 ,fig4 #gb4--,weighing metal in water4 ,the heavier a fluid is1 or the greater its density1 the greater will be the weight it will support4 ,therefore we can ascertain the purity or otherwise of certain liquids by using hydrometers1 etc41 which will float higher or lower in different liquids1 and being gauged at the standard of purity1 we can ascertain 7for instance7 how much water is in the milk when supplied from the dairy4 ,illustration3 ,fig4 #gc4--;,hydrometer4 ,but to return to ,,specific ,,gravity1 which means the 8,comparative density of any substance relatively to water10 or as ,professor ,huxley says1 8,the weight of a volume of any liquid or solid in proportion to the weight of the same volume of water1 at a known temperature and pressure40 ,water1 therefore1 is taken as the unit2 so anything whose equal volume under the same circumstances is twice as heavy as the water1 is declared to have its specific gravity #b2 if three-and-a-half times it is #ce1 and so on4 ,we append a few examples2 so we see that things which possess a higher specific gravity than water sink1 which comes to the same thing as saying they are heavier than water1 and vice vers4 ,to find the specific gravity of any solid body proceed as above1 in the experiment of the lead4 ,by weighing the substance in and out of water we find the weight of the water displaced2 that is1 the first weight less the second4 ,divide the weight in air by the remainder1 and we shall find the specific gravity of the substance4 ,illustration3 ,fig4 #gd4--,over-shot wheel of mill4 ,the following is a table of specific gravities of some very different substances1 taking water as the unit4 ---------------------------------------- ---------------------- ,substance4 ,specific ,substance4 ,specific ,substance4 ,specific ,gravity4 ,gravity4 ,gravity4 ---------------------------------------- ---------------------- ,platinum #bae ,iron #ggi ,water #ajjj ,gold #aie ,tin #gbi ,sea ,water #ajbf ,mercury #acei ,granite #bfb ,rain ,water #ajja ,lead #aade ,oak ,wood #jgg ,ice #iaf ,silver #ajej ,cork #jbd ,ether #jgbc ,copper #hif ,milk #ajcb ,alcohol #jgic ---------------------------------------- ---------------------- ,but we have by no means exhausted the uses of water4 ,hydrodynamics1 which is the alternative term for hydraulics1 includes the consideration of many forms of water-wheels1 most of which1 as mill-wheels1 are under-shot1 or over-shot accordingly as the water passes horizontally over the floats1 or acts beneath them4 ,these wheels are used in relation to the fall of water4 ,if there is plenty of water and a slight fall1 the under-shot wheel is used4 ,if there is a good fall less water will suffice1 as the weight and momentum of the falling liquid upon the paddles will turn the wheel4 ,here is the ,persian water-wheel1 used for irrigation 7fig4 #ge74 ,the ,archimedian ,screw1 called after its inventor1 was one of the earliest modes of raising water4 ,it consists of a cylinder somewhat inclined1 and a tube bent like a screw within it4 ,by turning the handle of the screw the water is drawn up and flows out from the top4 ,illustration3 ,fig4 #ge4--;,irrigation wheel in ,egypt4 ,the ,water ,ram is a machine used for raising water to a great height by means of the momentum of falling water4 ,the ,hydraulic ,lift is familiar to us all1 as it acts in our hotels1 and we need only mention these appliances here2 full descriptions will be found in ,cyclopdias4 ,we have by no means exhausted the subject of ,water in this chapter4 ,far from it4 ,but when we come to ,chemistry and ,physical ,geography we shall have more to tell1 and our remarks as to the application of science to ,domestic ,economy1 in accordance with our plan1 will also lead us up to some of the uses of water4 ,so for the present we will take our leave of water in a liquid form1 and meet it again under the application of ,heat1 which subject will take us to ,ice and ,steam1--two very different conditions of water4 ,,footnotes3 #i ,the curved surface of a column of liquid is termed a 8meniscus10 from the ,greek word meniskos1 meaning 8a little lens40 ,,chapter ,,vii4 ,,heat--,,what ,,it ,,is--,,theory ,,of ,,heat--,,the ,,thermometer--,,expansion ,,by ,,heat--,,ebullition ,,and ,,distillation--,,latent ,,heat--,,specific ,,heat4 ,what is ,heat8--,we will consider this question1 and endeavour to explain it before we speak of its effects on water and other matter4 ,heat is now believed to be the effects of the rapid motion of all the particles of a body4 ,it is quite certain that a heated body is no heavier than the same body before it was made 8hot10 so the heat could not have gone into it1 nor does the 8heat0 leave it when it has become what we call 8cold10 which is a relative term4 ,heat is therefore believed to be a vibratory motion1 or the effects of very rapid motion of matter4 ,the ,science of ,heat1 as we may term it1 is only in its infancy1 or certainly has scarcely come of age4 ,formerly heat was considered a chemical agent1 and was termed caloric1 but now heat is found to be motion1 which affects our nerves of feeling and sight2 and1 as ,professor ,stewart tells us1 8a heated body gives a series of blows to the medium around it2 and although these blows do not affect the ear1 they affect the eye1 and give us a sense of light40 ,although it is only within a comparatively few years that heat has been really looked upon as other than matter1 many ancient philosophers regarded it as merely a quality of matter4 ,they thought it the active principle of the universe4 ,epicurus declared that heat was an effluxion of minute spherical particles possessing rapid motion1 and ,lucretius maintained that the sun's light and heat are the result of motion of primary particles4 ,fire was worshipped as the active agent of the universe1 and ,prometheus was fabled to have stolen fire from heaven to vivify mankind4 ,the views of the ancients were more or less adopted in the ,middle ,ages2 but ,john ,locke recognized the theory of heat being a motion of matter4 ,he says3 8,what in our sensation is heat1 in the object is nothing but motion40 ,gradually two theories arose concerning heat2--one1 the ,material theory--the theory of ,caloric or ,phlogiston2 the other1 the ,kinetic theory4 ,before the beginning of the present century the former theory was generally accepted1 and the development of heat was accounted for by asserting that the friction or percussion altered the capacity for heat of the substances acted upon4 ,the heat was squeezed out by the hammer1 and the amount of heat in the world was regarded as a certain quantity1 which passed from one body to another1 and that some substances contained1 or could 8store away10 more of the material called heat than other substances4 ,heat was the material of fire--the principle of it1 or materia ignis2 and by these theories ,heat1 or ,caloric1 was gradually adopted as a separate material agent--an invisible and subtle matter producing certain phenomena when liberated4 ,so the two theories concerning heat arose at the end of the last century4 ,one1 as we have said1 is known as the ,material1 the other as the ,kinetic theory4 ,the latter is the theory of motion1 so called from the ,greek kinesis 7motion71 or sometimes known as the ,dynamic theory of heat1 from dunamis 7force72 or again as ,thermo-dynamics4 ,but any possibility of producing a new supply of heat was denied by the materialists4 ,they knew that some bodies possessed a greater capacity for heat than others2 but ,count ,rumford1 at ,munich1 in #agig1 astonished an audience by making water boil without any fire6 ,he had observed the great extent to which a cannon became heated while being bored in the gun factory1 and influenced by those who maintained the material theory of heat1 paid great attention to the evolution of heat4 ,he accordingly endeavoured to produce heat by friction1 and by means of horse power he caused a steel borer to work upon a cylinder of metal4 ,the shavings were permitted to drop into a pan of water at #fj ,fahrenheit4 ,in an hour after the commencement of the operation the temperature of the water had risen to #ajg3 in another half-hour the heat of it was up to #adb3 and in two hours had measured #agj4 ,upon this he says3 8,it is hardly necessary to add that anything which any insulated body or system of bodies can continue to furnish without limitation cannot possibly be a material substance1 and it appears to me to be extremely difficult1 if not quite impossible1 to form any distinct idea of anything capable of being excited and communicated in these experiments except by motion40 ,a few years later ,sir ,humphrey ,davy made his conclusive experiments1 and the ,material theory of heat received its death-blow4 ,sir ,humphrey ,davy--referring to the fact that water at a freezing temperature has 8more heat in it0 7as it was believed7 than ice at the same temperature--said3 8,if ,i1 by friction1 liquify ice1 a substance will be produced which contains a far greater absolute amount of heat than ice4 ,in this case it cannot reasonably be affirmed that ,i merely render sensible heat which had been previously insensible in the frozen mass4 ,liquification will conclusively prove the generation of heat4 ,this reasoning could not be doubted4 ,sir ,humphrey ,davy made the experiment4 ,he rubbed together two pieces of ice in the air1 and in a vacuum surrounded by a freezing mixture4 ,the ice became liquified1 and so the generation of heat by 8mechanical means0 was proved4 ,its immateriality was demonstrated1 but the ,material theory was not even then abandoned by its adherents4 ,so things continued1 until in #ahdb-c1 ,doctor ,julius ,meyer1 of ,heilbronn1 and ,doctor ,joule1 of ,manchester1 separately1 and by different means1 arrived at the conclusion that a certain definite amount of mechanical work corresponds to a certain definite amount of ,heat1 and vice vers4 ,thus was a great support afforded to the ,dynamic theory4 ,this fact ,doctor ,joule communicated to the ,philosophical ,magazine in #ahdc1 and the conclusions he came to were-- #a4 8,that the quantity of heat produced by the friction of bodies1 whether solid or liquid1 is always in proportion to the force expended2 #b4 8,that the quantity of heat capable of increasing the temperature of a pound of water 7weighed in vacuo and taken at between #ee and #fj ,fahr47 by #a ,fahr41 requires for its evolution the expenditure of a mechanical force represented by the fall of #ggb lbs4 through the space of one foot40 ,illustration3 ,fig4 #gf4--,melting a piece of tin on a card4 ,this is the 8mechanical equivalent of heat40 ,the first paper written by ,mr4 ,joule demonstrated that the temperature of water rises when forced through narrow tubes2 and to heat it one degree1 the force of #ggj foot pounds was necessary1 which means that the #a lb4 of water falling #ggj feet1 got hotter by one degree when it reached the earth4 ,he subsequently arrived at the more exact conclusions quoted above4 ,so heat is now known to be a series of vibrations1 or vibratory motions1 as sound vibrations1 which we cannot hear nor see1 but the effects of which are known to us as light and heat4 ,in considering heat we must put aside the idea of warmth and cold1 for they are only different degrees of heat1 not the absence of it4 ,the study of heat can be briefly undertaken without any complicated apparatus4 ,if we desire a proof of the great conducting power of metals1 let us place a fine piece of muslin tightly stretched over a lump of polished metal4 ,on the muslin we put a burning ember1 and excite combustion by blowing on it2 the muslin is not burned in the least1 the heat being entirely absorbed by the metal1 which draws it through the material into itself4 ,fig4 #gf represents a similar experiment3 it consists of melting some tin on a playing card1 held over the flame of a spirit lamp4 ,the metal becomes completely melted without the card being burnt4 ,it is through a similar effect that metals appear cold to us when we take them in our hands2 by their conductibility they remove the heat from our hands1 and give us the peculiar impression which we do not experience when in contact with substances that are bad conductors1 such as wood1 woollen materials1 etc4 ,illustration3 ,fig4 #gg4--;,boiling water in a paper case4 ,fig4 #gg shows the method of boiling water in paper4 ,we make a small paper box1 such as those made by school-boys1 and suspend it by four threads to a piece of wood held horizontally at a suitable height4 ,we fill this improvised vessel with water1 and place it over the flame of a spirit lamp4 ,the paper is not burnt1 because the water absorbs all the heat into itself4 ,after a few minutes the water begins to boil1 sending forth clouds of steam1 but the paper remains intact4 ,it is well to perform this operation over a plate1 in case of accident1 as the water may be spilt4 ,we may also make use of an egg-shell as a little vessel in which to heat the water1 by resting it on a wire ring over the flame of the spirit lamp4 ,illustration3 ,fig4 #gh4--;,experiment on the regelation of ice4 ,fig4 #gh shows the arrangement of a very remarkable experiment1 but little known1 on the refreezing of ice4 ,a block of ice is placed on the edge of two iron chairs1 and is encircled by a piece of wire1 to which is suspended the weight of say five pounds4 ,the wire penetrates slowly1 and in about an hour's time has passed completely through the lump of ice1 and the weight1 with the piece of wire1 falls to the ground4 ,what happens then to the block of ice8--,you imagine1 doubtless1 that it is cut in two4 ,no such thing2 it is intact1 and in a single lump as it was previous to the experiment4 ,in proportion as the wire was sunk through the mass1 the slit has been closed again by refreezing4 ,ice or snow during the winter may serve for a number of experiments relating to heat4 ,if we wish to demonstrate the influence of colours on radiation1 we take two pieces of cloth of the same size1--one white1 and the other black1--and place them both on the snow1 if possible1 when there is a gleam of sunlight4 ,in a short time it will be found that the snow underneath the black cloth has melted to a much greater extent than that beneath the white cloth1 because black absorbs heat more than white1 which1 on the contrary1 has a tendency to reflect it4 ,we perceive very plainly the difference in temperature by touching the two cloths4 ,the white cloth feels cold in comparison with the black cloth4 ,it is hardly necessary to point out experiments on the expansion of bodies4 ,they can be performed in a number of different ways2 by placing water in a narrow-necked bottle1 and warming it over the fire1 we can ascertain the expansion of liquids under the influence of heat4 ,we may in this way construct a complete thermometer4 ,we may now consider the ,sources of ,heat1 or causes of its development1 which are various1 and in many cases apparent4 ,the first great source is the ,sun1 and it has been calculated that the heat received by the earth in one year is sufficient to melt an envelope of ice surrounding it one hundred and five feet thick4 ,of course the heat at the surface of the sun is enormously greater than this1 about one-half being absorbed in the atmosphere before it reaches us at all4 ,in fact1 it is impossible to give you an idea of the enormous heat given out by the sun to the earth 7which is a very small fraction indeed of the whole71 stars1 and planets1 all of which give out heat4 ,we know that heat is stored in the earth1 and that it is in a very active condition we can perceive from the hot springs1 lava1 and flame which are continually erupting from the earth in various places4 ,these sources of heat are beyond our control4 ,but apart from the extra- and intra-terrestrial sources of heat there are mechanical causes for its generation upon our globe1 such as friction1 percussion1 or compression4 ,the savage or the woodman can procure heat and fire by rubbing a pointed stick in a grooved log4 ,the wooden 8breaks0 of a locomotive are often set on fire by friction of the wheels1 so they require grease1 and the wheels on the rails will develop heat and sparks4 ,our matches1 and many other common instances of the generation of heat 7and fire7 by friction1 will occur to every reader4 ,water may be heated by shaking it in a bottle1 taking care to wrap something round it to keep the warmth of the hand from the glass4 ,by percussion1 such as hammering a nail or piece of iron1 the solid bar may be made 8red-hot02 and when cannon are bored at ,woolwich the shavings of steel are too hot to hold even if soap-and-water has been playing upon the boring-machine4 ,the production of heat by chemical action is termed combustion1 and this is the means by which all artificial heat for our daily wants is supplied4 ,we can also produce heat by electricity4 ,a familiar and not always pleasant instance of this is seen in the flash of lightning which will fuse metals1 and experiment may do the same upon a smaller scale4 ,these are1 in brief1 the ,sources of ,heat1 and we may speak of its effects4 ,we may take it for granted that no matter from what source heat is derived1 it exhibits the same phenomena in its relation to objects4 ,one of the most usual of these phenomena is expansion4 ,let us take water1 and see the effect of heat upon it4 ,we know that a certain weight of water under the same conditions has always the same volume2 and although the attributes of the liquid vary under different circumstances1 under the same conditions its properties are exactly the same4 ,now1 water expands very much when under the influence of heat1 like all liquids2 solids and gases also expand upon the application of heat4 ,we can easily establish these statements4 ,a metallic ring when heated is larger than when cool4 ,a small quantity of air in a bladder when heated will fill the bladder1 and water will boil over the vessel1 or expand into steam1 and perhaps burst the boiler4 ,so expansion is the tendency of what we term heat4 ,we make use of this quality of heat in the thermometer1 by which we can measure the temperature not only of liquids or solids1 but of the atmosphere4 ,the reading of the thermometer varies in different countries1 for the degrees are differently marked1 but the construction of the instrument is the same4 ,it is called thermometer from two ,greek words signifying the measure of heat4 ,it is a notable fact that ,castelli1 writing in #afch1 says to ,ferdinand ,csarina3 8,i remembered an experiment which ,signor ,galileo had shown me more than thirty-five years ago4 ,he took a glass bottle about the size of a hen's egg1 the neck of which was two palms long1 and as narrow as a straw4 ,having well heated the bulb in his hands1 he placed its mouth in a vessel containing water1 and withdrawing the heat of his hand from the bulb1 the water instantly rose in the neck more than a palm above the level of the water in the vessel40 ,here1 then1 we have an air-thermometer1 but as it was affected by the pressure as well as the temperature of the atmosphere1 it could not be relied upon as a 8measurer of heat40 ,until ,torricelli propounded the principle of the barometer1 this 8weather-glass0 of ,galileo was used1 for the philosopher divided the stem into divisions1 and the air-thermometer served the purpose of our modern instruments4 ,the actual inventor of the thermometer is not known4 ,it has been attributed to ,galileo1 to ,drebbel1 and to ,robert ,fludd4 ,there is little doubt1 however1 that ,galileo and ,drebbel were both acquainted with it1 but whether either claimed the honour of the invention1 whether they discovered it independently1 or together1 we cannot say4 ,sanctorio1 of ,padua1 and ,drebbel have also been credited with the invention4 ,we may add that the spirit thermometer was invented in #afee-afef4 ,it was a rough form of our present thermometer1 and roughly graduated4 ,but it was hermetically closed to the air1 and a great improvement on the old 8weather-glass4 ,edmond ,halley introduced mercury as the liquid for the instrument in #afhj4 ,otto von ,guerike first suggested the freezing point of water as the lowest limit1 and ,renaldini1 in #afid1 proposed that the boiling and freezing points of water should be the limit of the scale4 ,let us now explain the construction and varied markings of the three kinds of thermometers in use4 ,by noting the differences between the scales every reader will be able to read the records from foreign countries noted upon the ,centigrade and ,raumur instruments1 which are all based upon the theory that heat expands liquids4 ,we used to hear the expression1 8,heat expands1 and cold contracts10 but we trust that all our readers have now learnt that there is no such thing as cold4 ,it is only a negative term4 ,we feel things cold because they extract some warmth from our fingers1 not because the substances have no heat4 ,thermometers are made of very fine bore glass tubes4 ,one end has a bowl1 or bulb1 the other is at first open4 ,by heating the bowl the air in the tube is driven away by the open end1 which is quickly dipped in a bowl of mercury4 ,the mercury will then occupy a certain space in the tube2 and if it be heated till the liquid boils1 all the air will be driven out by the mercurial vapour4 ,by once again dipping the tube in the quicksilver the glass will be filled4 ,then1 before it cools1 close the open end of the tube1 and the thermometer is so far made4 ,having now caught our thermometer we must proceed to mark it1 which is an easy process4 ,by plunging the mercury into pounded melting ice we can get the freezing point1 and boiling water will give us the boiling point4 ,the intermediate scale can be then indicated4 ,if mercury and glass expanded equally there would be no rise in the latter4 ,extreme delicacy of the thermometer can be arrived at by using a very fine tube1 particularly if it be also flat4 ,the freezing point in ,fahrenheit's scale is #cb2 in the ,centigrade it is #j1 and the boiling point #ajj4 ,this was the scale adopted by ,celsius1 a ,swede1 and is much used4 ,raumur called the freezing point #j1 and the boiling point #hj4 ,there is another scale1 almost obsolete1--that of ,delisle1 who called boiling point zero1 and freezing point #aej4 ,there is no difficulty in converting degrees on one scale into degrees on the other4 ,fahrenheit made his zero at the greatest cold he could get2 viz41 snow and salt4 ,the freezing point of water is #cb above his zero4 ,therefore #bab-cb gives #ahj the difference between the freezing and boiling points of water4 ,so #ahj ,fahr4 corresponds to #ajj ,cent41 and to #hj ,raumur1 reckoning from freezing point4 ,illustration3 ,fig4 #gi4--,thermometer4 ,the following tables will explain the differences3-- ,,table ,i4 #a ,fahr4 #jee ,cent41 or #jdd ,raumur4 #a ,cent4 #hj ,raumur1 or #ahj ,fahr4 #a ,raumur #abe ,cent41 or #bbe ,fahr4 ,,table ,,ii4 ---------------------------------------- ---------- ,fahr4 ,cent4 ,raumur4 ---------------------------------------- ---------- ,boiling point #bab #ajj #hj #aid #ij #gb #agf #hj #fd #aeh #gj #ef #adj #fj #dh #abb #ej #dj #ajd #dj #cb #hf #cj #bd #fh #bj #af #ej #aj #h ,freezing point of water #cb #j #j #ad -#aj -#h -#d -#bj -#af ,freezing point of ,mercury -#dj -#dj -#cb ---------------------------------------- ---------- ,alcohol is used in thermometers in very cold districts1 as it does not freeze even at a temperature of -#acb ,fahr4 ,we have now explained the way in which we can measure heat by the expansion of mercury in a tube4 ,we can also find out that solids and gases expand also4 ,engineers always make allowances for the effects of winter and summer weather when building bridges2 in summer the bridge gets longer1 and unless due provision were made it would become strained and weakened4 ,so there are compensating girders1 and the structure remains safe4 ,the effects of expansion by heat are very great and very destructive at times4 ,instances of boilers bursting will occur to every reader4 ,it is very important to be able to ascertain the extent to which solid bodies will expand4 ,such calculations have been made1 and are in daily use4 ,we can crack a tumbler by pouring hot water into it1 or by placing it on the 8hob40 ,a few minutes' consideration will assure us that the lower particles of the glass expanded before the rest1 and cracked our tumbler4 ,a gradual heating1 particularly if the glass be thin1 will ensure safety4 ,thick glass will crack sooner than thin4 ,again1 many people at railway stations have asked us1 8,why don't they join the rails together on this line80 ,we reply that if every length of rail were tightly fixed against its neighbour1 the whole railway would be displaced4 ,the iron expands and joins up close in hot weather4 ,in wet weather1 also1 the wooden pegs and the sleepers swell with moisture1 and get tightened up4 ,everyone knows how much more smoothly a train travels in warm1 wet weather4 ,this is due to the expansion of the iron and the swelling of the sleepers and pegs in the 8chairs40 ,a railway #djj miles long expands #cch yards in summer1--that is the difference in length between the laid railroad in summer and in winter4 ,this can be proved4 ,iron expands #jjjabce of its length for every #ahj ,fahr4 ,divided by #ahj it gives us the expansion for #a1 which is #jjjjjjfhf1 taking the difference of winter and summer at #gj ,fahr4 ,multiply these together1 and the result 7#jjjjdhfbj of its length7 by the number of yards in #djj miles1 and we find our answer #cch yards4 ,expansion acts in solids and most liquids by the destruction of cohesion between the particles4 ,gases1 however1 having much less cohesion amid the particles1 will expand far more under a given heat than either solids or liquids1 and liquids expand more than solids for the same reason1 and more rapidly at a high temperature than at a low one4 ,we have spoken of expansion4 ,we may give an instance in which the subsequent contraction of heated metal is useful4 ,walls sometimes get out of the perpendicular1 and require pulling together4 ,no force which can be conveniently applied would accomplish this so well as the cooling force due to the potential energy of iron4 ,rods are passed through the walls and braced up by nuts4 ,the rods are then heated1 and as they cool they contract and pull the walls with them4 ,when glass is suddenly cooled1 the inner skin1 as it were1 presses with great force against the cooled surface1 but as it is quite tight no explosion can follow4 ,but break the tail1 or scratch it with a diamond1 and the strain is taken off4 ,the glass drop crumbles with the effect of the explosion1 as in the cases of ,prince ,rupert's drops1 and the ,bologna flasks2 the continuity is broken1 and pulverization results4 ,but a very curious exception to the general laws of expansion is noticed in the case of nearly freezing water4 ,we know water expands by heat1 at first gradually1 and then to an enormous extent in steam4 ,but when cooling water1 instead of getting more and more contracted1 only contracts down to #cib ,fahr41 it then begins to expand1 and at the moment it freezes into ice it expands very much--about one-twelfth of its volume1 but according to ,professor ,huxley it weighs exactly the same1 and the steam produced from that given quantity of water will weigh just exactly what the water and the ice produced by it weigh individually4 ,at #cib ,fahr4 water is at its maximum density1 or in other words1 a vessel of a certain size will hold more water when it is at #ci ,fahr4 than at any other time4 ,whether the water be heated or cooled at this temperature1 it expands to the boiling or freezing point when it becomes steam or ice1 as the case may be4 ,water1 when heated1 is lighter than cold water4 ,you can prove this in filling a bath from two taps of hot and cold water at the same time4 ,the cold falls to the bottom1 and if you do not stir up the water when mixed you will have a hot surface and a cold foundation4 ,the heat increases the volume of water1 it becomes lighter1 and comes uppermost4 ,steam and ,water and ,ice are all the same things under different conditions1 although to the eye they are so different4 ,they are alike inasmuch as a given weight of water will weigh as much when converted into ice or developed into steam4 ,the half ounce of water will weigh half an ounce as ice or as steam1 but the volume or bulk will vary greatly1 as will be understood when we state that one cubic inch of water will produce #a1gjj cubic inches of steam1 and #a-a_/aa cubic inch of ice2 but at the same time each will yield1 when decomposed1 just the same amount of oxygen and hydrogen4 ,let us now consider the ,effects of ,heat upon ,water4 ,we have all seen the vapour that hangs above a locomotive engine4 ,we call it 8steam40 ,it is not pure steam1 for steam is really invisible4 ,the visible vapour is steam on its way to become water again4 ,on a very hot dry day we cannot distinguish the vapour at all4 ,the first effect of heat upon water is to expand it2 and as the heat is applied we know that the water continues to expand and bubble up2 and at last1 when the temperature is as high as #bab1 we say water 8boils0--that is1 at that heat it begins to pass away in vapour1 and you will find that the temperature of the steam is the same as the boiling water4 ,while undergoing this transformation1 the water increases in volume to #a1gjj times its original bulk1 although it will weigh the same as the water4 ,so steam has #a1gjj less specific gravity than water4 ,it is perhaps scarcely necessary to remind our readers that water1 when heated1 assumes tremendous force4 ,air likewise expands with great violence1 and the vessels containing either steam or air frequently burst1 with destructive effects4 ,solid bodies also expand when heated1 and the most useful and accurate observations have been made1 so that the temperatures at which solid bodies expand are now exactly known4 ,air also expands by heat4 ,while speaking of ,expansion by ,heat1 we may remark that a rapid movement is imparted to the air by ,heat4 ,in any ordinary room the air below is cool1 while if we mount a ladder to hang up a picture1 for instance1 we shall find the air quite hot near the ceiling4 ,this is quite in keeping with the effects of heat upon water4 ,the hot particles rise to the top in a vessel1 and thus a motion is conveyed to the water4 ,so in our rooms4 ,the heated air rushes up the chimney and causes a draught1 and this produces motion1 as we have seen by fig4 #ci1 in which the cardboard spiral was set in motion by heated air4 ,a balloon will ascend1 because it is filled with heated air or gas2 and we all have seen the paper balloons which will ascend if a sponge containing spirit of wine be set on fire underneath them4 ,winds are also only currents of air produced by unequal temperature in different places4 ,the heated air ascends1 and the colder fluid rushes in sometimes with great velocity to fill the space4 8,land0 and 8sea0 breezes are constant2 the cool air blows in from the sea during the day1 and as the land cools more rapidly at night1 the breeze passes out again4 ,when we touch upon ,meteorology1 we will have more to say respecting ,air ,currents and the various ,atmospheric ,phenomena4 ,we know that water can be made to boil by heat1 but it is not perhaps generally known that it will apparently boil by cold1 and the experiment may thus be made3--,a flask half-full of water is maintained at ebullition for some minutes4 ,it is removed from the source of heat1 corked1 inverted1 and placed in one of the rings of a retort stand4 ,if cold water is poured on the upturned bottom of the flask1 the fluid will start into violent ebullition4 ,the upper portion of the flask is filled with steam1 which maintains a certain pressure on the water4 ,by cooling the upper portion of the flask some of this is condensed1 and the pressure reduced4 ,the temperature at which water boils varies with the pressure4 ,when it is reduced1 water boils at a lower heat4 ,by pouring the cold water over the flask we condense the steam so that the water is hot enough to boil at the reduced pressure4 ,to assert that water boils by the application of cold is a chemical sophism4 ,ebullition and ,evaporation may be now considered1 and these are the two principal modes by which liquids assume the gaseous condition4 ,the difference is1 when water boils we term it ebullition 7from the ,latin ebullio1 ,i boil72 evaporation means vapour given out by water not boiling 7from evaporo1 ,i disperse in vapour74 ,there are two operations based upon the properties which bodies possess of assuming the form of vapour under the influence of heat1 which are called ,distillation and ,sublimation4 ,these we will consider presently4 ,ebullition then means a bubbling up or boiling2 and when water is heated in an open vessel two forces oppose its conversion into vapour2 viz41 its own cohesive force and atmospheric pressure4 ,at length1 at #bab ,fahr41 the particles of water have gained by heat a force greater than the opposing forces2 bubbles of vapour rise up from the bottom and go off in vapour4 ,this is ebullition1 and at that point the tension of the vapour is equal to the pressure of the atmosphere1 for if not1 the bubbles would not form4 ,all this time of boiling1 notwithstanding any increase of heat1 the thermometer will not rise above #bab 7,fahr471 for all the heat is employed in turning the water to steam4 ,we have said the ebullition takes place at #bab ,fahr4 7or #ajj ,c471 but that is only at a certain level4 ,if we ascend #fjj feet high we shall find that water will boil at a less temperature2 and on the top of a mountain 7say ,mont ,blanc7 water will boil at #ahe ,fahr42 so at an elevation of three miles water boils at a temperature less by #bg ,fahr4 ,an increase of pressure similarly will raise the boiling point of water4 ,the heights of mountains are often ascertained by noticing the boiling point of water on their summits1 the general rule being a fall of one degree for every #ecj feet elevation at medium altitudes4 ,we append a few instances taken at random3-- ---------------------------------------- -------------------------- ,place4 ,height above level ,barometer ,boiling point of the sea--,feet4 mean height4of water1 ,fahr4 ---------------------------------------- -------------------------- ,quito #i1eda #bjge #aidb ,mexico #g1dga #bbeb #aiha ,st4 ,gothard #f1hjh #bcjg #aiib ,garonne 7,pyrenees7 #d1gch #bdif #bjcj ,geneva #a1bba #bhed #bjie ,paris 7#ast floor7 #bac #bifi #baae ,sea level #j #cjjj #babj ---------------------------------------- -------------------------- ,the difference for a degree depends upon the height1 varying between #eaj and #eij feet1 according to the elevation reached4 ,the approximate height of a mountain can be found by multiplying #ecj by the number of degrees between the boiling point and #bab4 ,in some very elevated regions travellers have even failed to boil potatoes4 ,the boiling point of liquid may be altered by mixing some substance with it2 and although such a substance as sawdust would not alter the boiling point of water1 yet if the foreign matter be dissolved in the liquid it will alter the boiling point4 ,even the air dissolved in liquids alters their boiling point1 and water freed from air will not boil till it is raised to a temperature much higher than #bab ,fahr4 ,water will boil at a higher temperature in a glass vessel than in metal1 because there is a greater attraction between water and glass4 ,we said above that an increase of pressure will raise the boiling point of water4 ,under the pressure of one atmosphere--that is1 when there is a pressure of #ae lbs4 on the square inch--water boils at #bab4 ,but under a pressure of two atmospheres1 the boiling point rises to #bcd1 and of four atmospheres1 #bid4 ,so we see by increasing the pressure the water may be almost indefinitely heated1 and it will not boil4 ,we can understand that in a very deep vessel the layer of water at the bottom has to sustain the pressure of the water in addition to the weight of the atmosphere above it4 ,the pressure of thirty-four feet of water is equal to the atmospheric pressure of #ae lbs4 on the square inch1 and thus at such a distance water must be heated to #bcd before it will boil4 ,professor ,bunsen founded his ,theory of the ,geysers upon this fact1 for he maintained that water falling into the earth lost much air1 and required with the super-incumbent pressure a very high temperature to boil it4 ,when it did boil it generated steam so suddenly that it exploded upwards1 throwing up vapour and the water with it1 as water poured into a very hot basin will do4 ,evaporation may now be considered1 and is distinguished from ,ebullition by the production of vapour on the surface of liquids1 the latter term signifying the formation of vapour in the body of the liquid4 ,evaporation takes place at all temperatures1 and from every liquid surface exposed to the air4 ,we know what we call a 8drying wind40 ,the air in fresh layers continually passing over the wet ground1 takes up the moisture2 like the east wind1 for instance1 which has great capabilities of that nature4 ,damp air can only take up a certain quantity1 and when it contains as much water as corresponds to the temperature it can take no more1 and is 8saturated with moisture02 then evaporation ceases4 ,heat is a great cause of evaporation1 and the greater the surface the more rapid the process1 and in a vacuum more readily than in atmospheric air4 ,evaporation is resorted to very commonly to produce coolness2 for instance1 the universal fan1 by increasing evaporation from a heated skin1 generates a feeling of coolness2 and we know the vaporization of ether will freeze into insensibility4 ,when a fluid evaporates we can tell that the heat passes away at the same time1 for we cool water in porous jars1 which permit some of it to pass off in vapour1 the remainder being cooled4 ,sir ,john ,leslie invented a method of freezing water by rapid evaporation on sulphuric acid under the receiver of an air-pump1 and water has been frozen even on a hot plate by these means4 ,by pouring sulphurous acid and water on this plate1 the acid evaporates so quickly that it produces sufficient cold to freeze the water it quitted into solid ice4 ,we leave the phenomena of clouds and watery vapour in the atmosphere for consideration on another opportunity1 under the head of ,meteorology1 ,rain1 etc4 ,illustration3 ,fig4 #hj4--;,apparatus for freezing carafes of water4 ,an experiment is often performed by which water is frozen in a vacuum4 ,by putting a saucer full of water under the receiver of an air-pump it will first boil1 and then become a solid mass of ice4 ,it is not difficult to understand the cause of this4 ,the water boils as soon as the air is removed2 but in order to pass from the liquid to the gaseous state without the assistance of exterior heat1 it gives out heat to the surroundings1 and in so doing becomes ice itself4 ,this fact ,mr4 ,carr has made use of in the apparatus shown above 7fig4 #hj74 ,a small pump creates a vacuum in the water bottles1 and ice is formed in them4 ,this apparatus might easily be adopted in country houses1 and in places where ice is difficult to procure in summer4 ,the only inconvenience attending it is the employment of sulphuric acid1 of which a considerable quantity is used to absorb the vapour from the water1 as already referred to4 ,if proper precautions are taken1 however1 there will be no danger in using the apparatus4 ,the mode of proceeding is as follows3--,the bottle full of water is joined to the air-pump by a tube1 and after a few strokes the water is seen in ebullition4 ,the vapour thus disengaged traverses an intermediate reservoir filled with sulphuric acid1 which absorbs it1 and immediately condenses it1 producing intense cold4 ,in the centre of the liquid remaining in the carafe some needles of ice will be seen1 which grow rapidly1 and after a few more strokes of the pump the water will be found transformed into a mass of ice4 ,this is very easy of accomplishment1 and in less than a minute the carafe full of water will be found frozen4 ,the problem for the truly economical formation of ice by artificial means is one of those which have occupied chemists for a long time1 but hitherto1 notwithstanding all their efforts1 no satisfactory conclusion has been arrived at4 ,nearly every arrangement possesses some drawback to its complete success1 which greatly increases the cost of the ice1 and causes inconvenience in its production4 ,the usual mode in large towns is to collect the ice1 in houses constructed for the purpose1 during the winter1 and this simple method is also the best1 so far as at present has been ascertained4 ,illustration3 ,fig4 #ha4--,retort and ,receiver4 ,in connection with vaporization we may now mention two processes referred to just now 7page #hc72 viz41 sublimation and distillation4 ,the former is the means whereby we change solid bodies into vapour and condense the vapour into proper vessels4 ,the condensed substances when deposited are called sublimates1 and when we go into ,chemistry we shall hear more of them4 ,the mode of proceeding is to place the substance in a glass tube1 and apply heat to it4 ,vapour will be formed1 and will condense at the cool end of the tube4 ,the sublimate of sulphur is called 8,flowers of ,sulphur10 and that of perchloride of mercury 8,corrosive ,sublimate40 ,distillation is a more useful process1 or1 at any rate1 one more frequently employed1 and is used to separate a volatile body from substances not volatile4 ,a distilling apparatus 7distillo1 to drop7 converts a liquid to vapour by means of heat1 and then condenses it by cold in a separate vessel4 ,the distilling apparatus consists of three parts1--the vessel in which the liquid is heated 7the still1 or retort71 the condenser1 and the receiver4 ,the simple retort and receiver are shown in fig4 #ha4 ,but when very volatile vapours are dealt with1 the arrangement shown on next page is used 7fig4 #hb74 ,then the vapour passes into the tube encased in a larger one1 the intervening space being filled with cold water from the tap above 7c71 the warm water dropping from g4 ,the vapours are thus condensed1 and drop into the bottle 7or receiver7 ,b4 ,illustration3 ,fig4 #hb4--;,distilling apparatus4 ,the apparatus for distilling spirits is shown below4 ,the 8still0 ,a is fitted into a furnace1 and communicates with a worm ,o in a metal cylinder filled with water1 kept constantly renewed through the tube ,,tt4 ,this spirit passes through the spiral1 and being condensed1 goes out into the receiver ,c4 ,illustration3 ,fig4 #hc4--,spirit still4 ,there are even more simple apparatus for spirit distilling1 but the diagram above will show the principle of all 8stills40 ,in former days1 in ,ireland1 whiskey was generally procured illegally by these means4 ,,chapter ,,viii4 ,,specific ,,heat--,,fusion--,,latent ,,heat--,,conduction ,,and ,,convection ,,of ,,heat--,,calorescence4 ,we have considered the effects of heat upon water1 and touched upon one or two kindred experiments4 ,but we have some other subjects to discuss1 two in particular2 viz41 ,specific ,heat1 and ,latent ,heat4 ,the specific heat of any substance is 8the number of units of heat required to raise one pound of such substance one degree40 ,we can explain this farther4 ,when heat is communicated to a body it has two or three functions to perform4 ,some of it has to overcome the resistance of the air in expanding the body1 more of it expands1 and the remainder increases the temperature of the body4 ,so some heat disappears as heat1 and is turned into energy1--8molecular potential energy10--as it is called1 and the rest remains4 ,of course in objects the molecules vary very much in weight and in their mutual attraction1 and the heat requisite to raise equal weights of different substances through the same number of degrees of temperature will vary4 ,this is called capacity for heat1 or specific heat4 ,the capacity of different metals for heat can easily be shown4 ,the specific heat of water is very high1 because its capacity for heat is great4 ,we can cool a hot iron in very little water1 and it takes thirty times as much heat to raise a given weight of water a certain number of degrees1 as it would to raise the same weight of mercury to the same temperature4 ,water has greater specific heat1 generally speaking1 than other bodies1 and it is owing to this circumstance that the climate is so affected by ocean currents4 ,nearly all substances can be melted by heat1 if we go far enough1 or frozen1 if we could take the heat away4 ,solid can be made liquid1 and these liquids can be made gases and fly off in vapour4 ,similarly1 if we could only get heat away sufficiently from the atoms of a substance we could freeze it4 ,we cannot freeze alcohol1 nor make ice from air1 nor can we liquify it1 for we are unable to take away its heat sufficiently4 ,but we can turn water into steam1 and into ice2 or ice into water1 and then into steam4 ,but there is one body we cannot melt by heat1 that is carbon4 ,in the hottest fire coal will not melt1 it becomes soft4 ,we call this melting fusion1 and every body has its melting point1 or fusing point1 which is the same at all times if the air pressure be the same4 ,it is a curious fact that when a body is melting it rises to a certain temperature 7its fusing point71 and then gets no hotter1 no matter whether or not the fire be increased2--all the extra heat goes to melt the remainder of the substance4 ,the heat only produces changes of state4 ,so this heat above fusing point disappears apparently1 and is called ,latent ,heat4 ,this can easily be proved by melting ice4 ,ice melts at #cb ,fahr41 or #j ,cent41 and at that temperature it will remain so long as any ice is left2 but the water at #cb1 into which the ice has melted1 contains a great deal of latent heat1 for it has melted the ice quickly1 and yet the thermometer does not show it4 ,it is just the same with boiling water4 ,when substances are fused they expand as a rule1 but ice contracts2 so does antimony4 ,on the other hand1 when water solidifies it does not contract as most things do4 ,it expands1 as many of us are aware1 by finding our water pipes burst in the winter2 and the geologist will tell us how the tiny trickling rills of water fall in between the cracks of rocks and there freeze4 ,in freezing the drops expand and split the granite blocks4 ,type-metal expands also when it becomes solid1 and leaves us a clear type2 but copper contracts1 and won't do for moulding1 so we have to stamp it when we want an impression on it4 ,there is no doubt that chemical combinations produce heat1 as we can see every day in house-building operations1 when water is poured upon lime2 but there are also chemical combinations which produce cold4 ,fahrenheit produced his greatest cold by combining snow and salt1 for in the act of combining1 a great quantity of heat is swallowed up by reason of the heat becoming latent1 as it will do when solid bodies become liquid4 ,such mixtures or combinations are used as ,freezing ,mixtures when it is necessary to produce intense cold artificially4 ,sulphate of ,sodium and ,hydrochloric acid will also produce great cold1 and there are many other combinations equally or even more efficacious4 ,heat is communicated to surrounding objects in three well-known ways--by conduction1 by radiation1 and by convection4 ,conduction of heat is easily understood1 and is the propagation of heat through any body1 and it varies very much according to the substance through which it passes4 ,some substances are better conductors of heat than others4 ,silver has a far greater conductivity than gold1 and copper is a better heat-conductor than tin4 ,flannel is a non-conductor1 or rather a bad conductor1 for no substance can be termed actually a non-conductor4 ,flannel1 we know1 will keep ice from melting1 and a sheep's wool or a bird's feathers are also bad conductors of heat2 so ,nature has provided these coverings to keep in the animal heat of the body4 ,a good conductor of heat feels cold to the touch of our fingers1 because it takes the heat from our hands4 ,this can be tried by touching silver1 lead1 marble1 wood1 and wool4 ,each in turn will feel cold and less cold1 because they respectively draw away1 or conduct less and less heat from our bodies4 ,so our clothes are made of bad-conducting substances4 ,the bark of a tree is a bad conductor1 and if you strip off this clothing the tree will die4 ,solids conduct heat the better the more compact they are4 ,air being a bad conductor it follows that the less tightly the molecules are packed the less conductibility there will be2 and even a substance powdered will be a worse conductor than the same substance in solid form2 and also more readily in the direction of the fibres than crossways4 ,liquids do not possess great conductivity1 but they1 as well as gases1 are influenced by convection1 or the transport of heat from the bottom layers to the top 7conveho1 to carry up74 ,we have already mentioned that the heated particles of water rise to the top because they expand1 and so become lighter4 ,this is convection of heat2 and by it liquids and gases1 though actually bad conductors1 may become heated throughout to a uniform temperature4 ,of course the more easily expansible the body is the more rapidly will convection take place--so gases are more readily affected than liquids4 ,solids are not affected1 because convection of heat depends upon molecular movement or mobility1 and it is obvious that the particles of solid bodies are not mobile4 ,professor ,balfour ,stewart says with reference to this that 8were there no gravity there would be no convection10 for the displacement of the light warm particles by the heavier cold ones is due to gravity4 ,the instances of convection of heat in nature are numerous1 and on a gigantic scale4 ,the ocean currents1 trade winds1 lake freezing1 etc41 while the chimney draught already referred to1 is another example2 and in all these cases the particles of air or water are replaced by convection4 ,in the case of the lake freezing the cold particles at the top sink1 and the warmer ones ascend1 until all the lake is at a temperature of #cfb1 or say #d above freezing4 ,at this temperature water assumes its maximum density1 and then expands1 as we have seen1 instead of contracting4 ,ice is formed1 and being thus lighter than water1 floats2 and so unites to cover in the water underneath1 which is never frozen solid1 because the cold of the atmosphere cannot reach it through the ice in time to solidify the whole mass4 ,illustration3 ,fig4 #hd4--,radiant heat4 ,radiant heat is the motion of heat transmitted to the ether1 and through it in the form of waves4 ,the sun's heat is radiant heat1 and radiation may be defined as 8,the communication of the motion of heat from the articles of a heated substance to the ether40 ,the fire gives out radiant heat1 and so does heated metal1 and it is transmitted by an unseen medium4 ,it is quite certain that the heat of a suspended red-hot poker is not communicated to the air1 because it will cool equally in a vacuum4 ,sir ,humphrey ,davy proved that radiant heat could traverse a vacuum1 for by putting tin reflectors in an exhausted receiver he found that a hot substance in the focus of one reflector caused an increase in the heat of the other4 ,if we put a red-hot or a hot substance in one reflector1 and tinder in the other1 the latter will take fire4 ,the velocity of heat rays is equal to that of light1 #ahf1jjj miles in a second1 and indeed1 radiant heat is identical with light4 ,heat is reflected as is light1 and is refracted in the same way as sound4 ,some bodies allow the heat rays to pass through them1 as air does1 and as rock salt will do4 ,white clothing is preferable in summer 7and also in winter if we could only make people believe it74 ,white garments radiate less heat in winter1 and absorb less heat in summer4 ,an old black kettle will boil water more quickly than a new bright one1 but the latter will keep the water hotter for the longer time when not on the fire4 ,heat1 then1 is movement of particles4 ,energy can be changed into heat1 as the savage finds when he rubs the bits of wood to produce heat and fire4 ,friction causes heat1 and chemical combination produces heat2 and1 if 8visible energy can be turned into heat1 heat can be turned back into visible energy40 ,for fire heats water1 water expands into steam1 and steam produces motion and energy in the steam-engine4 ,if we heat water in ,wollaston's bulb1--the opening of which is hermetically stopped by a piston1--the vapour will raise the piston4 ,if we cool the bulb we condense the steam1 and the piston falls4 ,here we have the principle of the steam-engine4 ,,steam is the vapour of water educed by heat1 and we may give a few particulars concerning it4 ,its mechanical properties are the same as those of other gases1 and pure steam is colourless and transparent--in fact1 invisible4 ,its power when confined in boilers and subjected to pressure is enormous1 for the volume of the steam is far greater than the water which gave rise to it4 ,one cubic inch of water will produce #a1gjj cubic inches of steam--in other words1 a cubic inch of water produces a cubic foot of steam4 ,when we obtain steam at #bab1 we do so under the pressure of one atmosphere2 but by increasing the pressure we can raise the boiling point1 and thus water at the pressures of sixteen atmospheres will not steam till it reaches #cih4 ,it is thus we obtain pressure for locomotives1 and other engines1 although a very small portion of the steam does work4 ,much the largest portion is expended in overcoming cohesion1 and one way and another1 taking into consideration defects in machinery1 only about one-tenth of the heat is employed in doing the work4 ,the force exercised by steam under atmospheric pressure is sufficient to raise a ton weight one foot4 ,to obtain very high temperatures we shall find the thermometer of no use1 for mercury boils at #ffb1 so an instrument called a ,pyrometer is used to ascertain the fusing point of metals4 ,mr4 ,wedgwood1 the celebrated china manufacturer1 invented an instrument made of small cylinders of clay moulded and backed1 placed between two brass rods as gauges divided into inches and tenths4 ,but this instrument has been long superseded by ,professor ,daniell's ,pyrometer1 which consists of a small bar of platina in an earthenware tube4 ,the difference of expansion between the platina and the tube is measured on a scale on which one degree is equal to seven degrees of ,fahrenheit4 ,thus the melting temperatures of metals are ascertained4 ,the reflection and refraction of heat are ruled by the same laws as the reflection and refraction of light4 ,a convex lens will bring the heat or light to a focus1 and will act as a burning-glass if held in the sunlight4 ,gunpowder has been ignited by a lens of ice1 and more than one house has been mysteriously set on fire at midday in summer by the sun's rays shining through a glass globe of water containing gold fish1 and falling upon some inflammable substance4 ,professor ,tyndall performed a series of experiments of a very interesting nature1 described in his book1 8,heat considered as a ,mode or ,motion10 and showed the transmutation of invisible heat rays into visible rays1 by passing a beam of electric light through an opaque solution1 and concentrating it upon a lens4 ,the dark heat rays were thus brought to a focus1 all the light was cut off1 and at the dark focus the heat was found to be intense enough to melt copper and explode gunpowder4 ,this change of invisible heat into light is termed ,calorescence4 ,it was ,sir ,william ,herschell who discovered that there were heat rays beyond the red end of the spectrum4 ,when light is split up into its component rays1 or decomposed1 ,sir ,william found that the heat increased as the thermometer passed from violet to indigo1 and so on to blue1 green1 orange1 and red1 and the last were the hottest1 while beyond the spectrum there was heat even greater4 ,a ,heat ,spectrum was thus discovered1 and by comparing1 by means of the thermometer1 the various degrees of heat within certain limits1 ,professor ,tyndall found that the invisible ,heat ,spectrum is longer than the visible ,light ,spectrum4 ,,chapter ,,ix4 ,,light ,,and ,,its ,,sources--,,what ,,is ,,light8--,,velocity ,,of ,,light--,,reflection ,,and ,,refraction--,,relative ,,value ,,of ,,lights4 ,the subject of ,light and the science of ,optics are so interesting to all of us that some short history of light is necessary before we can enter upon the scientific portion of the subject4 ,the nature of the agent 7as we may term light7 upon which our sight depends has employed man's mind from a very early period4 ,the ancients were of opinion that the light proceeded from the eye to the object looked at4 ,but they discovered some of the properties of light4 ,ptolemy of ,alexandria1 who was born ,a4,d4 #gj1 made some attempts to discover the law of ,refraction2 and we are informed that ,archimedes set the ,roman fleet on fire with burning-glasses at ,syracuse4 ,the ,arabian treatise of ,alhagen1 in #aajj ,a4,d41 contains a description of the eye and its several parts2 and the writer notices refraction and the effects of magnifying glasses 7or spectacles74 ,galen1 the physician1 practically discovered the principle of the stereoscope1 for he laid down the law that our view of a solid body is made up of two pictures seen by each eye separately4 ,still the science of optics made little progress till the law determining the path of a ray of light was made known1 and the laws of refraction discovered4 ,refraction means that a ray is deflected from its straight course by its passage from one transparent medium to another of different density4 ,the old philosophers found out the theory of sound1 and they applied themselves to light4 ,newton said light consisted of minute particles emanating from luminous bodies4 ,huyghens and ,euler opposed ,newton's theory of the emission of light2 and it was not till the celebrated ,thomas ,young1 ,professor at the ,royal ,institution1 grappled with the question that the undulating or wave theory of light was found out4 ,he based his investigations upon the theory of sound waves2 and we know that heat1 light1 and sound are most wonderfully allied in their manner of motion by vibration4 ,but he was ridiculed1 and his work temporarily suppressed by ,mr4 ,brougham4 ,light1 then1 is a vibratory motion 7like sound and heat71 a motion of the atoms of our ether4 ,but how is the motion transmitted8 ,sound has its medium1 air2 and in a vacuum sounds will be very indistinctly heard1 if heard at all4 ,but what is the medium of communication of light8 ,it is decided that light is transmitted through a medium called ether1 a very elastic substance surrounding us4 ,the vibrations1 ,professor ,tyndall and other philosophers tell us1 of the luminous atoms are communicated to this ether1 or propagated through it in waves2 these waves enter the pupil of the eye1 and strike upon the retina4 ,the motion is thus communicated by the optic nerve to the brain1 and then arises the great primary faculty1 ,consciousness4 ,we see light1 the waves of which1 or ether vibrations1 are transversal2 air waves or sound vibrations are longitudinal4 ,we have spoken of radiant heat4 ,light acts in the same way through the ether2 and when we consider ,sound we shall learn that a certain number of vibrations of a string give a certain sound1 and the quicker the vibration the shriller the tone4 ,so in light4 ,the more quickly the waves of luminosity travel to our eye1 and the faster they strike it1 the greater the difference in the colour1 or what we call colour4 ,light as we see it is composed of different colours1 as visible in the rainbow4 ,there are seven primary colours in the sunlight1 which is white4 ,these can be divided or 8dispersed10 and the shortest rays of the spectrum are found to be violet1 the longest red4 ,it has been calculated that #ci1jjj red waves make an inch in length4 ,light travels at a rate of nearly #aij1jjj miles a second1 so if we multiply the number of inches in that distance by the number of red waves1 we shall have millions of millions of waves entering the eye in a single second of time4 ,the other waves enter more rapidly still1 and 8the number of shocks corresponding to the impression of violet is seven hundred and eighty-nine millions of millions0 per second6 ,or taking the velocity of light at #ahf1jjj miles in a second1 it would be six hundred and seventy-eight millions of millions 7,tyndall74 ,there may be other colours which we cannot see because the impressions come too rapidly upon the retina2 but the violet impression has been thus accurately determined4 ,see page #afh4 ,we have seen that heat is a kind of motion of particles in a body--a vibratory motion which1 instead of being apparent to the ear1 is apparent to the eye in rays of light4 ,thus heat1 sound1 and light are all intimately connected in this way4 ,we have also learnt that rays of light radiate and travel with tremendous speed to our eyes1 but without any shock4 ,there is no feeling connected with the entrance of light to the eye any more than there is any sensation of sound when entering the ear1 except when the light is vividly and very suddenly revealed1 or when a very piercing sound is heard4 ,then the nerves are excited1 and a painful sensation is the result2 but under ordinary circumstances we are not physically conscious of the entrance of light or sound4 ,heat and light are considered to be one and the same thing in different degrees of intensity4 ,the sources of light are various4 ,the sun and fixed stars1 heat1 electricity1 many animals1 and some plants1 as well as decaying animal matter1 give out light4 ,there are luminous and non-luminous bodies4 ,the moon is non-luminous1 as she derives her light from the sun1 as does the earth1 etc4 ,light is distributed in rays4 ,these rays are straight in all directions4 ,the velocity of light is almost inconceivable4 ,it travels at a rate of #ahf1ejj miles a second4 ,the latest computation with electric light has given a rate of #ahg1bjj miles a second2 but the blue rays in the light experimented on probably account for the difference1 for blue rays travel quicker by one per cent4 than red rays4 ,rmer first found out the velocity of light1 which comes to us from the sun--ninety millions of miles--in eight minutes4 ,fizeau calculated the velocity by means of a wheel1 which was set moving with tremendous speed by making the light pass between the teeth of the wheel and back again4 ,when rays of light meet substances they are deflected1 and the phenomena under these circumstances are somewhat similar to the phenomena of heat and sound4 ,there are three particular conditions of rays of light3 7#a7 they are absorbed2 7#b7 they are reflected2 7#c7 they are refracted4 ,firstly4 ,let us see what we mean by light being absorbed2 and this is not difficult to understand1 for any 8black0 substance shows us at once that all the sunlight is taken in by the black object1 and does not come out again4 ,it does not take in the light and radiate it1 as it might heat4 ,the rose is red1 because the rays of light pass through it1 and certain of them are reflected from within4 ,so colour may be stated to be the rays thrown out by the objects themselves--those they reject or reflect being the 8colour0 of the object4 ,illustration3 ,fig4 #he4--;,angle of reflection1 etc4 ,secondly4 ,bodies which reflect light very perfectly are known as mirrors1 and they are termed plane1 concave1 or convex mirrors1 according to form4 ,a plane mirror reflects so that the reflected ray d i forms the same angle with the perpendicular as the incident ray r i2 in other words1 the angle of incidence is always equal to the angle of reflection1 and these rays are perpendicular to the plane from which they are reflected4 ,the rays diverge1 so that they appear to come from a point as far behind the mirror as the luminous point is in front1 and the images reflected have the same appearance1 but reversed4 ,there is another law1 which is that 8the angular velocity of a beam reflected from a mirror is twice that of the mirror40 ,the ,kaleidoscope1 with which we are all familiar1 is based upon the fact of the multiplication of images by two mirrors inclining towards each other4 ,illustration3 ,fig4 #hf4--;,concave mirror4 ,a concave mirror is seen in the accompanying diagram1 and may be called the segment of a hollow sphere--,v ,w4 ,the point ,c is the geometrical centre1 and ,o ,c the radius2 ,f is the focus2 the line passing through it is the optical axis2 ,o being the optical centre4 ,all perpendicular rays pass through ,c4 ,all rays falling in a direction parallel with the optical axis are reflected and collected at ,f4 ,magnified images will be produced1 and if the object be placed between the mirror and the focus1 the image will appear at the back2 while if the object be placed between the geometrical centre and the focus1 the image will appear to be in front of the mirror4 ,we can understand these phenomena by the accompanying diagrams4 ,suppose a ray ,a n passes from one object1 ,a ,b1 at right angles1 it will be reflected as n ,a ,c1 the ray ,a ,c being reflected to ,f4 ,these cannot meet in front of the mirror1 but they will if produced meet at a1 and the point ,a will be reflected there2 similarly ,b will be reflected at b1 and thus a magnified image will appear behind or at the back of the mirror's surface4 ,in the next diagram the second supposed case will produce the image in the air at a b1 and if a sheet of paper be held so that the rays are intercepted1 the image will be visible on the sheet4 ,in this case the perpendicular ray1 ,a n1 is reflected in the same direction1 and the ray1 a c1 parallel with the axis is reflected to the focus4 ,these rays meet at a and corresponding rays at b1 when the image will be reproduced2 viz41 in front of the mirror4 ,illustration3 ,fig4 #hg4--,reflection of mirrors 7,i74 ,illustration3 ,fig4 #hh4--,reflection of mirrors 7,,ii74 ,the concave mirror is used in the manufacture of telescopes1 which1 with other optical instruments1 will be described in their proper places4 ,we will now look at the ,refraction of light4 ,bodies which permit rays of light to pass through them are termed transparent4 ,some possess this property more than others1 and so long as the light passes through the same medium the direction will remain the same4 ,but if a ray fall upon a body of a different degree of density it cannot proceed in the same direction1 and it will be broken or refracted1 the angle it makes being termed the angle of refraction4 ,for instance1 a straight stick when plunged into water appears to be broken at the point of immersion4 ,this appearance is caused by the rays of light taking a different direction to our eyes4 ,if in the diagram 7fig4 #hi7 our eye were at o1 and the vessel were empty1 we should not see m2 but when water is poured into the vessel the object will appear higher up at n1 and all objects under water appear higher than they really are4 ,illustration3 ,fig4 #hi4--,refraction in water4 ,illustration3 ,fig4 #ij4--;,a water-bottle employed as a convergent lens4 ,one may also place a piece of money at the bottom of a basin1 and then stoop down gradually1 until1 the edge of the basin intervening1 the coin is lost to view4 ,if an operator then fills the basin with water1 the piece of money appears as though the bottom had been raised4 ,the glass lenses used by professors may be very well replaced by a round water-bottle full of water4 ,a candle is lighted in the darkness1 and on holding the bottle between the light and a wall which acts as a screen1 we see the reflected light turned upside down by means of the convergent lens we have improvised 7fig4 #ij74 ,a balloon of glass constitutes an excellent microscope4 ,it must be filled with perfectly clear1 limpid water1 and closed by means of a cork4 ,a piece of wire is then rolled round its neck1 and one end is raised1 and turned up towards the focus2 viz41 to support the object we wish to examine1 which is magnified several diameters4 ,if a fly1 for instance1 is at the end of the wire1 we find it is highly magnified when seen through the glass balloon 7fig4 #ia74 ,by examining the insect through the water in the balloon1 we can distinguish every feature of its organism1 thanks to this improvised magnifier4 ,this little apparatus may also serve to increase the intensity of a luminous focus of feeble power1 such as a lighted candle4 ,it is often employed in this manner by watchmakers4 ,if a bottle full of water is placed on a table1 and exposed to the rays of the sun1 the head of a lucifer match being placed in the brightest centre of light caused by the refracted rays1 the match will not fail to ignite4 ,i have succeeded in this experiment even under an ,october sun1 and still more readily in warm weather4 ,illustration3 ,fig4 #ia4--;,a simple microscope formed with a glass balloon full of water4 ,in the ,conservatoire des ,arts in ,paris a visitor will always notice a number of people looking at the mirrors in the 8optical0 cabinets4 ,these mirrors deform and distort objects in a very curious manner1 and people find much amusement in gazing into them till they are 8moved on0 by the attendants4 ,such experiments create great interest1 and a very excellent substitute for these may be found in a coffee-pot or even in a large spoon1 and all the grotesque appearance will be seen in the polished surface4 ,the least costly apparatus will sometimes produce the most marvellous effects4 ,look at a soap-bubble blown from the end of a straw4 ,when the sphere has a very small diameter the pellicule is colourless and transparent2 but as the air enters by degrees1 pressing upon all parts of the concave surface equally1 the bubble gets bigger as the thickness decreases1 and then the colours appear1--feeble at first1 but stronger and stronger as the thickness diminishes4 ,the study of soap-bubbles and of the effects of the light is very interesting4 ,newton made the soap-bubble the object of his studies and meditations1 and it will ever hold its place amongst the curious phenomena of the ,science of ,optics4 ,but before going into all the phases of ,lights and ,optics we will proceed to explain the structure of the eye1 as it is through that organ that we are enabled to appreciate light and its marvellous effects4 ,illustration3 ,fig4 #ib4--;,grotesque effects of curved surfaces4 ,it is often considered an embarrassing matter to fix precisely the value of two lights4 ,nothing1 however1 can be easier in reality1 as we will show4 ,in comparing different lights1 it is necessary to bear in mind the amount of waste1 the colour of the light1 the luminous value of the source1 and the steadiness of the flame4 ,the luminous value of a lamp-burner is generally equalled by that of a wax candle1 and we will take as an example one of those at six to the pound4 ,very precise appliances are used for this experiment when great exactness is required2 but it is easy to calculate in a simple manner the differences in ordinary lights4 ,supposing we desire to test the value of light given by a lamp and a wax candle1 they must both be placed on the table at an equal height1 ,b and ,a1 7fig4 #ic71 in front of some opaque body1 ,a1 and then a large sheet of paper must be fixed as vertically as possible to form a screen4 ,when ,b and ,a are lighted1 two shadows1 ,e and ,f1 are produced1 to which it is easy to give exactly the same intensity1 by advancing or withdrawing one of the two sources of light4 ,the intensities of the two lights will then be inversely proportional to the squares of the measured distances1 ,,ab and ,,ac4 ,by a similar careful calculation it has been possible to draw up a table of the relative values of various ordinary lights4 ,we have not included here the electric light1 which has recently attracted so much attention1 because this system of lighting can hardly be said to have yet penetrated the domain of domestic life2 but when we consider electricity1 as we hope to do in a future part1 we intend to study this question fully1 for there is no doubt that electricity is becoming more and more adapted to our daily life4 ,illustration3 ,fig4 #ic4--;,an elementary ,photometer4 ,the measurement of intensity of light is called ,photometry1 and the instruments used are ,photometers4 ,bunsen's instrument consists of a screen of writing-paper1 saturated in places with spermaceti to make it transparent4 ,a sperm candle is placed on one side1 and the light to be compared on the other4 ,the lights are provided with graduated bars1 and these lights are then removed farther and farther from the screen till the spots of grease are invisible4 ,the relative intensities are as the squares of the distance from the screen4 ,illustration3 ,fig4 #id4--,the soap-bubble4 ,we append a table showing the comparative cost of light given by ,dr4 ,frankland at the ,royal ,institution some few years ago4 ,the standard of comparison was #bj sperm candles burning for #aj hours at the rate of #abj grains an hour3-- s4 d4 ,wax #g #b ,sperm ,oil #a #aj ,paraffin #c #aj ,spermaceti #f #h ,coal ,gas #j #d ,paraffin ,oil #j #f ,tallow #b #h ,cannel ,gas #j #c ,rock ,oil #j #g ,there are many other interesting experiments connected with ,light1--,spectrum ,analysis1 etc41 etc41--all of which we will defer for a time until we have examined the ,eye and some effects produced upon it by ,light1 illustrated by numerous diagrams in the pages next following4 ,,chapter ,x4 ,,vision ,,and ,,optical ,,illusions--,,the ,,eye ,,described--,,accommodation ,,of ,,the ,,eye--,,chromatic ,,aberration--,,spinning ,,tops4 ,the eye is an optical instrument that may be compared with those constructed by physicists themselves2 the media of which it is composed have surfaces like those which enter into the construction of optical instruments4 ,it was ,kepler who at the end of the eighteenth century discovered the passage of light into the eye4 ,soon after the discovery of the inner chamber he found that the eye realized the conditions that ,porta had combined to obtain the reflection of external objects4 ,we will now briefly state that the coats of this organ are constituted of a fibrous membrane1 ,t 7fig4 #ie71 termed sclerotic1 which is opaque1 except in the anterior portion of the eye1 where it forms the transparent cornea4 ,the crystalline1 ,c1 enshrined behind the cornea1 is the convergent lens of the inner chamber2 it is covered with a transparent membrane1 or capsule1 and is bathed in two fluids1 the aqueous humour1 between the crystalline humour and the cornea1 and the vitreous body1 a gelatinous humour lodged between the crystalline and the back of the eye4 ,the image of exterior objects which is produced by the passage of light through these refracting surfaces1 is received by a nervous membrane1 the retina1 ,b1 formed by an expansion of the optic nerve1 ,n4 ,we must also mention the choroid1 a membrane lined with a dark pigment1 which absorbs the light1 and prevents interior reflections1 and in front of the crystalline lens1 a curtain with an opening1 ,h1 called the iris1 which gives to the eyes their colour of blue1 grey1 or black4 ,the opening in the centre of the iris is called the pupil4 ,illustration3 ,fig4 #ie4--,structure of the eye4 ,the penetration of light through the surfaces of the eye is easily demonstrated4 ,an object throws divergent rays on the cornea1 a part penetrates into the eye and falls upon the retina1 leaving a perfectly retained image of the object4 ,magendie has proved in the following manner the truth of this mathematical deduction4 ,the eye of a rabbit is very similar to an albino's2 that is to say1 the choroid contains no black pigment1 but a transparent matter1 and when placed before a brilliant object1 the image can be seen inverted on the retina4 ,the experiment succeeds also with the eye of a sheep or a cow1 if the sclerotic has been lessened4 ,the optic centre of the eye is the point where the secondary axes cross2 the optic axis passes through the geometrical axis of the organ1 and directs itself spontaneously towards the point that attracts the eye4 ,illustration3 ,fig4 #if4--;,diagram of mode of vision4 ,we will now point out in what distinct vision consists4 ,a screen placed behind a lens will only receive the image of a lighted object1 ,a ,b1 if placed in a position1 ,r ,r 7fig4 #if74 ,if placed nearer at ,r ,r1 or further off at ,r ,r1 the light from the object is thrown on the screen1 and the image is confused4 ,to prove the imperfection of sight which is shown by the application of these theoretic rules1 ,,mm4 ,boutan and d',almda#aj cite the following experiment3--,if the head of a pin is placed from one to two inches from the eye1 nothing will be perceived but a confused haziness of vague outline4 ,the distance of distinct vision is that at which an object of small dimensions may be placed to be plainly perceived4 ,this distance1 which averages fifteen inches1 varies with different individuals4 ,it can be determined for different sights by means of an apparatus constructed by ,lepot4 ,a white thread1 a1 is stretched horizontally on a dark board 7fig4 #ig74 ,we look at it by placing our eye at one end behind a little screen pierced with an aperture1 ,o2 it then appears much reduced in length1 but either nearer or farther off it seems to enlarge and swell1 having the appearance of a white surface1 becoming larger and larger in proportion as we move away from the point at which it is seen most distinctly4 ,in this manner we can easily obtain a measure of the distance of distinct vision4 ,one of the most remarkable properties of the eye consists in the faculty which this organ possesses of seeing different distances4 ,if we consider it as a dark chamber1 there is but one distance at which an object will be perfectly visible2 nevertheless a metal wire1 for example1 can be seen as well at a distance of seven1 as ten1 fifteen1 or twenty inches by good sights4 ,illustration3 ,fig4 #ig4--;,experiment for sight4 ,this faculty of accommodation in the eye is thus demonstrated3 we place two pins1 one in front of the other1 one eye only being open2 we first look at the nearest pin1 which appears confused if it is near the eye1 but by an effort of will the image becomes clear4 ,if1 while preserving the clearness of the image1 we then carry our attention to the second pin1 we find that it1 too1 presents a confused appearance4 ,if we make an effort to distinguish the contour of the second pin1 we at last succeed1 and the first once more appears ill-defined4 ,it is only since the experiments of ,m4 ,cramer and ,m4 ,helmholtz that the explanation of this phenomenon could have been given4 ,m4 ,cramer has succeeded in determining on the living eye the curved ray of the cornea1 and of the two surfaces of the crystalline lens4 ,in so doing he followed ,samson's method1 and observed the images thrown by a luminous object1 whose rays strike the different refracting surfaces of the eye4 ,a candle1 ,l 7fig4 #ih71 is placed before the eye1 ,o1 and throws as in a convex mirror a straight image of the flame1 ,a 7fig4 #ii74 ,the other portion of the light1 which has penetrated the pupil1 falls on the crystalline lens1 and produces likewise a second straight image1 ,b4 ,then the light refracted by the lens reaches the posterior surface2 a portion is reflected on a concave mirror1 and gives the inverted image1 ,c1 very small and brilliant4 ,m4 ,cramer observed it through a microscope1 and studied the variations in the size of images when the eye passed from the observation of adjacent to distant objects4 ,he stated3-- #a4 ,that the image1 ,a1 formed on the surface of the cornea1 remains the same size in both cases2 the form of the cornea therefore remains unaltered4 ,illustration3 ,fig4 #ih4--,m4 ,cramer's experiment4 ,illustration3 ,fig4 #ii4--;,images in the eye4 #b4 ,that the image1 ,b1 formed on the upper surface of the lens1 diminishes in proportion as the eye is nearer the object2 the surface therefore becoming more and more convex1 as the focal distance diminishes--a result indicated by the theory that it is possible in the vision of near objects to receive the image on the retina4 #c4 ,that the third image1 ,c1 produced on the posterior surface of the lens1 remains nearly invariable4 ,we may confirm ,cramer's statements by an easy experiment4 ,we place ourselves in front of the eye of someone who looks in turn at two objects placed on the same black line at unequal distances from him1 and are able to distinguish by the dimension of the images of the candle1 which object it is that he is regarding4 ,m4 ,helmholtz has carried ,m4 ,cramer's methods to perfection1 and has been able to formulate a complete theory of all the phenomena of accommodation4 ,the laws of optics show that the rays emitted by a luminous point may unite at another point by the action of the refracting surfaces of the eye4 ,nevertheless1 a white light being composed of rays of diverse refrangibility1 particular effects1 known under the name of chromatic aberration1 are produced through the decomposition of light1 which we will proceed to study1 under ,m4 ,helmholtz's auspices#aa4 ,we make a narrow opening in a screen1 and fix behind this opening a violet glass1 penetrable only by red and violet rays4 ,we then place a light1 the red rays of which reach the eye of the observer after having passed through the glass and the opening in the screen4 ,if the eye is adapted to the red rays1 the violet rays will form a circle of diffusion1 and a red point encircled with a violet aureola is seen4 ,the eye may also be brought to a state of refraction1 so that the point of convergence of the violet rays is in front1 and that of the red rays behind the retina1 the diameters of the red and violet circles of diffusion being equal4 ,it is then only that the luminous point appears monochromatic4 ,when the eye is in this state of refraction1 the simple rays1 whose refrangibility is maintained between the red and the violet rays1 unite on the retina4 ,there is another kind of aberration of luminous rays of one colour emitted through a hole1 which generally only approach approximately to a mathematical focus1 in consequence of the properties of refracting surfaces2 it is called aberration of sphericity4 ,the phenomena are as follows3-- ,illustration3 ,fig4 #ajj4 #a4 ,we take for our object a very small luminous point 7the hole made by a pin in some black paper1 through which the light passes71 and having also placed before the eye a convex glass1 if we are not near-sighted1 we fix it a little beyond the point of accommodation1 so that it produces on the retina a little circle of diffusion4 ,we then see1 instead of the luminous point1 a figure representing from four to eight irregular rays1 which generally differ with both eyes1 and also with different people4 ,we have given the result of ,m4 ,helmholtz's observations in fig4 #ajj2 a corresponds to the right eye1 and b to the left4 ,the outer edges of the luminous parts of an image1 produced in this way by a white light1 are bordered with blue2 the edges towards the centre are of a reddish yellow4 ,the writer adds that the figure appears to him to have greater length than breadth4 ,if the light is feeble1 only the most brilliant parts of the figure can be seen1 and several images of the luminous point are visible1 of which one is generally more brilliant than the others4 ,if1 on the other hand1 the light is very intense1--if1 for example1 the direct light of the sun passes through a small opening1--the rays mingle with each other1 and are surrounded by aureola of rays1 composed of numberless extremely fine lines1 of all colours1 possessing a much larger diameter1 and which we distinguish by the name of the aureola of capillary rays4 ,illustration3 ,fig4 #aja4 ,the radiating form of stars1 and the distant light of street-lamps belong to the preceding phenomena4 ,if the eye is accommodated to a greater distance than that of the luminous point1--and for this purpose1 if the luminous point itself is distant1 we place before the eye a slightly convex lens1--we see another radiating image appear1 which ,m4 ,helmholtz represents thus 7fig4 #aja73 at c as it is presented to the right eye1 and at d as seen by the left4 ,if the pupil is covered on one side1 the side opposite to the image of diffusion disappears2 that is to say1 that part of the retinal image situated on the same side as the covered half of the pupil4 ,this figure1 then1 is formed by rays which have not yet crossed the axis of the eye4 ,if we place the luminous point at a distance to which the eye can accommodate itself1 we see1 through a moderate light1 a small1 round1 luminous spot1 without any irregularities4 ,if the light1 on the contrary1 is intense1 the image is radiated in every position of accommodation1 and we merely find that on approaching nearer1 the figure which was elongated1 answering to a distant accommodation1 gradually diminishes1 grows rounder1 and gives place to the vertically elongated figure1 which belongs to the accommodation of a nearer point4 ,when we examine a slender1 luminous line1 we behold images developed1 which are easily foreseen1 if for every point of the line we suppose radiating images of diffusion1 which encroach on each other4 ,the clearest portions of these images of diffusion mingle together and form distinct lines1 which show multiplied images of the luminous line4 ,most persons will see two of these images2 some1 with the eyes in certain positions1 will see five or six4 ,illustration3 ,fig4 #ajb4 ,to show clearly by experiment the connection existing between double images and radiated images from points1 it is sufficient to make in a dark sheet of paper a small rectilinear slit1 and at a little distance from one end1 on a line with the slit1 a small round hole1 as shown at a in fig4 #ajb4 ,looking at it from a distance we shall see that the double images of the line have exactly the same distance between them that the most brilliant parts of the starred figure of diffusion have from the point1 and that the latter are in a line with the first1 as will be seen at b 7fig4 #ajb71 where in the image of diffusion of the luminous point1 we only see the clearest parts of star a of the figure4 ,on lighted surfaces1 to which the eye is not exactly accommodated1 multiplied images are often remarked through the passage from light to darkness being made by two or three successive steps4 ,a series of facts which have been collected under the title of irradiation1 and which show that brightly-lighted surfaces appear larger than they are in reality1 and that the dark surfaces which surround them appear diminished to a corresponding degree1 explains this by the circumstance that the luminous sensation is not proportional to the intensity of the objective light4 ,these phenomena affect very various appearances1 according to the form of respective figures2 they are generally seen with the greatest ease and intensity when the eye is not exactly accommodated to the object examined1 either by the eye being too near or too far off1 or by using a concave or convex lens1 which prevents the object being seen clearly4 ,irradiation is not completely wanting1 even when the accommodation is exact1 and we notice it clearly in very luminous objects1 above all when they are small2 small circles of diffusion increase relatively the dimensions of small objects much more than of large ones1 with regard to which1 the dimensions of the small circles of diffusion which the eye furnishes1 when properly accommodated1 become insensible4 ,illustration3 ,fig4 #ajc4--;,experiment #a4 #a4 ,luminous surfaces appear larger4 ,we can never judge exactly of the dimensions of a slit or small hole through which a bright light escapes2 it always appears to us larger than it really is1 even with the most exact accommodation4 ,similarly1 the fixed stars appear in the form of small luminous surfaces1 even when we make use of a glass which allows of perfect accommodation4 ,if a gridiron with narrow bars--the spaces intervening being exactly equal to the thickness of the bars--is held over a light surface1 the spaces will always appear wider than the bars4 ,with an inexact accommodation1 these phenomena are still more remarkable4 ,fig4 #ajc exhibits a white square on a black foundation1 and a black square on a white foundation4 ,although the two squares have exactly the same dimensions1 the white appears larger than the black1 unless with an intense light and an inexact accommodation4 ,illustration3 ,fig4 #ajd4--;,experiment #b4 #b4 ,two adjacent luminous surfaces mingle together4 ,if we hold a fine metallic wire between the eye and the sun1 or the light of a powerful lamp1 we shall cease to see it2 the lighted surfaces on all sides of the wire in the visual range pass one into the other1 and become mingled4 ,in objects composed of black and white squares1 like those of a draught-board 7fig4 #ajd71 the angles of the white squares join by irradiation1 and separate the black squares4 #c4 ,straight lines appear interrupted4 ,if a ruler is held between the eye and the light of a bright lamp or the sun1 we perceive a very distinct hollow on the edge of the ruler in the part corresponding to the light4 ,when one point of the retina is affected by a light which undergoes periodical and regular variations1 the duration of the period being sufficiently short1 there results a continuous impression1 like that which would be produced if the light given during each period were distributed in an equal manner throughout the whole duration of the period4 ,to verify the truth of this law1 we will make use of some discs1 such as that represented in fig4 #aje4 ,the innermost circle is half white and half black2 the middle circle has two quarters1 or half its periphery1 white1 and the outer circle has four eighths' white1 the rest being black4 ,if such a disc is turned round1 its entire surface will appear grey2 only it is necessary to turn it with sufficient force to produce a continuous effect4 ,the white may also be distributed in other ways1 and provided only that on all the circles of the disc the proportion of the angles covered with white is the same1 they will always exhibit the same grey colour4 ,instead of black and white we may make use of different colours1 and obtain the same resultant colour from all the circles1 when the proportion of the angles occupied by each of the colours in the different circles is the same4 ,illustration3 ,fig4 #aje4--;,disc which appears uniformly grey by reason of its rotation4 ,if we paint on a disc a coloured star1 which is detached from a foundation of another colour 7fig4 #ajf71 during the rapid rotation of the disc the centre affects the colour of the star2 the outer circle assumes that of the background1 and the intermediate parts of the disc present the continuous series of the resultant colours4 ,these results are in accordance with the theory of the mixture of colours4 ,illustration3 ,fig4 #ajf4--;,disc with a star painted on the background of another colour4 ,rotative discs1 which are so much used in experiments in optical physiology1 were employed for the first time by ,msschenbroeck2 the most simple is the top4 ,m4 ,helmholtz ordinarily uses a brass spinning-top1 which fig4 #ajg represents at a third the natural size4 ,it is set in motion by the hand1 and its quickness may be increased or moderated at will2 but it cannot be made to spin quicker than six rounds in a second2 this motion will be kept up for three or four minutes4 ,thus1 with a feeble movement of rotation1 a uniform luminous impression can only be obtained by dividing the disc into four or six sections1 on each of which we repeat the same arrangement of colours1 light1 and shade4 ,if the number of repetitions of the design is less1 we obtain1 with a bright light1 a more or less shot-coloured disc4 ,illustration3 ,fig4 #ajg4--,m4 ,helmholtz's top for studying the impression of light on the retina4 ,it is easy to place designs on the disc1 even when in motion1 or to make any desired modification1 by superposing on the first disc another disc with sectors1 of which we can vary the position by slightly touching it1 or even blowing on it1 thus producing during the rotation of the disc very varied modifications4 ,if1 for instance1 we place on a disc covered with blue and red sectors of equal size1 a black disc1 of which the sectors are alternately filled in or empty1 the disc1 as it turns round1 will appear blue if the black sectors of the upper disc exactly cover the red sectors of the lower disc2 and it appears red1 if1 on the contrary1 the blue sectors are covered with the black2 while in the intermediate positions we obtain different mixtures of red and white1 and during the rotation of the disc may vary the colour insensibly by a gentle touch4 ,by dividing the different sectors with broken or curved lines1 instead of straight ones1 we can produce an arrangement of coloured rings of great variety and beauty4 ,to give the top greater speed1 we set it in motion by drawing a string twined round its stem4 ,the simplest method1 as shown in fig4 #ajh1 consists in the employment of a handle similar to that of the ,german top4 ,it is a hollow cylinder of wood set into a handle with two circular holes2 and at right angles with these is a groove for the passage of the string4 ,the stem of the top is passed through the holes of the cylinder1 one end of the string is fixed in the small hole in the stem1 and is rolled round by turning the top in the hand4 ,the part of the stem on which the string is twisted becomes sufficiently thick for the top to remain suspended to the handle2 then holding it a little above the table1 and giving the string a powerful pull1 we set the top in motion1 and as the string unrolls it falls on the table1 where it will continue its rotation for some time4 ,the top represented in fig4 #aji is constructed so that the discs may be firmly pressed by the stem1 which is necessary in experiments for demonstrating ,newton's theory of the mingling of colours4 ,we make use for this purpose of a variety of discs1 made of strong paper of different sizes1 having an opening in the centre and a slit1 as in fig4 #aaj2 each of the discs is covered uniformly with a single colour2 and if two or more are superposed1 with their slits placed one over the other1 we obtain sectors1 the size of which we may vary at will1 so that we can modify in a continuous manner the proportions of the colours4 ,the most perfect construction is that of ,busold's chromatic top 7fig4 #aaa71 which should only be employed for very rapid rotations4 ,the disc1 which weighs #e lbs41 is made of an alloy of zinc and lead1 about an inch and a quarter in diameter4 ,the brass axis terminates at its lower end with a blunt point of untempered steel2 the cylindrical part of the axis is roughened to encourage the adherence of the string2 the axis is placed between the clamps of a vice1 and a plate is put underneath2 we then pull the string firmly with the right hand1 and when the top is in motion it is separated from the clamps4 ,by pulling the string very powerfully it is possible to obtain a speed of sixty turns in a second1 and the movement will be kept up for three quarters of an hour4 ,illustration3 ,fig4 #ajh4--,spinning a top with coloured discs4 ,illustration3 ,fig4 #aji4--,top for experiments demonstrating ,newton's theory of the mingling of colours4 ,illustration3 ,fig4 #aaj4--;,disc4 ,illustration3 ,fig4 #aaa4--;,busold's chromatic top4 ,besides tops1 we may make use of different kinds of discs1 with an axis rotating between two clamps2 they are moved either by a kind of clock-work1 or by the unrolling of a string1 like the tops4 ,generally1 however1 these contrivances have this inconvenience1 that the discs cannot be changed without stopping the instrument1 and partly taking it to pieces4 ,on the other hand1 we have the advantage of being able to turn them on a vertical plane1 so that we can conveniently carry on our experiments before a numerous auditory1 which is a more difficult matter with tops4 ,montigny contrived to obtain the mingling of colours by means of a turning prism1 which he caused to throw its shadow on a white screen4 ,the ,thaumatrope is a small rectangle of cardboard1 which is made to rotate on an axis passing through the centres of the longest sides4 ,we shall describe it at greater length when we come to consider a new apparatus known under the name of the ,praxinoscope4 ,more complicated contrivances have also been constructed on the same principle1 by which one may perceive the rotating disc through slits which turn at the same time4 ,we will now describe the construction of some discs invented by ,plateau under the name of the ,phenakistoscope4 ,these discs are made of strong cardboard1 from six to ten inches in diameter 7fig4 #aab71 on which a certain number of figures 7eight to twelve7 are placed in circles at an equal distance from each other1 presenting the successive phases of a periodical movement4 ,this disc is placed on another opaque circle of rather larger diameter1 which has on its margin as many openings as the first disc has figures4 ,the two discs are placed one on the other1 and are fixed in the centre by means of a screw at the anterior extremity of a small iron axis1 the other end being fitted into a handle4 ,to make use of this contrivance we place ourselves in front of the glass1 towards which we turn the disc with the figures1 placing the eye so as to see the figures through one of the holes of the large disc4 ,directly the apparatus begins to turn round1 the figures seen in the glass appear to execute the particular movements which they represent in different positions4 ,let us designate by means of the figures #a1 #b1 #c1 the different openings through which the eye successively looks1 and point out by the same numbers the figures in the radiuses thus numbered4 ,if the experimenter looks in the glass through opening #a1 he will see first figure #a1 which appears in the glass to pass before his eyes2 then the rotation of the disc displaces opening #a1 and the cardboard intervenes1 until opening #b appears2 then figure #b takes the place of figure #a1 until it in turn disappears1 and opening #c presents figure #c to view4 ,if these figures were all similar1 the spectator would have but a series of visual impressions1 separate but alike1 which by a sufficiently rapid rotation mingle together in one durable impression like a perfectly immovable object4 ,if1 on the contrary1 the figures differ slightly from each other1 the luminous sensations will also mingle in a single object1 which will however appear to be modified in a continuous manner1 conformably with the differences of successive images4 ,with a difference of speed1 we obtain a new series of phenomena4 ,a most simple contrivance of this kind is a top of ,c4 ,b4 ,dancer1 of ,manchester 7fig4 #aac74 ,it will be seen that the axis carries another disc1 pierced with openings of different shapes1 to the edge of which a thread is attached4 ,this second disc is carried along by the friction of the axis1 but its rotation is less rapid because of the great resistance offered by the air to the piece of thread which participates in the movement4 ,if the lower disc has several differently-coloured sectors1 they produce a very motley appearance1 which seems to move sometimes by leaps1 and sometimes by continuous motion4 ,we must distinguish between the phenomena of successive contrast and simultaneous contrast4 ,illustration3 ,fig4 #aab4--,rotating disc4 ,illustration3 ,fig4 #aac4--,mr4 ,dancer's top4 ,phenomena of successive contrast develop what are called accidental images4 ,if we fix our eyes for a considerable time on a coloured object1 and then suddenly direct them towards a uniform white surface1 we experience the sensation of the object as it is1 but it appears coloured with a complementary tint2 that is to say1 it has the colour which1 superposed on the genuine tint1 we obtain from pure white4 ,thus a red object produces a consecutive green object4 ,the experiment can be tried by gazing at the sun when it is setting1 and then directing one's eyes towards a white wall in the same direction4 ,phenomena of simultaneous contrast arise from the influence exercised over each other by different shades and colours which we see simultaneously4 ,that we may be certain that we have really obtained phenomena of this kind1 the experiments must be arranged in such a manner that accidental images are not produced1 and that the part of the retina affected by the sensation of colour does not receive1 even momentarily1 a passing image4 ,illustration3 ,fig4 #aad4--;,disc1 which exhibits1 when in rotation1 a series of concentric rings4 ,the phenomena of simultaneous contrast appear with the greatest clearness with slight differences of colour1 and are therefore exactly the contrary of phenomena of successive contrast1 which are favoured by strong oppositions of colour and light4 ,we can1 in general1 characterise phenomena of simultaneous contrast as governed by this law1 common to all perceptions of the senses3 the differences clearly perceived appear greater than the differences equal to them1 but perceived with greater difficulty1 either because they only affect the observation in an uncertain manner1 or that the memory fails to judge of them4 ,a man of middle height appears small beside a tall man1 because at the moment it is forcibly impressed on us that there are taller men than he1 and we lose sight of the fact that there are smaller4 ,the same man of medium height appears tall beside a man of small stature4 ,we can easily make experiments on simultaneous contrast with a sheet of transparent paper4 ,we fasten together a sheet of green and a sheet of rose-coloured paper1 so as to obtain a sheet half red and half green4 ,on the line of separation between the two colours we place a strip of grey paper1 and cover the whole with a sheet of thin letter-paper of the same size4 ,the grey strip will then appear red at the edge touching the green1 and green at the edge touching the red2 the centre presenting an intermediate shade4 ,it presents a still more decided appearance if the grey strip is perpendicular with the line of separation of the two colours2 the piece of grey then stretching into the green will present as deep a red as the red foundation on the other side4 ,if the line of grey colour exactly covers the line of separation between the two colours1 the contrasting colour is more feeble2 the edges of the grey paper then present complementary strips of colour4 ,similar effects may be obtained by superposing1 in gradually diminishing layers1 strips of thin paper1 so as to form successive bands of different thicknesses4 ,if it is then lit up from behind1 the objective intensity is evidently constant through the extent of each layer2 nevertheless every strip appears darker at the edge touching a more transparent layer1 and lighter at the edge in contact with a thicker layer4 ,the dull tints of ,china ink1 superposed in layers1 will produce a similar effect4 ,the phenomena are produced by means of rotative discs of most beautiful and delicate gradations of colour4 ,let us give the sectors of the disc the form represented by fig4 #aad1 and make them black and white2 and when in rotation we shall see a series of concentric rings of a shade that becomes darker and darker towards the centre4 ,the angular surface of the dark portions is constant in each of these rings4 ,the intensity1 therefore1 of each ring is uniform during rapid rotation2 it is only between one ring and another that the intensity varies4 ,each ring also appears lighter on its inner side when it borders on a darker ring1 and darker on its outer side when in contact with a lighter ring4 ,if the differences of intensity in the rings are very slight1 one can scarcely judge sometimes if the inner rings are darker than the outer2 the eye is only struck by the periodical alternations of light and shade presented by the edges of the rings4 ,if1 instead of white and black1 we take two different colours1 each ring will present two colours on its two edges1 although the colour of the rest of the ring will be uniform4 ,each of the constituent colours presents itself with more intensity on that edge of the ring which borders on another ring containing a smaller quantity of the colour4 ,thus1 if we mix blue and yellow1 and the blue predominates in the exterior and the yellow in the interior1 every ring will appear yellow at its outer1 and blue at its inner edge2 and if the colours present together very slight differences1 we may fall into the illusion which causes the differences really existing between the colours of the different rings to disappear1 leaving instead1 on a uniformly coloured background1 the contrasting blue and yellow of the edges of the rings4 ,it is very characteristic that in these cases we do not see the mixed colours1 but seem to see the constituent colours separately1 one beside the other1 and one through the other4 ,all the experiments we have described afford great interest to the student2 they can easily be performed by those of our readers who are particularly interested in these little-known subjects4 ,any one may construct the greater part of the appliances we have enumerated1 and others can be obtained at an optician's4 ,the discs in particular are extensively manufactured1 and with great success4 ,,footnotes3 #aj ,trait de ,physique1 ,paris #ahgd4 #aa ,trait d'optique ,physiologique4 ,french translation by ,,mm4 ,javal and ,klein4 ,,chapter ,,xi4 ,,optical ,,illusions--,,zollner',s ,,designs--,,the ,,thaumatrope--,,phenokistoscope--,,the ,,zootrope--,,the ,,praxinoscope--,,the ,,dazzling ,,top4 ,we shall now continue the subject by describing some illusions more curious still--those of ocular estimation4 ,these illusions depend rather on the particular properties of the figures we examine1 and the greater part of these phenomena may be placed in that category whose law we have just formulated3 the differences clearly perceived appear greater than the differences equal to them1 but perceived with greater difficulty4 ,thus a line ---- when divided appears greater than when not divided2 the direct perception of the parts makes us notice the number of the sub-divisions1 the size of which is more perceptible than when the parts are not clearly marked off4 ,thus1 in fig4 #aae1 we imagine the length ab equals bc1 although ab is in reality longer than bc4 ,in an experiment consisting of dividing a line into two equal parts1 the right eye tends to increase the half on the right1 and the left eye to enlarge that on the left4 ,to arrive at an exact estimate1 we turn over the paper and find the exact centre4 ,illustration3 ,fig4 #aae4 ,illustration3 ,fig4 #aaf4 ,illusions of this kind become more striking when the distances to be compared run in different directions4 ,if we look at ,a and ,b 7fig4 #aaf71 which are perfect squares1 ,a appears greater in length than width1 whilst ,b1 on the contrary1 appears to have greater width than length4 ,the case is the same with angles4 ,on looking at fig4 #aag1 angles #a1 #b1 #c1 #d are straight1 and should appear so when examined4 ,but #a and #b appear pointed1 and #c and #d obtuse4 ,the illusion is still greater if we look at the figure with the right eye4 ,if1 on the contrary1 we turn it1 so that #b and #c are at the bottom1 #a and #b will appear greatly pointed to the left eye4 ,the divided angles always appear relatively greater than they would appear without divisions4 ,the same illusion is presented in a number of examples in the course of daily life4 ,an empty room appears smaller than a furnished room1 and a wall covered with paperhangings appears larger than a bare wall4 ,it is a well-known source of amusement to present someone in company with a hat1 and request him to mark on the wall its supposed height from the ground4 ,the height generally indicated will be a size and a half too large4 ,we will relate an experience described by ,bravais3 8,when at sea10 he says1 8at a certain distance from a coast which presents many inequalities1 if we attempt to draw the coastline as it presents itself to the eye1 we shall find on verification that the horizontal dimensions have been correctly sketched at a certain scale1 while all the vertical angular objects have been represented on a scale twice as large4 ,this illusion1 which is sure to occur in estimates of this kind1 can be demonstrated by numerous observations40 ,m4 ,helmholtz has also indicated several optical illusions4 ,illustration3 ,fig4 #aag4 ,illustration3 ,fig4 #aah4 ,illustration3 ,fig4 #aai4 ,if we examine fig4 #aah1 the continuation of the line a does not appear to be d1--which it is in reality1--but f1 which is a little lower4 ,this illusion is still more striking when we make the figure on a smaller scale 7fig4 #aai71 as at ,b1 where the two fine lines are in continuation with each other1 but do not appear to be so1 and at ,c1 where they appear so1 but are not in reality4 ,if we draw the figures as at ,a 7fig4 #aah71 leaving out the line d1 and look at them from a gradually increasing distance1 so that they appear to diminish1 it will be found that the further off the figure is placed1 the more it seems necessary to lower the line f to make it appear a continuation of a4 ,these effects are produced by irradiation2 they can also be produced by black lines on a white foundation4 ,near the point of the two acute angles1 the circles of diffusion of the two black lines touch and mutually reinforce each other2 consequently the retinal image of the narrow line presents its maximum of darkness nearest to the broad line1 and appears to deviate on that side4 ,in figures of this kind1 however1 executed on a larger scale1 as in fig4 #aah1 irradiation can scarcely be the only cause of illusion4 ,we will continue our exposition as a means of finding an explanation4 ,in fig4 #abj1 ,a and ,b present some examples pointed out by ,hering2 the straight1 parallel lines1 a b1 and c d1 appear to bend outwards at ,a1 and inwards at ,b4 ,but the most striking example is that represented by fig4 #aba1 published by ,zollner4 ,the vertical black strips of this figure are parallel with each other1 but they appear convergent and divergent1 and seem constantly turned out of a vertical position into a direction inverse to that of the oblique lines which divide them4 ,the separate halves of the oblique lines are displaced respectively1 like the narrow lines in fig4 #aai4 ,if the figure is turned so that the broad vertical lines present an inclination of #de to the horizon1 the convergence appears even more remarkable1 whilst we notice less the apparent deviation of the halves of the small lines1 which are then horizontal and vertical4 ,the direction of the vertical and horizontal lines is less modified than that of the oblique lines4 ,we may look upon these latter illusions as fresh examples of the aforesaid rule1 according to which acute angles clearly defined1 but of small size1 appear1 as a rule1 relatively larger when we compare with obtuse or right angles which are undivided2 but if the apparent enlargement of an acute angle shows itself in such a manner that the two sides appear to diverge1 the illusions given in figs4 #aah1 #abj1 and #aba1 will be the result4 ,illustration3 ,fig4 #abj4--,the horizontal lines1 a1 b1 c1 d1 are strictly parallel2 their appearance of deviation is caused by the oblique lines4 ,in fig4 #aah the narrow lines appear to turn towards the point where they penetrate the thick line and disappear1 to appear afterwards in continuation of each other4 ,in fig4 #abj the two halves of each of the two straight lines seem to deviate through the entire length in such a manner that the acute angles which they form with the oblique lines appear enlarged4 ,the same effect is shown by the vertical lines of fig4 #aba4 ,m4 ,helmholtz is of opinion 7figs4 #abj1 #aba7 that the law of contrast is insufficient to entirely explain the phenomena1 and believes that the effect is also caused by the movements of the eye4 ,in fact1 the illusions almost entirely disappear1 if we fix on a point of the object in order to develop an accidental image1 and when we have obtained one very distinctly1 which is quite possible with ,zollner's design 7fig4 #aba71 this image will present not the slightest trace of illusion4 ,in fig4 #aah the displacement of the gaze will exercise no very decided influence on the strengthening of the illusion2 on the contrary1 it disappears when we turn our eyes on the narrow line1 ad4 ,on the other hand1 the fixing of the eyes causes the illusion to disappear with relative facility in fig4 #abj1 and with more difficulty in fig4 #aba2 it will1 however1 disappear equally in the latter design1 if we fix it immovably1 and instead of considering it as composed of black lines on a white background1 we compel ourselves to picture it as white lines on a black foundation2 then the illusion vanishes4 ,but if we let our eyes wander over the illustration1 the illusion will return in full force4 ,we can indeed succeed in completely destroying the illusion produced by these designs by covering them with a sheet of opaque paper1 on which we rest the point of a pin4 ,looking fixedly at the point1 we suddenly draw away the paper1 and can then judge if the gaze has been fixed and steady according to the clearness of the accidental image which is formed as a result of the experiment4 ,illustration3 ,fig4 #aba4--,the vertical strips are parallel2 they appear convergent or divergent under the influence of the oblique lines4 ,illustration3 ,fig4 #abb4--,observation of electric spark4 ,the light of an electric spark furnishes the surest and simplest means of counteracting the influence of movements of the eyes1 as during the momentary duration of the spark the eye cannot execute any sensible movement4 ,for this experiment the present writer has made use of a wooden box1 ,a ,b ,c ,d 7fig4 #abb71 blackened on the inside4 ,two holes are made for the eyes on each side of the box1 f and g4 ,the observer looks through the openings1 f1 and in front of openings1 g1 the objects are placed2 these are pierced through with a pin1 which can be fixed by the eyes in the absence of the electric spark1 when the box is perfectly dark4 ,the box is open1 and rests on the table1 ,b ,d1 to allow of changing the object4 ,the conducting wires of electricity are at h and i2 in the centre of the box is a strip of cardboard1 white on the side facing the spark1 the light of which it shelters from the eye of the observer and throws back again on the object4 ,with the electric light the illusion was completely perceptible with fig4 #aah1 while it disappeared altogether in fig4 #abj2 with fig4 #aba it was not entirely absent1 but when it showed itself1 it was much more feeble and doubtful than usual1 though the intensity of light was quite sufficient to allow of the form of the object being very distinctly examined4 ,thus two different phenomena have to be explained2 first1 the feeble illusion which is produced without the intervention of movements of the eye2 and secondly1 the strengthening of the illusion in consequence of these movements4 ,the law of contrast sufficiently explains the first2 that which one perceives most distinctly with indirect vision is the concordance of directions with dimensions of the same kind4 ,we perceive more distinctly the difference of direction presented at their intersection by the two sides of an acute or obtuse angle1 than the deviation that exists between one of the sides and the perpendicular which we imagine placed on the other side1 but which is not marked4 ,by being distributed on both sides1 the apparent enlargement of the angles gives way to displacements1 and changes of direction of the sides4 ,it is difficult to correct the apparent displacement of the lines when they remain parallel to their true direction2 for this reason1 the illusion of the figure is relatively more inflexible4 ,changes of direction1 on the contrary1 are recognised more easily if we examine the figure attentively1 when these changes have the effect of causing the concordance of the lines 7which accord in reality7 to disappear2 it is probably because of the difference in aspect of the numerous oblique lines of figs4 #abj and #aba that the concordance of these lines escapes the observer's notice4 ,as regards the influence exercised by the motion of the eyes in the apparent direction of the lines1 ,m4 ,helmholtz1 after discussing the matter very thoroughly1 proves the strengthening of the illusion in ,zollner's illustration to be caused by those motions4 ,it is not now our intention to follow out the whole of this demonstration2 it will be sufficient to point out to the reader a fruitful force of study1 with but little known results4 ,the ,romans were well acquainted with the influence of oblique lines4 ,at ,pompeii1 fresco paintings are to be found1 in which the lines are not parallel1 so that they satisfy the eye influenced by adjacent lines4 ,engravers in copper-plate have also studied the influence of etchings on the parallelism of straight lines1 and they calculate the effect that they will produce on the engraving4 ,in some ornamentations in which these results have not been calculated1 it sometimes happens that parallel lines do not appear parallel because of the influence of other oblique lines1 and a disagreeable effect is produced4 ,a similar result is to be seen at the railway station at ,lyons1 the roof of which is covered with inlaid work in point de ,hongrie4 ,the wide parallel lines of this ceiling appear to deviate1 a result produced by a series of oblique lines formed by the planks of wood4 ,illustration3 ,fig4 #abc4--,two sides of a ,thaumatrope disc4 ,having given a long account of the result of ,m4 ,helmholtz's labours1 we will pass to the consideration of another kind of experiments1 or rather appliances1 based on the illusions of vision1 and the persistence of impressions on the retina4 ,the ,thaumatrope1 to which we have already referred1 is a plaything of very ancient origin1 based on the principle we have mentioned4 ,it consists of a cardboard disc1 which we put in motion by pulling two cords4 ,on one side of the disc a cage1 a1 is portrayed1 on the other a bird1 b 7fig4 #abc74 ,when the little contrivance is turned round1 the two designs are seen at the same time1 and form but one image--that of a bird in its cage 7fig4 #abd74 ,it is of course hardly necessary to add that the designs may be varied4 ,we have already referred to ,m4 ,plateau's rotating disc 7the ,phenakistoscope74 ,through the narrow slits we perceive in succession representations of different positions of a certain action4 ,the persistence of the luminous impressions on the retina gives to the eye the sensation of a continuous image1 which seems animated by the same movements as those portrayed in the different phases 7fig4 #abe74 ,illustration3 ,fig4 #abd4--;,appearance of the ,thaumatrope in rotation4 ,illustration3 ,fig4 #abe4--,plateau's ,phenokistoscope4 ,the ,zootrope 7fig4 #abf7 is a perfected specimen of this apparatus4 ,it is composed of a cylinder of cardboard1 turning on a central axis4 ,the cylinder is pierced with vertical slits at regular intervals1 and through which the spectator can see the designs upon a band of paper adapted to the interior of the apparatus in rotation4 ,the designs are so executed that they represent the different times of a movement between two extremes2 and in consequence of the impressions upon the retina the successive phases are mingled1 so the spectator believes he sees1 without transition1 the entire movement4 ,we give a few specimens of the pictures for the ,zootrope 7fig4 #abg74 ,we have here an ape leaping over a hedge1 a dancing 8,punch10 a gendarme pursuing a thief1 a person holding the devil by the tail1 a robber coming out of a box1 and a sportsman firing at a bird4 ,the extremes of the movement are right and left2 the intermediary figures make the transitions1 and they are usually equal in number to the slits in the ,zootrope4 ,it is not difficult to construct such an instrument1 and better drawings could be made than the specimens taken at random from a model4 ,the earth might be represented turning in space1 or a fire-engine pumping water could be given1 and thus the ,zootrope might be quite a vehicle of instruction as well as of amusement4 ,this instrument is certainly one of the most curious in the range of optics1 and never fails to excite interest4 ,the ingenious contrivances which have up to the present time reproduced it1 all consist in the employment of narrow slits1 which besides reducing the light to a great extent1 and consequently the light and clearness of the object1 require the instrument to be set in rapid rotation1 which greatly exaggerates the rapidity of the movements represented1 and without which the intermissions of the spectacle could not unite in a continuous sensation4 ,illustration3 ,fig4 #abf4--,the ,zootrope4 ,illustration3 ,fig4 #abg4--,pictures used in the ,zootrope4 ,we present here an apparatus based on a very different optical arrangement4 ,in the ,praxinoscope#ab 7a name given by the inventor1 ,mr4 ,reynaud1 to this new apparatus71 the substitution of one object for another is accomplished without interruption in the vision1 or solution of continuity1 and consequently without a sensible reduction of light2 in a word1 the eye beholds continuously an image which1 nevertheless1 is incessantly changing before it4 ,the result was obtained in this manner4 ,having sought unsuccessfully by mechanical means to substitute one object for another without interrupting the continuity of the spectacle1 the inventor was seized with the idea of producing this substitution1 not with the objects themselves1 but with their virtual images4 ,he then contrived the arrangement which we will now describe4 ,a plane mirror1 ,,ab 7fig4 #abi71 is placed at a certain distance from an object1 ,,cd1 and the virtual image will be seen at ,c,d4 ,if we then turn the plane mirror and object towards the point1 ,o1 letting ,,be and ,,df be their new positions1 the image will be at ,c,d4 ,its axis1 ,o1 will not be displaced4 ,in the positions1 ,,ab and ,,cd1 first occupied by the plane mirror and the object1 we now place another mirror and object4 ,let us imagine the eye placed at ,m4 ,half of the first object will be seen at ,,od1 and half of the second at ,,oc4 ,if we continue the rotation of the instrument1 we shall soon have mirror ,no4 #b at ,,tt1 and object ,no4 #b at ,,ss4 ,at the same moment the image of object ,no4 #b will be seen entirely at ,c,d4 ,mirror ,no4 #b and its object will soon after be at ,,be and ,,df4 ,if we then imagine another mirror and its corresponding object at ,,ab and ,,cd1 the same succession of phenomena will be reproduced4 ,this experiment therefore shows that a series of objects placed on the perimeter of a polygon will be seen successively at the centre1 if the plane mirrors are placed on a concentric polygon1 the 8apothme0 of which will be less by one-half1 and which will be carried on by the same movement4 ,in its practical form1 ,m4 ,reynaud's apparatus consists of a polygonal or simply circular box 7fig4 #abh71 7for the polygon may be replaced by a circle without the principle or result being changed71 in the centre of which is placed a prism of exactly half a diameter less1 the surface of which is covered with plane mirrors4 ,a strip of cardboard bearing a number of designs of the same object1 portrayed in different phases of action1 is placed in the interior of the circular rim of the box1 so that each position corresponds to a plate of the glass prism4 ,a moderate movement of rotation given to the apparatus1 which is raised on a central pivot1 suffices to produce the substitution of the figures1 and the animated object is reflected on the centre of the glass prism with remarkable brightness1 clearness1 and delicacy of movement4 ,constructed in this manner1 the ,praxinoscope forms an optical toy both interesting and amusing4 ,in the evening1 a lamp placed on a support ad hoc1 in the centre of the apparatus1 suffices to light it up very clearly1 and a number of persons may conveniently assemble round it1 and witness the effects produced4 ,illustration3 ,fig4 #abh4--,m4 ,reynaud's ,praxinoscope4 ,illustration3 ,fig4 #abi4 ,besides the attractions offered by the animated scenes of the ,praxinoscope1 the apparatus may also be made the object of useful applications in the study of optics4 ,it permits an object1 a drawing1 or a colour1 to be substituted instantaneously in experiments on secondary or subjective images1 etc41 on the contrast of colours or the persistence of impressions1 etc4 ,we can also make what is called a synthesis of movements by placing before the prism a series of diagrams of natural objects by means of photography4 ,m4 ,reynaud has already arranged an apparatus which exhibits in the largest dimensions the animated reflection of the ,praxinoscope1 and which lends itself to the demonstration of curious effects before a numerous auditory4 ,the ingenious inventor has recently contrived also a very curious improvement in the original apparatus4 ,in the ,praxinoscope ,theatre he has succeeded in producing truly ornamental tableaux1 as on a small ,lilliputian stage1 in the centre of which the principal object moves with startling effect4 ,to obtain this result1 ,m4 ,reynaud commences by cutting out in black paper the different figures1 the whole of which will form an object animated by the rotation given to the ,praxinoscope4 ,to supply the decorations1 he arranges on the black foundation the image of an appropriate coloured design by means of a piece of glass4 ,it is well known that transparent glass possesses the property of giving a reflection of the objects on the nearest side as well as on the farthest4 ,we may recall the applications of this optical effect in theatres1 and also in courses of physics1 under the title of impalpable spectres4 ,it is also by reflection on thin1 transparent glass1 that ,m4 ,reynaud produces the image of the ornamentations in the ,praxinoscope ,theatre4 ,the decorations are really placed in the lid1 which is held by a hook in a vertical position1 thus forming the front side of the apparatus 7fig4 #acj74 ,in this side a rectangular opening is made1 through which the spectator 7using both eyes7 perceives at the same time the animated reflection of the ,praxinoscope1 and the immovable image of the decorations reflected in the transparent glass4 ,the position of the latter and its distance from the coloured decorations are arranged so that the reflection is thrown behind the moving figure1 which consequently appears in strong relief against the background1 the effect produced being very striking4 ,it is evident that to change the decorations it is only necessary to place in succession on a slide the different chromos representing landscapes1 buildings1 the interior of a circus1 etc4 ,it is easy to choose an arrangement suitable for each of the moving figures placed in the ,praxinoscope4 ,by this clever and entirely novel optical combination1 the mechanism of the contrivance is entirely lost sight of1 leaving only the effect produced by the animated figures1 which fulfil their different movements on the little stage4 ,the ,praxinoscope ,theatre can also be used as well in the evening as in the daytime4 ,by daylight1 it is sufficient to place it before a window1 and in the evening the same effects may be produced1 perhaps in even a more striking manner1 by simply placing a lamp on the stand1 with a small plated reflector1 and a lamp-shade4 ,the illusion produced by this scientific plaything is very complete and curious1 and ,m4 ,reynaud cannot be too much commended for so cleverly applying his knowledge of physics in the construction of an apparatus which is at the same time both an optical instrument and a charming source of amusement4 ,illustration3 ,fig #acj4--,the ,praxinoscope ,theatre4 ,illustration3 ,fig4 #aca4--,the ,dazzling ,top4 ,amongst the toys founded upon the persistency of impressions upon the retina we may instance the 8,dazzling ,top0 7fig4 #aca74 ,this remarkable invention is quite worthy of a place in every cabinet1 and is an ingenious specimen of a perfected ,helmholtz top4 ,it is a metallic toy put in motion by means of a cord wound round a groove4 ,the axis is hollow1 admits a metallic stem1 and fits into a handle which is held in the hand4 ,the top is placed upon a little cup in an upright position1 and it is then set spinning in the usual way with the cord4 ,the stem and handle are then withdrawn1 and as the top will continue to spin for a long time1 discs and various outline shapes can be fixed upon it1 and various objects will be shadowed thereon4 ,cups1 bowls1 candlesticks1 and jugs can be seen plainly revolving as the top carries the wire representation in outline rapidly past the eyes4 ,coloured cardboard can be worked into various patterns1 and much amusement will be created amongst children and young people4 ,,footnotes3 #ab ,from praxis1 action1 and skopein1 to show4 ,,chapter ,,xii4 ,,optical ,,illusions ,,continued--,,experiments--,,the ,,talking ,,head--,,ghost ,,illusions4 ,the enumeration of optical illusions is so considerable that we have no intention of describing them all1 and will merely cite a few other examples4 ,the following facts have been communicated to us by ,m4 ,nachet3-- ,illustration3 ,fig4 #acb4--;,hexagonal appearance formed by circles joined together4 ,when examining alg under the microscope1 we notice the spaces which separate the streaks ornamenting the silicious covering of these various organisms1 and it is explained that they are formed by hexagons visible only when we examine the object with a powerful microscope4 8,for a long time10 says ,m4 ,nachet1 8,i occupied myself with the examination of the hexagonal appearance of the points constituting the streaks4 ,why should these hexagons show themselves1 and how could they be other than the visible base of small pyramids piled very closely one on the other2 and if this were the case1 why were not the points of the little pyramids visible8 ,or1 was the structure before me analogous to that of the eyes of insects8 ,then the carapace would be but a surface of perforated polygonal openings4 ,this latter hypothesis was attractive enough1 and would have explained many things2 but some careful observations with very powerful object-glasses1 quite free from blemishes1 had shown me that these hexagons had round points1 contrary to the descriptions of micrographs4 ,these observations1 corroborated by the micrographic photographs of ,lackerbauer1 the much-regretted designer1 and by ,colonels ,woodward and ,washington1 left not the slightest doubt that it was necessary to discover why the eye persistently saw hexagons where there were circles4 ,to elucidate this point1 it was necessary to find some means of reproducing artificially what nature had accomplished with so much precision on the surfaces of alg4 ,after many fruitless attempts1 ,i decided on making a trial of a stereotype plate covered with dots arranged in quincunxes1 very close together0 7figs4 #acb and #acc74 8,the result was more successful than ,i had hoped2 the effect produced is exactly that of the arrangement of the so-called hexagons of the most beautiful of the alg1 the ,pleurosigma angulata4 ,if these stereotypes are examined with one eye only1 we shall be immediately convinced that we have to do with hexagonal polygons40 ,it is useless to give any long exposition of a figure so clearly explanatory2 it is simply an effect of the contrast and opposition of the black and white in the sensation of the retina4 ,this effect is particularly striking with fig4 #acd1 a negative photograph heliographically engraved according to fig4 #acc4 ,in this the white points seem to destroy the black spaces1 and to approach each other tangentially1 and the irradiation is so intense that the white circles appear much larger than the black of fig4 #acc1 although of the same diameter4 ,there are in these facts many points which may interest not only students of micrography1 but also artists4 ,as to the alg1 the origin of this investigation1 it remains to be discovered if these circles which cover their silicious carapace are the projection of small hemispheres1 or the section of openings made in the thick covering4 ,certain experiments1 however1 seem to prove that they are hemispheres1 and the theory is also confirmed by a microscopic photograph from ,lackerbauer's collection1 magnified #c1jjj diameters1 in which a black central point is seen in the centre of each circle1 a certain reflection of the luminous source reproduced in the focus of each of the small demi-spheres which constitute the ornament of the alg4 ,the microscope1 which has progressively shown first the streaks1 then the hexagons1 and then the round points1 will surely clear up the point some day or other4 ,illustration3 ,fig4 #acc4--;,another figure of the same kind4 ,illustration3 ,fig4 #acd4--,third figure4 ,mr4 ,silvanus ,p4 ,thompson1 ,professor of ,physics at ,university ,college1 ,bristol1 has recently presented the ,french ,society of ,physical ,science with a curious example of optical illusion1 the true cause of which is not clearly known1 but which we may compare with other facts made known some time ago1 of which no precise explanation has been given4 ,let us first consider in what the effect discovered by ,mr4 ,s4 ,p4 ,thompson consists1 according to the description that has been given of it by ,m4 ,c4 ,m4 ,gariel2 the illustrations here given will also allow of our verifying the truth of the statements4 ,illustration3 ,fig4 #ace4 ,fig4 #acf4 ,mr4 ,thompson's optical illusion4 ,give a circular movement to these figures1 and the circles will appear to turn round4 ,the first illustration consists of a series of concentric circles of about the width of a millimetre1 separated by white intervals of the same size 7fig4 #ace74 ,these dimensions are not absolute2 they vary with the distance1 and may even be a few inches in width if it is desired to show the phenomenon to a rather numerous auditory4 ,if we hold the design in the hand1 and give it a twirl by a little movement of the wrist1 the circle appears to turn round its centre1 and the rotation is in the same direction1 and is equally swift2 that is to say1 the circle appears to accomplish a complete turn1 whilst the cardboard really accomplishes one in the same direction4 ,for the second effect we draw a dark circle1 in the interior of which are placed a number of indentations at regular intervals 7fig4 #acf74 ,operating in the same manner as described above1 this notched wheel appears to turn round its centre1 but this time in a different direction from the real movement4 ,in this1 however1 as in the other design1 the effect is more satisfactory if we do not look directly at it2 the movements also are particularly striking in combinations such as that represented in fig4 #acg1 in which the multiplicity of circles does not allow us to fix one specially4 ,we may add that the same effects may be obtained with eccentric wheels1 or even with other curves than circles4 ,by means of a photograph on glass1 ,mr4 ,thompson has been able to reflect these designs on a screen where they were obtained on a large scale2 a circular movement was communicated to the photographic plate1 so that the design moved in a circular manner on the screen1 and in this case also there existed the illusion that every circle seemed turning round its centre4 ,and what is the explanation of these curious effects8 ,mr4 ,thompson does not believe 7and we share his opinion7 that the faculty possessed by the retina of preserving images during a certain time 7persistence of impressions on the retina7 can entirely explain these phenomena4 ,without desiring to formulate a decided theory1 ,mr4 ,thompson is of opinion that we may class these facts with others which have been known for some time1 and that perhaps it is necessary to attribute to the eye some new faculty which may explain the whole at once4 ,illustration3 ,fig4 #acg4--;,another figure of ,mr4 ,thompson's4 ,the different circles appear to turn round if we give the design a rotating movement4 ,brewster and ,adams have described phenomena which are equally curious1 the principal of which we will describe1 adding also some analogous investigations due to ,mr4 ,thompson4 ,the result seems to be that there exists in the eye a badly-defined purpose of nature1 which in a certain way compensates 7,brewster7 for the real phenomenon1 because it has a contrary effect1 which will continue for some time after the cessation of the phenomena1 and which gives by itself a sensation contrary to that which the real movement would have produced4 ,thus1 after having fixed our eyes for two or three minutes on a rushing waterfall1 if we suddenly turn our glance on the adjacent rocks1 the latter appear to move from top to bottom4 ,it is not a question here of the effect of the relative movement to be observed on regarding simultaneously the falling water and the rocks2 if one can succeed in abstracting oneself to such an extent that the water appears motionless1 the rocks appear to take a contrary movement4 ,in the phenomenon we describe there is no simultaneous comparison2 the eyes are turned successively first on the water1 and then on the rocks4 ,in a rapid river1 such as the ,rhine above the fall at ,schaffhausen1 the stream is not equally swift in every part1 and the current is noticeably more rapid in the middle of the river than near the banks4 ,if we look fixedly at the centre of the stream1 and then suddenly turn our eyes towards the banks1 it will appear as though the river were flowing back towards its source4 ,this kind of compensation does not only produce an apparent displacement1 but also changes in size4 ,when travelling at great speed in a railway train1 the objects of the surrounding country as one flies by them gradually appear smaller and smaller4 ,if1 when this occurs1 we suddenly remove our eyes to the interior of the railway carriage1 and fix them on immovable objects1 such as the sides of the compartment1 or the faces of our travelling companions1 the images on the retina will really preserve the same size1 and yet the objects will appear larger4 ,such are some of the interesting facts among those discovered by ,mr4 ,thompson2 and though we do not intend to push the inquiry further1 we think it may not be without interest to describe here another illusion of that organ whose properties are in every way so curious and remarkable4 ,illustration3 ,fig4 #ach4--;,experiment on complementary colours4 ,illustration3 ,fig4 #aci4--;,design for experiment or the punctum ccum4 ,another experiment to show the existence of impressions received by the retina can be made with the figure above 7#ach74 ,if the gaze be fixed upon the dark spot in the centre of the white figure for about half a minute1 and the eyes then directed to the ceiling1 or a sheet of white paper1 the white figure will be reproduced in black4 ,this result is based upon the principle of complementary colours4 ,a red design1 for instance1 will be reproduced in green4 ,there is a dark spot in every human eye--that is1 a spot which is insensible to light4 ,the eye is generally regarded as a perfect instrument1 but it is not yet so by any means4 ,one of our great philosophers remarked that if an instrument were sent home to him so full of errors he would feel justified in returning it to the optician4 ,but the eye has its dark place1 the punctum ccum1 and it can be discovered by covering the left eye with the hand1 and holding the present page at arm's length with the other4 ,then fix the gaze on the small cross in the picture1 and bring the book close up4 ,at a little distance the white ball will disappear from the page 7fig4 #aci74 ,illustration3 ,fig #adj4--;,an optical illusion4 ,the illustration 7fig4 #adj7 shows us a very curious optical illusion1 and one very easy to practise4 ,roll up a sheet of paper1 and look through it1 as through a telescope1 with the right eye1 keeping both eyes open4 ,then place the left hand open palm towards you against the roll of paper1 you will then appear to be looking through a hole in your left hand4 ,sometimes the effect is produced without holding up the other hand to the roll1 as shown in fig4 #adj4 ,among optical illusions there are a great number that may be produced by means of mirrors4 ,the divided telescope is an example4 ,the apparatus1 raised on a firm stand1 allows of one apparently seeing an object through a stone or other opaque object1 as shown in fig4 #ada4 ,the illustration shows the arrangement of the apparatus4 ,the observer1 looking through it1 plainly perceives the object through the glass2 the image is reflected four times before reaching his eye1 by means of small mirrors concealed in the instrument4 ,illustration3 ,fig4 #ada4--;,a divided telescope4 ,convex or concave mirrors distort images in a singular manner1 and produce very interesting effects4 ,anamorphoses constitute particular objects belonging specially to the class of experiments relating to cylindrical mirrors4 ,they are images made according to determined rules1 but so distorted that when regarding them fixedly we can only distinguish confused strokes4 ,when they are seen reflected in the curved mirrors1 they present1 on the contrary1 a perfectly regular appearance4 ,fig4 #adb exhibits an ,anamorphosis made by a cylindrical mirror4 ,it will be seen that the confused image of the horizontal paper is reflected in the cylindrical mirror1 producing the figure of a juggler4 ,it is easy to contrive similar designs one's-self2 and comical mirrors may also be employed which produce particular effects of a no less interesting kind4 ,the next illustration is of a set of figures which in a cylindrical mirror look like the ten of hearts 7fig4 #adc74 ,illustration3 ,fig4 #adb4--;,cylindrical ,mirror and ,anamorphosis4 ,illustration3 ,fig4 #adc4--;,anamorphus design for the ten of hearts4 ,one of the most remarkable applications of mirrors in amusing experiments is undoubtedly that of the severed and talking head4 ,a few years back this trick obtained considerable success in ,paris and a number of other towns4 ,the spectators beheld a small space set apart1 in which was placed a table on three legs2 on this table was a human head1 placed in cloth on a dish4 ,the head moved its eyes and spoke2 it evidently belonged to a man whose body was completely hidden4 ,the spectators thought they saw an empty space beneath the table1 but the body of the individual who was really seated there was concealed by two glasses placed at an inclination of #de to the walls on the right and left4 ,the whole was arranged in such a manner that the reflection of the walls coincided with the visible part of the wall at the back of the room4 ,the three walls were painted in one colour1 and a subdued light increased the illusion1 the effect of which was remarkable 7fig4 #add74 ,illustration3 ,fig4 #add4--,the talking head4 ,the spectres designed by ,robin also attracted considerable public attention within recent times4 ,they were images formed by the medium of transparent glass4 ,glass panes often produce the phenomenon of spectres4 ,in the evening1 when it is dark out of doors1 it is easy to prove that the reflection of objects in a lighted room can be reproduced behind the window panes by reason of the darkness outside4 ,if we approach the window pane1 we see also the real objects outside1 a balcony1 tree1 etc4 ,these real objects mingle with the reflected image1 and combine to produce very curious effects4 ,in this way ,m4 ,robin has contrived the effects of the theatre4 ,he throws on the stage the reflection of a person dressed as a ,zouave1 and he himself1 armed with a sabre1 stabs the spectre through the body4 ,a great number of other singular effects have been obtained in the same manner4 ,pepper's ,ghost was managed in this way4 ,illustration3 ,fig4 #ade4--,the ghost effect4 ,within recent times1 images produced in a similar way have been utilized to facilitate the study of drawing4 ,a piece of glass is fixed vertically on a black board 7fig4 #adf74 ,a model to copy from is placed on one side of the piece of glass1 and is arranged so that the visual ray passes obliquely through the glass1 and we perceive the reflection of the design very clearly on the other side4 ,it is then very easily reproduced with a pencil on a sheet of white paper by tracing the outlines4 ,illustration3 ,fig4 #adf4--;,drawing by reflection4 ,,chapter ,,xiii4 ,,vision--,,the ,,eye--,,the ,,stereoscope--,,spectrum ,,analysis--,,the ,,spectroscope--,,the ,,telescope ,,and ,,microscope--,,photography--,,dissolvin g ,,views--,,luminous ,,paint4 ,the eye and vision are such important subjects to all of us that we may be excused for saying something more concerning phenomena connected with them1 and the instruments we use for assisting them4 ,we do not propose to write a treatise upon the physiology of vision1 for we know the image in the eye is produced physically in the same manner as the image in a camera obscura4 ,in the eye the sides of the box are represented by the sclerotic 7see chap4 x4 fig4 #ie72 the dark inner surface has its parallel in the pigment of the choroid2 the opening in the box in the pupil of the eye2 the convex lens in the crystalline and the cornea2 and the retina receives the image4 ,but why we see--beyond the fact that we do see--no one can explain4 ,science is dumb on the subject4 ,thought and consciousness elude our grasp2 and1 as ,professor ,tyndall says on this subject1 8we stand face to face with the incomprehensible40 ,but there are many interesting facts connected with our vision which may be plainly described4 ,some people are obliged to carry an object 7or a book7 to within ten inches of the eye to see it distinctly2 and a person who does not possess convergent power of the eye will have to move it farther off1 or use convex glasses2 while a 8near-sighted0 person1 whose eyes are too quickly convergent1 will use concave glasses to bring the object near to the eye4 ,there is but one small place in the retina of the eye which admits of perfect vision4 ,this1 the most sensitive portion1 is called the 8yellow spot10 and vision becomes more and more indistinct from this point towards the circumference4 ,this can be proved by any one2 for in reading we are obliged to carry our eyes from word to word1 and backwards and forwards along the lines of print4 ,another very important element in our vision is the contraction and enlargement of the iris around the pupil4 ,in cases where strong light would only dazzle us the iris expands1 and the pupil is contracted to a sufficient size to accommodate our vision4 ,at night1 or in a darkened room1 the pupil is enlarged4 ,this change will account for our not being immediately able to see objects when we have passed from darkness to great light1 or vice vers4 ,the iris must have time to accommodate itself to the light4 ,now1 outside the small space of perfect vision above mentioned1 there is a circle of considerable extent1 called the 8field of vision40 ,in man this field1 when the eyes are fixed1 subtends an angle of about #ahj1 because beyond that the rays cannot enter the pupil of the eye4 ,but in the lower animals1 the fish and birds1--notably the ostrich1--the field of vision is much more extensive1 because the pupils are more prominent1 or the eyes are set more towards the sides of the head4 ,the ostrich can see behind him1 and fish can see in any direction without apparent limit4 ,man can only see indistinctly2 and though he can move his eyes rapidly1 he can see distinctly but a small portion of any object at a time1 yet he sees with both eyes simultaneously a single object1 because the two lines of vision unite at a single point1 and as the two images cover each other we perceive only one image4 ,beyond or within this point of meeting the vision is indistinct1 but the angle of convergence is always varied according to the distance of the object4 ,if we hold up a penholder in front of us1 and in a line with any other defined object1--say an ink-bottle1--we can see the penholder distinctly1 and the ink-bottle indistinctly1 as two images4 ,if we then look at the ink-bottle we shall see it single1 while the penholder will appear double1 but with imperfect outlines4 ,illustration3 ,fig4 #adg4--,the ,stereoscope4 ,illustration3 ,fig4 #adh4--,mode of taking photograph for ,stereoscope4 ,again1 if we look at a box both eyes will see it equally well1 but the right eye will see a little more on its right side1 and the left eye on the left4 ,it is on this principle that the ,stereoscope is constructed4 ,sir ,charles ,wheatstone was the inventor1 and the instrument may be thus described3--,two pictures are taken by photography--one as the landscape is seen by the right eye1 the other as it is viewed by the left2 the points of view thus differing slightly4 ,when both eyes are simultaneously applied to the instrument the view is seen exactly as it would appear to the beholder at the actual place it represents4 ,the views are taken singly2 one side at one time1 and another after1 as in the camera 7fig4 #adh74 ,a is the first view2 ,b is kept dark2 ,c is the shutter for ,a4 ,there are ,reflecting and ,refracting ,stereoscopes4 ,in the former a mirror reflects the image into each eye2 in the latter the views are pasted on a card1 side by side1 and looked at through prismatic lenses4 ,the principles of ,binocular ,vision have been applied to the ,microscope4 ,in foregoing chapters we have given many examples with diagrams of the temporary impressions made upon the retina of the eye4 ,it is a fact that a wheel revolving at a great rate will appear to be standing still when suddenly illuminated by a flash of lightning1 because the eye has not time to take in the motion in the instant of time1 for the spokes of the wheel are not moving fast enough to convey the impression of motion in that half second to the eye2 yet the perfect outline of the wheel is distinctly visible4 ,indeed1 distinct vision can be exercised in a very small fraction of a second4 ,it was calculated by ,professor ,rood1 and proved by experiment1 that forty billionths of a second is sufficient time for the eye to distinguish letters on a printed page4 ,it this instance the illuminating power was an electric spark from a ,leyden ,jar4 ,we have remarked upon the distinctness with which we can see an object when we direct our gaze upon it1 and this appears a self-evident proposition2 but have any of our readers remarked the curious fact that when they want to see a faint and particular star in the sky it will at once disappear when they gaze at it8 ,the best way to see such very faint orbs as this is to look away from them1--a little to one side or the other1--and then the tiny point will become visible again to the eye4 ,there is also a degree of phosphorescence in the eye1 which any one who receives a blow upon that organ will readily admit4 ,even a simple pressure on the closed lid will show us a circle of light and 8colours like a peacock's tail10 as the great ,newton expressed it4 ,there are many occasions in which light is perceived in the eye--generally the result of muscular action2 and the ,irish term to 8knock fire out of my eye0 is founded upon philosophical facts4 ,we are many of us aware of 8spots0 on our eyes when our digestion is out of order1 and the inability of the eye to see figures distinctly in a faint light--within a proper seeing distance1 too--has often given rise to the 8ghost40 ,these shadowy forms are nothing more than affections of the eye1 and1 as well remarked in ,brewster's ,letters on ,natural ,magic1 8are always white because no other colour can be seen40 ,the light is not sufficiently strong to enable the person to see distinctly2 and as the eye passes from side to side1 and strives to take in the figure1 it naturally seems shadowy and indistinct1 and appears to move as our eyes move4 8,when the eye dimly descries an inanimate object whose different parts reflect different degrees of light1 its brighter parts may enable the spectator to keep up a continued view of it2 but the disappearance and reappearance of its fainter parts1 and the change of shape which ensues1 will necessarily give it the semblance of a living form2 and if it occupies a position which is unapproachable1 and where animate objects cannot find their way1 the mind will soon transfer to it a supernatural existence4 ,in like manner a human figure shadowed forth in a feeble twilight may undergo similar changes1 and after being distinctly seen while it is in a situation favourable for receiving and reflecting light1 it may suddenly disappear in a position before and within the reach of the observer's eye2 and if this evanescence takes place in a path or roadway where there is no sideway by which the figure could escape1 it is not easy for an ordinary mind to efface the impression which it cannot fail to receive40 ,this will account for many so-called 8ghosts40 ,accidental colours1 or ocular spectra1 are1 so to speak1 illusions1 and differently-coloured objects will1 when our gaze is turned from them1 give us different 8spectra0 or images4 ,for instance1 a violet object will1 when we turn to a sheet of white paper1 give us a yellow 8spectrum02 orange will be blue2 black and white will change respectively2 red will become a blue-green4 ,from a very strong white light the accidental colours will vary4 ,illustration3 ,fig4 #adi4--,the ,solar ,spectrum4 ,the ,solar ,spectrum is the name given to the coloured band formed by the decomposition of a beam of light into its elementary colours1 of which there are seven4 ,this is an easy experiment4 ,a ray of light can be admitted into a darkened room through a hole in the shutter1 and thus admitted will produce a white spot on the screen opposite1 as at g in the diagram 7fig4 #adi74 ,if we interpose a prism--a triangular piece of glass--the 8drop0 of a chandelier will do--we cause it to diverge from its direct line1 and it will produce a longer streak of light lower down4 ,this streak will exhibit the prismatic colours1 or the 8colours of the rainbow02 viz41 red 7at the top71 orange1 yellow1 green1 blue1 indigo 7blue71 and violet last4 ,these are the colours of the ,solar ,spectrum4 ,the white light is thus decomposed1 and it is called mixed light1 because of the seven rays of which it is composed4 ,these rays can be again collected and returned to the white light by means of a convex lens4 8,white light10 said ,sir ,isaac ,newton1 8is composed of rays differently refrangible10 and as we can obtain the colours of the rainbow from white light1 we can1 by painting them on a circular plate and turning it rapidly round1 make the plate appear white4 ,thus we can prove that the seven colours make 8white0 when intermingled4 ,but ,newton 7#afge7 did not arrive at the great importance of his experiment4 ,he made a round hole in the shutter1 and found that the various colours overlapped each other4 ,but1 in #ahjb1 ,dr4 ,wollaston improved on this experiment1 and by admitting the light through a tiny slit in the wood1 procured an almost perfect spectrum of 8simple0 colours1 each one perfectly distinct and divided by black lines4 ,but twelve years later1 ,professor ,fraunhofer made a chart of these lines1 which are still known by his name4 ,only1 instead of the #egf he discovered1 there are now thousands known to us6 ,to ,fraunhofer's telescope ,mr4 ,simms added a collimating lens1 and so the ,spectroscope was begun2 and now we use a number of prisms and almost perfect instruments1 dispersing the light through each4 ,we have here an illustration of a simple ,spectroscope1 which is much used for chemical analysis 7fig4 #aej74 ,in the spectrum we have long and short waves of light1 as we have long and short 7high and low7 waves in music1 called notes4 ,the long or low notes are as the red rays1 the high notes as the blue waves of light4 7,here we have another instance of the similarity between light and sound47 ,but suppose we shut out the daylight and substitute an artificial light4 ,if we use a lamp burning alcohol with salt 7chloride of sodium71 the spectrum will only consist of two yellow bands1 all the other colours being absent4 ,with lithium we obtain only two1 one orange and one red4 ,from this we deduce the fact that different substances when burning produce different spectra2 and although a solid may 7and platinum will7 give all seven colours in its spectrum1 others1 as we have seen1 will only give us a few1 the portion of the spectrum between the colours being black4 ,others are continuous1 and transversed by 8lines0 or narrow spaces devoid of light2 such is the spectrum of the sun1 and by careful and attentive calculation and observation we can get an approximate idea of the matter surrounding the heavenly bodies4 ,illustration3 ,fig4 #aej4--,the ,spectroscope4 ,we have said there are lines crossing the spectrum transversely2 these are called ,fraunhofer's lines1 after the philosopher who studied them2 they were1 however1 discovered by ,wollaston4 ,these lines are caused by light from the lower portion of the sun passing through the metallic vapours surrounding the orb in a state of incandescence1 such as sodium1 iron1 etc4 ,one of ,fraunhofer's lines1 a black double line known as ,d in the yellow portion of the spectrum1 was known to occupy the same place as a certain luminous line produced by sodium compounds in the flame of a spirit lamp4 ,this gave rise to much consideration1 and at length ,kirchkoff proved that the sodium vapour which gives out yellow light can also absorb that light2 and this fact1 viz41 that every substance1 which at a certain temperature emits light of a certain refrangibility1 possesses at that temperature the power to absorb that same light4 ,so the black lines are now considered the reversal of luminous lines due to the incandescent vapours by which the sun is surrounded4 ,thus the presence of an element can be found from black or luminous lines1 so the existence of terrestrial elements in celestial bodies has been discovered by means of preparing charts of the lines of the terrestrial elements1 and comparing them with the lines of stella spectra4 ,we have supposed the beam of light to enter through a slit in the shutter1 and fall upon a screen or sheet4 ,the solar spectrum shown by the passage of the beam through a prism is roughly as below-- ,illustration3 ,fig4 #aea4--;,example of the ,spectrum4 ,fraunhofer substituted a telescope for the lens and the screen1 and called his instrument a ,,spectroscope4 ,he then observed the lines1 which are always in the same position in the solar spectrum4 ,the principal of them he designated as ,a1 ,b1 ,c1 ,d1 ,e1 ,f1 ,g1 ,h4 ,the first three are in the red part of the spectrum2 one in the yellow1 then one in the green2 ,f comes between green and blue1 ,g in the indigo-blue1 and ,h in the violet4 ,but these by no means exhaust the lines now visible4 ,year by year the study of ,spectrum ,analysis has been perfected more and more1 and now we are aware of more than three thousand 8lines0 existing in the solar spectrum4 ,the spectra of the moon and planets contain similar dark lines as are seen in the solar spectrum1 but the fixed stars show different lines4 ,by spectrum analysis we know the various constituents of the sun's atmosphere1 and we can fix the result of our observations made by means of the ,spectroscope in the photographic camera4 ,by the more recent discoveries great studies have been made in 8solar chemistry40 ,what can we do with the ,spectroscope1 or rather1 ,what can we not do8 ,by ,spectroscopy we can find out1 and have already far advanced upon our path of discovery1 8the measure of the sun's rotation1 the speed and direction of the fierce tornados which sweep over its surface1 and give rise to the #8maelstroms' we term #8sunspots1' and the mighty alps of glowing gas that shoot far beyond the visible orb1 ever changing their form and size2 even the temperature and pressure of the several layers and their fluctuations are in process of being defined and determined40 ,this is what science is doing for us1 and when we have actually succeeded in ascertaining the weather at various depths in the atmosphere of the sun1 we shall be able to predict our own1 which depends so much upon the sun4 ,last year 7#ahhj7 ,professor ,adams1 in his address to the ,british ,association1 showed that magnetic disturbances1 identical in kind1 took place at places widely apart simultaneously4 ,he argues that the cause of these identical disturbances must be far removed from the earth4 8,if10 he says1 8we imagine the masses of iron1 nickel1 and magnesium in the sun to retain even in a slight degree their magnetic power in a gaseous state1 we have a sufficient cause for all our magnetic changes4 ,we know that masses of metal are ever boiling up from the lower and hotter levels of the sun's atmosphere to the cooler upper regions1 where they must again form clouds to throw out their light and heat1 and to absorb the light and heat coming from the hotter lower regions2 then they become condensed1 and are drawn back again towards the body of the sun1 so forming those remarkable dark spaces or sunspots by their down rush to their former levels4 ,in these vast changes we have abundant cause for those magnetic changes which we observe at the same instant at distant points on the surface of the earth40 ,so we are indebted to the ,spectroscope for many wonderful results--the constitution of the stars1 whether they are solid or gaseous1 and many other wonders4 ,the manner in which we have arrived at these startling conclusions is not difficult to be understood1 but some little explanation will be necessary4 ,the existence of dark lines in the solar spectrum proves that certain rays of solar light are absent1 or that there is less light4 ,when we look through the prism we perceive the spaces or lines1 and we can produce these ourselves by interposing some substance between the slit in the shutter before mentioned and the prism4 ,the vapour of sodium will answer our purpose1 and we shall find a dark line in the spectrum1 the bright lines being absorbed by the vapour4 ,we can subject a substance to any temperature we please1 and into any condition--solid1 liquid1 or gaseous2 we can also send the light the substance may give out through certain media1 and we can photograph the spectrum given out under all conditions4 ,the distance of the source of the light makes no difference4 ,so whether it be the sun1 or a far-distant star1 we can tell by the light sent to us what the physical condition of the star may be4 ,it was discovered in #ahfd that the same metallic body may give different spectra2 for instance1 the spectrum might be a band of light1--like the rainbow1--or a few isolated colours2 or again1 certain detached lines in groups4 ,the brightness of the spectrum lines will change with the depth of the light-giving source1 or matter which produces it4 ,we have become aware by means of the ,spectroscope that numerous metals known to us on earth are in combustion in the sun1 and new ones have thus been discovered4 ,in the immense ocean of gas surrounding the sun there are twenty-two elements as given by ,mr4 ,lockyer1 including iron1 sodium1 nickel1 barium1 zinc1 lead1 calcium1 cobalt1 hydrogen1 potassium1 cadmium1 uranium1 strontium1 etc4 ,not only is the visible spectrum capable of minute examination1 but1 as in the case of the heat spectrum already mentioned when speaking of ,calorescence1 the light spectrum has been traced and photographed far beyond the dark space after the blue and violet rays1 seven times longer than the visible solar spectrum--a spectrum of light invisible to our finite vision4 ,although a telescope has been invented for the examination of these 8ultra violet0 rays1 no human eye can see them4 ,but--and here science comes in--when a photographic plate is put in place of the eye1 the tiniest star can be seen and defined4 ,even the ,spectroscope at length fails1 because light at such limits has been held to be 8too coarse-grained for our purposes06 8,light10 says a writer on this subject 8we can then no longer regard as made of smooth rays2 we have to take into account--and to our annoyance--the fact that its #8long levelled rules' are rippled1 and its texture1 as it were1 loose woven06 ,twenty years ago ,professors ,kirchkoff and ,bunsen applied ,fraunhofer's method to the examination of coloured flames of various substances1 and since then we have been continually investigating the subject2 yet much remains to be learnt of ,spectrum ,analysis1 and ,spectroscopy has still much to reveal4 ,from ,newton's time to the present our scientists have been slowly but surely examining with the ,spectroscope the composition of spectra1 and the ,spectroscope is now the greatest assistant we possess4 8,spectrum ,analysis1 then1 teaches us the great fact that solids and liquids give out continuous spectra1 and vapours and gases give out discontinuous spectra instead of an unbroken light0 7,lockyer74 ,we have found out that the sunlight and moonlight are identical1 that the moon gives us spectrum like a reflection of the former1 but has no atmosphere1 and that comets are but gases or vapours4 ,the most minute particles of a grain of any substance can be detected to the millionth fraction4 ,the #a_/ajjj of a grain of blood can be very readily distinguished in a stain after years have passed4 ,the very year of a certain vintage of wine has been told by means of 8absorption10 or the action of different bodies on light in the spectrum4 ,it is now easy1 8by means of the absorption of different vapours and different substances held in solution1 to determine not only what the absorbers really are1 but also to detect a minute quantity40 ,the application of this theory is due to ,dr4 ,gladstone1 who used hollow prisms filled with certain substances1 and so thickened the 8absorption lines40 ,by these lines1 or bands1 with the aid of the ,spectrum ,microscope1 most wonderful discoveries have been made1 and will continue to be made4 ,we will close this portion of the subject with a brief description of the ,spectroscope in principle4 ,the instrument consists of two telescopes arranged with two object-glasses on a stand 7fig4 #aej74 ,a narrow slit is put in place of the eye-piece of one1 the arrangement admitting of the slit being made smaller or larger by means of screws4 ,the glass to which the slit is attached is called the collimating lens4 ,the light1 at the end of the slit seen from the other telescope1 being separated by the prisms between the two telescopes1 will produce the spectrum4 ,the ,spectroscope is enclosed1 so that no exterior light shall interfere with the spectra the student wishes to observe4 ,this merely indicates the principle1 not the details1 of the ,spectroscope1 which vary in different instruments4 ,we may now pass from the ,spectroscope to the ,telescope and the ,microscope1 instruments to which we are most largely indebted for our knowledge of our surroundings in earth1 air1 and water4 ,the word ,telescope is derived from the ,greek tele1 far1 and skopein1 to see2 and the instrument is based upon the property possessed by a convex lens or concave mirror1 of converging to a focus the rays of light falling on it from any object1 and at that point or focus forming an image of the object4 ,the following diagram will illustrate this4 ,let ,,vw be a lens1 and ,,ab an object between the glass1 and ,f the focus4 ,the ray1 ,ac1 is so refracted as to appear to come from a4 ,the ray from b likewise appears in a similar way1 and a magnified image1 ab1 is the result 7fig4 #aeb74 ,the ordinary ,telescope consists of an object-glass and an eye-lens1 with two intermediates to bring the object into an erect position4 ,a lens brings it near to us1 and a magnifier enlarges it for inspection4 ,we will now give a short history of the ,telescope and its improved construction4 ,roger ,bacon was supposed to have had some knowledge of the ,telescope1 for in #aeea it was written3 8,great talke there is of a glass he made at ,oxford1 in which men see things that were don40 ,but a little later1 ,baptista ,porta found out the power of the convex lens to bring objects 8nearer40 ,it was1 however1 according to the old tale1 quite by an accident that the ,telescope was discovered about the year #afjh4 ,illustration3 ,fig4 #aeb4--;,converging rays to a focus4 ,in ,middleburg1 in ,holland1 lived a spectacle-maker named ,zachary ,jansen1 and his sons1 when playing with the lenses in the shop1 happened to fix two of them at the proper distance1 and then to look through both4 ,to the astonishment of the boys1 they perceived an inverted image of the church weathercock much nearer and much larger than usual4 ,they at once told their father what they had seen4 ,he fixed the glasses in a tube1 and having satisfied himself that his sons were correct1 thought little more about the matter4 ,this is the story as told1 but there is little doubt that for the first ,telescope the world was indebted either to ,hans ,lippersheim or ,joseph ,adriansz1 the former a spectacle-maker of ,middleburg2 and in ,october #afjh1 ,lippersheim presented to the ,government three instruments1 with which he 8could see things at a distance40 ,jansen came after this4 ,the report of the invention soon spread1 and ,galileo1 who was then in ,venice1 eagerly seized upon the idea1 and returning to ,padua with some lenses1 he managed to construct a telescope1 and began to study the heavens4 ,this was in #afji4 ,galileo's ,tube became celebrated1 and all the first telescopes were made with the concave eye-lens4 ,rheita1 a monk1 made a binocular telescope1 as now used in our opera- and field-glasses approximately4 ,but the prismatic colours which showed themselves in the early telescopes were not got rid of1 nor was it till #agbi that ,hall1 by studying the mechanism of the eye1 managed a combination of lenses free from colour4 ,ten years before 7in #agah7 ,hadley had established the ,reflector ,telescope2 ,herschel made his celebrated forty-foot 8reflector0 in #aghi4 ,illustration3 ,fig4 #aec4--,the ,microscope4 ,however1 to resume4 ,in #agdg1 ,euler declared that it was quite possible to construct an arrangement of lenses so as to obtain a colourless image1 but he was at first challenged by ,john ,dollond4 ,the latter1 however1 was afterwards induced to make experiments with prisms of crown and flint glass4 ,he then tried lenses1 and with a concave lens of flint1 and a convex lens of crown1 he corrected the colours4 ,the question of proper curvature was finally settled1 and the 8,achromatic0 ,telescope became an accomplished fact4 ,there are two classes of ,telescopes--the reflecting and refracting4 ,lord ,rosse's is an instance of the former4 ,mr4 ,grubb's immense instrument in ,dublin is a refractor4 ,the ,microscope has been also attributed to ,zacharias ,jansen1 and ,drebbel1 in #afai1 possessed the instrument in ,london1 but it was of little or no use4 ,the lens invented by ,hall1 as already mentioned1 gave an impetus to the ,microscope4 ,in the simple ,microscope the objects are seen directly through the lens or lenses acting as one4 ,the compound instrument is composed of two lenses 7or a number formed to do duty as two71 an eye-lens1 and an object-lens4 ,between these is a 8stop0 to restrain all light1 except what is necessary to view the object distinctly4 ,the large glass near the object bends the rays on to the eyeglass1 and a perfect magnified image is perceived4 ,we annex diagrams1 from which the construction will be readily understood4 ,illustration3 ,fig4 #aed4--;,image on the ,retina4 ,we have in the previous chapter mentioned the effect of light upon the eye and its direction1 and when an object is placed very near the eye we know it cannot be distinctly seen2 a magnified image is thrown upon the retina1 and the divergency of the rays prevents a clear image being perceived4 ,but if a small lens of a short 8focal length0 be placed in front of the eye1 having ,,pq for its focus1 the rays of light will be parallel1 or very nearly so1 and will as such produce 8distinct vision10 and the image will be magnified at pq4 ,in the ,compound ,refracting ,microscope1 ,,bab is the convex lens1 near which an object1 ,,pq1 is placed a little beyond its focal length4 ,an inverted image1 pq1 will then be formed4 ,this image is produced in the convex lens1 bab1 and when the rays are reflected out they are parallel1 and are distinctly seen4 ,so the eye of the observer at the point ,e will see a magnified image of the object at ,,pq brought up to pq 7fig4 #aee74 ,illustration3 ,fig4 #aee4--,the ,microscope lenses4 ,sir ,isaac ,newton suggested the ,reflecting ,microscope1 and ,dr4 ,wollaston and ,sir ,david ,brewster improved the instrument called the 8,periscopic ,microscope10 in which two hemispherical lenses were cemented together by the plane surfaces1 and having a 8stop0 between them to limit the aperture4 ,then the 8,achromatic0 instrument came into use1 and since then the ,microscope has gradually attained perfection4 ,illustration3 ,fig4 #aef4--;,concave lens4 ,we have so frequently mentioned lenses that it may be as well to say something about them4 ,lenses may be spherical1 double-convex1 plane-convex1 plane-concave1 double-concave1 and concave-convex4 ,convex lenses bring the parallel lines which strike them to a focus1 as we see in the 8burning-glass40 ,the concave or hollow lens appears as in fig4 #aef4 ,the rays that follow it parallel to its axis are refracted1 and as if they came from a point ,f in the diagram4 ,but converging rays falling on it emerge in a parallel direction as above1 or diverge as in fig4 #aeh4 ,illustration3 ,fig4 #aeg4 #a4 ,focus of parallel rays4 #b4 ,focus of divergent rays4 #c4 ,focus of divergent rays brought forward by more convex lens4 ,the use of spectacles to long or short-sighted people is a necessity1 and the lenses used vary4 ,the eye has usually the capacity of suiting itself to viewing objects--its accommodation1 as it is termed--near or far4 ,but when the forepart of the eye is curved1 and cannot adapt itself to distant objects1 the person is said to be short-sighted4 ,in long sight the axis of the eyeball is too short1 and the focus falls beyond the retina2 in short sight it is too long4 ,in the diagrams herewith fig4 #aei shows by the dotted lines the position of the retina in long sight1 and fig4 #afj in short sight1 the clear lines showing in each case the perfectly-formed eye4 ,for long sight and old sight the double-convex glass is used1 for short sight the double-concave 7fig4 #afb74 ,we know the burning-glass gives us a small image of the sun as it converges the rays to its focus4 ,but lenses will do more than this1 and in the ,,photographic ,,camera we find great interest and amusement4 ,illustration3 ,fig4 #aeh4--;,diverging rays4 ,photography 7or writing by light7 depends upon the property which certain preparations possess of being blackened by exposure to light while in contact with matter4 ,by an achromatic arrangement of lenses the camera gives us a representation of the desired object ,fig4 #afc shows the image on the plate1 and figs4 #afd and #afe the arrangement of lenses4 ,illustration3 ,fig4 #aei4--;,hypermetropia 7long sight744 ,illustration3 ,fig4 #afj4--,myopia 7short sight74 ,illustration3 ,fig4 #afa4--;,concave and convex lenses4 ,illustration3 ,fig4 #afb4--,lenses for long and short sight4 ,to ,porta1 the ,neapolitan physician1 whose name we have already mentioned more than once1 is due the first idea of the ,photographic ,camera4 ,he found that if light was admitted through a small aperture1 objects from which rays reached the hole would be reflected on the wall like a picture4 ,to this fact we are indebted for the ,,camera ,,obscura1 which receives the picture upon a plane surface by an arrangement of lenses4 ,in fact1 ,porta nearly arrived at the ,daguerreotype process4 ,he thought he could teach people to draw by following the focussed picture with a crayon1 but he could not conquer the arial perspective4 ,so the camera languished till #ahbj1 when ,wedgwood and ,sir ,humphrey ,davy attempted to obtain some views with nitrate of silver1 but they became obliterated when exposed to the daylight4 ,illustration3 ,fig4 #afc4--,the ,camera4 ,as early as #ahad1 however1 ,m4 ,niepce had made a series of experiments in photography1 and subsequently having heard that ,m4 ,daguerre was turning his attention to the same subject1 he communicated with him4 ,in #ahbg a paper was read before the ,royal ,society1 and in #ahbi a partnership deed was drawn up between ,daguerre and ,niepce for 8copying engravings by photography40 ,daguerre worked hard1 and at length succeeded in obtaining a picture by a long process1 to which1 perhaps1 some of our readers are indebted for their likenesses forty years ago4 ,by means of iodine evaporated on a metal plate covered with 8gold-yellow10 and exposing the plate then in a second box to mercurial vapour1 he marked the image in the camera1 and then he immersed the plate in hyposulphate of soda1 and was able to expose the image obtained to daylight4 ,illustration3 ,fig4 #afd4 ,arrangement of lenses ,fig4 #afe4 ,but the mode now in use is the 8collodion0 process4 ,we have all seen the photographer pouring the iodized collodion on the plate1 and letting the superfluous liquid drain from a corner of the glass4 ,when it is dry the glass-plate is dipped into a solution of nitrate of silver1 and then in a few minutes the glass is ready4 ,the focus is then arranged1 and the prepared plate conveyed in a special slide--to keep it from the light--to the camera4 ,when the 8patient0 is ready1 the covering of the lens is removed1 and the light works the image into the sensitive plate4 ,the impression is then 8brought up10 and when developed is washed in water1 and after by a solution which dissolves all the silver from the parts not darkened by the light4 ,thus the negative is obtained and printed from in the usual manner4 ,instantaneous photography is now practised with great success4 ,an express train1 or the movements of a horse at full speed1 can thus be taken in a second or less4 ,these results are obtained by using prepared plates1 and the 8emulsion process10 as it is called1 succeeds admirably4 ,the mode of preparation is given in a late work upon the subject1 and the photographic plates may also be obtained ready for use4 ,gelatine and water1 mixed with bromide of ammonium1 nitrate of silver1 and carbonate of ammonium1 mixed with certain proportions of water1 form the 8emulsion40 ,we need not go into all the details here4 ,information can easily be obtained from published works1 and as the plates can be purchased by amateurs1 they will find that the best way4 ,aside from the art interest in the new plates is quite another1 that springs from the fact that it is now possible to take pictures of men1 animals1 and machinery in rapid motion1 thus enabling us to view them in a way that would be impossible with the unaided eye4 ,the first experiments in this direction were applied to the movements of a horse moving at full speed4 ,the pictures1 taken in series1 showed that he performed muscular actions that were not before comprehended or even imagined4 ,these pictures at the time attracted great attention1 and instantaneous pictures have been since taken of dancers in a ball-room1 of vessels and steam-boats in rapid movement1 of all kinds of animals in motion1 and of machinery in operation4 ,as the pictures represent the movements at one instant of time1 they give1 as it were1 a fixed view of a motion1 precisely as if it were suddenly arrested in full action4 ,in the case of animals1 the motions of the nostrils are represented in the most singular manner1 and the spokes of a steam-boat's paddle-wheel are shown apparently perfectly still while the spray and waves appear in active motion1 or1 rather1 as they would look if they could be instantly frozen4 ,it is clear the new process and pictures will open a wide and instructive field in art and in the study of mechanical action4 ,while on the subject of ,photography we may mention a very ingenious little apparatus called a ,,scenograph1 the invention of ,dr4 ,candize4 ,it is really a pocket-camera1 and is so easily manipulated that it will be found a most pleasant and useful holiday companion4 ,any one may obtain good results with it1 and friends of ours have had occasion to put it in practice during a series of excursions1 when it was found to answer in every instance4 ,the ,scenograph is something like a common ,stereoscope in outward appearance1 and would1 perhaps1 be at first regarded as a mere toy1 did not a more intimate acquaintance prove it a great acquisition1 particularly to explorers and tourists4 ,the tripod stand which supports the apparatus is1 when not in actual use in that capacity1 a very excellent walking-stick1 in which the two other 8legs0 are carried4 ,the instrument1 as will be perceived from the illustration 7fig4 #aff71 is very handy4 ,it produces pictures about the 8cabinet0 size1 and the whole is so arranged that it can be packed and carried in the pocket with ease4 ,illustration3 ,fig4 #aff4--,the ,scenograph4 ,photography1 as a rule1 necessitates a dark room or cabinet1 and many preparations as we all know--a 8messing0 about with chemicals and considerable practice before we can become proficient2 so it is not surprising that few amateurs take to it--they prefer to purchase the pictures4 ,but in the new apparatus of which we are speaking1 the glass plates are already prepared to receive the image4 ,it is not at all necessary for the operator to stain his fingers and knuckles and nails with nitrate of silver1 or any other 8chemicals0 whatever4 ,he just inserts the plate in the ,scenograph1 and then his apparatus being steadily set up1 he removes the covering from the lens4 ,to develop the image 7in the dusk of the evening or by candle-light7 it is necessary to put some drops of ammonia in a saucer1 breathe upon the plate so as to soften the collodion1 and hold it above the ammonia1 and then1 under the influence of the vapour1 the picture will appear4 ,after this simple operation the picture will be found fixed for a lengthened period--practically indefinitely4 ,thus on the return of the pedestrian he can reproduce1 at small expense1 a whole series of little pictures faithfully representing his holiday tour4 ,the illustration shows a small apparatus by which on thin plates small photographs can be taken and fixed till it is found desirable to enlarge them4 ,the ,photophone1 one of the most recent contributions to science1 is an instrument which1 in combination with the telephone principle1 makes it possible to convey sounds by means of a ray of light1 and by means of a quivering beam 8to produce articulate speech at a distance4 ,the success of the ,photophone depends upon a rare element1 selenium1 which has its 8electrical resistance0 affected by light4 ,professor ,adams demonstrated that the resistance of selenium was reduced just in proportion as the intensity of the light which was acting upon it4 ,here was the key to the ,photophone as thought out by ,professor ,bell4 ,he fancied that he might by means of his telephone produce sound if he could vary the intensity of the beam of light upon the selenium1 which he connected with his telephone and battery4 ,the ,photophone consists of a transmitter for receiving the voice and conveying it along the beam of light1 and a receiver for taking the light and converting it into sound--the receiver being the telephone4 ,there is a small mirror 7silvered mica has been used7 suspended freely for vibration4 ,a lens is used to transmit to this the beam of light1 and this beam is again reflected by another lens to the receiver1 which consists of a reflector which has a cell of selenium in its focus1 connected1 as already stated1 with the telephone and battery4 ,the speaker stands behind the mirror1 and the sound of his voice against the reverse side makes it vibrate in unison with the sounds uttered4 ,the movements cause a quivering in the reflected beam1 and this in its changing intensity acts on the selenium1 which changes its resistance accordingly1 and through the telephone gives forth a sound6 ,this is the apparently complicated but really simple1 and at the same time wonderful1 invention of ,professor ,bell4 ,by the ,photophone not only sounds but movements can be converted into sound2 even the burning of a candle can be heard6 ,the ,photophone is still capable of improvement1 and has not as yet arrived at its full development1 for it is stated it can be made quite independent of a battery or telephone4 ,there are many phenomena connected with the ,polarization of ,light4 ,this requires some notice at our hands4 ,we know that a ray of ordinary light is supposed to be caused by vibrations of the highly attenuated medium1 ther4 ,these vibrations occur across the direction of the ray2 but when they occur only in one plane the light is said to be 8polarized40 ,polarization means possessing poles 7like a magnet72 the polarized rays have 8sides10 as ,newton said1 or1 as explained by ,dr4 ,whewell1 8opposite properties in opposite directions1 so exactly equal as to be capable of accurately neutralizing each other40 ,there are some crystals which possess the property of 8double refraction10 and thus a ray of common light passing through such a crystal is divided into two polarized rays1 taking different directions4 ,one is refracted according to the usual laws of refraction2 the other is not1 and the planes of polarization are at right angles4 ,it is difficult within the limits of this chapter to explain the whole theory of ,polarization4 ,in order to account for certain phenomena in optics1 philosophers have assumed that rays possess polarity2 and polarized light is light which has had the property of ,polarization conferred upon it by reflection1 refraction1 or absorption4 ,common light has been compared to a round ruler1 and polarized light to a flat ribbon4 ,huygens found out1 when engaged upon the investigation of double refraction1 that the rays of light1 divided by passing through a crystal 7a rhomb7 of ,iceland spar1 possessed certain qualities4 ,when he passed them through a second rhomb1 he found that the brightness1 relatively1 of the rays depended upon the position of the second prism1 and in some positions one ray disappeared entirely4 ,the light had been reduced to vibrations in one plane4 ,in #ahjh1 ,malus1 happening to direct a double refracting prism to the windows then reflecting the sunset1 found that as he turned the prism round1 the ordinary image of the window nearly disappeared in two opposite positions2 and in two other positions1 at right angles1 the 8extraordinary0 image nearly vanished4 ,so he found that polarization was produced by reflection as well as by transmission4 ,the differences between common and polarized light have been summed up by ,mr4 ,goddard as follows3-- ,,common ,,light ,,polarized ,,light 8,is capable of reflection at 8,is capable of reflection at oblique angles of incidence in oblique angles only in every position of the reflector4 certain positions of the reflector4 8,will pass through a bundle of 8,will only pass through such plates of glass in any position glasses when they are in in which they may be placed4 certain positions4 8,will pass through a plate of 8,will only pass in certain tourmaline1 cut parallel to the positions1 and in others axis of the crystal1 in every will not pass at all40 position of the plate40 ,the bundle of glass plates or the tourmaline plate is thus the test for polarized light1 and is termed an analyzer4 ,the arrangement called a 8,nichol's prism10 made by cutting a prism of ,iceland spar and uniting the halves with a cement1 so that only one polarized ray can pass through it1 is termed a ,polarizer4 ,it only permits one of the two rays produced by 8double refraction0 to pass1 and the ray 7as said above7 will contain none but transverse vibrations4 ,polarized light will produce beautiful colours4 ,the whole subject is very interesting to the scientist1 but rather a difficult one for the general reader to understand4 ,amongst the uses to which light has been put is that of a milk-tester4 ,the ,,lactoscope will show the quantity of butter contained in a certain quantity of milk1 by diluting it till it displays a certain degree of transparency4 ,there is another method1 by the transmission of light4 ,the first test is obtained by means of a glass tube about nine inches long1 closed at one end1 and containing a small porcelain rod marked with black lines4 ,a small quantity of milk is measured and placed in the tube4 ,the black lines cannot at first be seen through the tube1 but by adding water the milk is rendered transparent1 and the black lines become visible4 ,the surface of milk in the tube1 by a graduated scale upon it1 shows the percentage of butter4 ,illustration3 ,fig4 #afg4--;,cut card figures4 ,the second method is not so simple4 ,a short tube of tin1 blackened on the inside1 and supported upright1 has an opening on one side1 and opposite this1 inside the tube1 is a mirror placed at an angle of #de4 8,by placing a lighted candle at a known distance opposite the opening1 its light is reflected in the mirror and thrown upward through the tube4 ,on top of the tube is placed a round vessel of glass or metal1 closed at the bottom by a sheet of clear glass4 ,the vessel is closed at the top by a cover having an opening in the centre1 in which slides up and down a small tube closed at the bottom with glass1 and having an eye-piece at the top4 ,the milk to be tested is placed in this vessel on the top of the tin tube1 so that the light of the candle reflected from the mirror passes upward through the milk4 ,then1 by looking through the sliding tube and moving it up and down1 a point may be found where the image of the candle in the mirror can be seen through the milk4 ,this device depends1 as will be seen1 on observing the light transmitted through a film of milk1 and the thickness of the film is the measure of the value of the milk4 ,the movable tube contains a graduated scale1 and by comparison of this with a printed table1 the percentage of butter in the milk may be ascertained40 ,in concluding this chapter we give a few hints for some pleasant relaxation for young people1 which has many a time created amusement4 ,the experiment consists in cutting out in paper or cardboard certain portions of a face or figure1 as per the illustration herewith4 ,fig4 #afg gives the card as cut with the scissors1 and the two subsequent faces are the result of the same held at a less or greater distance from a screen4 ,the illustrations 7fig4 #afh7 will assist those who wish to amuse children by making rabbits1 etc41 on the wall4 ,the shadows will be seen perfectly thrown if the hands be carefully fixed near a good light4 ,illustration3 ,fig4 #afh4--;,hand-shadows on the wall4 ,we are all so familiar with the 8,magic ,lantern10 and the apparatus for dissolving views by an arrangement of lenses and manipulation of slides1 that we need do no more than refer to them4 ,illustration3 ,fig4 #afi4--;,dissolving views apparatus4 ,the various ghost illusions1 etc41 produced by indirect mirrors1 have already been referred to1 the ghost being merely the reflection of an individual seen through a sheet of glass between the spectators and the stage4 ,the strong light throws a reflection from a parallel mirror lower down1 and this reflected image can be made to appear amongst the real actors who are behind the plate-glass in full view of the audience1 who are1 however1 ignorant of the existence of the glass screen4 ,for the winter evenings one may easily procure an apparatus for dissolving views by the oxy-hydrogen light4 ,one1 as shown in the illustration herewith 7fig4 #afi71 will answer every purpose1 and by this double arrangement phantasmagoria may be produced1 or a fairy tale may be illustrated4 ,the effect of gradually-approaching night may be given to the picture by means of a special glass in the lower lanthorn4 ,the apparatus is exhibited by means of a ,drummond light1 and is very simple1 although a certain supply of gas is necessary for the performance4 ,but this can be easily procured by an indiarubber tube1 or in a bag supplied for the purpose4 ,almost any objects can be used1 photographs1 etc41 etc41 and many very comical arrangements can be made4 ,we have lately been reading a curious method of obtaining light from oyster-shells in a ,trans-,atlantic magazine4 ,we give an extract wherewith to close this chapter4 ,the compound is 8luminous paint40 8,it has been known that certain compounds of lime and sulphur had the property of absorbing light1 and giving it out again when placed in the dark4 ,a simple way to do this is to expose clean oyster-shells to a red heat for half an hour4 ,when cold1 the best pieces are picked out and packed with alternate layers of sulphur in a crucible1 and exposed to a red heat for an hour4 ,when cold1 the mass is broken up1 and the whitest pieces are placed in a clean glass bottle4 ,on exposing the bottle to bright sunshine during the day1 it is found that at night its contents will give out a pale light in the dark4 ,such a bottle filled more than a hundred years ago still gives out light when exposed to the sun1 proving the persistency of the property of reproducing light4 ,very many experiments have been more recently made in this direction1 and the light-giving property greatly enhanced4 ,the chemicals1 ground to a flour1 may now be mixed with oils or water for paints1 may be powdered on hot glass1 and glass covered with a film of clear glass1 or mixed with celluloid1 papier-mach1 or other plastic materials4 ,as a paint1 it may be applied to a diver's dress1 to cards1 clock dials1 sign-boards1 and other surfaces exposed to sunlight during the day2 the paint gives out a pale violet light at night sufficient to enable the objects to be readily seen in the dark4 ,if the object covered with the prepared paint is not exposed to the sun1 or if the light fades in the dark1 a short piece of magnesium wire burned before it serves to restore the light-giving property40 ,,chapter ,,xiv4 ,,spectral ,,illusions4 ,a ,,spectre ,,visible--,,curious ,,illusions--,,ghosts4 ,we have already given numerous examples of the effects produced by impressions on the retina by mechanical appliances4 ,we can now in a short chapter speak of the cause of many spectral illusions1 commonly supposed to be 8ghosts0 or 8spirits40 ,that there are many 8well-authenticated #8ghost stories'0 no one can doubt who has read the literature of the day2 and we ourselves do not in any way desire to throw any doubt upon the existence of certain so-called 8ghosts40 ,that appearances of some kind or another are seen by people we know4 ,we ourselves have seen such1 but we cannot say we believe in the popular ghost4 ,in ancient times mirrors were much employed by the so-called magicians1 and in our day many wonderful ghost effects have been shown at the 7late7 ,polytechnic ,institution4 ,some people are believers in table-turning and spiritualism1 and mesmerists still attract large audiences1 and appear to possess extraordinary power over some individuals4 ,but apparitions have been seen by people eminently worthy of credit4 ,the experience of the learned ,doctor1 which appeared some months ago in the ,athenum1 is a case in point4 ,this narrative is concise and clear4 ,the spectre was there4 ,how did it get there8 ,was the 8appearance0 objective or subjective8 ,let us give an extract from the ,reverend ,doctor's narrative1 and comment upon it afterwards4 ,we may premise that ,dr4 ,jessopp had gone over to ,lord ,orford's 7,mannington ,hall71 and at eleven o'clock was busy writing in the library1 and was 8the only person downstairs40 ,we will give this ghost story in the ,doctor's own words4 ,after taking up a certain volume--time about #a a4m43-- 8,i had been engaged on it about half an hour1 and was beginning to think my work was drawing to a close1 when1 as ,i was actually writing1 ,i saw a large white hand within a foot of my elbow4 ,turning my head1 there sat a figure of a somewhat large man with his back to the fire1 bending slightly over the table1 and apparently examining the pile of books that ,i had been at work upon40444 ,after describing the appearance of the nocturnal visitor1 ,dr4 ,jessopp proceeds3-- 8,there he sat1 and ,i was fascinated2 afraid not of his staying1 but lest he should go4 ,stopping in my writing ,i lifted my left hand from the paper1 stretched it out to the pile of books1 and moved the top one--my arm passed in front of the figure1 and it vanished40444 ,shortly after the figure appeared again1 and 8,i was penning a sentence to address to him1 when ,i discovered ,i did not dare to speak4 ,i was afraid of the sound of my own voice6 ,there he sat1 and there sat ,i4 ,i turned my head and finished writing4 ,having finished my task1 ,i shut the book1 and threw it on the table2 it made a slight noise as it fell2--the figure vanished40 ,now here we have a perfectly plain narrative1 clear and full4 ,a ghost appeared2 he is described distinctly4 ,how can we account for the apparition8 ,in the first place1 someone might have played a trick1 but that idea was put aside by ,dr4 ,wilks1 who attempted to explain the appearances4 ,he went fully into the question1 and as it bears upon our explanation of the reality of ,spectral ,illusions1 we may condense his evidence4 ,it will of course be conceded that all the usual objects seen by people are material1 and the image of what we look at is formed upon the retina in the manner already explained4 ,but all images upon the retina are not immediately observed2 the impression may1 to a certain extent1 remain4 ,words are often impressed upon the brain1--words which we in our sober senses would never think of repeating1--and yet when we are delirious we give vent to these expressions1 of whose very nature and meaning we are perfectly unconscious4 ,it is1 according to our reference 7,dr4 ,wilks71 8quite possible for the perceptive part of the brain to be thrown into an active condition quite independent of the normal stimulus conducted to it from the retina40 ,if1 under these circumstances1 an object be viewed independently1 and1 as it were1 unconsciously1 it is merely1 we believe1 a parallel to the impression of words before noted4 ,sound and light are governed by the same laws4 ,in fevers we fancy we see all kinds of things which have no existence4 ,in dreams we hear noises2 and many a time people dreaming have been awakened by the report of a gun1 or the ringing of a bell which had no material origin1--the nerves were excited1 the 8perceptive centre0 of the brain was moved4 ,but if sight and hearing thus have their origin from the brain and not from without1 there must have been some predisposing cause1 some excitement to induce such a condition of things4 8,the impressions become abnormal and subjective1--the normal condition being objective1--the impression is received from without1 and impressed upon the eye4 ,now1 let us consider the 8ghost06 ,lately there have been many instances brought forward of 8spiritual0 appearances1 but we think nobody has ever seen a 8material0 ghost2 yet on the other hand none of us have any knowledge of anything in the likeness of a ghost1 or that has not a material basis which can bring forward an image on the retina6 ,therefore we are brought to the conclusion that apparitions are spectres emanating from within the brain1 not from any outward manifestation1 because it is within the experience of everybody that in bad health1 or disordered digestive functions1 images are produced in the brain and nerves of the eye4 ,these remarks have perhaps been made before in one form or other1 but as much popular interest is always awakened by the supernatural1 or what is supposed to be supernatural1 we may go a little farther1 and inquire how it was that the ghost seen by ,dr4 ,jessopp disappeared when he raised his arm4 ,would any ghost be afraid of the ,doctor extending his hand8 ,the fact no doubt occurred as related4 ,the explanation is that the narrator had been much impressed by a certain picture1 which a correspondent soon identified as a portrait of 8,parsons1 the ,jesuit ,father40 ,the description given is that of the priest who was described by the ,doctor in one of his books4 ,the association of ideas in the library of a ,norfolk house connected with the ,walpoles1 with whom ,parsons had been a leader1 gave rise1 during a period of 8forty winks0 at midnight1 to the spectre4 ,in the interesting letters written upon 8,natural ,magic0 by ,sir ,david ,brewster1 the subject of ,spectral ,illusions is treated at some length1 and with undoubted authority4 ,sir ,david thought the subject worth discussing with reference to the illusions or spectres mentioned by ,dr4 ,hibbert4 ,sir ,david ,brewster gives his own experiences which occurred while he was staying at the house of a lady in the country4 ,the illusions appear to have affected her ear as well as the eye4 ,we shall see in the next chapter how intimately sound and light are connected1 and how the eyes and ears are equally impressed1 though in a different way1 by the vibration of particles4 ,the lady referred to was about to go upstairs to dress for dinner one afternoon1 when she heard her husband's voice calling to her by name4 ,she opened the door1 and nobody was outside2 and when she returned for a moment to the fire she heard the voice again calling1 8,come to me2 come1 come away10 in a somewhat impatient tone4 ,she immediately went in search of her husband1 but he did not come in till half an hour afterwards1 and of course said he had not called1 and told her where he had been at the time--some distance away4 ,this happened on the #bfth ,december1 #ahcj1 but a more alarming occurrence took place four days after4 ,about the same time in the afternoon of the #cjth ,december1 the lady came into the drawing-room1 and to her great astonishment she perceived her husband standing with his back to the fireplace4 ,she had seen him go out walking a short time previously1 and was naturally surprised to find he had returned so soon4 ,he looked at her very thoughtfully1 and made no answer4 ,she sat down close beside him at the fire1 and as he still gazed upon her she said1 8,why don't you say something60 ,the figure immediately moved away towards the window at the farther end of the room1 still gazing at her1 8and it passed so close that she was struck by the circumstance of hearing no step nor sound1 nor feeling her dress brushed against1 nor even any agitation of the air40 ,although convinced this was not her husband1 the lady never fancied there was anything supernatural in the appearance of the figure4 ,subsequently she was convinced that it was a spectral illusion1 although she could not see through the figure which appeared as substantial as the reality4 ,were it advisable1 we could multiply instances4 ,in the ,edinburgh ,journal of ,science these1 and many more instances of spectral illusions were narrated by the husband of the lady4 ,she frequently beheld deceased relatives or absent friends1 and described their dress and general appearance very minutely4 ,on one occasion she perceived a coach full of skeletons drive up to the door1 and noticed spectral dogs and cats 7her own pets' likenesses7 in the room4 ,there can be no doubt upon these points2 the appearances were manifest and distinct4 ,they were seen in the presence of other people1 in solitude1 and in the society of her husband4 ,the lady was in delicate health1 and very sensitive4 ,the spectres appeared in daylight as well as in the dark1 or by candle-light4 ,let us now1 guided by what we have already written1 and by ,sir ,david ,brewster's experience1 endeavour to give a rational explanation of these illusions4 8,the mind's eye is really the body's eye1 and the retina is the common tablet upon which both classes of impressions are painted1 and by means of which they receive their visual existence according to the same optical laws40 8,in the healthy state of mind and body the relative intensity of the two classes of impressions on the retina are nicely adjusted--the bodily and mental are balanced4 ,the latter are feeble and transient1 and in ordinary temperaments are never capable of disturbing or effacing the direct images of visible objects4444 ,the mind cannot perform two different functions at the same instant1 and the direction of its attention to one of the two classes of impressions necessarily produces the extinction of the other2 but so rapid is the exercise of mental power1 that the alternate appearance and disappearance of the two contending impressions is no more recognized than the successive observations of external objects during the twinkling of the eyelids40 ,we have before illustrated1 by means of the pen and the ink-bottle1 how one object is lost sight of when the other is attentively regarded1 and a material picture or scene may be equally lost sight of1 and a mental picture take its place in the eye1 when we recall places or people we have seen or remembered4 ,we have all heard numerous anecdotes of what is termed 8absent-mindedness40 ,some people are quite absorbed in study1 and can see or hear no one in the room when deeply occupied4 ,we may be satisfied then that 8pictures of the mind and spectral illusions are equally impressions upon the retina1 and only differ in the degree of vividness with which they are seen40 ,if we press our eyes the phosphorescence becomes apparent1 and we can make a picture of the sun or a lamp visible for a long time to our closed eyes if we stare at either object for a few seconds1 and shut our lids4 ,so by increasing the sensibility of the retina we can obtain the image1 and alter its colour by pressure on the eye4 ,it is well known that poisons will affect sight1 and belladonna applied to the eyes will so affect them as to render the sight nil1 by enlargement of the 8pupil40 ,if one is out of health there is practically a poisoning of the system1 and when we have a 8bilious headache0 we see colours and stars because there is a pressure upon the blood-vessels of the eye4 ,the effects of a disordered stomach1 induced by drinking too much1 are well known2 objects are seen double1 and most ghosts may be traced to a disordered state of health of mind or body1 brought on by excitement or fatigue4 ,we could relate a series of ghost stories1--some in our own experience1 for we have seen a ghost equally with our neighbours1--but this is not the place for them4 ,although many apparently incontrovertible assertions are made1 and many spectres have been produced to adorn a tale1 we must put on record our own opinion1 that every one could be traced to mental impression or bodily affection had we only the key to the life and circumstances of the ghost-seer4 ,many celebrated conjurers will convince us almost against our reason that our pocket-handkerchief is in the orange just cut up4 ,they will bring live rabbits from our coat-pockets or vests1 and pigeons from our opera-hats4 ,these are equally illusions4 ,we know what can be done with mirrors4 ,we have seen ghosts at the ,polytechnic1 but we must put down all apparitions as the result of mental or bodily1 even unconscious impressions upon the retina of the eye4 ,there are numerous illusions1 such as the ,fata ,morgana1 the ,spectre of the ,brocken1 etc41 which are due to a peculiar state of the atmosphere1 and to the unequal reflection and refraction of light4 ,those1 and many other optical phenomena1 will1 with phenomena of heat and sound1 be treated under ,,meteorology1 when we will consider the rainbow and the aurora1 with many other atmospheric effects4 ,,chapter ,,xv ,,acoustics4 ,,the ,,ear1 ,,and ,,hearing--,,physiology ,,of ,,hearing ,,and ,,sound--,,sound ,,as ,,compared ,,with ,,light--,,what ,,is ,,sound8--,,velocity ,,of ,,sound--,,conductibility--,,the ,,harmonograph4 ,before entering upon the science of ,,acoustics1 a short description of the ear1 and the mode in which sound is conveyed to our brain1 will be no doubt acceptable to our readers4 ,the study of the organs of hearing is not an easy one2 although we can see the exterior portion1 the interior and delicate membranes are hidden from us in the very hardest bone of the body--the petrous bone1 the temporal and rock-like bone of the head4 ,illustration3 ,fig4 #agj4--a4 ,temple bone4 #b4 ,outer surface of temple4 #c4 ,upper wall of bony part of hearing canal4 #d4 ,ligature holding 8hammer0 bone to roof of drum cavity4 #e4 ,roof to drum cavity4 #f4 ,semicircular canals4 #g4 ,anvil bone4 #h4 ,hammer bone4 #i4 ,stirrup bone4 #aj4 ,cochlea4 #aa4 ,drum-head cut across4 #ab4 ,isthmus of ,eustachian tube4 #ac4 ,mouth of tube in the throat4 #ad4 ,auditory canal4 #ae4 ,lower wall of canal4 #af4 ,lower wall of cartilaginous part of canal4 #ag4 ,wax glands4 #ah4 ,lobule4 #ai4 ,upper wall of cartilaginous portion of canal4 #bj4 ,mouth of auditory canal4 #ba4 ,anti-tragus4 ,the ear 7external7 is composed of the auricle1 the visible ear1 the auditory canal1 and the drum-head1 or membra tympani4 ,the tympanum1 or 8drum10 is situated between the external and the internal portions of the ear4 ,this part is the 8middle ear10 and is an air cavity1 and through it pass two nerves1 one to the face1 and the other to the tongue4 ,the internal ear is called the 8labyrinth10 from its intricate structure4 ,we give an illustration of the auditory apparatus of man 7fig4 #agj74 ,the auricle1 or exterior ear1 is also represented1 but we need not go into any minute description of the parts4 ,we will just name them 7fig4 #aga74 ,sound is the motion imparted to the auditory nerve1 and we shall see in a moment how sound is produced4 ,the undulations enter the auditory canal1 having been taken up by the auricle2 the waves or vibrations move at the rate of #a1ajj feet a second1 and reach the drum-head1 which has motion imparted to it4 ,this motion or oscillation is imparted to other portions1 and through the liquid in the labyrinth4 ,the impressions of the sound wave are conveyed to the nerve1 and this perception of the movement in the water of the labyrinth by the nerve threads and the brain causes what we term 8hearing40 ,illustration3 ,fig4 #aga4--a4 ,pit of anti-helix4 #b1 #f1 #aj4 ,curved edge of the auricle4 #c4 ,mouth of auditory canal4 #d4 ,tragus4 #e4 ,lobe4 #g4 ,anti-helix4 #h4 ,concha4 #i4 ,anti-tragus4 ,let us now endeavour to explain what sound is1 and how it arises4 ,there are some curious parallels between sound and light4 ,when speaking of light we mentioned some of the analogies between sound and light1 and as we proceed to consider sound1 we will not lose sight of the light we have just passed by4 ,sound is the influence of air in motion upon the hearing or auditory nerves4 ,light1 as we have seen1 is the ether in motion1 the vibrations striking the nerves of the eye4 ,there are musical and unmusical sounds4 ,the former are audible when the vibrations of the air reach our nerves at regular intervals4 ,unmusical sounds1 or irregular vibrations1 create noise4 ,now1 musical tones bear the same relation to the ear as colours do to the eye4 ,we must have a certain number of vibrations of ether to give us a certain colour 7vide table74 8,about four hundred and fifty billion impulses in a second0 give red light4 ,the violet rays require nearly double4 ,so we obtain colours by the different rate of the impingement of impulses on the retina4 ,the eyes1 as we have already learned1 cannot receive any more rapidly-recurring impressions than those producing violet1 although as proved1 the spectrum is by no means exhausted1 even if they are invisible4 ,in the consideration of ,calorescence we pointed this out4 ,these invisible rays work great chemical changes when they get beyond violet1 and are shown to be heat4 ,so the rays which do not reach the velocity of red rays are also heat1 which is the effect of motion4 ,thus we have ,,heat1 ,,light1 and ,,sound1 all the ascertained results of vibratory motion4 ,the stillness of the ether around us is known as 8,darkness02 the stillness of the air is 8,silence02 the comparative absence of heat1 or molecular motion of bodies is 8,cold06 ,in the first part we showed how coins impart motion to each other4 ,,velocity ,,of ,,light ,,waves4 ,according to ,,sir ,j4 ,,herschel4 ,colour of the ,no4 of ,undulations ,no4 of ,undulations ,spectrum4 in an inch4 in a second4 ,extreme ,red #cg1fdj #deh1jjj1jjj1jjj1jjj ,red #ci1ahj #dgg1jjj1jjj1jjj1jjj ,intermediate #dj1gbj #die1jjj1jjj1jjj1jjj ,orange #da1faj #ejf1jjj1jjj1jjj1jjj ,intermediate #db1eaj #eag1jjj1jjj1jjj1jjj ,yellow #dd1jjj #ece1jjj1jjj1jjj1jjj ,intermediate #de1fjj #eee1jjj1jjj1jjj1jjj ,green #dg1dfj #egg1jjj1jjj1jjj1jjj ,intermediate #di1cbj #fjj1jjj1jjj1jjj1jjj ,blue #ea1aaj #fbb1jjj1jjj1jjj1jjj ,intermediate #eb1iaj #fdd1jjj1jjj1jjj1jjj ,indigo #ed1jgj #feh1jjj1jjj1jjj1jjj ,intermediate #ee1bdj #fgb1jjj1jjj1jjj1jjj ,violet #eg1dij #fii1jjj1jjj1jjj1jjj ,extreme ,violet #ei1gej #gbg1jjj1jjj1jjj1jjj ,when an impulse was given the motion was carried from coin to coin1 and at length the last one in the row flew out4 ,this is the case with sound4 ,the air molecules strike one upon another1 and the wave of 8sound0 reaches the tympanum1 and thus the impression is conveyed to the brain4 ,we say we hear--but why we hear1 in what manner the movement of certain particles affects our consciousness1 we cannot determine4 ,that the air is absolutely necessary to enable us to hear can readily be proved4 ,the experiment has frequently been made2 place a bell under the receiver of an air-pump1 and we can hear it ring4 ,but if we exhaust the air the sound will get fainter and fainter4 ,similarly1 as many of us have experienced upon high mountains1 sounds are less marked4 ,sound diminishes in its intensity1 just as heat and light do4 ,sound is reflected and refracted1 as are light and radiant heat4 ,we have already shown the effect of reflectors upon heat4 ,sound is caught and reflected in the same way as light from mirrors1 or as the heat waves in the reflectors4 ,we have what we term 8sounding boards0 in pulpits1 and speaking tubes will carry sound for us without loss of power4 ,echoes are merely reflected sounds4 ,the velocity of sound is accepted as #a1ajj feet in a second1 which is far inferior to the velocity of light4 ,fogs will retard sound1 while water will carry it4 ,those who have ever rowed upon a lake will remember how easily the sound of their voices reached from boat to boat1 and ,dr4 ,hutton says that at ,chelsea1 on the ,thames1 he heard a person reading from a distance of a hundred and forty feet4 ,some extraordinary instances could be deduced of the enormous distances sound is said to have travelled4 ,guns have been heard at eighty miles distant1 and the noise of a battle between the ,english and ,dutch1 in #afgb1 was heard even in ,wales1 a distance of two hundred miles from the scene of action4 ,sound always travels with uniform velocity in the air in the same temperature4 ,but sound6 ,what is the cause of it8 ,how does it arise8 ,these questions can now be fully answered with reference to the foregoing observations4 ,phenomena of vibration render themselves visible by light1 heat1 and sound1 and to arrive at some definite ideas of sound vibrations we may compare them to waves1 such as may be produced by throwing a stone into a pond4 ,there are1 so to speak1 8standing0 waves and 8progressive0 waves4 ,the former can be produced 7for instance7 by thrumming a fiddle-string1 and when the equilibrium of the cord is disturbed1 the position of the equilibrium is passed simultaneously by the string-waves4 ,in water the waves or vibrating points pass the position of equilibrium in succession4 ,waves consist of elevations and depressions alternately1 and when we obtain two 8systems0 of waves by throwing two stones into water1 we can observe some curious effects4 ,it can be seen how one series of depressions will come in contact with the other series of depressions1 and the elevations will likewise unite with the result of longer depressions and elevations respectively2 or it may very well be that elevation will meet depression1 and then the so-called 8interference0 of waves will produce points of repose4 ,these points are termed nodes4 ,the waves of the string proceed in the plane of its axis2 water waves extend in circles which increase in circumference4 ,the progression or propagation of sound may be said to begin when some tiny globule of matter expands in the air4 ,the air particles strike one against the other1 and so the motion is communicated to the air waves1 which in time reach the ear4 ,but the velocity of the sound is not equal in all substances4 ,air will convey it around our earth at the rate of #gfe miles an hour1 or #a1jij feet in a second4 ,that is1 we may accept such rate as correct at a temperature of #cb ,fahr41 and at a pressure of thirty inches1 and the velocity increases almost exactly one foot per second for each degree of temperature above #cb4 ,therefore on an average1 and speaking in 8round numbers10 the estimate of #a1ajj feet in a second may be accepted as correct4 ,in hydrogen gas the rate is much higher4 ,through water again it is different1 and still faster through iron1 glass1 and wood1 as will be seen in the following table3-- ,,taking ,,air ,,as #a4 ,whalebone #f ,tin #g ,silver #i ,walnut #aj ,brass #aj ,oak #aj ,earthen pipes #aa ,copper #ab ,pear-wood #ab ,ebony #ad ,cherry #ae ,willow #af ,glass #af ,iron or ,steel #af ,deal #ah ,so there is a considerable difference in the velocities of sound through the solid substances quoted1 but these figures cannot be taken as exact1 as different samples may give different results4 ,in wires and bells the bodies themselves produce the sounds we hear4 ,in wind instruments and the voice the air is the cause of the sound4 ,the very deepest notes are produced by the fewest vibrations4 ,fourteen or fifteen vibrations will give us a very low note1 if not the very lowest4 ,the pipe of sixteen feet1 closed at its upper end1 will produce sound waves of thirty-two feet4 ,high notes can be formed from vibrations up to #dh1jjj in a second4 ,beyond these limits the ear cannot accept a musical sound4 ,illustration3 ,fig4 #agb4--,the vibration of strings4 ,we will explain the phenomenon of the vibration of strings by means of the illustration4 ,in the cut we find a string or wire1 which can be lengthened or shortened at pleasure by a movable bridge1 and stretched by weights attached to the end 7fig4 #agb74 ,we can now easily perceive that the shorter and thinner the string is1 and the tighter it is1 the number of vibrations will be greater and greater4 ,the density of it is also to be considered1 and when these conditions are in the smallest proportion then the tone will be highest4 ,the depth will naturally increase with the thickness1 density1 and length1 and with a decreasing tension4 ,but we have strings of same thickness stretched to different degrees of tension1 and thus producing different notes4 ,some strings are covered with wire to increase their gravity1 and thus to produce low notes4 ,when a number of separate sounds succeed each other in very rapid course they produce a sound1 but to appear as one sound to the ear they must amount to fifteen or sixteen vibrations every second4 ,the particles of matter in the air form a connected system1 and till they are disturbed they remain in equilibrium2 but the moment they are in any way thrown out of this state they vibrate as the pendulum vibrates4 ,the particles thus strike each other1 and impart a motion to the elastic medium air1 so a sound comes to us4 ,the intensity of sounds gets less the farther it goes from us1 or the loudness of sound is less the greater its distance4 ,the law is1 that in an unvarying medium the loudness varies inversely as the square of the distance4 ,but ,poisson has shown that when air-strata1 differing in density1 are existing between the ear and the source of the sound1 the intensity or loudness with which it is heard depends only on the density of the air at the place the sound originated4 ,this fact has been substantiated by balloonists who heard a railway whistle quite distinctly when they were nearly #bj1jjj feet above the ground4 ,it therefore follows that sound can be heard in a balloon equally well as on the earth at certain given distances4 ,but as the density of the air diminishes the sound becomes fainter1 as has been proved by the bell rung in the receiver of an air-pump4 ,the velocity of sound1 to a certain extent1 depends upon its intensity1 as ,earnshaw sought to prove2 for he instanced a fact that in the ,arctic regions1 where sound can be heard for an immense distance1 in consequence of the still and homogeneous air1 the report of a cannon two miles and a half away was heard before the loud command to 8fire10 which must have preceded the discharge4 ,another instance showing the difference in hearing through mixed and homogeneous media may be referred to4 ,in the war with ,america1 when the ,english and their foes were on opposite sides of a stream1 an ,american was seen to beat his drum1 but no sound came across4 8,a coating of soft snow and a thick atmosphere absorbed the noise40 ,glazed1 or hard snow1 would have a contrary effect4 ,reynault also experimentally verified his theory1 that sound when passing through a space of nearly #h1jjj feet lost velocity as its intensity diminished1 and in that distance between its arrival at #d1jjj feet and at #g1ejj feet1 the sound velocity diminished by #bb feet per second4 ,he also tried to demonstrate that sound velocity depended upon its pitch1 and that lower notes travelled with the greater speed4 ,the reflection and refraction of sound follows the same fundamental laws as the reflection and refraction of light4 ,the reflection of sound is termed an ,echo1 which is familiar to all tourists in ,switzerland and ,ireland particularly4 ,there are several very remarkable echoes in the world3 at ,woodstock1 and at the ,sicilian cathedral of ,gergenti1 where the confessions poured forth near the door to priestly ears were heard by a man concealed behind the high altar at the opposite end4 ,it is curious that such a spot should have been accidentally chosen for the ,confessional4 ,the whispering gallery in ,st4 ,paul's is another instance of the echo4 ,echoes are produced by the reflection of sound waves from a plane or even surface4 ,a wall1 or even a cloud1 will produce echoes4 ,thunder is echoed from the clouds4 7,the celebrated echo of 8,paddy ,blake10 at ,killarney1 which1 when you say 8,how do you do10 is reported to reply1 8,very well1 thank you10 can scarcely be quoted as a scientific illustration47 ,and the hills of ,killarney contain an echo1 and the bugle sounds are beautifully repeated4 ,in the cases of ordinary echo1 when the speaker waits for the answer1 he must place himself opposite the rock4 ,if he stand at the side the echo will reply to another person in a corresponding place on the farther side1 for the voice then strikes the rock at an angle1 and the angle of reflection is the same1 as in the case of light4 ,but if it should happen that there are a number of reflecting surfaces the echo will be repeated over and over again1 as at the ,lakes of ,killarney4 ,the ,woodstock ,echo1 already referred to1 and mentioned by several writers1 repeats seventeen syllables by day1 and twenty by night4 ,in ,shipley there is even a greater repetition4 ,of course the echo is fainter1 because the waves are weaker if the reflecting surface be flat4 ,but1 as in the case of the mirrors reflecting light1 a circular or concave surface will increase the intensity4 ,a watch placed in one mirror will be heard ticking in the other focus4 ,whispering galleries carry sound by means of the curved surface4 ,sir ,john ,herschel mentions an echo in the ,menai ,suspension ,bridge4 ,the blow of a hammer on one of the main piers will produce the sound from each of the crossbeams supporting the roadway1 and from the opposite pier #egf feet distant1 as well as many other repetitions4 ,refraction of sound is caused by a wave of sound meeting another medium of different density1 just as a beam of light is refracted from water4 ,one sound wave imparts its motion to the new medium1 and the new wave travels in a different direction4 ,this change is refraction4 ,the sound waves are refracted in different directions1 according to the velocity it can acquire in the medium4 ,if a sound pass from water into air it will be bent towards the perpendicular1 because sound can travel faster in water than in air4 ,if it pass from air into water its force will cause it to assume a less perpendicular direction1 there being greater velocity in water4 ,the velocity in air is only #a1ajj feet in a second in our atmosphere4 ,in water sound travels #d1gjj feet in the same time4 ,when the wave of sound falls upon a medium parallel to the refracting surface there is1 however1 no refraction--only a change of velocity1 not direction4 ,when sound waves are prevented from dispersing the voice can be carried a great distance4 ,speaking tubes and trumpets1 as well as ear trumpets1 are examples of this principle1 and of the reflection of sound4 ,there are many very interesting experiments in connection with ,acoustics1 some of which we will now impart to our readers4 ,we shall then find many ingenious inventions to examine1--the ,audiphone1 ,telephone1 ,megaphone1 and ,phonograph1 which will occupy a separate chapter4 ,we now resume4 ,amongst the experiments usually included in the course of professors and lecturers who have a complete apparatus at their command1 and which at first appear very complicated and difficult1 there are some which can be performed with every-day articles at hand4 ,there is no experiment in acoustics more interesting than that of ,m4 ,lissajons1 which consists1 as is well known to our scientists1 of projecting upon a table or other surface1 with the aid of oxy-hydrogen light1 the vibratory curves traced by one of the prongs of a tuning-fork4 ,we can perform without difficulty a very similar experiment with the humble assistance of the common knitting-needle4 ,fix the flexible steel needle firmly in a cork1 which will give it sufficient support2 fasten then at the upper extremity a small ball of sealing wax1 or a piece of paper about the size of a large pea4 ,if the cork in which the needle is fixed be held firmly in one hand1 and you cause the needle to vibrate by striking it1 and then letting it sway of itself1 or with a pretty strong blow with a piece of wood1 you will perceive the little pellet of wax or paper describe an ellipse more or less elongated1 or even a circle will be described if the vibrations be frequent4 ,the effect is much enhanced if the experiment be performed beneath a lamp1 so that plenty of light may fall upon the vibrating needle4 ,in this case1 the persistence of impressions upon the retina admits of one seeing the vibrating circle in successive positions1 and we may almost fancy when the needle is struck with sufficient force1 that an elongated conical glass1 like the old form of champagne glass1 is rising from the cork1 as shown in the illustration annexed 7fig4 #agc74 ,illustration3 ,fig4 #agc4--;,experiment showing vibration of sound waves4 ,acoustics may be studied in the same way as other branches of physical science4 ,we will describe an interesting experiment1 which gives a very good idea of the transmission of sounds through solid bodies4 ,a silver spoon is fastened to a thread1 the ends of which are thrust into both ears1 as shown in fig4 #agd2 we then slightly swing the spoon until we make it touch the edge of the table2 the transmission of sound is in consequence so intense that we are ready to believe we are listening to the double diapason of an organ4 ,this experiment explains perfectly the transmission of spoken words by means of the string of a telephone1 another contrivance which any one may make for himself without any trouble whatever4 ,two round pieces of cardboard are fitted to two cylinders of tin-plate1 as large round as a lamp-glass1 and four-and-a-half inches in length4 ,if the two rounds of cardboard are connected by a long string of sixteen to eighteen yards1 we can transmit sounds from one end to the other of this long cord2 the speaker pronouncing the words into the first cylinder1 and the listener placing his ear against the other4 ,it is easy to demonstrate that sound takes a certain time to pass from one point to another4 ,when one sees in the distance a carpenter driving in a stake1 we find that the sound produced by the blow of the hammer against the wood only reaches the ear a few seconds after the contact of the two objects4 ,we see the flash at the firing of a gun1 before hearing the sound of the report--of course on the condition that we are at a fairly considerable distance1 as already remarked upon4 ,illustration3 ,fig4 #agd4--;,conductibility of sound by solid bodies4 ,illustration3 ,fig4 #age4--,musical glasses4 ,we can show the production of the ,gamut by cutting little pieces of wood of different sizes1 which one throws on to a table2 the sounds produced vary according to the size of the different pieces4 ,the same effect may be obtained much better by means of goblets more or less filled with water2 they are struck with a short rod1 and emit a sound which can be modified by pouring in a greater or less quantity of water2 if the performer is gifted with a musical ear1 he can obtain1 by a little arrangement1 a perfect ,gamut by means of seven glasses which each give a note 7fig4 #age74 ,a piece of music may be fairly rendered in this manner1 for the musical glasses frequently produce a very pure silvery sound4 ,we will complete the elementary principles of acoustics by describing a very curious apparatus invented by ,m4 ,tisley1 the ,,harmonograph4 ,this instrument1 which we can easily describe1 is a most interesting object of study4 ,the ,harmonograph belongs to mechanics in principle1 and to the science of acoustics in application4 ,we will first examine the apparatus itself4 ,it is composed of two pendulums1 ,a and ,b 7fig4 #agf71 fixed to suspensions4 ,pendulum ,b supports a circular plate1 ,p1 on which we may place a small sheet of paper1 as shown in the illustration4 ,this paper is fixed by means of small brass clips4 ,pendulum ,a supports a horizontal bar1 at the extremity of which is a glass tube1 ,t1 terminating at its lower extremity with a capillary opening2 this tube is filled with aniline ink1 and just rests on the sheet of paper2 the support and the tube are balanced by a counterpoise on the right4 ,the two pendulums1 ,a and ,b1 are weighted with round pieces of lead1 which can be moved at pleasure1 so that various oscillations may be obtained4 ,the ratio between the oscillations of the two pendulums may be exactly regulated by means of pendulum ,a carrying a small additional weight1 the height of which may be regulated by means of a screw and a small windlass4 ,if we give to pendulum ,a a slight movement of oscillation1 the point of tube ,t traces a straight line on the paper placed in ,p2 but if we move pendulum ,b1 the paper also is displaced1 and the point of tube ,t will trace curves1 the shape of which varies with the nature of the movement of pendulum ,b1 the relation between the oscillations of the two pendulums1 etc4 ,if the pendulums oscillate without any friction the curve will be clear1 and the point will pass indefinitely over the same track1 but when the oscillations diminish1 the curve also diminishes in size1 still preserving its form1 and tending to a point corresponding with the position of repose of the two pendulums4 ,the result is therefore that the curves traced by the apparatus1 of which we produce three specimens 7figs4 #agg1 #agh1 #agi71 are traced in a continuous stroke1 commencing with the part of the greatest amplitude4 ,illustration3 ,fig4 #agf4--,m4 ,tisley's ,harmonograph4 ,by changing the relation and phases of the oscillations we obtain curves of infinitely varied aspect4 ,m4 ,tisley has a collection of more than three thousand curves1 which we have had occasion to glance over1 in which we failed to meet with two corresponding figures4 ,the ratio between these curves corresponds with some special class1 of which the analyst may define the general characters1 but which is outside our present subject4 ,by giving the plate ,p a rotatory movement1 we obtain spiral curves of a very curious effect1 but the apparatus is more complicated4 ,considered from this point of view it constitutes an interesting mechanical apparatus1 showing the combination of oscillations1 and resolving certain questions of pure mechanics4 ,from the point of view of acoustics it constitutes a less curious object of study4 ,the experiments of ,m4 ,lissajons have proved that the vibrations of diapasons are oscillations similar to1 though much more rapid than those of the pendulum4 ,we can therefore with this apparatus reproduce all the experiments of ,m4 ,lissajons1 with this difference1 that the movements being slower are easier to study4 ,when the ratio between the number of vibrations--we purposely use the term vibration instead of the term oscillation--is a whole number1 we obtain figs4 #agg and #agh4 ,if the ratio is not exact1 we obtain fig4 #agi1 which is rather irregular in appearance1 corresponding to the distortions noticeable in ,m4 ,lissajon's experiments4 ,fig4 #agh has been traced in the exact ratio #b3c2 fig4 #agg in the ratio #a3b2 and fig4 #agi corresponds to the ratio #a3b and a small fraction1 which causes the irregularity of the figure4 ,illustration3 ,fig4 #agg4--,ratio #a3b4 ,fig4 #agh4--,ratio #b3c4 ,illustration3 ,fig4 #agi4--,ratio #a3b and a fraction4 ,illustration3 ,fig4 #ahj4 ,construction of the ,harmonograph4 ,fig4 #aha4 ,illustration3 ,fig4 #ahb4--,method of constructing an ,harmonograph4 ,illustration3 ,fig4 #ahc4--,the apparatus completed4 ,in considering the harmony of figs4 #agg and #agh1--the first of which corresponds to the octave1 the second to the fifth1 whilst fig4 #agi corresponds to the disagreeable interval of the ninth1--one is almost tempted to put a certain faith in the fundamental law of simple ratios as the basis of harmony4 ,at first sight this appears beyond doubt1 but perhaps musicians would be hardly content with the explanation4 ,m4 ,tisley's ,harmonograph1 it will be seen1 is a rather complicated apparatus2 and ,i will now explain how it may be constructed by means of a few pieces of wood4 ,i endeavoured to construct as simple an apparatus as possible1 and with the commonest materials1 feeling that it is the best means of showing how it is possible for everybody to reproduce these charming curves of musical intervals4 ,also ,i completely excluded the employment of metals1 and ,i constructed my apparatus entirely with pieces of wooden rulers1 and old cigar boxes4 ,i set to work in the following manner3 on the two consecutive sides of a drawing board ,i fixed four small pieces of wood 7fig4 #ahj71 side by side in twos1 having at the end a small piece of tin-plate forming a groove 7fig4 #aha74 ,in these grooves nails are placed which support the pendulums4 ,the piece of wood is placed on the corner of the table1 so that the pendulums which oscillate in two planes at right angles1 are in two planes that are sensibly parallel to the sides of the table4 ,the pendulums are made of a thin lath1 with two small pieces of wood fixed to them containing some very pointed nails1 on which the pendulum oscillates4 ,fig4 #ahb gives an illustration4 ,the pendulums have a pin fixed in vertically1 which passes through a piece of wood1 and by means of a hinge connects the upper ends of the two pendulums4 ,this contrivance of the pin is very useful1 and if care is taken to make the hole through the hinge in the form of a double cone1 as shown in fig4 #ahb1 c1 it makes a perfect joint1 which allows the piece of wood to be freely moved4 ,illustration3 ,fig4 #ahd4--;,details of mechanism4 ,to complete the apparatus1 the heads of the two pendulums are united by the hinge1 at the bend of which a slender glass tube is fixed1 which traces the curves4 ,the hinge is given in fig4 #ahd1 and to its two extremities are adjusted the two pins of the pendulum 7fig4 #ahc74 ,the pendulums are encircled with round pieces of lead1 which can be fixed at any height by means of a screw4 ,,chapter ,,xvi4 ,,acoustics 7,continued74 ,,the ,,topophone--,,the ,,megaphone--,,the ,,autophone--,,the ,,audiphone--,,the ,,telephone--,,the ,,phonograph--,,the ,,microphone4 ,we propose in this chapter to give as shortly as possible a description of the various instruments lately come into use1 by means of which1 and electricity1 sounds can be carried from place to place1 and their locality identified4 ,it is only within the last few years that these wonderful inventions have come into use1 and in a measure superseded the at one time invincible electric telegraph4 ,the ,telephone is now in daily use in ,london and other places1 and its novelty1 if not all its capability1 has been discounted4 ,the ,phonograph has also been frequently seen4 ,so we will on this occasion commence with the ,,topophone1 a rather novel instrument4 ,as the name indicates1 the ,,topophone is an apparatus for discovering the position of a sound1 from the ,greek words signifying a 8place0 and 8sound40 ,the sources of sound can be found by it1 and indeed this is its actual and practical use4 ,it is claimed for this new apparatus that it stands in the same relation to the sailor as his old and trusty friends1 the compass and sextant4 ,these in navigation inform the steersman as to his course1 and tells him his position by observation4 ,the ,topophone will tell him whence a sound arises1 its origin wherever it may be2 and this in a fog is no mean advantage4 ,suppose a ship to be approaching a dangerous coast in a fog4 ,we are all aware how deceptive sounds are when heard through such a medium4 ,we cannot tell from what precise direction the horn1 whistle1 or bell is sounding4 ,the ,topophone will give us the exact spot1 and we can then1 from our general knowledge of the locality1 work our vessel up the river1 or into the harbour1 in safety4 ,the ,topophone was invented in #ahhj1 by ,professor ,alfred ,mayer1 an ,american1 and is based upon the well-known theory of sound waves4 ,these1 as we have already explained1 exist in the air2 and if the theory of sound waves has perfected the ,topophone1 we can fairly say that it has confirmed the supposed form of the sound waves4 8,sound10 says the inventor of the apparatus1 8is supposed to be a particle continually expanding in the air1 composed of a wave produced by compression1 and followed by rarefaction4 ,a continuous sound is a series of these particles or globules spreading and expanding as the water-rings in a pond40 ,this much will be at once perceived4 ,now1 suppose a person up to his shoulders in a pond of water1 and someone throws a stone into it4 ,if that person extend his arms and hands at right angles facing the sound1 each hand would touch the edge of a ripple as it came towards him across the pond4 ,he would then be facing the source of the ripples or waves1 and look along a radius of the circle formed by the waves4 ,but if he please1 he can move his body so that both hands shall touch the same wave at the same time1 or he might turn away from the source1 and only one hand would touch the wave4 ,but when both hands are actually washed by the same circular ripple he must be facing the source of it4 ,any position in which his fingers did not touch the ripple almost at the same instant1 would not be facing the source of the wave ripples4 ,so by turning and extending his hands1 he could with his eyes shut find out whether he was or was not facing the original source of the waves4 ,this applied to sound waves in the air is the whole theory of the ,topophone1 which1 however1 depends for its usefulness upon the same note being sounded by all horns and whistles4 ,one note must be better than all the others1 and that note1 probably ,c 7treble71 caused by about two hundred and sixty vibrations per second1 has been found most applicable4 ,if all whistles and horns can by law be compelled to adjust themselves to this note1 then the ,topophone will be a real and lasting benefit4 ,let us now look at the apparatus itself4 ,it being conceded that the resonators are in the same key as the ,foghorn1--and this is necessary1--they are placed upon the deck of the vessel4 ,an ear-tube of indiarubber is carried from each of these 8resonators0 into the cabin4 ,these tubes unite and again separate1 ending in small pieces ready to be fitted to the ears4 ,the apparatus is fixed on deck1 and the arrangement which supports it passes into the cabin1 and can be turned about in any direction4 ,of course in this case a dial point is necessary to indicate the direction in which the instrument is turned4 ,if the machine be worn on the shoulders of the officer of the watch he can move as he pleases1 and wants no indicator4 ,the ,topophone when used is so constructed1 that when a horn is heard1 and when the listener is facing the sound1 he can hear nothing6 ,when not facing the origin of the sound he can hear the horn very well1 but the moment the resonators receive the sound together as they face the source1 a very low murmur is heard1 or perhaps no sound at all4--,why8 ,a certain pitch of tone is composed of vibrations or waves of equal length4 ,in all waves there is a hollow and a crest4 ,one neutralizes the other4 ,the hollow of a sound wave meeting the crest of another wave 8interferes0 to produce silence1 stillness1 a dead level4 ,so in 8light02 two rays will produce darkness4 ,we will endeavour to explain this4 ,if we have two equal strings1 each performing an equal number of vibrations in a second1 they will produce equal sound waves1 and the sound produced by both together will be uninterrupted1 and twice as loud as one of them4 ,but if one string vibrate1 say one hundred times1 and the other one hundred and one times in a second1 they will not be in unison1 and one will gain upon the other string1 till after it has got to fifty vibrations it will be half a vibration ahead4 ,at that moment they will neutralize each other1 and silence will ensue for an appreciable time4 ,illustration3 ,fig4 #ahe4--,the ,megaphone4 ,in the case of light suppose a red ray strikes the eye1 and another red ray to come upon it from somewhere else4 ,if the difference between its distance and the other point from the spot in the retina on which the first ray fell1 is the #beh_/ajjj part of an inch1 or exactly twice1 thrice1 four times as much1 etc41 that distance1 the light will be seen twice as strong4 ,but if the difference in the distances between the points whence the light comes be only one-half the #beh_/ajjj part of an inch1 or #a1 #b1 #c1 or #d times that distance1 one light will extinguish the other1 and darkness will be the result4 ,now this is precisely what happens in the case of the ,topophone4 ,to return to our simile of water waves4 ,if two stones be cast into a pond1 and two equal and similar waves produced1 and if they reach a certain place at the same moment1 they will make one large wave4 ,but if one followed the other a little1 so that the hollow of one coincided with the crest of the other1 and vice vers1 the waves would obliterate each other1 and a dead level would result4 ,one tube of the ,topophone is half a wave length longer than the other1 and when the resonators are in a line and receive the wave at the same time1 one ear hears the elevation of the sound wave1 and the other the depression1--the sound is neutralized1 and comparative1 if not actual1 silence results4 ,the sailor knows in what direction the land lies1 and can calculate his distance1 or anchor if he please4 ,if amongst our readers there be any who wish to make for themselves an acoustic signalling apparatus there is physically nothing to prevent them from constructing such an instrument as that shown in the annexed woodcut 7fig4 #ahe74 ,it is founded upon the speaking-trumpet principle1 which is supposed to have been originated by ,samuel ,markland1 in #afgj4 ,kircher1 in his 8,ars magna et umbra10 and in his 8,phonurgia10 mentions a kind of speaking-trumpet1 or porte voix1 of gigantic dimensions1 and called the 8,horn of ,alexander40 ,according to ,kircher1 the instrument was used by ,alexander the ,great to summon his soldiers from a distance of ten miles4 ,the diameter of the circumference was about eight feet1 and ,kircher conjectured that the instrument was mounted upon three supports4 ,during the last century1 a ,german professor1 named ,huth1 made a model of the horn1 and found it answered every purpose of a speaking-trumpet with most powerful results1 but we beg leave to doubt whether the instrument really carried the voice to any very great distance4 ,the ,acoustic ,cornet1 which is the counterpart of the speaking-trumpet1 has been made in many different forms during the last two centuries1 but none of them to the present time consist of anything more intricate than a simple tube with a mouthpiece and bell-shaped orifice4 ,professor ,edison1 however1 in his researches regarding the conveyance of sounds1 has made numerous and interesting experiments4 ,on one occasion1 with his ,megaphone he carried on a conversation at a distance of nearly two miles1 without any other assistance from instruments except a few little cornets of cardboard4 ,these constitute the ,megaphone1 which may be regarded as a curiosity1 considering the effects produced by such simple means4 ,the illustration 7fig4 #ahe7 represents the instrument which is 7or was lately7 fixed upon the balcony of ,mr4 ,edison's house4 ,at a mile-and-a-half distant from the house1 at a spot indicated by the two birds in the picture1 another instrument was fixed1 and conversation was carried on with ease4 ,perhaps the present opportunity will be the most convenient to speak of the ,,autophone1 although it is more a musical than an acoustic instrument4 ,until lately ,barbary organs and piano organs have been the only means by which poor people have been able to hear any music1 and that not of a very elevated class4 ,besides1 there is a good deal of expense connected with the possession of an organ4 ,but the ,americans1 with a view to popularize music1 have invented the ,,autophone1 which is simply a mechanical accordeon1 manufactured by the ,autophone ,company1 of ,ithaca1 ,new ,york4 ,the principle of the instrument is represented in fig4 #ahf1 and is extremely simple4 ,an upright frame carries within it on one side a bellows1 and on the other a flexible air chamber1 which serves as a reservoir4 ,the upper portion contains a set of stops like an accordeon1 but the escape of the air through the small vibrating plates can only take place by the upper surface of the frame work1 upon which slides a thin plate of ,bristol board pierced with holes at convenient distances1 and set in motion by the mechanism shown in the annexed diagram 7fig4 #ahg74 ,illustration3 ,fig4 #ahf4--,the ,autophone4 ,the figure represents an axle furnished with a series of 8washers10 which1 acting upon the plate1 cause it to move round4 ,it is the bellows movement that turns the axle by the aid of two 8catches10 ,b and ,c1 which work upon a toothed wheel fixed upon it4 ,the 8catch0 ,b moves the paper on which the tune is 8perforated10 when the bellows is empty1 the other catch when it is distended2 but a counter catch1 ,d1 represented by the dotted lines in the illustration1 is so arranged that the paper cannot pass on except the tooth of the catch ,d is opposite a hole pierced upon the plate above4 ,in the contrary case there is no movement of the paper during the dilatation of the bellows4 ,the effect of this very ingenious arrangement is to give to the 8musical0 band of 8board0 an irregular movement1 but it economises it in the case of sustained notes4 ,the whole action of the instrument depends upon the correct working of the bellows4 ,the effect1 from an artistic point of view1 certainly leaves something to be desired1 but the instrument is cheap1 and not cumbersome1 and the slips of paper upon which the music is 8cut out0 can be made by machinery1 and consequently are not dear4 ,so far1 the ,autophone is fitted for popular favour and use1 and may supersede the barrel organ4 ,illustration3 ,fig4 #ahg4--;,detail of the ,autophone4 ,the ,,audiphone is an instrument to conduct sound to the ear1 to supplement it when temporary or partial deafness has occurred4 ,very likely many of our readers have observed ladies carrying large black fans on occasions1--at church1 or lecture1 or theatre1--and wondered why1 perhaps4 ,those 8fans0 are ,audiphones4 ,the instrument is made of vulcanized rubber1 and consists of a long flexible disc supported by a handle4 ,to the upper edge of the 8fan0 are attached cords1 which pass through a clip on the handle4 ,if the person who wishes to hear by means of the ,audiphone will hold the fan against the upper teeth1--the convex side of the fan outward1--he or she will hear distinctly1 for the vibrations of sound are collected and strike upon the teeth and bones1 and act upon the auditory nerves from within1 precisely as the vibrations act from without through the auricle4 ,we need hardly add that if the ear be injured the ,audiphone will be of no use4 ,a writer says3 8,from personal observation with the ,audiphone it appears to convey the sonorous vibrations to the ear through the teeth1 just as a long wooden rod held in the teeth will convey the vibrations of the sounding-board of a piano1 though the piano is in another room and out of hearing by the ear4 ,in using the ,audiphone during conversation there is no movement or vibration felt by the teeth2 in listening to a piano there is a very faint sensation as if the ,audiphone vibrated slightly1 while with the handle of the ,audiphone resting on the sounding-board of the piano the vibrations are so violent as to be painful to the teeth4 ,by closing the ears a person with even acute hearing can observe the admirable manner in which the instrument conveys spoken words to the ear4 ,the ,audiphone will prove to be of great value to deaf mutes1 as it enables them to hear their own voices1 and thus to train them to express words1 while1 before1 they could only make inarticulate sounds40 ,we have a variation of this instrument which has been introduced employing a diaphragm held in a telephone mouthpiece1 and free to vibrate under the influence of sounds4 ,this is connected by a string to a bit of wood that may be held in the teeth4 ,in use the hearer places the wood between his teeth1 the string is drawn tight1 and the speaker speaks through the telephone mouthpiece1 the vibrations of the diaphragm being then conveyed to the teeth through the stretched string4 ,this apparatus works very successfully1 and ladies use it1 but it is not so convenient for general use as the ,audiphone4 ,illustration3 ,fig4 #ahh4--,the ,telephone4 ,the ,telephone is now in daily use in ,london1 and is by no means strange to the majority of our countrymen1 still some description of it will probably be acceptable1 and a glance at its history may prove interesting4 ,illustration3 ,fig4 #ahi4--,the 8receiving0 apparatus4 ,in speaking of the ,telephone1 we must not lose sight of the facts before mentioned1 as regards our sense of hearing1 and the manner in which the ear acts by the series of bones termed the hammer1 the anvil1 and stirrup4 ,in the process of reproduction of tone in the magnetic instruments1 the mechanism of the human ear was1 to a certain extent1 imitated1 and a diaphragm1 by vibrations1 generates and controls an electric current4 ,professor ,wheatstone was the first person to employ the electric wire for the transmission of sounds1 but ,professor ,philip ,reiss1 of ,friedrichsdorf1 was the first to make the experiment of producing musical sounds at a distance4 ,his first instrument was of a most primitive nature2 subsequently he produced an instrument of which fig4 #ahh is the ,telephone1 fig4 #ahi the 8receiver40 ,in fig4 #ahh1 it will be seen that there is an aperture on the top and one at the side2 the latter is the mouthpiece4 ,the top aperture is covered with a membrane which is stretched very tightly4 ,when a person speaks or sings into the mouthpiece his voice is at once concentrated upon the tight membrane1 which it causes to vibrate in a manner corresponding with the vibrations of the voice4 ,there are two binding screws1 one at each side4 ,to the centre of the tight membrane a piece of platinum is fixed1 and this is connected with the binding screw on one side1 in which a wire from the battery is fixed4 ,on the membrane is a tripod1 the feet of which 7two7 rest in metal cups1 one of them being in a mercury cup connected with the binding screw at the opposite side to that already mentioned4 ,the third 8foot0--a platinum point--is on the platinum in the centre of the membrane or top1 and moves with it4 ,every time the membrane is stretched by a vibration the platinum point is touched1 and the closed circuit is broken by the return of each vibration4 ,illustration3 ,fig4 #aij4--;,bell's first ,telephone 7,transmitter74 a4 ,electro-magnet4 b4 ,diaphragm4 c4 ,collar4 d4 ,collar and tube4 f4 ,screw4 g4 ,mouthpiece4 h4 ,battery4 i4 ,wire from battery to coil4 k4 ,telegraph wire4 l4 ,through binding screw4 m4 ,pillar holding magnet4 ,the receiving instrument 7fig4 #ahi7 consists of a coil enclosing an iron rod1 and fixed upon a hollow sounding box4 ,it is founded upon a fact discovered by ,professor ,henry1 that iron bars when magnetized by an electric current become a little longer1 and at the interruption of the current resume their former length4 ,thus in the receiver the iron will become alternately longer and shorter in accordance with the vibrations of the membrane in the box far away1 and so the longitudinal vibrations of the bar of iron will be communicated to the sounding box1 and become perfectly audible4 ,this instrument1 however1 could only produce the 8pitch0 of sound1 8not different degrees of intensity1 or other qualities of tones40 ,it merely sang with its own little trumpet whatever was sung into it2 for all the waves were produced by an electric current of a certain and uniform strength1 and therefore the sound waves were of the same size4 ,but in #ahgd1 ,mr4 ,elisha ,gray1 of ,chicago1 improved ,reiss' instrument1 and discovered a method by which the intensity or loudness of tones1 as well as their 8pitch10 were transmitted and reproduced4 ,in this method he employed electrical vibrations of varying strength and rapidity1 and so was enabled to reproduce a tune4 ,subsequently he conceived the notion of controlling the vibrations by means of a diaphragm1 which responded to every known sound1 and by this he managed to transmit speech in an articulate manner4 ,illustration3 ,fig4 #aia4--;,bell's ,telephone 7,receiver74 ,in #ahgf1 ,professor ,graham ,bell sent a ,telephone to the ,centennial ,exhibition at ,philadelphia4 ,mr4 ,bell1 according to the report1 managed to produce a variation of strength of current in exact proportion to the particle of air moved by the sound4 ,a piece of iron attached to a membrane1 and moved to and fro in proximity to an electro magnet1 proved successful4 ,the battery and wire of the electro magnet are in circuit with the telegraph wire1 and the wire of another electro magnet at the receiving station4 ,this second magnet has a solid bar of iron for core1 which is connected at one end1 by a thick disc of iron1 to an iron tube surrounding the coil and bar4 ,the free circular end of the tube constitutes one pole of the electro magnet1 and the adjacent free end of the bar core the other4 ,a thin circular iron disc held pressed against the end of the tube by the electro-magnetic attraction1 and free to vibrate through a very small space without touching the central pole1 constitutes the sounder by which the electric effect is reconverted into sound4 ,the accompanying illustrations 7figs4 #aij1 #aia7 show ,mr4 ,bell's ,telephone as described4 ,the ,telephone1 subsequently simplified by ,professor ,bell1 is shown in the two following illustrations 7figs4 #aib1 #aic74 ,the voice strikes against the diaphragm1 and it begins to vibrate4 ,the sound is not conveyed by the wire2 the motion is communicated1 and the vibrations become sound waves again4 ,the ,telephone consists of a cylindrical magnet encircled at one end by a bobbin1 on which is wound a quantity of fine insulated copper wire4 ,the magnet and coil are contained in a wooden case1 the ends of the coil being soldered to thick copper wire1 which traverse the 8wooden envelope10 and terminate in the binding screws4 ,in front of the magnet is a thin circular iron plate1 in which is the mouthpiece4 ,the drawings will explain the instrument4 ,illustration3 ,fig4 #aib4--;,external appearance of ,bell ,telephone4 ,illustration3 ,fig4 #aic4--;a4 ,bobbin of coil wire round magnet4 b4 ,diaphragm4 c4 ,mouthpiece4 d4 ,permanent magnet4 e4 ,wires to binding screws4 f4 ,both wires as one for convenience4 g4 ,adjusting screw-holding magnet4 ,mr4 ,edison also invented a ,telephone like ,gray's1 and made the discovery1 that when properly prepared1 carbon would change its resistance with pressure1 and that the ratio of these changes corresponded with the pressure4 ,this solved the problem of the production of speech4 ,the carbon is placed between two plates of platinum connected in the circuit and near the diaphragm1 and the carbon receives the pressure from it by means of the mouthpiece4 ,when we come to ,,magnetism and ,,electricity we may have something more to say respecting the mysteries of the ,telephone and its later developments4 ,at present we are only concerned with it as a sound conveyer1 and it answers its purpose admirably1 although somewhat liable to attract other sounds or vibrations from neighbouring wires4 ,the ,,phonograph1 a mechanical invention of ,mr4 ,edison1 does not make use of electricity1 although the vibratory motion of the diaphragm is utilized4 ,it1 in a simple form1 consists of a diaphragm so arranged as to operate upon a small stylus1 placed just opposite and below the centre1 and a brass cylinder1 six or eight inches long1 by three or four in diameter1 mounted upon a horizontal axis1 extending each way beyond its ends for a distance about its own length4 8,a spiral groove is cut in the circumference of the cylinder1 from one end to the other1 each spiral of the groove being separated from its neighbour by about one-tenth of an inch4 ,the shaft or axis is also cut by a screw thread corresponding to the spiral groove of the cylinder1 and works in screw bearings2 consequently when the cylinder is caused to revolve1 by means of a crank that is fitted to the axis for this purpose1 it receives a forward or backward movement of about one-tenth of an inch for every turn of the same1 the direction1 of course1 depending upon the way the crank is turned4 ,the diaphragm is firmly supported by an upright casting capable of adjustment1 and so arranged that it may be removed altogether when necessary4 ,when in use1 however1 it is clamped in a fixed position above or in front of the cylinder1 thus bringing the stylus always opposite the groove as the cylinder is turned4 ,a small1 flat spring attached to the casting extends underneath the diaphragm as far as its centre and carries the stylus1 and between the diaphragm and spring a small piece of india-rubber is placed to modify the action1 it having been found that better results are obtained by this means than when the stylus is rigidly attached to the diaphragm itself4 ,illustration3 ,fig4 #aid4--,mode of using the ,telephone4 8,the action of the apparatus will now be readily understood from what follows4 ,the cylinder is first very smoothly covered with tin-foil1 and the diaphragm securely fastened in place by clamping its support to the base of the instrument4 ,when this has been properly done1 the stylus should lightly press against that part of the foil over the groove4 ,the crank is now turned1 while1 at the same time1 someone speaks into the mouthpiece of the instrument1 which will cause the diaphragm to vibrate1 and as the vibrations of the latter correspond with the movements of the air producing them1 the soft and yielding foil will become marked along the line of the groove by a series of indentations of different depths1 varying with the amplitude of the vibrations of the diaphragm2 or in other words1 with the inflections or modulations of the speaker's voice4 ,these inflections may therefore be looked upon as a sort of visible speech1 which1 in fact1 they really are4 ,if now the diaphragm is removed1 by loosening the clamp1 and the cylinder then turned back to the starting point1 we have only to replace the diaphragm and turn in the same direction as at first1 to hear repeated all that has been spoken into the mouthpiece of the apparatus2 the stylus1 by this means1 being caused to traverse its former path1 and consequently1 rising and falling with the depressions in the foil1 its motion is communicated to the diaphragm1 and thence through the intervening air to the ear1 where the sensation of sound is produced4 ,illustration3 ,fig4 #aie4--;,,bell',s ,,long-,,distance ,,telephone a4 ,compound magnet4 d4 ,diaphragm4 e4 ,speaking tube4 f4 ,telegraph wire4 g4 ,line to earth4 b1 c4 ,small spaces4 8,as the faithful reproduction of a sound is in reality nothing more than a reproduction of similar acoustic vibrations in a given time1 it at once becomes evident that the cylinder should be made to revolve with absolute uniformity at all times1 otherwise a difference more or less marked between the original sound and the reproduction will become manifest4 ,to secure this uniformity of motion1 and produce a practically working machine for automatically recording speeches1 vocal and instrumental music1 and perfectly reproducing the same1 the inventor devised an apparatus in which a plate replaces the cylinder4 ,this plate1 which is ten inches in diameter1 has a volute spiral groove cut in its surface on both sides from its centre to within one inch of its outer edge2 an arm guided by the spiral upon the under side of the plate carries a diaphragm and mouthpiece at its extreme end4 ,if the arm be placed near the centre of the plate and the latter rotated1 the motion will cause the arm to follow the spiral outward to the edge4 ,a spring and train of wheel-work regulated by a friction governor serves to give uniform motion to the plate4 ,the sheet upon which the record is made is of tin-foil4 ,this is fastened to a paper frame1 made by cutting a nine-inch disc from a square piece of paper of the same dimensions as the plate4 ,four pins upon the plate pass through corresponding eyelet-holes punched in the four corners of the paper1 when the latter is laid upon it1 and thus secure accurate registration1 while a clamping-frame hinged to the plate fastens the foil and its paper frame securely to the latter4 ,the mechanism is so arranged that the plate may be started and stopped instantly1 or its motion reversed at will1 thus giving the greatest convenience to both speaker and copyist4 8,the articulation and quality of the ,phonograph1 although not yet perfect1 is full as good as the ,telephone was4 ,the instrument1 when perfected and moved by clock-work1 will undoubtedly reproduce every condition of the human voice1 including the whole world of expression in speech and song1 and will be used universally4 8,the sheet of tin-foil or other plastic material receiving the impressions of sound1 will be stereotyped or electrotyped so as to be multiplied and made durable2 or the cylinder will be made of a material plastic when used1 and hardening afterward4 ,thin sheets of papier mach1 or of various substances which soften by heat1 would be of this character4 ,having provided thus for the durability of the ,phonograph plate1 it will be very easy to make it separable from the cylinder producing it1 and attachable to a corresponding cylinder anywhere and at any time4 ,there will doubtless be a standard of diameter and pitch of screw for ,phonograph cylinders4 ,friends at a distance will then send to each other ,phonograph letters1 which will talk at any time in the friend's voice when put upon the instrument40 7,scribner47 ,the ,,microphone 7an outcome of the ,telephone7 was discovered by ,professor ,hughes1 of ,london4 ,it is an instrument which in its main features consists of a carbon 8pencil10 so suspended that one end rests upon a carbon 8die40 ,the instrument being connected with a ,telephone by the circuit wires1 will reproduce faint sounds very distinctly4 ,once a ,microphone was put into a preacher's pulpit1 and joined to a private telegraph wire which led to a gentleman's house4 ,the owner was thus enabled to hear the sermon4 ,so long as it is thus connected every minute sound1 even a fly's footstep1 will be faithfully reproduced4 ,,chapter ,,xvii4 ,,the ,,tuning-,,fork--,,the ,,syren--,,sound ,,figures--,,singing ,,flames4 ,we cannot close the subject of ,sound without some mention of the ,musical ,pitch1 and various instruments and experiments which have from time to time been made to discover the pitch1 sound1 and vibrations1 and even to see ,sound4 ,to understand the vibrations or 8pitch0 of a musical note we may study the illustration1 which shows us a tuning-fork in vibration4 ,you will perceive that each prong of the tuning-fork beats the air in an opposite direction at the same time1 say from a to b 7fig4 #aif74 ,the prong strikes the air1 and the wave thus created strikes again outward1 and the condensation thus created travels along the back beat1 rarefying the air1 and both these1 the rarefaction and the condensation1 move with the same rapidity one behind the other4 ,illustration3 ,fig4 #aif4 ,illustration3 ,fig4 #aig4 ,the tuning-fork of course vibrates a very great many times in a second1 every vibration generating a wave4 8,pitch10 in a general sense1 is the number of vibrations per second which constitute a note4 ,for instance1 the note ,a1 the standard pitch consists of four hundred and thirty-five complete vibrations per second4 ,concert pitch is slightly higher1 for there are a few more vibrations in the second4 ,the lowest sound pitch is forty vibrations1 the highest forty thousand4 8,pitch0 may be determined by an instrument termed the 8,syren10 or by a tooth-wheeled apparatus4 ,the ,,syren was invented by ,cagniard de ,latour4 ,it consists of a metal cylinder1 a tube passes through the bottom1 and through the tube air is blown into the cylinder4 ,on the top a number of holes are drilled1 while just over the cylinder top1 almost in contact with it1 is a metallic disc1 which rotates upon a vertical axis4 ,the disc is perforated with holes equal in number to those in the cylinder top1 but the holes are not perpendicular1 they slope in opposite directions4 ,so when the air is forced through the holes in the top of the cylinder it impinges upon one side of the holes in the rotating disc1 and blows it round4 ,the disc in one revolution will therefore open and shut as many holes as there are in the disc and cylinder1 and the air blown in will escape in so many puffs--the number of puffs in a given time depending upon the rapidity of rotation4 ,there is an arrangement to show the number of turns4 ,by these rotations a sound is produced which rises in pitch as the revolutions are increased in number4 ,illustration3 ,fig4 #aih4 ,sound ,figures4 ,fig4 #aii4 ,to determine the pitch of a certain sound we must find the number of times the plate revolves in that time1 then we shall have the number of vibrations per second required to produce the note we desire4 ,the arrangement working in a notched wheel tells us the number of rotations of the disc4 ,successive1 and rapidly-successive puffs or beats are heard as the rotation increases1 and at length the two sounds will disappear1 and merge into one1 which is perhaps that of the tuning-fork1 whose note you require to find the 8pitch0 of4 ,by maintaining this rate for a minute or less1 and setting the gear to tell the revolutions1 the number will be found marked on the dial of the apparatus4 ,so by multiplying the number of revolutions of the disc by the number of the holes1 and dividing the product by the number of seconds during which the disc was in connection with the recording gear1 we shall have the number of vibrations per second necessary to produce the pitch corresponding to the given sound4 ,the above is the description of one form of ,syren2 there are others1 which1 however1 we need not detail4 ,we have seen that there are certain nodal points1 or resting-places1 in vibrations1 and this can easily be shown upon a fiddle-string1 from which paper discs will fall off except on the nodal point1 showing that there is no vibration there4 ,the same experiment may be made by means of plates1 which will give us what are termed ,chladni's figures4 ,suppose we strew a glass-plate with fine sand1 and stroke the edge with a fiddle-bow4 ,the vibrations of the plates will make certain patterns1 and cast the sand upon those points of repose to form nodal lines in various directions4 ,the plates must1 of course1 be held or fastened1 and a variety of sound figures may be produced4 7,see figs4 #aih and #aii47 ,the relation between the number of segments on the plate and the pitch of the note1 can be ascertained by using a circular plate clamped in the centre4 8,if the finger on the plate and the fiddle-bow are one-eighth of the circumference apart1 the fundamental note will be produced4 ,if one-sixteenth apart1 the higher octave will be heard40 ,sensitive flames will detect air vibrations1 and flames can also be made to sing4 ,sensitive flames were discovered by ,mr4 ,barrett1 who noticed the effect a shrill note had upon a gas flame from a tapering jet4 ,the flame was a very long one 7fourteen inches71 and when the sound was produced it shortened at once1 while the upper part expanded like a fan2 the same effects1 in a less marked degree1 were observable when the shrill sound was prolonged from a distance of forty feet4 ,professor ,tyndall was immediately interested in this discovery1 and in ,january #ahfg he lectured upon it at the ,royal ,institution4 ,if any one wish to try the experiment1 a piece of glass tubing should be obtained1 and let the mouth be tapered down to a small orifice one-sixteenth of an inch in diameter4 ,then when the highest pressure is on for the evening1 light the gas and sound a shrill whistle4 ,the flame will sink down and spread out4 ,the illuminating power may thus be increased1 and many experiments may be made4 ,for instance1 if a person be in the room and try to read1 he will probably not be able to do so at a little distance2 but if his friend whistle to the gas it will so expand itself as to enable him to read1 so long as the whistle lasts4 ,a very ingenious burglar-detector was made upon the principle of the sensitive flame1 which expands at a noise and heats a welded plate of gold1 silver1 and platinum4 ,the plate swerves aside1 the metals being unequally affected by heat1 and as it is connected with a battery1 rings a bell by electricity4 ,a small high flame has been made sensitive to the chinking of coin1 or even to the ticking of a watch4 ,we will now give some explanation1 derived partly from ,professor ,tyndall1 of the cause of sensitive flames4 ,a sensitive flame is one just on the point of 8roaring10 and about to change its aspect4 8,it stands10 says ,tyndall1 8on the edge of a precipice4 ,the proper sound pushes it over4444 ,we bring it to the verge of falling1 and the sonorous pulses precipitate what was already imminent40 ,the flame is in a state of vibration1 so sounds being vibrations1 practically increase the pressure2 and the flame acknowledges the pressure thus invisibly applied by air waves4 ,,singing ,,flames are produced by burning hydrogen in a tube2 a musical note is thus produced in the same way as the air causes a note in an organ pipe4 ,faraday attributed the sound to rapid vibration caused by successive explosions of the burning gas4 ,the ,gas ,harmonicon has been made on this principle4 ,the air1 being heated in the glass tube1 ascends1 and the flame is thus permitted to come up more forcibly in the tube2 so violent agitation results when the air tries to get into the opening above4 ,the size of the flame and its position in the tube will give a certain note which will be the same note as the air would emit if in a pipe1 for the vibrations give the sound4 ,sir ,charles ,wheatstone has shown by experiment how sound can be transmitted by placing a rod on a musical-box1 and carrying the rod through the ceiling4 ,when a guitar or violin was placed upon the rod1 the sounds of the musical-box were distinctly heard in the upper room4 ,a ,phantom ,band can be made by connecting certain instruments with others being played on under the stage4 ,every one will then appear to play by itself4 ,,chapter ,,xviii ,,electricity4 ,,derivation ,,of ,,electricity--,,sealing-,,wax ,,experiment--,,the ,,electrophorus--,,leyden ,,jar--,,positive ,,and ,,negative--,,the ,,electroscope--,,electric ,,machines4 ,we have now briefly and of course imperfectly reviewed the phenomena of ,vibration1 as exemplified in what we term ,heat1 ,light1 and ,sound4 ,we now come to a most mysterious servant of mankind1 as mysterious as any ,djinn of romance2 viz41 ,,electricity4 ,the term ,electricity is derived from the ,greek word electron1 meaning 8amber02 because from amber the properties of what we call 8,electricity0 were first discovered4 ,six hundred years before the ,christian ,era1 ,thales wrote concerning the attraction which amber1 when rubbed1 possessed for light and dry bodies4 ,but it is to an ,englishman named ,gilbert that we owe the word 8,electricity10 which he derived from the ,greek1 and in his works 7about #afjj ,a4,d47 he discusses the force of the so-called 8fluid40 ,otto von ,guerike1 of 8air-pump0 celebrity1 and many other philosophers after him1 continued the investigation of the subject4 ,at the beginning of the last century great attention was paid to the ,electric ,machine4 ,the ,leyden ,jar was1 as its name denotes1 discovered by ,muschenbrock1 of ,leyden1 7though the honour was disputed74 ,franklin made the first lightning conductor in #agfj4 ,volta and ,galvani1 to whose invention we owe 8,voltaic ,electricity0 and 8,galvanism10 and ,faraday in more modern times gave a great impetus to electrical science4 ,the great part that electricity has been playing in the domestic history of the world since ,faraday's lamented death1 is probably known to the youngest of our readers4 ,what the future of this agent may be we can only guess1 but even now we may regard electricity as only in its infancy4 ,there are few scientific studies more attractive to the general reader than electricity1 and few admit of more popular demonstration4 ,the success of the late electrical exhibition in ,paris1 and its successor in ,london at the present time1 are proofs of the interest taken in this great and mysterious agent whose origin we are in ignorance of1 and of whose nature and powers we are daily discovering more and more1 and finding there is still an immense field for its application4 ,some fundamental facts regarding electricity may very easily be studied with the assistance of every-day objects at hand4 ,amber was the first substance to show attraction when rubbed1 but ,gilbert found out that glass and sealing-wax1 etc41 possessed like properties with amber4 ,if we rub a stick of sealing-wax with a piece of cloth1 we shall see that it will attract some small fragments of paper placed near it4 ,nothing is easier than to construct a small pendulum to show with perfect clearness the phenomenon of electric attraction4 ,a piece of iron is fixed on a wooden pedestal1 and supports a thread of silk1 to the end of which is fastened a little ball cut out of a piece of cork4 ,the stick of sealing-wax after being rubbed with the cloth will attract the ball as shown in fig4 #bjj4 ,illustration3 ,fig4 #bjj4--,sealing-wax attracting a piece of cork4 ,by means of a piece of paper we can produce a spark4 ,i take a large1 strong sheet of drawing paper1 heat it very thoroughly1 and lay it on a wooden table4 ,i rub it with a perfectly dry hand1 or with a piece of woollen material until it adheres to the table4 ,that done1 ,i place a bunch of keys in the centre of the sheet of paper1 which ,i raise1 lifting it by two corners4 ,if at this moment any one touches the bunch of keys with his finger1 a bright spark will be elicited4 ,the metal is charged with the electricity developed on the paper2 if the weather is dry1 and the paper thoroughly heated several times1 the spark may attain nearly an inch in length4 ,we can easily construct other electrical apparatus4 ,for instance1 an 8,electrophorus10 or instrument for obtaining electricity by means of induction1 or a ,leyden jar1 can both be made at home4 ,let us proceed to construct the former1 of which we give an illustration 7fig4 #bja74 ,we take a lacquered tea-tray about a foot long1 and cut out a sheet of thick wrapping paper1 so that it will lie over all the level portion of the tray4 ,at each side of this sheet of paper we fix two bands of paper1 as in the illustration 7fig4 #bja71 so as to serve as handles4 ,the tea-tray should be placed upon two tumblers to support it and to insulate it1 glass being a 8non-conductor40 7,we will speak of conductors and non-conductors presently47 ,we have now our ,electrophorus made ready for action2 let us proceed to see how it will act4 ,illustration3 ,fig4 #bja--,simple ,electrophorus4 ,first1 rub the thick packing paper over a hot fire or a stove1 and the friction must be continued for some time1 until the paper has become thoroughly dry1 and as hot as possible without charring4 ,when this has been accomplished1 place it quickly upon a wooden table1 and rub it rapidly and energetically with a clothes' brush1 dry and hard as can be obtained4 ,place the paper upon the tray2 touch the tray with the knuckle1 and draw away the paper by the handles fixed to it 7see fig4 #bja72 a spark will result4 ,then if the paper be replaced upon the tray1 and the hand again presented1 the same result will follow4 ,this experiment may be repeated five or six times1 at least1 with success4 ,we have in this tea-tray and its paper covering a real electric machine4 ,how can we manage to provide a ,leyden jar to contain our electricity8 ,nothing is more easy4 ,let us take a tumbler and partly fill it with shot2 insert into the glass a tea-spoon1 and if all the articles are quite dry we shall possess a ,leyden jar4 ,to charge the jar we have thus provided we must work the ,electrophorus we have already described4 ,while one person lifts off the paper as directed1 another must hold the glass filled with shot close to the edge of the tray1 and touch the corner with the tea-spoon2 the spark will then enter the 8jar0 or tumbler4 ,we can thus charge the jar as we please1 and by presenting the finger as in the illustration 7fig4 #bjb71 we shall obtain a discharge from it4 ,illustration3 ,fig4 #bjb4--;,a ,leyden jar4 ,mr4 ,louis ,figuier1 in his 8,merveilles de la ,science10 relates that ,wollaston1 meeting one of his friends one evening in the streets of ,london1 drew from his pocket a copper thimble1 and proceeded to turn it into a microscopic pile4#ac ,in order to do this he removed the bottom of the thimble1 flattened it with a stone1 so as to bring the two internal surfaces about on a line with each other1 then placed between the copper surfaces a small strip of zinc1 which was not in contact with the copper1 owing to the interposition of a little sealing-wax4 ,he then placed it in a glass cup1 previously filled with the contents of a small phial of water1 acidulated with sulphuric acid4 ,he next wound round the strip of zinc and its copper covering a piece of platinum wire1 the wire becoming red through the electricity developed in the pile4 ,the dimensions of this platinum wire were extremely small2 it was only #cj_/ajjj of an inch in diameter1 and #a_/cj of an inch in length4 ,by reason of its small dimensions it could not only be reddened1 but fused by the little battery4 ,thus ,wollaston's friend1 who was a witness of the experiment1 was able to light a tinder at the red wire4 ,in this little battery of ,wollaston's the copper enveloped the strip of zinc in every part2 that is to say1 the negative element was on a higher surface than the positive metal4 ,illustration3 ,fig4 #bjc4-;,a simple compass4 ,after considering ,electricity1 it is not impossible to approach the study of ,magnetism1 and even to construct a mariner's compass4 ,we shall find the method of doing so by borrowing an interesting passage from the 8,magasin ,pittoresque40 ,let us take a small cork and pass through it an ordinary knitting-needle 7fig4 #bjc71 which we have already magnetized by placing it ,n4,s41 rubbing it gently1 and always in the same direction1 with one of those little iron magnets with which children amuse themselves4 ,after the needle has been passed through the cork1 we also fix into it a sewing-needle1 or rather a pin1 the point of which rests in one of the little holes in the upper part of the thimble4 ,in order to balance the magnetised needle1 we thrust a match into both sides of the cork1 as shown in the illustration1 and fasten to the ends of each a ball of wax4 ,thus the needle1 the balls1 and the pin are all balanced at once1 so that the contrivance has the appearance of the illustration4 ,as it is very important that with such a sensitive instrument any agitation of the air should be avoided1 the thimble must be placed at the bottom of a common earthen pan1 ,b ,d ,t1 which should be covered over with a piece of glass1 ,v4 ,to graduate the compass a circle is described on a piece of paper4 ,on this dial we trace the divisions sufficiently close only at the north extremity of the needle1 and the paper is fixed underneath1 as in fig4 #bjc4 ,then we fix a piece of wax at the end of the match pointing ,n41 opposite the northern extremity of the needle inside the basin4 ,in this way we have a very useful and inexpensive compass4 ,we may also magnetize a fine sewing-needle1 and grease it by rubbing it with a little suet4 ,it is then capable of floating on the surface of water running in the direction of the north pole4 ,we might go on multiplying indefinitely examples of physical experiments without apparatus1 but we have probably already given a sufficient number to aid our readers in imagining others4 ,we have now in a simple manner shown how we can easily produce electricity4 ,we may understand that electrical phenomena are produced--7#a7 friction between different bodies2 7#b7 by placing bodies which differ in contact2 7#c7 by the transition of bodies from one condition to another2 7#d7 by chemical changes2 7#e7 by animals4 ,the two first1 and the fourth1 are the most usual causes4 ,we know that certain substances when rubbed with silk or wool acquire the property of attracting other substances4 ,but in the case of a rod of glass or stick of wax1 the attraction will only be perceived when the rubbing has been applied4 ,but metal will behave differently4 ,any part of the metal rod will continue to attract4 ,so metals are ,,conductors of electricity2 while glass1 wax1 silk1 amber1 sulphur1 etc41 are bad1 or ,,non-,,conductors4 ,metals are the best conductors we have1 but trees1 plants1 liquids1 and the bodies of animals1 including men1 are all good conductors of electricity4 ,dry air is a bad conductor4 ,illustration3 ,fig4 #bjd4--;,attraction and repulsion4 ,there are two kinds of electricity1 known as positive and negative 7plus or minus71 vitreous or resinous4 ,we saw in fig4 #bjj that we can attract a small ball of pith or cork by a piece of sealing-wax rubbed with flannel4 ,if we then present a glass rod rubbed with silk to it1 it will be equally attracted1 but will be at once repelled2 and after being so repelled1 if we put the wax to it1 it will be attracted to the sealing-wax again4 ,so wax at first attracts then repels the ball1 and so does glass1 but either will attract the ball if presented alternately 7fig4 #bjd74 ,the reason for this is as follows3-- ,when we have rubbed the glass with silk1 we charge it with positive electricity1 and when the rod touches the ball1 the latter imbibes that electricity1 and flies away from the glass rod4 ,the sealing-wax imparts negative electricity in the same way4 ,the law is1 that bodies charged with the same kind of electricity repel each other1 and those containing the opposite kinds attract each other4 ,positive repels positive2 negative repels negative4 ,but positive attracts negative1 and negative attracts positive4 ,opposite electricities unite1 and so neutralize each other that no effect is perceived2 but it must be borne in mind that all bodies possess both electricities in some quantity1 greater or less4 ,by rubbing we separate these electricities1 the rubber becoming negative1 the rubbee positive4 ,the friction of glass supplies positive electricity1 and sealing-wax supplies negative electricity1 or we can obtain the same effect by rubbing either with certain material4 ,the manner in which a body is electrified depends upon its nature and condition2 but we may accept as a general axiom1--but by no means as a law1--that when two bodies are rubbed together1 that which gets the hotter in the process takes the negative kind of electricity4 ,in the following list the substances have been so arranged that each is negatively electrified by those preceding1 and positively by those succeeding it4 #a1 cat's skin2 #b1 glass2 #c1 woollen stuffs2 #d1 feathers2 #e1 wood2 #f1 paper2 #g1 silk2 #h1 shellac2 #i1 rough glass4 ,we append a list of conducting and non-conducting bodies in their order3-- ,,conductors4 ,metals4 ,lime1 coal1 or coke4 ,saline mixtures4 ,pure water4 ,vegetable tissues4 ,animal tissues4 ,hot air4 ,steam4 ,rarefied air4 ,,non-,,conductors4 ,ice4 ,india-rubber4 ,marble4 ,porcelain4 ,resin4 ,dry gases4 ,paper4 ,wool4 ,silk4 ,shell-lac4 ,diamond4 ,glass4 ,wax4 ,sulphur4 ,illustration3 ,fig4 #bje4--,positive and negative4 ,illustration3 ,fig4 #bjf4--,the ,battery4 ,it should be observed that the degree of value as a conductor or non-conductor depends somewhat upon the atmosphere4 ,for instance1 glass is an excellent insulator1 or non-conductor1 when dry1 but when wet it changes to a conductor4 ,so insulators are at times covered with a solution of shell-lac1 or fat1 to keep away moisture4 ,we may reasonably conclude that bodies which are good and bad conductors are good and bad conductors of electricity4 ,water is a good conductor1 air is a bad one2 were it otherwise1 electricity would escape from the ground into the air2 as it is1 the air manages in some degree to retain the electricity at the surface of bodies1 for it is on the surface that we find the electric 8fluid40 ,we have mentioned electrical induction in a former experiment with the tea-tray4 ,we will now explain it more fully1 as a consideration of it will bring us to the electric spark1 or lightning1 with the account of the discovery of the ,conductor and the ,electrical ,machine4 ,let us look at the illustration next below4 ,a ,b is a cylinder supported on a glass rod1 and at each extremity is a small pith ball1 a and b4 ,the cylinder is in a neutral condition1 as is evidenced at first by the pellets being in a vertical position4 ,but suppose we bring a ball1 ,c1 towards the cylinder4 ,c is charged with positive electricity1 which attracts the negative to itself1 and so repels the positive away at the opposite side4 ,so the pellet at one side will be attracted to ,c1 and the other will fly in an opposite direction4 ,illustration3 ,fig4 #bjg4--;,electrical induction4 ,let us take another illustration4 ,here we have a horizontal metal rod1 cc1 insulated on a glass stand4 ,two balls of cork are attached at both ends of the rod by metallic wires4 ,hold a rod of resin1 r1 which has been made negatively electrical1 and apply it to one pair of the cork balls4 ,the positive electricity will be attracted at c and the negative repulsed1 and fly away at c4 ,if we remove the resin the equilibrium will be again established1 and the balls will fall to a vertical position4 ,illustration3 ,fig4 #bjh4--;,induction4 ,we can also by drawing off the negative electricity by the finger at c1 while the resin rod is still held to the other side1 c1 fill the whole of the metal rod with the positive electricity when the finger and the resin have been removed respectively first and last4 ,the balls will then fly in opposite directions again1 in consequence of the repulsion exercised by the positive poles4 ,the 8,electrophore10 or 8,electrophorus10 we have already learned to make for ourselves1 as also the ,leyden ,jar4 ,but we give cuts of them4 ,the former is very simple1 and can be made by mixing two parts of shell-lac and one of turpentine1 and pouring the mixture upon a metal plate4 ,if this be rubbed with a cat's skin when dry1 and a metal cover with a glass handle be placed upon it1 it will be found that the positive and negative electricity are collected on the lower and upper surfaces of the plate respectively1 and can be drawn away with a spark as before1 and made use of4 ,illustration3 ,fig4 #bji4--;,electrophorus4 ,the ,leyden ,jar requires a little more detailed description1 as it is to it we are indebted for our ,battery4 ,it is a common glass bottle or jar1 coated both inside and out with tinfoil nearly as high as the shoulder1 a a4 ,the mouth should be firmly closed with a bung of wood1 g g2 a hole should be bored in the bung1 through which a brass rod is tightly pushed4 ,the rod1 too1 is topped by a brass knob1 and a brass chain is attached to the other extremity4 ,the interior of the tinfoil receives positive electricity1 and the exterior negative when the jar is charged from the 8,electrophorus40 ,to discharge the jar and create a shock it is necessary to put one hand on the outside1 and the other on the knob of the jar4 ,a brilliant spark and a severe shock will result if the jar has been fully charged4 ,it is as well to be cautious when trying this experiment4 ,the effect of the shock may be felt by any number of persons joining hands1 if one at one end of the row1 and one at the other end1 touch the knob and the outside of the jar simultaneously4 ,illustration3 ,fig4 #baj4--,the ,leyden ,jar4 ,this electric discharge is lightning in miniature1 and it is to ,benjamin ,franklin that the world is indebted for the discovery4 ,the philosopher was greatly interested in the science of ,electricity and1 having retired from business1 he devoted himself to the consideration of thunderstorms4 ,he wrote a treatise to show that points drew off electricity1 and that electricity and lightning were similar4 ,he urged that metallic rods might be attached to ships and buildings1 so that during thunderstorms1 or at other times1 the electricity might be harmlessly carried into the ground4 ,this suggestion he made without being able to explain why points did carry off electricity without a spark4 ,the reason is because there is no place to store it2 it runs away at once1 without having time to collect1 as in a ball4 ,franklin made one or two experiments before his renowned kite-flying arrangement1 which convinced him that electricity was by no means an agent to be played with4 ,he endeavoured to kill a turkey by electricity1 but by incautious handling of the jars in which the 8fluid0 was stored1 he discharged them1 and describes the result3 8,the flash was very great1 and the crack was as loud as a pistol2 yet my senses being instantly gone1 ,i neither saw the one nor heard the other1 nor did ,i feel the stroke on my hand1 though ,i afterwards found it raised a round swelling where the fire entered as big as half a pistol bullet40 ,on a subsequent occasion he was again struck senseless while endeavouring to administer a shock to a paralytic patient4 ,it was not until ,june #ageb that ,franklin made the experiment with the kite1 which resulted in such great discoveries4 ,he made his kite of a silk pocket-handkerchief1 and he fixed a pointed rod upon the upright portion of the frame at the top2 the string ended in a foot or so of silk1 which was held by the philosopher1 and to the end of the hempen portion of the string a large key was tied4 ,for some time1 notwithstanding the approach of most unmistakable thunder-clouds1 his patience was tried4 ,but at last the strands of the hempen string began to bristle up1 and soon after1 when ,franklin applied his knuckle to the key1 a spark was obtained4 ,the great discovery was made4 ,franklin subsequently obtained lightning in his own house1 and performed several experiments with it4 ,illustration3 ,fig4 #baa4--,the ,electroscope4 ,the ,electroscope 7fig4 #baa7 is an instrument by which we can ascertain whether electricity is present or not1 and the nature of it4 ,if we bring an object unelectrified close to the ball or knob on the top of the glass shade1 the two needles1 or strips of gold-leaf1 which are often used1 will remain still4 ,but if the body has been electrified it will communicate the electricity to the rod inside1 and attract to itself the fluid of opposite quality2 the same kind of electricity then is in action in the gold-leaf or needles1 and they fly apart--repel each other4 ,supposing that positive electricity were first communicated1 we can cause the contraction of the leaves or wires by applying a negative kind1 which1 meeting the positive1 neutralizes it1 and the wires collapse4 ,if the electricity with which the instrument is charged be positive1 by approaching the baton to the ball1 ,a1 we shall see the wires diverge more than before1 and they will finally be discharged by the knobs within4 ,if the electricity be contrary to that in the baton1 the wires will approach each other1 but by gradually withdrawing the baton they will again separate1 and even to a greater distance than before4 ,the ,electric ,machine is shown in the illustration 7fig4 #bab74 ,it consists of a large plate of glass fixed upon a glass stand1 between wooden supports4 ,the handle is of glass2 two pairs of rubbers are fastened above and below2 the plate is turned between them1 and becomes 8positively0 electrified4 ,the rubbers are covered with leather and stuffed with horsehair1 ,,dd1 and press very tightly against the glass1 so that the friction is constant4 ,the rubbers are covered with an amalgam made of mercury1 zinc1 and tin1 two parts of the first to one each of the others4 ,a chain 7of metal7 connects the machine with the ground4 ,the conductors1 ,,pp1 are united by a cross-piece1 ,q1 and sustained upon glass supports4 ,at the end of the conductors are two curved rods1 ,,cc1 which are provided with points to take the electricity from the plate1 but do not touch it4 ,illustration3 ,fig4 #bab4--,the ,electric ,machine4 ,the electricity is thus stored in the insulated conductors as the machine is turned4 ,the negative portion is carried into the ground by the chain from the rubbers1 while the positive electricity is retained4 ,the longer we turn the more we shall obtain1 and the quantity is measured by an electric pendulum on one of the conductors1 which flies out by degrees as the charge increases1 and indicates its power by means of a needle it works upon an ivory index4 ,it is not difficult to make an electric machine out of a glass bottle4 ,this will furnish the glass cylinder4 ,if a stick be run through it 7for which purpose a hole must be drilled in the bottom of the bottle71 a handle can be fixed1 and the bottle mounted on a stand4 ,a wash-leather cushion1 stuffed1 can be so arranged that it will press against the bottle as it is turned2 a piece of silk should be permitted to hang from the cushion frame over the glass4 ,a conductor may be made from a piece of wood neatly rounded and smoothed1 and coated with tinfoil4 ,the ends should be rounded like 8knobs40 ,stick pins in to collect the electricity 7and it will be readily obtained74 ,the cushion should of course be well smeared with amalgam4 ,from this1 as well as from the glass-plate machine1 the 8positive0 electricity can be drawn off and stored in a ,leyden jar1 and then discharged by the 8discharging rod10 which is represented on the cut4 ,it may have one or two handles1 and one knob is placed outside the jar1 the other near the ball surmounting it4 ,the glass being a non-conductor saves the operator1 and some long sparks and loud reports may be obtained4 ,illustration3 ,fig4 #bac4--;,cylinder machine4 ,the ,electric ,machine is always assumed to give off positive electricity4 ,sir ,william ,armstrong's ,electric ,machine is a mode of obtaining electricity by moist steam4 ,the design is ,armstrong's1 and ,professor ,faraday subsequently went into all the conditions to produce the 8fluid0 by the friction of steam4 ,the machine was something like a small boiler supported on glass legs4 ,a row of nozzles was fixed upon the escape pipe so as to create a great velocity and friction in the escaping steam4 ,round the nozzles was a box of cold water1 for that fluid was found necessary for the production of electricity as demonstrated by ,professor ,faraday4 ,the steam rushed against a row of points attached to the prime conductor of an electric machine1 and the electricity of the steam was thus given off to the conductor4 ,there are many other forms of electric machines1 but it will serve no purpose to detail them4 ,illustration3 ,fig4 #bad4--;,discharging rod4 ,the ,electric ,battery 7see fig4 #bjf7 is formed by a collection of ,leyden jars4 ,the inside and outside coatings are connected in a box divided into partitions lined with tinfoil4 ,the rods of the jars are also connected1 as in the illustration1 by brass rods1 and when this battery is charged people should be careful how they handle it1 for a shock may be produced which would cause serious injury1 if not death4 ,the battery can be charged from the machine by a chain fastened to the central ball1 while a second chain connects the exterior of the box and all the outside of the jars1 by means of the handle1 to the ground4 ,when electricity is at rest it is termed 8static electricity10 and when in motion 8dynamic0 electricity4 ,the latter treats of electric currents which can be sent through wires or chains4 ,we can keep this current moving by means of a machine1 and the battery called a ,voltaic battery1 from ,volta4 ,we will describe it presently4 ,electric currents can be measured1 for they may be of different strengths according to the battery1 and they are measured by the ,,galvanometer4 ,electricity can therefore be transferred and carried by the conducting substances1 and much heat will be engendered as the 8electric fluid0 passes along a wire4 ,lightning frequently fuses bell-wires as it passes1 and when we touch upon ,galvanism or ,dynamical ,electricity we shall hear more about it4 ,by the ,electric ,machine we can obtain some very powerful currents of electricity2 we can produce many pleasing effects1 and perform a number of experiments1 such as making balls or figures of pith dance1 and several other easy and entertaining tricks1 which will be found in books more specially devoted to the entertainment of young people4 ,illustration3 ,fig4 #bae4--,leyden ,jar4 ,we have now given some explanation of the manner in which electrical phenomena can be produced1--viz41 by the ,electric ,machine and by the ,leyden ,jar1--but we must not expect to find any electricity inside any charged body4 ,it has been proved that all the electricity is upon the surface of bodies1 even if in varying quantity1 and that equal quantities of electricity are always produced when bodies are excited by friction1 but the kinds are different4 ,the rubbing body is of one kind1 the body rubbed another1 and consequently the forces neutralize each other4 ,the two forces or kinds of electricity we have seen repel or attract each other1 and we can imagine the farther they are apart the less will be the force1 and the rate of diminution of force1 according to distance1 is ascertained by an ingenious apparatus called a 8,torsion0 ,electromoter1 which was constructed by ,coulomb1 and was frequently used by ,faraday4 ,perhaps some people may not be aware of the term 8torsion40 ,it means twisting1 and 8the torsion of a thread suspended vertically is the force tending to twist the lower extremity when the upper end is turned through an angle40 ,this instrument is really an ,electromoter1 and is not considered suited to beginners1 and it is scarcely accurate in its workings4 ,we need not therefore describe it in detail4 ,there are some excellent ,electromoters1 the ,elliott being1 we believe1 the best for use4 ,a full and detailed description of the ,quadrant ,electromoter will be found in ,mr4 ,gordon's treatise on ,electricity4 ,recapitulation of foregoing ,chapter4 ,so far1 we have seen there is electricity in everything1 although some bodies are termed conductors and others non-conductors2 though1 as in applying the terms heat and cold1 we must remember that no body is entirely devoid of electricity1 and no body is therefore an absolute non-conductor any more than any object is absolutely devoid of heat4 ,faraday1 indeed1 was of opinion that 8conduction and insulation are only extreme degrees of one common condition02 they are identical both in principle and action1 except that in conduction an effect common to both is raised to the highest degree1 and in the case of insulation it occurs in an almost insensible quantity4 ,we have also read of positive and negative electricities1 and we must not fancy there is any particular reason for this distinction4 ,it was ,du ,fay1 whom we have mentioned1 who gave the names 8vitreous0 and 8resinous0 to the two kinds1 as one was developed by rubbing glass1 and the other by rubbing resin4 ,but1 as shown by our experiments1 either kind of electricity can be excited in glass or sealing-wax1 and both kinds are produced at once4 ,you cannot get 8positive0 without negative electricity4 8,positive0 is the term applied to the kind produced by rubbing glass with silk or wool2 8negative0 is the term applied to the kind developed by rubbing sealing-wax1 but the kind developed by friction depends on the rubbing substance and certain conditions4 ,bodies charged with the same electricity repel2 if charged with different kinds they attract each other4 ,the more readily displaced particles when bodies are rubbed become negatively electrified as a rule4 ,similar electricities repel each other with a force inversely proportional to the squares of the distance between their centres1 as established by ,coulomb4 ,so if the space between any two similarly electrified bodies be reduced by say one-half1 the force of the repulsion will be increased four times4 ,the rule for attraction is similar2 so when two bodies are charged with opposite electricities1 and the distance between them is increased1 the attractive force is diminished in proportion as the square of the distance between them4 ,many confirmations of this theory were made by the late friend of our boyhood1 ,sir ,w4 ,snow ,harris1 and published in the ,philosophical ,transactions4 ,the following full list of conductors and non-conductors 7copied from ,professor ,noad's ,text-book of ,electricity1 and compared with ,de ,la ,rive's ,treatise7 may be useful3-- ,,conducting ,,bodies ,,in ,,order ,,of ,,conducting ,,power4 ,all the metals4 ,well-burnt charcoal4 ,plumbago4 ,concentrated acids4 ,powdered charcoal4 ,dilute acids4 ,saline solutions4 ,,insulators ,,in ,,the ,,inverse ,,order ,,of ,,insulating ,,power4 ,dry metallic oxides4 ,oils 7heavier the better74 ,vegetable ashes4 ,transparent dry crystals4 ,ice below #ac ,fahr4 ,phosphorus4 ,lime4 ,,conducting ,,bodies ,,in ,,order ,,of ,,conducting ,,power4 ,metallic ores4 ,animal fluids4 ,sea-water4 ,spring-water4 ,rain-water4 ,ice above #ac ,fahr4 ,snow4 ,living vegetables4 ,living animals4 ,flame smoke4 ,steam4 ,salts soluble in water4 ,rarefied air4 ,vapour of alcohol4 ,vapour of ether4 ,moist earth and stones4 ,powdered glass4 ,flowers of sulphur4 ,,insulators ,,in ,,the ,,inverse ,,order ,,of ,,insulating ,,power4 ,dry chalk4 ,native carbonate of baryta4 ,lycopodium4 ,caoutchouc4 ,camphor4 ,silicious and argillaceous stones4 ,dry marble4 ,porcelain4 ,dry vegetables4 ,baked wood4 ,leather4 ,parchment4 ,dry paper4 ,hair4 ,wool4 ,dyed silk4 ,bleached silk4 ,raw silk4 ,the following may be added to the ,insulators1 viz43-- ,transparent precious stones4 ,diamond4 ,mica4 ,all vitrefactions4 ,glass4 ,jet4 ,wax4 ,sulphur4 ,resins4 ,amber4 ,gutta-percha4 ,shell-lac 7or gum-lac74 ,ebonite4 ,there are1 as we know1 two kinds of electricity1 the static and dynamic2 and when the latter state is instantaneous1 it is referred to as the 8electric discharge10 which occurs when opposite electricities seek each other1 and the bodies return to a state of equilibrium or neutralization4 8,these bodies1 if insulated1 obtain no more electricity after the spark has passed2 but if there be a constant source of negative electricity supplying one1 and a constant source of negative electricity supplying the other1 there will be a succession of sparks2 and if they communicate by a conductor there will be1 through this conductor1 an uninterrupted neutralization of a continual reunion of the two electricities1 and this is what is termed the continuous dynamic state or electric current0 7,de la ,rive74 ,,footnotes3 #ac ,this interesting experiment1 which we have exactly verified1 was described to us by ,professor ,waldner1 and ,m4 ,a4 ,keppler4 ,,chapter ,,xix4 ,,velocity ,,of ,,electricity--,,experiments--,,the ,,electric ,,egg--,,force ,,of ,,the ,,electric ,,spark4 ,we are now acquainted with many facts concerning electricity1 and have seen that electrical phenomena can be produced by the ,electric ,machine and the ,leyden ,jar4 7,an insulating stool--a stool with glass legs--is a very desirable adjunct for those who wish to experiment with the machine74 ,glass is a great insulator1 or non-conductor1 as a ,russian philosopher found to his cost4 ,he had an iron lightning-conductor from his house into his room1 the end not connected with the earth but with a glass4 ,one day the lightning came down the rod and reached the glass2 had a communication been made with the earth by a chain1 or directly1 no mischief would have ensued4 ,as it happened1 however1 the current was checked by the glass1 and immediately darted towards him2 it struck him in the head1 and killed the poor man on the spot4 ,if no insulating stool were used1 the body charged would be discharged upon contact with the ground4 ,the velocity of electricity is very great1 and experiments have frequently been made4 ,wheatstone undertook to ascertain the speed of the electric fluid1 and the instrument he employed he called a 8,chronoscope40 ,he caused a mirror to revolve with enormous velocity1 and measured the speed by the vibrations of air1 which produced a certain note by the same motive power4 7,we know already that certain notes are produced by a certain number of vibrations per second47 ,wheatstone's ,chronoscope consisted of this mirror1 in front of which was placed a circular block of wood1 in which1 in a row1 were set six wires carrying small knobs2 round these and over the wood he put an insulating varnish4 ,a ,leyden jar was connected outside with the first knob2 between the second and third a quarter of a mile of copper wire was coiled1 and a like length of wire between the fourth and fifth2 the inside of the ,leyden jar was then connected with the last knob1 and the spark passed2 it ran from knob to knob over the long coils of wire4 ,if all the flashes over the wire and knobs occurred simultaneously the mirror would show them side by side2 if not1 as the mirror turned a trifle1 the difference would be observed4 ,the mirror did show a slight retardation in the passage of the flash1 and from certain measurements and calculations ,wheatstone estimated the velocity of the spark to be #bhh1jjj miles a second4 ,this rate will carry electricity round the earth in about a twelfth of a second1 a rate ,puck never dreamed of when he promised to 8put a girdle round the earth in forty minutes40 ,but it appeared from investigations subsequently made that it was not possible to express the velocity of electricity with any certainty1 and a number of experiments were made as per the following table1 with very different results4 ,sir ,william ,thomson and ,faraday endeavoured to account for these stupendous discrepancies1 and the principles of retardation of electricity were established4 ,the differences are shown below3-- ,nature of ,velocity per ,wire4 ,second4 ,wheatstone's ,experiment in #ahcd ,copper #bhh1jjj ,gonella and ,fizeau ,copper #aaa1hcd ,iron #fb1acj ,mitchell ,iron #bh1cca ,walker ,iron #ah1fci ,gould ,iron #ae1hcj ,astronomers in ,greenwich ,copper #g1fjj 8 ,brussels ,copper #b1gjj ,result in ,atlantic ,cable1 #aheg ,copper #a1dcj 8 8 #aheh ,copper #c1jjj ,to account for the comparatively low velocities of the cables1 ,faraday proved that they act very much as a ,leyden jar acts2 that is1 it takes time to fill1 as it were1 and to discharge them1 the wire coating of the cable in air acting like the outer coating of the jar or the water in the case of an immersed cable1 and the retardation observed is owing to resistance of conduction1 and depends upon the way in which the electrical impulses traverse the wire4 8,there is a long1 gradual swell1 and still more gradual subsidence of the electric current1 and the length of time that elapses between the initial impulse and the attainment of maximum strength1 is proportional to the square of the length of the line40 ,the duration of the electric spark has been calculated at the #a_/bdjjj part of a second1 but ,professor ,tyndall regards this as the longest or nearly the longest time it is perceptible2 the shortest time is almost inconceivable4 ,the brightest portion of a spark has been ascertained to last only forty-six millionths of a second1 and certain experiments were made to ascertain the actual duration with various numbers of ,leyden jars4 ,it was discovered by ,messrs4 ,lucas and ,cuzin1 by an application of the ,vernier1 with batteries consisting variously of two to eight jars1 and obtained the following results#ad-- ,duration in ,no4 of ,jars4 millionths of a ,second4 #b #bf #d #da #f #de #h #dg 8,so10 adds the writer1 8the duration 7of spark7 increases in proportion with the number of the jars4 ,it increases also with the striking distance1 but is independent of the diameter of the balls or globes between which the spark strikes40 ,many examples might be given of the spark discharge of the electric current4 ,this form is seen in the blue line extending between the knob of a machine and the hand1 and the duration of a spark with a jar charged with an induction coil is stated by ,professor ,rood to vary1 but the brightest portion with a jar of #aad square inches only existed for the #ageth billionth of a second1 and with a smaller surface was much shorter4 ,such a spark may be conducted to a plate of gunpowder and will not ignite it1 because the time of the duration of the 8fire0 is not sufficiently long2 the powder will be scattered1 but not ignited4 ,if1 however1 a partly non-conducting medium be interposed between the jar and the powder1 so that the spark be retarded a little1 the gunpowder will be fired4 ,while speaking of electric discharge we may remark upon the beautiful effect of lightning4 ,these discharges are sometimes miles long1 and by the return stroke from the cloud may kill a person a long way from the actual discharge4 ,this phenomenon was illustrated by ,viscount ,mahon in #aggi1 in a very interesting book on the principles of electricity4 ,there are different ways in which the electric discharge shows itself4 ,we have spoken about the spark discharge which1 however1 is found to present very different appearances in varying conditions4 ,professor ,faraday proved that the colour of the electric sparks showed in air1 when obtained with brass balls1 the intense light and blue colour so familiar to all4 ,in nitrogen they are even bluer4 ,in oxygen again the sparks are much brighter than in air1 but not so brilliant4 ,in hydrogen they become crimson1 but the sound is almost inaudible because of the physical character of the gas4 ,in carbonic acid gas they are almost the same as in atmospheric air1 only more irregular4 ,in dry muriatic gas they are nearly white and very bright4 ,in coal gas the colours vary--sometimes being green and sometimes red4 ,occasionally the same spark will be red and green at different extremities1 and even black portions have been observed4 ,the density and pressure of the atmosphere has been proved to exercise considerable influence upon the spark discharge4 ,the 8,brush0 discharge is shown in 8a series of intermittent discharges which appear continuous40 ,this discharge assumes the shape of a fan4 8,it is accompanied with a low chattering sound10 which is the result of the separate and continuous discharges1 and ,faraday also demonstrated that its effects varied according to the medium in which it was exhibited4 ,the effect of the air pressure on electricity may be observed in the following way3-- ,if we pass a spark through rarefied air by an apparatus known as the ,electric ,egg1 we may obtain many curious effects4 ,the 8egg0 consists of a glass globe1 through which enter two rods with a knob upon each inside end4 ,the upper rod is moveable1 and held in its place by a 8cap0 like the lower rod4 ,there is a stop-cock in the lower cap1 so that the egg may be fastened to any plate or stand4 ,when the egg is filled with air1 the electric spark passed into the glass globe has the usual appearance1 but as the air is gradually rarefied by an air-pump1 the spark assumes beautiful forms and colours4 ,as the exhaustion continues1 however1 we shall find the spark decreasing in brilliancy1 and finally the spark will cease to be visible4 ,it thus is shown that the colour of the spark depends upon the gaseous medium and on the material of the conductors1 and when the electric spark is faint this medium can be observed1 for nitrogen will produce a blue tinge and carbonic acid a green2 hydrogen gives us a red1 as already remarked4 ,by multiplying the number of eggs and plates of glass1 and placing discs of tinfoil in various shapes at certain distances1 many beautiful figures may be observed when the spark is set free4 ,professor ,tyndall at the ,royal ,institution showed a very pretty experiment4 ,he took a funnel with a very fine bore1 and permitted sand to flow from it as it will in the hour-glass4 ,when he permitted the electric current to come in contact with the sand1 however1 it1 instead of falling vertically to the table1 spread out fan-like1 each grain repelling and being repelled by its neighbour with an effect very beautiful to see4 ,luminous effects have frequently been produced by passing an electric spark through various bodies4 ,for instance1 a lump of sugar can be made quite brilliant in the dark by passing electricity through it1 and there are other substances similarly affected4 ,even eggs and some fruits are thus made phosphorescent4 ,the illumination of the 8diamond0 covered ,leyden jar is familiar to all who ever attended a lecture on ,electricity4 ,the various effects of the electric discharge need not here be described4 ,we have witnessed the results of lightning1 but even in our laboratory many pretty little experiments can be made1 such as the perforation of a card by the electric discharge4 ,the chemical effects are various4 ,decomposition of water is effected by electricity1 and the discharge can also be1 and has been utilized for military purposes1 such as employed by ,professor ,abel in his fuse1 and in his apparatus for firing mines4 ,experiments at ,chatham and elsewhere have been very successful in the application of electricity to modern warfare4 ,we will illustrate one or two of these4 ,a thick card should be placed1 as in the illustration 7fig4 #baf71 between two insulated points1 and to the lower portion of the apparatus a chain be attached1 held in the hand1 and wound round the ,leyden jar4 ,if then the knob of the jar and the knob above the upper point be brought together1 the spark will pass through the card4 ,illustration3 ,fig4 #baf4--;,experiment with card4 ,in the same manner a glass may be perforated if the current be stronger4 ,of course the whole apparatus--and particularly the plate--must be quite dry1 and it will be better to put a drop of oil under the upper needle point so as to prevent the electricity spreading over the glass4 ,the glass will be found pierced by the electric spark when the ,leyden jar is brought into requisition 7fig4 #bag74 ,it was at one time contended that the sudden expansion of the air by the electric spark caused heat to be generated1 and a thermometer was invented by ,kinnersley to show this4 ,the illustration 7fig4 #bah7 will explain it4 ,when the electric spark passed between the balls in the large tube the water rose in the smaller4 ,but the immediate return of the water to its level showed that the disturbance was only mechanical1 and not owing to heat4 ,illustration3 ,fig4 #bag4--;,experiment with glass4 ,illustration3 ,fig4 #bah4--,kinnersley's thermometer4 ,we may now pass from the 8frictional0 to the other kind--viz41 8dynamical0 electricity1 and we shall begin with the consideration of ,,galvani',s experiments and the ,,voltaic ,,pile4 ,illustration3 ,electric condenser4 ,,footnotes3 #ad ,,ganot3 ,elments de ,physique4 ,,chapter ,,xx4 ,,galvanism4 ,,galvani',s ,,discovery--,,the ,,frogs ,,electrified--,,experiments--,,volta',s ,,pile--,,the ,,test--,,its ,,usefulness--,,faraday',s 8,,researches40 ,galvanism owes its origin to the researches of ,galvani1 the celebrated professor of ,bologna1 and we are indebted to what was a mere 8accident0 for our knowledge of this science4 ,before ,galvani's time there had been many instances adduced of animal electricity4 ,the ,rev4 ,f4 ,lunn1 in his article upon ,electricity1#ae mentions the fact that fire streamed from the head of ,servius ,tullius when about seven years of age1 and ,virgil we know refers to flame emitted by the hair of ,ascanius-- 8,lambere flamma comas1 et circum tempora pasci02 and if any one will comb his or her hair with an ebonite comb in the dark1 with what is sometimes called an 8india-rubber comb10 the hair will give out sufficient light to enable the operator to see himself in a looking-glass4 ,in olden days it is related that a lady when touched with a linen cloth emitted sparks1 and the same phenomenon was observable when a bookseller at ,pisa removed his under-garment or vest 7,de ,castro74 ,we are all aware of the electricity of the cat and of certain fishes 7see ,electricity of ,animals in sequel71 and 8torpedos40 ,galvani had of course a knowledge of this property1 and had occupied himself for some time making experiments upon the electricity in animals4 ,he was not in his laboratory that day when the great discovery was made by means of the edible frog4 ,galvani's wife was just then in a very delicate state of health1 and in accordance with usage had been ordered soup made from frogs4 ,it is related that some of these animals1 ready skinned1 were lying upon the laboratory table1 for the ,professor had been just previously investigating the question of what he opined was 8animal0 electricity2 that is1 he fancied that muscular motion depended upon that subtle force4 ,the electric machine was in action1 and one of the attendants happening to approach or touch one of the frogs1 the man as well as ,madame ,galvani observed that the limbs were violently agitated4 ,galvani was at once informed of this1 and he made repeated experiments1 which showed him that the convulsive movements only took place when a spark was drawn from the prime conductor of the electric machine1 and while the nerve was touched by a conductor4 ,galvani then suspended a number of frogs to a railing by metal hooks1 with a view to experiment upon them with atmospherical electricity4 ,but the frogs' limbs were again agitated when no electricity was apparent1 and ,galvani after some consideration came to the conclusion that the movement was owing to the position the animals assumed with reference to the metallic bodies4 ,thus when muscle and nerve were in contact with metallic bodies and connected by metal1 the movements of the limbs were observable1 and the greater the surface contact the greater was the convulsion4 ,the philosopher next tried various metals1 and discovered that the most powerful combination was zinc and silver4 ,galvani1 in #agia1 published his discovery and his theory that the body acted as a ,leyden jar1 different parts being in a different state of electricity4 ,no sooner were his deductions published than all ,europe was in a ferment1 and philosophers of all nations were discussing it4 ,fowler1 ,valli1 ,robison1 ,wells1 ,humboldt1 etc41 all were deeply interested1 but none of them appear to have arrived at so correct conclusions as did ,volta1 the physician of ,pavia4 8,wherever frogs were to be found10 says ,du ,bois ,reymond1 8and where two different kinds of metal could be procured1 everybody was anxious to see the mangled limbs of frogs brought to life in this wonderful way4 ,physiologists believed that at length they should realize their visions of a vital power1 and physicians thought no cure was impossible40 ,but notwithstanding the popular theory1 ,volta1 in his letters to ,carallo1 while giving a full and clear account of the discovery made by ,galvani and his own experiments1 attacked and finally defeated the ,professor4 ,volta quite upset ,galvani's ,leyden-jar theory2 ,volta says that it was by accident that ,mr4 ,galvani discovered the phenomenon1 and by which he was more astonished than he ought to have been4 ,volta's letters will be found in the ,philosophical ,transactions of the ,royal ,society 7in ,french71 and he attributes the effect to the metals which produced a small amount of electricity4 ,he found that the nerve was acted upon on even parts of a muscle laid upon two different metals1 and if those were united1 a contraction took place4 8,many experiments were made in all parts of ,europe10 says ,doctor ,roget1 and 8an opinion had been very prevalent that the real source of the power developed existed in the muscle and nerve which formed part of the circuit1 and that the metals which composed the other part acted merely as the conductors by which that agency was transferred from the one to the other of these animal structures4 ,but the discoveries of ,volta dispelled the error1 by proving that the sources of power were derived from the galvanic properties of the metals themselves when combined with certain fluids10 and decided that this principle was electricity4 ,from this the 8general fact0 was deduced--viz41 8that when a certain portion of a nerve which is distributed to any muscle is made part of a galvanic circuit1 convulsions1 generally of a violent and convulsive kind1 are produced in that muscle40 ,volta at length made the discovery that when two metals were brought together electricity was developed1 and by uniting a disc of copper and one of zinc1 and subjecting them to the test of an ,electroscope1 he found positive and negative electricity developed in the zinc and copper respectively2 so ,volta came to the conclusion that each metal parted with electricity1 and one became all 8positive0 and the other all 8negative40 ,but when he came further to consider the possibility of building up a 8pile0 of these metal discs sufficiently strong to produce electric effects1 he found that if his theory were correct he would lose from one side of the metal all he would gain from the other1 and therefore he could never obtain more than the slight effect he had originally produced4 ,this was at first a difficulty apparently impossible to remove4 ,it was so self-evident that the discs of metal1 if placed in a pile in a series of pairs1 would continually exercise like effects to the first pair of discs1 that ,volta was puzzled1 and for some time he could not arrive at any reasonable solution4 ,at last it struck him that if he placed between the discs some slow-conducting substance1 the electricity would not pass from disc to disc1 and the force developed or set in motion would be more powerful4 ,he made the experiment4 ,the result was the ,voltaic pile made in #ahjj1 of which we give an illustration 7fig4 #bai74 ,a communication on the subject of ,electricity by contact1 written by ,m4 ,volta1 is to be found in the ,philosophical ,proceedings for the year #ahjj4 ,volta constructed the pile which bears his name1 on the assumption that 8every two heterogeneous bodies form a galvanic circle or arc in which electricity is generated40 ,the 8pile0 consisted of a number of discs of zinc and copper separated by discs of card soaked in water4 ,this combination of metals separated by a bad conductor1 developed considerable electricity1 the 8positive0 going to the zinc at the top1 and the 8negative0 turning to the opposite end4 ,by touching the zinc and copper extremities simultaneously with wetted fingers we shall experience a shock4 8,i don't need your frog10 ,volta said1 when he had proved his theory2 8give me two metals and a moist rag1 and ,i will produce your animal electricity4 ,your frog is nothing but a moist conductor1 and in this respect it is inferior to my wet rag60 ,illustration3 ,fig4 #bai4--,voltaic ,pile4 ,after this discovery the theory of animal electricity died away for many years1 till in #ahbe1 ,nobili1 and afterwards ,matteucci1 proved the existence of galvanic currents in muscles4 ,after ,volta had succeeded in obtaining a shock from his 8pile10 he proceeded to the construction of another instrument1 or rather apparatus1 which he denominated 8,couronne des tasses0 7fig4 #bbj74 ,it consisted of a series of small glasses containing water or a saline solution4 ,he then procured a number of 8metallic arcs10 partly composed of zinc and partly of copper2 these were inserted into the glasses1 so that every glass contained the zinc of one and the copper of another arc1 not in contact1 but one at the right hand the other at the left4 ,the electro motion1 supposed to be the primary cause of the galvanic action1 was thus produced as well as from the 8pile40 ,the principle was just the same in both apparatus1 the metals being divided by the water in one case1 and by a wet card or cloth in the other4 ,volta1 in #ahjj1 addressed to the ,royal ,society his celebrated letter upon electricity excited by contact of conducting substances1 and then the ,english philosophers proceeded to make further experiments4 ,it was ,fabroni of ,florence who had just before suggested that chemical action was really the cause of the phenomena exhibited4 ,sir ,humphrey ,davy warmly advocated this theory1 and made numerous experiments with the view to establish it4 ,nicholson1 ,carlisle1 and ,cruickshank also paid great attention to the subject4 ,volta1 although he had laid the foundation1 did not venture to build upon it4 ,messrs4 ,nicholson and ,carlisle found the two kinds of electricity in the pile1 the zinc being positive and the silver negative4 ,they also found that the water was decomposed both in the circuit and in the body of the pile4 ,subsequently ,cruickshank confirmed ,nicholson's observations1 and made use of what is termed the 8trough0 apparatus4 ,he found that hydrogen was emitted from the silver or upper end1 and oxygen from the other4 ,illustration3 ,fig4 #bbj4--,volta's couronne des tasses4 ,these discoveries opened up a wide field4 8,the power of the pile in decomposing chemical substances was now established40 ,dr4 ,henry employed galvanism for analysis1 and ,sir ,humphrey ,davy invented new combinations of substances4 ,he formed a pile of charcoal and zinc1 and found out that a pile could consist of only one metal1 different fluids being applied to the opposite surfaces separated by water1 and one fluid 8capable of oxidating the metal1 the other of preventing the effect of oxidation40 ,soon after a pile was made of charcoal4 ,in #ahjf1 ,sir ,h4 ,davy gave the results of his researches to the world upon the electro-chemical action of bodies4 ,in the course of his experiments he found out the chemical constituents of the alkalies1 and a surprising number of new things were brought to light1 and chemical science received a most astonishing ally4 ,sir ,w4 ,s4 ,harris says3 8,a series of new substances were speedily discovered1 the existence of which had never before been imagined4 ,oxygen1 chlorine1 and acids were all dragged1 as it were1 to the positive pole1 while metals1 inflammable bodies1 alkalies1 and earths became determined to the negative pole of the 7galvanic7 battery4 ,when wires connected with each extremity of the new battery were tipped with prepared and well-pointed charcoal1 and the points brought near each other1 then a most intense and pure evolution of light followed1 which on separating the points extended to a gorgeous arc40 ,so the elements of all bodies were separated and the composition of their compounds closely investigated4 ,michael ,faraday threw himself con amore into the question4 ,he set about to classify the pile phenomena1 and arranged them with appropriate terms1 and in a series of papers1 between the years #ahcj and #ahdj 7see his 8,experimental ,researches071 he explained the chemical effects of voltaic electricity and electro-magnetic induction4 ,he showed that the electricities obtainable from the voltaic pile and the electrical machine are essentially the same in their action4 ,he proved that the theory held respecting the necessity for the presence of water in electro-chemical composition was erroneous1 and that many other fluids and compounds were equally effective4 ,we have not space at our disposal to include a digest of his various lectures and papers4 ,he calculated that as much electricity is employed in holding the gases oxygen and hydrogen together in a grain of water1 8as is present in a discharge of lightning40 ,when water is decomposed by the electric current1 the force which determines the oxygen and acid matter held in solution to the positive1 while the hydrogen passes to the negative pole1 is not in the poles1 but in the body decomposed1 he says4 8,the poles10 writes ,faraday1 8are merely the surfaces or doors by which the electricity enters into or passes out of the decomposing substance4 ,they limit the extent of that substance in the course of the electric current1 being its termination in that direction4 ,hence the elements evolved passed so far and no farther40 ,faraday named the poles 8electrodes0--the way 7in or out7 of electricity4 ,a very simple voltaic pile may be constructed with 8gold-leaf0 paper4 ,take two sheets of the gold paper and paste them back to back1 and two of silver paper2 cut them into discs about the size of a five-shilling-piece 7or even of half-a-crown71 and place them one on the top of the other1 so as the gold and silver may be alternate2 press the discs together slightly when a good many layers have been piled up1 and introduce them into a glass tube2 close the ends of the tubes with corks through which wires are passed from the discs top and bottom4 ,it will be found that the ends are charged with opposite electricities4 ,this is the ,zamboni pile1 or the dry pile1 which was constructed of hundreds of paper discs 8tinned on one side1 and covered with binoxide of manganese on the other10 put into a tube1 and closed with brass stoppers4 ,the electricity will last a long time in a dry pile4 ,illustration3 ,fig4 #bba4--,the ,galvanic ,pile4 ,in the accompanying illustration of the ,galvanic ,pile a disc of copper is at the bottom and a disc of zinc at the top4 ,the latter1 ,p1 is the positive pole2 the former1 ,n1 the negative4 ,when the wires are united the current is closed1 and no sign of disturbance can be detected1 although the action1 of course1 is proceeding within the pile4 ,the opposite kinds of electricity neutralize each other1 and if a continuous supply were not kept up the electricity would disappear2 but as it is1 a powerful current is obtained1 and if the wire be divided a spark will be observed4 ,illustration3 ,fig4 #bbb4--;,bunsen ,battery4 ,there are many forms of galvanic batteries4 ,the ,trough ,battery or ,cruickshank has been mentioned4 ,there is ,wollaston's ,pile1 ,bunsen's ,battery1 ,grove's ,battery1 and ,daniell's1 called the 8,constant0 ,battery4 ,in this last a porous earthenware cell is placed within a cylinder of copper2 in the cell a rod of zinc is inserted1 the cell being filled with diluted sulphuric acid1--one part of acid to ten parts of water1--and in the outer cylinder is a solution of sulphate of copper4 ,illustration3 ,fig4 #bbc4--;,daniell's ,battery4 ,illustration3 ,fig4 #bbd4--;,grove's ,battery4 ,the cut above illustrates ,daniell's ,battery 7fig4 #bbc7 with connectors4 ,in ,bunsen's ,battery 7or the ,zinc-,carbon ,battery71 which is very like the 8,daniell0 arrangement1 as will be seen from the plates 7figs4 #bbb1 #bbc71 the porous cell has a prism of carbon immersed in it1 and is apparently a modification of the powerful 8,grove0 ,battery 7fig4 #bbd74 ,this consists of slips of platinum1 h1 placed in porous cells1 g1 each cell being surrounded by a glass cylinder4 ,the outer 7glass7 cells are filled1 or nearly filled1 with diluted sulphuric acid2 nitric acid is used in the porous cells1 and a platinum plate inserted4 ,the chemical action of the ,grove cell is thus explained by ,professor ,stewart3 8,the zinc dissolves in the dilute sulphuric acid1 and during this process hydrogen gas is given off4 ,but this hydrogen does not rise up in the shape of bubbles2 it finds its way into the porous vessel which contains the strong nitric acid4 ,it there decomposes the acid1 taking some oxygen to itself1 so as to become water 7hydrogen and oxygen forming water71 and thereby turning the nitric into nitrous acid1 which shows its presence by strong orange-coloured fumes40 ,by this decomposition of the nitric acid the polarization of the platinum 7due to hydrogen7 is avoided4 ,the porous cell1 while keeping the liquids apart1 does not interfere with the chemical action4 ,a great number of cells are used in the ,grove ,battery2 perhaps even a hundred may be employed4 ,smee's ,battery consists of a plate of platinized silver1 ,s1 with a bar of wood to prevent contact with the zinc on each side1 ,z4 ,these are immersed in a glass jar1 ,a1 which contains dilute sulphuric acid4 ,the current is obtained by metallic communication with the binding-screws on the top4 ,this battery has much the same general arrangement as ,wollaston's--the position of the plates being1 however1 reversed2 in the latter there are two negative plates to one positive4 ,in ,smee's ,battery there are two positive 7zinc7 plates to one negative plate4 ,illustration3 ,fig4 #bbe4--,smee's ,cell4 ,illustration3 ,fig4 #bbf4--,smee's ,battery4 ,it will now be understood how an electric current is produced2 the electricity passing through the cells1 etc41 to wires1 confers certain properties upon the wires1 and we can ascertain the effect of the current by means of a ,galvanometer1 an instrument used to detect the strength and direction of electric currents4 ,the current will evolve heat and light2 it will excite muscular action1 and will decompose substances into their constituent elements4 ,the deflection of the magnetic needle by the electric current is considered the best evidence of its power2 it is on this that the ,galvanometer is based4 ,we can perform a few simple experiments with the current4 ,suppose1 for instance1 that a piece of fine wire be fixed between the pole wires of the battery2 it will be heated 8white hot40 ,or if two carbon points be approached in a glass of water1 as in the illustration 7fig4 #bbg71 they will emit a brilliant light in the fluid from the voltaic arc which has given us the electric light4 ,the current is the passage of electricity along the wire1 and continues until the working power or 8potential0 of one conductor is equal to that of the other4 ,when they become equal of course the action ceases1 as there is equilibrium4 ,but when an apparatus like the galvanic battery is brought to bear so that the force of electricity from one conductor is made always greater than that of the other conductor1 we have a continuous flow while the action of the battery goes on4 ,one view of the principle is thus expressed by ,professor ,gordon3#af 8,if two metals be placed near together1 but not in contact1 in a liquid which acts chemically more upon one than upon the other1 the metals become charged1 so that the one least acted on is of higher potential than the one most acted on4 ,the difference of potential produced depends only upon the nature of the metals and of the liquid1 and not on the size or position of the plates4 ,as soon as the difference of potential has reached its constant value the chemical action ceases4 ,illustration3 ,fig4 #bbg4--,the ,voltaic arc4 8,if now the metals are connected by a wire outside the liquid the difference of potential begins to diminish1 and an electric current flows through the wire4 ,as soon as the difference of potential becomes less than the maximum for the metals and liquid1 chemical action recommences and brings it up to the maximum2 and thus if no disturbing cause interferes the current will continue until the metal most acted on is entirely dissolved40 ,the metal most acted on is considered the 8generating plate10 and is 8positive40 ,the other attacked less is 8negative10 and is known as the 8collecting plate10 and the zinc is the positive plate4 ,sir ,w4 ,thomson has shown that the electrical movement in the galvanic circuit is entirely due to the electrical difference produced at the surfaces of contact of the dissimilar metals4 ,the electro-motive force obtained is not the same with all metals4 ,we have mentioned that some are electro-positive and some electro-negative1 and it is with reference to each other that the metals are considered to be endowed with these properties respectively4 ,it all depends how the metals are arranged or coupled4 ,with reference to their behaviour in this respect scientists have arranged them in a series1 as follows3-- #a4 ,zinc4 #b4 ,cadmium4 #c4 ,tin4 #d4 ,lead4 #e4 ,iron4 #f4 ,nickel4 #g4 ,bismuth4 #h4 ,antimony4 #i4 ,copper4 #aj4 ,silver4 #aa4 ,gold4 #ab4 ,platinum4 #ac4 ,graphite4 ,each metal in the list is arranged so that it is electro-positive to any one below1 and electro-negative to any one above it4 ,there is another curious fact which should be mentioned4 ,in associating these metals it has been found that when two are brought into contact the electro-motive force becomes greater the more distant they are in the series given above2 in other words1 the force between any two is equal to the sum of the forces between those intervening between those two4 ,so when zinc is used with copper its force is not so great as when used with platinum4 ,it was ,herr ,g4 ,s4 ,ohm who laid down the law that the strength of the electric current is equal to the electro-motive force divided by the resistance1 for he proved that the 8resistance was inversely proportional to the strength of a current40 ,there are two other laws respecting currents2 viz41-- 7#a47 ,parallel currents in the same direction attract each other4 7#b47 ,parallel currents in opposite directions repel each other4 ,illustration3 ,fig4 #bbh4 ,chemical action of electricity4 ,fig4 #bbi4 ,upon these two hang all the varied phenomena of electro-dynamics4 ,that chemical action develops electricity we can perceive with the aid of the two cuts 7figs4 #bbh and #bbi74 ,if the wires be attached to the collecting-plate of a condenser of electricity and the metal plate of a cell1 as shown in the figure 7fig4 #bbh71 the electricity on the plate will be negative4 ,if the operation be reversed1 and the plate be put in connection with the acid1 and the metal with the earth1 the instrument will be charged with positive electricity4 ,in the other case1 when two cups are used1 united by a magnet so that the solutions 7one acid and the other alkaline7 can by capillary attraction unite upon the binding of the magnet1 and we place the wires as in fig4 #bbi1 the charge on the plate will be positive if it be in connection with the acid1 and negative if in communication with the alkaline solution4 ,every time there is chemical action between two bodies in contact electricity is produced--positive on one negative on the other1 and that is the fundamental principle of the voltaic pile4 ,the decomposition of water can also be effected by means of the electric current4 ,if two tubes or vessels be placed in a vase of water1 and the wires from the battery be inserted in them respectively1 the oxygen will go to the platinum or positive pole wire1 and the hydrogen to the zinc or negative pole4 ,this decomposition or 8splitting up0 of components was termed ,,electrolysis by ,faraday1 who gave a series of names to the action and the actors in these phenomena 7fig4 #bcj74 ,any liquid body1 such as the water we have just decomposed for instance1 ,faraday termed an electrolyte2 the surfaces where the current enters or leaves the body were called electrodes--the 8ways10 from odos1 a 8way02 the entry is the anode2 the leaving point the katode1 from ana1 8up10 and kata1 8down40 ,the electrolyte is divided into two portions1 8ions0 78movers071 which move towards the electrodes1 which are positive and negative4 ,in the case of the decomposition of water the hydrogen goes to the negative electrode1 the oxygen to the positive4 ,illustration3 ,fig4 #bcj4--;,decomposition of water4 ,there are a few observations to be made respecting electrolysis4 ,one rule is1 that it 8never takes place unless the electrolyte is in a liquid state40 ,the liquid state is essential4 ,it is also observed that the components go to the different electrodes2 such elements as go to the negative electrode are termed electro-positive1 the others electro-negative2 or1 as ,faraday termed them1 8anions0 or 8kations30 ,the chemical power or electrolytic action of the current is the same at all parts of the circuit2 the quantity of the substance decomposed is in exact proportion to the strength of the current4 ,faraday measured the strength of the electric current1 and invented for the purpose an instrument called the ,voltameter4 ,we have mentioned the ,galvanometer more than once1 and will proceed to describe it4 ,there are several forms of this instrument3 the ,tangent1 the ,marine1 and the ,reflecting ,galvanometers1 and the ,astatic1 or 8,multiplier40 ,in the first-named the direction of the current is determined by ,ampre's rule1 which is as follows3-- 8,imagine an observer placed in the wire so that the current shall pass through him from his feet to his head2 let him turn his face to the needle3 its north pole is always deflected to his left side40 ,the 8,tangent0 ,galvanometer consists of a vertical circle like an upright ring1 across which is a support in the centre holding a copper wire1 through which the electric current passes4 ,on this point 7where the wire is7 a needle is very lightly supported1 and when the instrument is to be used it is placed so that the plane of the circle is parallel to the line in which the needle points4 ,the current passes1 and the needle is deviated4 ,by noting which side the north end of the needle goes the direction of the current is ascertained1 and the length of the needle being small in comparison with the diameter of the circle through which the current passes1 the strength of the current in the vertical circle is in proportion to the tangent of the angle through which the needle turns4 ,hence the term 8,tangent0 ,galvanometer4 ,the 8,reflecting0 instrument is the invention of ,sir ,william ,thomson1 in which a mirror is attached to the needle1 and reflects a small focus of light upon a scale4 ,the movements1 however minute1 are easily read4 ,sir ,w4 ,thomson's ,galvanometers are extremely sensitive4 ,we need not mention any other varieties1 as full descriptions can easily be obtained4 ,we only need to indicate the mode of working4 ,illustration3 ,fig4 #bca4--;,galvanometer4 ,the accompanying illustration 7fig4 #bca7 shows an ,astatic ,galvanometer which may be used in two ways--either to measure strength of current1 or to find out a current2 in the latter case it would be termed a ,galvanoscope4 ,it is a compound needle instrument1 and consists of two needles placed in parallel directions with opposite poles above each other in a coil4 ,the wire coil is wound round a bobbin1 and the astatic needle is placed therein and suspended freely1 as in the illustration1 by a cocoon thread4 ,the upper needle moves upon a scale1 ,o ,o1 and the instrument is enclosed in a glass shade4 ,the screw1 ,v1 communicates with the upper needle1 and fixes it at zero point when ready for use4 ,the wires are fastened to the binding-screws1 and the current is then sent4 ,the needle is deflected accordingly1 and the number of degrees on the scale can be read off4 ,the uses of the galvanic current are many4 ,amongst them ,electroplating is perhaps the most generally useful1 though ,electrotyping is also a very important process in art4 ,a visitor to ,birmingham may view the process carried on there by some enterprising firms1 who have succeeded wonderfully in producing electro-plate4 ,the principle is very simple and easy to understand1 but the greatest care and watchfulness are required on the part of the men employed4 ,the principle1 as we have said1 is simple1 and consists in the fact that if a plate of metal be suspended and attached to the positive pole of a galvanic battery and immersed in a solution of the same metal1 the conducting substance hung opposite at the negative pole becomes coated with the metal immersed in the solution4 ,illustration3 ,fig4 #bcb4--,trough for electro-deposition4 ,illustration3 ,fig4 #bcc4--,plates immersed4 ,suppose we take a plate of silver1 and immerse it in cyanide of silver dissolved in cyanide of potassium2 a coating of silver will be deposited upon the nickel spoon or other article suspended at the other pole4 ,but to make the coating adhere the spoons1 forks1 etc41 are prepared for the bath by cleansing in caustic potash to remove grease1 and washed in nitric acid to remove all traces of oxide1 then are scoured with sand4 ,next1 a thin coating of mercury is put on by immersion in solution of nitrate of mercury4 ,finally1 they are hung in the bath4 ,a metal rod is hung across the bath 7fig4 #bcb71 and the plate is immersed4 ,if the rod to which the articles are suspended be attached to the zinc or negative pole1 and the plate of silver to the positive pole of the battery1 decomposition begins1 and the silver begins to attach itself to the suspended objects4 ,if it be desirable to give the plated articles a thick coating1 they are retained for a long time in the bath1 which is of some non-conducting material4 ,the dull appearance is easily removed by brushing and burnishing1 and then the 8,electro-plate0 is ready for the warehouse4 ,the gilding process is performed in the same manner1 a gold plate being substituted for the silver4 ,illustration3 ,fig4 #bcd4--,medico-galvanic ,battery4 ,illustration3 ,fig4 #bce4--;,battery in case4 ,,electrotyping may be briefly explained as follows3--,take two vessels1 ,a and ,b1 and in one1 ,a1 put some dilute sulphuric acid and two plates1 one of zinc1 ,z1 the other of copper1 ,d1 but be sure they are not touching each other2 each of these plates must have a piece of wire fastened1 by soldering to their upper parts4 ,in the vessel1 ,b1 put some solution of sulphate of copper and a small quantity of dilute sulphuric acid1 and attach another copper plate to the wire which comes from the copper plate in the acid2 this second copper plate is to be immersed in the solution of sulphate of copper1 and to the wire from the zinc plate is to be fixed the object to be coated4 ,if a medallion or other object in plaster1 it should be soaked in very hot wax and then brushed over with blacklead until the surface is perfectly blackened and bright2 the wire should be bound all round the margin and soldered 7as it were7 with melted wax to the medallion1 taking care that this wax also is well coated with blacklead4 ,if the object be now immersed in the sulphate of copper solution and kept at a short distance from the plate 7it must not touch it71 a coating of copper will soon cover the surface and form a perfect cast1 which1 when of sufficient thickness1 may be removed by filing the edge all round4 ,if instead of the plaster cast a copper coin or other copper object be used1 the blackleading is not required1 but the surface must be first made clean and bright4 ,many uses are made of the galvanic current by medical men4 ,if the circuit of the pile is closed and we take a wire in each hand and break contact1 a concussion will be felt in the joints of the arm and fingers1 and a certain contraction of the muscles4 ,the currents of electricity cause the shocks1 and by a peculiar arrangement by which the circuit can be closed or broken at pleasure1 a series of shocks can be sent through the body when it forms the connection between the poles of the battery4 ,we give illustrations of a medico-galvanic machine4 ,in fig4 #bce there are two batteries1 ,a and ,b1 with cells1 ,c ,d4 ,each battery consists of a central plate of platinized silver separated from the zinc plates by a piece of wood1 ,e and ,f2 the binding-screws are fastened to the silver plates1 and ,g ,h retain the zinc plates2 ,i is a copper band connecting the zinc plate of one battery with the silver plate of the other4 ,at ,z and opposite are wires leading to the coil machine4 ,the quantity and intensity of the current are regulated respectively by the indicator1 ,o1 and the wires1 ,q4 ,there is a point1 ,r ,s1 for the breaking of the contact2 ,p ,n are screws retaining the wires which lead to the handles1 ,u ,v1 grasped by the patients4 ,illustration3 ,fig4 #bcf4 ,fig4 #bcg4 ,fig4 #bch4 ,horse-shoe magnets4 ,the electric current is employed in many diseases1 and is of great use in some cases1 but the further consideration of it with reference to its medical applications does not fall within the scope of our present work4 ,we will now pass on to one of the most useful applications of the electric force1 the ,telegraph1 and in dealing with it we must make a few remarks upon magnetism4 ,first1 let us make an experiment or two1 and see the reciprocal action between electricity and magnetism4 7#a47 ,if we take a piece of iron of the form of a horse-shoe 7fig4 #bcf71 and wind around it copper wire1 and pass through the wire an electric current from our battery1 the iron will exhibit strong magnetic properties1 which it will lose when the current is interrupted4 ,the conducting wires are insulated with silk1 and the current will then travel in one direction4 7#b47 ,if we cover the ends of a non-magnetic piece of iron with coils of wire1 and rotate the magnet1 ,a ,b1 so as to cause the poles to approach each end of the iron alternately1 an electric current will be established in the wire4 7#c47 ,referring to the first experiment1 if we bring a needle in contact with the iron horse-shoe1 while the current is passing through the wire we shall find that the needle has become a magnet2 i4e41 that it will point due north and south when suspended4 ,we will now see what a ,magnet is1 and why it has obtained this name4 ,illustration3 ,fig4 #bci4--,magnetic attraction4 ,in ,magnesia1 in ,lydia1 in olden times was found a stone of peculiar attributes1 which had the property of attracting small portions of iron4 ,the ,chinese were acquainted with it1 and nowadays it is found in many places4 ,in our childhood we have all read of it in the story of 8,sinbad the ,sailor40 ,popularly it is known as the loadstone2 chemists call it magnetic oxide of iron 7,f#b,o#c74 ,this stone is a natural magnet4 ,in ,sweden it exists in great quantities as 8magnetic iron10 for it has a great affinity for that metal4 ,if we rub a piece of steel upon the loadstone we convert the former into a magnet--an artificial magnet as it is called1 and the magnetic needle so useful to us in our compasses and in the working of one form of the electric telegraph is thus obtained4 ,let us see how this needle acts4 ,illustration3 ,fig4 #bdj4--,simple touch4 ,illustration3 ,fig4 #bda4--;,double touch4 ,take a magnetic needle and dust upon it some iron filings4 ,you will observe that the filings will be attracted to both ends of the magnet1 but the centre will remain uncovered4 ,the ends of a magnet are termed 8poles10 the centre the equator4 ,so one end is north and the other south1 and we might perhaps imagine that the same characteristics would abide in the bar when it is cut in two4 ,but we find that as when a worm is divided1 each portion gets a new head or tail1 and makes a perfect worm1 so in the magnet each divided half becomes a perfect magnet with separate poles1 one of which always points to the north4 ,the poles of the magnet display the same phenomena as regards attraction and repulsion1 as do the opposite kinds of electricity4 ,if we suspend a magnet and bring the north pole of another to the north pole of the suspended magnet1 the latter will turn away2 but if we apply the north pole of one to the south pole of the other they will be attracted just as opposite electricities attract each other4 ,,magnetization is the term applied to the making of artificial magnets1 which act is accomplished by bringing the needle in contact with other magnets1 or sometimes by means of the electric current4 ,if we carefully stroke the needle with the magnet1 always in the same direction1 lifting the magnet and beginning afresh every time1 we shall magnetize the needle1 but with a different polarity from the pole it was rubbed with4 ,a magnet rubbing its north pole against a needle will make the latter's point south1 and vice vers4 ,now that we have seen how the 8magnetic needle0 is arrived at1 we can proceed to explain the electric telegraph4 ,the term telegraph is derived from the ,greek words tele1 8far10 and graphein1 8to write10 and now includes all modes of signalling4 ,signalling1 or telegraphing1 is of very ancient origin2 the ,roman generals spelt words by fire4 ,the beacons fired on the hills1 the 8,fiery ,cross10 and other ancient modes are well known4 ,the semaphore and flags have long been and are still used as modes of signalling1 while the flashing of the heliograph 8telegraphs0 to a distant camp4 ,the ,semaphore was invented by ,chapp1 and was really the first practical system of telegraphy4 ,it was adopted in #agid1 but before this1 in #agec1 a letter appeared in the ,scots ,magazine1 by ,charles ,marshall1 suggesting that signals should be given by means of electric wires1 equal in number to the letters of the alphabet4 ,soon afterwards ,lesage1 of ,geneva1 made an electric telegraph to be worked by frictional electricity1 and many ingenious attempts were subsequently made to utilize electricity for signalling purposes1 but without any permanent success2 indeed1 the ,british government were quite content with their semaphores1 for they wrote that 8telegraphs of any kind are now wholly unnecessary1 and no other than the one now in use will be adopted06 ,the ,electric ,telegraph has had considerable antiquity claimed for it1 but it is pretty certain that the discovery made by ,doctor ,watson1 in #agdg1 that electricity would pass through wires1 and that the earth would complete the circuit1 gave the first impetus to the ,electric ,telegraph4 ,doctor ,watson was enabled to transmit shocks across the ,thames1 and made experiments at ,shooters ,hill4 ,franklin did likewise across the ,schuykill in #agdh1 and ,de ,luc performed the same experiments on the ,lake of ,geneva4 ,both ,lesage and ,lomond caused pith balls to diverge at distant points1 and in #agid ,reizen made use of the electric spark for transmitting signals1 and made strips of foil show out certain letters when the spark passed4 ,he had a wire and a return wire for each letter of the alphabet4 ,these were all slow advances1 and subsequently many learned men in ,europe sought to improve upon the ideas then promulgated4 ,we read of telegraphs constructed at ,madrid by ,salv and ,betancourt in #agig and #agih1 one extending for more than twenty miles4 ,the first-named gentleman finally proposed to substitute the ,voltaic pile for the usual machine1 and ,ronalds and ,dyar in ,england and ,new ,york respectively employed frictional electricity with some success4 ,the latter sent charges of frictional electricity through a wire1 and they were recorded by being made to pass through litmus paper4 ,the distances between the discharges were intended to indicate the letters of the alphabet1 but even if the experiment was fairly tried it failed1 for little was heard of the result4 ,after the invention of ,volta's pile1 which ,salv wished to adopt1 ,smmering began his experiments4 ,he used thirty-five wires1 set up vertically at the bottom of a glass reservoir of water1 and terminating in gold points4 ,these wires ended in the opposite direction in brass plates attached to a bar of wood4 ,at one end the points and at the other the plates bore the same letters respectively2 hydrogen at one gold point1 and oxygen at another1 and two different letters were indicated when the current was sent through any two plates4 ,this arrangement was afterwards improved upon1 and only two wires retained4 ,it was not until electro-magnetism had been developed1 however1 that rstead found out the power of electricity to deflect the magnetised needle1 and in #ahbj1 ,scheweigger added a 8multiplier40 ,then came ,arago into the field with his discovery1 that a 8wire carrying a current could magnetise a steel rod40 ,ampre substituted a helix for a straight wire1 and ,sturgeon used soft iron for steel1 and developed the electro-magnet4 ,daniell's battery1 and ,faraday's discoveries of magneto-electricity and the induction coil were the means of putting a constant supply of electricity at the service of the telegraph and so on1 till #ahcj brought out a more practical method introduced by ,schilling4 ,in that year ,baron ,schilling made a telegraph1 and exhibited it in #ahcb at ,bonn4 ,this invention1 with five vertical needles1 was shown to ,mr4 ,cooke in #ahcf4 ,but in #ahcd1 ,gauss and ,weber had succeeded in sending signals by means of a voltaic current acting upon a magnetised needle1 and this apparatus was really the first practical electric telegraph in use1 and it was much improved by ,professor ,steinheil of ,munich4 ,they employed a magnetic-electro machine1 and caused a bar to move in certain directions to indicate certain letters of the alphabet4 ,this was really of value1 but ,steinheil1 the pupil of ,gauss1 assisted by his government1 employed only a single wire1 and made the earth complete the circuit for him instead of having a return wire as his predecessors had4 ,this telegraph was perfected by a series of bells1 which gave different tones for different letters1 and he also caused the needle to make certain tracings as it moved upon a paper slip1 something like the ,morse pattern1 which was completed in #ahcg4 ,professor ,morse1 in #ahcb1 conceived the idea of an electric telegraph but his claim was disputed by a ,doctor ,jackson1 who was on the same vessel when the subject was discussed4 ,we need not enter into the details of the controversy4 ,mr4 ,morse won the day1 and patented his invention4 8,it was once a popular fallacy in ,england and elsewhere that ,messrs4 ,cooke and ,wheatstone were the original inventors of the electric telegraph4 ,the electric telegraph had1 properly speaking1 no inventor4444 ,messrs4 ,cooke and ,wheatstone were1 however1 the first who established a telegraph for practical purposes comparatively on a large scale1 and in which the public were more nearly concerned4444 ,therefore it was that the names of these enterprising and talented inventors came to the public ear1 while those of ,ampre and ,steinheil remained comparatively unknown4#ag ,the telegraph1 as used in ,great ,britain1 was the result of the co-operation of ,professors ,cooke and ,wheatstone4 ,mr4 ,cooke1 in #ahcf1 having seen the needle telegraph when in ,heidelberg1 made certain designs1 and soon entered into partnership with ,professor ,wheatstone for the application of electric telegraphs to railways4 ,their apparatus with five needles and five wires was put up on the ,london and ,north-,western 7then ,london and ,birmingham7 and ,great ,western lines1 but proved too expensive4 ,the instrument was subsequently modified1 and is used on the ,english railways still4 ,illustration3 ,fig4 #bdb4--;,cell4 ,we may now proceed to look at the ,wheatstone needle telegraph and see the method of working it4 ,we know already that when a pair of metallic plates are immersed in a fluid which acts chemically more rapidly on the one than the other1 and a wire connects the upper parts of these plates1 this wonderful agency is set in motion1 and circulates from the one plate to the other 7fig4 #bdb74 ,this arrangement may be best shown by using one plate of zinc and the other of copper1 and a dilute solution of sulphuric acid for the liquid2 this1 however1 produces by far too little of the agent to be used on a telegraphic line1 there are therefore combinations of such pairs of plates1 so arranged that the power of one pair shall be added to the next in such a way that at the end of the series 7called a 8battery07 there shall be a great increase of the power accumulated2 this arrangement is shown in fig4 #bdd4 ,now 7if the power be sufficient7 it does not signify what length of wire there may be between the two ends of this arrangement or 8battery02 whether they be connected by a few feet or many hundred miles1 the electricity passes instantaneously from one end to the other2 and furthermore1 it has been found in practice1 that this electrical influence can be transmitted through the earth in one direction if sent by a wire in the other2 for instance1 if a wire from one end of the battery be carried on from ,london to ,liverpool1 instead of having another from ,liverpool to ,london1 to connect the two ends of the battery1 it is found to answer the same purpose if the end of the wire at ,liverpool be fastened to a plate of metal buried beneath the surface of the earth1 and the other end of the battery at ,london furnished with a similar plate1 also buried4 ,in this arrangement1 the electricity will pass beneath the surface of the earth from ,liverpool to ,london1 and through the wire from ,london to ,liverpool1 thus completing the circuit4 ,the end from which the electricity passes is called the 8positive electrode10 that to which it returns1 the 8negative electrode40 ,fig4 #bde will show this arrangement4 ,illustration3 ,fig4 #bdc4--,the ,needle ,telegraph4 ,illustration3 ,fig4 #bdd4--,the ,battery4 ,illustration3 ,fig4 #bde4--,the circuit4 ,illustration3 ,fig4 #bdf4 ,fig4 #bdg4 ,fig4 #bdh4 ,magnetic needles4 ,if a bar-magnet be suspended on a pivot so that it may turn freely1 it will 7as is well known7 turn with one end to the north1 which is owing to a current of natural electricity passing round the earth in the direction of east and west1 the magnet crossing the current at a right angle2 and if a coil of wire coated with silk 7to keep one part of the coil from another7 be placed round1 above1 and below the long axis of a bar of steel1 as shown at fig4 #bdf1 and a current of electricity passed through the wire1 the steel becomes a magnet1 and will take a direction similar to the natural magnet1 more or less1 at right angles to this coil1 as in fig4 #bdg1 according to the intensity of the current2 and the instant this electrical current is stopped1 it will resume its former direction4 ,this fact has been made use of to form the principal feature of all ,english telegraphs2 such a needle is mounted in an upright position1 and instead of its tendency to turn to the north1 a tendency to maintain the upright position is given to it by having one of the arms of the magnet a little heavier than the other2 such a magnet having a coil of wire surrounding it4 ,when the electric current passes through the coil1 it will turn out of the upright position to either one side or the other1 according to the direction of the current1 from its tendency to assume a position at an angle thereto 7fig4 #bdh72 if the current be stopped even for an instant1 then the needle1 or magnet1 will again assume its upright position4 ,the pivot of this magnet is brought forward1 and has on its front part another needle1 which turns with it2 this is visible on the outside of the apparatus1 and is looked at to ascertain the movement of the one within4 ,there is also an arrangement called a 8commutator10 so contrived1 that by moving a handle to the right or left1 a connection shall be made with either end of the battery1 and thereby cause the direction of the current and needle to be changed at pleasure2 also by moving the handle into an upright position the current shall be stopped2 and finally1 by a third movement1 a bell shall be rung4 ,now1 as has already been explained1 when the current goes in one direction1 the magnetic needle is deflected in that direction2 and when the current is reversed the position of the needle is also reversed1 and when the current is cut off the needle will resume its perpendicular position4 ,if two such needles and two such handles be at each station1 when the handles at one station are moved1 the needles at the other station will take on a similar movement2 and when the handles at that station are moved1 the needles at the first station will be moved to correspond4 ,this constitutes the system of communication kept up by the electric telegraphs in ,england2 but it remains to be shown how all the letters of the alphabet and numerals can be represented by the movements of the two handles4 ,these handles can be placed in eight positions 7besides the upright one7 by a single movement of each hand1 as may be seen in fig4 #bdi2 and these eight signals if repeated1 or made twice in rapid succession will make eight more1 and by being repeated three times will constitute a third eight1 making twenty-four2 finally1 by a rapid motion right and left1 they may be caused to signify a fourth eight1 or thirty-two signals1 which are found to be sufficient for every purpose1 and by practice may be both produced and read off with facility4 ,before a message is about to be delivered the commutator is so placed as to ring a bell1 which is done by the same arrangement as in a common alarm-clock1 but the action is set in motion by a peculiar contrivance1 which depends upon the property a bar of soft iron has of becoming magnetic when a wire is wound round it and a current of electricity passed through this wire2 this magnetic property exists only as long as the current passes1 and stops the instant it is cut off4 ,the catch of the alarm is disengaged by the movement of a bar of iron being drawn to the magnet while the current passes1 and forced back again by a spring when it is stopped1 thus setting in action the mechanism of the alarm2 or in some cases there is a simple contrivance for causing a rapid flow and stoppage of the electricity1 so that the bar is alternately attracted by the magnet and released by the spring1 and this motion rings the bell as long as it is continued4 ,the bell is always rung to give notice that a message is about to be sent1 and at the station where it rings1 the bell at the former station is rung in return1 to show that they are prepared to receive the message3 which is then spelt1 letter after letter1 by moving the handles into the proper positions1 and as it is being sent1 the eye is kept on the dials1 certain single signs are made and recognised1 which will communicate any reply from the station to which the message is being sent1 such as 8repeat10 or 8not understood40 ,the wires which convey the electricity are made of galvanised iron 7iron coated with zinc71 and as they must be kept from all communication with the earth by some substance incapable of conducting it1 they are therefore stretched between wooden poles 7fig4 #bej71 and rest upon sockets or supports of glass or glazed earthenware1 which are both substances incapable of conducting the electricity to the earth 7fig4 #bea71 and in order that these may be quite dry1 an inverted cup of metal1 glass1 or earthenware is placed over it1 or the whole is blown or moulded in one piece4 ,if the support for the wires were not kept from the rain1 the wet would form a conducting surface1 and allow the electricity to escape into the earth4 ,illustration3 ,fig4 #bdi4--;,handles and needles of telegraph4 ,illustration3 ,fig4 #bej4--,telegraph wires4 ,illustration3 ,fig4 #bea4--;,insulator4 ,the ,telegraph ,alphabet1 in the two-needle instrument1 now not generally used in ,england1 is given below4 ,,two-,,needle ,,alphabet4 ,movements of ,first ,needle4 ,of ,second ,needle4 ,of both ,needles together4 ,a is signified by moving needle once to right ,b 8 8 8 once to left ,c ,by moving needle once to right ,d 8 8 once to left ,e ,moving to right4 ,f ,moving to left4 ,g twice to right ,h 8 to left ,i 7or ,j7 ,twice to right ,k 8 left ,l ,twice to right4 ,m ,twice to left4 ,n ,one to right1 one to left ,o ,one to left1 one to right ,p ,one to right1 one to left ,o ,one to left1 one to right ,r ,one to right1 one to left4 ,s ,one to left1 one to right4 ,t ,two to right1 one to left ,u ,one to right1 two to left ,v ,two to right1 one to left ,w ,x ,one to right1 two to left ,y ,two to right1 one to left4 ,z ,one to right1 two to left4 ,in the single needle instrument the letters are indicated by right and left vibrations1 from ,a one right1 to ,b one right and left1 and so on1 increasing to ,z4 ,this mode is now generally used4 ,the manner in which the current passes is shown by the following illustrations 7figs4 #beb1 #bec74 ,illustration3 ,fig #beb4--,passage of the current 7#a74 ,illustration3 ,fig4 #bec4--,passage of the current 7#b74 ,for the sake of clearness1 the diagram has been drawn with simple lines only4 ,in the real needle-machine the construction is much more complicated2 perspective drawings of it may be seen in ,lardner's 8,electric ,telegraph10 and numerous other works4 ,in fig4 #a1 ,b is a single cell of a battery containing a plate of copper1 ,c1 and a plate of zinc1 ,z1 immersed in sulphuric acid and water4 ,h is the handle of the instrument1 turning from left to right1 and vice vers1 like the handle of a door1 consisting of two pieces of brass insulated from each other by being inserted in an axis of ivory4 ,to the ends of the two pieces of brass are fixed the wires1 ,,cw and ,,zw1 leading from the copper and zinc ends of the cell respectively4 ,fixed on each side of the handle are two plates of metal1 which may be called ,,lp1 the left plate1 and ,,rp1 the right plate4 ,they are connected with the needle wire1 ,,nw1 which passes before and behind the magnetized needle1 ,n1 suspended perpendicularly on its axis1 with its north pole upwards4 ,as long as the wires1 ,,cw and ,,zw1 remain insulated from each other1 no current passes from the cell2 but as soon as the handle1 ,h1 is turned1 so that the copper end touches the left plate 7fig4 #b71 and the zinc end touches the right1 communication is established between the plates of the cell1 and the current commencing at the copper passes along ,,cw1 the top half of ,h1 into ,,lp1 along ,n ,w1 travelling up before and down behind the needle1 causing it to deflect to the observer's left1 according to the rule given above4 ,reaching ,,rp1 it passes downwards to the cell to ,z1 and so on to ,c1 continuing its travels and keeping the needle deflected as long as the handle remains in contact with the plates4 ,if it is required to deflect the needle to the right1 the handle is turned to the right1 bringing its copper end in contact with the right plate1 causing the current to travel in the opposite direction4 ,by following the current from the copper to the zinc1 as indicated by the arrows in fig4 #c1 it will be seen that it now travels up behind and down before the needle1 deflecting it to the observer's right4 ,thus1 by causing a current of voltaic electricity to pass alternately up before and down behind1 and up behind and down before1 the needle is moved to the left or the right at will4 ,the way in which the current is made to act on a distant needle is now simple4 ,the following figure 7fig4 #bec7 shows the arrangement4 ,the left portion of the figure represents an instrument at ,london1 that on the right an instrument at ,york4 ,the needle-wire1 instead of being continued directly to the zinc plate of the battery1 passes away from the needle over poles to ,york1 where it joins an instrument similar in all respects to that at ,london4 ,it passes similarly before and behind a magnetized needle1 joining the right plate of the instrument4 ,as long as the two plates are unconnected1 no current can pass4 ,the current is therefore completed by a contrivance which may be represented by the semicircular piece of metal1 ,k4 ,in practice the two plates or springs1 which1 when not in use1 are always pressed against the connector1 ,k1 which is a cross-piece on the top of the handle1 keeping the ,london needle in circuit with the ,york battery1 and vice vers4 ,as soon as ,london uses his handle1 it presses the spring-plate1 and puts his needle out of the ,york circuit1 the current he sets up sending ,york needle to the right or left1 as the case maybe4 ,the second wire connecting the left ,york plate with the right ,london plate is1 it will be seen1 not carried along like the first wire4 ,use is made in this case of the conducting power of the earth itself1 plates from the wires being buried many feet below the surface at ,london and ,york4 ,when ,london wishes to speak to ,york1 he first signifies his intention of so doing by ringing ,york's alarum4 ,this he effects by sending a current through an electro-magnet placed above ,york's instrument4 ,the armature is attracted1 and frees the detent of the alarum1 setting it ringing until ,york signals ready4 ,london then stops the bell1 and commences his message4 ,by following the direction of the current1 when the handle is turned to the left1 as in fig4 #d within fig4 #bec1 it will be readily seen how this is effected3 commencing with ,london's copper1 ,,lc1 it passes up before and down behind ,london's needle1 flowing along the wire between the two cities to ,york's needle1 up before and down behind which it travels1 sending it also to the left4 ,it then passes to ,york's right plate1 through the connector to the left plate1 and so on to earth at ,york1 coming to the surface again at ,london1 passing through ,london's right plate and through the lower part of the handle to the zinc of the battery4 ,the reverse current may be easily followed4 ,any number of instruments with similar needles may be interposed along the course of the wire4 ,when the operator wishes to speak to any particular one1 he rings all the bells for attention1 and then signals ,derby or ,nottingham1 as the case may be4 ,they all then throw their instruments out of current except the one required4 ,the mode by which the needle movements are converted into language is simple4 ,a is signalled by causing the needle to vibrate once to the right1 ,b once right and once left1 ,c once right and twice left2 and so on1 as arranged4 ,the following is the alphabet 7with numbers7 once in use on the ,south-,eastern ,railway for the double-needle instrument4 ,the table is taken from ,mr4 ,walker's translation of ,de la ,rive's work on ,electricity and ,magnetism4 ,a is signified by two movements of left needle to left4 ,b 0 by three 0 0 0 ,c 7and fig4 #a7 by two 0 0 right first1 then left4 ,d 7and fig4 #b7 by two 0 0 left first1 then right4 ,e 7and fig4 #c7 by one 0 0 to the right4 ,f by two 0 0 0 ,g by three 0 0 0 ,h 7and fig4 #d7 by one 0 right needle to the left4 ,i by two 0 0 0 ,j 7same as ,g74 ,k by three 0 0 0 ,l 7and fig4 #e7 by two 0 0 right and left4 ,m 7and fig4 #f7 by two 0 0 left and right4 ,n 7and fig4 #g7 by one 0 0 to the right4 ,o by two 0 0 0 ,p by three 0 0 0 ,q 7same as ,k74 ,r 7and fig4 #h7 by one parallel movement of lower points1 both needles to the left4 ,s by two 0 0 0 ,t by three 0 0 0 ,u 7and fig4 #i7 by two 0 0 first right1 then left4 ,v 7and fig4 #j7 by two 0 0 first left1 then right4 ,w by one movement of both needles 7lower points7 to right4 ,x by two 0 0 0 0 ,y by three 0 0 0 0 ,z 7same as ,s7 or specially4 ,the ,morse system of telegraphy was first brought out in #ahdd1 and was worked by means of a ,voltaic battery1 an electro-magnet being used at the receiving station4 ,this magnet attracted an 8armature10 and by it dots or lines are marked on a moving paper band by a point at the other end of the wire1 on the register in which the paper is carried by rollers which move out by clockwork4 ,the lever being 8tapped0 down in fast or slow pressures will give a corresponding series of dots or lines 7according as the pressure is long or short7 upon the moving strip of paper at the receiving station4 ,three taps will give ,c1 one tap and a pause will make ,a4 ,the dots are 8taps0 on the key1 the lines brief 8rests0 on it1 as will be seen from the alphabet below1 which is given as a specimen4 ,,morse ,,alphabet4 ,a 4- ,b -444 ,c 44 4 ,d -44 ,e 4 ,f 4-4 ,g --4 ,h 4444 ,i 44 ,j -4-4 ,k -4- ,l - ,m -- ,n -4 ,o 4 4 ,p 44444 ,q 44-4 ,r 4 44 ,s 444 ,t - ,u 44- ,v 444- ,w 4-- ,x 4-44 ,y 44 44 ,z 444 4 ,,numbers4 #a 4--4 #b 44-44 #c 444-4 #d 4444- #e --- #f 444444 #g --44 #h -4444 #i -44- #j ,the various stops are also indicated in the same manner by combinations of dots and lines4 ,the ,atlantic telegraph cables and similar enclosed wires between other countries are too well known to need detailed description4 ,there is a great variety of telegraphic instruments4 ,the dial1 and other arrangements1 are very common1 and the ,wheatstone ,key instrument is supplied to private firms as being the most handy4 ,it requires but a very short apprenticeship1 and any person who is handy can easily learn to work it in a few minutes4 ,the apparatus consists of a dial upon which the letters of the alphabet are printed1 each letter being supplied with a key or stop4 ,a pointer is placed in the centre1 as in the wheel barometer1 and there is a handle beneath4 ,in front1 upon a sloping board1 is another dial plate and pointer2 thus we have the receiver and transmitter before us in a very small space4 ,illustration3 ,fig4 #bed4--,receiver4 ,dial ,telegraph4 ,fig4 #bee4--,manipulator4 ,when it is necessary to work the instrument a bell is rung by turning the handle rapidly4 ,to speak by the instrument it is necessary to keep turning the handle with the right hand while the fingers of the left are employed in pressing down in as rapid succession as practice will permit the keys corresponding to the letters on the dial while the handle is kept turning4 ,when a word is completed the operator must stop at the at the top1 and then begin again1 stopping after each word4 ,when all is said1 a couple of rapid turns of the dial will signify that you have ended4 ,there are many other systems of telegraph1 but all are dependent upon the same principles4 ,the accompanying illustrations 7figs4 #bed1 #bee7 show a dial telegraph of a simple kind1 which almost explains itself4 ,the first figure is the receiver1 on which is a pointer fixed to a dial-plate having the letters of the alphabet inscribed around it4 ,when the manipulator is being worked the dart points to the letters in succession of the words used1 and they are separately spelt4 ,the manipulator 7fig4 #bee71 by closing and opening the circuit1 works the needle4 ,in the manipulator we have a wheel with an index point fixed above it4 ,in this wheel are thirteen teeth1 with the openings between them filled with ivory4 ,the axis of the wheel is in contact with the wire from the positive pole1 p1 and a spring attached to the wire or by the binding-screw1 t1 presses against the circumference of the wheel1 and completes the circuit4 ,when the wheel is placed so that the arrow point is above the 1 the needle of the receiver is also at 4 ,by turning the wheel to bring the needle to ,a1 the spring on the circumference is passed from an ivory 8tooth0 to a 8metal0 one2 the circuit is closed1 the point of the receiver also turns to ,a1 and so on through the word by successive closing and breaking of the circuit4 ,as there are a great many other applications of electricity of which we have to treat1--the ,electric ,light1 and ,mr4 ,edison's other inventions1--our space will not permit a much more detailed account of the telegraph1 but there are some incidents connected with its progress which it would be as well to mention4 ,illustration3 ,fig4 #bef4--;,electric cable4 ,illustration3 ,fig4 #beg4--,ocean cable4 ,alexander ,bain1 about #ahdj1 attempted to produce a printing telegraph1 and in #ahdf he actually accomplished a registering apparatus1 which was an application of the principles of ,dyar and ,davy4 ,but although ,bain's system was good1 ,morse had the advantage of possession in the ,united ,states1 where it was tried1 and ,bain went out of fashion4 ,bain's system was1 in fact1 the present chemical 8automatic0 telegraph1 which has been perfected for rapid transmission4 ,bakewell's instrument1 which has been improved upon by later electricians1 is termed the fac-simile telegraph4 ,the message to be sent is written with a pen which has been dipped in varnish 7for ink71 and the characters are inscribed upon prepared tinfoil4 ,the message is then put upon a cylinder covered with prepared paper1 and has a pointer attached4 ,there is a precisely similar cylinder at the receiving station4 ,when the cylinders are simultaneously set going1 the point at one will trace a spiral line as the first 7transmitting7 point passes round its cylinder4 ,however1 as the latter 8stylus0 meets the varnish letters a break occurs1 and these spaces are exactly reproduced as blanks at the other end1 and the form of the letters can be seen4 ,coselli1 in his adaptation1 caused dark letters to be registered on a white ground1 and thus simplified matters4 ,since then we have had printing telegraphs1 and dials1 and writing machines1 one of which will be described presently4 ,submarine telegraphs were1 it is said1 first suggested by ,salv in #agig1 and ,wheatstone1 in #ahdj1 declared that it was quite possible to connect ,england and ,france by wire4 ,morse and ,calt experimented with submarine cables in ,america1 and ,lieutenant ,siemens first applied gutta-percha to the wires as an insulator in the ,prussian line of telegraph across the ,rhine4 ,the ,english laid a wire between ,dover and ,calais1 which was broken1 but successfully relaid4 ,and so on1 till in #aheg the great project of the ,atlantic cable was broached4 ,we give illustrations of the cables2 the circumstances connected with the laying of which1 and the enthusiasm over the successful accomplishment of the task1 must be in the memory of all4 ,the readings of the messages were shown by delicate galvanometers1 the beam of light being reflected from a mirror4 ,this cable was lost1 and in #ahfb ,mr4 ,field came over to urge the importance of the submarine cable between this country and ,america4 ,the cable was shipped on the ,great ,eastern in #ahfe1 and was #b1ahf miles long4 ,it consisted of seven copper wires twisted1 and covered with gutta-percha4 ,the outside coating consists of ten iron wires surrounded by manilla yarn4 ,but this cable broke1 and a third was made and laid in #ahff4 ,the old cable was then recovered and spliced4 ,there are some two hundred cables now in existence1 the last being the ,cape cable1 laid when the ,boer ,war was engaging our attention4 ,the transmitting apparatus of ,mr4 ,varley and ,sir ,w4 ,thomson has greatly accelerated the rapidity of messages1 and ,thomson's syphon recorder farther increased the speed4 ,the following description of a new system is from ,scribner's ,magazine for #ahhj3-- 8,,new ,,telegraphic ,,system4 8,a new system of sending and receiving electrical impulses over an insulated wire has recently been brought into successful operation1 that seems to promise not only a radical change in the present methods of telegraphing1 but a material gain in the speed and cost of sending messages by wire4 ,it is founded on a union of the so-called 8automatic0 and 8chemical0 systems of telegraphy4 ,the first of these employs a strip of paper having1 by some mechanical means1 a series of small holes punched in it1 the design being to pass the perforated strip under a needle1 or stylus1 in electrical connection with the line4 ,this stylus1 on passing over the paper1 opens the circuit1 but in passing one of the holes1 drops through and closes it1--this alternate making and breaking of the circuit transmitting the message4 ,the chemical telegraph records any electrical impulses sent over a line by staining a strip of prepared paper passing under it4 ,this is founded on the fact that electricity has the power of decomposing certain chemicals1 and if paper is soaked in these chemicals and submitted to the action of electricity1 it will be discoloured wherever the current passes4 ,while both of these systems have been used1 neither has been able to compete with the more simple ,morse key and sounder1 and it has remained for the new system to bring them to a position where they may come into general use4 ,the new system is a modification and combination of the automatic and chemical systems1 the transmitting being performed by means of a perforated strip of paper1 and the receiving of the message being recorded by the discolouration of chemically prepared paper4 ,the process is entirely mechanical and chemical1 the telegraph operator having no direct control over the message1 either by sight1 sound1 or touch4 ,the written message is sent to the operating-room1 and given to the person using the perforating machine4 ,this consists of a small key-board1 with black and white keys1 each marked with a letter or sign1 and an ingenious system of levers1 operated by the keys1 for punching small holes in a ribbon of paper moving past the side of the machine4 ,the machine stands upon a small table1 and under it is a treadle for giving motion to the feeding apparatus for supplying the paper to the machine4 ,the operator moves the treadle with his feet1 and at the same time touches each key to spell out the message4 ,in a very few seconds the message is imprinted on the ribbon in the form of a double row of small perforations1 each group of two holes representing a dash1 and each single hole a dot1 as in the ,morse alphabet4 ,each letter is separated from the next by a longer dash1 and each word by a still longer dash1 and each sentence by a dash of indefinite length4 ,this spacing of the letters is performed automatically1 the spacing of words and sentences is performed by the operator4 ,the perforated slip containing the message is then sent to the transmitting machine4 ,this consists essentially of a metallic wheel1 divided into two sections by means of a thin insulation of hard rubber4 ,one section of the wheel is connected with the positive pole of the battery1 and the other section with the negative pole4 ,a pair of fine metallic brushes1 both of which are connected directly with the line1 are suspended above the wheel1 and are arranged so as to press lightly upon the latter1 when desired4 ,when resting on the wheel the circuit is closed1 and when raised above it the circuit is broken4 ,the perforated strip is1 by a simple piece of mechanism1 made to pass over the face of this wheel and under the brushes4 ,while the paper is passing1 both brushes are raised from the wheel1 and slide over the paper1 and the circuit is broken4 ,on passing a hole1 one of the brushes drops through and closes the circuit for an instant4 ,on passing two or more holes1 arranged in a series close together1 the brush closes the circuit for a shorter or longer time1 according to the number of holes1 and as the perforations on the paper are arranged in two rows1 alternating from one to the other1 the brushes are used alternately1 and the polarity of the current is continually changed with every impulse sent over the line4 ,no special skill is required in sending a message1 as the operator has only to put the perforated strip in the machine and turn a hand-crank1 to cause it to pass rapidly under the brushes1 and with a little practice1 a young girl can send messages at the rate of one thousand words a minute1 with absolute precision4 ,the receiving apparatus consists essentially of a simple piece of mechanism for causing a strip of chemically prepared paper to pass rapidly under two small needles that are connected with the line4 ,as the paper passes the needles1 the electricity sent over the line from the transmitting machine seeks the earth through the wet paper and the machine1 and in passing discolours the paper1 each stain representing a dot or dash1 and the message is printed on the paper in a double row of marks at the same speed with which it was dispatched4 ,in practice1 a ,morse key and sounder is placed at each end of the line1 and on sending a message the transmitting operator calls the receiving station1 and when the operator at the distant end replies1 both turn the cranks in their machine swiftly1 and the message is sent and received at an average speed of one thousand words a minute4 ,the message received is given to a person using a type-writer1 and at once translated into print and sent out by the messenger boy4 ,it is found in practice that two operators1 one at each end of a single wire of indefinite length1 can keep fifteen operators fully employed in preparing the messages1 and fifteen girls busy in translating and printing the messages for delivery4 ,the system is of ,american origin40 ,of the hundred and one uses to which electric wires are now appropriated--of the alarms1 fire-calls1 clocks1 etc4--we need not speak4 ,we must pass on to the ,writing ,machine 7fig4 #beh7 before we make mention of ,mr4 ,edison's inventions4 ,the ,writing ,machine is as remarkable for the simplicity of its mechanism as for the facility and ease with which it can be used4 ,it was invented by ,remington1 the ,american1 whose name is so universally known in connection with a repeating rifle4 ,he makes these writing machines in his own factory1 where he associates them with rifles and sewing machines--implements for war and peace4 ,the appearance of the ,writing ,machine may be easily perceived from the illustration 7fig4 #beh71 which is drawn to scale one-fourth of the actual size4 ,it comprises a key-board1 upon which there are forty-four keys or stops1 including numbers from #b to #i1 the i and o of the alphabet serving for numbers #a and #j1 and all the letters of the alphabet arranged in the manner most convenient for manipulation4 ,there are also the various accents and stops1 with note of interrogation1 etc4 ,the flat ruler at the base of the key-board is struck when it is necessary to separate one word from another4 ,in the interior of the apparatus every letter is attached to a small hammer1 and corresponds to the pressure bestowed upon the notes1 which are disposed in a circle4 ,if ,a1 for example1 be touched upon the key-board1 the hammer will bring ,a to the centre of the circle1 and so every letter of the word will be1 by such action1 brought to the centre of the circle in succession4 ,the paper upon which the letter is printed is wound upon a cylinder mounted upon a slide1 as seen in the upper portion of the illustration4 ,when the letter is pressed down on the key-board the corresponding hammer strikes against the cylinder1 between which and the hammer is a ribbon prepared with a special ink4 ,the letter being in relief like ordinary type is impressed upon the paper4 ,the slide upon which the paper is mounted is so arranged as to move from right to left exactly a letter-breadth after each impression4 ,thus as every hammer strikes at the same spot a regular succession of letters are printed off1 the paper moving with regularity4 ,when the line is filled--that is1 when the paper has moved across the cylinder--a bell rings1 and a handle is moved by the operator who is thus warned4 ,the lever moved brings the slide back again1 and a new plain surface is ready to commence upon the cylinder moving upwards at the same time1 and displaying the printed line4 ,illustration3 ,fig4 #beh4--,remington's ,writing ,machine4 ,in operating both hands may be employed1 but between each word care should be taken to press down the flat board at the base of the key-board1 which has the effect of leaving a space upon the paper4 ,immediately the sound of the warning bell is heard the lever at the right-hand side must be lowered4 ,the word can be finished in the line following if it be not concluded1 the hyphen button being pressed to indicate the continuation4 ,the paper used must not exceed the width of the cylinder1 but it may be of any less width1 and a post-card or any small sheet of paper may be substituted4 ,if the width be thus limited the length may be indefinite1 and a very long line of paper may be used if desirable4 ,the cylinder being made of gutta-percha offers a soft surface to the impression of the hammer1 and causes the letter to assume greater distinctness4 ,the inked ribbon which passes underneath the paper is so arranged that no two successive letters strike it on the same place4 ,it moves from an ink reservoir on the right to another on the opposite side1 and it can be made to return beneath the paper1 thus keeping up the supply4 ,the impression being made in copying ink1 the message or letter when finished can easily be reproduced in an ordinary press4 ,the characters are all 8capitals40 ,at first it may be found a slow means of writing1 and the manipulator may imagine he can do better without it4 ,but if the author be certain of what he intends to say1 after a little practice at the instrument1 and when he becomes accustomed to the positions of the various letters1 etc41 the rate at which words can be printed off will far exceed that at which even rapid writers can work4 ,a young ,english lady after some days' practice was able to write as many as ninety words a minute with this machine--a rate more than double the average writing rate of penmanship4 ,when such a rate or an approximation to it can be attained1 those who are quick in their ideas will find the machine a great saving of time1 and for any one afflicted with 8writer's cramp0 the gain must be enormous4 ,we need not insist upon the advantages the adaptation of the apparatus would confer upon editors and readers of ,,mss4 too often badly written1 and to compositors the invention is a great boon4 ,finally1 the working of the machine could be entrusted to the blind1 and by teaching them the form of letters which could be raised upon the key-board1 those so sadly afflicted could write with facility4 ,some methods for teaching the blind to manipulate and to read from the impressions of the hammers on the paper have already been tried with success4 ,the ,electric ,pen1 an invention of the fertile brain of ,mr4 ,edison1 is shown in fig4 #bei4 ,the 8writing0 consists of a series of little holes close together1 made by a fine steel point like a put-crayon4 ,this point is thrust in and out with great rapidity1 and passes quickly over the paper4 ,if the characters cannot be formed so quickly as with an ordinary pen1 the writing is very distinct4 ,the alternative movement is given to the pen by an electric motor at once simple and ingenious1 which is placed on the top of the penholder4 ,the general appearance of the apparatus will be understood from the cut on next page4 ,the point is the termination of a wire which traverses the penholder1 and the upper extremity of which catches on the motor by an eccentric4 ,this eccentric has three teeth or cogs1 and it makes sixty revolutions a second1 thus producing one hundred and eighty beats in that time4 ,the axle carries a plate of soft iron1 which acts like the armature of an electro-magnet1 before which it turns with great rapidity1 the current being interrupted twice in every revolution by the commutator4 ,the current which moves this little apparatus is furnished by a pile of two elements in bichromate of potash1 according to ,mr4 ,edison's arrangement1 which is considered very successful4 ,carbon and zinc are employed1 and when ready for action the battery assumes the appearance of the cells in the illustration4 ,when the operator wishes to discontinue writing1 he simply raises the stem which has the electrodes attached to it1 and the elements are thus preserved for a future time4 ,under these circumstances the battery could be made to last several days without any renewal of the liquid1 and the plates will last for weeks4 ,thus a very simple arrangement is at our disposal4 ,let us see what use can be made of it4 ,illustration3 ,fig4 #bei4--;,edison's ,electric ,pen4 ,when we use the electric pen we obtain a great number of small holes close to each other4 ,such hand-writing is not easy to decipher by mere inspection like ordinary writing4 ,by holding it up to the light it is more easy to read1 but in both instances reading is not easy1 nor does it come by nature as ,dogberry declares4 ,but if we consider the paper as a 8negative10 we may obtain a number of positive proofs or copies of the writing4 ,to obtain these successfully we must use a press1 as shown in the accompanying illustration 7fig4 #bfj74 ,the writing1 or negative1 is placed upon the cover to the left1 where it is firmly fastened4 ,upon the body of the press a sheet of white paper is placed1 and when the lid is shut down the negative comes in contact with the paper4 ,by means of a roller1 represented in the box1 the writing is blackened1--the ink penetrates into all the holes which are upon the paper1--and after the manner of a stencil plate the impression will be found upon the paper when the cover is removed4 ,the writing will have a curious effect1 but practice will speedily remove all deficiencies4 ,the same negative will serve for a great many impressions1 quite a thousand having been taken from one4 ,by people accustomed to such work as many as six proofs a minute may be obtained4 ,of course a little practice will be necessary in this1 as in every other case1 before a correct or rapid result can be obtained1 but there is no difficulty in the practice4 ,there are two or three other applications of electricity which we must refer to2 such as the electric stamp1 of which we give an illustration1 and a curious method of stopping a horse by electricity4 ,the electric stamp might be very advantageously employed in our post offices to obliterate the 8,queen's ,head40 ,the description1 with illustration of this apparatus1 is annexed4 7,see fig4 #bfa47 ,illustration3 ,fig4 #bfj4--;,duplicating press4 ,at the lower end of the apparatus is a thin platinum wire1 so arranged as to form either a design or an initial2 by this the postage stamp can be defaced4 ,the stamp being put in communication with the pile1 the circuit is closed by the pressure of the finger1 as shown in the illustration4 ,the platinum grows heated and carbonises the paper1 and thus proves itself an ineffaceable stamp4 ,this apparatus may easily be used1 not only by the post office authorities1 but by every one who is obliged to deface a certain number of stamps every day1 and wishes to do so rapidly and without possibility of error4 ,an ingenious1 if scarcely necessary arrangement for conquering restive horses1 and frightening them into submission1 is shown in the illustration 7fig4 #bfb74 ,many means have been tried to stop or conquer a restive horse1 but the most efficacious has been designed by ,m4 ,defoy2 and the director of the ,paris ,general ,omnibus ,company has experimented successfully1 as we are informed1 with the arrangement we are about to describe4 ,a small magneto-electric machine is contained in a box beside the driver1 within easy and convenient reach of his hand4 ,the reins contain a wire1 one end of which terminates in the horse's bit1 and the other in the electro-magnetic apparatus4 ,when the electro-magnet is put in action an electric current is generated1 which gives the horse a shock in the mouth1 and so astonishes him that he suddenly stops in his course4 ,if the operator have the humanity and good sense to unite kindness to the abrupt application of the electricity1--which in our opinion should be only used as a last resource1--no doubt some excellent results may be obtained even with vicious animals4 ,illustration3 ,fig4 #bfa4--,the electric stamp4 ,m4 ,bella1 the ,director of the ,omnibus ,company1 has reported that the apparatus was tried in his presence and found very successful1 and quite easy of application2 and that even the most unruly animals have been subjected by it4 ,on one occasion a most restive animal was thus treated on the way to the forge4 ,he had a tremendous objection to be shod1 and made no secret of his dislike4 ,but a gentle application of the electric current put quite an opposite complexion upon the matter1 and after a few minutes the animal permitted himself to be patted and caressed1 and even allowed the smith to feel his legs and inspect his feet without making any objection whatever4 ,his shoes were taken off1 and the horse was re-shod without any of the dangerous demonstrations hitherto indulged in by the animal4 ,we may quote another instance of the efficacy of this method1 which is reported from ,paris by ,m4 ,camille4 ,illustration3 ,fig4 #bfb4--;,electric apparatus for checking vicious horses4 8,many experiments have been made upon horses which had been most difficult to shoe1 and in each case we have succeeded when the electric apparatus has been put in requisition4 ,one horse1 in particular1 nothing could subdue4 ,he kicked and bit and jumped about in such a manner as to render all approach impossible4 ,we had recourse at length to ,m4 ,defoy's apparatus1 and after the first application1 and without any great difficulty1 we were able to raise the animal's feet2 but after a second lesson we were permitted to shoe him without his offering the slightest resistance4 ,he was completely subdued40 ,m4 ,defoy recently made the experiment with a very dangerous animal1 which he stopped instantaneously in full gallop 7see fig4 #bfb74 ,it may be remarked that the application of the current is not sufficiently strong to stop the horse too suddenly4 ,it merely causes a very unpleasant sensation--he is not stupefied nor galvanized by the electricity4 ,the narrator has felt the shock applied without inconvenience1 and the conclusion arrived at is1 that this method of employing electricity is far superior to the violent and inhuman treatment so often employed to break horses1 which renders them subsequently sulky and vindictive4 ,m4 ,defoy has completed an electric bit and an electric stick quite as ingenious as the electric rein4 ,the modus operandi is simple and effective1 the wires being insulated by leather1 and terminating at the extremities of the stick4 ,the current is induced1 as before1 by a small magneto-electric machine4 ,illustration3 ,electric ,time ,ball4 ,,footnotes3 #ae ,encly4 ,metrop4 #af 8,treatise on ,electricity and ,magnetism40 #ag ,sabine3 8,the ,electric ,telegraph40 ,,chapter ,,xxi4 ,,magnetism4 ,,the ,,loadstone--,,magnetic ,,curves--,,the ,,magnetic ,,needle--,,the ,,mariner',s ,,compass--,,magneto-,,electricity4 ,we have already mentioned some of the properties of the loadstone or magnet2 but as we are now about to enter more fully into the considerations of its attributes and of the compass1 etc41 we will add some further interesting particulars4 ,ancient writers 7,pliny1 ,homer1 and ,aristotle7 mentioned the existence of the magnet1 and ,humboldt refers to the knowledge of it possessed by the ancients4 ,pliny says 8the magnet-stone is found in ,cantabria10 and we have heard of the loadstones that are supposed to support ,mahomet's coffin at ,medina4 ,the origin of this fable was 7probably7 owing to the order given by ,ptolemy to his architect1 ,dinochares4 ,ptolemy wished the roof of a temple at ,alexandria to be roofed with the magnet-stone1 so that the own image of his sister1 ,arsinoe1 should remain suspended therein4 ,but the death of the king and his architect prevented the project from being carried out4 ,the name 8magnet0 is said to have been derived from a shepherd named ,,magnes1 who1 when tending his flock on ,mount ,ida1 found that his iron crook was attracted to a certain stone2 and six hundred years before the ,christian era ,thales wrote respecting amber and the magnet2 and because they attracted various substances1 he supposed they possessed life and power4 ,they were the germs of the science now so developed in their applications1 and whose full powers we are scarcely yet acquainted with4 ,we may remark that other bodies besides iron and steel are capable of magnetization2 nickel and cobalt have the like property4 ,magnetism1 properly so called1 treats of certain bodies known as ,,magnets1 describes the properties they possess1 and the influence of magnetic force upon other substances4 ,electricity and magnetism are always associated1 but practically the force is the same1 electricity being the current or motive power1 so to speak2 and it is to ,faraday that the world is indebted for the discovery of magneto-electricity4 ,epinus' theory of magnetism was that all bodies possessed a substance he termed magnetic fluid1 the particles of which repelled each other4 ,but while supposed to repel each other1 they attracted particles in other bodies4 ,thus they attracted iron4 ,coulomb asserted that there were two fluids--a north and south fluid4 ,ampre's theory was that magnetic bodies are made up of molecules1 round which currents are always circulating in all directions when non-magnetized1 but when magnetized the currents all flow in the same direction4 ,the space through which a magnet diffuses its influence was called by ,faraday the ,magnetic ,field4 ,the lines of magnetic force will be understood from the accompanying illustration 7fig4 #bfc74 ,if we cover a magnet with a paper and scatter iron filings over it1 we shall see the manner in which the filings arrange themselves4 ,they radiate in curves from the poles of the magnet1 and are dependent upon its form4 ,if it be a straight bar magnet1 evenly magnetized1 they will turn inward in oval curves4 ,illustration3 ,fig4 #bfc4--,lines of magnetic force4 ,illustration3 ,fig4 #bfd4--,magnetization4 ,the manner of magnetization has already been mentioned1 but here we will give further illustrations of the method of magnetization4 ,four magnets are used1 two being placed with their opposite poles apart1 and upon them is placed the bar of which a magnet is to be made4 ,two other magnets separated by a piece of wood are then brought near1 and subsequently drawn from the centre to the ends of the bar4 ,this is the separated touch system2 the double touch of ,mitchell is completed by moving the upper two magnets from end to end backwards and forwards1 and finally lifting them away from the centre4 ,a magnet1 then1 is a bar of steel endowed with certain properties1 such as attracting iron1 etc42 and electro-magnetism is the term applied to the production of magnetism by means of electricity1 the medium being the electro-magnet4 ,to understand the science it will be necessary to mention ,ampre's theory of magnetism4 ,it was rsted who observed that when a magnet is placed within reach of an electric current and free to move1 it sets itself at right angles to the direction of the current2 and ,ampre defined the law already referred to when treating of the electric current1--viz41 8that if a person be imagined as placed in the wire so that the current shall pass through him from feet to head1 if he turn his face toward the magnetic needle the north pole will always be deflected to his left-hand side40 ,when the current is passed above the needle from south to north poles1 the deflection is to the west2 when from north to south the deflection is east4 ,when the current is below the needle the contrary is the case4 ,ampre decided that currents circulating in the same direction attracted each other1 and when running in opposite ways they repelled each other4 ,he supposed currents to circulate within all magnetic substances1 and then--that is1 when the body is magnetized--these currents flow in planes parallel to each other1 and the material which offers the least resistance to the circulation of these currents becomes the most magnetic4 ,the earth being supposed to be an immense magnet has currents circulating through it in a direction from east to west2 and having the property or power of turning a magnetized bar in a direction similar to that in which the bar would be turned by a magnet1 the earth is considered a magnetic mass4 ,this influence is due to what is called 8terrestrial magnetism40 ,if we suspend a bar by a thread it will point in no particular direction1 but may be turned towards any side we please4 ,but when once the needle is magnetized it will point north and south2 or1 as we say 7but not correctly71 the north pole of the magnet points to the north of the globe4 ,it is really the south pole that points to the north1 and the north pole of the magnet points south1 as can be proved by suspending the bar over another magnetized bar4 ,so if the earth be considered a magnet our ,english terms are inconsistent with our theories4 ,continental writers are more correct4 ,the line of the magnetic needle's direction1 which differs in different places1 is called the magnetic meridian1 and the amount of its divergence from the astronomical meridian is termed its declination or variation4 ,when the amount of this variation is known it is allowed for1 and the needle can be considered as pointing due north and south4 ,but the needle does not assume a position perfectly parallel to the horizon4 ,it dips down in different hemispheres4 ,as we approach the north pole the dip or inclination will become greater1 and the same effect is observable at the south pole4 ,again1 there are certain places on the earth where the attraction is so evenly balanced that the needle is perfectly horizontal4 ,the line uniting these places is the magnetic equator4 ,this does not coincide with the earth's equator any more than the magnetic poles coincide with the geographical poles of the earth4 ,the declination of the needle varies from the meridian of ,greenwich at different times4 ,if we travel to the west the variation increases westerly1 and is greatest in the ,atlantic4 ,it then decreases2 the needle points due north in ,north ,america4 ,going still forward the variation becomes easterly1 increases1 and decreases to nothing in ,eastern ,russia4 ,thence the variations are westerly4 ,columbus discovered the variation of the compass needle in ,september #adic4 ,in places where the needle is due north and south the lines drawn through them are termed lines of no variation4 ,the variation1 however1 is not always the same in the same place4 ,in the year #aehj1 in ,london1 for instance1 the variation was #aa #aa ,e4 ,a little more than one hundred years later ,london was on the line of no variation1 and now the tendency is westerly4 ,on the other hand1 there are places where there is no deviation1 and ,sir ,john ,herschell says that ,west ,india property has been saved from litigation in consequence of the invariability of magnetic declination there1 for all surveys were made by the compass4 ,lines of equal variation are called isogonial2 those of equal dip or inclination1 isoclinical2 and those of equal intensity1 isodynamical4 ,as we have said1 the magnetic elements are not always the same1 and the variations of the compass are daily and annually observed with certain instruments4 ,what are termed secular variations take place at long intervals1 as the following table will show3-- ,in #aegf the angle of declination in ,england was #aa #ae ,east4 #afbb 0 0 #f #ab 0 #affj 0 0 #j 0 0 #agcj 0 0 #ac ,west4 #agfj 0 0 #ai #cj 0 #ahjj 0 0 #bd #cf 0 #ahah 0 0 #bd #da 0 #ahej 0 0 #bb #bi 0 #ahgj 0 0 #ai #ee 0 #ahgc 0 0 #ai #eh 0 #ahgi 0 0 #ai #g 0 ,in the year #ahah therefore the maximum declination was reached in ,london4 ,in ,paris the maximum was arrived at in #ahad1 and was #bb #cd4 ,the rate of decrease is about #h a year1 but varies in different periods1 as may be seen4 ,the discovery of the fact that an annual variation took place in the angle of declination1 is attributable to ,cassini1 and the diurnal variation was discovered by ,graham in #agbb4 ,from #h o'clock in the morning1 when the needle is pointing a little to the east of its 8mean position10 it turns towards the west until #a p4m4 ,it then returns towards the east again1 and passing westerly again between midnight and three o'clock a4m41 settles down till eight a4m41 when it begins afresh4 ,this variation does not apply to all places4 ,magnetic inclination is besides subject to changes4 ,there are also variations of magnetic force which occur at very irregular periods1 and cannot be said to follow any laws4 ,these disturbances are called ,magnetic ,storms1 of which the ,aurora ,borealis is one result4 ,professor ,faraday in his memorable experiments divided a long list of different substances into para-magnetic and dia-magnetic bodies4 ,he classed them under these two heads1 according as they took up a certain position parallel or perpendicular to the axial or equatorial line4 ,this definition of 8dia-magnetic0 was 8a body through which the lines of magnetic force are passing1 and which does not by their action assume the usual magnetic state of iron or loadstone40 ,he concluded that all bodies were magnetic1 and by suspending a great number of various substances he found they placed themselves axially1--that is1 lying between the poles of the magnet1 or equatorially1--viz41 at right angles to that line4 ,if the magnets be suspended at each side the same bodies will assume a position with their longest diameters between the poles1 while others will be repelled by the magnets even if the poles be reversed4 ,so those bodies which are attracted and lie in the axial line are termed para-magnetic2 those repelled into the equatorial line are termed dia-magnetic4 ,in the 8,proceedings of the ,royal ,society for #ahdf10 ,faraday's account of the various experiments can be studied in detail4 ,we can only give a brief resum of them here2 and he showed that the motions displayed by dia-magnetic bodies in a magnetic field are all reducible to one simple law--viz41 that the particles of the dia-magnetic tend to move into the positions of the weakest magnetic force4 ,he experimented upon a large number of bodies and gases2 he tested crystals1 metals1 liquids1 and solids1 and proved in whatever state a body might be in the effect was the same2 whether simple or compound1 it made no difference4 ,of course in a compound the preponderance of the dia-magnetic or para-magnetic property would influence the result1 and the medium in which the body operated on was placed1 was a condition in the experiment4 ,he proved that if a body be suspended in a medium or surrounded by a medium whose power either way is stronger than the body1 that body is para-magnetic or dia-magnetic1 according as it is surrounded by a medium whose power is weaker or stronger than the body itself4 ,the arrangement of the bodies is as follows1 from the para-magnetic to the dia-magnetic1 bismuth being the most dia-magnetic of all3-- ,,para-,,magnetic ,,metals4 ,iron4 ,nickel4 ,cobalt4 ,manganese4 ,chromium4 ,cerium4 ,titanium4 ,palladium4 ,platinum4 ,osmium4 ,,dia-,,magnetic4 ,bismuth4 ,antimony4 ,zinc4 ,tin4 ,cadmium4 ,sodium4 ,mercury4 ,lead4 ,silver4 ,copper4 ,gold4 ,arsenic4 ,uranium4 ,rhodium4 ,iridium1 etc4 ,common air was also discovered to have a magnetic action1 and hot air is more dia-magnetic than cold4 ,oxygen is as para-magnetic in the air as iron is on the earth1 and this1 it was considered1 may give rise to magnetic storms1 and account for the declination of the needle4 ,we may now proceed to consider the ,mariner's ,compass4 ,the compass1 or the mariner's compass1 is so common that it is scarcely necessary to give a long description of it4 ,its history is unknown4 ,the ,chinese seem to have been aware of its usefulness long before the western nations adopted it4 ,it was about the time of the ,crusades that it was brought into western prominence1 but was not generally known till the thirteenth century4 ,chinese writings ascribe to the compass a great antiquity2 they maintain that it was discovered two thousand five hundred years before the ,christian ,era1 and used for travelling on land4 ,but1 according to other accounts1 it was not used at sea till the year #cjj ,a4,d4 ,the ,chinese put the south first when speaking of the points of the compass1 and in the ,chinese empire and ,thibet west goes likewise before east4 ,so the imperial edifices in ,china face the south1 and the needle1 in their expression1 points south and north--not as we say1 north and south4 ,the antiquity of the compass may be inferred from the recorded fact in ,chinese chronicles1 written in the second century before the ,christian ,era1 that nine hundred years previously to the date of the chronicle the ,emperor gave magnetic cars to certain ambassadors to guide them home in safety4 ,these cars were fitted with a magnetic needle which communicated with a figure4 ,its outstretched hand and finger followed the compass-direction1 and pointed out the way4 ,the ,chinese subsequently 7in the twelfth century7 suspended the needle by a thread1 and it is said their philosophers at that time noticed the variation of the needle4 ,but ,columbus first1 in #adib1 and ,cabot1 in #aedj1 certainly remarked it in ,europe4 ,it is to ,marco ,polo that we are indebted for the direct introduction of the needle into ,europe1 although it probably had been in use in the ,levant previously1 for we have seen a quotation by an ,arab writer1 who1 in #abdb1 described the needle as being used at that time on his voyage from ,tripoli in ,syria to ,alexandria1 two years previously4 ,friar ,bacon possessed a loadstone1 and there are many instances in which it is referred to in ancient writings4 ,the inventor of the compass we cannot trace1 but no doubt exists as to its being of ,chinese origin4 ,the ordinary compass is shown in the illustration herewith 7fig4 #bfe74 ,it consists of a magnetized needle1 suspended freely1 and fixed to a circular card1 which is divided and subdivided into thirty-two points1 as in the cut4 ,this compass is suspended upon gimbals to keep it in an upright position when the vessel rolls or plunges4 ,the gimbals are concentric rings1 the compass being fastened to the inner one1 and keeps its position in all weathers4 ,it is then enclosed in the binnacle1 a glass receptacle4 ,the card moves with the needle which points north4 ,there is a dark line 7lubber line7 which indicates the ship's course1 and when sailing the steersman must keep that line opposite the compass direction-point which indicates the course4 ,at night a lamp is lighted in the binnacle1 and the card being transparent and the points opaque they are easily seen4 ,the magnetism of iron ships has a tendency to disturb the needle1 and many suggestions have been made and discussed with a view to obviate this4 ,to put the compass at the mast-head was one1 to surround the compass with 8counter-irritants0 another4 ,but the usual way is to 8swing the ship10 and so adjust the compass4 ,swinging the ship means turning her round point by point1 and marking the deflection of the needle with reference to a certain object4 ,the amount of deflection at each point is read and noted1 and subsequently taken into consideration when sailing4 ,the ,azimuth ,compass is a mariner's compass fitted with brass uprights slit through the centre1 through which the heavenly bodies may be seen4 ,these are the sights4 ,the card is divided into degrees and quarters4 ,a fine wire is fixed upon one of the sights1 and in the other slit is a prism to reflect the divisions of the card to the eye4 ,the object--the azimuth distance of which it is desirable to know--is looked at through the slit1 and bisected by the wire4 ,the divisions of the scale are at the same time reflected1 and the number read gives the azimuth distance required4 ,illustration3 ,fig4 #bfe4--;,compass4 ,the compass has led us away slightly from our consideration of the electro-magnet1 but we will now examine it and its effects as briefly as possible4 ,an electro-magnet is formed by wrapping a copper wire round a piece of soft iron shaped like a horse-shoe2 the wire should be insulated with silk4 ,if the wire be wound round the iron in the same direction1 and a current be merely sent through the coil1 it will be found that the horse-shoe iron is highly magnetic1 but if the current be stopped the power is lost4 ,such magnets will carry weights much heavier than themselves1 and by careful consideration of certain laws1 and with reference to the number of coils and the strength of the current1 these magnets will sustain a weight some thousands of times greater than their own weight4 ,illustration3 ,fig4 #bff4--;,electro-,magnet4 ,if we cover a non-magnetic piece of iron with a wire coil1 and taking a magnet turn it rapidly beneath the wire-bound iron1 so that the magnetic poles approach each other alternately1 an electrical current will be generated in the wire4 ,the electro-magnetic machine is thus made2 but although strong currents may be generated as a source of motive power it is a failure4 ,to ,faraday our knowledge of magneto-electricity is due4 8,he knew0 7says ,professor ,tyndall in his interesting work1 8,faraday as a ,discoverer07 8that under ordinary circumstances the presence of an electrified body was sufficient to excite by induction an unelectrified body4 ,he knew that the wire which carried an electric current was an electrified body1 and still all attempts had failed to make it excite in other wires a state similar to its own40 ,but while he was making his experiments on the induction of electric currents he noticed that at the time the current was passing from the battery through the coils of wire that no motion was perceptible in the galvanometer4 ,but when the circuit was opened1 and when it was closed1 there was a slight motion of the needle in the galvanometer1 but in different directions4 ,after consideration the philosopher came to the conclusion 8that a battery current through one wire induced a similar current through the other1 but for an instant only40 rsted had already demonstrated that all magnetic effects were attributable to the attraction and repulsion of electric currents2 and founding his views upon the theory of ,ampre1 ,faraday came to the conclusion that electricity could be produced from magnetism1 or that the electric current could be obtained from magnets4 ,this he succeeded in doing4 ,by inserting a steel magnet about half its length into a coil of wire1 ,faraday induced a current to pass through the wire in two directions4 ,thus he proceeded to solve all the mysteries of magneto-electricity1 and stated that to produce currents it was only necessary to 8cut appropriately the lines of magnetic force40 ,the application of the magnet to the machines for electric lighting will be shown further on4 ,very powerful currents are obtained by the induction coil2 but the currents would not be of practical service were it not for the apparatus called a ,commutator1 or key1 which reverses the connection of the bobbins1 and turns the current at every half revolution4 ,just as if a current were being sent across and back over a table1 and when the current has reached the end1 an instantaneous wheel round1 or pivoting of the table1 sends the current on1 in continuation 7but on the table all the time71 because of the sudden change of its position4 ,the back rush being on the table1 the movement of the latter really makes the line continuous1 and by quickly breaking and reversing the current in the commutator1 the effect is gained in the machine4 ,illustration3 ,electro-magnets and bobbin1 etc4 7,clarke's machine7 ,,chapter ,,xxii4 ,,sundry ,,electrical ,,appliances--,,mr4 ,,edison',s ,,inventions--,,the ,,electric ,,light--,,the ,,gyroscope--,a ,,new ,,electrophorus--,,electric ,,toys4 ,,the ,,electro-,,motograph--although perhaps even yet scarcely developed--has already proved a very useful invention4 ,the idea of it first occurred to ,mr4 ,edison in #ahgc1 when he was prosecuting some researches in chemical telegraphy4 8,one day10 says ,mr4 ,fox1 in his account of the invention1 8as he sat pondering over his work1 he happened to take in hand the metallic point through which1 as it rested upon the paper1 the current was wont to pass4 ,when again he closed the circuit to let the current through the paper1 he held the metallic point loosely1 and unintentionally allowed it to rest upon the paper4 ,every time he moved the metallic strip on the paper the latter became wonderfully smooth4 ,edison was determined to find the reason of this1 and he decided that the electricity very much lessened the friction of the metal on the paper4 ,he made many experiments1 and brought the subject before the ,royal ,society in #ahgd1 but nothing came of the idea till #ahgf1 when ,edison was perfecting his musical telephone4 8,the new appliance is1 in fact1 the same invention revived and now perfected by the original inventor1 and brought to complete practical success under the title of the #8electro-motograph4' ,the action of the #8electro-motograph' depends on the fact1 discovered during former experiments1 and employed imperfectly in the musical telephone1 that the friction of moving bodies varies in greater or less degree with their electrical condition4 ,in the electro-motograph a cylinder made of prepared chalk1 and saturated with a strong solution of caustic alkali1 is set upon supports1 so that it can be turned upon its axis4 ,a strip of metal fastened to the mica diaphragm rests on the cylinder1 and is pressed so firmly by its spring upon the cylinder that when it is turned by means of the handle the friction of the strip on the cylinder tends to pull the diaphragm out of shape1 causing it to bulge inward as long as the cylinder is in motion4 ,if now1 while this motion of the cylinder is maintained1 an electric current passes through the strip of metal1 and then through the chalk cylinder to earth1 the amount of this friction is varied or it is destroyed altogether1 and the strip slides freely on the cylinder4 ,this was the basis of the former invention4 ,the release from friction by a change in electric condition in the first instrument failed simply from ignorance of some slight matters of detail1 that in the electro-motograph are corrected and made practical4 ,in the musical telephone the releasing of the frictional resistance by electric action caused the sounding-board of a guitar to vibrate1 and thus set up sonorous vibrations4 ,in the electro-motograph the mica disc takes the place of the guitar1 and1 by the improved construction of the apparatus1 intricate and complex vibrations1 such as are produced in speaking1 are reproduced in their original or even in greater volume4 ,when the apparatus is at rest the diaphragm is motionless1 and electric currents shot through the apparatus produce no effect4 ,in the same manner the mere turning of the cylinder without electric action produces no effect1 except to pull the diaphragm slightly out of shape4 ,if while the cylinder is being turned an electric impulse arrives1 the pull on the diaphragm1 caused by the friction of the strip on the cylinder1 is more or less released1 and the diaphragm is free to vibrate or spring back into its original condition4 ,if now1 the electric impulses follow one another in regular order in correspondence with the sonorous vibrations imparted to the transmitting telephone1 the alternate slipping and catching of the metal strip on the cylinder will follow in the same order1 and thus the diaphragm will be made to vibrate in unison with the original vibrations1 and thus reproduce the original words4 ,as the mica disc is much larger than the disc of the transmitting instrument1 the amplitude of its swing may be much greater1 and consequently it will repeat the words with greater power4 ,the electro-motograph is practically an apparatus for transforming electric action received from a distance into mechanical work4 ,the amount of electric action has nothing to do with the amount of the mechanical work performed1 because the movement of the cylinder is controlled by power independently of the electric action1 the electricity merely releasing this power by destroying the friction in greater or less degree4 ,the electric action set up by the sonorous vibrations at the transmitting end of the line may be very slight1 while the mechanical action at the distant end may be powerful1 and in this manner the amplitude of the vibrations may be increased to an indefinite extent1 and a whisper may reappear as a loud shout4 8,the electro-motograph is not only a solution of the telephone1 making it capable of sounds of every quality and pitch and in greatly increased volume1 but by this conversion of electrical action into mechanical work at a distance makes it possible to unite the telephone and phonograph4 ,telephonic messages by the electro-motograph may be impressed upon a self-acting 7clock-work7 phonograph1 the same current starting and stopping the phonograph after the manner of the stock-reporting machines1 and afterward the phonograph may be made to repeat the message impressed upon it40 ,the above extract1 which explains the principle fully1 has been taken from a long article on the subject which formerly appeared in ,scribner's ,magazine4 ,the uses to which the electro-motograph may be applied are various4 ,it can produce mechanical motion even at a distance1 and is useful to lessen friction by machinery2 and in this way its service to railways and other locomotive systems may be estimated4 ,it is a great help to telegraphy by increasing the speed of transmission1 and can ascertain the beatings of the heart of the apparently dead4 ,it amplifies sound in a much greater degree than the microphone1 by which even a fly can be heard moving4 ,in fact1 the limit of the usefulness of this wonderful machine has not been reached4 ,another very ingenious apparatus has been developed by ,professor ,bell4 ,this is for the purpose of ascertaining the position of bullets in the body4 ,the following is condensed from the ,times3-- 8,two conductors are used1 and the ball completes the circuit4 ,professor ,bell inserts a fine needle in the suspected region4 ,it is connected by wire with one of the binding screws of a telephone1 which the surgeon holds to his ear2 the other binding screw being connected with a metallic mass applied to the skin4 ,when the needle point touches the ball1 an electric couple is formed1 and the current generates the sound in the telephone4 ,the surgeon may then use his knife with confidence1 guided by the needle4 ,he may make several insertions of the needle if necessary without danger1 and any pain may be obviated by etherization4 ,this simple method 7which should prove useful on the field of battle7 was tried with success with a lead ball introduced into a piece of beef4 ,contact of the needle with bone had no effect1 but a very distinct sound was heard each time the ball was reached4 ,a modification consists in inserting a vibrator in the circuit2 this gives a musical note in the telephone at each contact of ball and needle4 ,again1 if the circuit include a battery1 the telephone sounds may be heard by several persons at once4 ,a sound is heard1 in this case1 whenever the needle enters the skin2 but1 on reaching the ball1 it is much intensified1 owing to lessened resistance4 ,a galvanometer may be used in place of the telephone40 ,mr4 ,c4 ,vernon ,boys has exhibited and described a very ingenious new integrating machine of his invention1 and its application as a measurer of the electric energy in the circuit of an electric lamp or a dynamo-electric motor4 ,mr4 ,boys' mechanical integrator belongs to the class termed tangent machines1 and consists essentially of a small disc or wheel running along the surface of a drum or cylinder4 ,when the wheel runs straight along the drum parallel to its axis there is no rotation of the latter1 but when the wheel is inclined to the axis the drum rotates1 and the integral is represented by the amount of rotation4 ,continuous action is secured in giving the drum a reciprocating motion along its axis1 so that when the wheel has travelled to one end of the cylinder it can travel back again4 ,the new integrator is especially adapted for measuring forces which are either delicate or variable4 ,it is applied by causing the varying force to be measured to vary in a corresponding manner the inclination of the wheel to the axis of the rotating cylinder4 ,in this way it can be used to find the work done by a fluid pressure reciprocating engine1 or the energy transmitted by a shaft or belt from one part of a factory to another4 ,by making the wheel very small and light1 the strength of an electric current may be continuously measured1 if the disc is inclined by means of the needle of a galvanometer in circuit4 ,mr4 ,boys has constructed on the same principle an electric energy meter1 which integrates the product of the strength of current and the difference of potential between two points with respect to time4 ,in it the current is passed through a pair of concentric solenoids or coils of wire1 and in the annular space between these is hung a third solenoid1 the upper half of which is wound in the opposite direction to its lower half4 ,by the use of what ,mr4 ,boys calls 8induction traps0 of soft iron1 the magnetic force is confined to a small portion of the suspended solenoid1 and by this means the attracting force of the fixed solenoids upon it is independent of position4 ,the middle solenoid is hung from the end of a balance beam1 and its motion is retarded by a counterweight1 which admits of regulating the meter to give standard measure as a clock gives standard time4 ,the motion of the beam is caused to incline the integrating wheel1 and the rotation of the cylinder gives the energy expended in foot-pounds by means of an indicator or diagram1 as the case may be4 ,the object in giving an equal number of turns in opposite directions to the suspended solenoid is to render the instrument insensible to external magnetic forces4 ,we have1 in a former portion of this work1 explained the construction of the telephone and phonograph with other inventions to make sounds audible at a distance1 so we need not repeat the explanations here4 ,a brief reference to them will1 however1 be found in this chapter1 in which the electro-magnet and the methods of lighting by magneto-electric machines are treated of4 ,we will proceed to give some particulars concerning the electric light before considering the means by which it is produced1 as such an arrangement is more convenient4 ,the light is very easily produced by uniting and then separating the terminals of a strong battery4 ,the passage of the electric current induces intense heat and a most brilliant light4 ,but if this were continued the wires would melt1 and therefore some non-fusible substance is placed at the ends of the wires1 which will be at once a conductor and infusible4 ,now in gas-carbon 7the deposited substance found in gas retorts7 we have a substance suited to these conditions4 ,the carbon is heated to an intense brightness1 and particles of it are passed across the arc of flame almost in a state of fusion4 ,combustion does not actually take place1 because it has been proved that the wires will give out light under water1 and in the vacuum of an air-pump the light is even increased1 so that had the oxygen of the air any part in the production of the light it would not remain unaffected under these conditions4 ,the heat arising from this ,voltaic arc is intense1 and even platinum may be fused with the assistance of the gas carbon4 ,the carbon points are of course liable to be worn away1 and one side more than another4 ,the positive pole is generally more concave than the other1 for it sheds its particles in a greater degree1 and is the more intensely heated4 ,the electric light first appeared in public at the opera in ,paris in #ahcf1 to illustrate a sunrise1 but it was not till #ahdc that it was experimented upon in the open air4 ,we need not trace it farther at present1 for a full account of its origin1 rise1 and progress is published in a small shilling volume by ,messrs4 ,ward1 ,lock1 ,co4 ,we will proceed to the methods of bringing out the light4 ,illustration3 ,fig4 #bfg4--,the ,maxim light4 ,illustration3 ,fig4 #bfh4--,mechanism of ,maxim's lamp4 ,there are various lamps1 many of which required a regulator in consequence of the wearing away of the carbon points1 as already explained4 ,we append two illustrations of the ,maxim lamp1 the invention of ,hiram ,maxim1 of ,new ,york4 ,in both cuts the letters refer to the same portions4 ,in the first illustration 7fig4 #bfg71 ,a and ,b are the positive and negative carbon-holders respectively1 and the carbon points are controlled by an armature1 which is1 in its turn1 adjusted by the screw1 ,d4 ,when it happens that the magnetic force is reduced the spring acts and permits the points to approach again1 and the light is rekindled2 the carbons are then locked till required to move4 ,the second illustration 7fig4 #bfh7 shows a section of the lamp with the wheel arrangements for controlling the advance of the carbon points as they waste away4 ,illustration3 ,fig4 #bfi4--,wallace lamp ,illustration3 ,fig4 #bgj4--;,houston lamp4 ,in the 8,brush0 light1 which is in use in ,london1 and is fitted for large spaces1 the carbon points are held by a regulator side by side1 and they last eight hours without renewal4 ,the power is generated by an electro-dynamic engine4 ,we give illustrations of the lamps of ,wallace and ,houston 7figs4 #bfi1 #bgj74 ,the current is conveyed through b and the magnet1 m4 ,the armature1 a1 separates the electrodes1 and the weakened current is restored by b1 and the light continues4 ,the pillar1 p1 is hollow1 with a wire running through it4 ,the positive electrode is supported by ,j1 the negative by ,c2 ,v is a button which comes in contact with the lever1 ,t1 when the carbon points are exhausted1 and cuts the lamp out of the circuit by passing it direct through mercury cups4 ,the ,jablochkoff candle and chandelier are also represented 7figs4 #bga1 #bgb74 ,the candles consist of carbons connected at the top1 but otherwise insulated1 and fixed in a socket4 ,they do not last very long without renewal4 ,the exhibition at the ,crystal ,palace will be essentially an ,electric ,light ,exhibition1 and all the latest forms can be studied there4 ,the great attraction will doubtless be1 as at ,paris1 the varied and numerous inventions of ,mr4 ,edison4 ,the early career of that ,american 8magician0 is now tolerably well known2 his tremendous energy and application are fully appreciated4 ,with only a few months schooling all his life he has taken a foremost place in the scientific world4 ,in ten years he has invented the phonograph1 the electric pen1 a system of fast telegraphy1 the electro-motograph1 the telephone1 a tasimeter1 and other useful applications of electricity1 besides solving the problem of electric light for domestic purposes4 ,mr4 ,edison's electric light#ah requires something more than a passing notice1 and we will therefore endeavour to give a sketch of the general subject4 ,now that the electric light has been made available for domestic purposes1 and the very simple lamp 7consisting of an exhausted glass globe1 two platinum wires1 and a piece of charred paper7 can be obtained1 people will no doubt soon largely adopt electric lighting in their houses4 ,the light has found a success at the theatre1 in the streets1 and in the train2 there is no reason why it should not be adopted generally1 being more economical and more healthy than gas4 ,illustration3 ,fig4 #bga4 ,electric candle4 ,illustration3 ,fig4 #bgb4--;,chandelier4 ,if we sever an electric wire1 and bring the ends1 tipped with carbon1 into juxtaposition1 we obtain a brilliant light4 ,this is the ,voltaic arc we have already mentioned1 produced by the incandescence of finely-divided matter2 it was the first method of illuminating by electricity1 and was discovered by ,sir ,humphrey ,davy1 who obtained a very brilliant light1 but at great expense--about a guinea a minute6 ,but the ,daniell and ,grove batteries and generators1 and modern improvements in #ahfj1 brought the use of the electric light into prominence4 ,faraday lighted a lighthouse with its assistance4 ,but when the ,,gramme ,,generator was invented the needed impetus was applied4 ,the ,jablochkoff candles followed1 and now we have the electric light in full operation4 ,so far we have sketched the history of illumination by the ,voltaic arc1 and descriptions of the various apparatus will be found at the end of this chapter4 ,but the method of lighting with an incandescent solid was introduced in #ahde by ,starr and ,peabody1 who took out a patent for the use of platinum4 ,later on ,drs4 ,draper and ,despretz made experiments with platinum and carbon4 ,the latter gentleman sealed the carbon in an exhausted globe1 and then introduced nitrogen in place of the air4 ,but the method died out and was forgotten1 and in #ahgc a medal was actually given by the ,academy of ,st4 ,petersburg for the 8discovery0 to ,messrs4 ,sawyer and ,mann4 ,in #ahgh ,paris was lighted with the electric candles of ,jablochkoff4 ,this application of electricity stirred up our transatlantic cousins1 and ,mr4 ,edison was requested--backed up by many influential persons--to make the investigation whether the light could be produced for domestic purposes4 ,the celebrated electrician undertook the commission1 and certainly came unprejudiced to the encounter1 for he had not at that time even seen an electric light4 ,he perceived at once that 8permanence in the lamp and the subdivision of the light0 were the two desiderata4 ,he put the ,voltaic arc aside as unsuitable1 and addressed himself to the problem of obtaining the desired results from an incandescent solid4 ,the subdivision of the light is really an important point1 and a comparison between divided and undivided burners is in favour of the more diffused light in a number of burners4 ,this subdivision ,edison worked hard to secure1 and1 as it is said of him1 8,with a steadfast faith in the fulness of nature1 a profound conviction that if a new substance were demanded for the carrying out of some beneficial project1 that substance need only be sought for1 he set to work40 ,mr4 ,edison found difficulties in his way4 ,one was the apparent impossibility of illuminating by means of an incandescent solid1 for even platinum will melt at a heat too low for use4 ,but this apparent impossibility was overcome by the inventor's genius4 ,he1 after many trials1 found that if he raised the platinum to a white heat in a vacuum he would practically obtain a new metal which would sustain the required heat4 ,illustration3 ,fig4 #bgc4--;,edison's platinum lamp4 8,in making an electric lamp without a regulator10 says ,mr4 ,upton1 8two things are essential1--great resistance in the wire1 and a small radiating surface4 ,mr4 ,edison sought to combine these two essential conditions by using a considerable quantity of insulated platinum wire wound like thread on a spool40 ,this platinum1 as shown in the accompanying cut 7fig4 #bgc71 was suspended in a glass bulb in vacuo1 the air contained in it being expelled by electricity1 heating it1 and suddenly cooling the platinum1 and squeezing out the air by the process4 ,but1 after all1 the great difficulty of the inventor was to insulate his wires so perfectly that they would not meet and become a conductor4 ,for1 to perfect his lamp1 this non-conducting principle was a necessity1 otherwise the current would flow across instead of going all along the wires4 ,he had previously made many uses of carbon1 which we know is infusible4 ,he tried lampblack tar1 but it contained air1 and would not do4 ,thread answered his purpose1 but was too fragile and uneven in texture4 ,it suddenly occurred to him that paper--charred paper--cut into a thread-like form would satisfy all his conditions4 ,the problem was solved--the lamp was a fact4 ,but how can paper1 so easily burned1 answer8 ,we will endeavour to explain4 8,a piece of charred paper1 cut into horse-shoe shape1 so delicate that it looked like a fine wire firmly clamped to the two ends of the conducting and discharging wires1 so as to form part of the electric circuit1 proved to be the long-sought combination40 ,we will now explain the construction of this little lamp1 which is shown in the illustration 7fig4 #bgd7 one-half of its actual size4 ,the illuminating is equal to ten or twelve ordinary gas jets4 ,illustration3 ,fig4 #bgd4--;,edison's electric lamp4 ,the manner in which the paper is prepared is1 like many other very important inventions1 extremely simple1 and1 we may add1 almost costless4 ,cardboard will furnish us with the loops1 and these 8horseshoes0 are placed in layers in an iron box with tissue paper between each4 ,the box is then hermetically sealed1 and made red hot4 ,the carbonized paper remains till all the air has been got rid of1 and although it will burn freely to ashes in atmospheric air1 in the vacuum prepared for it it is never consumed4 ,that is the plain fact--the secret of the ,edison lamp4 ,a vacuum can now be produced almost perfect4 ,it is of course impossible to extract every tiny particle of air from the globes1 but by the ,sprengel pump1 in which mercury is employed1 excellent vacuums are obtained4 ,several very curious phenomena have been observed in these vacuums1 and the ,royal ,society has been engaged upon their consideration4 ,another advantage of the vacuum1 as applied by ,edison1 is that little or no heat is generated4 ,the electricity is all1 or very nearly all1 converted into light4 ,thus the glass globes remain almost unheated1 and are unbroken4 ,the electric current passes along the wire1 ,w1 and at a certain place marked ,b1 the copper is soldered to a platinum wire1 which enters at ,c1 and so by platinum clamps into the horse-shoe1 ,l4 ,the return wire is similarly arranged2 the carbon is enclosed in a glass bulb1 ,,gg1 and all the air is extracted by the pumps2 the end is then sealed up by melting it at ,f4 ,the world is now in possession of a lamp for household use1 and we are surprised that it is not more extensively adopted in ,england4 ,there are some ,swan lamps used in parts of the ,british ,museum1 and when we have explained the application of the light1 and the uses to which the motive power can be applied1 we shall1 we believe1 convince the most conservative gas bill advocate that ,edison's lamp is cheaper1 safer1 and far better in illuminating power than gas1 if the success of the electric lamp can be assured4 ,we need not dwell upon the construction of the 8pumping station10 for that is virtually what the magneto-electric generator is4 ,several of these stations can be established in various parts of the city1 and each station will supply a district with electricity4 ,the wires are laid in a tight box along the street1 beneath the footpath1 or other convenient position1 and we are informed that the frost rather improves their electrical condition4 ,here is one advantage over gas4 ,from the main wires smaller ones enter the houses1 and are carried through a 8meter0 containing a safety valve4 ,there are two wires--a distributing wire and a waste--coloured1 one red and the other green1 which communicate respectively with the main supply and return wires to the 8pumping station0 or generator4 ,the electricity is admitted between carbon points and flows round a magnet1 the armature of which is held above it by a spring4 ,if too much force be put on and any danger incurred1 the magnet will attract the armature1 and the current will cease4 ,a snap connected by a small wire will then be closed by the electricity1 and melting from the heat will cut off all the current4 ,in ordinary circumstances the electricity passes through regulators 7wire wound on spools7 and on to a copper plate1 8through a solution of copper salt40 ,thus for every unit of current a certain quantity of copper is deposited4 ,a certain standard amount represents five cubic feet1 and the bills1 based on the accumulation of copper1 are made out like gas bills4 ,when the lamp is required a small handle is turned1 and is instantly lighted2 the reverse motion cuts off the current4 8,by touching a knob in the bedroom the whole house can be simultaneously lighted up0 if desirable4 ,no matches are necessary1 as the lamps light themselves4 ,by adding a small electro-motor to the furniture of the house1 and turning a handle1 the sewing-machine can be worked by electricity1 or lathes turned2 and any business operations1 such as lifting by cranes1 etc41 can be easily carried on4 ,the ,swan electric lamps1 which1 with ,mr4 ,edison's1 were exhibited in ,paris1 and will be found at ,sydenham1 give about twelve candle-power light4 ,edison's lamps are made in two sizes1 and vary accordingly4 ,the ,swan lamps give a very soft light1 and are as easily manipulated as ,edison's4 ,the ,siemens system of lighting was also well seen in ,paris1 and the ,faure storage system enables our trains to be lighted instantaneously by simply turning a handle4 ,a full description of the ,faure battery was given in the ,times by ,sir ,william ,thomson1 and in his address to the ,british ,association at ,york in ,september last4 ,he pointed out that in the accumulators of ,m4 ,faure1--which can be seen at #ddf1 ,west ,strand1 ,london1--by means of a large battery it is quite easy to draw off electricity and to apply it as ,edison proposed to do1 in lighting our houses and do any little service4 ,the electricity thus stored would be always ready for use1 and would be supplied and paid for4 ,it can be applied to any purpose1 and locomotion by its means will ere long become more general4 ,in ,paris ,dr4 ,siemens exhibited his electric tramway4 ,this was an improvement upon the first ,berlin tramway1 for in it the horses frequently received shocks which they resented4 ,in the later application the current comes from the generator by metal rods carried above the heads of the passengers alongside the line4 ,little rollers upon these are united with an electric machine in the tram-car4 ,the current is sent along the wires1 and reconverted into mechanical energy in the second machine1 turns the wheels of the cars4 ,in this way1 as the car proceeds1 the rollers overhead or alongside the track are kept moving by the car1 and the connection is never broken4 ,but this is a digression4 ,the electric light as applied to lighthouses was also exhibited1 and any reader desirous to obtain full information upon the subject of lights and lighthouses will find it in a very pleasantly-written work by ,mr4 ,thomas ,stevenson1 in which the various systems of lighting by electricity and otherwise are fully recounted1 the conclusion being in favour of electricity1 which is employed and has been used for years in ,france and in some ,english beacons4 ,if its penetrative power can be finally established1--for some authorities maintain that the electric is more easily absorbed by fog than other light1--there is no doubt about its being universally adopted4 ,it is very interesting to watch the uses to which the electric light is being put4 ,the latest experiment has been made by an ,austrian1 ,doctor ,mikerliez4 ,almost incredible as it may seem1 the interior of the human stomach can now be illuminated by means of a wonderful little instrument called the ,gastroscope1 which is said to be actually in use and to have been favourably reported upon by the medical faculty of ,vienna4 ,there is at the end of a jointed flexible tube 7which can be passed down the gullet7 a miniature lamp1 far more marvellous and mysterious than that of ,aladdin1 in which a strip of platinum is fixed and connected with fine wires conducting the electricity from a small battery4 ,when contact is made1 and the 8light turned on10 the cavernous interior of the stomach is lit up4 ,still more extraordinary is the fact that the tube can be made to revolve1 and the light reflected from the walls of the stomach and directed to the eye of the observer4 ,there is necessarily a bend in the instrument1 so that the light has literally to turn a corner before it reaches the surgeon's eye2 here the inventor's skill and thorough knowledge of the laws of optics are brought into requisition4 ,the reflected rays of light fall upon a sort of window situated a little above the lantern1 and by means of prisms and a series of lenses1 the light is twisted and turned about until it arrives at the eye-piece4 ,no sensation of heat is to be feared1 the little lamp being kept constantly cool by a reservoir of water4 ,several contrivances have been invented within the last few years for examining the interior of the body1 but they are very costly2 the ,gastroscope is likely to render great service to medical science4 ,the term 8magneto-electric machine0 is given to a collection of parts of mechanism intended to create or gather together induced electric currents4 ,the invention of the magneto-electric machine was by no means a sudden inspiration1 but the gradual result of a series of experiments and discoveries1 the first of which1 dating from #ahbj1 may be said to be rsted's observation1 that a magnetised needle is deflected by the approach of an electric current as well as by that of a magnet1 clearly proving that magnetism and electricity have some relation to one another4 ,in the same year ,arago discovered that a coil of insulated wire wound round a core of soft iron1 converts it into a powerful magnet 7i4e41 an electro-magnet7 when a current passes through the coil4 ,it was in #ahcj1 however1 that our countryman ,faraday proved the creation of a current by the action of a magnet on a coil of wire1 and his experiment proved shortly as follows3--,if a coil of wire be wound on a hollow core1 and a permanent bar magnet be introduced into the hollow core1 whilst introducing it a current may be proved 7by a galvanometer71 to be induced in the coil flowing in a certain direction1 ,a ,b1 which ceases as soon as the magnet is at rest in the centre of coil4 ,on the withdrawal of the magnet a second current is induced flowing in the opposite direction1 ,b ,a4 ,therefore it is clear that if a magnet be incessantly approached to and withdrawn from a coil of wire a constant succession of currents will be produced1 and if a charged coil 7i4e41 a coil connected with the poles of a voltaic battery7 take the place of the magnet a precisely similar result will be obtained4 ,now it will have been noticed that two opposite currents are constantly being formed1 and as the object is to obtain a continuous flow of electricity in one given direction1 or1 in fact1 divert or reverse the current instantly on its formation to make it practically the same current1 for this purpose a commutator is used1 and as for most purposes a commutator is one of the essentials of a magneto-electric machine1 we will here give a description thereof4 7,see fig4 #bge47 ,the machine is composed of a cylinder1 consisting of two metallic conducting halves1 separated by a non-conducting layer4 ,whilst it is at rest the alternating currents1 from being connected with the halves by the current1 will pass to the two contact springs1 and thence through the circuit4 ,now if 7as is the case7 the current is constantly changing1 as has been noticed1 the inverse current will at the first change pass through the same channels1 but in another direction2 but if at the instant of the reversal of the current the cylinder be revolved1 the current flowing the reverse way will be guided through other channels respectively1 instead of the original channels1 and the direction of the current being changed at the same moment as the current itself1 the two inversions neutralize themselves1 and one constant current is produced4 ,in a magneto-electric machine the commutator revolves identically with the magnet or armature1 and the point at which sparks are being constantly produced is where the contact is being continually broken and made by the passage of the friction springs from over the non-conducting layer4 ,the first machine formed on the basis of ,faraday's experiments was ,pixii's4 ,it was composed of two uprights and a cross bar1 to which is attached1 hanging poles downwards1 an electro-magnet2 underneath this1 the poles upwards1 revolves a magnet4 ,the commutator is fixed on the same axle and revolves with the permanent magnet4 ,saxton1 and subsequently ,clarke1 made the obvious improvement of making the magnet less cumbrous and fixed1 and causing the bobbins of the electro-magnet to revolve before or rather beside its poles2 the commutator was fixed at the end of the axle on which the revolving bobbins 7or armature7 are fixed4 ,niaudat formed a compound ,clarke machine1 by setting two horse-shoe magnets a short distance apart4 ,the armature revolves between them1 and consists of twelve coils set between two plates2 the coils are set alternately and connected1--i4e41 the poles of the electro-magnets are set beside one another1--,n4 to ,s41 ,s4 to ,n41 and so on1 so that the ,n4 pole receding produces a current2 but the ,n4 pole receding makes the ,s4 pole approach1 and produces another current1 ,a ,b2 in fact1 a continuation of the same1 for the approach of a ,n4 pole naturally produces the same current as the recession of a ,s4 pole2 then as the ,s4 pole in turn recedes it produces an inverse current1 ,b ,a1 which is in turn kept up by the approach of the next ,n4 pole1 and so on4 ,each coil is attached to a radiating metal bar1 which conveys the current to be redirected to the commutator1 which is affixed to the axle of the revolving armature as in ,clarke's machine4 ,in #ahed ,siemens completed his machine1 the chief peculiarity of which was its cylindrical bobbin2 the core is grooved deeply1 parallel with its axis1 and the wire is wound on cylindrically and covered with plates of brass2 one end of the coil is fixed to the metal axis1 the other to an insulated ferule at the end of the axis1 where is also situate the commutator4 ,this armature revolves between the poles by which it is closely embraced4 ,one of the most celebrated of the magneto-electrical machines is that known as the 8,alliance10 invented by ,nollet1 and perfected by ,van ,malderen4 ,it is composed of four or six bronze discs1 revolving on an axle1 round the external circumference of each of which are set sixteen bobbins4 ,this rotating compound armature revolves between four to six sets of horse-shoe magnets1 which1 being fixed radially to the centre1 present in each set sixteen poles to the sixteen bobbins4 ,it will be readily understood that this immense quantity of poles and bobbins produces a highly concentrated current1 the ends of which proceed from the axle and an insulated ferule at its extremity4 ,illustration3 ,fig4 #bge4--,the ,wallace ,machine4 ,in #ahfi ,mr4 ,holmes perfected his machine1 which differs from all previous ones 7except ,pixii's71 in that the electro-magnets revolve in front of the coils instead of vice vers2 and besides magnetising his electro-magnets with part of the self-produced electricity1 his bobbins are so disposed as to be able to keep several independent lights going at once4 ,the ,wylde machine consists1 as it were1 of two ,siemens machines1 one on the top of the other1 the lower and larger of which is worked by an electro-magnet1 which is magnetised by the action of the upper or smaller one1 consisting in the ordinary way of a permanent magnet apparatus1 which is termed 8the exciting machine40 ,the longitudinal bobbin revolved between these permanent poles produces alternating currents1 which are commutated 7or redirected71 and pass to work the larger and lower electro-magnet1 which is composed of two large sheets of iron connected by a plate 7on which stands the exciter74 ,its poles are two masses of iron separated by a layer of copper1 and in this armature revolves the larger longitudinal bobbin4 ,this lower machine is called the generator4 ,both bobbins are simultaneously revolved1 and an intense current of electricity is thereby generated4 ,almost simultaneously with this one ,mr4 ,ladd invented his machine1 which is distinguished from all hitherto described by being composed of two parallel bar electro-magnets1 between the extremities of which are placed two ,siemens armatures1 one smaller than the other2 both being revolved1 the smaller excites the electro-magnets1 and the larger generates the electricity required4 ,the wire is wound round the magnets so that the ,n4 and ,s4 poles face each other at each end4 ,the chief advantage of the ,ladd machine is the conversion of dynamic force into electricity1 there always being just sufficient magnetism in an iron bar 7by induction from terrestrial magnetism and other causes7 to produce a very feeble current in the ,siemens bobbin1 and the bobbin taking it up and returning it to the electro-magnet1 and the electro-magnet at once giving it back to the bobbin1 the current gradually increases till the maximum is reached4 ,and when we take into consideration this modicum of utilisable terrestrial magnetism1 we may truly say in the words of ,m4 ,hippolyte ,fontaine1 8,the mind is lost in contemplation of the succession of discoveries completing one another1 and showing that with apparatus of small dimensions an infinite source of electricity could be produced if matter could withstand infinite velocities40 ,the ,lontin machine1 which supplied the current for the electric light which used to make night bright outside the ,gaiety1 is also composed of two parts1 one dividing1 the other generating the electricity produced4 ,the principle of the dividing machine is somewhat similar to the alliance1 excepting that a number of electro-magnets arranged radially round a core1 revolve close to a corresponding number of bobbins fixed inside an iron cylinder1 outside which is the collecting and dividing apparatus4 ,the ,maxim machine is constructed on the principle of sets of coils rotating between powerful electro-magnets4 ,the ,wallace machine was invented by the inventor of the ,wallace-,farmer lamp4 ,it consists of two horse-shoe electro-magnets placed side by side1 the opposing poles facing each other4 ,each magnet has a rotating armature of twenty-five bobbins1 on which the wire is wound quadruply1 and the current generated by these coils is conducted away1 passing through and exciting the electro-magnets1 thus utilizing the residual and terrestrial magnetism before mentioned in connection with the ,ladd machine2 otherwise it partakes of the nature of the ,niaudet machine4 ,illustration3 ,fig4 #bgf4--,the ,gramme ,machine4 ,we now come to what is perhaps the most perfect magneto-electric machine1 which was first constructed by ,m4 ,gramme1 a ,parisian1 in #ahgb1 and differs in principle and construction from all those hitherto noticed4 ,its essential characteristic is a soft iron ring1 round which is coiled one single continuous wire 7i4e41 the two ends are joined74 ,round the exterior surface of the wire coil a band is bared1 and on this bared part two friction springs act4 ,if the ring and coil be placed before the poles of a magnet1 the ring will have two poles1 ,s4 and ,n41 induced opposite the opposing poles ,n4 and ,s4 of the magnet2 and if the ring revolve the poles will remain stationary1 and as the coil revolves each coil of the wire will pass this induced pole1 and as naturally half the coil will be inducted with one current1 the other half 7acted on by the other pole7 will be charged with another or opposite current1 which two kinds of electricity are carried away by the friction springs before mentioned4 ,in the machine1 as actually constructed1 the soft iron ring is composed like the magnet or wire bundle of an induction coil1 and the coils are set upon it side by side4 ,inside the ring are radially set insulated pieces1 to each of which is attached the issuing end of one and the entering end of another bobbin2 these answer the same purpose as the denudation of the external layer of wire4 ,these pieces are bent so as to come out of the centre of the ring at right angles1 and lay side by side 7insulated7 round a small cylinder4 ,these1 as they revolve1 are touched by friction springs1 which draw off the electricity induced in the coils in one continuous current4 ,no sparks are produced at the contact of the friction springs1 and there is no tendency to become heated4 ,to obviate the inconvenience of the secondary or inverted current produced by the stopping of the machine1 the inventor has contrived a circuit breaker on the principle of the electro-magnet1 the magnets holding the circuit breaker in contact so long as the machine is working2 but the decrease of velocity lessening the attractive power of the magnet1 the circuit breaker opens by its own weight 7or a counter-weight71 and all danger of a reverse current is obviated4 ,experimental machines are manufactured by ,brquet ,cie 7,paris71 composed of ,jamin's magnets1 and turned with a handle1 and produce a force of eight ,bunsen cells4 ,a great revolution1 or rather the beginning of a new era in the history of electricity1 may be said to have commenced with the perfection of ,m4 ,faure's accumulators4 ,these are troughs containing eleven lead plates1 each coated with oxide of lead and wrapped in felt1 the fluid being dilute sulphuric acid4 ,the application of them to the electric light is one of their most valuable features2 at the dept in the ,strand1 where they may be seen at work1 there are thirty such elements1 each weighing about #ej lbs4 ,it takes a two-horse-power engine working an ,edison or ,gramme machine six to eight hours to charge them1 and when charged they will keep almost any number of lamps of sixteen-candle-power going some eight hours4 ,they are used on the ,brighton and ,south ,coast ,railway1 and seem peculiarly adapted to lighting by incandescence1 by ,swan1 or ,edison's lamp4 ,the elements fully charged may be carried any distance without losing their electric power4 ,and the stored force may be used for charging the accumulators themselves afresh from the machine4 ,these accumulators may be seen any day at #ddf1 ,strand1 and are well worth a visit4 ,the ,gyroscope1 though now an instrument common and familiar to all students1 is none the less the subject of a problem1 the solution of which is still to seek4 ,it has indeed been entitled the paradox of mechanics2 for though it depends on gravitation1 gravitation yet appears indifferent to it4 ,in order to render the operation of the ,gyroscope as continuous as possible1 so as to facilitate the profound study of its working1 and also to unite another influence with those of the ordinary ,gyroscope1 producing phenomena of which this instrument affords us the spectacle1 a learned ,american has employed electricity as a motive power4 ,illustration3 ,fig4 #bgg4--,the ,gyroscope4 ,the ,gyroscope1 shown in fig4 #bgg1 has a large1 heavy pedestal1 with a pointed column1 which supports the instrument itself4 ,the frame1 of which the electro-magnets form a part1 is connected with a rod1 having at one end a hollow cavity which rests on the point of the vertical column4 ,one of the extremities of the magnetic spool is attached to this cavity1 the other end communicating with the bar which unites the two magnets4 ,over this bar is a spring which breaks the current1 supported by an insulator in hard india-rubber2 it is adjusted so that it touches a small cylinder on the axis of the wheel twice during every rotation of the latter4 ,the wheel's plane of rotation is at right angles with the magnets1 and it carries an armature of soft iron1 which rotates close to the magnet without touching it4 ,the armature is so placed in relation to the surface of contact with the cylinder that breaks the current1 that twice during each rotation1 as the armature approaches the magnets1 it is attracted2 but immediately afterwards1 as the armature comes directly in front of the magnets1 the current is broken1 and the acquired impulsion is sufficient to move the wheel until the armature comes again under the influence of the magnet4 ,the spring which interrupts the current is connected with a thin copper wire1 which stretches back as far as the point of the column1 entwining it several times to render it flexible1 finally bending down and plunging into some mercury enclosed in a round vulcanite cup placed on the column near the pedestal4 ,the pedestal also bears two small stakes for receiving the wires of the battery1 one connected with the column1 and the other communicating by a small wire with the mercury contained in the vulcanite vessel4 ,the magnets1 the wheel1 and all the connected parts can move in any direction round the point of the column4 ,when two large ,bunsen cells1 or four small ones1 are connected with the ,gyroscope1 the wheel turns with great rapidity1 and allowing the magnets to operate1 it not only sustains itself1 but also the magnets and the other objects which are between it and the point of the column in opposition to the laws of gravitation4 ,the wheel1 besides turning rapidly round its axis1 also effects a slow rotation round the column in the direction of the movement experienced by the lower part of the wheel4 ,by placing the arm and the counterpoise of the machine as shown in fig4 #bgg1 so that the wheel and the magnets balance exactly on the pointed column1 the whole machine rests stationary2 but if we give the preponderance to the wheel and the magnets1 the apparatus begins to rotate in a direction contrary to or following that of the upper part of the wheel4 ,the ,gyroscope exemplifies very clearly the persistence with which a body undergoing a movement of rotation maintains itself in the plane of its rotation in spite of gravitation4 ,it shows also the result of the combined action of two forces tending to produce rotations round two axes which are separate1 but situated in the same plane4 ,the rotation of the wheel round its axis1 produced1 in the present instance1 by the electro-magnet1 and the tendency of the wheel to fall or turn in a vertical plane1 parallel to its axis1 produce1 as a result1 the rotation of the entire instrument round a new axis which coincides with the column4 ,,peiffer',s ,,electrophorus4 ,it will now perhaps interest our readers to describe a charming little plaything which is a great favourite with children1 and which has the incontestable merit of early initiating them into all the principal phenomena of the statics of electricity1 and teaching them the science of physics in an amusing form4 ,it is a small electrophorus invented by ,m4 ,j4 ,peiffer1 and reduced to such a point of simplicity1 that it consists merely of a thin plate of ebonite1 about the size of a large sheet of letter paper4 ,the tinned wooden disc of the electrophorus which is found described in most treatises on physics1 is replaced by a small sheet of tin1 about the size of a playing-card1 fastened on to the surface of the ebonite4 ,the ebonite electrophorus produces electricity with remarkable facility4 ,it must be placed flat on a wooden table1 and thoroughly rubbed with the hand2 if it is then lifted1 and the sheet of tin lightly touched1 a spark is elicited from inch to inch in length4 ,the electrophorus is completed by the addition of a number of small accessories in the shape of small dolls made of elder-wood1 which exhibit in a very amusing manner the phenomena of attraction and repulsion4 ,after the board has been charged with electricity1 place the three little figures on the sheet of tin1 and lift up the apparatus1 so as to isolate it from any support4 ,you will then see one little doll extending its arms1 another with its silky hair standing on end1 and a third1 lighter than the others1 leaping like a clown1 and displacing as he does so the two small balls of elder-wood which have been placed on each side of him4 ,we have given an illustration of the three figures performing at once 7fig4 #bgh71 but they are generally used separately4 ,m4 ,peiffer has indeed collected every known accessory for an electric machine1 such as ,geissler's tube1 the electric carillon1 etc4 ,these different experiments are all reduced to their simplest form1 and1 with their appliances1 are all contained in a cardboard box4 ,they are placed beside the electrophorus1 which thus takes the place of an unwieldy electric machine4 ,m4 ,j4 ,peiffer accompanies this little portable cabinet with an exhaustive pamphlet1 which is a valuable guide to the young physicist in studying the first principles of electricity4 ,illustration3 ,fig4 #bgh4--,m4 ,j4 ,peiffer's electrophorus with dolls4 8,it is easy to discover in the education of children10 says ,m4 ,peiffer in his preface1 8how to turn their budding faculties to the best account4 ,would you utilize them in a satisfactory manner8--,then put in their hands playthings which1 in an attractive form1 serve to familiarize them at an early age with those sciences1 a knowledge of which will be at a later period absolutely indispensable to them2 and they will be much more amused than with ordinary commonplace toys40 ,these are sensible words1 in which we heartily concur4 ,yes6 ,science properly taught1 and properly understood1 can indeed be brought within the range of children2 it should give a lasting interest to all amusements1 and form a part of the culture of the youthful mind1 as at a later period it will contribute to the perfect development of the grown man4 ,,magic ,,fish4 ,an ingenious physicist1 ,m4 de4 ,combettes1 who is a civil engineer at ,paris1 has devoted himself to constructing a number of playthings and scientific appliances for young people1 among which we will describe the very curious one represented in fig4 #bgi4 ,a jar is filled with water1 holding in suspension some fish made of tin1 similar to those which children put in water and attract with a magnet4 ,in this case1 however1 the mechanism is hidden1 and the operator can turn the fish first in one direction and then in the other at pleasure4 ,the secret of this experiment is easily explained by examining the illustration 7fig4 #bgi74 ,in the wooden stand which supports the jar there is concealed a small electro-magnet which acts on the soft iron contained in the floating fish4 ,when the current passes the small magnet turns round and attracts the little fish swimming in the water4 ,this gyratory movement can be changed at pleasure by means of a regulator4 ,illustration3 ,fig4 #bgi4--;,experiment of magic fish set in motion by electricity4 ,illustration3 ,fig4 #bhj4--;,an electric toy4 ,we will give an illustration of a few electric toys which ,m4 ,trouv has found for us4 ,in the picture 7fig4 #bha7 we see three different objects1--a rabbit beating a small bell1 a representation of a bird with outstretched wings1 and a pin surmounted by a skull4 ,all these are capable of having movement imparted to them by means of electricity1 although made and intended for ordinary use in the form of scarf-pin or other ornament4 ,let us take the 8death's head0 pin first4 ,it is in gold1 and enamelled with diamond eyes and articulated jaws4 ,the rabbit is also gold1 and carries two small drumsticks1 with which he can play a tiny bell4 ,this device also can be worn as a scarf-pin4 ,illustration3 ,fig4 #bha4--,magic toys4 ,a conducting wire leads from the pin into the waistcoat pocket1 where a small 8pile10 about the size of a cigarette1 is hidden away4 ,if any one particularly admires the scarf-pin1 all you have to do is to insinuate your fingers into your pocket1 and you will1 by contact1 cause the electric current to act upon the pin in your scarf4 ,the death's head will at once begin to roll its eyes and grind its teeth1 while the rabbit1 under similar circumstances1 will begin to play its bell with the greatest energy4 ,the handsome diamond bird represented in the centre of the illustration belongs to ,madame de ,metternich4 ,when any lady wears it in her hair1 she can1 by the concealed wire1 make it flap its jewelled wings1 and by so doing cause much surprise amongst the spectators4 ,we will now endeavour to give a description of the manner in which these toys play their parts in company with the 8hermetic-pile0 which ,m4 ,trouv has applied to many specialities that he has supplied to doctors1 who use them largely4 ,this pile is formed by a 8couple0 of carbon and zinc hermetically enclosed in an ebonite box4 ,the carbon and zinc only occupy one-half of the case4 ,the liquid occupies the other4 ,the sketch 7fig4 #bhj7 on preceding page will explain the apparatus4 ,so long as the case is in its normal position the elements are not immersed in the solution1 and consequently no electricity is developed4 ,but as soon as the figure is placed in a horizontal or leaning position the force is generated2 on readjusting the box the electric current is cut off1 and all development ceases4 ,many curious electrical toys can be seen in ,paris4 ,dolls are made to talk1 and many other wonders for children can be easily procured4 ,,animal ,,and ,,atmospheric ,,electricity4 ,before concluding the subject of electricity we must devote a few pages to the consideration of the electric influence possessed by certain fishes1 and to some of the phenomena of the atmosphere1 especially thunderstorms4 ,we have seen how ,galvani experimented upon the limbs of frogs1 and maintained that they possessed electricity2 he attributed the current in the muscles to that cause4 ,this theory ,volta denied1 but subsequently ,nobili1 in #ahbg1 proved the existence of a current in the frog by means of a ,galvanometer4 ,this was conclusive1 and the experiment was performed in the following manner3--,he filled two vessels with salt and water1 and into one he dipped the crucal muscles of a frog1 and in the other the lumbar nerves were immersed4 ,by putting these vessels in communication with his improved ,galvanometer1 which was extremely sensitive1 he perceived a current passing from the feet towards the head of the animal4 ,it is1 however1 to ,matteucci and ,du ,bois ,reymond that the investigation of the phenomena of the courant propre are due4 ,the former formed a 8pile0 of the thighs of frogs1 and by placing the interior and exterior muscles in contact he formed a current from the inside to the outside muscles4 ,this current is supposed to be occasioned by certain chemical changes which are continually taking place1 and it continues longer in the case of a cold-blooded animal than in a warm-blooded one4 ,there are many interesting papers on this subject included amongst the 8,philosophical ,transactions02 and the 8,physical ,phenomena of ,living ,beings0 is fully treated in ,matteucci's lectures on that subject4 ,in the 8,transactions0 for #ahdh and subsequent years1 other experiments may be perused1 but space will not permit us to dilate upon them4 ,the fact has been established1 and we are told that muscles and nerves1 as well as certain glands of the body1 possess certain electrical properties4 ,the electricity of fishes1 and the power possessed by the torpedo--whose name is now chiefly known in connection with warlike appliances--and the gymnotus1 have been known for a very long time4 ,this fish1 popularly known as the electric eel1 inhabits the warm fresh-water lakes of ,africa1 ,asia1 and ,america4 ,a specimen was exhibited at the ,polytechnic some years ago4 ,this was the fish experimented on at the ,adelaide ,gallery by ,professor ,faraday1 who clearly demonstrated the fact that the electricity of the animal and the common electricity are identical4 ,numerous experiments were made1 and the circuit shock and even sparks were obtained from the gymnotus4 ,in fact1 the gymnotus is a natural electric machine4 ,the force of the shock given by the electric eel is very great1 for ,faraday has put on record that a single discharge of the eel is equal to fifteen ,leyden jars charged as highly as possible4 ,its power does not even end there1 for having shocked people to that extent1 it was capable of a second and occasionally of a third shock of less violence4 ,illustration3 ,fig4 #bhb4--;,electric eel4 ,the manner in which the gymnotus acts is from a regular battery in the head1 the sides of which are filled with a fluid4 ,these cells are something like a honeycomb in appearance4 ,the shock is quite voluntary on the part of the fish4 ,sometimes it will kill its prey1 on other occasions it is merely numbed4 ,professor ,faraday on one occasion placed a live fish in the tub with the gymnotus1 which curled itself so as to enclose the unsuspecting one4 ,in a second the prey was struck dead1 and floated on the water4 ,the gymnotus immediately devoured it1 and went in quest of more4 ,another1 but an injured fish1 was then introduced1 but the electric eel took no trouble about this one4 ,it did not trouble to give it a shock1 seeing it was disabled1 it merely swallowed without killing it4 ,it is also on record that on one occasion an electric eel had stunned a fish which1 before he began to eat it1 gave signs of returning animation2 the eel immediately gave it another shock and killed it4 ,illustration3 ,fig4 #bhc4--,large gymnotus4 ,there were some other curious peculiarities connected with the electric eel4 ,it appears to be quite capable of discriminating between animate and inanimate touch4 ,for instance1 when touched with a glass rod it at first gave signs of electricity1 and discharged a shock at the attacking party4 ,but on subsequent occasions1 when touched with metal rods or glass1 the fish declined to 8shock02 nevertheless the ,professor succeeded the moment he touched the animal with his hands4 ,the torpedo is something like the well-known skate2 it is sometimes called the electric ray1 and is common enough in the ,bay of ,biscay and in the ,mediterranean ,sea4 ,it sometimes pays ,england a visit1 or is caught by fishermen and brought in4 ,we have seen one at ,plymouth1 and a very ugly-looking fish it was4 ,its electric power is considerable4 ,illustration3 ,fig4 #bhd4--,ray torpedo4 c1 brain2 m e1 spinal chord2 o1 eye2 e1 electric organs2 b1 gills2 np1 nl1 nerves2 n1 spinal nerve4 ,there is yet another fish known as the malapterurus2 one species is called the thunder-fish4 ,professor ,wilson has written a paper upon the electric fishes as applied to the remedy of disease1 and considers them the 8earliest electric machines ever known40 ,humboldt relates that the ,south-,american ,indians capture the gymnotus by driving horses into ponds which the electric eels are known to inhabit4 ,the result is that the fish deliver shock after shock upon the unfortunate quadrupeds4 ,mules and horses have frequently been killed by these powerful eels1 and even ,faraday experienced a very great shock when he touched the head and tail of the captive gymnotus with either hand4 ,the malapterurus to which we have referred is an inhabitant of the ,african rivers1 chiefly in the ,nile and ,senegal4 ,such a fish has been known with others for some hundreds of years2 its electrical powers are not great4 ,there are one or two other species of fish which possess electrical qualities1 but none apparently to the same extent as the torpedo and the gymnotus4 ,illustration3 ,fig4 #bhe4--,the ,malapterurus4 ,the electricity of plants also is in some cases very marked4 ,flashes have been seen to come from some flowers in hot and dry weather4 ,currents of electricity have been detected1 and ,wartmann investigated the subject closely4 ,he says the currents in flowers are feeble1 but in succulent fruits and some kinds of grain they are very marked4 ,these currents depend upon the season1 and are greatest in the spring1 when the plant is bathed in sap4 ,these experiences were confirmed by ,bequerel in #ahej1 and he concludes that the rank vegetation in some parts of the world must exercise considerable influence on the electric phenomena of the atmosphere4 ,m4 ,buff has more recently made experiments in this direction1 and he examined plants and trees1 and even mushrooms4 ,m4 de la ,rive1 after carefully summing up the various theories1 comes to the conclusion that it is to chemical reactions that the traces of electricity are due4 ,the subject of atmospherical electricity properly belongs to meteorology1 and under that heading we will treat of it more fully4 ,but lightning is so identified with electricity1 and being the most common form observable to all1 we will say something about thunderstorms and the electric discharges accompanying them4 ,illustration3 ,fig4 #bhf4--;,benjamin ,franklin4 ,before ,franklin's ever-memorable experiment with his kite established the identity of lightning and electricity1 the resemblance between the two discharges had been frequently noticed4 ,the ,etruscans pretended to bring down lightning from heaven1 and ,tullus ,hostilius1 when experimenting or performing certain 8ceremonies10 was killed by the electric discharge he desired to attract4 ,but after all1 we cannot attribute any knowledge of electric science to the ancients1 although they were1 of course1 familiar with electric phenomena4 ,it is to ,dr4 ,wall that testimony points as the first person who remarked the analogy between the electric spark and lightning4 ,this was in #agjh4 ,grey and other philosophers supported the theory1 but could not establish it4 ,to ,franklin1 who in ,june #ageb actually brought down the lightning by his kite and a key1 is the actual discovery due4 ,we have already detailed the circumstances 7page #bjf7 and need not repeat the account of the experiment4 ,of course the ,american philosopher found numerous imitators1 not always with impunity4 ,professor ,richmann was killed by the spirit he was invoking2 ,lemounier and ,beccaria confirmed the theory that the air was full of electricity2 while ,du ,saussure1 from his investigations on the ,alps1 and ,volta from the invention of the pile1 are most famous in the history of electricity4 ,they applied themselves with much success to the investigation of the electric condition of the atmosphere1 of which the disturbances called thunderstorms are the result4 ,the amount of electricity varies in the atmosphere at different times in the day and night4 ,towards midday and midnight the development is generally greatest1 and this fact will account for the prevalence of storms during our hours of rest4 ,again1 different kinds of clouds have different degrees of electricity1 and of different kinds4 ,under certain conditions these clouds will give forth lightning1 and a storm will begin4 ,the more clouds the more globules1 and therefore in summer1 while there is more production of vapour from solutions of salts1 etc41 we are more likely to have the storms4 ,we are most of us familiar with the mass of the 8thunder cloud0 rising in the distance1 light at the upper part1 very dark below1 and throwing out tentacles like the octopus1 coming up sometimes--frequently1 indeed--8against the wind10 impelled by an upper current1 or following the course of a river1 which is not unusual4 ,below1 there is perhaps an army of thin dark clouds4 ,the nature and height of clouds have also a great deal to do with the phenomena displayed4 ,in general1 storm-clouds are positively electrified4 ,illustration3 ,fig4 #bhg4--;,cirrus cloud4 ,clouds are good conductors of electricity1 and yet they may be so insulated by the dry air surrounding them that they will accumulate it2 and when thus charged1 if they encounter other clouds charged with opposite electricity1 the opposing masses will attract each other until a discharge takes place4 ,this is what we term lightning1 and under such conditions electricity1 though very dazzling1 is harmless4 ,it is when the cloud comes near to the earth1 and a discharge is released1 that lightning is so dangerous to persons who remain in the fields4 ,sometimes the discharge comes from the earth to meet that from the cloud4 ,sheep are frequently killed by ground lightning1 and once1 at ,malvern1 we had an escape from an upward stroke4 ,the back-stroke from a cloud is also dangerous4 ,it may happen that the cloud has discharged itself upon the earth many miles away1 but a return discharge takes place at the other end1 and if that end be near the earth the consequences may be serious4 ,as a rule1 the return stroke is not so violent as the first discharge4 ,the colour of lightning varies very much4 ,we have the white1 the blue1 the violet1 and red4 ,the colour depends upon the distance and intensity of the lightning1 and the more there is of it the whiter the light4 ,we can illustrate the varied hues of the electric 8fluid0 by passing a spark through the receiver of an air-pump4 ,if the air be rarefied1 or there be a vacuum1 we shall perceive a blue or violet light4 ,therefore we may conclude that the blue and violet flashes have birth in high strata of the atmosphere4 ,illustration3 ,fig4 #bhh4--;,cumulus cloud4 ,we have all heard how dangerous it is to stand under a tree during a thunderstorm1 or rather1 we should say1 when the storm is approaching us nearly4 ,the tree is a conductor1 and the lightning having no better one at hand will pass through the tree on its way to the earth1 and if we are standing against the tree we shall be included in the course1 and die from the shock to the nerves while the lightning is passing through us4 ,the best position in a thunderstorm1 if we are in the neighbourhood of trees1 is to sit or lie down on the ground some little distance from the base of the nearest tree4 ,if the tree be sixty feet high suppose1 and we sit fifty feet or less from the trunk1 we shall be pretty safe1 because the lightning will reach the tree top before it can reach us4 ,we are protected by it as by a conductor1 bad though it be4 ,standing up in a boat during a storm is not wise4 ,lightning has an affinity for water1 and besides1 if no higher objects are near1 our body will act as a conductor4 ,bed is the safest place1 as blankets are non-conductors4 ,cellars are not the safest by any means4 ,lightning may1 and it frequently does1 strike the house and descend to the basement4 ,if the air be very full of electricity1 and a flash be near1 a person running away may conduct the lightning to himself by creating a vacuum into which the flash may dart4 ,illustration3 ,fig4 #bhi4--,nimbus1 or rain cloud4 ,arago classified lightning into three kinds3 zig-zag1 globular1 and sheet4 ,the first we call forked lightning1 and frequently this kind branches out at the end1 so that although there may be only one flash1 it may strike out in two or three directions at the same time4 ,this may be accounted for by the unequal power of the air strata to conduct the electricity4 ,the forked flashes are of very great length1 extending frequently for miles1 and the bifurcations also are often miles apart4 ,the duration of the flash is less than the thousandth part of a second2 so instantaneous is it that no motion can be perceived even in a most rapidly-moving wheel1 as proved by ,professor ,wheatstone4 ,we sometimes fancy that the flash lasts longer1 but the impression received by the eye quite accounts for the apparently prolonged sight of the lightning4 ,sheet lightning1 the faint flashes frequently seen upon the horizon1 are quite harmless4 ,sheet lightning is that which is seen reflected behind clouds or from far-distant storms4 ,it is sometimes very beautiful4 ,ball1 or globular lightning1 is dangerous1 and globes of fire have been seen to descend1 and striking the ground1 bound onwards for some distance4 ,the descent of these forms of electric discharge has given rise to the popular notion of 8thunderbolts40 ,the 8,mariner's ,lights10 or ,st4 ,elmo's fire1 is frequently observed in ships4 ,it is usually regarded as a fortunate occurrence4 ,it was noticed by ,columbus4 ,one voyager describes the phenomena as follows3--8,the sky was suddenly covered with thick clouds4444 ,there were more than thirty of ,st4 ,elmo's fires on the ship4 ,one of them occupied the vane of the mainmast4 ,i sent a sailor to fetch it4 ,when he was aloft he heard a noise like that which is made when moist gunpowder is burned4 ,i ordered him to take off the vane4 ,he had scarcely executed this order1 when the fire quitted it and placed itself at the apex of the mainmast1 whence it could not possibly be removed40 ,illustration3 ,fig4 #bij4--,thunderstorm4 ,there have been occasions when the manes and tails of horses1 and even the ears of human beings1 have shown a phosphorescent light which emitted a hissing noise4 ,alpine travellers have noticed similar phenomena2 and ,professor ,forbes1 when crossing the ,theodule ,pass into ,italy1 heard the hissing sound in his alpenstock4 ,the tips of rocks and grass points were all hissing too4 ,the party were in the midst of an electric cloud4 ,when the ,professor turned the point of his alpenstock upwards1 a vivid flash was emitted1 but no thunder followed4 ,they descended as quickly as possible from such a dangerous neighbourhood4 ,illustration3 ,fig4 #bia4--,st4 ,elmo's fire4 ,it is observable that the properties of lightning and of the electric spark are identical--the faint crackle of the latter being magnified into the loud rolling of the thunder4 ,the disturbance of the atmosphere is the cause of the loud reverberations1 and echoes produced from clouds tend to intensify and prolong the peal4 ,the sound rises and falls1 and varies accordingly as the cloud is near or far4 ,a smart sharp report or rattle denotes the nearness of the lightning1 while the gradual swelling and subsidence1 followed1 mayhap1 by an increasing volume of sound1 which in its turn dies away1 tells us that the danger is not imminent4 ,the cause o this loud rolling1 unless it proceeds from echoes from different clouds1 has not been satisfactorily explained4 ,sound travels less quickly than light1 and therefore we only hear the thunder some seconds after we have perceived the flash4 ,it is therefore conceivable that we may hear the last reverberations and its echoes first1 and the sound of the first disturbance with its echoes last of all4 ,thus there will be distinct sounds4 ,firstly1 the actual noise we call thunder from the air strata nearest to us2 secondly1 the echoes of that disturbance from the clouds1 of course fainter2 then we hear the sound caused by the tearing asunder of the air particles farthest off1 and again the echoes of that disturbance4 ,this theory will1 we think1 account for the swelling peals of thunder1 and the successive loud and fainter reverberations4 ,at any rate1 in the absence of any other theory1 we submit it for consideration4 ,the sound of thunder is seldom or never heard at a distance greater than fifteen miles4 ,lightning conductors are such every-day objects that no description is necessary2 but the reason the lightning runs along it harmlessly is because the galvanized iron rod is the best conductor in the immediate neighbourhood4 ,where there is not a good conductor lightning will accept the next best1 and so on1 any conductor being better than none4 ,the point of the rod cannot contain any electricity1 there being no room for it1 and the 8fluid10 as it is termed1 runs down to the ground1 to terminate1 when possible1 in water or charcoal4 ,a great deal of electricity is no doubt carried away from the air by the numerous conductors without any spark passing4 ,until ,sir ,w4 ,snow ,harris brought forward his lightning conductors for ships1 the loss was great at sea4 ,but now we rarely hear of any vessel being disabled by lightning4 ,we owe to ,franklin the idea of the lightning conductor4 ,according to observations made by ,mr4 ,crosse1 the following statement shows the tendency of the atmosphere1 in certain conditions1 to thunderstorms4 ,we may accept the deduction of ,m4 ,peltier that grey and slate-colour clouds are charged with negative1 and white1 rose-colour1 and orange clouds with positive electricity4 ,the order of arrangement in the following table places the most likely source of thunderstorms first1 and the least likely source at the end1 with regular rotation of intermediate probabilities intervening3-- #a4 ,regular thunder clouds4 #b4 ,driving fog with small rain4 #c4 ,fall of snow1 or hailstorm4 #d4 ,smart shower on a hot day4 #e4 ,smart shower on a cold day4 #f4 ,hot weather after wet days4 #g4 ,wet weather after dry days4 #h4 ,clear frosty weather4 #i4 ,clear warm weather4 #aj4 ,cloudy days4 #aa4 8,mackerel0 sky4 #ab4 ,sultry weather and hazy clouds4 #ac4 ,cold damp night4 #ad4 ,cold1 dry north-east winds4 ,we have thus briefly touched upon some of the atmospherical phenomena directly attributable to electricity4 ,in our articles upon ,meteorology we will consider the aurora and many other interesting facts concerning the atmosphere1 and the effects of sound1 heat1 and light upon the air4 ,illustration3 ,fig4 #bib4--,lightning conductor4 ,,footnotes3 #ah ,we are indebted for many facts respecting ,mr4 ,edison's light in this chapter to a paper by ,mr4 ,upton4 ,,chapter ,,xxiii4 ,,aeronautics4 ,,pressure ,,of ,,air ,,in ,,bodies--,,early ,,attempts ,,to ,,fly ,,in ,,the ,,air--,,discovery ,,of ,,hydrogen--,,the ,,montgolfier ,,balloons--,,first ,,experiments ,,in ,,paris--,,noted ,,ascents4 ,in the first part of this volume we entered into the circumstances of air pressure1 and in the ,chemistry section we shall be told about the atmosphere and its constituents4 ,we know that the air around us is composed principally of two gases1 oxygen and nitrogen1 with aqueous vapour and some carbonic acid4 ,an enormous quantity of carbonic acid is produced every day1 and were it not for the action of vegetation the amount produced would speedily set all animal life at rest4 ,but our friends1 the plants1 decompose the carbonic acid by assimilating the carbon and setting free the oxygen which animals consume4 ,thus our atmosphere keeps its balance1 so to speak4 ,nothing is lost in nature4 ,we have illustrated the pressure of the atmosphere by the ,magdeburg hemispheres1 and we know that the higher we ascend the pressure is lessened4 ,the weight of the atmosphere is #ae lbs4 to the square inch at sea level4 ,this we have seen in the barometer4 ,now pressure is equal4 ,any body immersed in a liquid suffers pressure1 and we remember ,archimedes and the crown4 ,it displaced a certain amount of water when immersed4 ,a body in air displaces it just the same4 ,therefore when any body is heavier than the air1 it will fall just as a stone will fall in water4 ,if it be of equal weight1 it will remain balanced in the air1 if lighter it will rise1 till it attains a height where the weight of the atmosphere and its own are equal2 there it will remain till the conditions are altered4 ,now we will readily understand why balloons float in the air1 and why clouds ascend and descend in the atmosphere4 ,in the following pages we propose to consider the question of ballooning1 and the possibility of flying4 ,we all have been anxious concerning the unfortunate balloonist who was lost in the ,channel1 so some details concerning the science generally1 with the experiences of skilled aeronauts1 will guide us in our selection of material4 ,we will first give a history of the efforts made by the ancients to fly1 and this ambition to soar above the earth has not yet died out4 ,from a very early period man appears to have been desirous to study the art of flying4 ,the old myths of ,ddalus and ,icarus show us this1 and it is not to be wondered at4 ,when the graceful flight of birds is noticed1 we feel envious almost that we cannot rise from the earth and sail away at our pleasure over land and sea4 ,any one who has watched the flight of the storks around and above ,strasburg will feel desirous to emulate that long1 swift-sailing flight without apparent motion of wing1 and envy the accuracy with which the bird hits the point aimed at on the chimney1 however small4 ,it is small wonder that some heathens of old time looked upon birds as deities4 ,the earliest flying machine that we can trace is that invented by ,archytas1 of ,tarentum1 ,b4,c4 #djj4 ,the historian of the 8,brazen ,age0 tells us how the geometrician1 ,archytas1 made a wooden pigeon which was able to sustain itself in the air for a few minutes1 but it came down to the ground after a short time1 notwithstanding the mysterious 8aura spirit0 with which it was supposed to be endowed4 ,the capability of flying has for centuries been regarded as supernatural4 ,putting angels aside1 demons are depicted with wings like bats' wings1 while witches1 etc41 possessed the faculty of flying up chimneys upon broomsticks4 ,we even read in childish lore of an old woman who 8went up in a basket0 7perhaps a balloon-car71 and attained a most astonishing altitude-an elevation no less than 8seventy times as high as the moon60 ,but to descend to history4 ,it is undoubtedly true that in the time of ,nero1 ,simon ,magus attempted to fly from one house to another by means of some mechanical contrivance1 and failing1 killed himself4 ,roger ,bacon1 the 8admirable doctor10 to whom the invention of gunpowder is generally attributed1 had distinct notions of flying by means of machines1 and 8hollow globes10 and 8liquid fire40 ,but he did not succeed1 nor did many successive attempts succeed any better in subsequent years4 ,bishop ,wilkins treated of the art of flying1 but most1 if not all who discussed the subject appear to have been indebted to ,roger ,bacon for the idea4 ,when the nature and pressure of the atmosphere by ,torricelli's experiments became better known1 ,father ,lana1 a ,jesuit priest1 constructed a flying machine or balloon of curious shape4 ,he proposed to fix four copper globes1 very thin1 and about twenty feet in diameter1 and to these he fastened a boat or car1 looking very much like a basin4 ,his idea was to empty his great copper globes1 and that their buoyancy would then bear the weight of the traveller4 ,but he overlooked or was ignorant of the effect of the atmospheric pressure1 which would have speedily crushed the thin copper globes when empty4 ,lana's suggestion was made in #afgj1 the barometer had been discovered in #afdc4 ,there were some fairly successful experiments made in flying in #afgh and in #agji4 ,the former attempt was made by ,besmir1 a locksmith of ,sable1 who raised himself by means of wings up to the top of a house by leaps1 and then succeeded in passing from one house to another lower down by supporting himself in the air for a time4 ,he started from an elevated position1 and came down by degrees4 ,dante1 a mathematician1 also tried to fly1 but without great success4 ,he broke his thigh on one occasion4 ,laurence de ,gusman claimed an invention for flying in #agji1 and petitioned for a 8patent10 which was granted by the king's letter4 ,the machine appears to have borne some resemblance to a bird4 ,it was not till #aghb1 however1 that the true art of aerial navigation was discovered4 ,the knowledge of hydrogen gas possessed by ,cavendish in #agff no doubt led up to it1 and in the year following its discovery ,professor ,black1 lecturing in ,edinburgh1 stated that it was much lighter than the atmosphere1 and that any vessel filled with the gas would rise in the air4 ,we now come to the invention of the ,,balloon 7so called from its shape being similar to a vessel used in the laboratory7 by the ,brothers ,montgolfier4 ,illustration3 ,fig4 #bic4--,montgolfier balloon4 ,stephen and ,james ,montgolfier were paper-makers1 and carried on their business at ,annonay1 near ,lyons1 but it was partly by accident that the great discovery was made4 ,they had no knowledge of the buoyancy of hydrogen gas4 ,they took their idea of the balloon 7inflated7 from noticing an ascending column of smoke4 ,it occurred to ,stephen that if a paper bag were filled with smoke it would ascend into the air4 ,a large bag was made and some paper burnt beneath it in a room4 ,when the smoke had filled the bag it was released1 and immediately ascended to the ceiling4 ,here was the germ of the ,montgolfier or heated air balloon4 ,the experiment was repeated in the open air with even greater success1 and a trial upon a larger scale was immediately determined upon4 ,a story is related of ,mongolfier when prosecuting his researches1 that a widow whose husband had belonged to the printing firm with whom ,montgolfier was then connected in business1 saw the smoke issuing from the room in which the little balloon was being filled4 ,she entered1 and was astonished to see the difficulty experienced by the experimenter in filling the balloon4 ,it swerved aside1 and increased the trouble he had to keep it above the chafing dish4 ,montgolfier was greatly troubled1 and seeing his disappointment1 the widow said1 8,why don't you fasten the balloon to the chafing dish80 ,this had not occurred to the experimenter1 and the idea was a valuable one4 ,that was the secret of success4 ,the ,montgolfier ,brothers determined to exhibit their successful experiment1 and accordingly on the #eth of ,june1 #aghc1 a great concourse assembled to see the wonderful sight4 ,a large canvas or linen balloon was made and suspended over a fire of chopped straw4 ,the heated air quickly filled the balloon1 which rose high in the air1 and descended more than a mile away4 ,this balloon contained #bb1jjj cubic feet of heated air1 which is lighter than cold air1 and of course rising carried the globe with it4 ,as soon as the air began to cool the balloon ceased to rise1 and as it got colder descended4 ,here was the actual discovery of the science of ,aerostatics4 ,the intelligence of the success achieved soon spread from ,france to other countries4 ,paris1 however1 was in advance1 and the ,brothers ,robert applied hydrogen gas to a balloon which was sent up from the ,champ de ,mars in ,august #aghc4 ,there was some trouble experienced in filling it1 but when the balloon was at length released it realized all expectations by remaining in the air nearly an hour4 ,when at length it fell it met with a worse fate than it deserved1 for the ignorant and superstitious peasantry at once destroyed it4 ,after this ,montgolfier exhibited his experiment next time at ,versailles in the presence of the ,court4 ,the first aerial travellers appeared on this occasion--viz41 a sheep1 a cock1 and a duck1 which were secured in the car4 ,they all descended in safety1 and this success encouraged ,m4 ,pilatre de ,rozier to make an attempt in a 8fire balloon40 ,he went up first in a captive balloon1 and at length he and a friend1 the ,marquis d',arlandes1 ascended from the ,bois de ,boulogne4 ,the trip was a decided success1 and the possibility of navigating the air was fully demonstrated4 ,soon after this1--viz41 in ,december #aghc1--;an ,italian ,count1 named ,zambeccari1 made an ascent in ,london1 and came down safely at ,petworth4 ,,mm4 ,charles and ,robert ascended from ,paris in ,december1 and in ,february a balloon crossed the ,english ,channel4 ,we must pass over some time and come to the ascents of ,lunardi1 which caused great excitement in ,london4 ,his balloon was a very large one1 and was inflated1 or rather partially so1 at the ,artillery ground4 ,some delay occurred1 and fearing a riot1 ,m4 ,lunardi proposed to go up alone with the partially-filled balloon4 ,a ,mr4 ,biggin who had intended to ascend was left behind4 ,the ,prince of ,wales was present1 with thousands of spectators4 ,lunardi cast off and ascended rapidly1 causing great admiration from the whole metropolis4 ,judge and jury1 sovereign and ministers1 all turned out to gaze at the balloon2 a guilty prisoner was acquitted hurriedly1 so that no time was lost in discussion1 and one lady died of excitement4 ,lunardi was regarded as a hero1 and made many other ascents4 ,he died in #ahjf4 ,in those earlier days one or two fatal accidents happened4 ,count ,zambeccari and a companion were in a balloon which caught fire1 and both occupants of the car leaped from it as they were descending4 ,the ,count was killed on the spot1 and his companion was much injured4 ,pilatre de ,rozier made an attempt to cross the channel to ,england in #aghe2 he had reached three thousand feet when the balloon caught fire1 and the unfortunate traveller was precipitated to the ground4 ,his associate only survived him a few minutes4 ,illustration3 ,fig4 #bid4--,,mm4 ,charles' and ,roberts' balloon4 ,illustration3 ,fig4 #bie4--;,blanchard's balloon4 ,it is to the celebrated ,english aeronaut1 ,mr4 ,green1 that the substitution of carburetted hydrogen or street gas for hydrogen is due1 and since his ascent in #ahba no other means of inflation have been used4 ,a great many quite successful and a few unsuccessful ascents have been made for pleasure or profit4 ,mr4 ,green1 in the ,nassau balloon1 passed over to ,nassau1 a distance of five hundred miles1 in eighteen hours4 ,this exploit was the cause of the name being bestowed upon the balloon4 ,the ,giant of ,m4 ,nadar was exhibited in ,england1 and it was an enormous one1 being an hundred feet high1 and nearly as wide in the widest part4 ,but even this machine was outdone by the ,godard 8,montgolfier0 balloon1 which was one hundred and seventeen feet high1 and carried a stove4 ,we give illustrations of these celebrated balloons1 and will now pass on to the more scientific portion of the subject and the ascents of ,mr4 ,glaisher and other aeronauts for the purpose of making meteorological observations1 and the use of balloons for purposes of observation in war4 ,it appears that the first ascent for scientific investigation was made in the year #ahjc4 ,the aeronauts were ,messrs4 ,robertson and ,lhoest4 ,they ascended from ,hamburg and came down at ,hanover1 and made meantime several experiments with reference to the electrical condition of the atmosphere1 its influence upon a magnetic needle1 and some experiments with regard to acoustics and heat4 ,the report was presented to the ,st4 ,petersburg ,academy1 and contains the result of their interesting observations4 ,the travellers ascertained that at the elevation to which they attained1--viz41 #be1ejj feet1--the temperature was on that ,july day fifty degrees colder1 falling to #aif1 while on the earth the thermometer had shown #fh4 ,they ascertained that glass and wax did not become electric when rubbed1 that the ,voltaic battery lost much of its power1 that the oscillation of a 8dipping needle0 increased as they mounted into the air1 while sound was certainly less easily transmitted at that elevation1 and struck them as less powerful in tone4 ,the heat experiment was not a success1 owing to the breaking of the thermometer4 ,they wished to find the temperature of boiling water at that elevation1 but when the experiment was about to be made ,robertson accidentally plunged the instrument into the fire instead of into the water4 ,so the question was not settled4 ,the effect upon the aeronauts was a sensation of sleepiness1 and two birds died4 ,the muscular powers of the voyagers also appear to have been much affected1 and similar sensations may be experienced by travellers on high mountains who find their breath very short and a disinclination to exertion oppress them4 ,,mm4 ,biot and ,gay-,lussac made a very interesting ascent in #ahjd4 ,we will detail their experiences at some length1 for the coolness displayed and the value of the observations made are remarkable in the history of scientific ballooning4 ,they started1 at #aj o'clock a4m4 on the #bcrd of ,august1 and when the balloon had carried them up to an altitude of #h1fjj feet they commenced their experiments4 ,they had some animals in the car with them1 a bee amongst the number1 and the insect was let go first4 ,it flew away swiftly1 not at all inconvenienced apparently4 ,the sun was very hot at #ef ,fahr4 ,their pulses were beating very fast1 but no inconvenience was felt4 ,when #aa1jjj feet had been reached a linnet was permitted to go at large1 but after a little time the bird returned to the balloon4 ,it remained perched for a few minutes1 and then dashed downwards at a tremendous pace4 ,a pigeon was then liberated4 ,it also appeared very uncertain1 and wheeled around in circles for a time4 ,at last it gained confidence1 and descended1 and disappeared in the clouds beneath4 ,they made other experiments1 but descended without having obtained as accurate results as had been anticipated4 ,illustration3 ,fig4 #bif4--,the ,nassau balloon4 ,illustration3 ,fig4 #big4--,the 8,giant0 balloon of ,m4 ,nadar4 ,on the next occasion1 however1 every care was taken1 and on the #aeth of ,september the important ascent was made by ,gay-,lussac alone4 ,he fixed hanging ropes to the balloon with the view to check the rotating movements1 and having provided himself with all necessary apparatus and two vacuum flasks to bring down some of the upper air1 the young man started4 ,the barometer marked #cjff1 the thermometer #hb 7,fahr474 ,at an elevation of #ab1fhj feet ,lussac perceived that the variation of the compass was the same as on land4 ,two hundred feet higher up he ascertained that a key held in the magnetic direction repelled with the lower1 and attracted with its upper extremity the north pole of a needle4 ,this experiment was repeated with the same result at an elevation of #bj1jjj feet1 which shows how the earth exercises its magnetic influence4 ,the temperature of the air was found to decrease in proportion as the ascent up to #ab1jjj feet1 where the reading was #dgc4 ,it then increased up to #ad1jjj feet by #f1 and then regularly diminished again as the balloon rose1 till at the greatest elevation reached1 #bc1jjj feet1 there was a difference of #fg in the temperature on the earth1 for at the maximum height attained the thermometer stood at #adi4 ,but the most important fact ascertained1 and one which set many theories at rest1 was the composition of the atmosphere in those high altitudes4 ,we mentioned that ,gay-,lussac took up two empty flasks from which the air had been taken4 ,the vacuum was almost perfect4 ,when the aeronaut had reached #ba1dfj feet he opened one flask1 and it was quickly filled2 he secured it carefully2 and when at his highest point1--four miles and a half above the sea-level1--he opened the other flask4 ,the barometer stood at #ab4ie inches1 and the cold was very great4 ,the voyager felt benumbed1 and experienced difficulty of breathing2 his throat was parched and dry4 ,so ,lussac determined to return1 he could go no higher4 ,he dropped gently near ,rouen1 and soon reached ,paris4 ,as soon as possible the air in the flasks was submitted to very delicate tests1 and to the satisfaction of the scientists engaged it was found to be in exactly the same proportions as that collected near the earth--two hundred and fifteen parts of oxygen to every thousand of atmospheric air4 ,messrs4 ,banal and ,bixio1 in #ahej1 also made some observations1 and found the temperature very variable4 ,at #bc1jjj feet they found the thermometer at minus #chb ,fahr41 which was much below the cold experienced by ,gay-,lussac4 ,we may still conclude that the various currents of the atmosphere cause considerable variation1 and that it is impossible to lay down anything respecting the degrees of heat and cold likely to be found at certain elevations4 ,we quote ,arago's observations upon this ascent3-- 8,this discovery0 7the ice particles found in the air7 8explains how these minute crystals may become the nucleus of large hailstones1 for they may condense round them the aqueous vapour contained in the portion of the atmosphere where they exist4 ,they go far to prove the truth of ,mariotte's theory1 according to which these crystals of ice suspended in the air are the cause of parahelia--or mock-suns and mock-moons4 ,moreover1 the great extent of so cold a cloud explains very satisfactorily the sudden changes of temperature which occur in our climates40 ,m4 ,flammarion gives in his 8,voyages0 some very interesting and amusing particulars1 as well as many valuable scientific observations4 ,during one ascent he remarked that the shadow of the balloon was white1 and at another time dark4 ,when white the surface upon which it fell looked more luminous than any other part of the country6 ,the phenomenon was an anthelion4 ,the absolute silence impressed the voyager very much4 ,he adds1 8,the silence was so oppressive that we cannot help asking ourselves are we still alive6 ,we appear to appertain no longer to the world below40 ,m4 ,flammarion's observations on the colour of what we term the sky are worth quoting--not because they are novel1 but because they put so very clearly before us the appearance we call the 8blue vault40 ,he says1--speaking of the non-existence of the 8celestial vault10--8,the air reflects the blue rays of the solar spectrum from every side4 ,the white light of the sun contains every colour1 and the air allows all tints to pass through it except the blue4 ,this causes us to suppose the atmosphere is blue4 ,but the air has no such colour1 and the tint in question is merely owing to the reflection of light4 ,planetary space is absolutely black2 the higher we rise the thinner the layer of atmosphere that separates us from it1 and the darker the sky appears40 ,illustration3 ,fig4 #bih4--,the 8,eagle0 of ,m4 ,godard4 ,some beautiful effects may be witnessed at night from a balloon1 and considering the few accidents there have been in proportion to the number of ascents1 we do not wonder at balloon voyages being undertaken for mere pleasure4 ,when science has to be advanced there can be no objection made1 for then experience goes hand-in-hand with caution4 ,it is only the ignorant who are rash2 the student of ,nature learns to respect her1 and to attend to her admonitions and warnings in time4 ,the details of the ascents of famous aeronauts give us a great deal of pleasant and profitable reading4 ,the phenomena of the sky and clouds1 and of the heavens1 are all studied with great advantage from a balloon1 or 8aerostat10 as it is the fashion to call it4 ,the grand phenomena of 8,ulloa's circles10 or anthelia1 which represent the balloon in air1 and surrounded by a kind of glory1 or aureola1 like those represented behind saintly heads1 appear1 as the name denotes1 opposite to the sun4 ,the various experiments made to ascertain the intensity of sounds have resulted in the conclusion that they can be heard at great distances4 ,for instance1 the steam whistle is distinctly audible #aj1jjj feet up in the air1 and human voices are heard at an altitude of #e1jjj feet4 ,a man's voice alone will penetrate more than #c1jjj feet into the air2 and at that elevation the croaking of frogs is quite distinguishable4 ,this shows that sound ascends with ease1 but it meets with great resistance in its downward course1 for the aeronaut cannot make himself audible to a listener on the earth at a greater distance than #cjj or #djj feet1 though the latter can be distinctly heard at an elevation of #a1fjj feet4 ,the diminution of temperature noted by ,m4 ,flammarion is stated to be #a ,fahr4 for every #cde feet on a fine day4 ,on a cloudy day the mean decrease was #a for every #ced feet of altitude4 ,the temperature of clouds is higher than the air surrounding them1 and the decrease is more rapid near the surface1 less rapid as the balloon ascends4 ,we may add that at high elevations the cork from a water-bottle will pop out as if from a champagne flask4 ,we have hitherto referred more to ,m4 ,flammarion and other ,french aeronauts1 but we must not be considered in any way oblivious of our countrymen1 ,messrs4 ,glaisher1 ,green1 and ,coxwell1 nor of the ,american1--one of the most experienced of aerial voyagers1--,mr4 ,wise4 ,the scientific observations made by the ,french voyagers confirmed generally ,mr4 ,glaisher's experiments4 ,this noted air-traveller made twenty-eight ascents in the cause of science1 and his experiences related in 8,travels in the ,air10 and in the 8,reports0 of the ,british ,association1 are both useful and entertaining4 ,for 8,sensational ballooning0 one wishes to go no farther than his account of his experience with ,mr4 ,coxwell1 when 7on the #eth of ,september1 #ahfb7 he attained the greatest elevation ever reached1 viz41 seven miles1 or thirty-seven thousand feet4 ,we condense this exciting narrative for the benefit of those who have not seen it already4 ,the ascent was made from ,wolverhampton4 ,at #a4ci p4m41 the balloon was four miles high1 the temperature was #h1 and by the time the fifth mile had been reached the mercury was below zero1 and up to this time observations had been made without discomfort1 though ,mr4 ,coxwell1 having exerted himself as aeronaut1 found some difficulty in breathing4 ,about #b o'clock1 the balloon still ascending1 ,mr4 ,glaisher could not see the mercury in the thermometer1 and ,mr4 ,coxwell had just then ascended into the ring above the car to release the valve line which had become twisted4 ,mr4 ,glaisher was able to note the barometer1 however1 and found it marked #aj inches1 and was rapidly decreasing4 ,it fell to #i inches1 and this indicated an elevation of #bi1jjj feet6 ,but the idea was to ascend as high as possible1 so the upward direction was maintained4 8,shortly afterwards10 writes ,mr4 ,glaisher1 8,i laid my arm upon the table possessed of its full vigour1 and on being desirous of using it ,i found it powerless1--it must have lost power momentarily4 ,i tried to move the other arm1 and found it powerless also4 ,i then tried to shake myself1 and succeeded in shaking my body4 ,i seemed to have no limbs4 ,i then looked at the barometer1 and whilst doing so my head fell on my left shoulder40 ,mr4 ,glaisher subsequently quite lost consciousness1 and 8black darkness0 came4 ,while powerless he heard ,mr4 ,coxwell speaking1 and then the words1 8,do try1 now do40 ,then sight slowly returned1 and rousing himself1 ,mr4 ,glaisher said1 8,i have been insensible40 ,mr4 ,coxwell replied1 8,you have1 and ,i1 too1 very nearly40 ,mr4 ,coxwell's hands were black1 and his companion had to pour brandy upon them4 ,mr4 ,coxwell's situation was a perilous one4 ,he had lost the use of his hands1 which were frozen1 and had to hang by his arms to the ring and drop into the car4 ,he then perceived his friend was insensible1 and found insensibility coming on himself4 ,there was only one course to pursue--to pull the valve line and let the gas escape1 so as to descend4 ,but his hands were powerless6 ,as a last resource he gripped the line with his teeth1 and bending down his head1 after many attempts succeeded in opening the valve and letting the gas escape4 ,the descent was easily made1 and accomplished in safety4 ,illustration3 ,fig4 #bii4--;,a descending balloon4 ,some pigeons were taken up on this occasion1 and were set free at different altitudes4 ,the first1 at three miles1 8dropped as a piece of paper02 the second1 at four miles1 8flew vigorously round and round1 apparently taking a dip each time02 a third1 a little later1 8fell like a stone40 ,on descending a fourth was thrown out at four miles1 and after flying in a circle1 8alighted on the top of the balloon40 ,of the remaining pair one was dead when the ground was gained1 and the other recovered4 ,the observations noted are too numerous to be included here4 ,some1 we have seen1 were confirmed by subsequent aeronauts1 and as we have mentioned them in former pages we need not repeat them4 ,the results differed very much under different conditions1 and it is almost impossible to decide upon any law4 ,the direction of the wind in the higher and lower regions sometimes differed1 sometimes was the same1 and so on4 ,the 8,reports0 of the ,british ,association 7#ahfb-ahff7 will furnish full particulars of all ,mr4 ,glaisher's experiments4 ,we have scarcely space left to mention the parachutes or umbrella-like balloons which have occasionally been used4 ,its invention is traced to very early times2 but ,garnerin was the first who descended in a parachute1 in #agig1 and continued to do so in safety on many subsequent occasions4 ,the parachute was suspended to a balloon1 and at a certain elevation the voyager let go and came down in safety4 ,he ascended once from ,london1 and let go when #h1jjj feet up4 ,the parachute did not expand as usual1 and fell at a tremendous rate4 ,at length it opened out1 and the occupier of the car came down forcibly1 it is true1 but safely4 ,the form of the parachute is not unlike an umbrella opened1 with cords attaching the car to the extremities of the 8ribs10 the top of the basket car being fastened to the 8stick0 of the umbrella4 ,mr4 ,robert ,cocking invented a novel kind of parachute1 but when he attempted to descend by it from ,mr4 ,green's balloon it collapsed1 and the unfortunate voyager was dashed to pieces4 ,his remains were found near ,lee1 in ,kent4 ,mr4 ,hampton did better on ,garnerin's principle1 and made several descents in safety and without injury4 ,the problem of flying in the air has attracted the notice of the ,aeronautical ,society1 established in #ahgc1 but so far without leading to practical results1 though many daring and ingenious suggestions have been put forth in the 8,reports40 ,it is not within our province to do more than refer to the uses of the balloon for scientific purposes1 but we may mention the services it was employed upon during the ,french war1 #ahgj-ga4 ,the investment of ,paris by the ,german army necessitated aerial communication1 for no other means were available4 ,balloon manufactories were established1 and a great number were made1 and carried millions of letters to the provinces4 ,carrier-pigeons were used to carry the return messages to the city1 and photography was applied to bring the correspondence into the smallest legible compass4 ,the many adventures of the aeronauts are within the recollection of all4 ,a few of the balloons never reappeared2 some were carried into ,norway1 and beyond the ,french frontier in other directions4 ,the average capacity of these balloons was #gj1jjj cubic feet4 ,of course it will be understood how balloons are enabled to navigate the air4 ,the envelope being partly filled with coal-gas-heated air and hydrogen1 is much lighter than the surrounding atmosphere1 and rises to a height according as the density of the air strata diminishes4 ,the density is less as we ascend1 and the buoyant force also is lessened in proportion4 ,so when the weight of the balloon and its occupants is the same as the power of buoyancy1 it will come to a stand1 and go no higher4 ,it can also be understood that as the pressure of the outside becomes less1 the expansive force of the gas within becomes greater4 ,we know that gas is very compressible1 and yet a little gas will fill a large space4 ,therefore1 as the balloon rises1 it retains its rounded form1 and appears full even at great altitudes2 but if the upper part were quite filled before it left the ground1 the balloon would inevitably burst at a certain elevation when the external pressure of the air would be removed1 unless an escape were provided4 ,this escape is arranged for by a valve at the top of the balloon1 and the lower part above the car is also left open very often1 so that the gas can escape of itself4 ,when a rapid descent is necessary1 the top valve is opened by means of a rope1 and the balloon sinks by its own weight4 ,mr4 ,glaisher advises for great ascensions a balloon of a capacity of #ij1jjj cubic feet1 and only filled one-third of that capacity with gas4 ,six hundred pounds of ballast should be taken4 ,illustration3 ,fig4 #cjj4--;,filling a balloon4 ,a very small quantity of ballast thrown away will make a great difference2 a handful will raise the balloon many feet1 and a chicken bone cast out occasions a rise of thirty yards4 ,the ballast is carried in small bags1 and consists of dry sand1 which speedily dissipates in the air as it falls4 ,by throwing out ballast the aeronaut can ascend to a great height--in fact1 as high as he can go1 the limit apparently for human existence being about seven miles1 when cold and rarefied air will speedily put an end to existence4 ,it is a curious fact1 that however rapidly the balloon may be travelling through the air1 the occupants are not sensible of the motion4 ,this1 in part1 arises from the impossibility of comparing it with other objects4 ,we pass nothing stationary which would indicate the pace at which we travel4 ,but the absence of oscillation is also remarkable2 even a glass of water may be filled brim-full1 and to such a level that the water is above the rim of the glass1 and yet not a drop will fall4 ,this experiment was made by ,m4 ,flammarion4 ,when the aeronaut has ascended some distance the earth loses its flat appearance1 and appears as concave as the firmament above4 ,guide ropes are usually attached to balloons1 and as they rest upon the ground they relieve the balloon of the amount of weight the length trailing would cause4 ,they thus act as a kind of substitute for ballast as the balloon is descending4 ,most of the danger of aerial travelling lies in the descent2 and though in fine weather the aeronaut can calculate to a nicety where he will descend1 on a windy day1 he must cast a grapnel1 which catches with an ugly jerk1 and the balloon bounds and strains at her moorings4 ,although many attempts have been made to guide balloons through the air1 no successful apparatus has ever been completed for use4 ,paddles1 sails1 fans1 and screws have all been tried1 but have failed to achieve the desired end4 ,whether man will ever be able to fly we cannot of course say4 ,in the present advancing state of science it may not be impossible ere long to supply human beings with an apparatus worked by electricity1 perhaps1 which will enable them to mount into the air and sustain themselves4 ,but even the bird cannot always fly without previous momentum4 ,a rook will run before it rises1 and many other birds have to 8get up steam10 as it were1 before they can soar in the atmosphere4 ,eagles and such heavy birds find it very difficult to rise from the ground4 ,we know that vultures when gorged cannot move at all1 or certainly cannot fly away2 and eagles take up their positions on high rocks1 so that they may launch down on their prey1 and avoid the difficulty of rising from the ground4 ,they swoop down with tremendous momentum and carry off their booty1 but often lose their lives from the initial difficulty of soaring immediately4 ,we fear man's weight will militate against his ever becoming a flying animal4 ,when we obtain a knowledge of the atmospheric currents we shall no doubt be able to navigate our balloons2 but until then--and the information is as yet very limited1 and the currents themselves very variable--we must be content to rise and fall in the air1 and travel at the will of the wind in the upper regions of the atmosphere4 ,,chapter ,,xxiv4 ,,chemistry4 ,,introduction4 ,,what ,,chemistry ,,is--,,the ,,elements--,,metallic ,,and ,,non-,,metallic--,,atomic ,,weight--,,acids--,,alkalis--,,bases--, ,salts--,,chemical ,,combination ,,and ,,study4 ,chemistry is the science of phenomena which are attended by a change of the objects which produce them4 ,we know that when a candle burns1 or when wood is burned1 or even a piece of metal becomes what we term 8rusty10 that certain chemical changes take place4 ,there is a change by what is termed chemical action4 ,rust on iron is not iron2 it is oxide of iron4 ,the oxygen of the air causes it4 ,so we endeavour1 by ,chemistry1 to find out the nature of various bodies1 their changes1 and the results4 ,illustration3 ,fig4 #cja4--,the ,laboratory4 ,in nature we have simple and compound bodies4 ,the former are called ,,elements4 ,we must not confuse these elements with the so-called elements--earth1 air1 fire1 and water4 ,these are really compound bodies4 ,an element is a substance or a gas which is not composed of more than one constituent2 it is itself--a compound of perfectly identical particles4 ,every 8compound0 body1 therefore1 must be made up of some of the elements1 of which there are sixty-five4 ,these bodies are divided into non-metallic and metallic elements1 and all bodies are composed of them1 or are these bodies themselves4 ,the list is as follows4 ,the non-metallic elements are 8metalloids40 ,we have omitted fractions from the weights1 on which chemists differ4 ,,table ,,of ,,elements ,,with ,,their ,,chemical ,,symbols ,,and ,,combining ,,weights4 ,non-,metallic ,atomic or ,elements4 ,symbols4 ,combining ,derivation of ,name4 ,weights4 ,oxygen ,o #af ,gr4 ,oxus1 acid2 genna1 to make4 ,hydrogen ,h #a ,gr4 ,udor1 water2 genna1 to make4 ,nitrogen ,gaseous ,n #ad ,gr4 ,natron1 nitre2 genna1 to make4 ,chlorine ,cl #ce ,gr4 ,chloros1 green4 ,iodine ,i #abg ,gr4 ,ioeides1 violet4 ,fluorine ,f #ai ,fluor spar1 the mineral4 ,carbon ,c #ab ,lat4 ,carbo1 coal4 ,sulphur ,s #cb ,lat4 ,sulphurium4 ,phosphorus ,p #ca ,gr4 ,phos1 light2 pherein1 to carry4 ,arsenic99 ,solid ,as #ge ,gr4 ,arsenicon1 potent4 ,silicon ,si #bh ,gr4 ,silex1 flint4 ,boron ,b #aa ,gr4 ,borax1 ,arab41 baraga1 to shine4 ,selenium ,se #gi ,gr4 ,selene1 the moon4 ,tellurium ,te #abi ,lat4 ,tellus1 the earth4 ,bromine ,fluid #hj ,gr4 ,bromos1 offensive smell4 ,,metals4 ,name4 ,symbols4 ,atomic or ,derivation4 ,combining ,weights4 ,aluminium ,al #bg ,lat4 ,alumen1 alum4 ,antimony 7,stibium7 ,sb #abb ,gr4 ,anti1 against2 minos1 one4 ,arsenic ,as #ge 7,not known47 ,barium ,ba #acg ,gr4 ,bars1 heavy4 ,bismuth ,bi #baj ,ger4 ,weissmuth1 white matter4 ,cadmium ,cd #aab ,gr4 ,cadmeia1 calamite4 ,csium ,cs #acc ,lat4 ,csius1 sky-blue4 ,calcium ,ca #dj ,lat4 ,calx1 lime4 ,cerium ,ce #ada ,the planet ,ceres4 ,chromium ,cr #eb ,gr4 ,chroma1 colour4 ,cobalt ,co #eh ,ger4 ,kobald1 a sprite4 ,copper ,cu #fc ,lat4 ,cuprum 7,cyprium71 ,cyprus4 ,didymium ,d #adg ,gr4 ,didumos1 twins4 ,erbium ,e -- ,ytterby in ,sweden4 ,gallium ,ga #gj 7,not known47 ,glucinum ,gl #i ,gr4 ,glukos1 sweet4 ,gold ,au #aig ,from ,hebrew1 to shine 7doubtful74 ,indium ,in #aac ,indigo colour4 ,iridium ,ir #aih ,gr4 ,iris1 rainbow4 ,iron ,fe #ef ,hebrew1 to meet 7doubtful74 ,lanthanum ,la #aci ,gr4 ,lanthanein1 to lie hid4 ,lead ,pb #bjg 7,plumbum7 malubodos 7galena74 ,lithium ,li #g ,gr4 ,lithos1 stone4 ,magnesium ,mg #bd ,magnesia1 ,asia ,minor4 ,manganese ,mn #ee ,mangana1 ,e4 ,i4 7or ,magnesia74 ,mercury ,hg #bjj ,heathen deity 7quick74 ,molybdenum ,mo #if ,gr4 ,molybdena1 lead ore1 like lead4 ,nickel ,ni #eh ,ger4 ,kupfer nikel1 false copper4 ,niobium 7,columbium7 ,nb #id ,columbite4 ,osmium ,os #aii ,osme1 an odour4 ,palladium ,pl #ajf ,pallas1 ,minerva4 ,platinum ,pt #aig ,spanish1 platina1 little silver4 ,potassium 7,kalium7 ,k #ci ,potash4 ,rhodium ,rh #ajd ,gr4 ,roda1 rose4 ,rubidium ,rb #he ,lat4 ,rubidus1 red4 ,ruthenium ,ru #ajd 7,not known47 ,silver 7,argentum7 ,ag #ajh ,hebrew1 money4 ,sodium 7,natrium7 ,na #bc ,salsoda plant4 ,strontium ,sr #hg ,strontian1 ,n4,b4 ,tantalum ,ta #ahb ,tantalite mineral4 ,terbium ,tr -- 7,not known47 ,thallium ,tl #bjd ,gr4 ,thallos1 green twig4 ,thorium ,th #bcj ,thor1 deity4 ,tin 7,stannum7 ,sn #aah 7,not known47 ,titanium ,ti #ej ,titans4 ,tungsten 7,wolfram7 ,w #ahd ,swedish4 ,uranium ,u #bdj ,urania4 ,vanadium ,v #ea ,vanadis1 a goddess in ,sweden1 etc4 ,yttrium ,y #ic 7,not known47 ,zinc ,zn #fe ,ger4 ,zinken1 nails4 ,zirconium ,zr #hi ,ger4 ,zircon1 four-cornered 7,ceylon74 99,arsenic is sometimes considered a non-metallic and sometimes a metallic substance4 ,the term 8combining weight0 requires a little explanation4 ,we are aware that water1 for instance1 is made up of oxygen and hydrogen in certain proportions4 ,this we will prove by-and-by4 ,the proportions are in eighteen grains or parts of water1 sixteen parts 7by weight7 of oxygen1 and two parts 7by weight7 of hydrogen4 ,these are the weights or proportions in which oxygen and hydrogen combine to form water1 and such weights are always the same in these proportions4 ,chemical combination always occurs for certain substances in certain proportions which never vary in those compounds1 and if we wish to extract oxygen from an oxide we must take the aggregate amount of the combining weights of the oxide1 and we shall find the proportion of oxygen2 for the compound always weighs the same as the sum of the elements that compose it4 ,to return to the illustration of water4 ,the molecule of water is made up of one atom of oxygen and two atoms of hydrogen4 ,one atom of the former weighs sixteen times the atom of the latter4 ,the weights given in the foregoing table are atomic weights1 and the law of their proportions is called the ,atomic ,theory4 ,an atom in chemistry is usually considered the smallest quantity of matter that exists1 and is indivisible4 ,a molecule is supposed to contain two or more atoms1 and is the smallest portion of a compound body4 ,the standard atom is hydrogen1 which is put down as #a1 because we find that when one part by weight of hydrogen is put in combination1 it must have many more parts by weight of others to form a compound4 ,two grains of hydrogen1 combining with sixteen of oxygen1 makes eighteen of water1 as we have already seen4 ,take an example so plainly given by ,professor ,roscoe1 remembering that the numbers in our table represent the fixed weight or proportion by weight in which the simple body combines4 ,the red oxide of mercury contains sixteen parts by weight of oxygen to two hundred parts by weight of mercury 7we see the same numbers in the table72 these combined make two hundred and sixteen parts of oxide4 ,so to obtain #af lbs4 of oxygen we must get #baf lbs4 of the powder4 ,it is the same all through1 and it will be found by experiment that if any more parts than these fixed proportions be taken to form a compound1 some of that element used in excess will remain free4 ,lime is made up of calcium and oxygen4 ,we find calcium combining weight is forty1 oxygen sixteen4 ,lime is oxide of calcium in these proportions 7by weight74 ,when we wish to express the number of atoms in a compound we write the number underneath when more than one2 thus water is ,h#b,o4 ,sulphuric acid ,h#b,,so#d4 ,as we proceed we will give the various formul when considering the chief elements4 ,in chemistry we have acids1 alkalis1 and salts1 with metallic oxides1 termed bases1 or bodies1 that when combined with acids form salts4 ,alkalis are bases4 ,,acids are compounds which possess an acid taste1 impart red colour to vegetable blues1 but lose their qualities when combined with bases4 ,hydrogen is present in all acids4 ,there are insoluble acids4 ,silicic acid1 for instance1 is not soluble in water1 has no sour taste1 and will not redden the test litmus paper4 ,on the other hand1 there are substances 7not acids7 which possess the characteristics of acids1 and most acids have only one or two of these characteristics4 ,thus it has come to pass that the term 8acid0 has in a measure dropped out from scientific nomenclature1 and salt of hydrogen has been substituted by chemists4 ,for popular exposition1 however1 the term is retained4 ,,alkalis are bases distinguished by an alkaline taste4 ,the derivation is from ,arabic1 al-kali4 ,they are characterized by certain properties1 and they change vegetable blues to green1 and will restore the blue to a substance which has been reddened by acid4 ,they are soluble in water1 and the solutions are caustic in their effects4 ,potash1 soda1 and ammonia are alkalis1 or chemically1 the oxides of potassium1 sodium1 ammonium1 lithium1 and csium are all alkalis4 ,potash is sometimes called 8caustic0 potash4 ,there are alkaline earths1 such as oxides of barium1 strontium1 etc4 ,bases may be defined as the converse of acids4 ,acids and alkalis are then evidently opposite in character1 and yet they readily combine1 and in chemistry we shall find that unlike bodies are very fond of combining 7just as opposite electricities attract each other71 and the body made by this combination differs in its properties from its constituents4 ,,salts are composed of acids and bases1 and are considered neutral compounds1 but there are other bodies not salts1 which likewise come under that definition--sugar1 for instance4 ,as a rule1 when acids and alkalis combine salts are found4 ,chemical phenomena are divided into two groups1 called inorganic and organic1 comprising the simple and compound aspects of the subject1 the elementary substances being in the first1 and the chemistry of animals or vegetables1 or organic substances1 in the latter4 ,in the inorganic section we shall become acquainted with the elements and their combinations so often seen as minerals in nature4 ,chemical preparations are artificially prepared4 ,to consider these elements we must have certain appliances1 and indeed a laboratory is needed4 ,heat1 as we have already seen1 plays a great part in developing substances1 and by means of heat we can do a great deal in the way of chemical decomposition4 ,it expands1 and thus diminishes cohesion2 it counteracts the chemical attraction4 ,light and electricity also decompose chemical combinations4 ,but before proceeding it will be as well to notice a few facts showing how ,nature has balanced all things4 ,the earth1 and its surrounding envelope1 the atmosphere1 consist of a number of elements1 which in myriad combinations give us everything we possess1--the air we breathe1 the water we drink1 the fire that warms us1 are all made up of certain elements or gases4 ,water1 hydrogen and oxygen2 air1 oxygen and nitrogen4 ,fire is combustion evolving light and heat4 ,chemical union always evolves heat1 and when such union proceeds very rapidly fire is the result4 ,in all these combinations we shall find when we study chemistry that not a particle or atom of matter is ever lost4 ,it may change or combine or be 8given off10 but the matter in some shape or way exists still4 ,we may burn things1 and rid ourselves1 as we think1 of them4 ,we do rid ourselves of the compounds1 the elements remain somewhere4 ,we only alter the condition4 ,during combustion1 as in a candle or a fire1 the simple bodies assume gaseous or other forms1 such as carbon1 but they do not escape far4 ,true they pass beyond our ken1 but nature is so nicely balanced that there is a place for everything1 and everything is in its place under certain conditions which never alter4 ,we cannot destroy and we cannot create4 ,we may prepare a combination1 and science has even succeeded in producing a form like the diamond--a crystal of carbon which looks like that most beautiful of all crystals1 but we cannot make a diamond after all4 ,we can only separate the chemical compounds4 ,we can turn diamonds into charcoal it is true1 but we cannot create 8natural0 products4 ,we can take a particle of an element and hide it1 or let it pass beyond our ken1 and remain incapable of detection1 but the particle is there all the time1 and when we retrace our steps we shall find it as it was before4 ,this view of chemistry carries it as a science beyond the mere holiday amusement we frequently take it to be4 ,it is a grand study1 a study for a lifetime4 ,nature is always willing1 like a kind1 good mother as she is1 to render us up her secrets if we inquire respectfully and lovingly4 ,the more we inquire the more we shall find we have to learn4 ,in these and the following pages we can only tell you a few things1 but no one need be turned away because he does not find all he wants4 ,we never do get all we want in life1 and there are many first-rate men--scientists--who would give 8half their kingdom0 for a certain bit of knowledge concerning some natural phenomena4 ,there are numerous excellent treatises on chemistry1 and exhaustive as they are1 at present they do not tell us all4 ,let these popular pages lead us to the study of nature1 and we shall find our labour far from onerous and full of interest1 daily increasing to the end1 when we shall know no more of earth1 or chemistry4 ,as a preliminary we will put our workshop aside1 and show you something of ,chemistry without a ,laboratory4 ,,chapter ,,xxv4 ,,chemistry ,,without ,a ,,laboratory4 ,we have already pointed out the possibility of going through a course of physics without any special apparatus1 we shall now endeavour to show our readers the method of performing some experiments in chemistry without a laboratory1 or at any rate with only a few simple and inexpensive appliances4 ,the preparation of gases1 such as hydrogen1 carbonic acid1 and oxygen1 is very easily accomplished1 but we shall here point out principally a series of experiments that are not so much known4 ,we will commence1 for example1 by describing an interesting experiment which often occurs in a course of chemistry4 ,ammoniacal gas combined with the elements of water is analogous to a metallic oxide which includes a metallic root1 ammonium4 ,this hypothetically composed metal may be in a manner perceived1 since it is possible to amalgamate it with mercury by operating in the following manner3--,we take a porcelain mortar1 in which we pour a quantity of mercury1 and then cut some thin strips of sodium1 which are thrown into the mercury4 ,by stirring it about with the pestle a loud cracking is produced1 accompanied by a flame1 which bears evidence to the union of the mercury and the sodium1 and the formation of an amalgam of sodium4 ,if this amalgam of sodium is put into a slender glass tube containing a concentrated solution of hydrochlorate of ammonia in water1 we see the ammonia expand in an extraordinary manner1 and spout out from the end of the tube1 which is now too small to contain it1 in the form of a metallic substance 7fig4 #cjb74 ,in this case1 the ammonium1 the radical which exists in the ammoniacal salts1 becomes amalgamated with the mercury1 driving out the sodium with which it had previously been combined2 the ammonium thus united with the mercury becomes decomposed in ammoniacal gas and hydrogen1 the mercury assuming its ordinary form4 ,phosphate of ammonia is very valuable from its property of rendering the lightest materials1 such as gauze or muslin1 incombustible4 ,dip a piece of muslin in a solution of phosphate of ammonia1 and dry it in contact with the air2 that done1 you will find it is impossible to set fire to the material2 it will get charred1 but you cannot make it burn4 ,it is to be wished that this useful precaution were oftener taken in the matter of ball-dresses1 which have so frequently been the cause of serious accidents4 ,there is no danger whatever with a dress that has been soaked in phosphate of ammonia1 which is very inexpensive1 and easily procured4 ,illustration3 ,fig4 #cjb4--;,experiment with ammonium4 ,for preparing cool drinks in the summer ammoniacal salts are very useful2 some nitrate of ammonia mixed with its weight in water1 produces a considerable lowering of the temperature1 and is very useful for making ice4 ,volatile alkali1 which is so useful an application for stings from insects1 is a solution of ammoniacal gas in water1 and sal-volatile1 which has such a refreshing and reanimating odour1 is a carbonate of ammonia4 ,we often see in chemists' shops large glass jars1 the insides of which are covered with beautiful transparent white crystals1 which are formed over a red powder placed at the bottom of the vase4 ,these crystals are the result of a combination of cyanogen and iodine4 ,nothing is easier than the preparation of iodide of cyanogen1 a very volatile body1 which possesses a strong tendency to assume a definite crystalline form4 ,we pound in a mortar a mixture of #ej grams of cyanide of mercury1 and #ajj grams of iodine2 under the action of the pestle the powder1 which was at first a brownish colour1 assumes a shade of bright vermilion red4 ,the cyanogen combines with the iodine1 and transforms itself into fumes with great rapidity4 ,if the powder is placed at the bottom of a stoppered glass jar1 the fumes of the iodide of cyanogen immediately condense1 thereby producing beautiful crystals which often attain considerable size 7fig4 #cjc74 ,cyanogen forms with sulphur a remarkable substance1 sulpho-cyanogen1 the properties of which we cannot describe without exceeding the limits of our present treatise2 we shall therefore confine ourselves to pointing out one of its combinations1 which is well known at the present day1 owing to its singular properties4 ,this is sulpho-cyanide of mercury1 with which small combustible cones are made1 generally designated by the pompous title of ,pharaoh's serpents4 ,for making these1 some sulpho-cyanide of potassium is poured into a solution of nitrate acid on mercury1 which forms a precipitate of sulpho-cyanide of mercury4 ,this is a white1 combustible powder1 which after passing through a filter1 should be transformed into a stiff pulp by means of water containing a solution of gum4 ,the pulp is afterwards mixed with a small quantity of nitrate of potash1 and fashioned into cones or cylinders of about an inch and a quarter in length1 which should be thoroughly dried4 ,the egg thus obtained can be hatched by the simple application of a lighted match1 and gives rise to the phenomenon4 ,the sulpho-cyanide slowly expands1 the cylinder increases in length1 and changes to a yellowish substance1 which dilates and extends to a length of twenty or five-and-twenty inches4 ,it has the appearance of a genuine serpent1 which has just started into existence1 and stretches out its tortuous coils1 endeavouring to escape from its narrow prison 7fig4 #cjd74 ,the residue is composed partly of cyanide of mercury and of para-cyanogen2 it constitutes a very poisonous substance1 which should be immediately thrown away or burned4 ,it can be easily powdered into dust in the fingers4 ,during the decomposition of the sulpho-cyanide of mercury1 quantities of sulphurous acid are thrown off1 and it is to be regretted that ,pharaoh's serpent should herald his appearance by such a disagreeable1 suffocating odour4 ,illustration3 ,fig4 #cjc4--;,iodide of cyanogen4 ,illustration3 ,fig4 #cjd4--,pharaoh's serpent4 ,after these few preliminary experiments1 we will endeavour to show the interest afforded by the study of chemistry in relation to the commonest substances of every-day life4 ,we will first consider the nature of a few pinches of salt4 ,we know that kitchen salt1 or sea salt1 is white or greyish1 according to its degree of purity2 that it has a peculiar flavour1 is soluble in water1 and makes a peculiar crackling when thrown in the fire4 ,but though its principal physical properties may be familiar enough1 many people are entirely ignorant of its chemical nature and elementary composition4 ,kitchen salt contains a metal1 combined with a gas possessing a very suffocating odour2 the metal is sodium1 the gas is chlorine4 ,the scientific name for the substance is chloride of sodium 7salt74#ai ,the metal contained in common salt in no way resembles ordinary metals2 it is white like silver1 but tarnishes immediately in contact with air1 and unites with oxygen1 thus transforming itself into oxide of sodium4 ,to preserve this singular metal it is necessary to protect it from the action of the atmosphere1 and to keep it in a bottle containing oil of naptha4 ,sodium is soft1 and it is possible with a pair of scissors to cut it like a ball of soft bread that has been kneaded in the hand4 ,it is lighter than water1 and when placed in a basin of water floats on the top like a piece of cork2 only it is disturbed1 and takes the form of a small brilliant sphere2 great effervescence is also produced as it floats along1 for it reduces the water to a common temperature by its contact4 ,by degrees the small metallic ball disappears from view1 after blazing into flame 7fig4 #cje74 ,illustration3 ,fig4 #cje4--;,combustion of sodium in water4 ,this remarkable experiment is very easy to carry out1 and sodium is now easily procured at any shop where chemicals are sold4 ,the combustion of sodium in water can be explained in a very simple manner4 ,water1 as we know1 is composed of hydrogen and oxygen4 ,sodium1 by reason of its great affinity for the latter gas1 combines with it1 and forms a very soluble oxide2 the hydrogen is released and thrown off1 as we shall perceive by placing a lighted match in the jar1 when the combustible gas ignites4 ,oxide of sodium has a great affinity for water2 it combines with it1 and absorbs it in great quantities4 ,it is a solid1 white substance1 which burns and cauterizes the skin2 it is also alkaline1 and brings back the blue colour to litmus paper that has been reddened by acids4 ,sodium combines easily also with chlorine4 ,if plunged into a jar containing this gas it is transformed into a substance1 which is sea salt4 ,if the chlorine is in excess a part of the gas remains free1 for simple substances do not mingle in undetermined ratios2 they combine1 on the contrary1 in very definite proportions1 and #cee gr4 of dry chlorine always unites with the same quantity of soda equal to #bc grams4 ,a gram of kitchen salt is formed1 therefore1 of #jfjf gr4 of chlorine1 and #jcid gr4 of sodium4 ,besides sea salt1 there are a number of different salts which may be made the object of curious experiments4 ,we know that caustic soda1 or oxide of sodium1 is an alkaline product possessing very powerful properties2 it burns the skin1 and destroys organic substances4 ,sulphuric acid is endowed with no less powerful properties2 if a little is dropped on the hand it produces great pain and a sense of burning2 a piece of wood plunged into this acid is almost immediately carbonized4 ,if we mix forty-nine grams of sulphuric acid and thirty-one grams of caustic soda a very intense reaction is produced1 accompanied by a considerable elevation of temperature2 after it has cooled we have a substance which can be handled with impunity2 the acid and alkali have combined1 and their properties have been reciprocally destroyed4 ,they have now originated a salt which is sulphate of soda4 ,this substance exercises no influence on litmus paper1 and resembles in no way the substances from which it originated4 ,there are an infinite number of salts which result in like manner from the combination of an acid with an alkali or base4 ,some1 such as sulphate of copper1 or chromate of potash1 are coloured2 others1 like sulphate of soda1 are colourless4 ,the last-mentioned salt1 with a number of others1 will take a crystalline form2 if dissolved in boiling water1 and the solution left to stand1 we shall perceive a deposit of transparent prisms of very remarkable appearance4 ,this was discovered by ,glauber1 and was formerly called ,glauber's salts4 ,illustration3 ,fig4 #cjf4--,preparation of a solution saturated with sulphate of soda4 ,sulphate of soda is very soluble in water1 and at a temperature of thirty-three 7,centigr47 water can dissolve it in the greatest degree4 ,if we pour a layer of oil on a solution saturated with ,glauber's salts1 and let it stand1 it will not produce crystals2 but if we thrust a glass rod through the oil into contact with the solution1 crystallization will be instantaneous4 ,this singular phenomenon becomes even more striking when we put the warm concentrated solution into a slender glass tube1 ,a ,b1 which we close after having driven out the air by the bubbling of the liquid 7fig4 #cjf74 ,when the tube has been closed1 the crystals of sulphate of soda will not form1 even with the temperature at zero2 nevertheless the salts1 being less soluble cold than hot1 are found in the fluid in a proportion ten times larger than they would contain under ordinary conditions4 ,if the end of the tube be broken the salt will crystallize immediately4 ,we will describe another experiment1 but little known and very remarkable1 which exhibits in a striking manner the process of instantaneous crystallizations4 ,let one hundred and fifty parts of hyposulphite of soda be dissolved in fifteen parts of water1 and the solution slowly poured into a test-glass1 previously warmed by means of boiling water1 until the vessel is about half-full4 ,one hundred parts of acetate of soda is then dissolved in fifteen parts of water1 and poured slowly into the first solution1 so that they form two layers perfectly distinct from each other4 ,the two solutions are then covered with a little boiling water1 which1 however is not represented in our illustration4 ,after it has been left to stand and cool slowly1 we have two solutions of hyposulphite of soda and acetate of soda superposed on each other4 ,a thread1 at the end of which is fixed a small crystal of hyposulphite of soda1 is then lowered into the test-glass2 the crystal passes through the solution of acetate without disturbing it1 but it has scarcely reached the lower solution of hyposulphite than the salt crystallizes instantaneously4 7,see the test-glass on the left of fig4 #cjg47 ,we then lower into the upper solution a crystal of acetate of soda1 suspended from another thread4 ,this salt then crystallizes also4 7,see experiment glass on the right of fig4 #cjg47 ,this very successful experiment is one of the most remarkable belonging to the subject of instantaneous crystals4 ,the successive appearance of crystals of hyposulphite of soda1 which take the form of large1 rhomboidal prisms1 terminating at the two extremities with an oblique surface1 and the crystals of acetate of soda1 which have the appearance of rhomboidal1 oblique prisms1 cannot fail to strike the attention and excite the interest of those who are not initiated into these kinds of experiments4 ,illustration3 ,fig4 #cjg4--;,experiment of instantaneous crystallization4 ,another remarkable instantaneous crystallization is that of alum4 ,if we leave standing a solution of this salt it gradually cools1 at the same time becoming limpid and clear4 ,when it is perfectly cold1 if we plunge into it a small octahedral crystal of alum suspended from a thread1 we perceive that crystallization instantly commences on the surface of the small crystal2 it rapidly and perceptibly increases in size1 until it nearly fills the whole jar4 ,,common ,,metals ,,and ,,precious ,,metals4 ,how many invalids have swallowed magnesia without suspecting that this powder contains a metal nearly as white as silver1 and is malleable1 and capable of burning with so intense a light that it rivals even the electric light in brilliancy6 ,if any of our readers desire to prepare magnesium themselves it can be done in the following manner3--,some white magnesia must be obtained from the chemist1 and after having been calcined1 must be submitted to the influence of hydrochloric acid and hydrochlorate of ammonia4 ,a clear solution will thus be obtained1 which by means of evaporation under the influence of heat1 furnishes a double chloride1 hydrated and crystallised4 ,this chloride1 if heated to redness in an earthenware crucible1 leaves as a residue a nacreous product1 composed of micaceous1 white scales1 chloride of anhydrous magnesium4 ,illustration3 ,fig4 #cjh4--;,group of alum crystals4 ,if six hundred grams of this chloride of magnesium are mixed with one hundred grams of chloride of sodium1 or kitchen salt1 and the same quantity of fluoride of calcium and metallic sodium in small fragments1 and the mixture is put into an earthenware crucible made red-hot1 and heated for a quarter of an hour under a closed lid1 we shall find on pouring out the fluid on to a handful of earth1 that we have obtained instead of scoria1 forty-five grams of metallic magnesium4 ,the metal thus obtained is impure1 and to remove all foreign substances it must be heated in a charcoal tube1 through which passes a current of hydrogen4 ,magnesium is now produced in great abundance1 and is very inexpensive4 ,it is a metal endowed with a great affinity for oxygen1 and it is only necessary to thrust it into the flame of a candle to produce combustion2 it burns with a brightness that the eye can scarcely tolerate1 and is transformed into a white powder--oxide of magnesium1 or magnesia4 ,combustion is still more active in oxygen1 and powder of magnesium placed in a jar filled with this gas produces a perfect shower of fire of very beautiful effect4 ,to give an idea of the lighting power of magnesium1 we may add that a wire of this metal1 which is #bi_/ajj of a millimetre in diameter1 produces by combustion a light equal to that of seventy-four candles4 ,illustration3 ,fig4 #cji4--;,calcined alum4 ,illustration3 ,fig4 #caj4--,preparation of metallic iron4 ,the humble earth of the fields--the clay which is used in our potteries1 also contains aluminium1 that brilliant metal which is as malleable as silver1 and unspoilable as gold4 ,when clay is submitted to the influence of sulphuric acid and chloride of potassium1 we obtain alum1 which is a sulphate of alumina and potash4 ,alum is a colourless salt1 which crystallizes on the surface of water in beautiful octahedrons of striking regularity4 ,fig4 #cjh represents a group of alum crystals4 ,this salt is much used in the colouring of fabrics2 it is also used for the sizing of papers1 and the clarification of tallow4 ,doctors also use it as an astringent and caustic substance4 ,when alum is submitted to the action of heat in an earthenware crucible1 it loses the water of crystallization which it contains1 and expands in a singular manner1 overflowing from the jar in which it is calcined 7fig4 #cji74 ,iron1 the most important of common metals1 rapidly unites with oxygen1 and1 as we know1 when a piece of this metal is exposed to the influence of damp air1 it becomes covered with a reddish substance4 ,in the well-known experiment of the formation of rust1 the iron gradually oxidises without its temperature rising1 but this combination of iron with oxygen is effected much more rapidly under the influence of heat4 ,if1 for example1 we redden at the fire a nail attached to a wire1 and give it a movement of rotation as of a sling1 we see flashing out from the metal a thousand bright sparks due to the combination of iron with oxygen1 and the formation of an oxide4 ,particles of iron burn spontaneously in contact with air1 and this property for many centuries has been utilized in striking a tinder-box2 that is to say1 in separating1 by striking a flint1 small particles of iron1 which ignite under the influence of the heat produced by the friction4 ,we can prepare iron in such atoms that it ignites at an ordinary temperature by simple contact with the air4 ,to bring it to this state of extreme tenuity1 we reduce its oxalate by hydrogen4 ,we prepare an apparatus for hydrogen as shown in fig4 #caj1 and the gas produced at ,a is passed through a desiccative tube1 ,b1 and finally reaches a glass receptacle1 ,c1 in which some oxalate of iron is placed4 ,the latter salt1 under the combined influence of hydrogen and heat1 is reduced to metallic iron1 which assumes the appearance of a fine black powder4 ,when the experiment is completed the glass vessel is closed1 and the iron1 thus protected from contact with the air1 can be preserved indefinitely2 but if it is exposed to the air by breaking off the end of the receptacle 7fig4 #caa71 it ignites immediately1 producing a shower of fire of very beautiful effect4 ,iron thus prepared is known under the name of pyrophoric iron4 ,iron is acted upon in a very powerful manner by most acids4 ,if some nitric acid is poured on iron nails1 a stream of red1 nitrous vapour is let loose1 and the oxidised iron is dissolved in the liquid to the condition of nitrate of iron4 ,this experiment is very easy to perform1 and it gives an idea of the energy of certain chemical actions4 ,we have endeavoured to represent its appearance in fig4 #cab4 ,fuming nitric acid does not act on iron1 and prevents it being attacked by ordinary nitric acid4 ,this property has given rise to a very remarkable experiment on passive iron4 ,it consists in placing some nails in a glass1 into which some fuming nitric acid is poured1 which produces no result2 the fuming acid is then taken out1 and is replaced by ordinary nitric acid1 which no longer acts on the iron rendered passive by the smoking acid4 ,after this1 if the nails are touched by a piece of iron1 which has not undergone the action of nitric acid1 they are immediately acted upon1 and a giving off of nitrous vapour is manifested with great energy4 ,lead is a very soft metal1 and can even be scratched by the nails4 ,it is also extremely pliable1 and so entirely devoid of elasticity that when bent it has no tendency whatever to return to its primitive form4 ,lead is heavy1 and has a density represented by #aad2 that is to say1 the weight of a quart of water being one kilogram1 that of the same volume of lead is #aadjj k4 ,illustration3 ,fig4 #caa4--,pyrophoric iron4 ,fig4 #cac represents cylindrical bars of the best known metals1 all weighing the same1 showing their comparative density4 ,illustration3 ,fig4 #cab4--;,iron and nitric acid4 ,lead1 like tin1 is capable of taking a beautiful crystalline form when placed in solution by a metal that is less oxydisable4 ,the crystallization of lead1 represented in fig4 #cad1 is designated by the name of the ,tree of ,saturn4 ,this is how the experiment is produced3 ,thirty grams of acetate of lead are dissolved in a quart of water1 and the solution is poured into a vase of a spherical shape4 ,a stopper for this vase is made out of a piece of zinc1 to which five or six separate brass wires are attached2 these are plunged into the fluid1 and we see the wires become immediately covered with brilliant crystallized spangles of lead1 which continue increasing in size4 ,the alchemists1 who were familiar with this experiment1 believed that it consisted in a transformation of copper into lead1 while in reality it only consists in the substitution of one metal for another4 ,the copper is dissolved in the liquid1 and is replaced by the lead1 but no metamorphosis is brought about4 ,we may vary at will the form of the vase or the arrangement of the wire2 thus it is easy to form letters1 numbers1 or figures1 by the crystallization of brilliant spangles4 ,illustration3 ,platinum ,density #ba4ej ,gold ,d4 #ai4be ,mercury ,d4 #ac4ef ,lead ,d4 #aa4ce ,silver ,d4 #aj4dg ,bismuth ,d4 #i4hb ,copper ,d4 #h4gh ,nickel ,d4 #h4bg ,tin ,d4 #g4bi ,iron ,d4 #g4bj ,zinc ,d4 #f4hf ,aluminium ,d4 #b4ef ,magnesium ,d4 #a4dc ,sodium ,d4 #j4ig ,fig4 #cac4--,representation of bars of metal1 all of the same weight4 ,copper1 when it is pure1 has a characteristic red colour1 which prevents it being confounded with any other metal2 it dissolves easily in nitric acid1 and with considerable effervescence1 giving off vapour very abundantly4 ,this property has been put to good use in engraving with aqua fortis4 ,a copper plate is covered with a layer of varnish1 and when it is dry some strokes are made on it by means of a graver2 if nitric acid is poured on the plate when thus prepared1 the copper is only acted on in the parts that have been exposed by the point of steel4 ,by afterwards removing the varnish1 we have an engraved plate1 which will serve for printing purposes4 ,illustration3 ,fig4 #cad4--,tree of ,saturn4 ,among experiments that may be attempted with common metals1 we may mention that in which salts of tin are employed4 ,tin has a great tendency to assume a crystalline form1 and it will be easy to show this property by an interesting experiment4 ,a concentrated solution of proto-chloride of tin1 prepared by dissolving some metallic tin in hydrochloric acid1 is placed in a test glass2 then a rod of tin is introduced1 as shown in fig4 #cae4 ,some water is next slowly poured on the rod1 so that it gradually trickles down1 and prevents the mingling of the proto-chloride of tin4 ,the vessel is then left to stand1 and we soon see brilliant crystals starting out from the rod4 ,this crystallization is not effected in the water2 it is explained by an electric influence1 into the details of which we cannot enter without overstepping our limits2 it is known as 8,jupiter's ,tree40 ,it is well known that alchemists1 with their strange system of nomenclature1 believed there was a certain mysterious relation between the seven metals then known and the seven planets2 each metal was dedicated to a planet2 tin was called ,jupiter2 silver1 ,luna2 gold1 ,sol2 lead1 ,saturn2 iron1 ,mars2 quicksilver1 ,mercury2 and copper1 ,venus4 ,the crystallization of tin may be recognised also by rubbing a piece of this metal with hydrochloric acid2 the fragments thus rubbed off exhibit specimens of branching crystals similar to the hoar-frost which we see in severe winter weather4 ,if we bend a rod of tin in our hands the crystals break1 with a peculiar rustling sound4 ,when speaking of precious metals1 we may call to mind that the alchemists considered gold as the king of metals1 and the other valuable ones as noble metals4 ,this definition is erroneous1 if we look upon the useful as the most precious2 for1 in that case1 iron and copper would be placed in the first rank4 ,if gold were found abundantly on the surface of the soil1 and iron was extremely rare1 we should seek most eagerly for this useful metal1 and should despise the former1 with which we can neither make a ploughshare nor any other implement of industry4 ,nevertheless1 the scarcity of gold1 its beautiful yellow colour1 and its unalterability when in contact with air1 combine to place it in the first rank in the list of precious metals4 ,gold is very heavy2 its density is represented by the figure #aie4 ,it is the most malleable and the most ductile of metals1 and can be reduced by beating to such thin sheets that ten thousand can be laid1 one over the other1 to obtain the thickness of a millimetre4 ,with a grain of gold a thread may be manufactured extending a league in length1 and so fine that it resembles a spider's web4 ,when gold is beaten into thin sheets it is no longer opaque2 if it is fastened1 by means of a solution of gum1 on to a sheet of glass1 the light passes right through it1 and presents a very perceptible green shade4 ,gold is sometimes found scattered in sand1 in a condition of impalpable dust1 and1 in certain localities1 in irregular lumps of varying size1 called nuggets4 ,gold is the least alterable of the metals1 and can be exposed1 indefinitely1 to the contact of humid atmosphere without oxidizing4 ,it is not acted on by the most powerful acids1 and only dissolves in a mixture of nitric acid and hydrochloric acid4 ,we can prove that gold resists the influence of acids by the following operation3-- ,some gold-leaf is placed in two small phials1 the first containing hydrochloric acid1 and the second nitric acid4 ,the two vessels are warmed on the stove1 and whatever the duration of the ebullition of the acids1 the gold-leaf remains intact1 and completely resists their action4 ,if we then empty the contents of one phial into the other1 the hydrochloric and nitric acids are mixed1 and we see the gold-leaf immediately disappear1 easily dissolved by the action of the liquid 7aqua regia74 ,gold also changes when in contact with mercury2 this is proved by suspending some gold-leaf above the surface of this liquid 7fig4 #caf72 it quickly changes1 and unites with the fumes of the mercury1 becoming of a greyish colour4 ,silver is more easily affected than gold1 and though so white when fused1 tarnishes rapidly in contact with air4 ,it does not oxidize1 but sulphurizes under the influence of hydro-sulphuric emanations4 ,silver does not combine directly with the oxygen of the atmosphere2 but under certain conditions it can dissolve great quantities of this gas4 ,if it is fused in a small bone cupel1 in contact with the air1 and left to cool quickly1 it expands in a remarkable manner1 and gives off oxygen4 ,illustration3 ,fig4 #cae4--;,jupiter's ,tree4 ,nitric acid dissolves silver very easily1 by causing the formation of abundant fumes4 ,when the solution evaporates1 we perceive white crystals forming1 which are nitrate of silver4 ,this fused nitrate of silver takes the name of lunar caustic1 and is employed in medicine4 ,nitrate of silver is very poisonous2 it possesses the singular property of turning black under the action of the sun's rays1 and is used in many curious operations in photography4 ,it is also employed in the manufacture of dyes for the hair2 it is applied to white hair with gall-nut1 and under the influence of the light it turns black1 and gives the hair a very dark shade4 ,salts of silver in solution with water have the property of forming a precipitate under the influence of chlorides1 such as sea salt4 ,if a few grains of common salt are thrown into a solution of nitrate of silver1 it forms an abundant precipitate of chloride of silver1 which blackens in the light4 ,this precipitate1 insoluble in nitric acid1 dissolves very easily in ammonia4 ,platinum1 which is the last of the precious metals that we have to consider1 is a greyish-white colour1 and like gold is only affected by a mixture of nitric acid and hydrochloric acid4 ,it is the heaviest of all the ordinary metals2 its density is #baej4 ,it is very malleable and ductile1 and can be beaten into very thin sheets1 and into wires as slender as wires of gold4 ,platinum wires have even been made so fine that the eye can scarcely perceive them2 these are known as ,wollaston's invisible wires4 ,platinum resists the action of the most intense fire1 and we can only fuse it by means of a blow-pipe and hydro-oxide gas4 ,its inalterability and the resistance it opposes to fire render it very valuable for use in the laboratory4 ,small crucibles are made of it1 which are used by chemists to calcine their precipitates in analytical operations1 or to bring about reactions under the influence of a high temperature4 ,platinum may be reduced to very small particles2 it then takes the form of a black powder4 ,in this pulverulent condition it absorbs gases with great rapidity1 to such an extent that a cubic centimetre can condense seven hundred and fifty times its own volume of hydrogen gas4 ,it also condenses oxygen1 and in a number of cases acts as a powerful agent4 ,platinum is also obtained in porous masses 78spongy platinum071 which produce phenomena of oxidation4 ,illustration3 ,fig4 #caf4--;,gold-leaf exposed to the fumes of mercury4 ,a very ingenious little lamp may be constructed which lights of itself without the help of a flame4 ,it contains a bell of glass1 which is filled with hydrogen gas1 produced by the action exercised by a foundation of zinc on acidulated water4 ,if the knob on the upper part of the apparatus is pressed1 the hydrogen escapes1 and comes in contact with a piece of spongy platinum1 which1 acting by oxidation1 becomes ignited4 ,the flame produced sets fire to a small oil lamp1 which is opposite the jet of gas4 ,this very ingenious lamp is known under the name of ,gay-,lussac's lamp4 ,platinum can also produce1 by mere contact1 a great number of chemical reactions4 ,place in a test glass an explosive mixture formed of two volumes of hydrogen and one volume of oxygen2 in this gas plunge a small piece of spongy platinum1 and the combination of the two bodies will be instantly brought about1 making a violent explosion4 ,make a small spiral of platinum red-hot in the flame of a lamp1 having suspended it to a card2 then plunge it quickly into a glass containing ether1 and you will see the metallic spiral remain red for some time1 while in the air it would cool immediately4 ,this phenomenon is due to the action of oxidation which the platinum exercises over the fumes of ether4 ,this curious experiment is known under the name of the lamp without a flame4 ,this remarkable oxidizing power of platinum1 which has not yet been explained1 was formerly designated by the title of catalytic action4 ,but a phrase is not a theory1 and it is always preferable to avow one's ignorance than to simulate an apparent knowledge4 ,science is powerful enough to be able to express her doubts and uncertainties boldly4 ,in observing nature we find an experience of this1 and often meet with facts which may be put to profit1 and become useful in application2 nevertheless it is often the case that the why and the wherefore will for a long time escape the most penetrating eye and lucid intelligence4 ,it is true the admirable applications of science strike us with the importance of their results1 and the wonderful inventions they originate2 but if they turn to account the observed facts of nature1 what do they teach us as to the first cause of all things1 the wherefore of nature8--,almost nothing4 ,we must humbly confess our powerlessness1 and say with d',alembert3 8,the encyclopdia is very abundant1 but what of that if it discourses of what we do not understand80 ,illustration3 ,fig4 #cag4--;,discolouration of periwinkles by sulphuric acid4 ,,artificial ,,colouring ,,of ,,flowers4 ,in a course of chemistry1 the action exercised by sulphurous acid on coloured vegetable matter is proved by exposing violets to the influence of this gas1 which whitens them instantaneously4 ,sulphurous acid1 by its dis-oxidating properties1 destroys the colour of many flowers1 such as roses1 periwinkles1 etc4 ,the experiment succeeds very readily by means of the little apparatus which we give in fig4 #cag4 ,we dissolve in a small vessel some sulphur1 which ignites in contact with air1 and gives rise1 by its combination with oxygen1 to sulphurous acid2 the capsule is covered with a conical chimney1 made out of a thin sheet of copper1 and at the opening at the top the flowers that are to be discoloured are placed4 ,the action is very rapid1 and a few seconds only are necessary to render roses1 periwinkles1 and violets absolutely white4 ,illustration3 ,fig4 #cah4--;,experiment for turning columbines a green colour with ammoniacal ether4 ,m4 ,filpol1 a distinguished savant1 has exhibited to the members of the ,scientific ,association1 ,paris1 the results which he obtained by subjecting flowers to the influence of a mixture of sulphuric ether and some drops of ammonia2 he has shown that1 under the influence of this liquid1 a great number of violets or roses turn a deep green4 ,we have recently made on this subject a series of experiments which we will here describe1 and which may be easily attempted by those of our readers who are interested in the question4 ,some common ether is poured into a glass1 and to it is added a small quantity of liquid ammonia 7about one-tenth of the volume74 ,the flowers with which it is desired to experiment are then plunged into the fluid 7fig4 #cah74 ,a number of flowers1 whose natural colour is red or violet1 take instantaneously a bright green tint2 these are red geranium1 violet1 periwinkle1 lilac1 red and pink roses1 wall-flower1 thyme1 small blue campanula1 fumeter1 myosotis1 and heliotrope4 ,other flowers1 whose colours are not of the same shade1 take different tints when in contact with ammoniacal ether4 ,the upper petal of the violet sweet-pea becomes dark blue1 whilst the lower petal turns a bright green colour4 ,the streaked carnation becomes brown and bright green4 ,white flowers generally turn yellow1 such as the white poppy1 the variegated snow-dragon1 which becomes yellow and dark violet1 the white rose1 which takes a straw colour1 white columbine1 camomile1 syringa1 white daisy1 potatoe blossom1 white julian1 honeysuckle1 and white foxglove1 which in contact with ammoniacal ether assume more or less deep shades of yellow4 ,white snap-dragon becomes yellow and dark orange4 ,red geranium turns blue in a very remarkable fashion2 with the monkey-flower the ammoniacal ether only affects the red spots1 which turn a brownish green2 red snap-dragon turns a beautiful brown2 valerian takes a shade of grey2 and the red corn-poppy assumes a dark violet4 ,yellow flowers are not changed by ammoniacal ether2 buttercups1 marigolds1 and yellow snap-dragon preserve their natural colour4 ,leaves of a red colour are instantly turned green when placed in contact with ammoniacal ether4 ,the action of this liquid is so rapid that it is easy to procure green spots by pouring here and there a drop of the solution4 ,in like manner violet flowers1 such as periwinkles1 can be spotted with white1 even without gathering them4 ,we will complete our remarks on this subject with a description of experiments performed by ,m4 ,gabba in ,italy by means of ammonia acting on flowers4 ,m4 ,gabba simply used a plate1 in which he poured a certain quantity of solution of ammonia4 ,he placed on the plate a funnel turned upside down1 in the tube of which he arranged the flowers on which he wished to experiment4 ,he then found that under the influence of the ammonia the blue1 violet1 and purple flowers became a beautiful green1 red flowers black1 and white yellow1 etc4 ,the most singular changes of colour are shown by flowers which are composed of different tints1 their red streaks turning green1 the white yellow1 etc4 ,another curious example is that of red and white fuchsias1 which1 through the action of ammonia1 turn yellow1 blue1 and green4 ,when flowers have been subjected to these changes of colour1 and afterwards plunged into pure water1 they preserve their new tint for several hours1 after which they gradually return to their natural colour4 ,another interesting observation1 due to ,m4 ,gabba1 is that asters1 which are naturally inodorous1 acquire an agreeable aromatic odour under the influence of ammonia4 ,asters of a violet colour become red when wetted with nitric acid mixed with water4 ,on the other hand1 if these same flowers are enclosed in a wooden box1 where they are exposed to the fumes of hydrochloric acid1 they become1 in six hours' time1 a beautiful red colour1 which they preserve when placed in a dry1 shady place1 after having been properly dried4 ,hydrochloric acid has the effect of making flowers red that have been rendered green by the action of ammonia1 and also alters their appearance very sensibly4 ,we may also mention1 in conclusion1 that ammonia1 combined with ether1 acts much more promptly than when employed alone4 ,,phosphorescence4 ,artificial flowers are frequently to be seen prepared in a particular manner1 which have the property of becoming phosphorescent in darkness1 when they have been exposed to the action of a ray of light1 solar or electric4 ,these curious chemical objects are connected with some very interesting phenomena and remarkable experiments but little known at the present time1 to which we will now draw the reader's attention4 ,the faculty possessed by certain bodies of emitting light when placed in certain conditions1 is much more general than is usually supposed4 ,m4 ,edmond ,becquerel1 to whom we owe a remarkable work on this subject1 divides the phenomena of phosphorescence into five distinct classes3 #a4 ,phosphorescence through elevation of temperature4 ,among the substances which exhibit this phenomenon in a high degree we may mention certain diamonds1 coloured varieties of fluoride of calcium1 some minerals2 and sulphur1 known under the name of artificial phosphorus1 when it has previously been exposed to the action of the light4 #b4 ,phosphorescence through mechanical action4 ,this is to be observed when we rub certain bodies together1 or against a hard substance4 ,if we rub together two quartz crystals in the dark1 we perceive red sparks2 and when pounding chalk or sugar1 there is also an emission of sparks4 #c4 ,phosphorescence through electricity4 ,this is manifested by the light accompanying disengagement of electricity1 and when gases and rarefied vapours transmit electric discharges4 #d4 ,spontaneous ,phosphorescence is observed1 as every one knows1 in connection with several kinds of living creatures1--glow-worms1 noctilucids1 etc41 and similar phosphorescent effects are produced also with organic substances1 animal or vegetable1 before putrefaction sets in4 ,it is manifested also at the flowering time of certain plants1 etc4 #e4 ,phosphorescence through insolation and the action of light4 8,it consists10 says ,m4 ,edmond ,becquerel1 8in exposing for some instants to the action of the sun1 or to that of rays emanating from a powerful luminous source1 certain mineral or organic substances1 which immediately become luminous1 and shine in the dark with a light1 the colour and brilliancy of which depend on their nature and physical character2 the light gradually diminishes in intensity during a period varying from some seconds to several hours4 ,when these substances are exposed anew to the action of light1 the same effect is reproduced4 ,the intensity of the light emitted after insolation is always much less than that of the incidental light40 ,these phenomena appear to have been first observed with precious stones2 then1 in #afjd1 in calcined ,bologna stone1 and later1 in a diamond by ,boyle1 in #affc2 in #afge it was noticed in ,baudoin phosphorus 7residuum of the calcination of nitrate of lime71 and more recently still in connection with other substances which we will mention4 ,the substances most powerfully influenced by the action of light are sulphates of calcium and barium1 sulphate of strontium1 certain kinds of diamonds1 and that variety of fluoride of calcium1 which has received the name of chlorophane4 ,illustration3 ,fig4 #cai4--;,artificial flower coated with phosphorescent powder1 exposed to the light of magnesium wire4 ,phosphorescent sulphate of calcium is prepared by calcining in an earthenware crucible a mixture of flowers of sulphur and carbonate of lime4 ,but the preparation only succeeds with carbonate of lime of a particular character4 ,that obtained from the calcination of oyster shells produces very good results4 ,three parts of this substance is mixed with one part of flowers of sulphur1 and is made red-hot in a crucible covered in from contact with the air4 ,the substance thus obtained gives1 after its insolation1 a yellow light in the dark4 ,the shells of oysters1 however1 are not always pure1 and the result is sometimes not very satisfactory2 it is therefore better to make use of some substance whose composition is more to be relied on4 8,when we desire to prepare a phosphorescent sulphate with lime1 or carbonate of lime10 says ,m4 ,e4 ,becquerel1 8the most suitable proportions are those which in a hundred parts of the substance are composed of eighty to a hundred of flowers of sulphur in the first case1 and forty-eight to a hundred in the second1 that is1 when we employ the quantity of sulphur which will be necessary for burning with carbonate of lime to produce a monosulphate4#bj ,it is necessary to have regard to the elevation of the temperature in the preparation4 ,by using lime procured from arragonite1 and reducing the temperature below five hundred degrees for a sufficient time for the reaction between the sulphur and lime to take place1 the excess of sulphur is eliminated1 and we have a feebly luminous mass1 of a bluish tint2 if this mass is raised to a temperature of eight hundred or nine hundred degrees1 it will exhibit a very bright light40 ,sulphate of calcium possesses different phosphorescent properties according to the nature of the salt which has served to produce the carbonate of lime employed4 ,if we transform marble into nitrate of lime1 by dissolving it in water and nitric acid1 and form a precipitate with carbonate of ammonium1 and use the carbonate of lime thus obtained in the preparation of sulphate of calcium1 we have a product which gives a phosphorescence of a violet-red colour4 ,if the carbonate of lime used is obtained from chloride of calcium precipitated by carbonate of ammonia1 the phosphorescence is yellow4 ,if we submit carbonate of lime1 prepared with lime water and carbonic acid1 to the influence of sulphur1 we obtain a sulphur giving a phosphorescent light of very pure violet4 ,carbonate of lime obtained by forming a precipitate of crystallized chloride of calcium with different alkaline carbonates also gives satisfactory results4 ,luminous sulphates of strontium may be obtained1 like those of calcium1 by the action of sulphur on strontia or the carbonate of this base1 by the reduction of sulphates of strontia with charcoal4 ,blue and green shades are the most common4 ,sulphates of barium also present very remarkable phenomena of phosphorescence2 but to obtain very luminous intensity a higher temperature is needed than with the other substances mentioned1 and we have the same result when we reduce native sulphate of baryta with charcoal2 that is to say1 when the reaction takes place which produces the phosphorus formerly known as phosphorus of ,bologna4 ,preparations obtained from baryta have a phosphorescence varying from orange-red to green4 ,the preparation of such substances as we have just enumerated afford an easy explanation of the method of manufacturing the luminous flowers which we described at the commencement of this chapter4 ,we obtain some artificial flowers1 cover them with some liquid gum1 sprinkle with phosphorescent sulphur1 and let them dry4 ,the pulverulent matter then adheres to them securely1 and it is only necessary to expose the flowers thus prepared to the light of the sun1 or the rays emanating from magnesium wire in a state of combustion 7fig4 #cai71 to produce immediate phosphorescent effects4 ,if taken into a dark room 7fig4 #cbj7 they shine with great brilliancy1 and give off very exquisite coloured rays4 ,phosphorescent sulphates are used also in tracing names or designs on a paper surface1 etc41 and it can easily be conceived that such experiments may be infinitely varied according to the pleasure of the experimenter4 ,illustration3 ,fig4 #cbj4--,phosphorescent flower emitting light in a dark room4 ,but let us ask ourselves if these substances are not capable of being put to more serious uses1 and of being classed among useful products4 ,to this we can reply very decidedly in the affirmative4 ,with phosphorescent matter we can obtain luminous faces for clocks placed in dark1 obscure spots1 and it is not impossible to use it for making sign-boards for shops1 or numbers of houses1 which can be lit up at night4 ,professor ,norton even goes so far as to propose in the 8,journal of the ,franklin ,institute10 not only coating the walls of rooms with these phosphorescent substances1 but also the fronts of houses1 when he considers it would be possible to do away entirely with street lights1 the house-fronts absorbing sufficient light during the day to remain luminous the whole of the night4 ,,chemistry ,,applied ,,to ,,sleight ,,of ,,hand4 ,while physics has provided the species of entertainment called 8sleight of hand0 with a number of interesting effects1 chemistry has only offered it very feeble contributions4 ,robert ,houdin formerly made use of electricity to move the hands of his magic clock1 and the electric magnet in making an iron box so heavy instantaneously that no one could lift it4 ,robin has made use of optics to produce the curious spectacle of the decapitated man1 spectres1 etc4 ,those persons who are fond of this kind of amusement may1 however1 borrow from chemistry some original experiments1 which can be easily undertaken1 and ,i will conclude this chapter by describing a juggling feat which ,i have seen recently executed before a numerous audience by a very clever conjuror4 ,illustration3 ,fig4 #cba4--;,amusing experiment in chemistry4 ,the operator took a glass that was perfectly transparent1 and placed it on a table1 announcing that he should cover the glass with a saucer1 and then1 retiring to some distance1 would fill it with the smoke from a cigarette4 ,and this he carried out exactly1 standing smoking his cigarette in the background1 while the glass1 as though by enchantment1 slowly filled with the fumes of the smoke4 ,this trick is easily accomplished4 ,it is only necessary to pour previously into the glass two or three drops of hydrochloric acid1 and to moisten the bottom of the saucer with a few drops of ammonia4 ,these two liquids are unperceived by the spectators1 but as soon as the saucer is placed over the glass1 they unite in forming white fumes of hydrochlorate of ammonia1 which bear a complete resemblance to the smoke of tobacco4 ,this experiment excited the greatest astonishment among the spectators present on the occasion1 but understanding something of chemistry myself1 ,i easily guessed at the solution of the mystery4 ,the same result is obtained in a course of chemistry in a more simple manner1 and without any attempt at trickery1 by placing the opening of a bottle of ammonia against the opening of another bottle containing hydrochloric acid4 ,,footnotes3 #ai ,it is the same with a number of other common products1 such as clay1 sandstone1 etc41 the composition of which chemistry has revealed4 ,argil1 or clay1 slate1 and schist all contain a metal--aluminium1 which has become most valuable for industrial purposes4 ,stones for building are composed of a metal combined with carbon and oxygen--calcium2 sandstone is composed of silicium1 a metallic body united with oxygen2 and sulphate of magnesia1 which enters into the composition of a purgative drink1 also contains a metal--magnesium4 #bj ,these substances must be finely powdered and thoroughly mixed4 ,,chapter ,,xxvi4 ,,chemistry ,,and ,,alchemy--,,chemical ,,combinations--,,the ,,atmospheric ,,air4 ,we have in the foregoing pages given some experiments1 and considered several of the metals1 but there are numerous very interesting subjects still remaining2 indeed1 the number is so great that we can only pick and choose4 ,all people are desirous to hear something of the atmosphere1 of water1 and the earth2 and as we proceed to speak of crystals and minerals1 and so on to geology1 we shall learn a good deal respecting our globe--its conformation and constituents4 ,but the atmospheric air must be treated of first4 ,this will lead us to speak of oxygen and nitrogen4 ,water will serve to introduce hydrogen with a few experiments1 and thus we shall have covered a good deal of ground on our way towards various other elements in daily use and appreciation4 ,now let us begin with a few words concerning ,,chemistry itself4 ,at the very outset we are obliged to grope in the dark after the origin of this fascinating science4 ,shem1 or 8,chem10 the son of ,noah1 has been credited with its introduction1 and1 at any rate1 magicians were in ,egypt in the time of ,moses1 and the lawgiver is stated by ancient writers to have gained his knowledge from the ,egyptians4 ,but we need not pursue that line of argument4 ,in more modern times the search for the ,philosopher's ,stone and the ,elixir of ,life1 which respectively turned everything to gold1 and bestowed long life upon the fortunate finder1 occupied many people1 who in their researches no doubt discovered the germs of the popular science of ,chemistry in ,alchemy1 while the pursuit took a firm hold of the popular imagination for centuries2 and even now chemistry is the most favoured science1 because of its adaptability to all minds1 for it holds plain and simple truths for our every-day experience to confirm1 while it leads us step by step into the infinite1 pleasing us with experiments as we proceed4 ,alchemy was practised by numerous quacks in ancient times and the ,middle ,ages1 but all its professors were not quacks4 ,astrology and alchemy were associated by the ,arabians4 ,geber was a philosopher who devoted himself entirely to alchemy1 and who lived in the year #gcj ,a4,d4 ,he fancied gold would cure all disease1 and he did actually discover corrosive sublimate1 nitric acid1 and nitrate of silver4 ,to give even a list of the noted alchemists and magicians would fill too much space4 ,raymond ,sully1 ,paracelsus1 ,friar ,bacon1 ,albertus ,magnus1 ,thomas ,aquinas1 ,flamel1 ,bernard of ,treves1 ,doctor ,dee1 with his assistant ,kelly1 and in later times ,jean ,delisle1 and ,joseph ,balsamo 7,cagliostro71 who was one of the most notorious persons in ,europe about one hundred years ago 7#agfe-aghi71 are names taken at random2 and with the older philosophers chemistry was an all-absorbing occupation--not for gold1 but knowledge4 ,the revelation was slow4 ,on the temperature of bodies the old arts of healing were based--for chemistry and medicine were allies4 ,the elements1 we read1 existed on the supposition 8that bodies were hot or cold1 dry or moist02 and on this distinction for a long time 8was based the practice of medicine40 ,the doctrine of the 8three principles0 of existence superseded this1--the principles being salt1 mercury1 and sulphur4 ,metals had been regarded as living bodies1 gases as souls or spirits4 ,the idea remained that the form of the substance gave it its character4 ,acid was pointed2 sweet things were round4 ,chemistry1 then1 has had a great deal to contend against4 ,from the time of the ,egyptians and ,chinese1 who were evidently acquainted with various processes1--dyeing1 etc41--the science filtered through the alchemists to ,beecher and ,stahl1 and then the principle of affinity--a disposition to combine--was promulgated1 supplemented in #afgd by ,mayow1 by the theory of divorce or analysis4 ,he concluded that where union could be effected1 separation was equally possible4 ,in #agah the first 8,table of ,affinities0 was produced4 ,affinity had been shown to be elective1 for ,mayow pointed out that fixed salts chose one acid rather than another4 ,richter and ,dalton made great advances4 ,before them ,hales1 ,black1 ,priestley1 ,scheele1 ,lavoisier1 and numerous others penetrated the mysteries of the science whose history has been pleasantly written by more than one author who we have not been able to consult1 and have no space to do more than indicate4 ,in later days ,faraday1 ,de la ,rive1 ,roscoe1 and many others have rendered chemistry much more popular1 while they have added to its treasures4 ,the story of the progress of chemistry would fill a large volume1 and we have regretfully to put aside the introduction and pass on4 ,before proceeding to investigate the elements1 a few words concerning the general terms used in chemistry will be beneficial to the reader4 ,if we look at the list of the elements1 pp4 #cjh-i1 we shall see various terminations4 ,some are apparently named from places1 some from their characteristics4 ,metals lately discovered by the spectroscope 7and recently7 end in ium2 some end in 8ine10 some in 8on40 ,as far as possible in late years a certain system of nomenclature has been adhered to1 but the old popular names have not been interfered with4 ,when elements combine together in certain proportions of each they receive certain names4 ,the following table will explain the terms used2 for instance1 we find that-- ,compounds of ,oxygen are termed ,oxides1 as oxide of copper4 0 ,hydrogen 0 ,hydrides1 as hydride of potassium4 0 ,chlorine 0 ,chlorides1 as chloride of sodium4 0 ,nitrogen 0 ,nitrides1 as nitride of boron4 0 ,bromine 0 ,bromides1 as bromide of potassium4 0 ,iodine 0 ,iodides1 as iodide of potassium4 0 ,sulphur 0 ,sulphides1 or ,sulphurets1 as sulphuret of lead4 0 ,selenium 0 ,selenides1 as selenide of mercury4 0 ,carbon 0 ,carbides1 or as carbide of nitrogen1 ,carburets1 and so on4 ,the above examples refer to the union in single proportion of each1 and are called ,binary ,compounds4 ,when more than one atom of each element exists in different proportions we have different terms to express such union4 ,if one atom of oxygen be in the compound it is called a 8monoxide0 or 8protoxide02 two atoms of oxygen in combination is termed 8dioxide0 or 8binoxide02 three1 8trioxide10 or 8tritoxide02 four is the 8tetroxide0 or 8per-oxide10 etc4 ,when more than one atom1 but not two atoms is involved1 we speak of the sesqui-oxide 7one-and-a-half71--8oxide0 being interchangeable for 8sulphide0 or 8chloride10 according to the element4 ,there are other distinctions adopted when metals form two series of combinations1 such as ous and ic1 which apply1 as will be seen1 to acids4 ,sulphuric and sulphurous acids1 nitric and nitrous acid are familiar examples4 ,in these cases we shall find that in the acids ending in 8ous0 oxygen is present in less quantity than in the acids ending in ic4 ,the symbolic form will prove this directly1 the number of atoms of oxygen being written below1 ,sulphurous ,acid ,h#b ,,so#c4 ,nitrous ,acid ,,hno#b4 ,sulphuric ,acid ,h#b,,so#d4 ,nitric ,acid ,,hno#c4 ,whenever a stronger compound of oxygen is discovered than that denominated by ic1 chemists adopt the plan of dubbing it the per 7 over71 as per-chloric acid1 which possesses four atoms of oxygen 7,h,cl,o#d71 chloric acid being ,h,cl,o#c4 ,the opposite ,greek term1 7hupo1 below71 is used for an acid with less than two atoms of oxygen1 and in books is written 8hypo0-chlorous 7for instance74 ,care has been taken to distinguish between the higher and lower2 for 8hyper0 is used in ,english to denote excess1 as hyper-critical2 and hypo might to a reader unacquainted with the derivation convey just the opposite meaning to what is intended4 ,while speaking of these terminations we may show how these distinctive endings are carried out4 ,we shall find1 if we pursue the subject1 that when we have a salt of any acid ending in ic the salt terminates in 8ate40 ,similarly the salts of acids ending in ous1 end in 8ite40 ,to continue the same example we have-- ,sulphurous ,acid1 which forms salts called ,sulphites4 ,sulphuric ,acid1 0 0 ,sulphates4 ,besides these are sulphides1 which are results of the unions or compounds of elementary bodies4 ,sulphites are more complicated unions of the compounds4 ,sulphates are the salts formed by the union of sulphuric acid with bases4 ,sulphides or sulphurets are compounds in which sulphur forms the electro-negative element1 and sulphites are salts formed by the union of sulphurous acids with bases1 or by their action upon them4 ,illustration3 ,fig4 #cbb4--;,combinations of elements4 ,the symbolical nomenclature of the chemist is worse than ,greek to the uninitiated4 ,we frequently see in so-called popular chemical books a number of hieroglyphics and combinations of letters with figures very difficult to decipher1 much less to interpret4 ,these symbols take the place of the names of the chemical compounds4 ,thus water is made up of oxygen and hydrogen in certain proportions2 that is1 two of hydrogen to one of oxygen4 ,the symbolic reading is simple1 ,h#b,o1 the oxide of hydrogen4 ,potassium again mingles with oxygen4 ,potassium is ,k in our list2 ,,ko is oxide of potassium 7potash74 ,let us look into this a little closer4 ,the union of one particle of a simple body with a particle of another simple body can be easily understood2 but1 as we have seen1 it is possible to have substances consisting of four or five different particles1 though the greater number of chemical combinations consist of two or three dissimilar ones4 ,in the diagram 7fig4 #cbb7 we have some possible combinations4 ,in these combinations we may have one particle of a in combination with one1 two1 three1 four1 or five of b1 and many particles of a can unite with various molecules of b4 ,suppose we have oxygen and sulphur compounds as follows3-- ,thus there are three different compounds of these two elements--,,so1 ,,so#b1 ,,so#c 7without water74 ,illustration3 7#a7 7#b7 7#c7 ,fig4 #cbc4-7a7 ,hydrosulphurous ,acid4 7#b7 ,sulphurous ,acid4 7#c7 ,sulphuric ,acid4 ,a compound body may combine with another compound body1 and this makes a complicated compound4 ,suppose we have a mixture of sulphuric acid and potash4 ,we have a sulphate of potassium 7,k#b,,so#d7 and combinations of these combinations may likewise be formed4 ,we must read these symbols by the light of the combining weights given in the table1 and then we shall find the weight of oxygen or other elements in combination4 ,thus when we see a certain symbol 7,hg4,s for instance71 we understand that they form a compound including so many parts of mercury and so many of sulphur1 which is known as vermilion4 ,hg4,o is oxide of mercury1 and by reference to the table of ,atomic ,weights1 we find mercury is ,hg41 and its combining weight is #bjj2 while oxygen is ,o1 and its weight is #af4 ,thus we see at once how much of each element is contained in oxide of mercury1 and this proportion never varies2 there must be #bjj of one and #af of the other1 by weight1 to produce the oxide4 ,so if the oxygen has to be separated from it1 the sum of #baf parts must be taken to procure the #af parts of oxygen4 ,when we see1 as above1 ,o#b or ,o#c1 we know that the weight must be calculated twice or three times1 ,o being #af2 ,o#b is therefore #cb parts by weight4 ,so when we have found what the compounds consist of1 we can write them symbolically with ease4 ,,composition ,,of ,,the ,,atmospheric ,,air4 ,we have already communicated a variety of facts concerning the air4 ,we have seen that it possesses pressure and weight4 ,we call the gaseous envelope of the earth the atmosphere1 and we are justified in concluding that other planets possess an atmosphere also1 though of a different nature to ours4 ,we have seen how easy it is to weigh the air1 but we may repeat the experiment4 7,see illustration1 fig4 #de1 page #ej47 ,we shall find that a perfectly empty glass globe will balance the weights in the scale-pan2 admit the air1 and the glass globe will sink4 ,so air possesses weight4 ,we have mentioned the ,magdeburg hemispheres1 the barometer1 the air-pump1 and the height and the pressure of the atmosphere have been indicated4 ,the density of the atmosphere decreases as we ascend2 for the first seven miles the density diminishes one-fourth that of the air at the sea-level1 and so on for every succeeding seven4 ,in consequence of the equal1 if enormous1 pressure exercised in every direction1 we do not perceive the inconvenience1 but if the air were removed from inside of a drum1 the parchment would quickly collapse4 ,we feel the air when we move rapidly4 ,we breathe the air1 and that statement brings us to consider the composition of the atmosphere1 which1 chemically speaking1 may vary a little 7as compared with the whole mass7 in consequence of changes which are continually taking place1 but to all intents and purposes the air is composed as follows1 in #ajj parts3 ,nitrogen #gi parts4 ,oxygen #bj 0 ,carbonic ,acid 4#jd 0 with minute quantities of other ingredients1 such as ammonia1 iodine1 carbonetted hydrogen1 hydrochloric acid1 sulphuretted hydrogen1 nitric acid1 carbonic oxide1 and dust particles1 as visible in the sunbeams1 added4 ,the true composition of the atmosphere was not known till ,lavoisier demonstrated that it consisted of two gases1 one of which was the vital fluid1 or oxygen1 discovered by ,priestley4 ,to the other gas ,lavoisier gave the name of ,azote1--an enemy of life1--because it caused death if inhaled alone4 ,the carbonic acid in the air varies very much1 and in close1 heated1 and crowded rooms increases to a large quantity1 which causes lassitude and headache4 ,we can easily prove the existence of carbonic acid gas as exhaled from the lungs4 ,suppose we take a glass and fill it partly with clear lime-water2 breathe through a glass tube into the water in the glass1 and very quickly you will perceive that the lime-water is becoming cloudy and turbid4 ,this cloudiness is due to the presence of chalk1 which has been produced by the action of the carbonic acid gas in the lime-water4 ,this is a well known and always interesting experiment1 because it leads up to the vital question of our existence1 and the functions of breathing and living4 ,a popular writer once wrote a book entitled1 8,is ,life ,worth ,living80 and a witty commentator replied to the implied question by saying1 8,it depends upon the liver40 ,this was felt to be true by many people who suffer1 but the scientific man will go farther1 and tell you it depends upon the air you breathe1 and on the carbonic acid you can raise to create heat1--animal heat1--which is so essential to our well-being4 ,we are always burning2 a furnace is within us1 never ceasing to burn without visible combustion4 ,we are generating heat by means of the blood4 ,we know that we inhale air into the lungs1 and probably are aware that the air so received parts with the oxygen to renew the blood4 ,the nitrogen dilutes the oxygen1 for if we inhaled a less-mixed air we should either be burnt up or become lunatics1 as light-headed as when inhaling 8laughing-gas40 ,this beautifully graduated mixture is taken into our bodies1 the oxygen renews the blood and gives it its bright red colour2 the carbon which exists in all our bodies is cold and dead when not so vivified by oxygen4 ,the carbonic acid given off produces heat1 and our bodies are warm4 ,but when the action ceases we become cold1 we die away1 and cease to live4 ,man's life exemplifies a taper burning2 the carbon waste is consumed as the wax is1 and when the candle burns away--it dies6 ,it is a beautiful study1 full of suggestiveness to all who care to study the great facts of ,nature1 which works by the same means in all matter4 ,we will refer to plants presently1 after having proved by experiment the existence of nitrogen in the air4 ,rutherford experimented very cruelly upon a bird1 which he placed beneath a glass shade1 and there let it remain in the carbonic acid exhaled from its lungs1 till the oxygen being at length all consumed by the bird1 it died4 ,when the atmosphere had been chemically purified by a solution of caustic potash1 another bird was introduced1 but though it lived for some time1 it did not exist so long as the first4 ,again the air was deprived of the carbonic acid1 and a third bird was introduced4 ,the experiment was thus repeated1 till at length a bird was placed beneath the receiver1 and it perished at once4 ,this is at once a cruel and clumsy method of making an experiment1 which can be more pleasantly and satisfactorily practised by burning some substance in the air beneath the glass4 ,phosphorus1 having a great affinity for oxygen1 is usually chosen4 ,the experiment can be performed as follows with a taper1 but the phosphorus is a better exponent4 ,let us take a shallow basin with some water in it1 a cork or small plate floating upon the water1 and in the plate a piece of phosphorus4 ,we must be careful how we handle phosphorus1 for it has a habit1 well known1 but sometimes forgotten by amateur chemists1 of suddenly taking fire4 ,light this piece of phosphorus1--a small piece will do if the jar be of average 8shade0 size1--and place the glass over it1 as in the illustration 7fig4 #cbe74 ,the smoke will quickly spread in the jar1 and the entry of air being prevented1 because the jar is resting under water1 phosphoric acid will be formed1 and the oxygen thereby consumed4 ,the water1 meanwhile1 will rise in the jar1 the pressure of the air being removed4 ,the burning phosphorus will soon go out1 and when the glass is cool1 you will be able to ascertain what is inside the jar4 ,put a lighted taper underneath1 and it will go out4 ,the taper would not go out before the phosphorus was burnt in the glass1 and so now we perceive we have azote in the receptacle--that is1 nitrogen4 ,the other1 the constituent of our atmosphere1 carbonic acid1 as we have seen1 is very injurious to the life of animals1 and as every animal breathes it out into the air1 what becomes of it8 ,where does all this enormous volume of carbonic acid1 the quantities of this poison which are daily and nightly exhaled1 where do they all go to8 ,we may be sure nature has provided for the safe disposal of it all4 ,not only because we live and move about still1--and of course that is a proof1--but because nature always has a compensating law4 ,remember nothing is wasted2 not even the refuse1 poisonous air we get rid of from our lungs4 ,where does it go8 ,illustration3 #cbd4--,rutherford's experiment4 ,it goes to nourish the plants and trees and vegetables that we delight to look upon and to eat the fruit of4 ,thus the vegetable world forms a link between the animals and the minerals4 ,vegetables obtain food1 so to speak1 and nourishment from water1 ammonia1 and carbonic acid1 all compound bodies1 but inorganic4 ,water consists of oxygen and hydrogen1 carbonic acid of carbon and oxygen1 and ammonia of hydrogen and nitrogen4 ,water and ammonia are present in the air2 so are oxygen and nitrogen4 ,water falls in the form of rain1 dew1 etc4 ,so in the atmosphere around us we find nearly every necessary for plant-life2 and in the ground1 which supplies some metallic oxides for their use1 we find the remainder4 ,from the air1 then1 the plant derives its life4 ,illustration3 ,fig4 #cbe--;,drawing the oxygen from air by combustion4 ,the vegetable kingdom in turn gives all animals their food4 ,this you will see at a glance is true4 ,certainly animals live on animals4 ,man and wilder animals live on the beasts of the field in a measure1 but those beasts derive their nourishment from vegetables--the vegetable kingdom4 ,so we live on the vegetable kingdom1 and it separates the carbonic acid from the air1 and absorbs it4 ,what we do not want it takes4 ,what we want it gives4 ,vegetables give out oxygen1 and we consume it gladly4 ,we throw away carbonic acid1 and the plants take it greedily2 and thus the atmosphere is retained pure for our use4 ,we can1 if desirable1 prove that plants absorb carbonic acid and give out oxygen by placing leaves of a plant in water1 holding the acid in solution1 and let the sun shine upon them4 ,before long we shall find that the carbonic acid has disappeared1 and that oxygen has come into the water4 ,carbonic acid is sufficiently heavy to be poured from one vessel to another2 and if we have obtained some in a glass1 we can extinguish a taper by pouring the invisible gas on to the lighted taper1 when it will be immediately extinguished4 ,from the foregoing observations it will be perceived how very desirable it is that ventilation should be attended to4 ,people close up windows and doors and fireplaces1 and go to bed and sleep4 ,in the morning they complain of headache and lassitude2 they wonder what is the matter1 and why the children are not well4 ,simply because they have been rebreathing the carbonic acid4 ,go into a closed railway carriage which is nearly filled 7and it is astonishing to us how people can be so foolish as to close every outlet71 and you will recoil in disgust4 ,these travellers shut the ventilators and windows 8because of the cold40 ,a very small aperture will ventilate a railway carriage2 but a close carriage is sickening and enervating1 as these kind of travellers find out by the time they reach their journey's end4 ,air was given us to breathe at night as well as by day2 and though from man's acts or omissions there may be circumstances in which 8night0 air may affect the health1 we maintain that air is no more injurious naturally than 8day0 air4 ,colder it may be1 but any air at night is 8night0 air1 in or out of doors at night2 and we are certain that night air in itself never hurt any healthy person4 ,it is not nature's plan to destroy1 but to save4 ,if a person delicate in constitution gets hot1 and comes out into a colder atmosphere1 and defy nature in that way1 he 7or she7 must take the consequences4 ,but air and ventilation 7not draught7 are necessaries of health1 and to say they injure is to accuse nature falsely4 ,there are many impurities in the air in cities1 and in country places sometimes1 but such impurities are owing to man's acts and omissions4 ,with average sanitary arrangements and appliances in a neighbourhood no one need be afraid to breathe fresh air night or day2 and while many invalids have1 we believe1 been retarded in recovery from being kept in a close room1 hundreds will be benefited by plenty of fresh air4 ,we should not so insist upon these plain and simple truths were there not so many individuals who think it beneficial to close up every avenue by which air can enter1 and who then feel ill and out of spirits1 blaming everything but their own short-sightedness for the effect of their own acts4 ,an inch or two of a window may be open at night in a room1 as the chimney register should be always fully up in bedrooms4 ,when there are fires the draught supplies fresh air to the room with sufficient rapidity4 ,but many seaside journeys might be avoided if fresh air were insisted on at home4 ,there is another and an important constituent of the atmosphere called ,,ozone1 which is very superior oxygen1 or oxygen in what is termed the 8,allotropic0 state1 and is distantly related to electricity1 inasmuch as it can be produced by an electrical discharge4 ,this partly accounts for the freshness in the air after a thunderstorm1 for we are all conscious that the storm has 8cleared the air40 ,the fresh1 crisp ozone in the atmosphere is evident4 ,ozone differs from oxygen in possessing taste and smell1 and it is heavier by one-half than the oxygen gas4 ,there is a good deal of ozone in the sea breeze1 and we can1 though not infallibly1 detect its presence by test-paper prepared with iodide of potassium1 which1 when ozone is present1 will turn blue4 ,we have still something to learn about ozone1 which may be considered as 8condensed oxygen40 ,illustration3 ,fig4 #cbf4 ,development of gas by combustion4 ,fig4 #cbg4 ,we have frequently mentioned 8combustion10 and as under ordinary circumstances such effects cannot take place without atmospheric air1 we will consider it4 ,combustion is chemical action accompanied by light and heat4 ,chemical union is always attended by the development of heat1 not always by light1 because the union varies in intensity and quickness4 ,but when a candle is burning we can study all the interesting phenomena of combustion4 ,we have already spoken of ,,heat and ,,light1 so we need only refer the readers to those subjects in the former parts of this volume4 ,heat is referable to chemical action1 and varies according to the energy of union4 ,heat is always present1 remember1 in a greater or less degree2 and when visible combustion takes place we see light4 ,invisible combustion goes on in our bodies1 and we feel heat2 when we get cold we feed the fire by eating1 or blow it by exercise and air in our lungs4 ,illustration3 ,fig4 #cbh4--;,gas evolved from flame4 ,we shall speak1 however1 of combustion now as it affects us in daily life2 our fires1 our candles1 gas1 etc41 and under these ordinary circumstances hydrogen and carbon are present4 7,we shall hear more about carbon presently47 ,these unite with the oxygen to form water and carbonic acid2 the water being visible as we first put the cold shade upon the lighted lamp1 and the carbonic acid renders the air impure4 ,in the case of a common candle1 or lamp1 combustion takes place in the same way4 ,the wick is the intermediary4 ,the oil mounts in the lamp wick1 where it is converted into a gas by heat2 it then 8takes fire10 and gives us light and heat4 ,the candle-flame is just the same with one exception3 the burning material is solid1 not liquid1 though the difference is only apparent1 for the wax is melted and goes up as gas4 ,the burning part of the wick has a centre where there is no combustion1 and contains carbon4 ,we can prove this by placing a bent tube1 as in the illustration 7fig4 #cbf71 one end in the unburning part of the flame4 ,we shall soon see a dark vapour come over into the receiver4 ,this is combustible1 for if we raise the tube without the glass we can light the gas 7fig4 #cbg74 ,if we insert the end of the tube into the brilliant portion of the flame we shall perceive a black vapour1 which will extinguish the combustion1 for it is a mixture of carbonic acid gas and aqueous vapour1 in which 7fig4 #cbh7 particles of carbon are floating4 ,illustration3 ,fig4 #cbi4--;,davy's safety lamp4 ,illustration3 ,fig4 #ccj4--;,davy lamp 7section74 ,when we proceed to light our lamps to read or to write by1 we find some difficulty in making the wick burn at first4 ,we present to it a lighted taper1 and it has no immediate effect4 ,here we have oil and cotton1 two things which would speedily set a warehouse in flames from top to bottom1 but we cannot even ignite them1 try all we can4 ,why8--,because we must first obtain a gas1 oil will not burn liquid2 it must be heated to a gaseous point before it will burn1 as all combustion depends upon that1--so flames mount high in air4 ,now in a candle-flame1 as will be seen in the diagram 7fig4 #cca471 there are three portions1--the inner dark core1 which consists of unburnt gas2 the outer flame1 which gives light2 and the outside rim of perfect combustion non-luminous4 ,in the centre1 ,a1 there is no heat4 ,if we place a piece of gauze wire over the flame at a little distance the flame will not penetrate it4 ,it will remain underneath1 because the wire1 being of metal1 quickly absorbs the heat1 and consequently there is no flame4 ,this idea led to the invention of the 8safety0 lamp by ,sir ,humphrey ,davy1 which1 although it is not infallible1 is the only lamp in general use in mines 7figs4 #cbi1 #ccj74 ,illustration3 ,fig4 #cca4--;,construction of a candle flame4 ,mines must have light1 but there is a gas in mines1 a 8marsh0 gas1 which becomes very explosive when it mixes with oxygen4 ,of course the gas will be harmless till it meets oxygen1 but1 in its efforts to meet1 it explodes the moment the union takes place2 instead of burning slowly like a candle it goes off all at once4 ,this gas1 called 8fire damp10 is carburetted hydrogen1 and when it explodes it develops into carbonic acid gas1 which suffocates the miners4 ,illustration3 ,fig4 #ccb4--,pouring carbonic acid on a lighted taper4 ,,chapter ,,xxvii4 ,,non-,,metallic ,,elements4 ,,oxygen--,,symbol ,o2 ,,atomic ,,weight #af4 ,oxygen is certainly the most abundant element in nature4 ,it exists all around us1 and the animal and vegetable worlds are dependent upon it4 ,it constitutes in combination about one-half of the crust of the earth1 and composes eight-ninths of its weight of water4 ,it is a gas without taste or colour4 ,oxygen was discovered by ,priestley and ,scheele1 in #aggd1 independently of each other4 ,illustration3 ,fig4 #ccc4--,oxygen from oxide of mercury4 ,oxygen can be procured from the oxides of the metals1 particularly from gold1 silver1 and platinum4 ,the noble metals are reducible from their oxides by heat1 and this fact assists us at once4 ,if we heat chlorate of potash1 mixed with binoxide of manganese1 in a retort in a furnace1 the gas will be given off4 ,there are many other ways of obtaining oxygen1 and we illustrate two 7figs4 #ccc1 #cce74 ,the red oxide of mercury will very readily evolve oxygen1 and if we heat a small quantity of the compound in a retort as per illustration 7fig4 #ccc7 we shall get the gas4 ,in a basin of water we place a tube test-glass1 and the gas from the retort will pass over and collect in the test tube1 driving out the water4 ,the other method mentioned above1--viz41 by heating chlorate of potash1 etc41 in a furnace1 is shown in the following illustration4 ,oxygen1 as we have said1 is a colourless and inodorous gas1 and for a long time it could not be obtained in any other form2 but lately both oxygen and hydrogen have been liquified under tremendous pressure at a very low temperature4 ,oxygen causes any red-hot substance plunged into it to burn brightly2 a match will readily inflame if a spark be remaining1 while phosphorus is exceedingly brilliant1 and these appearances1 with many others equally striking1 are caused by the affinity for those substances possessed by the gas4 ,combustion is merely oxidation1 just as the process of rusting is1 only in the latter case the action is so slow that no sensible heat is produced4 ,but when an aggregate of slowly oxidising masses are heaped together1 heat is generated1 and at length bursts into flame4 ,this phenomenon is called 8spontaneous combustion40 ,cases have been known in which the gases developed in the human body by the abuse of alcoholic drinks have ended fatally2 in like manner the body being completely charred4 7,combustion must not be confounded with ignition1 as in the electric light47 ,oxygen then1 we see1 is a great supporter of combustion1 though not a combustible itself as coal is4 ,when the chemical union of oxygen with another substance is very rapid an explosion takes place4 ,illustration3 ,fig4 #ccd4--,showing retort placed in furnace4 ,illustration3 ,fig4 #cce4--,the generation of oxygen from oxide of manganese and potash4 ,oxidation occurs in various ways4 ,besides those already mentioned1 all verdigris produced on copper1 all decays of whatever kind1 disintegration1 and respiration1 are the effects of oxygen4 ,the following experiment for the extraction of oxygen directly from the air was made by ,m4 ,boussingault1 who passed the gas upon a substance at a certain temperature1 and released it at a higher4 ,the illustration on page #cea will show the way in which the experiment was performed4 ,boussingault permitted a thin stream of water to flow into a large empty flask1 and by this water the air was gradually driven out into a flask containing chloride of calcium and sulphuric acid1 which effectually dried it4 ,this dry air then passed into a large tube inside the reverberatory furnace1 in which tube were pieces of caustic baryta4 ,heated to a dull redness this absorbs oxygen1 and when the heat is increased to a bright red the superabundant gas is given off4 ,thus the oxygen was permitted to pass from the furnace-tube into the receiving glass1 and so pure oxygen was obtained from the air which had been in the glass bottle at first 7fig4 #cch74 ,illustration3 ,fig4 #ccf4--,phosphorus burning in oxygen4 ,,hydrogen--,,symbol ,h2 ,,atomic ,,weight #a4 ,hydrogen is abundant in nature1 but never free4 ,united with oxygen it forms water1 hence its name1 8water-former40 ,it is to ,parcelcus that its discovery is due1 for he found that oil of vitriol in contact with iron disengaged a gas which was a constituent of water4 ,this gas was subsequently found to be inflammable1 but it is to ,cavendish that the real explanation of hydrogen is owing4 ,he explained his views in #agff4 ,hydrogen is obtained in the manner illustrated in the cut1 by means of a furnace1 as in fig4 #cci1 or by the bottle method1 as per fig4 #cdj4 ,the first method is less convenient than the second4 ,a gun-barrel or fire-proof tube is passed through the furnace1 and filled with iron nails or filings2 a delivery tube is at the farther end1 and a flask of water boiling at the other4 ,the oxygen combines with the iron in the tube1 and the hydrogen passes over4 ,the second method is easily arranged4 ,a flask1 as in the cut1 is provided1 and in it some zinc shavings are put4 ,diluted sulphuric acid is then poured upon the metal4 ,sulphate of zinc is formed in the flask1 and the hydrogen passes off4 ,hydrogen being the lightest of all known bodies1 its weight is put as #a1 and thus we are relatively with it enabled to write down the weights of all the other elements4 ,hydrogen is fourteen-and-a-half times lighter than atmospheric air1 and would do admirably for the inflation of balloons were it not so expensive to procure in such large quantities as would be necessary4 ,ordinary coal gas1 however1 contains a great deal of hydrogen1 and answers the same purpose4 ,illustration3 ,fig4 #ccg4--,magnesium wire burning in oxygen4 ,a very pretty experiment may be made with a bladder full of hydrogen gas4 ,if a tube be fitted to the bladder already provided with a stop-cock1 and a basin of ordinary soap-suds be at hand1 by dipping the end of the tube in the solution and gently expressing the gas1 bubbles will be formed which are of exceeding lightness 7fig4 #cda74 ,they can also be fired with a taper4 ,another experiment may be made with hydrogen as follows3--,if we permit the gas to escape from the flask1 and light it1 as in the illustration1 and put a glass over it1 we shall obtain a musical note1 higher or lower1 according to the length1 breadth1 and thickness of the open glass-tube 7fig4 #cdb74 ,if a number of different tubes be employed1 we can obtain a musical instrument--a gas harmonium4 ,illustration3 ,fig4 #cch4--;,extraction of oxygen from air4 ,hydrogen burns with a blue flame1 and is very inflammable4 ,even water sprinkled upon a fire will increase its fierceness1 because the hydrogen burns with great heat1 and the oxygen is liberated4 ,being very light1 ,h can be transferred from one vessel to another if both be held upside down4 ,some mixtures of ,h and ,o are very explosive4 ,the oxyhydrogen blow-pipe is used with a mixture of ,o and ,h1 which is forcibly blown through a tube and then ignited4 ,the flame thus produced has a most intense heating-power4 ,a very easy method of producing hydrogen is to put a piece of sodium into an inverted cylinder full of water1 standing in a basin of water4 ,the sodium liberates the hydrogen by removing the oxygen from the liquid4 ,,water--,,symbol ,h#b,o2 ,,atomic ,,weight #ah4 ,at page #ei of this volume we said something about water1 and remarked 7as we have since perceived by experiment7 that 8water is composed of oxygen and hydrogen in proportions1 by weight1 of eight of the former to one of the latter gas2 in volume1 hydrogen is two to one02 and we saw that 8volume and weight were very different things40 ,this we will do well to bear in mind1 and that1 to quote ,professor ,roscoe1 8,water is always made up of sixteen parts of oxygen to two parts of hydrogen by weight02 sixteen and two being eighteen1 the combining weight of water is eighteen4 ,illustration3 ,fig4 #cci4--,preparation of hydrogen with furnace4 ,illustration3 ,fig4 #cdj4--;,apparatus for generating hydrogen by flask4 ,we can prove by the ,eudiometer that hydrogen when burnt with oxygen forms water2 and here we must remark that water is not a mere mechanical mixture of gases1 as air is4 ,water is the product of chemical combination1 and as we have before said1 is really an oxide of hydrogen1 and therefore combustion1 or electricity1 must be called to our assistance before we can form water1 which is the result of an explosion1 the mixture meeting with an ignited body--the aqueous vapour being expanded by heat4 ,the ancients supposed water to be a simple body1 but ,lavoisier and ,cavendish demonstrated its true character4 ,pure water1 at ordinary temperatures1 is devoid of taste and smell1 and is a transparent1 nearly colourless1 liquid4 ,when viewed in masses it is blue1 as visible in a marked degree in the ,rhone and ,rhine1 at ,geneva1 and ,ble respectively4 ,its specific gravity is #a1 and it is taken as the standard for ,sp4 ,gravity1 as hydrogen is taken as the standard for ,atomic ,weight4 ,the uses of water and the very important part it plays in the arrangements of nature as a mechanical agent1 geology can attest1 and meteorology confirm4 ,it composes the greater portions of animals and plants2 without water the world would be a desert--a dead planet4 ,illustration3 ,fig4 #cda4--;,blowing bubbles with hydrogen gas4 ,we sometimes speak of 8pure0 spring water1 but such a fluid absolutely pure can scarcely be obtained2 and though we can filter water there will always remain some foreign substance or substances in solution4 ,it is well known that the action of water wears away and rounds off hard rocks1 and this power of disintegration is supplemented by its strength as a solvent1 which is very great4 ,rain-water is purest in the country as it falls from the clouds4 ,in smoky towns it becomes sooty and dirty4 ,it is owing to the solvent properties of water1 therefore1 that we have such difficulty in obtaining a pure supply4 ,there is hard water and soft water4 ,the former is derived from the calcareous formations1 and contains lime1 like the ,kent water4 ,this can be ascertained by noticing the incrustations of the vessels wherein the water is boiled4 ,but water rising from hard rocks1 such as granite1 can do little to disintegrate them at the moment1 and therefore the water rises purer4 ,springs from a great depth are warm1 and are known as 8thermal springs02 and when they come in contact with carbonic acid and some salts in their passage to the surface1 they are known as 8mineral waters40 ,these waters hold in solution salts of lime and magnesia1 or carbonates of soda with those of lime and magnesia2 salts of iron1 and compounds of iodine and bromine are found in the natural mineral waters also1 as well as sulphurous impregnations1 instances of which will occur to every reader4 ,illustration3 ,fig4 #cdb4--;,experiment with hydrogen4 ,illustration3 ,fig4 #cdc4--,the composition of water4 ,we mentioned the ,eudiometer just now1 and we give an illustration of it4 ,this instrument is used to ascertain the proportions in which the elements of water are composed by synthesis1 or a putting together of the constituents of a body to make it up4 ,this is distinguished from analysis1 which means separating the compound body into its elements1 as we do when we pass the electric current through water4 ,the ,eudiometer consists of a stout glass tube sealed hermetically at one end2 two platinum wires are pushed in through the glass just before the end is sealed4 ,the tube is now filled with mercury1 and inverted in a bowl of the same metal4 ,hydrogen1 and then oxygen1 are admitted through the mercury in the recognised proportions of two to one4 ,by the time the mercury is somewhat more than half displaced1 the tube should be held upon a sheet of india-rubber at the bottom of the vessel to keep the metal in the tube1 for when the necessary explosion takes place the mercury might also be driven out4 ,a spark from the electrophorus or from a ,leyden jar may now be passed through the gases in the tube4 ,the explosion occurs1 and water is formed inside4 ,if the mercury be again admitted it will rise nearly to the very top of the tube1 driving the bubble up4 ,thus we find we have formed water from the two gases4 ,the decomposition of water is easily affected by electricity1 and if a little sulphuric acid be added to the water1 the experiment will be thereby facilitated4 ,two wires from a battery should be inserted through a glass filled with the water1 and into two test tubes also filled4 ,the wires terminate in platinum strips1 and are fastened at the other end to the positive and negative poles of the galvanic battery4 ,the gases will collect in the test tubes1 and will be found in proper proportions when the current passes4 ,illustration3 ,fig4 #cdd4--,the ,eudiometer4 ,illustration3 ,fig4 #cde4--;,decomposition of water4 ,so much for water in its liquid state4 ,the solid condition of water 7ice7 is equally interesting4 ,when we apply heat to water1 we get a vapour called 8steam02 when we cool water to #cb ,fahr41 we get a solid mass which weighs just the same as the liquid we have congealed1 or the steam we have raised from an equal amount of water4 ,but water expands while in the process of solidification1 just as it does when it becomes gaseous1 and as we have remarked before1 our water-pipes bear full testimony to this scientific fact4 ,when ice forms it has a tendency to crystallize1 and some of these ice crystals are1 as we see1 very beautiful4 ,snow is only water in a nearly solid form1 and the crystals are extremely elegant1 appearing more like flowers than congealed water1 in tiny six-pointed ice crystals4 ,many philosophers of late years have written concerning these tiny crystals1 which1 in common with all crystals1 have their own certain form1 from which they never depart4 ,snowflakes are regular six-sided prisms grouped around a centre forming angles of #fj and #abj4 ,there are a number of forms1 as will be seen from the accompanying illustrations1 and at least ninety-six varieties have been observed4 ,one snowflake1 apparently so like all other flakes that fall1 can thus be viewed with much interest1 and yet1 while so very various1 snowflakes never get away from their proper hexagonal structure4 ,it has been remarked that snowflakes falling at the same time have generally the same form4 ,of the latent heat of ice1 etc41 we have already spoken in our article upon ,heat1 and therefore it will be sufficient to state that the latent heat of water is #gi thermal units1 because when passing from the liquid to the solid state a certain amount of water absorbs sufficient heat to raise an equal quantity of the liquid #gi4 ,this can be proved by taking a measured quantity 7say a pint7 of water at #gi and adding ice of the same weight to the water4 ,the mixture will be found to be at zero4 ,therefore the ice has absorbed or rendered latent #gi of heat which the water possessed4 ,if we melt ice until only a trace of it is left1 we shall still find the water as cold as the ice was2 all the latent heat is employed in melting the ice4 ,so it will take as much heat to bring a pound of ice at zero to a pound of water at zero1 as it would to raise #gi pounds of water #a4 ,the same law applies to steam4 ,illustration3 ,fig4 #cdf4--,snow crystals4 ,water can be distilled in small quantities by an apparatus1 as figured in the illustration1 and by these means we get rid of all impurities which are inseparable from the liquid otherwise4 ,when it is desirable to distil large quantities of water a larger apparatus is used1 called an 8,alembic40 ,the principle is simply to convert the liquid by heat into vapour1 then cool it1 by condensation1 in another vessel4 ,illustration3 ,fig4 #cdg4--;,distilling water4 ,the evaporation of water1 with its effects upon our globe1 belong more to the study of ,meteorology4 ,illustration3 ,fig4 #cdh4--;,distillation4 ,rain-water is the purest1 as we have said1 because it goes through the process of distillation by nature4 ,the sun takes it up1 by evaporation1 into the air1 where it is condensed1 and falls as rain-water4 ,water containing carbonate of lime will petrify or harden1 as in stalactite caverns4 ,the carbonic acid escapes from the dripping water1 the carbonate in solution is deposited as a stalactite1 and finally forms pillars in the cave4 ,sea-water contains many salts2 its composition is as follows1 according to ,dr4 ,schwertzer1 of ,brighton3-- ,water #ifdgdcgb grains4 ,chloride of sodium 7salt7 #bhjeidh 0 ,chloride of potassium #jgfeeb 0 ,chloride of magnesium #cfffeh 0 ,bromide of magnesium #jjbibi 0 ,sulphate of magnesia #bbiegh 0 ,sulphate of lime #jdjffb 0 ,carbonate of lime #jjccja 0 7,with traces of iodine and ammonia74 ------------ #ajjjjjjjj grains4 ,illustration3 ,fig4 #cdi4--,stalactite ,cavern4 ,there is much more oxygen in water than in air1 as can be ascertained by analysis of these compounds4 ,this great proportion in favour of water enables fish to breathe by passing the water through the gills4 ,marine animals 7not fishes71 like the whale1--which is a warm-blooded creature1 and therefore not suited to exist without air1--are obliged to come to the surface to breathe4 ,the density of salt water is much greater than that of fresh water1 and therefore swimming and flotation is easier in the sea than in a river4 ,we shall have more to say of water by-and-by4 ,,nitrogen--,,symbol ,n2 ,,atomic ,,weight #ad4 ,we have already made some reference to this gas when speaking of the atmosphere and its constituents1 of which nitrogen is the principal4 ,from its life-destroying properties it is called 8azote0 by ,french chemists1 and when we wish to obtain a supply of nitrogen all we have to do is to take away the oxygen from the air by burning phosphorus on water under a glass4 ,nitrogen is not found frequently in solid portions of the globe4 ,it is abundant in animals4 ,it is without colour or smell1 and can be breathed in air without danger4 ,it is heavy and sluggish2 but if we put a taper into a jar of nitrogen it will go out1 and animals die in the gas for want of oxygen1 as nitrogen alone cannot support life4 ,illustration3 ,fig4 #cej4--,obtaining nitrogen4 ,the affinity of nitrogen for other substances is not great1 but it gives rise to five compounds1 which are as below1 in the order they are combined with oxygen3-- ,nitrous oxide 78laughing gas07 7,monoxide7 ,n#b,o4 ,nitric oxide ,dioxide ,n#b,o#b4 ,nitrous acid ,trioxide ,n#b,o#c4 ,nitric peroxide ,tetroxide ,n#b,o#d4 ,nitric acid ,pentoxide ,n#b,o#e4 ,these compounds are usually taken as representative examples of combining weight1 and as explanatory of the symbolic nomenclature of chemistry1 as they advance in such regular proportions of oxygen with nitrogen4 ,the combining weight of nitrogen is #ad1 and when two parts combine with five of oxygen it makes nitric acid1 and we put it down as ,n#b,o#e2 on adding water1 ,,hno#c1 as we can see by eliminating the constituents and putting in the proportions4 ,actually it is ,h#b,n#b,o#f1 or1 by division1 ,,hno#c4 ,nitrogen plays a very important part in nature1 particularly in the vegetable kingdom4 ,nitric acid has been known for centuries4 ,geber1 the alchemist1 was acquainted with a substance called 8nitric10 which he found would yield a dissolvent under certain circumstances4 ,he called it 8dissolving fluid40 ,at the end of the twelfth century ,albert ,magnus investigated the properties of this acid1 and in #abce ,raymond ,lully prepared nitre with clay1 and gave the liquid the name of 8aqua-fortis40 ,but till #ahdi nitric acid was only known as a hydrate1--that is1 in combination with water1--but now we have the anhydrous acid4 ,illustration3 ,fig4 #cea4--;,apparatus for obtaining nitrogen by using metal to absorb the oxygen of the air4 ,oxygen and nitrogen combine under the influence of electricity1 as shown by ,cavendish1 who passed a current through an atmospheric mixture of oxygen and nitrogen1 in a tube terminating in a solution of potash1 lime1 and soda4 ,every time the spark passed1 the volume of gas diminished1 and nitric acid was formed1 as it is in thunderstorms1 when it does not remain free1 but unites with ammonia1 and forms a highly useful salt1 which promotes vegetable growth4 ,here is another instance of the usefulness of thunderstorms1 and of the grand provisions of nature for our benefit4 ,nitric acid is obtained by distilling nitre with sulphuric acid4 ,the liquid is1 when pure1 colourless1 and is a powerful oxidizer4 ,it dissolves most metals1 and destroys vegetable and animal substances4 ,by an addition of a little sulphuric acid the water is taken from the nitric acid1 and a very powerful form of it is the result4 ,the acid is of great use in medicine1 and as an application to bites of rabid animals or serpents4 ,it converts cotton waste into 8gun-cotton0 by a very simple process of steeping1 washing1 and pressing4 ,from the hydraulic press it comes in discs like 8quoits10 which will burn harmlessly and smoulder away1 but if detonated they explode with great violence4 ,as a rule1 when damp1 it is not dangerous1 but it can be fired even when wet4 ,it will explode at a less temperature than gunpowder1 and1 moreover1 yields no smoke1 nor does it foul a gun4 ,gun-cotton1 when dissolved in ether1 gives us collodion for photographic purposes4 ,illustration3 ,fig4 #ceb4--,nitric acid obtained from nitre and sulphuric acid4 ,in speaking farther of the compounds of nitrogen with oxygen1 we will limit ourselves to the monoxide1 or laughing gas4 ,this is now used as an ansthetic in dentistry1 etc41 and is quite successful1 as a rule4 ,people afflicted with heart disease should not use it without advice1 however4 ,when inhaled into the lungs it makes the subject very hilarious1 and the effect is rather noisy4 ,it is obtained from the nitrate of ammonia1 which1 on the application of heat1 decomposes into nitrous oxide and vapour4 ,warm water should be used for the trough4 ,the gas is a powerful supporter of combustion4 ,illustration3 ,fig4 #cec4--;,cavendish's experiment4 ,binoxide of nitrogen is of importance in the manufacture of sulphuric acid4 ,nitrogen combines with hydrogen1 forming various compounds4 ,these are the 8amines10 also ammonia1 and ammonium4 ,ammonia possesses the properties of a base4 ,its name is derived from ,jupiter ,ammon1 near whose temple it was prepared1 from camels' dung4 ,but bodies containing nitrogen give off ammonia in course of distilling1 and hartshorn is the term applied to horn-cuttings1 which yield ammonia1 which is a colourless gas of strong odour and taste now obtained from gas-works4 ,illustration3 ,fig4 #ced4--;,experiment to obtain nitric acid4 ,illustration3 ,fig4 #cee4--;,apparatus for obtaining laughing-gas4 ,illustration3 ,fig4 #cef4--;,inhaling laughing gas4 ,illustration3 ,fig4 #ceg4--;,generation of ammonia4 ,to obtain ammonia heat equal parts of chloride of ammonia 7sal ammoniac7 and quick-lime powdered 7see fig4 #ceg74 ,the gas must be collected over mercury1 because it is very soluble in water4 ,ammonia is useful to restore tipsy people and fainting ladies4 ,a solution of ammonia is used for cauteries4 ,ammoniacal gas is remarkable for its solubility in water4 ,to prepare the solution the gas is forced through a series of flasks4 ,the tubes carrying the gas should be continued to the bottoms of the flasks1 else the solution1 being lighter than water1 the upper portion alone would be saturated4 ,the tubes carrying away the solution are raised a little1 so that the renewal is continually proceeding4 ,the gas liquifies under a pressure of six atmospheres1 at a temperature of #aj ,cent4 ,this experiment can be artificially performed by heating chloride of silver saturated with ammonia1 and the silver will part with the gas at a temperature of #dj ,c4 ,the gas will then condense in a liquid form in the tube4 ,the experiment may be facilitated by placing the other extremity of the tube in snow and salt1 and by the liquid we can obtain intense cold4 ,this experiment has been made use of by ,m4 ,carr in his refrigerator 7which was described in the ,physics' section71 by which he freezes water4 ,we may1 however1 just refer to the process4 ,whenever the condition of a body is changed from that of liquid to a gas1 the temperature is greatly lowered1 because the heat becomes 8latent40 ,the latest freezing machine consists of an apparatus as shown in the illustrations herewith 7figs4 #cei and #cfj74 ,the machine is of wrought iron1 and contains1 when ready for action1 a saturated solution of ammonia at zero4 ,this is in communication with another and an air-tight vessel1 of which the centre is hollow4 ,the first process is to heat the solution1 and the gas escapes into the second 8vase10 which is surrounded by cold water1 and quite unable to escape4 ,a tremendous pressure is soon obtained1 and this1 added to the cold water1 before long liquifies the ammonia1 and when the temperature indicates #acj the hot vessel is suddenly cooled by being put into the water4 ,the gas is thus suddenly converted into a liquid1 the water in the second hollow vase is taken out1 and the bottle to be frozen is put into the cavity4 ,the cold is so great1 in consequence of the transformation of the liquid ammonia into a gas1 that it freezes the water in any vessel put into the receiver4 ,the ammonia can be reconverted into liquid and back again1 so no loss is occasioned by the process1 which is rapid and simple4 ,this is how great blocks of ice are produced in water-bottles4 ,illustration3 ,fig4 #ceh4--,liquefaction of ammonia4 ,illustration3 ,fig4 #cei4--;,carr's refrigerator 7first action74 ,the one important point upon which care is necessary is the raising of the temperature4 ,if it be elevated beyond #acj ,c41 the pressure will be too great1 and an explosion will occur4 ,the abundant formation of ammonia from decaying animal matter is evident to everyone1 and depends upon the presence of moisture to a great extent4 ,chloride of ammonia is called sal-ammoniac1 and the carbonate of ammonia crystallizes from the alkaline liquid produced by the distillation of certain animal matter4 ,the compounds of ammonia are easily recognized by a certain sharp taste4 ,they are highly valuable remedial agents1 acting particularly upon the cutaneous system1 and when taken internally1 produce the effect of powerful sudorifics4 ,their volatility1 and the facility with which they are expelled from other substances1 render them of great importance in chemistry1 and peculiarly fit them for the purposes of many chemical analyses4 ,the ammonia compounds display a remarkable analogy to the corresponding combinations of potash and soda4 ,the compounds of ammonia are highly important in their relation to the vegetable kingdom4 ,it may be assumed that all the nitrogen of plants is derived from the ammonia which they absorb from the soil1 and from the surrounding atmosphere4 ,illustration3 ,fig4 #cfj4--;,carr's refrigerator 7second action74 ,the similarity of ammonia to the metallic oxides has led to the conjecture that all its combinations contain a compound metallic body1 which has received the name ammonium 7,,nh#d72 but no one has yet succeeded in its preparation1 although by peculiar processes it may be obtained in the form of an amalgam4 ,ammonias1 in which one or more atoms of hydrogen are replaced by basic radicals1 are termed ,amides1 or ,amines4 ,,chapter ,,xxviii4 ,,non-,,metallic ,,elements 7continued74 ,,chlorine--,,bromine--,,iodine--,,fluor ine--,,carbon--,,sulphur--,,phosphorus-- ,,silicon-- ,,boron--,,tellurium--,,arsenic4 ,chlorine 7,cl47 is usually found with sodium in the mineral kingdom1 and this chloride of sodium is our common salt4 ,chlorine can be obtained by heating hydrochloric acid with binoxide of manganese4 7,atomic weight #cee47 ,illustration3 ,fig4 #cfa4--;,generation of chlorine4 ,chlorine possesses a greenish-yellow colour1 hence its name 8,chloros10 green4 ,it should be handled carefully1 for it is highly injurious and suffocating4 ,it possesses a great affinity for other substances1 and attacks the metals4 ,for hydrogen it has a great affection1 and when hydrogen is combined with any other substances chlorine immediately attacks them1 and in time destroys them4 ,but even this destructive and apparently objectionable quality makes chlorine very valuable2 for if we carry the idea to its conclusion1 we shall find that it also destroys offensive and putrid matter1 and purifies the atmosphere very much4 ,most colouring matters include hydrogen1 and therefore they are destroyed by chlorine1 which is a great 8bleacher0 as well as a purifier4 ,if we dip any vegetable dyes into a jar of chlorine1 they will become white if the dyed substances are damp4 ,hydrochloric acid is known as muriatic acid and spirits of salt4 ,it is obtained when salt is treated with sulphuric acid and the gas comes off into water4 ,equal parts of the acid and the salt are put into a flask as in the cut 7fig4 #cfb71 and diluted with water4 ,the mixture is then heated4 ,the gas is condensed in the bottles half-full of water4 ,the result gives sulphate of soda and hydrochloric acid4 ,this acid is procured in soda manufactories1 and with nitric acid is called 8aqua regia10 a solvent for gold4 ,when chlorine and hydrogen are mixed in equal proportions they explode in sunlight4 ,in the dark or by candle-light they are harmless4 ,dry chlorine gas can be obtained by interposing a glass filled with some chloride of calcium4 ,the gas being heavier than air 7about #b times71 displaces it in the flask1 and when it is filled another can be placed in position4 ,this mode causes a little waste of gas1 which should not be breathed4 ,illustration3 ,fig4 #cfb4--,production of hydrochloric acid4 ,chlorine possesses a great affinity for certain bodies4 ,if the gas be thrown upon phosphorus1 the latter will burn brilliantly4 ,arsenic1 tin1 and antimony when powdered and poured from a shoot into a vase of chlorine will burst into brilliant sparks1 and other metals will glow when introduced to this gas4 ,chlorine forms many unstable combinations with oxygen4 ,its combination with hydrogen has already been referred to4 ,,bromine is a rare element4 7,symbol ,br4 ,atomic weight #hj47 ,it is deep brownish red1 very volatile1 and of a peculiar odour4 ,bromine unites with the elementary bodies1 and forms some oxygen compounds4 ,it resembles chlorine in its properties1 and is used in medicine and in photography4 ,it is found in saline springs and in salt water1 combined with soda and magnesium4 ,the presence of bromine may easily be detected in the strong smell of seaweed4 ,its combinations with metals are termed bromides4 ,it is a powerful poison4 ,,iodine is another relative of chlorine4 ,it is found in seaweed1 which by burning is reduced to kelp4 ,when iodine is heated a beautiful violet vapour comes off1 and this characteristic has given it its name 78iodes10 violet74 ,iodine was discovered by ,courtois1 of ,paris1 and in #ahac1 ,gay ,lussac made it a special study4 ,it is solid at ordinary temperatures1 and assumes crystallized forms in plates of metallic lustre4 ,it is an excellent remedy in 8goitre0 and such affections4 7,symbol ,i4 ,atomic weight #abg47 ,,fluorine is very difficult to prepare4 ,fluor spar is a compound of fluorine and calcium4 ,this element is gaseous1 and combines so rapidly that it is very difficult to obtain in a free state4 ,etching on glass is accomplished by means of hydrofluoric acid1 for fluorine has a great affinity for silicic acid1 which is contained in glass4 ,the glass is covered with wax1 and the design is traced with a needle4 ,the acid attacks the glass and leaves the wax1 so the design is eaten in4 7,symbol ,f4 ,atomic weight #ai47 ,illustration3 ,fig4 #cfc4--;,apparatus for obtaining dry chlorine gas4 ,chlorine1 fluorine1 bromine1 and iodine are termed 8,halogens0 7producers of salts74 ,they appear1 as we have seen1 in a gaseous1 liquid1 and solid form respectively4 ,,carbon is the most1 or one of the most1 largely diffused elements in nature1 and claims more than a passing notice at our hands1 though even that must be brief4 ,we may put down carbon next to oxygen as the most important element in the world4 ,the forms assumed by carbon are very variable1 and pervade nature in all its phases4 ,we have carbon in crystals1 in the animal and vegetable kingdoms1 and amongst the chief minerals a solid1 odourless1 tasteless1 infusible1 and almost insoluble body4 ,in various combinations carbon meets us at every turn2 united with oxygen it forms carbonic acid1 which we exhale for the plants to imbibe4 ,we have it in coal1 with hydrogen and oxygen4 ,we have it building up animal tissues1 and it is never absent in two out of the three great divisions of nature--the plants and the animals 7,symbol ,c2 ,atomic ,w4 #ab74 ,illustration3 ,fig4 #cfd4--;,facets of a brilliant4 ,illustration3 ,fig4 #cfe4--;,facets of a rose diamond4 ,we have carbon in three different and well-known conditions2 as the diamond1 as graphite1 or black-lead1 and as charcoal4 ,the properties of the diamond are well known1 and we shall1 when we get to ,crystallography1 learn the forms of diamond or crystals of carbon4 ,at present we give an illustration or two1 reserving all explanation for the present4 ,diamond cutting is a matter of some difficulty1 and it requires skill to cut in the proper direction4 ,diamonds are found in ,india1 ,brazil1 and at the ,cape of ,good ,hope1 in alluvial soil4 ,the identity of diamond and charcoal was discovered accidentally4 ,an experiment to fuse a few small diamonds resulted in their disappearance1 and when the residue was examined it was found that the diamonds had been burned1 that they had combined with oxygen and formed carbonic acid1 just as when coal burns4 ,the diamond is the hardest of all substances1 the most valuable of gems1 and the purest condition in which carbon appears4 ,,graphite 7,plumbago7 is termed 8black-lead10 and is the next purest form of carbon4 ,it crystallizes and belongs to the primitive formations4 ,in ,cumberland it is dug up and used to make pencils2 the operations can be seen at ,keswick4 ,it has other uses of a domestic character4 ,charcoal is the third form of carbon1 and as it possesses no definite form1 is said to be amorphous4 ,charcoal is prepared in air-tight ovens1 so that no oxygen can enter and burn the wood thus treated4 ,coke is the result of the same process applied to coal4 ,the gas manufactories are the chief depts for this article1 and it is used in locomotive engines4 ,the various smokeless coals and prepared fuels1 however1 are frequently substituted4 ,illustration3 ,fig4 #cff4 --,coke ovens4 ,coke ovens were formerly much resorted to by the railway companies1 who found the ordinary coal too smoky for locomotive purposes1 and apt to give rise to complaints by passengers and residents near the line4 ,the origin of wood charcoal we have seen4 ,all vegetable substances contain carbon4 ,when we burn wood1 in the absence of air as far as possible1 oxygen and hydrogen are expelled4 ,the wood is piled in layers as in the illustration 7fig4 #cfh71 covered over with turf and mould1 with occasional apertures for air4 ,this mass is ignited1 the oxygen and hydrogen are driven off1 and carbon remains4 7,animal charcoal is obtained from calcining bones74 ,wood charcoal attracts vapours1 and water1 if impure1 can be purified by charcoal1 and any impure or tainted animal matter can be rendered inoffensive by reason of charcoal absorbing the gases1 while the process of decay goes on just the same4 ,housekeepers should therefore not always decide that meat is good because it is not offensive to the olfactory nerves4 ,charcoal will remove the aroma1 but the meat may be nevertheless bad4 ,the use of charcoal in filters is acknowledged universally1 and as a constituent of gunpowder it is important4 ,illustration3 ,fig4 #cfg4--;,charcoal burning4 ,carbon is not easily affected by the atmospheric air1 or in the earth2 so in many instances wood is charred before being driven into the ground2 and casks for water are prepared so4 ,soot is carbon in a pulverised condition1 and ,indian ink is manufactured with its assistance4 ,illustration3 ,fig4 #cfh4--,wood piles of charcoal burners4 ,the preparation of wood charcoal gives occupation to men who are frequently wild and untutored1 but the results of their labour are very beneficial4 ,care should be taken not to sleep in a room with a charcoal stove burning1 unless there is ample vent for the carbonic acid gas1 for it will cause suffocation4 ,lampblack is obtained by holding a plate over the flame of some resinous substance1 which deposits the black upon it4 ,there is a special apparatus for this purpose4 ,illustration3 ,fig4 #cfi4--,seltzer-water manufactory4 ,carbon combines with oxygen to make carbonic acid gas1 as we have already mentioned1 and in other proportions to form a more deadly compound than the other4 ,the former is the dioxide 7,,co#b71 the latter the monoxide1 or carbonic oxide 7,,co74 ,the dioxide is the more important1 being held in the atmosphere1 and combined with lime in chalk4 ,all sparkling beverages contain carbonic acid1 to which their effervescence is due4 ,the soda and other mineral waters owe their sparkle to this gas4 ,soda-water consists of a weak solution of carbonate of soda and the acid4 ,there is a vessel holding chalk and water1 and another containing some sulphuric acid4 ,when the sulphuric acid is permitted to unite with the chalk and water1 carbonic acid is liberated4 ,a boy turning a wheel forces the gas into the water in the bottles1 or the water and carbonate of soda is drawn off thus impregnated into bottles and corked down1 in the manner so familiar to all4 ,the bottles are made of the shape depicted1 so that the bubble of air shall be at the top when the bottle lies down4 ,if it be not kept so1 the air will eventually escape1 no matter how tightly the cork be put in4 ,the ordinary 8soda-water0 contains scarcely any soda4 ,it is merely water1 chalk1 and carbonic acid4 ,the 8,gazogene0 is made useful for small quantities of soda-water1 and is arranged in the following manner4 ,the appearance of it is familiar to all4 ,it consists of a double vessel1 into the upper part of which a solution of any kind--wine and water1 or even plain water--is put1 to be saturated with carbonic acid1 or 8aerated10 and into the lower one some carbonate of soda and tartaric acid4 ,a tube leads from this lower to the top of the upper vessel1 which screws on and off4 ,by shaking the apparatus when thus charged and screwed together1 some of the liquid descends through the tube into the lower vessel and moistens the soda and acid1 which therefore act on each other1 and cause carbonic acid to be disengaged2 this1 rising up through the tube 7which is perforated with small holes at the upper part71 disperses itself through the liquid in small bubbles1 and causes sufficient pressure to enable the liquid to absorb it1 which therefore effervesces when drawn off by the tap4 ,illustration3 ,fig4 #cgj4--;,gazogene4 ,illustration3 ,fig4 #cga4--,soda-water apparatus4 ,carbonic acid can be liquified1 and then it is colourless4 ,in a solid form it resembles snow1 and if pressed with the fingers it will blister them4 ,being very heavy the gas can be poured into a vase1 and if there be a light in the receptacle the flame will be immediately extinguished4 ,that even the gas introduced into seltzer-water is capable of destroying life1 the following experiment will prove4 ,let us place a bird within a glass case as in the illustration 7fig4 #cgc71 and connect the glass with a bottle of seltzer-water or a siphon4 ,as soon as the liquid enters1 the carbonic acid will ascend1 and this1 if continued for a long time1 would suffocate the bird1 which soon begins to develop an appearance of restlessness4 ,illustration3 ,fig4 #cgb4--,pouring out the carbonic acid gas4 ,illustration3 ,fig4 #cgc4--;,experiment with carbonic acid4 ,we have already remarked upon the important part taken by this gas in nature1 so we need only mention its existence in pits and caves4 ,there are many places in which the vapour is so strong as to render the localities uninhabitable4 ,in the ,middle ,ages the vapours were attributed to the presence of evil spirits1 who were supposed to extinguish miners' lamps1 and suffocate people who ventured into the caves4 ,in the ,grotto ,del ,cane there is still an example1 and certain caves of ,montrouge are often filled with the gas4 ,a lighted taper held in the hand will1 by its extinction1 give the necessary warning4 ,oxygen and carbon are condensed in carbonic acid1 for the gas contains a volume of oxygen equal to its own4 ,if we fill a glass globe1 as per illustration 7fig4 #cgd71 with pure oxygen1 and in the globe insert two carbon points1 through which we pass a current of electricity1 we shall find1 after the experiment1 that if the stop-cock be opened1 there is no escape of gas1 and yet the mercury does not rise in the tube1 so the oxygen absorbed has been replaced by an equal volume of carbonic acid4 ,the other combination of carbon with oxygen is the carbonic oxide 7,,co71 and when a small quantity of oxygen is burnt with it it gives a blue flame1 as on the top of the fire in our ordinary grates4 ,this gas is present in lime kilns1 and is a very deadly one4 ,we must now pass rapidly through the compounds of carbon with hydrogen1 merely referring to coal for a moment as we go on4 ,coal1 of which we shall learn more in ,mineralogy and ,geology1 is a combination1 mechanical or otherwise1 and is the result of the decomposition of vegetable matter in remote ages1--the so-called 8forests10 which were more like the jungles than the woods of the present day4 ,moss and fern played prominent parts in this great transformation1 as we can see in the ,irish peat-bogs1 where the first steps to the coal measures are taken4 ,illustration3 ,fig4 #cgd4--;,experiment showing that carbonic acid contains oxygen and carbon4 ,the compounds of carbon with hydrogen are important4 ,there is the 8light0 carburetted hydrogen 7,,ch#d71 which is usually known as fire-damp in coal mines4 ,it is highly inflammable and dangerous4 ,the safety-lamp invented by ,davy is a great protection against it1 for as the gas enters it is cooled by the wire1 and burns within harmlessly4 ,the explosion warns the miner4 8,heavy0 carburetted hydrogen possesses double the quantity of carbon 7,c#b;,h#d74 ,it is also explosive when mixed with oxygen4 ,illustration3 ,fig4 #cge4--,temperature reduced by contact with wire4 ,the most useful compound is coal-gas1 and though its principal function appears to be in some manner superseded by electricity1 8gas0 is still too important to be put aside4 ,it can easily be obtained by putting small fragments of coal in the bowl of a tobacco-pipe1 closing the bowl with clay1 and putting it in the fire4 ,before long the gas will issue from the stem of the pipe1 and may either be lighted or collected in a bladder4 ,for the use of the 8million10 however1 gas is prepared upon a very large scale1 and is divided into three processes--its 8formation10 8purification10 and its 8collection0 for distribution to consumers4 ,the first process is carried on by means of retorts shown in the illustration 7fig4 #cgf74 ,the first portion of the next figure is a section of a furnace1 the other part shows two furnaces from the front4 ,the following is the mode employed4 ,the coal is put into retorts fitted to the furnace1 so that they are surrounded by the flames1 and terminating in a horizontal tube called the hydraulic main1 ,e1 which is in its turn connected with a pit or opening for the reception of the tar and ammoniacal liquor1 etc41 which condenses from the gas4 ,it then passes up and down a series of tubes in water1 called a 8condenser10 and in this are reservoirs or receptacles for any tar and ammonia that remain4 ,but sulphur is still present1 so the gas is carried to the purifying apparatus 7,d in fig4 #cgh71 which consists of a large cylindrical vessel air-tight1 with an inverted funnel1 nearly filled with a mixture of lime and water4 ,the gas bubbles in1 and the sulphur unites with the lime1 while the gas rises to the top 7trays of lime are used when the gas enters from the bottom74 ,the ,gasometer1 a large vessel closed at the top and open below1 dips into a large trough of circular shape4 ,the gasometer is balanced by weights and chains1 and may be raised 7,see fig4 #cgi74 ,when quite empty the top rests upon the ground1 and when the gas enters it is raised to the top of the frame which supports it4 ,we have now our ,gasometer full4 ,when the time comes to fill the pipes for lighting purposes1 some of the weights are removed1 the ,gasometer falls down slowly1 and forces the gas through the tubes into the main supply to be distributed4 ,about four cubic feet of gas is obtained from every pound of coal4 ,when gas and air become mixed1 the mixture is very explosive4 ,in a house where an escape of gas is detected let the windows be opened at the top1 and no light introduced for several minutes4 ,illustration3 ,fig4 #cgf4--,retorts4 ,illustration3 ,fig4 #cgg4--,section4 ,front view4 ,illustration3 ,fig4 #cgh4--;,condenser4 ,purifier4 ,gasometer4 ,illustration3 ,fig4 #cgi4--;,gasometer4 ,it has been calculated that one ton of good coal produces the following3-- #a ,chaldron of coke weighing #a1did lbs4 #ab ,gallons of tar 0 #ace lbs4 #ab ,gallons of ammoniacal liquor 0 #ajj lbs4 #e1ijj ,cubic feet of gas 0 #bia lbs4 ,loss 7water7 0 #bbj lbs4 ---------- ,total #b1bdj lbs4 ,illustration3 ,fig4 #chj4--;,gasometer ,we can thus estimate the profits of our gas companies at leisure4 ,the analysis of gas made by ,professor ,bunsen is as under1 in #ajj parts4 ,hydrogen #deeh ,marsh gas #cdij ,carbonic oxide #ffd ,olefiant gas #djh ,butyline #bch ,sulphide of hydrogen #jbi ,nitrogen #bdf ,carbonic acid #cfg ------ #ajjjj ,gas1 therefore1 is very injurious1 for it rapidly vitiates the atmosphere it burns in1 and is very trying to the eyes1 as well as destructive to gilt ornaments4 ,tar is familiar to all readers1 and though unpleasant to handle or to smell1 it produces the beautiful aniline dyes4 ,tar pills are very efficacious for some blood disorders1 and will remove pimples1 etc41 from the face1 and cure 8boils0 effectually4 ,if a dose of five be taken first1 in a day or two four1 and so on1 no second remedy need be applied4 ,we have known cases finally cured1 and no recurrence of boils ever ensued after this simple remedy4 ,illustration3 ,fig4 #cha4--,tar manufactory ,tar is one of the results left in the distillation both of wood and coal3 in places where wood is plentiful and tar in request1 it is produced by burning the wood for that purpose2 and in some of the pits in which charcoal is produced1 an arrangement is made to collect the tar also4 ,coal-tar and wood-tar are different in some respects1 and are both distilled to procure the napthas which bear their respective names4 ,from wood-tar creosote is also extracted1 and it is this substance which gives the peculiar tarry flavours to provisions1 such as ham1 bacon1 or herrings1 cured or preserved by being smoked over wood fires4 ,tar is used as a sort of paint for covering wood-work and cordage when much exposed to wet1 which it resists better than anything else at the same price2 but the tar chiefly used for these purposes is that produced by burning fir or deal wood and condensing the tar in a pit below the stack of wood2 it is called ,stockholm tar1 as it comes chiefly from that place4 ,carbon only combines with nitrogen under peculiar circumstances4 ,this indirect combination is termed cyanogen 7,,cn74 ,it was discovered by ,gay-,lussac1 and is used for the production of ,prussian blue4 ,hydrocyanide of potassium 7,prussic acid7 is prepared by heating cyanide of potassium with sulphuric acid4 ,it is a deadly poison1 and found in peach-stones4 ,free cyanogen is a gas4 ,the bisulphide of carbon is a colourless1 transparent liquid4 ,it will easily dissolve sulphur and phosphorus and several resins4 ,when phosphorus is dissolved in it1 it makes a very dangerous 8fire10 and one difficult to extinguish4 ,we must now leave carbon and its combinations1 and come to sulphur4 ,illustration3 ,fig4 #chb4--,sulphur furnace4 ,,sulphur is found in a native state in ,sicily and many other localities which are volcanic4 ,it is a yellow1 solid body1 and as it is never perfectly free from earthy matter1 it must be purified before it can be used4 ,it possesses neither taste nor smell1 and is insoluble in water4 ,sulphur is purified in a retort1 ,c ,d1 which communicates with a brick chamber1 ,a4 ,the retort is placed over a furnace1 ,k1 and the vapour passes into the chimney through the tube1 ,d1 where it condenses into fine powder called 8flowers of sulphur0 7brimstone74 ,a valve permits the heated air to pass off1 while no exterior air can pass in1 for explosions would take place were the heated vapour to meet the atmospheric air4 ,the danger is avoided by putting an air reservoir outside the chimney which is heated by the furnace4 ,the sulphur is drawn out through the aperture1 r1 when deposited on the floor of the chamber4 ,the sulphur is cast into cylinders and sold4 ,sulphur is soluble in bisulphide of carbon1 and is used as a medical agent4 ,the compounds of sulphurs with oxygen form an interesting series4 ,there are two anhydrous oxides 7anhydrides71--viz41 sulphurous and sulphuric anhydride 7,,so#b and ,,so#c74 ,there are two notable acids formed by the combination with water1 sulphurous and sulphuric1 and some others1 which1 as in the case of nitrogen1 form a series of multiple proportions1 the oxygen being present in an increasing regularity of progression1 as follows3-- ,name of ,acid4 ,chemical ,formula4 ,hypo-sulphurous acid ,h#b,,so#b ,sulphurous acid ,h#b,,so#c ,sulphuric acid ,h#b,,so#d ,thio-sulphuric1 or hypo-sulphuric acid ,h#b,s#b,o#c ,dithionic acid ,h#b,s#b,o#f ,trithionic acid ,h#b,s#c,o#f ,tetrathionic acid ,h#b,s#d,o#f ,pentathionic acid ,h#b,s#e,o#f ,the last four are termed 8polythionic10 because the proportions of sulphur vary with constant proportions of the other constituents4 ,illustration3 ,fig4 #chc4--,liquefaction of sulphuric acid4 ,the sulphurous anhydride mentioned above is produced when we burn sulphur in the air1 or in oxygen2 it may be obtained in other ways4 ,it is a colourless gas1 and when subjected to pressure may be liquified1 and crystallized at very low temperature4 ,it was formerly called sulphuric acid4 ,it is a powerful 8reducing agent10 and a good antiseptic4 ,it dissolves in water1 and forms the ,h#b,,so#c1 now known as sulphurous acid4 ,illustration3 ,fig4 #chd4--,retorts and receivers for acid4 ,sulphuric acid is a most dangerous agent in wicked or inexperienced hands1 and amateurs should be very careful when dealing with it4 ,it takes the water from the moist air1 and from vegetable and animal substances4 ,it carbonizes and destroys all animal tissues4 ,its discovery is due to ,basil ,valentine1 in #addj4 ,he distilled sulphate of iron1 or green vitriol1 and the result was 8oil of vitriol40 ,it is still manufactured in this way in the ,hartz district1 and the acid passes by retorts into receivers4 ,the earthen retorts1 ,a1 are arranged in the furnace as in the illustration1 and the receivers1 ,b1 containing a little sulphuric acid1 are firmly fixed to them4 ,the oily brown product fumes in the air1 and is called 8fuming sulphuric acid10 or ,nordhausen acid4 ,sulphuric acid is very much used in chemical manufactures1 and the prices of many necessaries1 such as soap1 soda1 calico1 stearin1 paper1 etc41 are in close relationship with the cost and production of sulphur1 which also plays an important part in the making of gunpowder4 ,the manufacture of the acid is carried on in platinum stills4 ,illustration3 ,fig4 #che4--;,experiment to show the existence of gases in solution4 ,sulphuretted hydrogen1 or the hydric sulphide 7,h#b,s71 is a colourless and horribly-smelling gas1 and arises from putrefying vegetable and animal matter which contains sulphur4 ,the odour of rotten eggs is due to this gas1 which is very dangerous when breathed in a pure state in drains1 etc4 ,it can be made by treating a sulphide with sulphuric acid4 ,it is capable of precipitating the metals when in solution1 and so by its aid we can discover the metallic ingredient if it be present4 ,the gas is soluble in water1 and makes its presence known in certain sulphur springs4 ,the colour imparted to egg-spoons and fish-knives and forks sometimes is due to the presence of metallic sulphides4 ,the solution is called hydro-sulphuric acid4 ,,phosphorus occurs in very small quantities1 though in the form of phosphates we are acquainted with it pretty generally1 and as such it is absorbed by plants1 and is useful in agricultural operations4 ,in our organization--in the brain1 the nerves1 flesh1 and particularly in bones--phosphorus is present1 and likewise in all animals4 ,nevertheless it is highly poisonous4 ,it is usually obtained from the calcined bones of mammalia by obtaining phosphoric acid by means of acting upon the bone-ash with sulphuric acid4 ,phosphorus when pure is colourless1 nearly transparent1 soft1 and easily cut4 ,it has a strong affinity for oxygen4 ,it evolves white vapour in atmospheric air1 and is luminous2 to this element is attributable the luminosity of bones of decaying animal matter4 ,it should be kept in water1 and handled--or indeed not handled--but grasped with a proper instrument4 ,phosphorus is much used in the manufacture of lucifer matches1 and we are all aware of the ghastly appearance and ghostly presentment it gives when rubbed upon the face and hands in the dark4 ,in the ripples of the waves and under the counter of ships at sea1 the phosphorescence of the ocean is very marked4 ,in ,calais harbour we have frequently noticed it of a very brilliant appearance as the mail steamer slowly came to her moorings4 ,this appearance is due to the presence of phosphorus in the tiny animalcul of the sea4 ,it is also observable in the female glow-worm1 and the 8fire-fly40 ,phosphorus was discovered by ,brandt in #affi4 ,illustration3 ,fig4 #chf4--,manufacture of sulphuric acid4 ,it forms two compounds with oxygen-phosphorous acid1 ,h#b,,po#d1 and phosphoric acid1 ,h#c,,po#d4 ,the compound with hydrogen is well marked as phosphuretted hydrogen1 and is a product of animal and vegetable decomposition4 ,it may frequently be observed in stagnant pools1 for when emitted it becomes luminous by contact with atmospheric air4 ,there is a very pretty but not altogether safe experiment to be performed when phosphuretted hydrogen has been prepared in the following manner4 ,heat small pieces of phosphorus with milk of lime or a solution of caustic potash2 or make a paste of quick-lime and phosphorus1 and put into the flask with some quick-lime powdered4 ,fix a tube to the neck1 and let the other end be inserted in a basin of water4 7,see illustration1 fig4 #chh47 ,apply heat2 the phosphuretted hydrogen will be given off1 and will emerge from the water in the basin in luminous rings of a very beautiful appearance4 ,the greatest care should be taken in the performance of this very simple experiment4 ,no water must on any account come in contact with the mixture in the flask4 ,if even a drop or two find its way in through the bent tube a tremendous explosion will result1 and then the fire generated will surely prove disastrous4 ,the experiment can be performed in a cheaper and less dangerous fashion by dropping phosphate of lime into the basin4 ,we strongly recommend the latter course to the student unless he has had some practice in the handling of these inflammable substances1 and learnt caution by experience4 ,the effect when the experiment is properly performed is very good1 the smoke rising in a succession of coloured rings4 ,illustration3 ,fig4 #chg4--7,phosphuretted hydrogen and marsh gas7 ,will-o'-the-,wisp4 ,,silicon is not found in a free state in nature1 but1 combined with oxygen1 as ,silica it constitutes the major portion of our earth1 and even occurs in wheat stalks and bones of animals4 ,as flint or quartz 7see ,mineralogy7 it is very plentiful1 and in its purest form is known as rock crystal1 and approaches the form of carbon known as diamond4 ,when separated from oxygen1 silicon is a powder of greyish-brown appearance1 and when heated in an atmosphere of oxygen forms silicic 8acid0 again1 which1 however1 is not acid to the taste1 and is also termed 8silica10 or 8silex40 ,it is fused with great difficulty1 but enters into the manufacture of glass in the form of sand4 ,the chemical composition of glass is mixed silicate of potassium or sodium1 with silicates of calcium1 lead1 etc4 ,ordinary window-glass is a mixture of silicates of sodium and calcium2 crown glass contains calcium and silicate of potassium4 ,crystal glass is a mixture of the same silicate and lead4 ,flint glass is of a heavier composition4 ,glass can be coloured by copper to a gold tinge1 blue by cobalt1 green by chromium1 etc4 ,glass made on a large scale is composed of the following materials1 according to the kind of glass that is required4 ,flint glass 78crystal07 is very heavy and moderately soft1 very white and bright4 ,it is essentially a table-glass1 and was used in the construction of the ,crystal ,palace4 ,its composition is--pure white sea-sand1 #eb parts1 potash #ad parts1 oxide of lead1 #cd parts #ajj4 ,plate ,glass4 ,crown ,glass4 ,green 7,bottle7 ,glass4 ,pure white sand #ee parts4 ,fine sand #fc parts4 ,sea sand #hj parts4 ,soda #ce 0 ,chalk #g 0 ,salt #aj 0 ,nitre #h 0 ,soda #cj 0 ,lime #aj 0 ,lime #b 0 --- --- --- #ajj 0 #ajj 0 #ajj 0 ,the ingredients to be made into glass 7of whatever kind it may be7 are thoroughly mixed together and thrown from time to time into large crucibles placed in a circle1 ,a ,a 7fig4 #chi71 in a furnace resting on buttresses1 ,b ,b1 and heated to whiteness by means of a fire in the centre1 ,c1 blown by a blowing machine1 the tube of which is seen at ,d4 ,this furnace is shown in prospective in fig4 #cij4 ,the ingredients melt and sink down into a clear fluid1 throwing up a scum1 which is removed4 ,this clear glass in the fused state is kept at a white heat till all air-bubbles have disappeared2 the heat is then lowered to a bright redness1 when the glass assumes a consistence and ductility suitable to the purposes of the 8blower40 ,illustration3 ,fig4 #chh4--;,experiment with phosphuretted hydrogen4 ,glass blowing requires great care and dexterity1 and is done by twirling a hollow rod of iron on one end of which is a globe of melted glass1 the workman blowing into the other end all the time4 ,by reheating and twirling a sheet of glass is produced4 ,plate glass is formed by pouring the molten glass upon a table with raised edges4 ,when cold it is ground with emery powder1 and then polished by machinery4 ,illustration3 ,fig4 #chi4--;,crucibles4 ,many glass articles are cast1 or 8struck-up10 by compression in moulds1 and are made to resemble cut-glass1 but they are much inferior in appearance4 ,the best are first blown1 and afterwards cut and polished4 ,of whatever kind of glass the article may be1 it is so brittle that the slightest blow would break it1 a bad quality which is got rid of by a process called 8annealing10 that is1 placing it while quite hot on the floor of an oven1 which is allowed to cool very gradually4 ,this slow cooling takes off the brittleness1 consequently articles of glass well annealed are very much tougher than others1 and will scarcely break in boiling water4 ,illustration3 ,fig4 #cij4--,plate-glass casting--bringing out the pot4 ,the kind generally used for ornamental cutting is flint-glass4 ,decanters and wine-glasses are therefore made of it2 it is very bright1 white1 and easily cut4 ,the cutting is performed by means of wheels of different sizes and materials1 turned by a treadle1 as in a common lathe1 or by steam power2 some wheels are made of fine sandstone1 some of iron1 others of tin or copper2 the edges of some are square1or round1 or sharp4 ,they are used with sand and water1 or emery and water1 stone wheels with water only4 ,illustration3 ,fig4 #cia4--;,glass furnace4 7,see also fig4 #cij for detail47 ,illustration3 ,fig4 #cib4--;,glass-cutting4 ,in a soluble form silicic acid is found in springs1 and thus enters into the composition of most plants and grasses1 while the shells and scales of 8infusoria0 consist of silica4 ,as silicate of alumina1--i4e41 clay1--it plays a very important rle in our porcelain and pottery works4 99 99 99 99 99 ,,boron is found in volcanic districts1 in lakes as boracic acid1 in combination with oxygen4 ,it is a brownish-green1 insoluble powder1 in a free state1 but as boracic acid it is white4 ,it is used to colour fireworks with the beautiful green tints we see4 ,soda and boracic acid combine to make borax 7or biborate of soda74 ,another and inferior quality of this combination is tinkal1 found in ,thibet4 ,borax is much used in art and manufactures1 and in glazing porcelain4 7,symbol ,b1 ,atomic ,weight #aa74 ,,selenium is a very rare element4 ,it was found by ,berzilius in a sulphuric-acid factory4 ,it is not found in a free state in nature4 ,it closely resembles sulphur in its properties4 ,its union with hydrogen produces a gas1 seleniuretted hydrogen1 which is even more offensive than sulphuretted hydrogen4 7,symbol ,se1 ,atomic ,weight #gi74 ,,tellurium is also a rare substance generally found in combination with gold and silver4 ,it is like bismuth1 and is lustrous in appearance4 ,telluretted hydrogen is horrible as a gas4 ,tellurium1 like selenium1 sulphur1 and oxygen1 combines with two atoms of hydrogen4 7,symbol ,te1 ,atomic ,weight #abi74 ,illustration3 ,fig4 #cic4--;,casting plate-glass4 ,,arsenic1 like tellurium1 possesses many attributes of a metal1 and on the other hand has some resemblance to phosphorus4 ,arsenic is sometimes found free1 but usually combined with metals1 and is reduced from the ores by roasting2 and uniting with oxygen in the air1 is known as 8white arsenic40 ,the brilliant greens on papers1 etc41 contain arsenic1 and are poisonous on that account4 ,arsenic and hydrogen unite 7as do sulphur and hydrogen1 etc471 and produce a foetid gas of a most deadly quality4 ,this element also unites with sulphur4 ,if poured into a glass containing chlorine it will sparkle and scintillate as in the illustration 7fig4 #cie74 7,symbol ,as1 ,atomic ,weight #ge74 ,before closing this division1 and passing on to a brief review of the ,,metals1 we would call attention to a few facts connected with the metalloids we have been considering4 ,some1 we have seen1 unite with hydrogen only1 as chlorine2 some with two atoms of hydrogen1 as oxygen1 sulphur1 etc41 and some with three1 as nitrogen and phosphorus2 some again with four1 as carbon and silicon4 ,it has been impossible in the pages we have been able to devote to the ,metalloids to do more than mention each briefly and incompletely1 but the student will find sufficient1 we trust1 to interest him1 and to induce him to search farther1 while the general reader will have gathered some few facts to add to his store of interesting knowledge4 ,we now pass on to the ,metals4 ,illustration3 ,fig #cid--,the manufacture of porcelain in ,china4 ,illustration3 ,fig4 #cie4--;,experiment showing affinity between arsenic and chlorine4 ,,chapter ,,xxix4 ,,the ,,metals4 ,,what ,,metals ,,are--,,characteristics ,,and ,,general ,,properties ,,of ,,metals--,,classification--,,specific ,,gravity--,,descriptions4 ,we have learnt that the elements are divided into metalloids and metals1 but the line of demarcation is very faint4 ,it is very difficult to define what a metal is1 though we can say what it is not4 ,it is indeed impossible to give any absolute definition of a metal1 except as 8an element which does not unite with hydrogen1 or with another metal to form a chemical compound40 ,this definition has been lately given by ,mr4 ,spencer1 and we may accept it as the nearest affirmative definition of a metal1 though obviously not quite accurate4 ,a metal is usually supposed to be solid1 heavy1 opaque1 ductile1 malleable1 and tenacious2 to possess good conducting powers for heat and electricity1 and to exhibit a certain shiny appearance known as 8metallic lustre40 ,these are all the conditions1 but they are by no means necessary1 for very few metals possess them all1 and many non-metallic elements possess several4 ,the 8alkali0 metals are lighter than water2 mercury is a fluid4 ,the opacity of a mass is only in relation to its thickness1 for ,faraday beat out metals into plates so thin that they became transparent4 ,all metals are not malleable1 nor are they ductile4 ,tin and lead1 for example1 have very little ductility or tenacity1 while bismuth and antimony have none at all4 ,carbon is a much better conductor of electricity than many metals in which such power is extremely varied4 ,lustre1 again1 though possessed by metals1 is a characteristic of some non-metals4 ,so we see that while we can easily say what is not a metal1 we can scarcely define an actual metal1 nor depend upon unvarying properties to guide us in our determination4 ,illustration3 ,fig4 #cif4--,laminater4 ,the affinity of metals for oxygen is in an inverse ratio to their specific gravity1 as can be ascertained by experiment1 when the heaviest metal will be the least ready to oxidise4 ,metals differ in other respects1 and thus classification and division become easier4 ,the fusibility of metals is of a very wide range1 rising from a temperature below zero to the highest heat obtainable in the blow-pipe1 and even then in the case of osmium there is a difficulty4 ,while there can be no question that certain elements1 iron1 copper1 gold1 silver1 etc41 are metals proper1 there are many which border upon the line of demarcation very closely1 and as in the case of arsenic even occupy the debatable land4 ,,specific ,,gravity is the relation which the weight of substance bears to the weight of an equal volume of water1 as already pointed out in ,,physics4 ,the specific gravities of the metals vary very much1 as will be seen from the table following--water being1 as usual1 taken as #a3-- ,aluminium #bef ,antimony #fg ,arsenic #f ,bismuth #ig ,cadmium #hf ,calcium #ae ,chromium #fh ,cobalt #hi ,copper #hi ,gold #aic ,indium #gc ,iridium #baa ,iron #gh ,lead #aac ,lithium #eic ,magnesium #agd ,manganese #h ,mercury #ace ,molybdenum #hf ,nickel #hh ,osmium #bad ,palladium #aah ,platinum #bae ,potassium #hfe ,rhodium #aba ,rubidium #ae ,ruthenium #aad ,silver #aje ,sodium #igb ,strontium #be ,thallium #aah ,tin #gb ,titanium #ec ,tungsten #agf ,uranium #ahd ,zinc #ga ,zircon #dc ,some metals are therefore lighter and some heavier than water4 ,the table underneath gives the approximate fusing points of some of the metals 7,centigrade ,scale7-- 7,ice melts at #j47 ,platinum#ba about #aejj ,gold 0 #abjj ,silver 0 #ajjj ,cast iron #ajjj-abjj ,wrought iron 0 #aejj ,copper 0 #aajj ,antimony 0 #dcb ,zinc 0 #djj ,lead 0 #ccj ,bismuth 0 #bfe ,tin 0 #bce ,sodium 0 #ig ,potassium 0 #fj ,mercury 0 #dj ,there are some metals which1 instead of fusing1--that is1 passing from the solid to the liquid state1--go away in vapour4 ,these are volatile metals4 ,mercury1 potassium1 and sodium1 can be thus distilled4 ,some do not expand with heat1 but contract 7like ice71 antimony and bismuth1 for instance1 while air pressure has a considerable effect upon the fusing point4 ,some vaporise at once without liquefying2 others1 such as iron1 become soft before melting4 ,,alloys are combinations of metals which are used for many purposes1 and become harder in union4 ,amalgams are alloys in which mercury is one constituent4 ,some of the most useful alloys are under-stated3-- ,name of ,alloy4 ,composition4 ,aluminium bronze ,copper and aluminium4 ,bell metal ,copper and tin4 ,bronze 0 0 ,gun metal 0 0 ,brass ,copper and zinc4 ,dutch metal 0 0 ,mosaic gold 0 0 ,ormulu 0 0 ,tombac 0 0 ,german silver ,copper1 nickel1 and zinc4 ,britannia metal ,antimony and tin4 ,solder 0 0 ,pewter ,tin and lead4 ,type metal ,lead and antimony 7also copper at times74 ,shot ,lead and arsenic4 ,gold currency ,gold and copper4 ,silver currency ,silver and copper4 ,stereotype metal ,lead1 antimony1 and bismuth4 ,metals combine with chlorine1 and produce chlorides1 ,metals 0 0 sulphur 0 0 sulphides1 ,metals 0 0 oxygen 0 0 oxides1 and so on4 ,the metals may be classed as follows in divisions3-- ,metals of the alkalies as ,,potassium1 ,,sodium1 ,,lithium1 ,,ammonium4 ,metals of the alkaline earths as ,,barium1 ,,calcium1 ,,magnesium1 ,,strontium4 ,metals of the earths as ,,aluminium1 ,cerium1 ,didymium1 ,erbium1 ,glucinium1 ,lanthanum1 ,terbium1 ,thorium1 ,yttrium1 ,zirconium4 ,metals proper-- ,common ,metals as ,,iron1 ,,manganese1 ,,cobalt1 ,,nickel1 ,,copper1 ,bismuth1 ,,lead1 ,,tin1 ,,zinc1 ,,chromium1 ,antimony4 ,noble ,metals as ,,mercury1 ,,silver1 ,,gold1 ,,platinum1 ,palladium1 ,rhodium1 ,ruthenium1 ,osmium1 ,iridium4 ,we cannot attempt an elaborate description of all the metals1 but we will endeavour to give a few particulars concerning the important ones1 leaving many parts for ,mineralogy to supplement and enlarge upon4 ,we shall therefore mention only the most useful of the metals in this place4 ,we will commence with ,,potassium4 ,,metals ,,of ,,the ,,alkalies4 ,,potassium has a bright1 almost silvery1 appearance1 and is so greatly attracted by oxygen that it cannot be kept anywhere if that element be present--not even in water1 for combustion will immediately ensue on water2 and in air it is rapidly tarnished4 ,it burns with a beautiful violet colour1 and a very pretty experiment may easily be performed by throwing a piece upon a basin of water4 ,the fragment combines with the oxygen of the water1 the hydrogen is evolved1 and burns1 and the potassium vapour gives the gas its purple or violet colour4 ,the metal can be procured by pulverizing carbonate of potassium and charcoal1 and heating them in an iron retort4 ,the vapour condenses into globules in the receiver1 which is surrounded by ice in a wire basket4 ,it must be collected and kept in naphtha1 or it would be oxidised4 ,potassium was first obtained by ,sir ,humphrey ,davy in #ahjg4 ,potash is the oxide of potassium1 and comes from the 8ashes0 of wood4 ,illustration3 ,fig4 #cig4--,preparation of potassium4 ,the compounds of potassium are numerous1 and exist in nature1 and by burning plants we can obtain potash 78pearlash074 ,nitrate of potassium1 or nitre 7saltpetre71 7,,kno#c71 is a very important salt4 ,it is found in the ,east ,indies4 ,it is a constituent of gunpowder1 which consists of seventy-five parts of nitre1 fifteen of charcoal1 and ten of sulphur4 ,the hydrated oxide of potassium1 or 8caustic potash0 7obtained from the carbonate71 is much used in soap manufactories4 ,it is called 8caustic0 from its property of cauterizing the tissues4 ,iodide1 bromide1 and cyanide of potassium1 are used in medicine and photography4 ,soap is made by combining soda 7for hard soap71 or potash 7for soft soap71 with oil or tallow4 ,yellow soap has turpentine1 and occasionally palm oil1 added4 ,oils and fats combine with metallic oxides1 and oxide of lead with olive oil and resin forms the adhesive plaister with which we are all familiar when the mixture is spread upon linen4 ,fats boiled with potash or soda make soaps2 the glycerine is sometimes set free and purified as we have it4 ,sometimes it is retained for glycerine soap4 ,fancy soap is only common soap coloured4 ,white and brown ,windsor are the same soap--in the latter case browned to imitate age6 ,soap is quite soluble in spirits1 but in ordinary water it is not so greatly soluble1 and produces a lather1 owing to the lime in the water being present in more or less quantity1 to make the water more or less 8hard40 ,illustration3 ,fig4 #cih4--,machine for cutting soap in bars4 ,illustration3 ,fig4 #cii4--,soap-boiling house4 ,,sodium is not unlike potassium1 not only in appearance1 but in its attributes2 it can be obtained from the carbonate1 as potassium is obtained from its carbonate4 ,soda is the oxide of sodium1 but the most common and useful compound of sodium is the chloride1 or common salt1 which is found in mines in ,england1 ,poland1 and elsewhere4 ,salt may also be obtained by the evaporation of sea water4 ,rock salt is got at ,salzburg1 and the ,german salt mines and works produce a large quantity4 ,the ,carbonate of ,soda is manufactured from the chloride of sodium1 although it can be procured from the salsoda plants by burning4 ,the chloride of sodium is converted into sulphate1 and then ignited with carbonate of lime and charcoal4 ,the soluble carbonate is extracted in warm water1 and sold in crystals as soda1 or 7anhydrous7 8soda ash40 ,the large quantity of hydrochloric acid produced in the first part of the process is used in the process of making chloride of lime4 ,a few years back1 soda was got from ,hungary and various other countries where it exists as a natural efflorescence on the shores of some lakes1 also by burning sea-weeds1 especially the common bladder wrack 7,fucus vesiculosus71 the ashes of which were melted into masses1 and came to market in various states of purity4 ,the bi-carbonate of soda is obtained by passing carbonic acid gas over the carbonate crystals4 ,soda does not attract moisture from the air4 ,it is used in washing1 in glass manufactories1 in dyeing1 soap-making1 etc4 ,sulphate of ,soda is 8,glauber's ,salt02 it is also employed in glass-making4 ,mixed with sulphuric acid and water1 it forms a freezing mixture4 ,glass1 as we have seen1 is made with silicic acid 7sand71 soda1 potassa1 oxide of lead1 and lime1 and is an artificial silicate of soda4 ,,lithium is the lightest of metals1 and forms the link between alkaline and the alkaline earth metals4 ,the salts are found in many places in solution4 ,the chloride when decomposed by electricity yields the metal4 ,c,,sium and ,,rubidium require no detailed notice from us4 ,they were first found in the solar spectrum1 and resemble potassium4 ,,ammonium is only a conjectural metal4 ,ammonia1 of which we have already treated1 is so like a metallic oxide that chemists have come to the conclusion that its compounds contain a metallic body1 which they have named hypothetically ,,ammonium4 ,it is usually classed amongst the alkaline metals4 ,the salts of ammonia are important1 and have already been mentioned4 ,muriate 7chloride7 of ammonia1 or sal-ammoniac1 is analogous to chloride of sodium and chloride of potassium4 ,it is decomposed by heating it with slaked lime1 and then gaseous ammonia is given off4 ,illustration3 ,fig4 #djj4--,mottled soap-frames4 ,,the ,,metals ,,of ,,the ,,alkaline ,,earths4 ,,barium is the first of the four metals we have to notice in this group1 and will not detain us long1 for it is little known in a free condition4 ,its most important compound is heavy spar 7sulphate of baryta71 which1 when powdered1 is employed as a white paint4 ,the oxide of barium1 ,ba,o1 is termed baryta4 ,nitrate of ,baryta is used for 8green fire10 which is made as follows3--,sulphur1 twenty parts2 chlorate of potassium1 thirty-three parts2 and nitrate of baryta1 eighty parts 7by weight74 ,illustration3 ,fig4 #dja4--,soda furnace4 99 99 99 99 99 ,,calcium forms a considerable quantity of our earth's crust4 ,it is the metal of lime1 which is the oxide of calcium4 ,in a metallic state it possesses no great interest1 but its combinations are very important to us4 ,lime is1 of course1 familiar to all4 ,it is obtained by evolving the carbonic acid from carbonate of lime 7,ca,o74 ,the properties of this lime are its white appearance1 and it develops a considerable amount of heat when mixed with water1 combining to make hydrate of lime1 or 8slaked lime40 ,this soon crumbles into powder1 and as a mortar attracts the carbonic acid from the air1 by which means it assumes the carbonate and very solid form1 which renders it valuable for cement and mortar1 which1 when mixed with sand1 hardens4 ,caustic lime is used in whitewashing1 etc4 ,carbonate of ,lime 7,ca,c,o#c7 occurs in nature in various forms1 as limestone1 chalk1 marble1 etc4 ,calc-spar 7arragonite7 is colourless1 and occurs as crystals4 ,marble is white 7sometimes coloured by metallic oxides71 hard1 and granular4 ,chalk is soft and pulverizing4 ,it occurs in mountainous masses1 and in the tiniest shells1 for carbonate of lime is the main component of the shells of the crustacea1 of corals1 and of the shell of the egg2 it enters likewise into the composition of bones1 and hence we must regard it as one of the necessary constituents of the food of animals4 ,it is an almost invariable constituent of the waters we meet with in ,nature1 containing1 as they always do1 a portion of carbonic acid1 which has the power of dissolving carbonate of lime4 ,but when gently warmed1 the volatile gas is expelled1 and the carbonate of lime deposited in the form of white incrustations upon the bottom of the vessel1 which are particularly observed on the bottoms of tea-kettles1 and if the water contains a large quantity of calcareous matter1 even our water-bottles and drinking-glasses become covered with a thin film of carbonate of lime4 ,these depositions may readily be removed by pouring into the vessels a little dilute hydrochloric acid1 or some strong vinegar1 which in a short time dissolves the carbonate of lime4 ,sulphate of ,lime 7,ca,s,o#d7 is found in considerable masses1 and is commonly known under the name of ,gypsum4 ,it occurs either crystallized or granulated1 and is of dazzling whiteness2 in the latter form it is termed ,alabaster1 which is so soft as to admit of being cut with a chisel1 and is admirably adapted for various kinds of works of art4 ,gypsum contains water of crystallization1 which is expelled at a gentle heat4 ,but when ignited1 ground1 and mixed into a paste with water1 it acquires the property of entering into chemical combination with it1 and forming the original hydrate1 which in a short time becomes perfectly solid4 ,thus it offers to the artist a highly valuable material for preparing the well-known plaster of ,paris figures1 and by its use the noblest statues of ancient and modern art have now been placed within the reach of all4 ,gypsum1 moreover1 has received a valuable application as manure4 ,in water it is slightly soluble1 and imparts to it a disagreeable and somewhat bitterish1 earthy taste4 ,it is called 8selenite0 when transparent4 ,phosphate of ,lime constitutes the principal mass of the bones of animals1 and is extensively employed in the preparation of phosphorus2 in the form of ground bones it is likewise used as a manure4 ,it appears to belong to those mineral constituents which are essential to the nutrition of animals4 ,it is found in corn and cereals1 and used in making bread2 so we derive the phosphorus which is so useful to our system4 ,chloride of ,lime is a white powder smelling of chlorine1 and is produced by passing the gas over the hydrate of lime spread on trays for the purpose4 ,it is the well-known 8bleaching powder40 ,it is also used as a disinfectant4 ,the ,fluoride of ,calcium is ,derbyshire spar1 or 8,blue ,john40 ,fluor spar is generally of a purple hue4 ,we may add that hard water can be softened by adding a little powdered lime to it4 99 99 99 99 99 ,,magnesium sometimes finds a place with the other metals1 for it bears a resemblance to zinc4 ,magnesium may be prepared by heating its chloride with sodium4 ,salt is formed1 and the metal is procured4 ,it burns very brightly1 and forms an oxide of magnesia 7,mg,o74 ,magnesium appears in the formation of mountains occasionally4 ,it is ductile and malleable1 and may be easily melted4 ,carbonate of ,magnesia1 combining with carbonate of lime1 form the ,dolomite ,hills4 ,when pure1 the carbonate is a light powder1 and when the carbonic acid is taken from it by burning it is called ,calcined ,magnesia4 ,the ,sulphate of ,magnesia occurs in sea-water1 and in saline springs such as ,epsom4 ,it is called 8,epsom ,salts40 ,magnesium wire burns brightly1 and may be used as an illuminating agent for final scenes in private theatricals4 ,magnesite will be mentioned among ,minerals4 99 99 99 99 99 ,,strontium is a rare metal1 and is particularly useful in the composition of 8red-fire40 ,there are the carbonate and sulphate of strontium2 the latter is known as ,celestine4 ,the red fire above referred to can be made as follows1 in a dry mixture4 ,ten parts nitrate of strontia1 #a parts chlorate of potassium1 #c parts of sulphur1 #a part sulphide of antimony1 and part charcoal4 ,mix well without moisture1 enclose in touch paper1 and burn4 ,a gorgeous crimson fire will result4 ,,metals ,,of ,,the ,,earths4 ,,aluminium 7,aluminum7 is like gold in appearance when in alloy with copper1 and can be procured from its chloride by decomposition with electricity4 ,it occurs largely in nature in composition with clays and slates4 ,its oxide1 alumina 7,al#b,o#c71 composes a number of minerals1 and accordingly forms a great mass of the earth4 ,alumina is present in various forms 7see ,minerals7 in the earth1 all of which will be mentioned under ,crystallography and ,mineralogy4 ,the other nine metals in this class do not call for special notice4 ,,heavy ,,metals ,,iron1 which is the most valuable of all our metals1 may fitly head our list4 ,so many useful articles are made of it1 that without consideration any one can name twenty4 ,the arts of peace and the glories of war are all produced with the assistance of iron1 and its occurrence with coal has rendered us the greatest service1 and placed us at the head of nations4 ,it occurs native in meteoric stones4 ,iron is obtained from certain ores in ,england and ,sweden1 and these contain oxygen and iron 7see ,mineralogy74 ,we have thus to drive away the former to obtain the latter4 ,this is done by putting the ores in small pieces into a blast furnace 7fig4 #djb7 mixed with limestone and coal4 ,the process of severing the metal from its ores is termed smelting1 the air supplied to the furnace being warmed1 and termed the 8hot blast40 ,the 8cold blast0 is sometimes used4 ,the ores when dug from the mine are generally stamped into powder1 then 8roasted10--that is1 made hot1 and kept so for some time to drive off water1 sulphur1 or arsenic1 which would prevent the 8fluxes0 acting properly4 ,the fluxes are substances which will mix with1 melt1 and separate the matters to be got rid of1 the chief being charcoal1 coke1 and limestone4 ,the ore is then mixed with the flux1 and the whole raised to a great heat2 as the metal is separated it melts1 runs to the bottom of the 8smelting furnace10 and is drawn off into moulds made of sand2 it is thus cast into short thick bars called 8pigs10 so we hear of pig-iron1 and pig-lead4 ,iron is smelted from 8ironstone10 which is mixed with coke and limestone4 ,the heat required to smelt iron is so very great1 that a steam-engine is now generally employed to blow the furnace4 7,before the invention of the steam-engine1 water-mills were used for the same purpose47 ,the smelting is conducted in what is called a blast furnace4 ,when the metal has all been 8reduced10 or melted1 and run down to the bottom of the furnace1 a hole is made1 out of which it runs into the moulds2 this is called 8tapping the furnace40 ,illustration3 ,fig4 #djb4--;,blast furnace4 ,smelting is often confounded with melting1 as the names are somewhat alike1 but the processes are entirely different2 in melting1 the metal is simply liquefied1 in smelting1 the metal has to be produced from ores which often have no appearance of containing any1 as in the case of ironstone1 which looks like brown clay4 ,the cone of the furnace1 ,a1 is lined with fire-bricks1 i i1 which is encased by a lining1 l l2 outside are more fire-bricks1 and then masonry1 m n2 ,c is the throat of the furnace2 ,d the chimney4 ,the lower part1 ,b1 is called the boshes4 ,as soon as the ore in the furnace has become ignited the carbon and oxygen unite and form carbonic acid1 which escapes1 and the metal fuses at last and runs away4 ,the coal and ore are continually added year after year4 ,the glassy scum called 8slag 8 protects the molten iron from oxidation4 ,the metal drawn from the blast furnace is 8pig iron10 or 8cast0 iron1 and contains carbon4 ,this kind of iron is used for casting operations1 and runs into sand-moulds4 ,it contracts very little when cooling4 ,it is hard and brittle4 ,illustration3 ,fig4 #djc4--;,general foundry1 ,woolwich ,arsenal4 ,illustration3 ,fig4 #djd4--,wire rollers4 ,illustration3 ,fig4 #dje4--;,cutting edges4 ,bar ,iron is the almost pure metal4 ,it is remarkably tenacious1 and may be drawn into very fine wire or rolled4 ,but it is not hard enough for tools4 ,it is difficult to fuse1 and must be welded by hammering at a red heat4 ,wire-drawing is performed by taking the metal as a bar1 and passing it between rollers 7fig4 #djd71 which flattens it1 and then between a new set1 which form cutting edges on the rolled plate 7fig4 #dje71 the projections of one set fitting into the hollows of the other closely as in the illustration4 ,the strips of metal come out at the aperture seen at ,a in the next illustration4 ,these rods are drawn through a series of diminishing holes in a steel plate1 occasionally being heated to keep it soft and ductile4 ,when the wire has got to a certain fineness it is attached to a cylinder and drawn away1 at the same time being wound round the cylinder over a small fire4 ,some metals can be drawn much finer than others4 ,gold wire can be obtained of a 8thickness0 7or thinness7 of only the #e1jjjth part of an inch1 #eej feet weighing one grain6 ,but platinum has exceeded this marvellous thinness1 and wire the #cj1jjjth part of an inch has been produced4 ,ductility and malleability are not always found in the same metal in proportion4 ,the sizes of wires are gauged by the instrument shown in the margin4 ,the farther the wire will go into the groove the smaller its 8size40 ,illustration3 ,fig4 #djf4--,rollers4 ,illustration3 ,fig4 #djg4--,wire size4 ,steel contains a certain amount of carbon1 generally about #a to #b per cent4 ,cast steel is prepared from cast iron4 ,steel from bar-iron has carbon added1 and is termed bar-steel4 ,the process is called 8cementation10 and is carried on by packing the bars of iron in brick-work boxes1 with a mixture of salt and soot1 or with charcoal1 which is termed 8cement40 ,steel is really a carbide of iron1 and ,mr4 ,bessemer founded his process of making steel by blowing out the excess of carbon from the iron1 so that the proper amount--#ae per cent4--should remain4 ,illustration3 ,fig4 #djh4--;,coarse wire-drawing4 ,a brief summary of the ,bessemer process may be interesting4 ,if a bar of steel as soft as iron be made red-hot and plunged into cold water1 it will become very hard4 ,if it be then gently heated it will become less hard1 and is then fitted for surgical instruments4 ,the various shades of steel are carefully watched1--the change of colour being due to the varying thickness of the oxide2 for we know that when light falls upon very thin films of a substance1--soap-bubbles1 for instance1--the light reflected from the under and upper surfaces interfere1 and cause colour1 which varies with the thickness of the film4 ,these colours in steel correspond to different temperatures1 and the 8temper0 of the steel depends upon the temperature it has reached4 ,the following table extracted from ,haydn's 8,dictionary of ,science0 gives the 8temper10 the colour1 and the uses of the various kinds of steel4 ,illustration3 ,fig4 #dji4--;,fine wire-drawing4 ,temperature ,colour4 ,uses of ,steel4 ,cent4 ,fahr4 ---------------------------------------- ---------------------------- #bbj #dcj ,faint yellow ,lancets4 #bcb #dej ,pale straw ,best razors and surgical instruments4 #bdc #dgj ,yellow ,ordinary razors1 pen-knives1 etc4 #bed #dij ,brown ,small shears1 scissors1 cold chisels1 etc4 #bfe #eaj ,brown and purple ,axes1 pocket-knives1 plane-irons1 etc4 spots #bgg #ecj ,purple ,table-knives1 etc4 #bhh #eej ,light blue ,swords1 watch-springs1 etc4 #bic #efj ,full blue ,fine saws1 daggers1 etc4 #caf #fjj ,dark blue ,hand and pit saws4 ,the ,bessemer process transfers the metal into a vessel in which there are tubes1 through which air is forced1 which produces a much greater heat than a bellows does4 ,thus in the process the carbon of the iron acts as fuel to maintain the fusion1 and at the same time by the bubbling of the carbonic acid mixes the molten iron thoroughly4 ,during the bubbling up of the whole mass of iron1 and the extreme elevation of temperature caused by the union of the carbon of the impure iron with the oxygen of the air1 the oxide of iron is formed1 and as fast as it forms fuses into a sort of glass2 this unites with the earthy matters of the 8impure0 iron1 and floats on the upper part as a flux1 thus ridding the 8cast iron0 of all its impurities1 with no other fuel than that contained in the metal itself1 and in the air used4 ,when the flame issuing from the 8converter0 contracts and changes its colour1 then the time is known to have arrived when the iron is 8 de-carbonized40 ,the amount of carbon necessary is artificially added1 ebullition takes place1 a flame of carbonic oxide comes out1 and the metal is then run into ingots4 ,the compounds of iron which are soluble in water have a peculiar taste called chalybeate 7like ink74 ,many mineral springs are so flavoured1 and taste1 as the immortal ,samuel ,weller put it1 8like warm flat-irons40 ,iron is frequently used as a medicine to renew the blood globules4 ,protoxide of ,iron is known only in combination4 ,sesqui-,oxide of ,iron is 8red ironstone40 ,powdered it is called ,english rouge1 a pigment not altogether foreign to our use4 ,in a pure state it is a remedy for arsenical poisoning1 and is really the 8rust0 upon iron4 ,illustration3 ,fig4 #daj4--;,bessemer's process4 ,bisulphide of ,iron is iron pyrites1 and is crystalline4 ,chloride of ,iron is dissolved from iron with hydrochloric acid4 ,it is used in medicine4 ,cyanide of ,iron makes1 with cyanide of potassium1 the well-known prussiate of potash 7ferro-cyanide of potassium71 which1 when heated1 precipitates ,prussian blue 7cyanogen and iron74 ,the ,sulphate of the ,protoxide is known as copperas1 or green vitriol1 and is applied to the preparation of ,prussian blue4 99 99 99 99 99 ,,manganese is found extensively1 but not in any large quantities1 in one place2 iron ore contains it4 ,it is very hard to fuse1 and is easily oxidised4 ,the binoxide is used to obtain oxygen1 and when treated with potassium and diluted1 it becomes the permanganate of potassium1 and is used as 8,condy's fluid40 ,it readily oxides organic matters1 and is thus a disinfectant4 ,it crystallizes in long1 deep1 red needles1 which are dissolved in water4 ,it is a standard laboratory test4 ,there are other compounds1 but in these pages we need not detail them4 99 99 99 99 99 ,,cobalt and ,,nickel occur together4 ,they are hard1 brittle1 and fusible4 ,the salts of cobalt produce beautiful colours1 and the chloride yields an 8invisible0 or sympathetic ink4 ,the oxide of cobalt forms a blue pigment for staining glass which is called 8smalt40 ,nickel is chiefly used in the preparation of ,german silver and electro-plating4 ,the salts of nickel are green4 ,nickel is difficult to melt1 and always is one of the constituents of meteoric iron1 which falls from the sky in arolites4 ,it is magnetic like cobalt1 and is extracted from the ore called kupfer-nickel4 ,a small ,united-,states coin is termed a 8nickel40 99 99 99 99 99 ,,copper is the next metal we have to notice4 ,it has been known for centuries4 ,it is encountered native in many places4 ,the ,cornish copper ore is the copper pyrites4 ,the fumes of the smelting works are very injurious1 containing1 as they do1 arsenic and sulphur4 ,the ground near the mines is usually bare of vegetation in consequence of the 8smoke40 ,sheet copper is worked into many domestic utensils1 and the alloy with zinc1 termed ,brass1 is both useful and ornamental4 ,red brass is beaten into thin leaves1 and is by some supposed to be 8gold leaf02 it is used in decorative work4 ,bronze is also an alloy of copper1 as are gun-metal1 bell-metal1 etc4 ,illustration3 ,fig4 #daa4--,native copper4 ,next to silver1 copper is the best conductor of electricity we have4 ,it is very hard and tough1 yet elastic1 and possesses malleability and ductility in a high degree4 ,it forms two oxides1 and there are several sulphides2 the principal of the latter are found native1 and worked as ores4 ,the sulphate of copper is termed blue vitriol1 and is used in calico-printing1 and from it all the 7copper7 pigments are derived4 ,it is also used in solution by agriculturists to protect wheat from insects4 ,when copper or its alloys are exposed to air and water1 a carbonate of copper forms1 which is termed verdigris4 ,all copper salts are poisonous2 white of eggs is an excellent remedy in such cases of poisoning4 99 99 99 99 99 ,,lead is obtained from galena1 a sulphide of lead4 ,it is a soft and easily-worked metal4 ,when freshly cut it has quite a bright appearance1 which is quickly tarnished4 ,silver is often present in lead ore1 and is extracted by ,pattison's process1 which consists in the adaptation of the knowledge that lead containing silver becomes solid1 after melting1 at a lower temperature than lead does when pure4 ,pure lead therefore solidifies sooner4 ,one great use of lead is for our domestic water-pipes1 which remind us in winter of their presence so disagreeably4 ,shot is made from lead1 and bullets are cast from the same metal4 ,shot-making is very simple1 and before the days of breech-loading guns and cartridges1 no doubt many readers have cast bullets in the kitchen and run them into the mould over a basin of water or a box of sand4 ,for sporting purposes lead is mixed with arsenic1 and when it is melted it is poured through a sort of sieve 7as in the cut7 at the top of a high tower4 7,see figs4 #dac and #dad74 ,the latter illustration gives the section of the shot tower2 ,a is the furnace1 ,b is the tank for melting the lead1 and the metal is permitted by the workman at ,c to run through the sieve in fine streams4 ,as the lead falls it congeals into drops1 which are received in water below to cool them4 ,they are1 of course1 not all round1 and must be sorted4 ,this operation is performed by placing them on a board tilted up1 and under which are two boxes4 ,the round shot rush over the first holes and drop into the second box1 but the uneven ones are caught lagging1 and drop into box ,no4 #a4 ,they are accordingly sent to the furnace again4 ,illustration3 ,fig4 #dab4--,shot tower4 ,the next process is to sort the good shot for size4 ,this is done by sieves--one having holes a little larger than the size of shot required4 ,this sieve passes through it all of the right size and smaller1 and keeps the bigger ones4 ,those that have passed this examination are then put into another sieve1 which has holes in it a little smaller than the size of shot wanted4 ,this sieve retains the right shot1 and lets the smaller sizes pass1 and so on4 ,the shot are sized and numbered1 glazed by rolling them in a barrel with graphite1 and then they are ready for use4 ,bullets are made by machinery by the thousand1 and made up into cartridges with great speed4 ,illustration3 ,fig4 #dac4--,sieve for making shot4 ,the compounds of lead are also poisonous1 and produce 8colic10 to which painters are subject4 ,red lead1 or minium1 is a compound of the protoxide and the binoxide1 and may be found native4 ,the former oxide is litharge2 white lead1 or the carbonate of lead1 is a paint1 and is easily obtained by passing a stream of carbonic acid into a solution of acetate of lead4 ,it is used as a basis of many paints4 ,illustration3 ,fig4 #dad4--,section of shot tower4 ,illustration3 ,fig4 #dae4--,preparing lead for bullets4 ,,tin is another well-known metal4 ,it is mentioned by ,moses4 ,it possesses a silver-like lustre1 and is not liable to be oxidised4 ,the only really important ore is called ,tinstone1 from which the oxygen is separated1 and the metal remains4 ,cornwall has extensive tin mines4 ,tin is malleable and ductile1 and can be beaten into foil or 8silver leaf10 or drawn into wire4 ,it prevents oxidation of iron if the latter be covered with it1 and for tinning copper vessels for culinary purposes4 ,the ,romans found tin in ,cornwall1 and the term 8,stanneries0 was applied to the courts of justice among the tin miners in ,edward the ,first's time4 ,we have already mentioned the alloys of tin4 ,the oxides of tin1 8,stannous0 and 8,stannic10 are useful to dyers4 ,the latter is the tinstone 7,sn,o#b74 ,sulphide of tin is called 8,mosaic gold10 and is much used for decorative purposes4 ,,zinc is procured from calamine1 or carbonate of zinc1 and blende1 or sulphide of zinc4 ,it has for some years been used for many purposes for which lead was once employed1 as it is cheap and light4 ,zinc is a hard metal of a greyish colour1 not easily bent1 and rather brittle2 but when made nearly red-hot1 it can be rolled out into sheets or beaten into form by the hammer4 ,zinc is about six-and-three-quarter times heavier than water4 ,like many other metals1 it is volatile 7when heated to a certain extent it passes off into vapour71 and the probable reason that it was not known or used of old is that it was lost in the attempt to smelt its ores4 ,zinc is now obtained by a sort of distillation2 the ores are mixed with the flux in a large earthen crucible or pot4 ,we have already noticed the alloy of zinc with copper 7brass71 and the use of zinc to galvanize iron by covering the latter with a coating of zinc in a bath is somewhat analogous to electro-plating4 ,the metal is largely used as the positive element in galvanic batteries1 and for the production of hydrogen in the laboratory4 ,zinc forms one oxide 7,zn,o71 used for zinc-white4 ,the sulphate of zinc is white vitriol1 and the chloride of zinc is an 8antiseptic40 ,certain preparations of the metal are used in medicine as 8ointments0 or 8washes10 and are of use in inflammation of the eyelids4 ,,chromium4 ,this 8metallic element0 is almost unknown in the metallic state4 ,but although little known1 the beautiful colours of its compounds make it a very interesting study4 ,the very name leads one to expect something different to the other metals--chroma1 colour4 ,the metal is procured from what is known as chrome-ironstone1 a combination of protoxide of iron and sesqui-oxide of chromium 7,fe,o,cr#b,o#c74 ,by ignition with potassium we get chromic acid and chromate of potassium1 a yellow salt which is used to make the other compounds of chromium4 ,the metal is by no means easy to fuse4 ,sesqui-,oxide of ,chromium is a fine green powder employed in painting porcelain4 ,chromate of ,lead is termed 8chrome yellow10 and in its varieties is employed as a paint4 ,chromate of ,mercury is a beautiful vermilion4 ,there are numerous other combinations which need not be mentioned here4 ,illustration3 ,fig4 #daf4--,type-casting4 ,,antimony was discovered by ,basil ,valentine4 ,the ,latin term is ,stibium1 hence its symbol1 ,sb4 ,it is very crystalline1 and of a peculiar bluish-white tint4 ,it will take fire at a certain high temperature1 and can be used for the manufacture of 8,bengal ,lights10 with nitre and sulphur in the proportions of antimony 8one10 the others two and three respectively4 ,the compounds of antimony are used in medicine1 and are dangerous when taken without advice4 ,they act as emetics if taken in large quantities4 ,our 8tartar emetic0 is well known4 ,antimony1 in alloy with lead and a little tin1 form the type metal to which we are indebted for our printing4 ,type-casting is done by hand1 and requires much dexterity4 ,a ladle is dipped into the molten metal1 and the mould jerked in to fill it properly1 and then the type is removed and the mould shut ready for another type2 and a skilful workman can perform these operations five hundred times in an hour1--rather more than eight times a minute1--producing a type each time2 this has afterwards to be finished off by others4 ,the metal of which type is made consists of lead and antimony2 the antimony hardens it and makes it take a sharper impression4 ,the letters are first cut in steel1 and from these 8dies0 the moulds are made in brass1 by stamping1 and in these the types are cast4 ,stereotype consists of plates of metal taken1 by casting1 from a forme of type set up for the purpose3 an impression was formerly carried on by plaster-of-,paris moulds1 but lately what is termed the papier-mach process is adopted4 ,the paper used is now made in ,england1 and the prepared sheet is placed upon the type and beaten upon it4 ,paste is then filled in where there are blanks1 and another and thicker sheet of the prepared paper is placed over all1 dried1 and pressed4 ,when this is properly done the paper is hardened1 and preserves an impression of the type set up4 ,the paper mould is then put into an iron box1 and molten metal run in4 ,in a very short time a 8stereotype0 plate is prepared from the paper1 which can be used again if necessary4 ,the metal plate is put on the machine4 ,there are several compounds of antimony1 which1 though valuable to chemists1 would not be very interesting to the majority of readers4 ,we will therefore at once pass to the ,noble ,metals4 ,,the ,,noble ,,metals4 ,there are nine metals which rank under the above denomination3--,mercury1 ,silver1 ,gold1 ,platinum1 ,palladium1 ,rhodium1 ,ruthenium1 ,osmium1 ,iridium4 ,we will confine ourselves chiefly to the first four on the list4 ,,mercury1 or ,,quicksilver1 is the first of the metals which remain unaltered by exposure to atmospheric air1 and thus are supposed to earn their title of nobility4 ,mercury is familiar to us in our barometers1 etc41 and is fluid in ordinary temperatures1 though one of the heaviest metals we possess4 ,it is principally obtained from native cinnabar1 or sulphide of mercury 7vermilion71 and the process of extraction is very easy4 ,mercury was known to the ancients1 and is sometimes found native4 ,in the mines the evil effects of the contact with mercury are apparent4 ,this metal forms two oxides1--the black 7mercurous7 oxide1 or suboxide 7,hg#b,o71 and the red 7mercuric7 oxide1 or red precipitate4 ,the chlorides are two1--the subchloride1 or calomel1 and the perchloride1 or corrosive sublimate4 ,the sulphides correspond with the oxides2 the mercuric sulphide has been mentioned4 ,its crimson colour is apparent in nature1 but the ,chinese prepare it in a particularly beautiful form4 ,many amalgams are made with mercury1 which is useful in various ways that will at once occur to the reader4 ,,silver is the whitest and most beautiful of metals1 and its use for our plate and ornaments is general4 ,it is malleable and ductile1 and the best conductor of electricity and heat that we have4 ,it is not unfrequently met with in its native state1 but more generally it is found in combination with gold and mercury1 or in lead1 copper1 and antimony ores4 ,the mines of ,peru and ,mexico1 with other ,western ,states of ,america1 are celebrated--,nevada1 ,colorado1 and ,utah in particular4 ,the story of the silver mine would be as interesting as any narrative ever printed4 ,the slavery and the death-roll would equal in horror and in its length the terrible records of war or pestilence4 ,we have no opportunity here to follow it1 or its kindred metals with which it unites1 on the sentimental side2 but were the story of silver production written in full1 it would be most instructive4 ,illustration3 ,fig4 #dag4--,native silver4 ,silver is found with lead 7galena71 which is then smelted4 ,the lead is volatilized1 and the silver remains4 ,it is also extracted by the following process1 wherein the silver and golden ore is crushed and washed1 and quicksilver1 salt1 and sulphate of copper added1 while heat is applied to the mass4 ,from tank to tank the slime flows1 and deposits the metals1 which are put into retorts and heated4 ,the mercury flies off2 the silver and gold remain in bars4 ,in some countries1 as in ,saxony and ,south ,america1 recourse is had to another process1 that of amalgamation1 which depends on the easy solubility of silver and other metals in mercury4 ,the ore1 after being reduced to a fine powder1 is mixed with common salt1 and roasted at a low red heat1 whereby any sulphide of silver the ore may contain is converted into chloride4 ,the mixture is then placed1 with some water and iron filings1 in a barrel which revolves round its axis1 and the whole agitated for some time1 during which process the chloride of silver becomes reduced to the metallic state4 ,a portion of mercury is then introduced1 and the agitation continued4 ,the mercury combines with the silver1 and the amalgam is then separated by washing4 ,it is afterwards pressed in woollen bags to free it from the greater part of the mercury1 and then heated1 when the last trace of mercury volatilizes and leaves the silver behind4 ,nitrate of ,silver is obtained when metallic silver is dissolved in nitric acid4 ,it is known popularly as lunar caustic1 and forms the base of 8marking inks40 ,chloride of silver is altered by light1 but the iodide of silver is even more rapidly acted on1 and is employed in photography4 ,fulminating silver is oxide of silver digested in ammonia4 ,it is very dangerous in inexperienced hands4 ,it is also prepared by dissolving silver in nitric acid1 and adding alcohol4 ,it cools in crystals4 ,fulminating mercury is prepared in the same way4 ,,gold is the most valuable of all metals1--the 8king of metals10 as it was termed by the ancients4 ,it is always found 8native10 frequently with silver and copper4 ,quartz is the rock wherein it occurs4 ,from the disintegration of these rocks the gold sands of rivers are formed1 and separated from the sands by 8washing40 ,in ,australia and ,california 8nuggets0 are picked up of considerable size4 ,it is a rather soft metal1 and1 being likewise costly1 is never used in an absolutely pure state4 ,coins and jewellery are all alloyed with copper and silver to give them the requisite hardness and durability4 ,gold is extremely ductile1 and very malleable4 ,one grain of gold may be drawn into a wire five hundred feet in length1 and the metal may be beaten into almost transparent leaves #a_/bjjjjj of an inch in thickness6 ,illustration3 ,fig4 #dah4--,native gold4 ,aqua-regia1 a mixture of hydrochloric and nitric acids1 is used to dissolve gold1 which is solved only by selenic acid1 though the free chlorine will dissolve it4 ,faraday made many experiments as to the relation of gold to light4 7,see 8,phil4 ,trans410 #aheg1 p4 #ade47 ,the various uses of gold are so well known that we need not occupy time and space in recording them4 ,gilding can be accomplished by immersing the articles in a hot solution of chloride of gold and bicarbonate of potash mixed2 but the electro process is that now in use1 by which the gold precipitates on the article to be plated4 ,we have already described the process of electro-plating in the case of silvered articles1 and we need only mention that electro-gilding is performed very much in the same way4 ,but gilding is also performed in other ways2 one of which1 the so-called water gilding1 is managed as follows4 ,gilding with the gold-leaf is merely a mechanical operation1 but water-gilding is effected by chemistry4 ,water-gilding is a process 7in which1 however1 no water is used7 for covering the surface of metal with a thin coating of gold2 the best metal for water-gilding is either brass1 or a mixture of brass and copper4 ,a mixture of gold and mercury1 in the proportion of one part of gold to eight of mercury1 is made hot over a fire till they have united2 it is then put into a bag of chamois-leather1 and the superfluous mercury pressed out4 ,what remains is called an 8amalgam02 it is soft1 and of a greasy nature1 so that it can be smeared over any surface with the fingers4 ,the articles to be gilt are made perfectly clean on the surface1 and a liquid1 made by dissolving mercury in nitric acid 7aqua-fortis71 is passed over them with a brush made of fine brass wire1 called a 8scratch-brush40 ,the mercury immediately adheres to the surface of the metal1 making it look like silver2 when this is done1 a little of the amalgam is rubbed on1 and the article evenly covered with it4 ,it is then heated in a charcoal fire till all the mercury evaporates1 and the brass is left with a coating of gold1 which is very dull1 but may be burnished with a steel burnisher and made bright if necessary4 ,in former times articles were inlaid with thin plates of gold1 which were placed in hollows made with a graver1 and melted in1 a little borax being applied between4 ,when a solution of 8chloride of gold0 is mixed with ether1 the ether takes the gold away from the solution1 and may be poured off the top charged with it4 ,this solution1 if applied to polished steel by means of a camel-hair pencil1 rapidly evaporates1 leaving a film of gold adhering to the steel1 which1 when burnished with any hard substance1 has a very elegant appearance4 ,in this way any ornamental design in gold may be produced1 but it is not very durable4 ,the gilt ornaments1 scrolls1 and mottoes on sword-blades1 are sometimes done in this way4 ,,platinum is the heaviest of all metals1 gold being next4 ,platinum is practically infusible1 and quite indifferent to reagents4 ,it is therefore very useful in certain manufactories1 and in the laboratory4 ,it can be dissolved by aqua-regia4 ,the stills for sulphuric acid are made of platinum1 and the metal is used for ,russian coinage1 but must be very difficult to work on account of its infusible property4 ,in the finely-divided state it forms a gray and very porous mass1 which is known as spongy platinum1 and possesses the remarkable property of condensing gases within its pores4 ,hence1 when a jet of hydrogen is directed upon a piece of spongy platinum1 the heat caused by its condensation suffices to inflame the gas4 ,this singular power has been applied to the construction of a very beautiful apparatus1 known as ,dbereiner's lamp1 which consists of a glass jar1 a1 covered by a brass lid1 e1 which is furnished with a suitable stop-cock1 c1 and in connection with a small bell jar1 f1 in which is suspended1 by means of a wire1 a cylinder of metallic zinc1 z4 ,when required for use1 the outer jar is two-thirds filled with a mixture of one part sulphuric acid and four parts water1 and the stop-cock opened to allow the escape of atmospheric air1 the spongy platinum contained in the small brass cylinder1 d1 being covered by a piece of paper4 ,the stop-cock is then closed1 and the bell jar1 f1 allowed to fill with hydrogen1 and after it has been filled and emptied several times1 the paper is removed from the platinum and the cock is again opened1 when the gas1 which escapes first1 makes the metal red-hot and finally inflames4 ,this property of platinum is also used in the 8,davy0 lamp4 ,illustration3 ,fig4 #dai4--;,dbereiner's lamp4 ,the remaining metals do not call for detailed notice4 ,in conclusion1 we may refer to the following statement1 which in general terms gives the properties of the metals1 their oxides and sulphides for ordinary readers4 ,,general ,,classification ,,of ,,the ,,metals4 7,transcriber's ,note3 ,the table has been divided into two parts to fit within width constraints7 ,the metals admit of being really distinguished by the following table1 in which they are presented in several groups1 according to their peculiar properties1 and each distinguished by a particular name3-- --------------------------------------- ,,metals4 -------------------------------------- 7,a47 ,light ,metals4 ,specific gravity from #jh to #a2 never occur in the uncombined state4 -------------------------------------- 7a47 ,alkaline ,metals4 #a4 ,potassium4 #b4 ,sodium4 7,ammonium47 -------------------------------------- 7b47 ,metals of the ,alkaline ,earths4 #c4 ,calcium4 #d4 ,barium4 #e4 ,strontium4 -------------------------------------- 7c47 ,metals of the ,earths proper4 #f4 ,magnesium4 #g4 ,aluminium4 -------------------------------------- 7,b47 ,heavy ,metals4 ,specific gravity from #e to #ba2 are found chiefly in combination with oxygen1 and frequently with sulphur and arsenic2 some are native4 -------------------------------------- 7a47 ,common ,metals4 ,become oxidized in the air4 #h4 ,iron4 #ad4 ,lead4 #i4 ,manganese4 #ae4 ,tin4 #aj4 ,cobalt4 #af4 ,zinc4 #aa4 ,nickel4 #ag4 ,chromium4 #ab4 ,copper4 #ah4 ,antimony4 #ac4 ,bismuth4 -------------------------------------- 7b47 ,noble ,metals4 ,unchangeable in the air4 #ai4 ,mercury4 #ba4 ,gold4 #bj4 ,silver4 #bb4 ,platinum4 --------------------------------------- ---------------------------------------- ---------------------------------- ,properties of the ---------------------------------------- -------------------------------- ,oxides4 ,sulphides4 ---------------------------------------- ------------------------------- ,a,powerful bases2 possessing a ,powerful bases1 which oxidize in strong affinity for water1 and the air1 and form sulphates2 form with it hydrates4 ,they when treated with acids evolve yield their oxygen to carbon hydrosulphuric acid4 only at a white heat4 ---------------------------------------- ------------------------------- a,highly caustic2 powerful bases1 ,caustic2 strong bases2 very soluble separate all other oxides from in water1 and dissolve a their combinations with acids2 large quantity of sulphur1 which are very soluble in water1 and is separated on addition of an do not lose their water of acid as a white powder1 termed hydration at the highest milk of sulphur2 they were temperatures2 attract carbonic formerly termed liver of sulphur4 acid rapidly from the air4 ---------------------------------------- ------------------------------- b,caustic2 strong bases2 slightly ,caustic2 strong bases2 dissolve soluble in water2 lose their sulphur1 and are partly soluble water of hydration at a moderate in water1 and partly insoluble4 heat1 and powerfully absorb carbonic acid4 ---------------------------------------- ------------------------------- c ,weak bases1 ,insoluble in water4 ,feebly caustic4 insoluble in ,not caustic4 water4 ---------------------------------------- ------------------------------- ,b,feebler bases than the foregoing1 ,neutral compounds2 insoluble in some are acids2 insoluble in water2 antimony and several water1 and lose their water of of the rarer metals produce hydration at a moderate heat4 compounds with sulphur1 which deport themselves as acids4 ---------------------------------------- ------------------------------- a,with few exceptions1 are soluble ,those occurring in nature are in acids1 and1 when ignited with somewhat brass-like in appearance1 carbon at a red heat1 yield and are termed pyrites their oxygen2 are1 for the most and blendes4 ,those which are part1 fusible and non-volatile4 artificially prepared have peculiarcolours2 by heat they are converted into sulphates4 ---------------------------------------- ------------------------------- b,have more the properties of acids ,with the exception of sulphide than of bases2 are decomposed of mercury1 they leave the pure by ignition into oxygen and metal when ignited4 metal4 ---------------------------------------- ---------------------------------- ,,footnotes3 #ba ,requires oxy-hydrogen blow-pipe4 ,,chapter ,,xxx4 ,,organic ,,chemistry4 ,,radicals--,,acids--,,bases--,,neutrals 4 ,in the introduction to these brief chapters upon ,chemistry1 we said that the science was divided into two sections1 the first section consisting of the simple combinations1 and the other of compound combinations4 ,the latter being met with chiefly in animal and vegetable matter1 as distinguished from dead or inert matter1 was termed ,organic4 ,this distinction will be seen below4 ,,combinations ,,of ,,simple ,,groups4 ,,inorganic4 ,i4 ,elements and their ,combinations4 7#a7 ,non-,metallic4 7#b7 ,metallic4 ,,ii4 ,peculiar ,decompositions of the above4 7#a7 ,by ,electricity4 7#b7 ,by ,light4 ,,combinations ,,of ,,compound ,,groups4 ,,organic4 ,i4 ,compound ,radicals and their ,combinations4 ,,ii4 ,peculiar ,decompositions of the above4 7#a7 ,spontaneous4 7#b7 ,dry ,distillation4 ,we have already placed before our readers the elements and their simple combinations1 and have incidentally mentioned the decomposition by electricity and by light4 ,in the section upon ,electricity the positive and negative poles are explained4 ,oxygen appears always at the positive pole1 potassium at the negative4 ,the other simple bodies vary4 ,chlorine1 in combination with oxygen1 is evolved at the negative pole1 but when with hydrogen at the positive pole4 ,in the series below each element behaves electro-negatively to those following it1 and electro-positively to those above it2 and the farther they are apart the stronger their opposite affinities are4 ,,electrical ,,relation ,,of ,,the ,,elements4 ,oxygen4 ,sulphur4 ,nitrogen4 ,chlorine4 ,bromine4 ,iodine4 ,fluorine4 ,phosphorus4 ,arsenic4 ,carbon4 ,chromium4 ,boron4 ,antimony4 ,silicium4 ,gold4 ,platinum4 ,mercury4 ,silver4 ,copper4 ,bismuth4 ,lead4 ,cobalt4 ,nickel4 ,iron4 ,zinc4 ,hydrogen4 ,manganese4 ,aluminium4 ,magnesium4 ,calcium4 ,strontium4 ,barium4 ,sodium4 ,potassium4 ,the importance of these facts to science is unmistakable1 and1 indeed1 many attempts have been made to explain1 from the electrical condition of the elements1 the nature of chemical affinity1 and of chemical phenomena in general4 ,electrotyping is another instance of decomposition by means of electricity1 and respecting decomposition by light we know how powerful the action of the sun's rays are upon plants1 and for the evolution of oxygen4 ,the daguerreotype and photographic processes are also instances which we have commented upon4 ,so we can pass directly to the consideration of the compound groups4 ,in nearly every complex organic compound we have a relatively simple one of great stability1 which is termed the radical1 which forms1 with other bodies1 a compound radical4#bb ,in these complex groups we find certain elements generally1--viz41 carbon1 hydrogen1 nitrogen1 sulphur1 and phosphorus4 ,some compounds may consist of two of these1 but the majority contain three 7hydrogen1 oxygen1 and carbon74 ,many have four 7carbon1 oxygen1 hydrogen1 and nitrogen71 and some more than four1 including phosphorus and sulphur4 ,others1 again1 may contain chlorine and its relatives1 arsenic1 etc41 in addition4 ,now we will all admit that in any case in which carbon is present in composition with other simple bodies forming an organic body1 and if that body be ignited in the air1 it burns and leaves 7generally7 a black mass4 ,this is a sure test of the presence of carbon1 and forms an organic compound4 ,similarly in decomposition nitrogen and sulphur in combination inform us they are present by the odour they give off4 ,we need not go farther into this question of radicals and compound radicals than to state that a compound radical plays the part of an element in combination4 ,we find in alcohol and ether a certain combination termed ,ethyl4 ,this 8compound radical0 occurs in same proportions in ether1 chloride of ethyl1 iodide of ethyl1 etc41 as ,c#b;,h#e2 so it really acts as a simple body or element1 though it is a compound of carbon and hydrogen4 ,a simple radical is easily understood2 it is an element1 like potassium1 for instance4 ,we may now pass to the organic combinations classified into ,,acids1 ,,bases1 and ,,indifferent1 or ,,neutral1 ,,bodies4 ,i4 ,,acids4 ,there are several well-known organic acids1 which we find in fruits and in plants4 ,they are volatile and non-volatile2 acids are sometimes known as 8,salts of ,hydrogen40 ,we have a number of acids whose names are familiar to us1--viz41 acetic1 tartaric1 citric1 malic1 oxalic1 tannic1 formic1 lactic1 etc4 ,acetic acid 7,,hc#b;,h#d,o#b7 is a very important one1 and is easily found when vegetable juices1 which ferment1 are exposed to the air1 or when wood and other vegetable matter is subjected to the process of 8dry distillation40 ,vinegar contains acetic acid1 which is distilled from wood1 as we shall see presently4 ,vinegar is made abroad by merely permitting wine to get sour2 hence the term ,vin-aigre4 ,in ,england vinegar is made from 8wort10 of malt which is fermented for a few days1 and then put into casks1 the bung-holes of which are left open for several weeks1 until the contents have become quite sour4 ,the liquid is then cleared by isinglass4 ,the vinegar of commerce contains about #f per cent4 of pure acetic acid1 and some spirit1 some colouring matter1 and1 of course1 water4 ,wood vinegar 7pyroligneous acid7 is used for pickles4 ,the ordinary vinegar when distilled is called white vinegar1 and it may also be obtained from fruits1 such as gooseberries or raspberries4 ,illustration3 ,fig4 #dbj4--,vinegar ground4 ,illustration3 ,fig4 #dba4--;,boiler or copper4 ,acetic acid1 or 8wood vinegar10 is prepared as follows3--,there are some large iron cylinders set in brickwork over furnaces1 and these cylinders have each a tube leading to a main pipe in which the liquid is received for condensation4 ,the cylinders1 which contain about seven or eight hundredweight1 are filled with logs of wood1 either oak1 beech1 birch1 or ash1 the door is closely fastened1 and the joints smeared with clay2 the fires are now lighted and kept up all day1 till the cylinders are red-hot2 at night they are allowed to cool4 ,in the morning1 the charcoal1 into which the wood is now converted1 is withdrawn1 and a fresh charge supplied2 it is then found that about thirty or forty gallons of liquid has condensed in the main tube from each cylinder1 the remainder being charcoal and gases which pass off2 the liquid is acid1 brown1 and very offensive1 and contains acetic acid1 tar1 and several other ingredients1 among which may be named creosote2 it is from this source all the creosote1 for the cure of toothache1 is obtained4 ,to purify this liquid it is first distilled1 and this separates much of the tar2 it is then mixed with lime1 evaporated to dryness1 and heated to expel the remaining tar and other impurities2 it is next mixed with sulphate of soda and water1 and the whole stirred together2 the soda1 now in union with the acetic acid1 is washed out from the lime and strained quite clear2 it is afterwards evaporated till it crystallises1 and vitriol 7sulphuric acid7 then added2 finally the acetic acid is distilled over1 and the sulphuric acid left in union with the soda1 forming sulphate of soda1 to be used in a similar process for the next batch of acid4 ,the acetic acid is now quite colourless1 transparent1 and very sour1 possessing a fragrant smell4 ,this is not pure acetic acid1 but contains a considerable quantity of water4 ,the acetic acid of commerce1 mixed with seven times its bulk of water1 forms an acid of about the strength of malt vinegar1 perfectly wholesome1 and agreeable as a condiment4 ,illustration3 ,fig4 #dbb4--,vinegar-cooling process4 ,illustration3 ,fig4 #dbc4--,tan-yard and pits4 ,pure acetic acid may be made by mixing dry acetate of potash with oil of vitriol in a retort1 and distilling the acetic acid into a very cold receiver2 this1 when flavoured with various volatile oils1 forms the aromatic vinegar sold by druggists4 ,it is a very strong acid1 and if applied to the skin will quickly blister it4 ,acetate of lead1 or sugar of lead1 is obtained by dissolving oxide of lead in vinegar4 ,a solution of this salt makes the goulard water so familiar to all4 ,acetate of lead is highly poisonous4 ,acetate of copper is verdigris1 and poisonous4 ,other acetates are used in medicine4 ,we may pass quickly over some other acids4 ,they are as follows3-- ,,tartaric ,,acid 7,c#d;,h#f,o#f7 is contained in grape juice1 and crystallizes in tabular form4 ,the purified powdered salt is cream of ,tartar4 ,,citric ,,acid 7,c#f;,h#h,o#g7 is found native in citrons and lemons1 as well as in currants and other fruits4 ,it is an excellent anti-scorbutic4 ,,malic ,,acid 7,c#d;,h#f,o#e7 is found chiefly in apples1 as its name denotes 7malum1 an apple74 ,it is prepared from mountain-ash berries4 ,,oxalic ,,acid 7,c#b;,h#b,o#d74 ,if we heat sugar with nitric acid we shall procure this acid4 ,it is found in sorrel plants4 ,,tannic ,,acid 7,c#bg;,h#bb,o#ag74 ,it is assumed that all vegetables with an astringent taste contain this acid4 ,tannin is known for its astringent qualities4 ,the name given to this acid is derived from the fact that it possesses a property of forming an insoluble compound with water1 known as leather4 ,tanning is the term employed4 ,tannin is found in many vegetable substances1 but oak bark is usually employed1 being the cheapest4 ,the 8pelts10 hides1 or skins1 have first to be freed from all fat or hair by scraping1 and afterwards soaking them in lime and water4 ,then they are placed in the tan-pit between layers of the bark1 water is pumped in1 and the hides remain for weeks1 occasionally being moved from pit to pit1 or relaid1 so as to give all an equal proportion of pressure1 etc4 ,the longer the leather is tanned--it may be a year--the better it wears4 ,skins for gloves and binding are tanned with 8sumach10 or alum and salt4 ,sometimes the leather is split by machinery for fine working4 ,parchment is prepared from the skins of asses1 sheep1 goats1 and calves1 which are cleaned1 and rubbed smooth with pumice stone4 ,tannic acid1 with oxide of iron1 produces ,ink1 for the gall-nut contains a quantity of the acid4 ,all the black inks in use generally are composed of green vitriol 7sulphate of iron7 in union with some astringent vegetable matter2 the best is the gall-nut1 although1 for cheapness1 logwood and oak bark have each been used4 ,an excellent black ink may be made by putting into a gallon stone bottle twelve ounces of bruised galls1 six ounces of green vitriol1 and six of common gum1 and filling up the bottle with rain water2 this should be kept three or four weeks before using1 shaking the bottle from time to time4 ,blue ink has lately been much used2 it is made by dissolving newly-formed ,prussian blue in a solution of oxalic acid4 ,to make it1 dissolve some yellow prussiate of potash in water in one vessel1 and some sulphate of iron in another1 adding a few drops of nitric acid to the sulphate of iron2 now mix the two liquids1 and a magnificent blue colour will appear1 in the form of a light sediment2 this is to be put upon a paper filter1 and well washed by pouring over it warm water1 and allowing it to run through2 a warm solution of oxalic acid should now be mixed with it1 and the ,prussian blue will dissolve into a bright blue ink4 ,illustration3 ,fig4 #dbd4--,unhairing the hide4 ,red ink is made by boiling chips or raspings of ,brazil wood in vinegar1 and adding a little alum and gum2 it keeps well1 and is of a good colour4 ,a red ink of more beautiful appearance1 but not so durable1 may be made by dissolving a few grains of carmine in two or three teaspoonfuls of spirit of hartshorn4 ,marking ink is made by dissolving nitrate of silver in water1 and then adding some solution of ammonia1 a little gum water1 and some ,indian ink to colour it4 ,printers' ink is made by grinding drying oil with lamp-black4 ,the powdered gall-nut is an excellent test for iron in water4 ,it will turn violet if any iron be present4 ,,formic ,,acid 7,,ch#b,o#b7 is the caustic means of defence employed by ants1 hence the term formic4 ,it can be artificially prepared by distilling a mixture of sugar1 binoxide of manganese1 and sulphuric acid4 ,on the skin it will raise blisters4 ,illustration3 ,fig4 #dbe4--;,drying rooms for hides4 ,,lactic ,,acid 7,c#c;,h#f,o#c7 is present in vegetable and animal substances4 ,sour whey contains it1 and the presence of the acid in the whey accounts for its power of removing from table-linen stains4 ,when what is called 8lactic fermentation0 occurs1 milk is said to be 8turned40 ,,ii4 ,,bases4 ,the definition of a base is not easy4 ,we have described bases as substances which1 combining with acids1 form salts1 but the definition of a base is as unsatisfactory as that of acid or salt4 ,all vegetable bases contain nitrogen1 are usually very bitter1 possess no smell or colour1 and are insoluble in water4 ,they are usually strong poisons1 but very useful in medicine4 ,the most important are the following bases3-- ,,quinine is contained in the cinchona 7yellow7 bark4 ,one hundred parts of the bark have been calculated to yield three of quinine4 ,,morphine is the poisonous base of opium1 which is the juice of the poppy1 and is prepared chiefly in ,india and ,china4 ,,nicotine is the active principle of tobacco1 and varies in quantity in different tobaccos4 ,havannah tobacco possesses the least4 ,it is a powerful poison1 very oily1 volatile1 and inflammable4 ,,conia is prepared from the hemlock4 ,it is fluid and volatile4 ,it is also a deadly poison1 and paralyses the spine directly4 ,illustration3 ,fig4 #dbf4--;,hemlock4 ,,strychnine is found in poisonous trees1 particularly in the nux-vomica seeds of ,coromandel4 ,it produces lock-jaw and paralysis4 ,there is no antidote for strychnine2 emetics are the only remedy4 ,the above are chiefly remarkable for their uses in medicine1 and in consequence of their highly poisonous character are best left alone by unpractised hands4 ,a ,german chemist1 named ,serturner1 was the first to extract the active principle from ,opium4 ,the question of opium importation has lately been attracting much attention1 and the opinions concerning its use are divided4 ,probably in moderation1 and when used by ordinary people 7not demoralized creatures71 it does little harm4 ,illustration3 ,fig4 #dbg4--,the ,poppy4 ,opium is the juice of the 8common0 poppy1 and derives its name from the ,greek opos1 juice4 ,the plant is cultivated in ,india1 ,persia1 and ,turkey4 ,after the poppy has flowered the natives go round1 and with a sharp instrument wound1 or puncture1 every poppy head4 ,this is done very early in the morning1 and under the influence of the sun during the day the juice oozes out4 ,next morning the drops are scraped off4 ,the juice is then placed in pots1 dried1 and sent for export4 ,the 8construction0 of opium is very complicated1 for it contains a number of ingredients1 the most important being morphia1 narcotine1 meconic acid1 and codeia4 ,it is to the first named constituent that the somnolent effect of opium is due4 ,,iii4 ,,indifferent ,,substances4 ,there are a great number of so-called 8indifferent0 substances to which we cannot be indifferent4 ,such bodies as these have neither acid nor basic properties1 and stand no comparison with salts4 ,they are of great importance1 forming1 as they do1 the principal nutriment of animals4 ,some contain nitrogen1 some do not2 they may therefore be divided into nitrogenous and non-nitrogenous substances2 the former for solid portions of the body1 the latter for warmth4 ,we will take the latter first1 and speak of some of them--such as starch1 gum1 sugar1 etc4 ,,starch is found in the roots of grain1 in the potato1 dahlia1 artichoke1 etc41 and by crushing the parts of the plant1 and washing them1 the starch can be collected as a sediment4 ,in cold water and in spirits of wine starch is insoluble4 ,the various kinds of starch usually take their names from the plants whence they come4 ,arrowroot is obtained from the ,west ,indian plant ,maranta ,arundinacea4 ,cassava and tapioca are from the manioc2 sago1 from the sago palm2 wheat starch1 and potato starch are other examples4 ,illustration3 ,fig4 #dbh4--,plantation of sugar-canes4 ,if starch be baked in an oven at a temperature of about #cjj it becomes1 to a great extent1 soluble in cold water1 forming what is called 8,british gum02 this is largely used for calico printing and other purposes2 if boiled in water under great pressure1 so that the temperature can be raised to the same degree1 it is also changed into an adhesive sort of gum1 8mucilage02 this is the substance made use of by the government officials to spread over the backs of postage and receipt stamps to make them adhere4 ,the starch of grain1 during germination1 or growth1 contains diastase1 which converts the starch into gum and sugar2 the same effect can be produced by heating starch with diluted sulphuric acid4 ,,gum found in plants is chiefly procured from the ,mimosa trees1 from which it flows in drops1 and is called ,gum ,arabic4 ,there are other so-called 8gums10 but this is the one generally referred to4 ,,sugar exists in fruits1 roots1 and in the stalks of plants1 in the juice of the cane1 maple1 and beet-root particularly4 ,the canes are crushed1 the juice is clarified with lime to prevent fermentation1 and the liquid is evaporated4 ,it is then granulated and cleared from the molasses4 ,sugar1 when heated1 becomes dark1 and is called 8caramel40 ,it is used for colouring brandy1 and gives much difficulty to the sugar refiners4 ,illustration3 ,fig4 #dbi4--,refining vacuum pan4 ,sugar refining is conducted as follows4 ,the raw 7brown7 sugar is mixed into a paste with water1 and allowed to drain4 ,the sugar thus becomes white4 ,it is then dissolved in water1 with animal charcoal and bullocks' blood4 ,the liquid is boiled1 and put into a dark cistern with holes at the bottom1 and cotton fibres being fastened in the holes1 are hung into another dark cistern1 into which the liquid runs pure and white4 ,it is then pumped into a copper vessel1--vacuum pan1--and condensed to the proper consistence4 ,subsequently it is poured into conical moulds1 and pure syrup poured upon the crystal shapes4 ,the caramel is then removed through a hole at the end4 ,the moulds or loaves are then dried1 and if not even or elegant they are turned in a lathe4 ,finally they are packed up as 8loaf sugar40 ,sugar undergoes no decomposition1 and is the cause of non-decomposition in other substances4 ,for this reason it is employed in 8preserving0 fruit1 etc4 ,sugar is obtained from beet by crushing and rasping the roots1 as the cane is treated4 ,illustration3 ,fig4 #dcj4--,sugar moulds4 ,illustration3 ,fig4 #dca4--,turning the loaves4 ,,spirit ,,of ,,wine1 ,,or ,,alcohol1 is not a natural product4 ,it is found by the decomposition of grape-sugar by fermentation4 ,there is a series of alcohols which exhibit a regular gradation1 founded1 so to speak1 upon one1 two1 or three molecules of water4 ,they are called respectively alcohols1 glycols1 and glycerins4 ,thus we have-- ,alcohols4 ,methylic alcohol4 ,ethylic 0 ,prophylic 0 ,amylic 0 ,glycols4 ,enthelein glycol4 ,prophylene 0 ,butylene 0 ,amylene 0 ,glycerins4 7,ordinary ,glycerine is the only one known47 ,the cetyl and melissylic alcohols are contained in spermaceti and bees-wax respectively4 ,the usual alcohol is the ,vinic1 a transparent1 colourless liquid1 which is the spirituous principle of wine1 spirits1 and beer1 and when sugar is fermented the alcohol and carbonic acid remain4 ,spirits of wine has a very powerful affinity for water1 and thus the use of stimulants in great quantity is to be deprecated1 for alcohol absorbs the water from the mucous membranes of the stomach and the mouth1 making them dry and hard4 ,the state of 8intoxication10 unfortunately so familiar1 is the effect produced by alcohol upon the nerves4 ,we append a list of the beverages which are most in use1 and the percentage of alcohol in each according to ,professor ,hart3-- ,port #ae per cent4 ,madeira #ade 0 ,sherry #ad 0 ,claret #h 0 ,ale #f 0 ,porter #e 0 ,spirit of wine is contained in many mixtures1 and for the purpose of ascertaining how much alcohol may be in wine1 or any other liquid1 a hydrometer is used 7fig4 #dcb74 ,this instrument consists of a glass tube with a bulb at the end4 ,it is put into water1 and the place the water 8cuts0 is marked by a line on the stem1 and called zero #j4 ,spirit of wine has less specific gravity than water1 so in absolute alcohol the instrument will sink lower than in water1 and will descend to a point which is marked #ajj4 ,in any mixture of alcohol and water1 of course the hydrometer will rise or sink between the extreme points accordingly as the mixture may contain less alcohol or more4 ,so a scale can be furnished4 ,the instrument1 as described1 was invented by ,,mm4 ,gay-,lussac and ,tralles1 and called the 8percentage0 hydrometer4 ,there are many other instruments marked in a more or less arbitrary manner4 ,we append a comparative table of a few hydrometers4 7,see page #dbj47 ,illustration3 ,fig4 #dcb4--;,hydrometer4 ,,ether1 or sulphuric ether1 is a mixture of spirits of wine with sulphuric acid1 and distilled4 ,it loses water1 and the product is ether1 which is volatile1 and transparent1 with a peculiarly penetrating odour4 ,it will not mix with water1 and if inhaled will produce a similar effect to chloroform4 ,,comparative ,,table ,,of ,,hydrometers4 ---------------------------------------- -------------------------- ,specific ,percentage ,percentage ,degree1 ,degree1 ,degree1 ,gravity4 ,volume ,weight1 according according according 7,tralles74 at #fj ,f4 to ,cartier4 to ,beck4 to ,baum4 ---------------------------------------- -------------------------- #ajjj #j #j #aj #j #aj #jiia #e #dj 444 444 444 #jihe #aj #hj #ab 444 444 #jihj #ae #aba 444 #c #ac #jige #bj #afb 444 444 444 #jigj #be #bjd #ad #e 444 #jifd #cj #bdf #ae #f #ae #jieh #ce #bhi 444 444 #af #jiea #dj #ccd 444 #i #ag #jidb #de #cgi #ah 444 444 #jicc #ej #dbe 444 #ab #bj #jibc #ee #dgb #ba #ad 444 #jiab #fj #ebb 444 #af #bd #jija #fe #egb #bd #ai 444 #jhhi #gj #fbe #bg 444 #bh #jhgf #ge #fgi 444 #bd 444 #jhfc #hj #gce #cj #bg #cb #jhdh #he #gie #ce #cj #ce #jhcc #ij #heg 444 #cd #ch #jhae #ie #ibd #dj #ch #db #jgic #ajj #ajjj #dd #dd #dh ---------------------------------------- -------------------------- ,chloroform is transparent1 and will sink in water4 ,diluted alcohol with hypo-chloride of lime1 will produce it4 ,when inhaled1 chloroform produces a pleasing insensibility to pain1 and is useful in surgery4 ,a certain compound of alcohol with mercury dissolved in nitric acid will cause decomposition1 and white crystals will eventuate4 ,these compound crystals are termed fulminating mercury4 99 99 99 99 99 ,we must now pass rapidly over the few remaining subjects we have to notice1 such as fats and soaps1 wax1 oils1 etc4 ,fats are of the greatest use to man1 particularly in cold climates1 for upon them depends the heat of the body4 ,fatty acid1 if liquid1 is known as oleic acid2 if solid1 stearic acid4 ,soaps are compounds of fatty acids4 ,many 8fats0 are consumed as food1 others as fuel or for lighting purposes1 in the shape of oils4 ,such oils are not primarily useful for burning4 ,petroleum and other mineral oils are found in enormous quantities in ,america4 ,there are what we term fixed oils1 and essential or volatile oils4 ,a list is annexed as given by 8,hadyn's ,dictionary of ,science03-- ,,fixed ,,oils4 ,drying4 ,linseed oil4 ,poppy oil4 ,sunflower oil4 ,walnut oil4 ,tobacco-seed oil4 ,cress-seed oil4 ,non-,drying4 ,almond oil4 ,castor oil4 ,colza oil4 ,oil of mustard4 ,rape-seed oil4 ,olive oil1 etc4 ,,essential ,,oils4 ,oil of anise4 ,oil of bergamot4 ,oil of carraway4 ,oil of cassia4 ,oil of cedar4 ,oil of cloves4 ,oil of lavender4 ,oil of lemon4 ,oil of mint4 ,oil of myrrh4 ,oil of nutmeg4 ,oil of peppermint4 ,oil of rose4 ,oil of turpentine4 ,vegetable oils are obtained by crushing seeds2 animal oils come from the whale and seal tribe4 ,paraffin oil comes from coal4 ,linseed is a very drying oil1 and on it depends the drying power of paint4 ,we know olive oil will not dry on exposure to the air4 ,oiled silk is made with linseed oil4 ,when oil is drying in the air considerable heat is evolved1 and if oiled substances be left near others likely to catch fire1 spontaneous combustion may ensue4 ,oil of turpentine is found in the pine and fir trees1 and many of the oils above mentioned are used by perfumers1 etc41 the rose oil1 or attar of roses1 being an ,eastern compound4 ,illustration3 ,fig4 #dcc4--;,crushing mill4 ,allied to the volatile oils are the ,,resins1 which are non-conductors of electricity4 ,they are vegetable products4 ,they are soluble in alcohol1 in the volatile oils1 or in ether1 and these solutions are called varnishes2 the solvent evaporates and leaves the coating4 ,turpentine1 copal1 mastic1 shellac1 caoutchouc1 and gutta-percha are all resinous bodies4 ,amber is a mineral resin1 which was by the ancients supposed to be the 8tears of birds0 dropped upon the seashore4 ,moore refers to this in his poetic 8,farewell to ,araby's ,daughter0-- 8,around thee shall glisten the loveliest amber ,that ever the sorrowing sea-bird has wept40 ,amber is not soluble either in water or alcohol2 it is1 however1 soluble in sulphuric acid4 ,it takes a good polish1 and when rubbed is very electrical4 ,it is composed of water1 an acid1 some oil1 and an inflammable gas1 which goes off when the amber is distilled4 ,the well-known camphor is got from a tree called the 8,laurus ,camphora02 it is a white1 waxy substance1 and can be obtained by oxidizing certain volatile oils4 ,it is generally produced from the ,laurus ,camphora in a 8still40 ,the behaviour of a piece of camphor in pure water is curious1 but its motions can be at once arrested by touching the water or dropping oil on the surface4 ,this phenomenon is due to the surface tension of the liquid1 which diminishes when it is in contact with the vapour of the substance4 ,,nitrogenous ,,substances4 ,there are certain albuminous compounds which we must mention here4 ,these are albumen1 fibrine1 and caseine4 ,albumen is the white of egg2 fibrine is1 when solid1 our flesh and muscular fibre1 while caseine is the substance of cheese4 ,these are very important compounds1 and the albuminous bodies are of the very highest importance as food1 for the solid portion of blood1 brain1 and flesh consist1 in a great measure1 of them4 ,albumen1 fibrine1 and caseine contain carbon1 hydrogen1 nitrogen1 and oxygen1 with sulphur and phosphorus4 ,,albumen4 ,the most familiar and the almost pure form of albumen is in the white of eggs1 which is albuminate of sodium4 ,it also exists in the serum of the blood1 and therefore it is largely found in the animal kingdom4 ,it can also be extracted from seed or other vegetable substances1 but it is essentially the same4 ,albumen is very useful as an antidote to metallic poisons4 ,it forms about #g per cent4 of human blood4 ,it is soluble up to about #adj ,fah42 it then solidifies1 and is precipitated in a white mass4 ,albumen is used in the purification of sugar1 etc4 ,,fibrine is found in a liquid condition in blood4 ,the vegetable fibrine 7gluten7 is prepared by kneading wheat flour in a bag till the washings are no longer whitened4 ,like albumen it is found both in a solid and liquid state4 ,caseine is seen in the skin which forms upon milk when heated1 and forms about #c per cent4 of milk1 where it exists in a soluble state1 owing to the presence of alkali2 but caseine1 like albumen1 is only soluble in alkaline solutions4 ,as we have said1 it is the principal constituent of cheeses4 ,caseine is precipitated by the lactic acid of milk1 which is produced by keeping the milk too warm4 ,caseine1 or curds1 as they are called1 are thus precipitated4 ,the milk is said to be 8sour10 or turned4 ,,milk1 the food of the young of all mammalia1 is composed chiefly of water1 a peculiar kind of sugar1 butter1 and caseine4 ,it is this sugar in milk which causes the lactic acid mentioned above4 ,the actual constituents of milk are as follows3-- ,water #hgcjj ,butter #cjjj ,sugar #dcij ,caseine #dhbj ,calcium 7phosphate7 #bca ,magnesia #jdb ,iron #jjg ,potassium 7chloride7 #add ,sodium #jbd ,soda 7with caseine7 #jdb ------- #ajjjjj ,the sugar of milk is non-fermenting1 and can be procured from whey by evaporation4 ,,decomposition4 ,we have seen that animals and plants are composed of many different substances1 and so it will be at once understood that these substances can be separated from each other1 and then the decomposition of the body will be completed4 ,when the sap sinks or dries up in plants they are dead4 ,when our heart ceases to beat and our blood to flow we die1 and then1 gradually but surely1 decay sets in4 ,there is no fuel left to keep the body warm2 cold results1 and the action of oxygen of the air and light or water decays the body1 according to the great and unalterable laws of ,nature4 8,dust thou art1 and unto dust shalt thou return10 is an awful truth4 ,the constituents of our bodies must be resolved again1 and the unfailing law of chemical attraction is carried out1 whereby the beautiful organism1 deprived of the animating principle1 seeks to render itself into less complicated groups and their primary elements4 ,this resolution of the organic bodies is decomposition1 or 8spontaneous decomposition10 and is called decay1 fermentation1 or putrefaction1 according to circumstances4 ,the ,egyptians1 by first drying the bodies of the dead 7and then embalming them71 removed one great source of decay--viz41 water1 and afterwards1 by the addition of spices1 managed to arrest putrefaction4 ,fermentation is familiar in its results1 which may be distilled for spirituous liquors1 or merely remain fermented1 as beer and wine4 ,fusel oil is prepared from potatoes1 rum from cane sugar1 arrack from rice4 ,the power of fermentation exists in nature everywhere1 and putrefaction is considered to be owing to the presence of minute germs in the atmosphere1 upon which ,professors ,tyndall and ,huxley have discoursed eloquently4 ,plants are subjected to a process of decomposition1 which has been termed 8slow carbonization10 under certain circumstances which exclude the air4 ,the gases are given off1 and the carbon remains and increases4 ,thus we have a kind of moss becoming peat1 brown coal1 and coal4 ,the immense period during which some beds of coal must have lain in the ground can only be approximately ascertained1 but the remains found in the coal-measures have guided geologists in their calculations4 ,having already mentioned some products of distillation1 we may now close this portion of the subject and pass on to a brief consideration of minerals and crystals4 ,we have left many things unnoticed1 which in the limited space at our disposal we could not conveniently include in our sketch of chemistry and chemical phenomena4 ,,footnotes3 #bb ,cyanogen1 ethyl1 and cacodyl1 are compound radicals4 ,,chapter ,,xxxi4 ,,mineralogy ,,and ,,crystallography4 ,,the ,,minerals--,,characteristics--,,crystal s ,,and ,,their ,,forms--,,descriptions ,,of ,,minerals4 ,,minerals are constituent parts of the earth4 ,all parts of minerals are alike4 ,there are simple minerals and mixed4 ,the former are the true minerals1 and are generally considered under the heading ,,mineralogy4 ,the others constitute a branch of ,,geology1 as they form aggregate masses1 and as such compose a large portion of the earth4 ,we must learn to distinguish minerals and crystals as inorganic forms of nature4 ,in the animal and vegetable kingdoms we have forms which are possessed of organs of sight1 smell1 taste1 and certain structures indispensable to their existence and development4 ,but in minerals we have no such attributes4 ,they are ,,inorganic1 and have a similar structure2 a fragment will tell us the story as well as a block of the same mineral4 ,these inorganic substances are possessed of certain attributes or characteristics4 ,we find they have ,,form4 ,they have chemical properties1 and they behave differently when exposed to light and electricity4 ,they are generally solid4 ,all the elements are found in the mineral kingdom1 and a mineral may be an element itself1 or a chemical combination of elements4 ,these compounds are classed according as the combination is more or less simple4 ,an alliance of two elements is termed a binary compound1 of three a ternary compound1 forming a base and an acid4 ,we have learnt from our chemistry paper that there are between sixty and seventy elementary bodies in nature4 ,when we speak of 8elements10 we do not mean to apply the popular and erroneous definition of the word4 ,earth1 air1 fire1 and water are not elements2 they are compounds1 as we have seen4 ,the list of elements has been given2 we will now give the names of the more important minerals4 ,we have no space for a detailed description1 but in the ,british ,museum the cases contain some hundreds1 and the student will find them classified and described with the greatest care1 and according to the arrangement of ,berzelius4 ,,principal ,,minerals ,,as ,,arranged ,,by ,,professor ,,ansted4 ,i4 ,diamond4 ,graphite4 ,anthracite4 ,coal4 ,lignite4 ,bitumen4 ,amber4 ,sulphur4 ,quartz4 ,amethyst4 ,agate4 ,chalcedony4 ,flint4 ,jasper4 ,opal4 ,,ii4 ,sal-ammoniac4 ,nitre4 ,rock-salt4 ,borax4 ,,iii4 ,witherite4 ,spar4 ,strontianite4 ,celestine4 ,calc-spar4 ,marble4 ,dolomite4 ,fluor-spar4 ,gypsum4 ,apatite4 ,magnesite4 ,corundum4 ,sapphire4 ,emery4 ,turquoise4 ,alum-stone4 ,,iv4 ,cyanite4 ,christolite4 ,clay4 ,fullers-earth4 ,garnet4 ,iolite4 ,jade4 ,emerald4 ,beryl4 ,felspar4 ,obsidian4 ,pumice4 ,talc4 ,serpentine4 ,zircon4 ,hornblende4 ,asbestos4 ,augite4 ,diallage4 ,topaz4 ,tourmaline4 ,lapis-lazuli4 ,chrysoberyl4 ,v4 ,wolfram4 ,molybdenite4 ,chromite4 ,pitch-blende4 ,uranite4 ,pyrolusite4 ,wad4 ,manganese-spar4 ,arsenic4 ,realgar4 ,orpiment4 ,antimony 7grey74 ,bismuth4 ,blende4 ,calamine4 ,spartalite4 ,tinstone4 ,galena4 ,pyromorphite4 ,iron-pyrites4 ,mispickel4 ,magnetic iron ore4 ,micaceous iron4 ,hematite4 ,spathic iron4 ,cobalt4 ,copper4 ,oxides of copper4 ,copper pyrites4 ,azurite4 ,malachite4 ,mercury4 ,cinnabar4 ,silver4 ,gold4 ,platinum4 ,palladium4 ,the above is the arrangement best suited for beginners4 ,professor ,nichol prefers the following arrangement3-- ,,order ,i4--,,the ,,oxidised ,,stones4 ,quartz4 ,felspar4 ,scapolite4 ,haloid stones4 ,leucite4 ,zeolite4 ,mica4 ,serpentine4 ,hornblende4 ,clays4 ,garnet4 ,cyanite4 ,gems4 ,metallic stones4 ,,order ,,ii4--,,saline ,,stones4 ,calc-spar4 ,fluor-spar4 ,heavy-spar4 ,gypsum4 ,rock-salt4 ,,order ,,iii4--,,saline ,,ores4 ,sparry iron ores4 ,iron salts4 ,copper salts4 ,lead salts4 ,,order ,,iv4--,,oxidized ,,ores4 ,iron ores4 ,tinstone4 ,manganese ores4 ,red copper ores4 ,white antimony ores4 ,,order ,v4--,,the ,,native ,,metals4 ,,order ,,vi4--,,sulphuretted ,,metals4 ,iron pyrites4 ,galena4 ,grey antimony ore4 ,grey copper ore4 ,blende4 ,ruby-blende4 ,,inflammables4 ,sulphur4 ,diamond4 ,coal4 ,mineral resins4 ,combustible salts4 ,these are only a portion of the minerals1 but it would be scarcely interesting to give the list at greater length4 ,in the foregoing we recognize the metals and various combustible and non-combustible substances familiar to us1 existing1 as people say sometimes1 in 8lumps40 ,but if any one will take the trouble to examine a 8lump10 he will find the shape is definite and even4 ,these regular forms of the minerals are called ,,crystals1 from the ,greek word krustallos1 ice4 ,the term was originally applied to quartz1 for in olden times it was thought that quartz was really congealed water4 ,we can define a crystal as 8an inorganic solid bounded by plane surfaces arranged round imaginary lines known as axes40 ,it must not be imagined that crystals are small bodies2 they may be of any size4 ,there are crystals of many hundredweight2 and although the usual crystal is comparatively small1 it may be any size4 ,crystallization has occurred by cooling1 or by other natural means2 and we can form crystals by evaporation from certain salts deposited in water4 ,so we may conclude also that the evaporation of water in the early periods deposited many forms of crystals4 ,we have crystals in the air1 such as snowflakes1 which are vapours crystallized4 ,carbon1 when crystallized1 is the diamond4 ,boron is very like it4 ,oxygen cannot be crystallized4 ,alumina makes sapphires and ruby with silica4 ,alumina and earth give us spars1 tourmaline1 and garnets4 ,limestone also has beautiful forms1 as in ,iceland spar4 ,crystals1 therefore1 are certain forms of nature1 corresponding in the inorganic kingdom to the animals and plants of the organic4 ,let us look a little more at these4 ,here we have a group of crystals of different forms4 ,earths are metals combined with oxygen1 and the principal earths are alumina1 lime1 and silica4 ,to these three we are chiefly indebted for the ground we live on1 and from which we dig so many useful metals and other minerals4 ,earths are coloured by the substances mixed with them4 ,we can thus find copper1 silver1 gold1 lead1 etc41 by noting the appearance of the soil4 ,true earths are white4 ,strontia and baryta are also earths1 and the latter is used in firework manufactories4 ,our chief assistants are ,,alumina1 which furnishes us with bricks and slate2 ,,lime1 which gives us marble or stones for building in a carbonate form4 ,quicklime1 by which is meant lime freed from the carbonic acid1 is well known2 and plaster of ,paris is only lime and sulphuric acid in combination4 ,the ,,silicates1 such as sand and flint1 are in daily demand4 ,agate1 cornelian1 ,scotch pebbles1 rock-crystal1 etc41 belong to the same family4 ,even our gems are crystallized earths1 and1 as already stated1 diamonds are merely carbon4 ,stone1 as we know1 is quarried2 that is1 it is dug out of the earth4 ,but perhaps many readers do not know why a stone-mine is called a 8quarry40 ,most kinds of stone 7granite and marble are the exceptions7 are found in layers1 or strata1 rendering them easy of removal4 ,the blocks of stone are cut with reference to these layers in a more or less square manner1 and 8squared up0 before they are carried away4 ,thus the term 8quarry10 from an old ,french word1 quarr1 or carr1 as now written1 signifying a square4 ,in granite quarries the stone being very hard is bored1 and loosened by means of gunpowder or dynamite blasting4 ,slate1 on the contrary1 is easily divided into slabs4 ,we will now resume the subject of ,crystals4 ,illustration3 #a4--;,emerald4 #c4--;,garnet4 #e4--;,diamond4 ,fig4 #dcd4 #b4--;,agate4 #d4--,ruby4 #f4--,rock crystal4 ,we have said that crystals vary in size1 and this variety may be traced1 in the cases of crystallization from fluids1 to the slowness or the rapidity of the cooling process4 ,if the work be done slowly1 then the crystals obtain a size commensurate with the time of cooling1 as they are deposited one upon the other4 ,the form of minerals is the first important point1 and to ascertain their forms and structure we must study ,,crystallography4 ,we shall find faces1 or planes1--the lines of contact of any two planes1--called edges1 and the angles formed where these planes meet4 ,we may add that crystals have1 at least1 four planes1 making six edges and four angles4 ,nearly all crystals have more than this1 for the forms are1 if not infinite1 very numerous1 and are divided into six 7by some writers into seven7 different systems or fundamental forms from which the varieties are derived4 ,the axis of a crystal is an imaginary line drawn from an angle to the opposite one4 ,the first form1 the monometric1 or cubic system1 with three equal axes at right angles1 is represented by fig4 #dcf4 ,this crystal is limited by eight equilateral triangles4 ,it has twelve edges and six angles4 ,if we describe a line from any one angle to an opposite one1 that line is called an axis1 and in the case before us there are three such axes1 which intersect each other at right angles4#bc ,such crystals are regular octohedra4 ,there are irregular forms also1 whose axes do not come at right angles1 or they may be of unequal length4 ,the substances which we find crystallized in this form or system are the diamond1 nearly all metals1 chloride of sodium 7salt71 fluor-spar1 alum1 etc4 ,illustration3 ,fig4 #dce4--,stone quarry4 ,when we say in this form we do not mean that all the minerals are shaped like the illustration 7fig4 #dcf74 ,we shall at once see that the system admits of other shapes4 ,for instance1 a regular crystal may have been cut or rubbed 7and the experiment can be made with a raw turnip74 ,suppose we cut off the angles in fig4 #dcf2 we then shall have a totally different appearance1 and yet the crystal is the same1 and by cutting that down we can obtain a cube 7fig4 #dcg74 ,take off its angles again we obtain a regular octohedron once more1 as shown in the diagram opposite4 ,illustration3 ,fig4 #dcf4--,regular octahedron--first system4 ,we will exhibit the gradations4 ,suppose we cut fig4 #dcg2 we will obtain 7fig4 #dch7 the cube4 ,the next is merely the cube with angles and edges cut off2 and if we proceed regularly we shall arrive at fig4 #ddb1 the rhombic dodecahedron1 or twelve-sided figure1 whose equal planes are rhombs4 ,we can1 by taking away alternate angles or edges situated opposite1 arrive at other secondary crystals4 ,from the original octohedron we can thus obtain figs4 #ddc and #ddd4 ,these are known as tetrahedron4 ,the pentagonal dodecahedron is another secondary form 7fig4 #dde74 ,illustration3 ,fig4 #dcg4--,octohedron angles removed4 ,illustration3 ,fig4 #dch4--,the cube4 ,illustration3 ,fig4 #dci4--;,cube with angles removed4 ,the cube1 or hexahedron1 the octohedron1 and the rhombohedron are all simple forms1 being each bounded by equal and similar faces1 or surfaces4 ,we can thus understand how certain primary or original natural forms of crystals can be changed in appearance by connection4 ,of the various substances crystallizing in this system we find salt1 iron pyrites1 gold1 silver1 copper1 and platinum1 and the sulphide of lead called galena1 in the cube or hexahedron form4 ,the diamond and fluor-spar1 alum1 etc41 appear in the first form 7,i71 fig4 #dcf 7octohedron74 ,the cube1 we see1 has six equal faces1 eight equal angles1 and twelve equal edges4 ,galena1 as will be observed from the illustration herewith1 shows this peculiarity in a very marked manner 7fig4 #ddf74 ,illustration3 ,fig4 #ddj4--;,another intermediate form of octohedron between figs4 #dcf and #dch4 ,illustration3 ,fig4 #dda4--;,cube deprived of edges and angles4 ,illustration3 ,fig4 #ddb4--,rhombic dodecahedron 7garnet crystal74 ,illustration3 ,figs4 #ddc and #ddd4--,secondary forms of first system4 ,illustration3 ,fig4 #dde4--,pentagonal dodecahedron4 ,the second crystalline form is the ,,hexagonal1 and in this system three of the four axes are equal and in the same plane1 inclined at an angle of #fj1 with a principal axis at right angles to the others4 ,in crystals of this system are found quartz and calc-spar4 ,the third system is termed the ,,quadratic or the diametric4 ,this form has three axes1 all at right angles1 two being equal and the other longer or shorter than the former two4 ,in this system crystallize sulphate of nickel1 zircon1 oxide of tin1 etc4 ,illustration3 ,fig4 #ddf4--;,galena1 or sulphide of lead4 ,illustration3 ,fig4 #ddg4--,oxide of tin4 ,the fourth1 or ,,rhombic system1 or the trimetric4 ,here we have three rectangular axes1 all unequal and intersecting at right angles4 ,the sulphate and nitrate of potassium crystallize in this system4 ,illustration3 ,fig4 #ddh4--,rock crystal--second system4 ,illustration3 ,figs4 #ddi and #dej4--,quadratic1 or third system4 ,illustration3 ,fig4 #dea4--,prism of quadratic system4 ,the fifth is the oblique1 or ,,monoclinic system1 which displays three unequal axes1 two of which are at right angles2 the third1 or principal axis1 is at right angles to one and oblique to the other of the preceding4 ,ferrous sulphate1 tartaric acid1 and gypsum crystallize in this system4 ,illustration3 ,fig4 #deb4--,rhombic1 or fifth system of crystals4 ,illustration3 ,fig4 #dec4--;,crystals of the fifth system4 ,the sixth1 or ,,triclinic system1 or the doubly oblique4 ,in this system we have three axes differing in length1 and all forms which can be arranged about these unequal and oblique axes4 ,sulphate of copper will be found in this group4 ,the system has been called anorthic1 or triclinic1 because the axes are unequal and inclined1 as in the oblique prism based upon an obliqued angled parallelogram4 ,axinite crystal1 as annexed1 will show one form in this system4 ,illustration3 ,fig4 #ded4--,sixth system4 ,as may be gathered from the foregoing1 it is not easy to determine a crystalline form with certainty1--a great part of the crystal may be invisible4 ,a crystalline mass is a mineral1 which consists of an arrangement of crystals heaped together4 ,if it does not possess these the mineral is amorphous1 or shapeless4 ,we will now endeavour to describe some of the physical characteristics of minerals4 ,illustration3 ,fig4 #dee4--,wollaston's ,goniometer1 an instrument for measuring the angles of crystals4 ,the ,,goniometer 7see fig4 #dee7 is the instrument used for measuring the angles of crystals4 ,wollaston's reflecting instrument is most generally used4 ,it consists of a divided circle1 graduated to degrees1 and subdivided with the vernier4 ,the manner of working is easy1 though apparently complicated4 ,the vernier is brought to zero1 when an object is reflected in one face of the crystal4 ,the crystal is turned till the same object is viewed from another face4 ,the angle of reflection is then measured1 and can be read off on the circle4 ,we have already referred to the physical characteristics of the minerals1 and one of these attributes is cohesion4 ,when we find a substance is difficult to break1 we say it is 8hard40 ,this means that the cohesion of the different particles is very great4 ,minerals vary in hardness2 some are extremely difficult to act upon by force1 and a file appears useless4 ,at the other side we find some which can be pricked or scratched with a pin2 and these degrees of hardness being put as extremes1 we can in a manner relatively estimate the hardness of all other minerals4 ,we can test this by scratching one against another2 whichever scratches the other is the harder of the two1 and thus by taking up and discarding alternately1 we can at length arrive at a comparative estimate of the hardness of all4 ,such a scale was arrived at by ,mohs1 and arranged in the following order4 ,the softest mineral comes first3-- #a4 ,talc4 #b4 ,gypsum 7rock-salt74 #c4 ,calcareous spar4 #d4 ,fluor-spar4 #e4 ,apatite-spar4 #f4 ,felspar4 #g4 ,quartz4 #h4 ,topaz4 #i4 ,corundum4 #aj4 ,diamond4 ,talc1 we see1 is the softest1 and diamond the hardest4 ,thus 8diamond cut diamond0 has passed into a proverb expressive of the difficulties one 8sharp0 person has to circumvent or 8cut out0 another4 ,diamond is used by glass-cutters4 ,when geologists wish to express the degree of hardness of any substance1 they mention it with reference to the foregoing list2 and if the substance be harder than fluor-spar1 but not so hard as felspar1 they determine its hardness five1 or perhaps between five and six1 or between four and five1 according as it is harder or less hard than apatite4 ,thus hardness1 or power of cohesion1 resistance to exterior force and pressure1 is a prime characteristic of the mineral kingdom4 ,the file is the best test4 ,we now come to another phase of the physical character of our minerals--cleavage4 ,this is the term employed to express the facility of cutting in a certain direction which in the mineral is its direction of cleavage4 ,take mica1 for instance4 ,there is no difficulty in separating mica into thin layers2 we can do so with our fingers4 ,the layers1 or flakes1 or lamin are so arranged that they exhibit less cohesion in one direction than when tried in other ways4 ,we cut with the grain1 as it were in the direction of the fibre when wood is concerned4 ,here we have another popular saying expressive of this1--8against the grain10--which signifies an act performed unwillingly and unpleasantly4 ,cleavability1 therefore1 means cutting with the grain1 as it were1 and various minerals are possessed of different degrees of cleavage4 ,it sometimes happens that electric excitement is observed when cleavage takes place4 ,one place will become positive1 and the other negative4 ,mica1 arragonite1 and calcareous spar will exhibit this action after cleavage or pressure4 ,when a crystal of tourmaline is heated1 it will develop positive electricity at one end of its principal axis1 and negative at the other4 ,even if it be broken1 the extremities of the fragments will exhibit similar phenomena1 and so far like a magnet1 which1 as we have seen1 possesses this attribute of 8polarity40 ,but a curious fact in connection with this is that1 if the heating cease the polarity ceases for a second or two1 and yet as cooling goes on the polarity is restored1 with the difference that the positive end has become negative1 and the end previously negative has come over to the opposite pole4 ,electricity1 therefore1 must be hidden away in every portion of our globe1 and will some day be proved to be the mainspring of all life4 ,fracture in minerals is also to be noticed4 ,those substances which we cannot laminate we are obliged to break1 and we may require to break a mineral in a direction different from or opposed to its direction of cleavage4 ,under such circumstances we must break it1 disintegrate it1 and observe the fracture4 ,sometimes we shall find the surfaces very even1 or uneven1 or what is termed conchoidal4 ,this is observable in the breaking of flint4 ,there are various ways in which minerals display fracture1 and the particular manner and appearance denotes the class to which the mineral belongs4 ,we may pass over the question of the specific gravity of minerals1 as we have in a former part explained this4 ,it is important1 however1 to ascertain the specific gravity4 ,as a general rule1 minerals containing heavy metals are of high specific gravity4 ,but the relation of minerals 7crystals7 with regard to light is of great interest and importance4 ,when we were writing of polarization1 we mentioned the faculty a crystal has for double refraction1 by which it divides a ray of light into two prolonged rays taking different directions1 the plane of vibration of one being at right angles to that of the other4 ,this property is not possessed by all crystals4 ,some act as ordinary transparent media4 ,some crystals transmit only one polarized ray1 and tourmaline is called a polarizer2 and if light be passed through it to another polarizer1 it will be transmitted if the latter be similarly held2 but if the second be held at right angles to it the ray will be stopped4 ,we can easily understand this if we suppose a grating through which a strip of tin is passed2 but the strip will be stopped by bars at right angles to it4 ,the coloured rings in crystals can be observed when a slice of a double refracting crystal is examined4 ,the rings are seen surrounding a black cross in some instances1 and a white cross in another4 ,the effect when examined in the polariscope is very beautiful4 ,selenite is probably the best crystal for exhibiting colours4 ,minerals sometimes reflect1 sometimes refract light2 they are said to possess lustre and phosphorescence4 ,all these properties may be considered as belonging to the crystals which are transparent1 semi-transparent1 translucent1 or opaque1 according to the degrees in which they permit light to pass through them4 ,all minerals are electric or non-electric1 and the variety can be ascertained by rubbing and placing the mineral near the electrometer4 ,but all do not exhibit magnetic properties4 ,taste and smell are strongly marked in some minerals--salts1 for instance1 and sulphur2 some are soapy to the touch1 some appear cold to the fingers4 ,chemistry is very useful to us in determining the nature of the mineral1 and the amount of it enclosed in the substance under examination4 ,these delicate operations are termed qualitative and quantitative analysis4 ,the application of heat is increased by means of the blowpipe1 which is in effect a small bellows4 ,we can thus1 and particularly by means of the oxy-hydrogen blowpipe1 obtain a very intense heat with little trouble4 ,when the fragments of a mineral are held in the flame by platinum 8tweezers10 or tongs1 then the fusibility of the substance1 and the colour of the blow-pipe flame will be of great assistance in determining the nature of the mineral4 ,it is also curious to observe the different forms into which the various substances expand or contract under the influence of the blowpipe4 ,we may have a rugged slag1 an enamel1 or a glass1 or a bead1 or 8drop0 of metal4 ,the varied substances produce various colours--yellow1 green1 orange1 or red1 according to circumstances4 ,strontia is a vivid red1 copper is green1 lime orange1 and so on4 ,illustration3 ,fig4 #def4--,the blowpipe4 ,it is very little use to attempt a study of mineralogy without some acquaintance with chemistry4 ,in dealing with minerals1 and in studying geology1 we must try to keep our knowledge of chemical science in our minds1 and thus fortified we can more easily understand the steps leading to the classification of minerals4 ,it is impossible to teach mineralogy or geology from books4 ,nature must be studied1 the specimens must be seen1 the earth must be examined4 ,the advance in mineralogy may be--probably will be--slow1 but crystals will teach something2 and when we can pass a viva voce examination in chemistry and crystallography1 expressing1 by the symbols1 the various substances under discussion1 we shall have made a considerable advance in the science4 ,we shall have an idea of the component parts of various substances1 and be able to class the various minerals according to their chemical constitution4 ,beginning with the metalloids1 we shall pass to the metals and various compounds1 salts1 resinous substances1 etc41 such as amber4 ,it is impossible in the space at our command to describe all the minerals1 and yet it is necessary to enumerate the most important4 ,we may1 therefore1 take them in the following order4 ,it should be added that most of the simple minerals occur in comparatively small quantities1 but sometimes we find them in aggregate masses 7rocks74 ,we append a table4 ,,synoptical ,,table ,,of ,,the ,,minerals4 ,first ,class4--,metalloids4 ,sulphur4 ,boron4 ,carbon4 ,silicium 7,silicon74 ,second ,class4--,light ,metals4 ,potassium4 ,sodium4 ,ammonium4 ,calcium4 ,barium4 ,strontium4 ,magnesium4 ,aluminum4 ,heavy ,metals4 ,iron4 ,manganese4 ,cobalt4 ,copper4 ,bismuth4 ,lead4 ,tin4 ,zinc4 ,chromium4 ,antimony4 ,arsenic4 ,mercury4 ,silver4 ,gold4 ,platinum4 ,third ,class4 ,salts4 ,earthy resins4 ,,sulphur is found in ,sicily and ,italy and other parts of ,europe1 in a native state1 but as such has to be purified4 ,the crystals take the form as shown in the margin4 ,cleavage imperfect2 it is brittle4 ,sulphuric acid is a very important combination1 and a very dangerous one in inexperienced hands4 ,sulphur combines with a number of elements1 which combinations are 8,sulphides40 7,see ,chemistry section47 ,illustration3 ,fig4 #deg4--;,crystals of sulphur4 ,,selenium is a metalloid resembling sulphur1 but less common4 ,it is inodorous4 ,,boron is usually found near volcanic springs1 and in combination with oxygen4 ,it is soluble4 ,taste1 acid bitter1 and white in colour2 friable4 ,it is known as ,,sassoline1 or boracic acid4 7,see ,biborate of ,soda for one of the borates47 ,,carbon is one of the most important of our minerals4 ,in the form of coal we have it in daily use1 and in the form of diamond it is our most valuable gem4 ,in the latter form it is the hardest of all minerals1 a powerful refractor of light1 lustrous1 and transparent4 ,it is found in the ,east ,indies and ,brazil2 more lately ,cape diamonds have been brought to ,europe1 but they do not equal the ,eastern gem4 ,almost fabulous prices have been given for diamonds1 which1 after all1 are only carbon in a pure state4 ,another form of carbon is graphite 7plumbago1 or blacklead74 ,it is much used for pencils and in households4 ,it is found in ,cumberland1 and in many other localities in ,europe and ,canada4 ,carbon appears in one or other of the above forms in regular octahedrons or their allied shapes4 ,anthracite1 another form of carbon1 is used as fuel for strong furnaces4 ,it leaves little 8ash10 and is smokeless when burned4 ,coal1 in all its forms1 is evidently derived from wood4 ,thousands of years ago vegetable matter must have been embedded in the ground and subjected to carbonization4 ,there are different kinds of coal1 all of which come under one or other of the following heads3 cubical coal1 slate coal1 cannel coal1 glance-lignite1--the last being1 as its name implies1 an imperfect development of wood2 it is a brown coal4 ,we are not here concerned with coal as a fuel4 ,charcoal is also a form of carbon prepared from wood and finds a counterpart in coke1 which is prepared from coal4 ,carbon1 as we have already seen1 plays an important part in electric lighting and in the ,voltaic ,battery4 ,peat1 or as it is called in ,ireland1 8turf10 is one of the most recent of the carboniferous formations4 ,it is much used as fuel4 ,it is cut from moors 78bogs10 as they are sometimes called71 and the various deposits can be traced4 ,bog-oak is no doubt the first step towards peat1 as peat is the step towards coal4 ,the brown turf is newer than the black1 and both kinds may be seen stacked in small square 8bricks0 along the ,irish canals and in the yards of retailers of fuel4 ,illustration3 ,fig4 #deh4--;,crystals of carbon4 ,,silicon4 ,silica occurs generally in combination with alumina1 and never in a free state4 ,in combination with oxygen it is called silicic acid4 ,silica1 when crystallized1 is usually called quartz4 ,,quartz has several varieties4 ,we need only enumerate them1 they will all be immediately recognized4 ,we give illustrations of the crystals of quartz 7fig4 #dei73-- #a4 ,rock crystal appears in beautiful six-sided prisms4 #b4 ,amethyst is coloured by protoxide of manganese1 supposed by the ancients to be a charm against drunkenness4 #c4 ,common quartz1 or quartz rock1 forms granite in combination1 and is also known as 8cat's-eye10 8rose0 quartz1 etc4 #d4 ,chalcedony1 sometimes termed cornelian3 used for seals1 etc4 #e4 ,flint3 much used in potteries4 8,flint and steel0 have been superseded by phosphorus4 #f4 ,hornstone3 something like flint1 resembling horn4 #g4 ,jasper3 of various colours2 opaque and dull in appearance4 #h4 ,silicious slate3 a combination2 used as a whetstone4 #i4 ,agate3 a mixture of quartz1 amethyst1 jasper1 and cornelian2 very ornamental4 #aj4 ,opal3 a peculiar variety1 containing water4 ,it is not found in the form of crystal1 but in vitreous masses4 ,its changeableness of hue is proverbial4 ,the 8noble0 opal is much prized4 #aa4 ,smoky quartz1 or cairngorm4 #ab4 ,onyx and ,sardonyx4 ,illustration3 ,fig4 #dei4--,quartz crystals in various forms4 ,we now arrive at some minerals which contain metals4 ,,potassium4 ,this metal is so frequently combined in minerals with alumina that we may refer to it with the latter in sequel4 ,there are two natural potassa salts--nitre1 and sulphate of potassa4 ,nitre is known as saltpetre1 and is of great use in medicine4 ,it is the chief ingredient in the composition of gunpowder4 ,,sodium4 ,we have a number of minerals in this group--viz41 nitrate of soda 7nitratine71 which occurs in large quantities in ,peru2 rock salt1 chloride of sodium1 known as salt4 ,it crystallizes in the cubic system4 ,colour usually white1 but it occurs in secondary rocks in company with gypsum1 etc4 ,it is sometimes of a reddish colour1 or even green and yellow4 ,biborate of soda is borax1 and is found in and on the borders of a ,thibetian lake4 ,there are several other combinations with soda3 the sulphates of soda--viz41 thenardite and glauberite1 anhydrous and hydrated respectively1 carbonate of soda1 and so on4 ,,ammonia combinations occur in lava fissures1 and are not often met with in consequence of their volatile nature4 ,illustration3 ,fig4 #dfj4--,spar crystal4 ,,calcium4 ,this forms an important group of the minerals1 which are very white in colour1 and not very hard in substance4 ,calcium is the metallic basis of lime4 ,fluoride of calcium1 known as fluor-spar1 most frequently crystallizes in cubes in the first system4 ,anhydrite is the anhydrous sulphate of calcium4 ,the hydrated sulphate is called gypsum4 ,one variety of the hydrated sulphate is selenite1 another is known as alabaster4 ,apatite1 or asparagus stone1 and pharmacolite are in this group4 ,illustration3 ,rhombohedron 7r74 ,primary rhombohedron 7r74 ,six-sided prism 7g7 regular4 ,primitive rhombohedron 7r71 with acute form 7r74 ,obtuse rhomtrahedron 7r71 ending in prism 7g74 ,equal six-sided prism 7a71 ending in regular 7r74 ,obtuse rhombohedron4 ,fig4 #dfa4--;,,crystals ,,of ,,carbonate ,,of ,,lime4 ,carbonate of lime1 not content with one system of crystals1 makes its appearance in two4 ,it is therefore divided into two minerals--namely1 calcareous spar and arragonite4 ,in the former it possesses various forms1 as will be observed in the accompanying diagrams4 ,it is a very important mineral1 as will be readily acknowledged2 it enters largely into the composition of all shells and bones4 ,the minute shells1 deposited by millions at the bottom of the sea1 have combined to raise our chalk cliffs4 ,carbonate of lime is a constituent of water1 as the deposits at the bottoms of kettles1 upon the sides and bottoms of water-bottles1 and the stalactites all testify4 ,a little good vinegar will quickly dissolve this deposit4 ,calc-spar is crystallized1 and the ,iceland spar is celebrated4 ,marble1 which is another form of carbonate of lime1 is white1 hard1 and granular4 ,it is sometimes varied1 but the pure white is the most valuable4 ,chalk1 we know well1 is soft1 and is useful for writing4 ,we have also aphrite1 schiefer spar1--compact limestone in various forms1--and finally1 arragonite1 called from the place of its nativity1 ,arragon1--a colourless and somewhat transparent vitreous crystal4 ,,barytes4 ,the sulphate of baryta is known as heavy spar2 the crystals are of tabular forms1 but numerous modifications exist4 ,one of the forms is represented in the margin4 ,illustration3 ,fig4 #dfb4--,tabular form of heavy spar4 ,,strontium is the metallic basis of strontia4 ,sulphate of strontium is celestine1 the mineral which colours the blow-pipe flame a fine crimson4 ,there are certain varieties4 ,strontia salts are chemical preparations4 ,a beautiful pyrotechnic 8red fire0 is produced by mixing nitrate of strontia with sulphur1 antimony1 charcoal1 and chlorate of potassia4#bd ,there is a carbonate of strontia in the same crystalline system4 ,,magnesium4 ,with this metal we have a large group of minerals4 ,magnesite is carbonate of magnesia1 and occurs as talc-spar4 ,the magnesium limestone crystallizes as bitter spar4 ,this dolomite is like marble or common limestone1 according to colour4 ,talc is a combination of magnesia with silicic acid4 ,the hydrated carbonate is termed 8white magnesia40 ,the sulphate of magnesia is found in ,siberia1 and we have boracite1 and native magnesia called periclase4 ,the sulphate is generally present in mineral waters1 such as the ,seidlitz and ,epsom ,springs4 ,large masses have been found in the extensive caverns of ,kentucky and ,tennessee1 etc4 ,meerschaum is a hydrated silicate of magnesia4 ,it is found in ,anatolia and ,negropont1 also in ,france and ,australasia4 ,serpentine is another similar composition4 ,it is found in ,cornwall1 where it is carved into various ornaments4 ,it is sometimes called snakestone4 ,there are many other hydrated silicates of magnesia--viz41 gymnite1 picrosmine1 pycrophyll1 etc4 ,illustration3 ,fig4 #dfc4--;,crystal of augite4 ,there is another family allied to magnesia1 called ,,augites4 ,these minerals are black or dark-green1 and are contained in lava and basalt3 ,,augite and ,,hornblende are the chief representatives of this family4 ,the former crystallizes in the fourth system 7see fig4 #dfc71 and there are several varieties--diallage1 bronzite1 diopside1 etc4 ,,hornblende belongs to the same system1 and is a large factor in the composition of gneiss1 syenite1 and porphyry4 ,tremolite is a hornblende1 and asbestos 7amianthos71 and mountain-cork are also varieties4 ,the attribute of asbestos for sustaining heat is well known1 and may be usefully employed for fire-proof purposes4 ,the well-known jade-stone of ,china and calamite are other varieties4 ,illustration3 ,fig4 #dfd4--;,alum crystals4 ,,aluminum1 or ,,aluminium1 gives us a large class of minerals4 ,it is the metallic basis of alumina1 which1 combined with silica1 is the chief component of our clay4 ,silicic acid and this base combine to form many minerals1 and contains nearly all the precious stones4 ,corundums consist of pure alumina1 and crystallize in the hexagonal system4 ,the following stones are varieties of this mineral3--,sapphire1 a beautiful blue2 ruby1 a red oriental2 topaz1 yellow oriental2 amethyst1 violet2 all being sapphires more or less4 ,the finest crystals are found in the ,east ,indies in the sands of rivers and diluvial soils4 ,the common corundum is very hard1 and is used for polishing4 ,emery is well known1 and is found in mica-slate4 ,it is of a bluish-grey colour1 and is also a polisher4 ,,alum forms another family1 of which we may first mention aluminite1 a 8basic sulphate0 of alumina and found in small quantities4 ,alum-stone is found in ,italy4 ,alum occurs in large crystallized masses4 7,see illustration1 fig4 #dfd47 ,there are different minerals with a composition very similar to alum1 in which the potassa base of alum is supplied by others4 ,thus we have the potassa alum1 soda alum1 manganese alum1 ammonia alum--all being very nearly of the same constituents1 and having similar crystals in the regular system1 and are thus termed isomorphous1 or similarly-formed4 ,the potassa1 or potash alum1 is the commonest form1 and is found abundantly in ,england1 on the ,continent of ,europe1 and the ,united ,states4 ,soda alum is called salfatarite1 and magnesia alum pickeringite2 manganese alum is apjohnite2 phosphate of alumina is wavellite4 ,there are compounds of alumina and magnesia called ,,spinels4 ,they are hard minerals1 and the same isomorphous changes take place with them as are observable with the bases of alum4 ,there are therefore varieties such as the spinel ruby found in the ,east ,indies1 very red in colour2 the balas ruby not so red1 and the orange-red1 termed rubicelle4 ,ceylon is remarkable for some fine specimens of spinels4 ,chromite is like the spinel1 but is known as chrome iron4 ,,zeolites are principally compositions of silica and alumina4 ,they contain water1 and are white1 vitreous1 and transparent4 ,there are several varieties of them--natrolite1 stilbite1 etc4 ,we will now pass on to the ,clays1 which are a very important family of the aluminum group4 ,there are a number of hard minerals which1 when disintegrated1 form certain earthy masses4 ,these we term clay1 or clays1 which possess various colours and receive certain names1 according to the proportion of metallic oxides they contain4 ,all clays have an affinity for water1 and retain it to a very great extent4 ,the earth has also a peculiar smell4 ,clay is used in various ways2 pottery1 for instance1 we read in the ,bible as having been an employment from very ancient times4 ,one attribute of clays1 the retention of water1 is of the greatest use to the world in providing moisture for plants and seeds4 ,we may mention other characteristics of clay4 ,it absorbs oil very quickly1 and therefore is useful for removing grease-spots4 ,it cannot be burned1 so we have fire-bricks and fire-clay in our stoves and furnaces4 ,there are various clays--pipe-clay1 for instance1 which is white2 potters' clay is coarser4 ,there is porcelain clay as well as porcelain earth1 of which more below4 ,yellow ochre and sienna are clays used by artists4 ,bole is a reddish clay2 and tripoli is employed for polishing4 ,there are1 besides1 andalusite1 or chiastolite and disthene1 crystalline forms of clay4 99 99 99 99 99 ,porcelain has been known to the ,chinese for centuries4 ,in #agja it was discovered in ,germany by ,bttcher1 a chemist1 who while endeavouring to make gold by ,royal command1 found the porcelain1 and was thereby enriched4 ,porcelain earth is frequently found2 is known in many places as kaolin1 and usually comes from the decomposition of felspar4 ,but in ,cornwall we find it as decomposed granite1 and the filtering process can be viewed from the railway1 while both gneiss and granulite have been known to yield kaolin4 ,it is also found in ,china1 ,saxony1 and ,france4 ,it is free from iron1 and when ground and mixed with silicic acid1 it is handed to the potter or moulder4 ,after the vessels have been dried in the air they are put into the kiln1 and then become white and hard4 ,after that they are glazed in a mixture of porcelain earth and gypsum1 or ground flints and oxide of lead1 made fluid with water in the glazing of earthenware4 ,the vessel is then put into the furnace again1 or 8fired10 as the process is called1 and then comes out white1 hard1 and partly transparent4 ,illustration3 ,fig4 #dfe4--,porcelain furnace4 ,earthenware utensils are made of a coarser material1--clay and powdered flints1--from which all the gross matter has been eliminated4 ,flint is not difficult to break1 if made hot and thrown into cold water4 ,a stamper is then used to break the flints4 ,they are first ground in a mill and purified like the clay1 then they are mixed and beaten1 while moist1 into 8putty10 and turned1 or forced1 into moulds4 ,the handles are fixed on afterwards4 ,the ware is baked for two days and glazed4 ,the various colours are obtained by mixing different clays and oxides--iron or manganese4 ,biscuit porcelain is made by pouring a creamy mixture of porcelain earth into plaster-of-,paris moulds1 and when a thin case has formed within1 the liquid is poured out again4 ,it is then dried in the mould and shrinks4 ,the mould is taken to pieces1 and the thin biscuit porcelain is left4 ,illustration3 ,fig4 #dff4--,stampers4 ,illustration3 ,fig4 #dfg4--;,flint mill4 ,,felspars are very like the zeolites1 except that the former contain no water4 ,felspar crystallizes in a number of different forms4 ,we annex illustrations of specimens4 ,this spar is found in rocks1 granite1 gneiss1 etc4 ,one variety is the moonstone1 of a peculiar lustre4 ,felsite is amorphous felspar4 ,albite contains soda instead of potash4 ,labradorite is nearly a pure lime felspar1 and is remarkable for its colours1 like a pigeon's breast4 ,spodumene is like albite1 and leucite1 soda-lite1 etc41 belong to this family4 ,illustration3 ,fig4 #dfh4--;,felspar4 ,illustration3 ,fig4 #dfi4--;,felspar crystal4 ,,lapis-,,lazuli is a felspar distinguished by its blue tint4 ,it was used for ultramarine colouring at one time1 which colour can also be made chemically4 ,lapis-lazuli is found in ,siberia and ,china4 ,it is a mixture of mineral species4 ,hauyne is something like it4 ,obsidian is a sort of black glass1 and occurs in various colours in vitreous masses4 ,it is derived from the fusion of rocks1 and is employed in the manufacture of boxes1 etc4 ,pumice stone bears a resemblance in composition to the foregoing1 but is porous1 and so called spongy4 ,it contains both potash and soda in some quantities4 ,pearlstone and pitchstone also attach themselves to this family group4 ,the ,,garnets possess many curious forms of crystals1 which are coloured and used as gems4 ,tourmaline is a very particularly useful crystal1 and is used in the investigations concerning the polarization of light4 ,it is found of nearly all colours4 ,the garnet and staurolite crystals are shown 7figs4 #dgj1 #dga74 ,the former is silicate of alumina with the silicate of some other oxide1 which is not always the same4 ,this change1 of course1 gives us a series1 as in the case of alum above mentioned4 ,illustration3 ,fig4 #dgj4--;,garnet crystal4 ,the red varieties1 called almandine1 or precious garnets1 are distinguished from the duller1 8common0 species by their clear colour4 ,bohemia is the most productive soil for the garnets4 ,,mica includes1 as we have already noticed1 a group of minerals which have a peculiarly laminated structure4 ,these layers are by no means all alike1 but they present a smoothness to the fingers which is highly characteristic4 ,the chief constituents are alumina and silica1 occasionally with magnesia4 ,mica slate is very common1 and is often used instead of glass in window-frames4 ,muscovite1 lepidolite1 and phlogopite are all micas of the 8potash10 8lithia10 and 8magnesia0 varieties4 ,in the list of minerals associated with the lighter metals1 we need only now mention the ,gems1 so well known4 ,these stones are very hard in many instances1 infusible1 and exhibiting beautiful colours4 ,amongst them are diamonds1 sapphires1 and rubies1 of which we have spoken2 the topaz1 noticed under corundum4 ,the chrysoberyl 7of a pale green1 or occasionally reddish hue71 of which the alexandrite of ,siberia is a variety1 is a compound of glucina with alumina2 the beryl1 a silicate of the same1 and the emerald of beautiful green4 ,zircon is another gem1 and 8hyacinth0 is its most valued form4 ,the latter is found in basaltic rocks4 ,the emerald crystallizes in the hexagonal system4 ,illustration3 ,fig4 #dga4--,staurolite crystal4 ,we may now consider the minerals formed by the heavier metals1 such as ,iron1 ,copper1 ,nickel1 etc4 ,,iron4 ,this well-known metal fills a very important place in our mineral arrangements1 for the substances formed with iron ores occur in great variety of structure1 and occasionally in very large masses4 ,they are highly magnetic1 and very hard4 ,were we here treating of iron as a metal1 we could give some information respecting its extraction and manifold uses4 ,all we need mention here is the fact that iron occurs in nature in various ores which are essentially composed of iron and oxygen4 ,the iron is extracted in the blast furnace1 in which the process is continued for years4 ,the 8slag10 or glassy scum1 protects the molten iron from the air2 its presence is necessary in all blast furnaces4 ,the most important of the iron group of minerals are ,,magnetic ,,iron 7magnetite71 or loadstone4 ,this mineral occurs in ,sweden and ,north ,america1 and is found in primary rocks1 and in ,scandinavia forms mountains4 ,it crystallizes in the regular 7octahedron7 system1 and often in the form in illustration in the margin4 ,it is highly magnetic1 as its name implies4 ,illustration3 ,fig4 #dgb4--,magnetic iron4 ,native iron very rarely occurs1 and then only in thin layers4 ,the most extraordinary specimens are those termed meteoric iron1 which fall from the atmosphere in great masses2 and the meteoric stones1 which contain ninety per cent of iron1 together with other constituents in small quantities--viz41 nickel1 cobalt1 copper1 manganese1 carbon1 sulphur1 arsenic1 etc4 ,red hematite crystallizes in the hexagonal system4 ,it possesses much the same 7chemical7 constitution as corundum 7q4 v474 ,it is brightly metallic1 and shows a red streak4 ,it occurs in various forms1 as iron glance or specular iron1 which is found in ,sweden and ,russia2 micaceous iron1 bloodstone1 clay1 ironstone1 etc4 ,brown hematite has not been found in crystals1 but brown ironstone 7fibrous7 is crystalline4 ,the earthy brown1 containing clay1 gives us yellow ochre and umber4 ,pea-iron ore and 8morass0 or 8bog0 ore also belong to this class4 ,limonite is the name given to these more recent formations1 of which yellow ochre is a pure specimen4 ,illustration3 ,fig4 #dgc4--,native oxide of iron4 ,the combinations of iron with sulphur 7pyrites7 are also important4 ,iron pyrites and magnetic iron pyrites are two which may be mentioned4 ,the latter first4 ,magnetic iron pyrites 7or pyrrhotin7 crystallizes in six-sided prisms1 and is attracted by the magnet4 ,the composition of this mineral has not been exactly ascertained1 and no chemical formula has been found for it4 ,,iron ,,pyrites 7bisulphide of iron7 is known as cubic pyrites1 yellow pyrites1 and mundic4 ,it is generally found in the regular system of crystals1 either as a cube or as a pentagonal dodecahedron4 7,see first system of crystals1 ante47 ,its colour is yellowish4 ,it is known also as green vitriol when oxidised1 and forms beautiful green crystals 7copperas74 ,this salt is used in the preparation of ,prussian blue and violet dyes4 ,with gallic acid it makes ink4 ,there are many other 8ferruginous0 minerals1 such as vivianite1 green ironstone1 white iron pyrites1 arsenical pyrites1 or mispickel1 etc4 ,a carbonate of iron1 called chalybite1 or spathic ironstone1 is very abundant in nature1 and forms obtuse rhombohedrons4 ,it is very useful for the production of steel1 as it forms the clay iron ore found in coal districts in combination4 ,in a fibrous form it is known as sphrosiderite4 ,it is a most useful mineral4 ,chrome iron 7chromite7 is useful for the preparation of chromium compounds4 ,it crystallizes in the cubic system4 ,it is magnetic1 especially when treated4 ,chromic acid forms scarlet 8needle0 crystals1 and by its assistance chromate of lead1 or chrome yellow1 is prepared4 7,chromate of lead is found in a native state as crocoisite74 ,see ,chromium4 ,,manganese is contained in several minerals4 ,it usually occurs as an oxide4 ,it colours minerals variously4 ,in a pure state manganese is white and brittle4 ,the chief minerals are-- ,pyrolusite 7the binoxide of manganese of commerce7 occurs in crystals4 ,it is black4 ,it is used in the preparation of chlorine and oxygen4 ,the other minerals are known as manganite1 which is also found associated with pyrolusite1 as are hausmannite and braunite1 the other oxides4 ,,nickel and ,,cobalt are generally found together1 both being similar1 and the minerals are compounds of arsenic or sulphur1 and occur under similar circumstances4 ,the principal are of ,,nickel and of ,,cobalt-- ,sulphide of nickel 7ullmanite74 ,arsenical nickel 7nickeline74 ,nickel glance 7gersdorffite74 ,nickel pyrites 7siegenite74 ,arsenical cobalt 7smaltine74 ,cobalt glance 7cobaltine74 ,cobalt bloom 7erythrine74 ,cobalt pyrites 7linnite74 ,nickel ores are used for extraction of the metal1 which is used as a substitute for silver4 ,the name is derived from the ,german1 kupfernickel1 or false copper4 ,it was discovered in #agea4 ,,copper1 again1 forms a number of minerals1 and the chief is the red oxide of the metal1 called cuprite4 ,it crystallizes in the cubic system4 ,its colour is red1 and tinges a flame green4 ,cuprite yields excellent copper1 and is found in ,cornwall1 and in many places on the continent4 ,the black oxide is rarely found4 ,it is known as melaconite4 ,malachite 7carbonate of copper7 is remarkable for its beautiful green colour4 ,in ,australia it is worked for copper4 ,it is chiefly ornamental4 ,siberia yields the finest specimens1 but the mineral is found in ,cornwall and ,cumberland1 as well as on the continent4 ,chessylite 7from ,chessy1 in ,france7 is frequently found with malachite4 ,it has been called blue malachite1 or the azure copper ore4 ,it is used as a paint4 ,besides the above1 copper unites with sulphur to form minerals1 such as the needle ore 7bismuthic sulphide of copper71 antimonial sulphide1 bournonite2 purple copper1 and copper pyrites1 which is very abundant1 and furnishes us with most of our copper4 ,there is also the 8grey0 copper ore1 which contains various metals2 even silver is obtained from it at times4 ,,bismuth gives us only a few minerals1 of secondary importance4 ,native bismuth resembles antimony1 but is reddish in hue4 ,bismuth ochre1 bismuth blende1 and bismuthine are the chief combinations4 ,,lead is more important1 and is obtained from galena1 the sulphide of lead1 which is very abundant1 and the principal lead ore4 ,it can be at once distinguished by its high specific gravity and metallic lustre2 the 8cubic cleavage0 also is very easy4 ,it frequently is found containing silver1 and even gold1 antimony1 iron1 etc4 ,there are several suphantimonites of lead1 such as zinkenite1 geocronite1 etc41 and the salts1 such as sulphate of lead and white lead ore1 or carbonate of lead 7cerasite74 ,the chromate of lead is found in the ,ural ,mountains4 ,,tin is not found in a native state1 but as tinstone1 or binoxide of tin1 named cassiterite4 ,it is found largely in ,cornwall1 and the mines there have yielded great quantities for generations4 ,tin pyrites1 a union of sulphides of tin1 iron1 and copper1 is also found in ,cornwall4 ,,zinc is produced from the ore called 7zinc7 blende1 or sulphide of zinc 7black ,jack74 ,its colour is very variable1 sometimes red1 but when pure is greenish-yellow4 ,it is also found black and brown4 ,the red oxide of zinc 7or spartalite7 is also worked for zinc4 ,the carbonate1 or zinc spar1 is common1 and used to make brass1 as is calamine1 which is possessed of a remarkable lustre1 and is even luminous when rubbed4 ,it is a silicious oxide of zinc1 and is found in the sedimentary rocks4 ,when heated1 it displays strong electric properties4 ,,chromium occurs in very few mineral combinations2 chromate of lead1 chrome iron1 and chrome ochre1 or sesqui-oxide of chromium are the only important ones4 ,,antimony minerals are very hard2 the tersulphide is the most common1 and from this the metallic antimony is produced4 ,red antimony1 the oxide1 is a rarer ore4 ,,arsenic resembles antimony1 and occurs in combination with many metals4 ,white arsenic1 or arsenious acid1 is found in ,bohemia1 ,alsace1 ,transylvania1 etc4 ,orpiment and realgar are sulphides of arsenic1 and are employed as colouring matters in paint and fireworks4 ,arsenic is very poisonous4 ,,mercury is occasionally found native1 but more generally as cinnabar4 ,chloride of mercury 7or calomel7 is found associated with the cinnabar1 or hepatic ore4 ,cinnabar is easily volatilized1 and possesses high specific gravity4 ,the ,californian mines are very rich4 ,spain also produces a large quantity4 ,it is opaque1 and carmine in colour4 ,,silver occurs native1 or in ores4 ,the latter are as follows3--,the sulphide1 or the vitreous silver 7argentite72 antimonial silver2 and the combined sulphides1 of antimony and silver4 ,there are many silver minerals1 such as the chloride 7horn silver1 or kerargyrite71 bromide1 and carbonate of silver1 bismuthic silver1 etc4 ,the bromide and iodide are bromargyrite and iodargyrite4 ,silver occurs most frequently associated with gold2 natural alloys of these two metals are found1 containing from #jaf to #chg per cent4 of silver1 which causes considerable variations both of colour and density4 ,in addition to this alloy1 we may mention sylvanite 7graphic tellurium71 which contains1 besides gold and silver1 one of the rarer metals--viz41 tellurium4 ,illustration3 ,fig4 #dgd4--;,gold crystals4 ,,gold is our most precious mineral1 and is generally found native4 ,it exists in sand and in certain rocks4 ,it crystallizes in various forms1 and in ,mexico it is found in companionship with silver and copper sulphides4 ,australia and ,california render the most valuable supplies of the metal4 ,,platinum is also found native1 and rarely is crystals4 ,it is often alloyed with other metals1 chiefly with iron or gold2 also with diamonds4 ,we have already considered it as a metal4 ,little remains to be said about salts and resins1 for with the exception of those we have referred to under ,chemistry1 they are of little value4 ,the bitumens1 rock oil1 etc41 which exude from the earth1 are very useful1 and as asphalt and petroleum play an important part in the civilized world1 but scarcely come under the strict rule of minerals as we consider them1 and with this reference we close our sketch of ,mineralogy4 ,,footnotes3 #bc ,a crystal should be held so that one of its axes is vertical to the spectator4 ,this axis is termed the principal axis1 and when there is inequality the longest axis is the principal4 #bd ,see 8,strontium0 in ,chemistry4 ,,chapter ,,xxxii4 ,,new ,,locomotive ,,appliances4 ,,the ,,kite--,,the ,,aerophane--,,ice ,,yachts--,,sailing ,,trucks--,,water ,,velocipedes4 ,the kite1 known from the earliest times1 and constructed by a number of people1 is a very familiar object1 which we shall not describe2 for we will now speak of some similar appliances of a more interesting and uncommon description4 ,illustration3 ,fig4 #dge4--,mr4 ,penaud's 8,high-flier40 ,m4 ,penaud has invented some appliances in which twisted india-rubber is the principal agent4 ,fig4 #dge represents a sort of kite1 which rises in the air if one twists and then looses the india-rubber round the central bow4 ,fig4 #dgf represents another kind of invention2 it is an 8aerophane10 with a screw at the back1 so fixed that it receives no shock from striking against any obstacle4 ,after having twisted the india-rubber1 and loosened our hold of the apparatus in a horizontal position1 it will first descend for an instant1 then1 acquiring increased speed1 it rises seven or eight feet from the ground1 and describes a regular movement in the air for a distance of about fifty yards2 the motion lasts for several seconds4 ,some models have also been constructed capable of traversing a distance of over seventy yards1 remaining for thirteen seconds in the air1 as lightly poised as a bird1 and without any connection with the ground4 ,during the whole time the rudder restrains with perfect exactitude the ascending and descending movements as they occur2 and we can plainly observe the various oscillations like those of sparrows1 or more especially woodpeckers4 ,at last1 when the movements are coming to an end1 the apparatus falls gently to the ground in a slanting line4 ,illustration3 ,fig #dgf4--,m4 ,penaud's 8,aerophane40 ,m4 ,penaud has also succeeded in constructing a mechanical bird1 that we have seen set in motion1 which will continue flying for several seconds2 we give an illustration of it in fig4 #dgg4 ,another scientist1 ,m4 ,tatin1 has also produced some remarkable results4 ,his efforts have been unceasingly directed towards the reproduction of the flight of a bird by means of more or less complicated arrangements4 ,he has endeavoured to discover in the small appliances made with indiarubber1 and used by ,,mm4 ,penaud and ,hureau de ,villeneuve1 what were the best shapes in which to reproduce the wings1 in order to adapt them to a large apparatus acting by compressed air4 ,after several attempts1 he decided on the employment of long1 narrow wings4 ,wenham had previously proved that a wing may be equally effectual whether it be narrow or wide1 and ,m4 ,marcy has also declared that birds with a quick1 narrow wing-stroke have always very long wings4 ,by means of these long1 narrow wings 7fig4 #dgh7 ,m4 ,tatin has reduced the time during which the wing reaches a suitable position for acting on the air when it first descends4 ,granted the fact1 so long established1 that a bird flies more easily if it rests its wing against a great volume of air1 it will be understood that the maximum speed of movement will also be the most advantageous as regards the reduction of expended force4 ,the inventor1 finding that he could not prevent his mechanical birds from losing force in proportion as they attained considerable speed1 remedied this defect by placing the centre of gravity in front4 ,in consequence of this1 the bird in full flight preserves the same equilibrium as the bird hovering in the air1 and its speed is1 to a certain extent1 passive1 the mass of air pressing of its own accord against the wings1 all expenditure of force therefore being utilized for suspension4 ,thus has ,m4 ,tatin been enabled to increase the weight of his appliances1 without increasing the motive power1 and yet obtains a double course4 ,illustration3 ,fig4 #dgg4--,mechanical bird4 ,the movement made by the wing round a longitudinal axis1 by means of which it always exposes its lower surface in front on rising1 is obtained by the mechanism illustrated in fig4 #dgh a4 ,m4 ,,tatin',s ,,bird4 ,this apparatus1 looked at sideways or from behind1 is composed of a light wooden frame1 on which are two small supports crossed by an axletree so as to form two cranks4 ,this axle receives a circular movement from an india-rubber spring4 ,the crank on the foremost plane causes the rising and falling of the wings1 which move round a common axis1 and pass the dead points as the cranks of a locomotive do--so the action is maintained4 ,illustration3 ,fig4 #dgh4--,m4 ,tatin's bird4 ,illustration3 ,fig4 #dgh a4--,detail of fig4 #dgh4 ,but the wing does not only move as a whole2 every part of it1 particularly as it rises1 shows a tendency to inclination1 which is most marked towards the extremity2 the part near the body alone preserves an invariable obliquity4 ,m4 ,tatin was of opinion that it is with the screw that it is necessary to direct the twisting movement2 and to obtain it with all its transitions1 he has substituted for silk wings1 which fold up1 some wings composed entirely of strong feathers1 arranged in such a manner that they slipped one over the other when in motion4 ,the arrangement was perfect1 but still not suitable for adaptation to the large bird4 ,the inventor therefore again returned to the use of the silk wings1 which he appears to have definitely adopted4 ,by means of certain modifications which he has recently introduced in his larger apparatus--viz41 a change in the shape of the wings1 variation of the amplitude in the flapping1 etc41 ,m4 ,tatin has been enabled to make great progress4 ,the bird1 acting by means of compressed air1 at first could only raise three-quarters of its own weight1 but finally lifted itself entirely4 ,and we must take into consideration that the apparatus has to struggle against the weight of the steering apparatus1 which nullifying the vertical and horizontal reactions of the bird during flight1 constantly fulfils the office of regulator4 ,illustration3 ,fig4 #dgi4--;,back view of apparatus4 ,we will now pass to the consideration of two ingenious appliances of a very clever inventor1 ,m4 ,salleron4 ,,small ,,atmospheric ,,boat4 ,the little boat shown in fig4 #dhj1 which is about the size of an ordinary plaything1 is a very ingenious1 if not a practical1 application of the specific lightness of air acting as a propelling force4 ,in this instance steam plays but a secondary part1 which consists in carrying off the air that causes the moving of the boat4 ,illustration3 ,fig4 #dhj4--;,atmospheric boat4 ,the apparatus1 as represented in fig4 #dha1 is of extreme simplicity1 as will be seen at a glance4 ,a small cylindrical boiler1 ,b1 connected with a capillary tube1 is placed on two supports over a spirit-lamp1 in such a manner that the opening from which the steam issues is directly opposite the mouth of the tube1 ,t4 ,this tube1 after forming a sudden inclination1 terminates at the back of the boat in an inclined drain1 ,r4 ,the steam driven through the tube1 ,t1 carries along with it a certain quantity of air1 which1 forced under the water1 propels the boat along4 ,the little vessel soon reaches considerable speed1 leaving a long track behind it4 ,it will be seen that this is not a mechanical apparatus1 capable of absorbing force or diminishing the action of steam by causing its condensation4 ,illustration3 ,fig4 #dha4--,section of 8atmospheric0 boat4 ,let us now calculate the force engendered by this apparatus4 ,we know that a litre of water at boiling point gives #a1gjj times its volume4 ,the steam1 as it quickly issues from the opening of the boiler1 carries along at least ten times its volume1 or #ag1jjj litres of air1 which1 driven under the water1 assumes an ascending force equal to the difference of the densities of water and air1 or about the weight of the displaced water4 ,therefore in a litre of water transformed into #a1gjj litres of the steam1 which carries off into the water #a1gjj #aj #ag1jjj litres of air1 a force is developed represented by #cd1jjj kilograms4 ,in fact1 by reason of the inclined position of the drain on which the pressure of air acts1 and its restricted dimensions1 the quantity of force employed in the propulsion of the boat is but a fraction of the total force produced4 ,moreover1 the resistance of traction increases with the size of the boat1 and as the dimensions of the inclined pipe cannot be indefinitely enlarged1 the result is that the propulsive action is soon insufficient1 so that the invention is not1 in its present condition1 applicable to navigation on a large scale4 ,its superiority to the steam-engine cannot1 therefore1 be demonstrated2 and we are only now discussing the contrivance in order to show that it is possible1 with only moderately powerful generators and extremely simple mechanical appliances1 to obtain considerable dynamic effects1 susceptible of more serviceable application than is commonly believed4 ,,circulating ,,fountain4 ,the apparatus given in fig4 #dhb is the subject of a very charming experiment1 showing the influence of capillarity on the movements of liquids4 ,two glass balls1 ,b ,b1 are connected by two tubes2 one straight and of rather large diameter1 the other extremely slender1 and winding in and out in a more or less complicated manner4 ,the large tube passes into ball ,b1 and forms a slender point1 ,j1 at the orifice of the narrow tube4 ,at the lower end of the ball is a bulb1 which is closed with a cork1 and contains a coloured liquid4 ,the apparatus is fixed to a board with a ring at each end1 by which it can be hung on the wall4 ,when commencing the experiment1 it should be hung so that the ball ,b is uppermost4 ,the liquid then flows through into the ball ,b1 without presenting any particular phenomenon4 ,the apparatus is then turned1 and the liquid descends again with great speed1 shoots through the opening1 ,j1 and rises into the twisted tube4 ,the air displaced from ball ,b also rises1 however1 and mingles with the liquid1 and it can be seen circulating through the winding tube in a number of air-bubbles1 mingled with drops of liquid1 gradually transmitting the pressure of the column contained in the upper ball and straight tube2 so that by means of a similar phenomenon to that of the fountain of ,nero1 the liquid rises higher than the level of the reservoir1 a part falling into ball ,b1 which causes the experiment to be a little prolonged4 ,this circulation of air-bubbles and coloured drops through the twisted tube of the apparatus has a very pretty effect4 ,illustration3 ,fig4 #dhb4--;,circulating fountain4 ,,the ,,pneumatic ,,pencil4 ,this ingenious invention is productive of results similar to ,edison's electric pen4 ,it is the invention of an ,american gentleman1 ,mr4 ,j4 ,w4 ,brickenridge1 of ,lafayette1 ,indiana4 ,the illustration 7fig4 #dhc7 explains the mechanism of the pneumatic pencil4 ,the whole apparatus is figured on the left side of the picture1 while the longitudinal section of the pencil is shown on the right1 the small cut at the top being a vertical section of a portion of the motive power4 ,compressed air furnishes the power of pressure1 which is accomplished by means of a perforating needle4 ,if the treadle is put in motion1 a backward and forward movement is imparted to a flexible diaphragm1 as in the upper section in the centre of the illustration4 ,by this movement the air is permitted to enter1 and is compressed by the diaphragm into the flexible tube with which the diaphragm is connected4 ,the air is thus brought into contact with another diaphragm at the end of the tube and presses on it4 ,the pencil is fixed to the latter4 ,when it is desired to use the pencil the apparatus is set in motion1 and by a series of sharp1 quick perforations1 any writing can be traced1 as by the electric pen4 ,this indentation can be copied over and over again in a press1 the writing acting as the negative2 and if ink be first run over it1 as in a stencil plate1 by a proper 8roller10 the latter will come out as plainly as possible4 ,illustration3 ,fig4 #dhc4--,pneumatic pencil4 ,,tube ,,wells4 ,the principle upon which the tube well depends is very simple4 ,it is well known that in certain localities water lies a short distance beneath the surface of the ground1 and a very little trouble would satisfy us upon the point1 and render us quite independent of the water companies' supply4 ,on the supposition that the water exists underneath our garden at1 say1 twenty-five feet beneath the surface of the ground1 we have only to drive into the soil a tube for that distance1 and by the assistance of a common pump we shall obtain a pure supply of water4 ,we will now proceed to describe the manner in which these wells are sunk4 ,the first step is to fix a platform firmly upon the ground and bore a hole1 by which the tube is to enter the ground4 ,this tube should be very thick1 with an aperture of two inches or rather less1 and three or four yards in length4 ,the lower portion should be pierced with holes1 as in the illustration1 and terminating in a point of extremely fine-tempered steel4 ,this tube can be driven into the ground by mallets1 or by the suspended hammer1 worked as shown in the illustration 7fig4 #dhd74 ,this work will be easily accomplished1 and when the first length of tube has been driven in1 another can be fixed to it and hammered down in the same way4 ,illustration3 ,fig4 #dhd4--,tube ,well4 ,when the tubes have been driven to the depth indicated it will be as well to let down a sounding line1 a simple cord sustaining a pebble4 ,if the stone be pulled up dry1 another length of tube can be added1 or the tubes can be pulled up1 and another trial made4 ,if1 on the contrary1 the pebble come up wet1 the object is accomplished1 and a small pump can be fixed to the upper end of the tube1 as in fig4 #dhe4 ,at first the water will be found a little thick and muddy1 in consequence of the disturbance of the soil and the particles adhering to the end of the first tube2 but after an hour or so it will be found that the water has become quite clear4 ,it need scarcely be said that if the water possesses sufficient ascensional force to rise to the level of the ground a pump need not be employed4 ,an ,artesian ,well will1 in that case1 be the result4 ,the operation described on page #def can usually be performed without any difficulty4 ,sometimes1 however1 the tube may come in contact with a large stone1 and in that case the experiment must be tried elsewhere2 but1 as a rule1 the pointed tube1 in consequence of its small size and penetrative power1 pushes any moderately-sized obstacle aside1 readily turns aside itself1 or passes between pieces of stone to the desired depth4 ,nine times out of ten the operation will be successful1 and the experiment will not occupy more than an hour1 under ordinary circumstances1 and the tubing 7and pump7 may be obtained at a moderate price1 which can even be diminished by arrangement4 ,ordinary wells are relatively very difficult to sink1 and the soil thrown out from the pit is in the way1 while a parapet is necessary to protect the opening4 ,besides1 should water not be found after much work1 the expense and trouble of digging will be uselessly incurred4 ,thanks to the tube system1 we can search or probe for water anywhere with ease1 and if we do not find it in one spot we can easily move on to another without incurring any serious trouble or expense4 ,illustration3 ,fig4 #dhe4--;,abyssinian ,pump4 ,we believe the idea of these 8instantaneous wells0 originated in the ,united ,states during the ,war of ,secession1 when some soldiers of the ,northern army sunk rifle barrels into the ground1 and obtained water in a barren land4 ,to ,mr4 ,norton the development of the idea is due1 and in the ,abyssinian ,expedition the utility of the notion was fully demonstrated4 ,since that time ,m4 ,donnet of ,lyons has modified and improved the tube-well1 and arranged all the materials1 including wider tubing and the hammers upon a carriage1 thus giving greater facilities to the workmen and to those desirous of sinking such wells4 ,the general arrangement of ,m4 ,donnet1 and the carriage with its equipments utilized1 is depicted in fig4 #dhd2 the actual sinking of the well is carried out just as originally performed by ,mr4 ,norton4 ,a ,,new ,,swimming ,,apparatus4 ,illustration3 ,fig4 #dhf4--,swimming apparatus4 ,we have to mention a novel means of swimming1 which may prove useful to those who distrust the natural buoyancy of water and their own powers of keeping afloat or swimming4 ,the simple apparatus1 shown in fig4 #dhf1 is the invention of an ,american named ,richardson1 a citizen of ,mobile1 ,u4,s4 ,illustration3 ,fig4 #dhg4--,nautical ,velocipede4 ,the machine consists1 essentially1 of a shaft1 upon which a float is fixed1 and at the end of the shaft is a small screw propeller4 ,the shaft is put in motion by a wheel arrangement worked by the hands1 and by a crank moved by the feet4 ,the swimmer rests upon the float1 with his head well above water4 ,the float sustains him1 while the propeller forces him through the water1 without his feeling fatigued1 at the rate of about five miles an hour4 ,a certain amount of practice is necessary to obtain complete command of the machine1 but when mastered the swimmer can proceed1 without much exertion1 at a rapid rate4 ,the apparatus itself is not difficult to make1 and persons who have tried it speak highly of its convenience and of the facilities it may afford4 ,captain ,boyton's swimming-dress is another useful invention1 but the means of mechanical propulsion are wanting1 while in this new apparatus the swimmer can drive himself through the sea with ease and expedition1 and even a non-swimmer may thereby save life without danger to himself1 or the person he wishes to rescue4 ,illustration3 ,fig4 #dhh4--,trained seal drawing canoe4 ,the ,,nautical ,,velocipede1 which also deserves some notice at our hands1 is the invention of ,m4 ,croce-,spinelli1 who tried it upon the great lake of ,vincennes and also on the ,seine1 when it was the object of much curiosity2 but when the ,franco-,german war broke out the experiments were discontinued1 and the inventor did not live to perfect the apparatus4 ,he fell a victim to his love for ballooning4 ,but ,m4 ,joberts1 a practical machinist1 has lately taken up the idea broached by ,croce-,spinelli1 and has brought out a new water velocipede of very ingenious construction1 with satisfactory results4 ,the machine is described as follows4 ,there are two hollow tin 8floats0 of cylindrical form1 and tapered at the ends4 ,these floats are joined together by a platform made of very light wood1 on which the seat of the worker is raised1 and underneath is the machinery for propelling the velocipede4 ,the motive power is very simple1 and corresponds to that employed to propel the bicycle on land1 by the feet of the rider1 the wheel being furnished with paddles in the water velocipede4 ,illustration3 ,fig4 #dhi4--;,double yachts4 ,a rudder1 which can easily be worked by cords1 gives the velocipedist complete control of the machine1 the steering being performed by a handle similar to that which the bicyclist uses to turn the machine he rides4 ,in fact1 the 8water0 velocipede is an adaptation of the 8terrestrial0 machine so familiar to all readers4 ,this velocipede is equally adapted for sea or lake progression1 the waves of the former being1 under ordinary circumstances1 no obstruction1 for very little motion is imparted to the sitter4 ,for those desirous to bathe in deep water the machine offers many facilities2 and in the case of attack of cramp or faintness1 rescue would not be difficult1 as the swimmer could support himself upon the pointed cylinders of the water velocipede till assistance arrived4 ,on the other hand1 it is very necessary to know how to swim before attempting to work the machine4 ,illustration3 ,fig4 #dij4--;,ice boats4 ,before describing the ice-yachts which are used in ,canada when winter's cold grasp lies on water and land1 we will mention a very curious experiment in water locomotion made a year or two ago4 ,the illustration explains itself4 ,it is not an imaginary sketch1 it is the record of fact4 ,this sagacious seal was exhibited in ,london1 and was in the habit of performing certain tricks1 one item of his performance being to draw the light canoe 7as represented71 and another accomplishment consisted in 8striking the light guitar10 to the astonishment of the spectators1 amongst whom was the writer4 ,the instrument was placed between his fins1 or 8flappers10 and the seal twanged it more or less melodiously4 ,he was very tame1 and obedient to his master and trainer4 ,we all have heard of1 even if we have not seen1 the twin steamer ,castalia1 which1 pending the opening of the tunnel beneath the ,channel1 was supposed to reduce sea-sickness to a minimum4 ,the ,castalia did not answer1 however1 but an ,american has planned certain double yachts1 of which we give an illustration4 ,the sailing-boats1 as represented1 have had much success upon the lake of ,cayuga1 and are quite seaworthy1--in fact1 it is impossible to overturn them4 ,the weight of one of these yachts is about fifteen hundred pounds1 and the draught six inches4 ,having two keels they answer the helm very readily4 ,the boat1 in the centre of the illustration1 belongs to ,mr4 ,prentiss1 and is called the ,pera ,ladronia4 ,it is a very fast 8ship40 ,from navigation in water1 we now come to navigation on water4 ,the ice-boats are much used in ,canada1 and their simple but effective construction will be readily perceived from the accompanying illustration4 ,the ,americans state that these ice-yachts can run before a good breeze as fast as an ordinary train4 ,there are1 or were1 models of some such 7,finland7 yachts in the ,south ,kensington ,museum with two sails4 ,the ,american yacht1 as a rule1 has only one sail1 and the owners say--but we will not vouch for the truth of the allegation--that they frequently run far ahead of the wind that primarily propelled them6 ,,sailing ,,on ,,land4 ,it is quite possible to sail upon land1 although this statement may appear contradictory in terms4 8,the force of the wind upon sails10 says ,bishop ,wilkins in his work1 8,mathematical ,magic10 printed in ,london in #afdh1 8can be applied to vehicles on land as well as to ships at sea4 ,such conveyances10 he adds1 8have long been in use in ,china and in ,spain1 as well as in flat countries1 such as ,holland1 where they have been employed with great success4 ,in the last-named country they are propelled with greater speed than are ships before a fair wind2 so that in a few hours a boat containing several persons actually travelled nearly two hundred miles1 with no trouble to any one on board except the steersman1 who had little difficulty in guiding the boat40 ,illustration3 ,fig4 #dia4--,sailing carriage of the #agth century1 from a drawing of the period4 ,the astonishment expressed by the good bishop was quite justified1 for1 as a matter of fact1 a carriage or boat on wheels1 with sails1 as shown in the illustration1 achieved a distance of nearly thirty-eight miles in an hour4 ,this pace was quite unknown at that time2 such a rate of travelling had never entered the minds of people then4 8,men running in front of the machine after a while appeared to be going backwards1 so quickly were they overtaken and passed40 8,objects at a distance were approached in the twinkling of an eye1 and were left far in the rear40 ,so it is evident that1 had locomotion by steam not been adopted1 the mode of sailing on land would have eventually become the most rapid mode of transit1 and it is rather remarkable that it was never adopted as a mode of travel4 ,illustration3 ,fig4 #dib4--,on the ,kansas ,pacific ,railway4 ,but ,bishop ,wilkins had not to reproach himself on this account1 for he adapted the principle of the windmill to carriages1 8so that the sails would turn and move his car1 no matter in what direction the wind was blowing40 ,he proposed to make these sails act upon the wheels of a carriage1 and trusted to 8make it move in any direction1 either with the wind or against it60 ,this suggestion has been lately adopted in the ,united ,states1 and it is curious that after two hundred and fifty years no better mode for utilizing wind-power on land has ever been found4 ,perhaps the ice-boats already mentioned may be the forerunners of some new system of 8land transport10 for which enormous kites have been made available4 ,it is somewhat remarkable that if the introduction of railroads quite 8took the wind out of the sails0 of any other mode of locomotion on terra firma1 it is that very iron track which has led to the reintroduction of sails as a mode of progression upon the rails4 ,in the ,united ,states at the present time there are many vehicles propelled by sails across the immense prairies at a pace1 with a strong wind1 which equals that of the trains4 ,we are indebted to ,mr4 ,wood1 of ,hayes ,city1 ,kansas1 for the photograph from which the picture of the sailing-waggon1 invented by ,mr4 ,bascom1 of the ,kansas ,pacific ,railway1 is copied4 ,this carriage travels usually at thirty miles an hour1 and a speed of forty miles an hour has been obtained when the wind has been high and blowing directly 8aft40 ,the distance of eighty-four miles has been accomplished in four hours when the wind was 8on the beam10 or a little forward of it1 and on some curves with an almost contrary breeze4 ,the newest machine has four wheels1 each thirty inches in diameter2 it is six feet in length1 and weighs six hundred pounds4 ,the sails are carried upon two masts1 and they contain about eighty-one square feet of canvas4 ,the main1 or principal mast1 is eleven feet high1 four inches in diameter at the base1 and two inches at the top4 ,as in the case of the ice-boats1 it is claimed for the sailing carriage that it frequently outstrips the wind that propels it along the track4 ,on the other hand1 there is a difference between the best sailing points of the two kinds of vehicle4 ,the ice-boat goes quickest with the wind 8dead aft10 the carriage makes best time with the wind 8on the beam0--i4e41 sideways4 ,the greater friction and larger surface exposed to the influence of a side-wind no doubt will account for the difference between the speed of the railway sailing-carriage and the ice-boat4 ,mr4 ,bascom informs us that the carriage we have described is in frequent use upon the ,kansas ,pacific ,railway1 where it is employed to transport materials for the necessary repairs of the line1 telegraph1 etc41 etc4 ,it is a very cheap contrivance1 and a great economizer of labour4 ,we all have noticed the cumbrous method of 8trolly-kicking0 by 8navvies0 along the line4 ,a trolly fitted with a sail would1 in many cases1 and on many ,english lines1 save a great deal of trouble1 time1 and exertion to the plate-layers4 ,,chapter ,,xxxiii4 ,,astronomy4 ,,introductory--,,history ,,of ,,astronomy--,,nomenclature4 ,illustration3 ,fig4 #dic4--;,celestial globe4 ,astronomy is the science which treats of the heavenly bodies and the laws which govern them4 ,the term is derived from two ,greek words1 astron1 a star1 and nomos1 a law4 ,it may be included in the study of ,physics1 for the motion of the planetary bodies and equilibrium1 gravity1 etc41 all have something to say to the arrangements and positions of the stars4 ,the space in which they are set is infinite1 and known as the 8,firmament10 or 8,heaven40 ,the number of the heavenly bodies must therefore be infinite also4 ,we can see a few stars1 comparatively speaking1 and there must be numbers whose light has never yet reached the earth4 ,when we calmly reason upon the immeasurable distances and the awful rapidity of motion1 with the masses of matter thus in movement1 we are constrained to acknowledge that all our boasted knowledge is as nothing in the wondrous dispensations of ,him 8who telleth the number of the stars1 and calleth them all by their names40 ,astronomy1 no more than any other of the physical sciences1 cannot stand by itself4 ,we have seen how heat1 light1 electricity1 etc41 are all1 in a manner1 inter-dependent4 ,so astronomy is dependent upon mathematics1 particularly geometry and trigonometry1 for the wondrous problems to be solved4 ,but in the following sketch we do not propose to plunge the reader in the slough of calculations4 ,we only desire to put plainly before him the great phenomena of nature with regard to the heavens1 and the glorious orbs which so thickly stud the space above us4 ,we need not detail the laborious calculations by which philosophers have arrived at certain discoveries4 ,we may refer to the results and explain general principles1 thereby indicating the road by which the student may arrive at the more difficult bypaths in the fields of scientific discovery4 ,the history of astronomy is nearly as old as the world itself1 or rather as old as the human race4 ,from the earliest ages we can picture men gazing upon the 8spangled heavens10 and the wandering tribes of the desert were always very careful observers of the paths of the stars4 ,to the nomads of the ,east the planetary system served as compass and clock1 calendar and barometer4 ,we shall find1 therefore1 that many observations of the heavenly bodies were made by the ancients1 and have descended to more advanced generations1 and this leads us to remark that the science of astronomy can be studied without any very special or costly apparatus4 ,in other branches of science numerous instruments are indispensable before we can reveal to ourselves the desired results4 ,in astronomy1 a telescope--even a good field glass1 such as possessed by any household1 will reveal many interesting facts4 ,we will1 by means of more expensive instruments1 and by the aid of large telescopes particularly1 enjoy the sight of the moon and planets4 ,but even with the naked eye a great variety of phenomena may be observed4 ,with a celestial globe in our hands upon a fine starry night1 we can easily find out the position of the constellations1 and trace their forms in the firmament4 ,it is to the ,chaldeans1 ,indians1 ,chinese1 and ,egyptians1 that our knowledge of astronomy is primarily due4 ,they did much to facilitate the observation of the stars2 they named the planets1 grouped the stars1 and marked the sun's track in the sky4 ,astrology was cultivated in very remote ages4 ,the ,jews practised it2 and the astrologers of subsequent periods played very important parts in divining the future of individuals1 and casting their horoscopes4 ,many of these so-called predictions came true1 8because10 as was remarked by ,pascal1 8as misfortunes are common they0 7the astrologers7 8are often right10 as they foretold misfortune oftener than good fortune4 ,still the fact remains that occasionally a very startling prediction was made1 and proved true2 such1 for instance1 as the laying waste of ,germany by ,gustavus ,adolphus1 which was foretold by ,tycho ,brah after his consideration of a certain comet1 and the date of the king's death was also correctly prophesied4 ,astrology1 therefore1 held a very considerable influence over the human race during the ,middle ,ages4 ,we can only give a very brief historical summary of the science4 ,we know that the destinies of individuals and nations were at a very early period attributed to the influence of the stars4 ,we read that 8the stars in their courses fought against ,sisera10 and many expressions surviving to the present time serve to remind us that the stars were at one time paramount in men's minds4 ,thus we have the phrases--8unlucky star10 8born under a lucky star10 8mark my stars10 8moonstruck10 etc4 ,even the common term 8consider0--to take counsel of the stars--is thus accounted for1 and many men have a habit of looking up to the ceiling of a room or to the sky when thinking deeply--considering with the stars4 8,contemplate0 is another term signifying the same thing2 for templum1 a temple1 was formerly a space marked upon the sky in imaginary lines1 and traced on the ground in accordance with the supposed diagram4 ,thus temple became a place for heavenly 8contemplation10 and by an easy transition to a place of worship4 ,in our old poets' writings we have many allusions to the influences of the stars4 8,now glowed the firmament ,with living sapphires2 ,hesperus1 that led ,the starry host1 rode brightest1 till the moon1 ,riding in clouded majesty1 at length ,apparent queen1 unveiled her peerless light1 ,and o'er the dark her silver mantle threw40--,,milton4 ,although from ,thales1 who lived ,b4,c4 #faj1 the real science of astronomy may be allowed to date1 there can be no doubt that the ancients were acquainted with many phenomena4 ,the ,chaldeans were1 doubtless1 the first to place on record the rising and setting of the celestial bodies and eclipses1 and used the water-clock 7clepsydra74 ,a list of eclipses from #bbcd ,b4,c4 is stated to have been found at ,babylon by ,alexander the ,great4 ,the ,chaldeans also divided the ecliptic into twelve equal parts1 and the day and night into twenty-four hours4 ,the ,chinese1 again1 have recorded astronomical phenomena as far back as #bheg ,b4,c42 and the ,egyptians also were well versed in the science1 although no records of much importance remain to us1 unless the zodiac signs were their invention4 ,thales predicted the eclipse of the sun ,b4,c4 #faj4 ,aristarchus and ,eratosthenes also made important observations4 ,hipparchus 7#afj-abe ,b4,c47 discovered the precession of the equinoxes1 calculated eclipses1 determined the length of the year1 etc41 etc4 ,ptolemy1 of ,alexandria1 ,a4,d4 #acj-aej1 was the founder of a theory called the ,ptolemaic ,system1 which recognized the earth as the centre of all--the sun1 moon1 stars1 etc41 all revolving in very complicated courses around it1 as figured in the diagram herewith4 ,even though his theory turned out to be untenable1 he paved the way for his successors in other ways1 and left a valuable collection of observations on record4 ,in this volume1 called the 8,almagest10 he reviewed the state of the science1 and gave a catalogue of stars1 as well as a description of the heavens4 ,he discovered the lunar evection4 ,after his time astronomy1 though it was not neglected1 appeared to droop1 and it is at a comparatively late period that we again open the records--viz41 in #aedc1 the year in which ,copernicus died4 ,this philosopher1 who was born in #adgc1 promulgated the true theory of the solar system4 ,he placed the sun in the centre of the planets1 and by this he explained their motion around the sun1 though they appeared to be carried round the earth4 ,the book in which he explained his theory1 8,de ,revolutionibus ,orbium ,celestium10 was not finished till a day or two before he died4 ,illustration3 ,fig4 #did4--,ptolemaic ,system4 ,the justly celebrated ,tycho ,brah was the most important of the successors of ,copernicus1 but he opposed the ,copernican theory1 while other able philosophers agreed with it4 ,brah was a ,dane2 he died in #afja4 ,he adopted the theory that the sun and moon revolved around the earth1 while the 7other7 planets moved around the sun4 ,this theory did not gain much credence1 but he1 again1 though he could not defeat ,copernicus1 and though he was wrong in his assumption1 made many important investigations4 ,after him came ,kepler1 whose observations upon the planet ,mars cleared away many complications1 and he laid down three laws1 which are as follows3-- #a4 ,every planet describes an elliptic orbit about the sun1 which occupies one focus of each such ellipse4 #b4 ,if a line be drawn from the sun1 continually1 to any planet1 this line will sweep over equal areas in equal times4 #c4 ,the squares of the periodic times of the planets are proportional to the cubes of their mean distances from the sun4 ,kepler also remarked that gravity was a power existing between all bodies1 and reasoned upon the tides being caused by the attraction of the moon for the waters4 ,illustration3 ,fig4 #die4--;,copernican ,system4 ,it was about this time--viz41 the beginning of the seventeenth century--that the telescope was invented1 and logarithms came into use4 ,the actual discoverer of this now almost perfected instrument is uncertain4 ,borelli1 who wrote in the seventeenth century1 ascribes the discovery to ,zachariah ,jansen and ,hans ,lippersheim1 spectacle makers of ,middleburg4 ,baptista ,porta1 also a spectacle maker1 has had the credit of discovering the magnifying power of the lens1 and1 so far1 the originator of the telescope4 ,illustration3 ,fig4 #dif4--;,ellipse4 ,illustration3 ,fig4 #dig4--,radii ,vectores4 ,illustration3 ,fig4 #dih4--;,ecliptic and ,equator4 ,but whoever invented it1 the telescope did not penetrate into southern ,europe till #afjh-i4 ,galileo then made inquiries concerning the new instrument1 and ,kepler made some propositions for their construction4 ,but ,harriot had used the instrument so far back as #afaa or #afab1 and had observed spots upon the sun's disc4 ,galileo1 in #afaj1 had also made observations with the telescope1 and discovered the satellites of ,jupiter4 ,he thereby confirmed the ,copernican theory2#be and when ,newton promulgated his immortal discovery of gravitation1 after ,picard's researches1 the relations of the sun and planets became more evident4 ,his researches were published in the ,principia1 and then one-half the scientific world began to question the principle of gravitation1 which was supported by ,newton and his adherents4 ,subsequently the researches of ,lagrange and ,laplace1 ,adams and ,leverrier1 ,sir ,j4 ,herschel1 etc41 brought astronomy into prominence more and more2 and the innumerable stars have been indicated as new planets have been discovered4 ,the spectroscope1 which gives us the analyses of the sun and other heavenly bodies1 has1 in the able hands of living astronomers1 revealed to us elements existing in the vapours and composition of the sun1 etc4 ,stars are now known to be suns1 some bearing a great resemblance to our sun1 others differing materially4 ,the nebul have been analysed1 and found to be stars1 or gas1 burning in space--hydrogen and nitrogen being the chief constituents of this glowing matter4 ,instruments for astronomical observation have now been brought to a pitch of perfection scarcely ever dreamed of1 and month by month discoveries are made and recorded1 while calculations as to certain combinations can be made with almost miraculous accuracy4 ,the transit of ,venus1 the approaches of comets1 eclipses1 and the movements of stars1 are now known accurately1 and commented upon long before the event can take place4 ,we will close this chapter by giving a brief explanation of the various definitions most usually employed in astronomy4 #a4 ,the ,axis of the earth is an imaginary line passing through the centre 7north and south72 the poles are the extremities of this line4 #b4 ,the ,equator is an imaginary circle passing round the globe1 dividing it into northern and southern hemispheres4 ,the equinoctial is the plane of the former circle extended to the heavens1 and when the sun appears in that line the days and nights are of equal duration--twelve hours each4 #c4 ,the ,ecliptic is the sun's path through the heavens--though1 of course1 the sun does not actually move1 and therefore the track1 or supposed circle1 is really the earth's motion observable from the sun4 ,when the moon is near this circle eclipses happen4 ,the ecliptic cuts the equinoctial at an angle of about #bc4 ,one half is to the north and the other to the south of the equinoctial4 ,illustration3 ,fig4 #dii4--,the ,zodiac4 #d4 ,the ,zodiac is a girdle extending #h on each side of the ecliptic1 in which space of #af the planets move4 ,the zodiac is divided into twelve parts of #cj each1 called the 8,signs40 ,these names are as under written3-- ,,northern ,,signs4 ,spring4 ,aries1 the ,ram1 ,march4 ,taurus1 the ,bull1 ,april4 ,gemini1 the ,twins1 ,may4 ,summer4 ,cancer1 the ,crab1 ,june4 ,leo1 the ,lion1 ,july4 ,virgo1 the ,virgin1 ,august4 ,,southern ,,signs4 ,autumn4 ,libra1 the ,balance1 ,september4 ,scorpio1 the ,scorpion1 ,october4 ,sagittarius1 the ,archer1 ,november4 ,winter4 ,capricornus1 the ,goat1 ,december4 ,aquarius1 the ,waterbearer1 ,january4 ,pisces1 the ,fishes1 ,february4 #e4 ,colures are two circles dividing the ecliptic into four equal parts1 and making the seasons4 #f4 ,the ,horizon is the boundary line of our vision1 and is called the sensible 7apparent7 horizon4 ,the true horizon is the circle--as on a globe--dividing the heavens into two hemispheres4 ,the sensible horizon is enlarged according as the eye is elevated above the ground4 ,a man six feet high can see a distance of three miles when standing on a plain4 ,we can always find the distance visible when we know the height at which we stand1 or1 inversely1 we can tell the height of an object if we know the distance4 ,we have only to increase the height one half in feet1 and extract the square root for the distance in miles4 ,on giving the distance in miles reverse the operation4 ,illustration3 ,fig4 #ejj4--,right ascension4 ,for instance1 for the man six feet high1 as supposed1 add three feet1 being half his height2 that makes nine feet4 ,the square root 7or number multiplied by itself to give nine7 is three1 which is the number of miles the man can see on a plain4 ,or1 again1 suppose we can see a tower on the level1 and we know we are twelve miles away from it4 ,the square of twelve is one hundred and forty-four feet1 one-third of that is forty-eight feet1 which represents the half of the original height added to the whole tower in feet2 so the whole tower is ninety-six feet high4 ,reversing1 as in the former case1 we can prove this by taking the tower at ninety-six feet high and trying to find the distance we can see from its summit #if #dh #add2 the square root of #add #ab1 the distance required4 #g4 ,the ,nadir and the ,zenith are the poles of the horizon4 ,the zenith is exactly overhead1 the nadir exactly under foot4 ,circles drawn through these points are azimuth circles4 #h4 ,meridians are circles passing through the poles at right angles to the equinoctial4 ,every place is supposed to have a meridian1 but only twenty-four are upon the globe1 and they represent the sun's1 or the planets'1 8movements0 every hour--#ae being one hour1 #cfj being twenty-four hours 7see fig4 #ejj74 ,one quarter of a degree equals one minute of time4 ,parallels of latitude are familiar circles parallel to the equator4 ,latitude in astronomy is the distance from the ecliptic at a right angle north or south4 ,this will be explained as we proceed4 ,illustration3 ,fig4 #eja4--,orbit of planet4 #i4 ,declination is the distance of the heavenly bodies from the equinoctial measured as a meridian4 ,the ,tropics indicate the limits of the sun's declination4 #aj4 ,disc is the term applied to the apparently flat surface of a planet1 such as the moon1 for instance4 #aa4 ,the ,orbit is the path described by a planet revolving round the sun4 ,the plane of the orbit is an imaginary surface cutting through the centre of the sun and the planet1 and extending to the stars4 ,the diagram shows the plane of the earth's orbit4 ,the circle1 ,a ,b ,c ,d 7fig4 #eja71 is the ecliptic4 ,the inclination of an orbit is the plane of the orbit with reference to the plane of the earth2 and1 supposing the shaded part of the illustration to be water1 a hoop held inclined towards the earth1 with one half in and the other half out of the water1 will describe the planetary orbit4 ,illustration3 ,fig4 #ejb4--;,conjunction of ,venus and ,saturn4 #ab4 ,nodes are the opposite points of a planet where its orbit cuts the ecliptic or the earth's orbit4 #ac4 ,apogee is the point of a planet's orbit farthest from the earth4 ,perigee is the nearest point4 #ad4 ,the terms ,culmination1 ,conjunction1 and ,opposition require no special explanation4 ,but planets are in conjunction with each other when in the same sign and degree4 ,a planet with the sun between it and the earth is in conjunction with the sun4 ,with the earth between it and the sun it is in opposition4 #ae4 ,latitude and longitude upon a celestial globe are known respectively as 8,declination0 and 8,right ,ascension40 #af4 ,the ,radius ,vector is a line drawn from a planet to the sun1 wherever the planet may be 7see fig4 #dig74 ,,footnotes3 #be ,he was obliged to recant before the ,inquisition1 and to repudiate his researches4 ,he was released on the condition of observing silence upon the theory he had supported1 but again obliged to recant4 ,,chapter ,,xxxiv4 ,,angles ,,and ,,measurement ,,of ,,angles4 ,,the ,,quadrant--,,transit ,,instrument--,,clocks--,,stellar ,,time--,,solar ,,time--8,,mean0 ,,time4 ,we must say a few words respecting the various instruments and aids to astronomical observation before proceeding1 for astronomy requires very accurate calculations2 and though we do not propose to be very scientific in our descriptions1 some little idea of the manner in which observations may be made is necessary4 ,the first thing to see about is the ,,angle4 ,suppose we draw four lines on a piece of paper1 ab and cd4 ,these intersect at a point1 m4 ,we have then four spaces marked out1 and called angles4 ,the four angles are in the diagram all the same size1 and are termed right angles1 and the lines containing them are perpendicular to each other4 ,illustration3 ,fig4 #ejc4--,right angles4 ,but by altering the position of the lines 7see fig4 #ejd71 we have two pairs of angles quite different from right angles2 one angle1 a m c1 is smaller1 while a m d is much larger than the right angle4 ,the former kind are called acute1 the latter obtuse angles4 ,we can therefore obtain a great number of acute angles1 but only three obtuse1 and four right angles around a given point1 m4 ,illustration3 ,fig4 #ejd4--,obtuse and acute angles4 ,the length of the sides of an angle have no effect on its magnitude1 which is determined by the inclination of the lines towards each other4 ,we now may consider the magnitude of angles1 and the way to determine them4 ,for this purpose we must describe a circle1 which is figured in the diagram4 ,but what is a circle8--,a circle is a curved line which always is at the same distance from a certain fixed point1 and the ends of this line meet at the point from which the line started4 ,illustration3 ,fig4 #eje4--,the circle1 etc4 ,if we fasten a nail or hold a pencil on the table1 and tie a thread to it1 and to the other end of the thread another pencil1 we can describe a line around the first pencil by keeping the thread tightly stretched4 ,this line is at all points at equal distance from the centre point4 ,any line from the centre to the circumference is called a radius1 and a line through the centre to each side of the circumference is the diameter1 or double the radius4 ,the circumference is three 7#cad7 times the diameter4 ,any portion1 say k i l1 is an arc1 and the line1 k l1 is the chord of that arc4 ,a line like m n is a secant1 and o p is a tangent1 or a line touching at one point only4 ,we may now resume our consideration of the angles by means of the circle4 ,let us recur to our previous figure of the right angles1 around which we will describe a circle4 ,we see that the portion of the circumference contained between the sides of the right angle is exactly one-fourth of the whole4 ,this is termed a quadrant1 and is divided into #ij--the fourth of #cfj equal parts or degrees into which the whole circumference is divided4 ,the angle of #de so often quoted as an angle of inclination is half a right angle4 ,to measure angles an instrument called a ,protractor is used4 ,illustration3 ,fig4 #ejf4--;,circle and angles4 ,illustration3 ,fig4 #ejg4--,the ,protractor4 ,the ,protractor1 as will be seen from the accompanying illustration 7fig4 #ejg71 is a semi-circle containing #ahj4 ,the lower portion is a diagonal scale1 the use of which will be explained presently4 ,the ,protractor measures any actual angle with accuracy4 ,if we put the vertical point of the angle and the centre point of the circle together1 we can arrive at the dimensions of the angle by producing the lines containing it to the circumference4 ,an angle instrument1 figured herewith1 may be assumed as the basis of most apparatus for measuring angles4 ,an index hand1 ,r ,r1 moves round a dial like the hand of a clock1 and the instrument is used by gazing first at one of the two objects1 between which the angle we wish to determine is made--like the church steeples 7fig4 #ejh7 for instance4 ,the centre of the instrument is placed upon the spot where lines1 if drawn from the eye to each of the objects1 would intersect4 ,the index hand is then put at #j1 and in a line between the observer and the object1 ,a4 ,then the index is moved into a similar position towards ,b1 and when in line with it the numbers of degrees passed over 7in this imaginary case #bj71 shows the magnitude of the angle4 ,illustration3 ,fig4 #ejh4--;,determination of distance4 ,illustration3 ,fig4 #eji4--,measuring angles4 ,the simple quadrant is shown in the cut 7fig4 #eaj74 ,this was so arranged that when any object in the horizon was being looked at through the telescope attached1 a plummet line is at #j4 ,but if the telescope be raised to ,c ,s1 the quadrant will move1 and the line will mark a certain number of degrees of the angle which a line if drawn from the star makes with the line of the horizon4 ,the 8,astronomical ,quadrants0 are as shown in fig4 #eaf1 and consist of a quadrant of wood strengthened and fitted with a telescope4 ,the circle is graduated on the outer edge1 and a 8vernier0 is attached4 ,the time is determined by the observation of the altitude of a star1 and then by calculation finding out at what time the star would have the observed altitude4 ,the quadrant is now superseded by circular instruments4 ,illustration3 ,fig4 #eaj4--,the quadrant4 ,illustration3 ,fig4 #eaa4--;,ellipse4 ,an ellipse is a flattened circle1 or oval1 and will be understood from the diagrams4 ,let us fix two pegs upon a sheet of paper1 and take a thread longer than the distance between the pegs2 draw with the pencil controlled by the thread a figure1 keeping the thread tight4 ,we shall thus describe an oval1 or ellipse4 ,the orbit of nearly all the heavenly bodies is an ellipse4 ,the parabola is another curved line1 but its ends never meet2 they become more and more distant as they are continued4 ,the comets move in parabolic curves1 and consequently do not again come within our vision unless their direction be altered4 ,illustration3 ,fig4 #eab4--;,ellipse4 ,this figure has a long axis1 ab 7fig4 #eab72 and perpendicular to this a short axis1 de1 passing through the centre1 c4 ,the two points1 ,,ss1 are called the foci of the ellipse2 also1 as is evident from the construction of the figure1 any two lines drawn from the two foci1 to any point of the circumference1 for instance1 ,s and ,sm1 or ,sm and ,sm1 etc41 which represent the thread when the pencil is at m or m1 are together equal to the larger axis of the ellipse4 ,these lines1 and we may imagine an infinite number of such1 are called radii vectores4 ,the distance of the foci1 ,s or ,s1 from the centre1 c1 is called the eccentricity of the ellipse4 ,it is evident that the smaller the eccentricity is1 the nearer the figure approaches to that of the circle4 ,the superficies of the ellipse is found by multiplying the two half axes1 ac and dc1 by each other1 and this product by the number #cad4 ,illustration3 ,fig4 #eac4--;,diagonal scale4 ,the ,diagonal ,scale is shown in the margin4 ,it is used to make diagrams so as to bring the relative distances before the eye4 ,the larger divisions represent1 it may be1 miles1 or any given distance2 the figures on the left side tenths1 and the upper range hundredths of a mile4 ,so a measurement from ,z to ,z will represent two miles1 we may say1 with so many tenths and hundredths4 ,illustration3 ,fig4 #ead4--,transit instrument4 ,the ,transit instrument is due to ,roemer1 a ,danish astronomer4 ,it consists of a telescope so constructed as always to point to the meridian1 and rotates upon a hollow axis1 directed east and west4 ,at one end is a graduated circle4 ,the optical axis of the telescope must be at exactly right angles to the axis of the instrument2 it will then move on the meridian4 ,there is an eye-piece filled with two horizontal and five vertical wires1 very fine1 the latter at equal distances apart4 ,the star appears1 and the time it takes to cross is noted as it passes between each wire1 and the mean of all the transits will be the transit on the meridian4 ,for if we add the times of all the transits across the wires1 and divide by five the number of them we shall get at a true result4 ,illustration3 ,fig4 #eae4--,the eyepiece of transit instrument4 ,a good clock is also a necessary adjunct for astronomical observations1 and the astronomical clocks and chronometers now in use record the time with almost perfect accuracy4 ,the improvement in telescopes1 the use of micrometers1 etc41 have greatly facilitated observations4 ,in the transit clock we have a most useful timekeeper1 for the ordinary clocks are not sufficiently accurate for very close observations4 ,the sidereal time differs from solar time1 and the twenty-four hours' period is calculated from the moment a star passes the meridian until it passes it again4 ,the sidereal day is nearly four minutes shorter than the solar day1 and the sidereal clock marks twenty-four hours instead of twelve1 like the old dial at ,hampton ,court ,palace over the inner gate4 ,the ,chronograph has also been useful to astronomers1 for by 8pricking off0 the seconds on a roller by itself1 the observer can mark on the same cylinder the actual moment of transit across each wire of the instrument1 and on inspection the exact moment of transit may be noted4 ,the ,equitorial is another useful instrument1 and by its means the whole progress of a star can be traced4 ,the ,equitorial consists of a telescope fixed so that when it has been pointed at a certain star a clock-work movement can be set in motion1 which exactly corresponds with the motion of the star across the heavens1 and so while the star moves from its rising to setting it is under observation4 ,thus continuous observations maybe made of that particular star or comet without any jerking or irregular movement4 ,we can thus see the uniform motion of the stars which go on in greater or lesser circles as they are nearer to or farther from the pole2 and with the exception of the polar star1 which1 so far as we are concerned1 may be considered stationary1 every star moves round from east to west--that is1 from the east of the polar star to the west of it1 in an oblique direction4 ,therefore1 as ,professor ,airy remarks1 8,either the heavens are solid1 and go all of a piece1 or the heavens may be assumed to be fixed or immovable1 and that we and the earth are turning instead of them40 ,illustration3 ,fig4 #eaf4--;,astronomical quadrant4 ,the ,mural ,circle is another very useful instrument1 and is used by calling to aid the powers of reflection of quicksilver1 in which a bright star will appear below the horizon at the same angle as the real star above the horizon1 and thus the angular distance from the pole or the horizon of any star can be calculated when we know the inclination of the telescope4 ,the ,transit ,circle is also used for this purpose1 and is a combination of the transit instrument with the circle4 ,in all calculations allowance must be made for refraction1 for which a 8,table of ,refractions0 has been compiled4 ,from the zenith to the horizon refraction increases4 ,the effect of refraction can be imagined1 for when we see the sun apparently touching the horizon the orb is really below it1 for the refraction of the rays by the air apparently raises the disc4 ,the clock and chronometer are both very useful as well as very common objects1 but a brief description of the pendulum and the clock may fitly close our remarks upon astronomical apparatus and instruments4 ,the telescope has been already described in a previous portion of this work1 so no more than a passing reference to it has been considered necessary4 ,we therefore pass on to a consideration of the measurement of time1 so important to all astronomers and to the public generally4 ,time was measured by the ancients by dividing the day and night into twelve hours each1 then by sun-dials and water-clocks1 or clepsydra1 and sand-clocks4 ,the stars were the timekeepers for night before any mechanical means of measurement were invented4 8,what is the star now passing8-- ,the ,pleiades show themselves in the east1 ,the eagle is soaring in the summit of heaven40--,,euripides4 ,sun-dials were in use in ,elijah's time1 and the reference to the miracle of the sun's shadow going back on the dial as a guarantee to ,hezekiah1 will be recalled at once by our readers4 ,these dials were universal1 and till sunset answered the purpose4 ,but the hours must have been very varying1 and on cloudy days the sun-dials were practically useless4 ,the water-clocks measured time by the dripping or flow of water1 and they were used to determine the duration of speeches1 for orators were each allotted a certain time if a number of debaters were present4 ,this method might perhaps be adapted to the ,house of ,commons1 and speaking by the clock might supersede clture4 ,we find allusions to these practices in the orations of ,demosthenes4 ,even this system was open to objection1 for the vases were frequently tampered with1 and an illiberal or objectionable person was mulcted of a portion of the water1 while a generous or popular adversary had his clepsydra brimming full4 ,some of these water-clocks were of elegant design1 and a ,cupid marked the time with arrows on the column of the clock of ,ctesibius1 while another weeping kept up the supply of water4 ,the motive power was the water1 which filled a wheel-trough in a certain time1 and when full this trough turned over1 and another was filled4 ,the wheel revolved once in six days2 and by a series of pinions and wheels the movements were communicated more slowly to the pillar on which the time was marked for #cfj days1 or with other arrangements for twenty-four hours4 ,the repeating of psalms by monks also marked the time1 for by practice a monk could tell pretty accurately how many paternosters or other prayer he could repeat in sixty seconds4 ,at the appointed hour he then awoke the monastery to matins4 ,nature also marks time for us--as1 for example1 the age of trees by means of rings--one for each year2 and horses' teeth will guide the initiated to a guess at the ages of the animals1 while the horns of deer or cattle serve a like purpose4 ,but man required accuracy and minute divisions of time4 ,he had recourse therefore1 to machinery and toothed wheels4 ,till the mechanical measurement of time was adopted1 the sunrise and sunset only marked the day1 and the ,italians as well as ,jews counted twenty-four hours from sunset to sunset4 ,this was a manifestly irregular method4 ,to this day we have marked differences of time in various places1 and at ,geneva we have ,swiss and ,french clocks keeping different hours according to ,paris or ,berne 8time40 ,this1 of course1 is easily accounted for1 and will be referred to subsequently4 ,illustration3 ,fig4 #eag4--;,clock movement4 ,we have read that the first clock in ,england was put up in ,old ,palace yard in #abhh1 and the first application of the toothed-wheel clock to astronomical purposes was in #adhd1 by ,waltherus1 of ,nuremberg4 ,tycho ,brah had a clock which marked the minutes and seconds4 ,if we had had any force independent of gravitation which would act with perfect uniformity1 so that it would measure an equal distance in equal spaces of time1 all the various appliances for chronometers would have been rendered useless4 ,in the supposed case the simple mechanism1 as shown in the margin 7fig4 #eag71 would have sufficed4 ,the same effect would be produced by the spring1 were it possible that the spring by itself would always uncoil with the same force4 ,but it will not do so3 we therefore have to check the unwinding of the cord and weight1 for left to itself it would rapidly increase in velocity2 and if we likewise make an arrangement of wheels whereby the spring shall uncoil with even pressure all the time1 we shall have the principle of the watch4 ,it is to ,huygens that the employment of the pendulum in clocks is due1 and the escapement action subsequently rendered the pendulum available in simple clocks1 while the manner of making pendulums self-regulating by using different metals1 has rendered timepieces very exact4 ,of course the length of a pendulum determines the movement1 fast or slow2 a long pendulum will cause the hands of the clock to go slower1 for the swing will be a fraction longer4 ,a common pendulum with the escapement is shown 7fig4 #eah74 ,each movement liberates a tooth of the escapement4 ,the arrangement of wheels sets the clock going4 ,the forms of pendulum are now very varied4 ,but in watches the pendulum cannot be used4 ,the watch was invented by ,peter ,hele1 and his watches were called 8,nuremburg eggs0 from their shape4 ,the weight cannot be introduced into a watch1 and so the spring and fusee are used4 ,the latter is so arranged that immediately the watch is wound and the spring at its greatest tension1 the chain is upon the smallest diameter of the fusee1 and the most difficult to move4 ,but as the spring is relaxed the lever arm becomes longer1 and the necessary compensating power is retained4 ,watches without a 8fusee0 have a toothed arrangement beneath the spring4 ,the ,pendulum4 ,a 8simple0 pendulum is impossible to make1 for we cannot put the connecting line between the 8bob0 and the clock-work out of consideration1 so 8simple pendulums0 are looked upon as 8mathematical abstractions40 ,the most modern clocks have what is called a 8deadbeat0 escapement1 and a compensating pendulum4 ,clocks are liable to alter by reason of the state of the air and varying temperature1 and until all our clocks are placed in vacuo we must be content to have them lose or gain a little4 ,there is a magnet arrangement by which the ,greenwich ,observatory clocks keep time by compensation1 corresponding with the fall or rise of the syphon barometer attached to it4 ,the description need not be added4 ,we may here state that detailed descriptions of all the instruments used in the ,observatory1 together with full information as to their use1 will be found in a very interesting work by ,mr4 ,lockyer1 entitled 8,stargazing10 to which we are indebted for some corrections in our summary4 ,illustration3 ,fig4 #eah4--,pendulum and escapement4 ,illustration3 ,fig4 #eai4--;,balance4 ,illustration3 ,fig4 #ebj--,regulator4 ,we have spoken of solar time and sidereal time1 and no doubt someone will inquire what is meant by mean time--an expression so constantly applied to the ,greenwich clock time4 ,stellar time1 we have seen1 corresponds to the daily revolution of a star or stars4 ,solar time is regulated by the sun1 and this is the astronomical time generally observed1 except for sidereal investigations4 ,but the sun is not always regular2 the orbit of the earth causes this irregularity partly4 ,the earth moves faster in winter than in summer1 so the sun is sometimes a little fast and sometimes a little slow4 ,astronomers therefore strike an average1 and calculate upon a ,,mean ,,sun1 or uniform timekeeper4 ,mean time and true 7apparent7 time are at some periods the same--viz41 on the #aeth of ,april1 on the #adth of ,june1 on the #cast of ,august1 and on the #bdth of ,december4 ,twice it is after1 and twice before it4 ,the time occupied by this 8mean0 sun passing from the meridian and its return to it1 is a mean solar day1 and clocks and chronometers are adjusted by it4 ,illustration3 ,fig4 #eba4--;,fusee and spring4 ,twenty-four hours represents a complete revolution of the heavenly bodies4 ,the mean solar time is #bc;h #ef #djia1 while twenty-four hours of mean time are equal to #bd;h #c #efee of sidereal time4 ,the difference between the times is given by ,dr4 ,newcomb as follows1 and is called the ,equation of ,time3-- ,,differences ,,between ,,mean ,,and ,,apparent ,,time4 ,february #ajth ,true ,sun #ae minutes slow4 ,april #aeth 8 ,correct4 ,may #adth 8 #d minutes fast4 ,june #adth 8 ,correct4 ,july #beth 8 #f minutes slow4 ,august #cast 8 ,correct4 ,november #bnd 8 #af minutes fast4 ,december #bdth 8 ,correct4 ,,measurement ,,of ,,distances4 ,before passing to consider the planetary system we must say a few words respecting the manner of ascertaining the distances of inaccessible objects1 and by so doing1 we shall arrive at an idea how the immense distances between the sun 7and the planets7 and the earth have been so accurately arrived at4 ,to do this we must speak of parallax1 a very unmeaning word to the general reader4 ,illustration3 ,fig4 #ebb4--,works of a clock4 ,parallax is simply the difference between the directions of an object when seen from two different positions4 ,now we can illustrate this by a very simple method1 which we have often tried as a 8trick10 but which has been very happily used by ,professor ,airy to illustrate the doctrine of parallax4 ,we give the extract in his own words3-- 8,if you place your head in a corner of a room1 or on a high-backed chair1 and if you close one eye and allow another person to put a lighted candle upon a table1 and if you then try to snuff the candle with one eye shut1 you will find you cannot do it4444 ,you will hold the snuffers too near or too distant--you cannot form any idea of the distance4 ,but if you open the other eye1 or if you move your head sensibly you are enabled to judge of the distance40 ,the difference of direction between the eyes1 which is so well known to all1 is ready a parallax4 ,it can also be illustrated by the diagram herewith4 ,illustration3 ,fig4 #ebc4--,parallax4 ,if two persons1 ,a and ,c 7fig4 #ebc71 from different stations1 observe the same point1 ,m1 the visual lines naturally meet in the point1 ,m1 and form an angle1 which is called the angle of parallax4 ,if the eye were at ,m1 this angle would be the angle of vision1 or the angle under which the base line1 ,a ,c1 of the two observers appears to the eye4 ,the angle at ,m also expresses the apparent magnitude of ,a ,c when viewed from ,m1 and this apparent magnitude is called the parallax of ,m4 ,let ,m represent the moon1 ,c the centre of the earth represented by the circle1 then ,a ,c is the parallax of the moon2 that is1 the apparent magnitude the semi-diameter of the earth would have if seen from the moon4 ,if the moon be observed at the same time from ,a1 being then on the horizon1 and from the point ,b1 being then in the zenith1 and the visual line of which when extended passes through the centre of the earth1 we obtain1 by uniting the points1 ,a ,c ,m1 by lines1 the triangle1 ,a ,c ,m4 ,therefore1 as ,a ,m1 the tangent of the circle stands at right angles to the radius1 ,a ,c1 the angle at ,a is a right angle1 and the magnitude of the angle at ,c is found by means of the arc1 ,a ,b1 the distance of the two observers from each other4 ,as soon1 however1 as we are acquainted with the magnitude of two angles of a triangle1 we arrive at that of the third1 because we know that all the angles of a triangle together equal two right angles 7#ahj74 ,the angle at ,m1 generally called the moon's parallax1 is thus found to be fifty-six minutes and fifty-eight seconds4 ,we know that in the right-angled triangle ,m ,c ,a1 the measure of the angle1 ,m #ef #eh1 and also that ,a ,c1 the semi-diameter of the earth #c1ifd miles4 ,this is sufficient1 in order by trigonometry1 to obtain the length of the side1 ,m ,c2 that is1 to find the moon's distance from the earth4 ,a ,c is the sine of the angle1 ,m1 and by the table the sine of an angle of #ef #eh is equal to #afeb_/ajjjjj2 or1 in other words1 if we divide the constant1 ,m ,c1 the distance of the moon1 into #ajj1jjj equal parts1 the sine1 ,a ,c1 the earth's semi-diameter #a1feb of these parts4 ,and this last quantity being contained #fj times in #ajj1jjj1 the distance of the moon from the earth is equal to #fj semi-diameters of the earth1 or #fj #cifd #bcg1hdj miles4 ,illustration3 ,fig4 #ebd4--,parallax explained4 ,in a similar way the parallax of the sun has been found #hf1 and the distance of the sun from the earth to be #ia1jjj1jjj miles4 ,let us first see how we can obtain the distance of any inaccessible or distant object4 ,we have already mentioned an experiment1 but this method is by a calculation of angles4 ,the three angles of a triangle1 we know1 are equal to two right angles2 that is an axiom which cannot be explained away4 ,we first establish a base line2 that is1 we plant a pole at one point1 ,a1 and take up our position at another point1 ,b1 at some distance in a straight line1 and measure that distance very carefully4 ,by means of the theodolite we can calculate the angles which our eye1 or a supposed line drawn from our eye to the top of the object 7,c7 we wish to find the distance of1 makes with that object4 ,we now have an imaginary triangle with the length of one side1 ,a ,b1 known1 and all the angles known2 for if all three angles are equal to #ahj1 and we have calculated the angles at the base1 we can easily find the other4 ,we can then complete our triangle on paper to scale1 and find out the length of the side of the triangle by measurement2 that is the distance between our first position1 ,a1 and the object1 ,c4 ,it is of course necessary that all measurements should be exact1 and the line we adopt for a base should bear some relative proportion to the distance at which we may guess the object to be4 ,in celestial measurements two observers go to different points of the earth1 and their distance in a straight line is known1 and the difference of the latitudes4 ,by calling the line between the observers a base line1 a figure may be constructed and angles measured2 then by some abstruse calculation the distance between the centre of the earth and the centre of the moon may be ascertained4 ,the mean distance is sixty times the radius of the earth4 ,the measurement of the sun's distance is calculated by the observations of the transit of ,venus across his disc1 a phenomenon which will again occur on #fth ,december1 #ahhb1 and on #hth ,june1 #bjjd1 the next transit will take place2 there will be no others for a long time after #bjjd4 ,all astronomical observations are referred to the centre of the earth1 but of course can only be viewed from the surface1 and correction is made4 ,in the cut above1 let ,e be the earth and ,b a point on the surface4 ,from ,b the stars1 a b c d1 will be seen in the direction of the dotted lines1 and be projected to e i k l respectively4 ,but from the centre of the earth they would appear at e f g h correctly4 ,the angles formed by the lines at b c d are the parallactic angles1 f i g h and h l show the parallax4 ,an object on the zenith thus has no parallax4 7,see fig4 #ebd47 ,illustration3 ,fig4 #ebe4--;,halo ,nebul4 ,,chapter ,,xxxv4 ,,the ,,solar ,,system4 ,,gravitation--,,the ,,planets--,,size ,,and ,,measurement ,,of ,,the ,,planets--,,satellites--,,falling ,,stars--,,comets--,,aerolites4 ,illustration3 ,fig4 #ebf4--,planets compared with a quarter of the sun4 ,,gravitation is the force which keeps the planets in their orbits1 and this theory1 perfected by ,newton1 was partially known to ,kepler4 ,newton brought this idea into practical shape1 and applied it mathematically4 ,we know that every object in the world tends to attract every other object in proportion to the quantity of matter of which each consists4 ,so the sun attracts the planets1 and they influence him in a minor degree4 ,likewise the moon and our earth reciprocally attract each other4 ,but as the sun's mass is far greater than the masses of the planets he influences them more1 and could absorb them all without inconvenience or disturbance from his centre of gravity4 ,we have1 in a former portion of this work1 spoken of the law of universal gravitation1 which is the mutual attraction of any two bodies to each other1 is directly proportioned to their masses 7not size71 and inversely to the square of their distances apart4 ,this law operates amongst the heavenly bodies1 and it is to the never-changing action of gravitation that the planets are kept in their places4 ,let us see how this is effected4 ,we have read of force1 and motion1 and rest4 ,every body will remain at rest unless force compels it to change its position1 and it will then go on for ever in a straight path unless something stops it4 ,but if this body be acted on simultaneously by two forces in different directions1 it will go in the direction of the greater force4 ,two equal forces will tend to give it an intermediate direction1 and an equal opposing force will stop it4 ,the last axiom but one--viz41 the two equal forces in different1 not opposing directions1 gives us the key to the curving line of the planetary motions4 ,were it not for the attraction of the sun the planets would fly off at a tangent2 while1 on the other hand1 were not the impelling force as great as it is1 they would fall into the sun4 ,thus they take an intermediate line1 and circle round the centre of the solar system--the ,,sun4 ,the solar system consists of the sun and the planets which revolve in space around him4 ,these stars are called planets because they move in the heavens4 ,we shall see that they have certain motions--going from east to west1 from west to east1 and sometimes they appear to be quite motionless4 ,this change of place1 appearing now at one side of the sun and now at another1 has given them their title of 8wanderers0 7planets74 ,besides the planets there are comets and meteors1 asteroids and satellites1 all circling round the sun in more or less regular orbits4 ,and there must be families of comets1 and whole systems of meteors that have not yet appeared to us1 and which make up the comets1 as has been lately suggested4 ,five planets were known to the ancients1 and were named after gods and a goddess3 ,,mercury1 ,,venus1 ,,mars1 ,,jupiter1 ,,saturn4 ,in later years a great number were discovered4 ,we must1 however1 confine ourselves to the consideration of the principal ones1 eight in number1 including our own ,,earth1 ,,uranus and ,,neptune completing the list4 ,of these ,,venus and ,,mercury are the inferior1 or interior planets moving between us and the sun4 ,,mars1 ,,jupiter1 ,,saturn1 ,,uranus1 and ,,neptune are superior1 or exterior1 and pass quite round the heavens4 ,all the planets are spheroids1 and vary greatly in their magnitude1 as will be seen by the illustration 7fig4 #ebh71 the largest body being the sun4 ,mercury1 ,mars1 and ,venus1 are not so large as the ,earth4 ,the other principal planets are considerably larger than our globe4 ,illustration3 ,fig4 #ebg4--,the ,moon4 ,mercury is the smallest of the planets1 ,venus being nearly as large as the earth4 ,then comes ,mars1 which1 though smaller than ,venus1 is larger than ,mercury4 ,jupiter is the largest of all--the giant amongst planets1 as ,jove was the ruler of the gods of mythology4 ,saturn comes next1 though much smaller than ,jupiter1 but bigger than all the rest together4 ,next ,uranus1 then ,neptune1 larger than ,uranus1 but farther away from us4 ,we shall speak more in detail about these in their order separately4 ,illustration3 ,fig4 #ebh4--;,comparative size of the sun seen from the planets4 ,taking the earth as #a1 the comparative ,,volumes of the planets are as follows3-- ,mercury #a_/be1 ,venus #d_/e1 ,mars #a_/e1 ,jupiter #acjj1 ,saturn #ijj1 ,uranus #hj1 ,neptune #bcj4 ,sir ,john ,herschel gives the following illustration of magnitudes and distances3-- 8,choose any well-levelled field or bowling green2 on it place a globe two feet in diameter2 this will represent the sun4 ,mercury will be represented by a grain of mustard seed on the circumference of a circle #afd feet in diameter for its orbit2 ,venus a pea1 on a circle #bhd feet in diameter2 the ,earth also a pea on a circle #dcj feet2 ,mars a rather large pin's head on a circle of #fed feet2 ,juno1 ,ceres1 ,vesta1 and ,pallas grains of sand in orbits of #a1jjj to #a1bjj feet2 ,jupiter a moderate-sized orange on a circle nearly half a mile across2 ,saturn a small orange on a circle four-fifths of a mile2 and ,uranus a full-sized cherry1 or small plum1 upon the circumference of a circle more than a mile and a half in diameter0 ,illustration3 ,fig4 #ebi4--,sizes of the planets4 ,illustration3 ,fig #ecj4--,sizes of planets4 ,illustration3 ,fig4 #eca4--,orbits of planets4 ,from an inspection of the following table the relative distances of the principal planets from the sun1 their diameters1 and other information respecting them may approximately be obtained4 ,the dates of the discovery of the more modern pair are added3-- ---------------------------------------- --------------------- ,names4 ,diameters,distance from ,sidereal ,time of ,date of in the sun period of rotation discovery4 ,english 7about74 revolution4 on their miles axis4 7about74 ---------------------------------------- --------------------- d4 h4 m4 d4 h4 m4 ,,mercury #c1jjj #ce1jjj1jjj #hg #bc #af #bd #e -- ,antiquity ,,venus #g1ejj #ff1jjj1jjj #bbd #af #ej #bc #ba #ba do4 ,,earth #h1jjj #ia1jjj1jjj #cfe #f #i #bc #ef #d do4 ,,mars #d1ejj #aci1jjj1jjj #fhf #bc #ca #bd #cg #bj do4 ,,jupiter #he1jjj #dgf1jjj1jjj #d1ccb #ad #b #i #ee #ba do4 ,,saturn #gj1jjj #hgb1jjj1jjjaj1gei #e #af #aj #af -- do4 ,,uranus #cc1jjj #a1gec1jjj1jjjcj1fhf #ag #ba #i #cj -- ,herschel1 #agha4 ,,neptune #cg1jjj #b1gdf1jjj1jjjfj1abf #ag #e 4 4 4 ,leverrier and ,galle1 #ahdf4 ,,the ,,sun #hej1jjj 4 4 4 4 4 4 4 4 #be #g #dh ---------------------------------------- --------------------- ,altogether there are a great number of planets and asteroids1 which latter are minor planets circulating outside the orbit of ,mars4 ,they have nearly all classical names1 such as ,juno1 ,ceres1 ,vesta1 ,flora1 ,ariadne1 ,pallas1 ,pomona1 ,thalia1 etc41 and are all at distances from the sun ranging between #bjj1jjj1jjj and #cjj1jjj1jjj of miles1 the periods of sidereal revolution ranging from #a1ajj to #c1jjj days1 so their years must be from four times to nine times as long as ours4 ,altogether about two hundred of the minor planets have been discovered1 and they are all very much smaller than the earth2 some1 indeed1 being very tiny--only a few miles in diameter1 but very massive4 ,they do not appear to possess any satellites--at least1 none have been discovered1 for such very small bodies as they must be1 supposing they exist1 would be quite invisible even with our perfected instruments4 ,illustration3 ,fig4 #ecb4--,mars4 ,,satellites1 however1 or 8planetary moons10 as they are sometimes designated1 are plainly perceived attending upon the great planets4 ,there are twenty of these at present under observation4 ,one we are all familiar with1 and the moon1 par excellence1 lends a beauty to our nights which no other light that we can enjoy or command can ever do4 ,it is remarkable that only this moon is specially mentioned in the ,bible in connection with the sun4 ,the stars are usually grouped1 although1 of course1 the sun and moon are equally 8stars0 in the firmament4 ,mars possesses two moons and ,jupiter four2 ,uranus also rejoices in the latter number2 ,neptune1 like the ,earth1 has only one4 ,it is reserved for ,saturn to outstrip all the rest in his attendants1 for no less than eight satellites wait upon that enormous planet4 ,no doubt there are many more of these moons to be found1 and every year will doubtless bring us further knowledge respecting them4 ,mars' moons were only discovered very lately 7in #ahgg71 although they were known to exist2 but being very small1 unlike the others1 they were missed4 ,so we may conclude that the remaining satellites will remain for some time undiscovered1 even if they actually are in existence4 ,jupiter's moons are supposed to be as large as our own moon2 ,neptune and ,uranus can boast of equally-sized attendants4 ,but it is impossible to estimate the riches of astronomical lore which are beyond our ken4 ,millions of tiny planets are believed to exist1 but their immense distance from us precludes all investigation4 ,we are but mites in the scale4 ,illustration3 ,fig4 #ecc4--;,jupiter4 ,illustration3 ,fig4 #ecd4--,saturn4 ,illustration3 ,fig4 #ece4--,meteor shower4 ,,meteors1 to which we have already referred1 are small erratic bodies rushing through the planetary system1 and getting hot in the process1 appear in the atmosphere surrounding our earth as 8shooting stars40 ,some of these falling bodies have reached the earth1 and several can be seen in the ,british ,museum4 ,numbers1 of course1 are burnt up before they reach us1 and who can tell what destruction such a catastrophe may represent1 or whether it be or be not an inhabited world which has thus plunged to destruction by fire8 ,they are of a metallic or stony nature4 ,on certain nights in ,august and ,november it has been calculated that these meteors will appear4 ,they fall from certain constellations apparently on these occasions1 and are called after their names--as ,leonides1 from ,leo1 in the ,november displays4 ,the star-showers at times attain the dimensions of a very beautiful display of rockets4 ,millions of them rush round the sun2 and when1 as occasionally happens1 our earth comes near them1 we have 7as in #ahff7 a grand display of celestial 8fireworks40 ,but the individuals composing the mass of falling stars are very small4 ,these meteors are very much like the comets we last year had an example of1 and it has been lately suggested that there is a great degree of affinity between the comets and the meteors2--in fact1 that a comet is merely an aggregation of meteors4 ,they have been supposed to be bodies of burning gas4 ,their mass is very great1 and their brilliant tails are many millions of miles in extent4 ,comets are thus distinguished by their tails1 and differ very much in their orbits from the planets4 ,the latter are direct in their wanderings1 but comets are most irregular and eccentric4 ,the name bestowed upon comets is from the ,greek ,kome1 hair2 for when the comet recedes from the sun the 8tail0 may be said to come out of the head1 and appear as a hair in front1 so to speak4 ,but though all comets have tails1 there are many luminous bodies 7classed with comets7 which have no tails4 ,illustration3 ,fig4 #ecf4--,star shower4 ,illustration3 ,fig4 #ecg4--;,halley's ,comet4 ,the comet which created the most excitement was ,halley's in #adef1 of which we append an illustration 7fig4 #ecg74 ,a comet had been observed in #afjg1 and ,halley made a calculation that it would reappear in #ageg4 ,the calculation for its actual appearance was made by ,claivant1 and the expected visitor passed the perihelion in ,march #agei4 ,this comet1 on its appearance at ,constantinople1 is said to have caused much consternation1 and ,christians regarded it as a 8sign10 for the ,turks had just then captured ,constantinople1 and were threatening ,europe4 ,pious people included it in their supplications for deliverance from their most dreaded enemies1 and 8,lord1 save us from the ,turks1 the devil1 and the comet10 was a common prayer4 ,illustration3 ,fig4 #ech4--;,great comet of #ahaa4 ,there have been several very beautiful comets4 ,encke's1 ,coggia's1 etc41 and the comet of #aheh 7,donatis7 must be in the recollection of middle-aged readers4 ,others came in #ahfa and #ahgd4 ,in #ahha two comets appeared4 ,some comets of antiquity were very remarkable1 and are reputed to have equalled the sun in magnitude4 ,one tail is usually supposed to be the distinguishing mark of a comet1 but in #aggd one appeared with six tails1 arranged something like a fan4 ,sometimes the tail is separated from the head4 ,of the actual consistency of comets we cannot give any lengthened details4 ,they apparently consist of elements similar to the meteors--namely1 of solid masses1 and have been supposed to be aggregations of meteors4 ,some appear at regular intervals1 and their approach can be determined with accuracy4 ,of course we only see those which are attracted by the sun1 or those which revolve in the solar system4 ,there must be thousands of other comets which we never see at all4 ,the diagram 7fig4 #edj in the next page7 represents a portion of the path of the comet of #afhj4 ,this visitor pursued its course for two months at a velocity of #hjj1jjj miles an hour4 ,the tail was estimated to extend #abc1jjj1jjj of miles1 and a length of #fj1jjj1jjj of miles was emitted in two days4 ,when this great comet was approaching the sun1 or its perihelion1 as such approach is termed1 three minutes more would have seen it rush into the orb had its enormous pace been slackened1 but as it was proceeding so rapidly1 and being just then #add1jjj miles away1 it escaped4 ,we can scarcely estimate the results of such a collision4 ,this comet appeared ,b4,c4 #cd1 and again at intervals of about #ege years4 ,it may be expected in #bbee4 ,it is to ,halley that the discovery of the elliptical orbits of comets is due4 ,m4 ,biela's comet was the cause of much anxiety in #ahcb1 for a collision with the earth was apprehended4 ,fortunately a month intervened between the period at which the comet was expected at a certain place in the system and the earth's arrival at that spot1 so1 as it happened1 about #fj1jjj1jjj of miles intervened4 ,we cannot say what the exact effect of such a collision would be1 but some wonderful atmospheric phenomena and increased temperature would certainly result from the contact4 ,now the comet is supposed to have an effect upon the vintage1 as 8comet0 wines are regarded with much favour4 ,if comets1 as is believed1 do consist partly of solid particles1 a collision might be unpleasant2 but the weight is1 as a rule1 a mere nothing compared to their vapoury volume1 which is enormous4 ,that the tails must be of a very attenuated medium is evident1 as we can see the stars through them1 and we know that a very thin cloud will obscure a star4 ,the 8menacing0 comet1 mentioned in the ,spectator ,february #ahha1 will not do much damage1 so the scare was needless1 as ,mr4 ,proctor has explained4 ,illustration3 ,fig4 #eci4--,path of ,biela's ,comet4 ,illustration3 ,fig4 #edj4--,path of comet1 #afhj4 ,,aerolites1 or 8,meteorites10 are falling bodies 7meteors71 which reach the earth in solid form4 ,the greater mass of falling stars are burnt up ere they reach us1 or are dissipated in space4 ,but many instances of aerolites descending might be adduced4 ,they usually consist of metals1 such as iron and nickel mixed with sulphur1 magnesia1 and silica4 ,the theory concerning falling stars has been already mentioned4 ,illustration3 ,fig4 #eda4--,the heavens as seen from ,saturn4 ,we have thus far taken a brief general view of the solar system1 with a few of the phenomena of the heavens4 ,our next step will be to consider the sun1 the planets1 and the asteroids1 according to the order of magnitude4 ,the asteroids we cannot consider separately1 but the sun1 moon1 earth1 and the principal planets will yield us much interesting information as we examine them more closely4 ,we shall then1 as far as possible1 look into the domain of the fixed stars1 constellations1 and the nebul1 commenting1 as we proceed1 upon the varied celestial and terrestrial phenomena connected with the movements of the heavenly bodies4 ,as is due to the great centre of our system1 we will commence with the ,,sun4 ,but before proceeding to do so1 we must say a few words about the motion of the heavenly bodies--that is1 the apparent motion of the rising and setting of the sun and stars4 ,the attentive observation of the starry heavens1 even during a single night1 will convince us that all the visible stars describe circles which are the smaller1 the nearer the stars are to a certain point of the heavens1 ,p 7fig4 #edb74 ,in close proximity to this point there is a tolerably bright star1 called the ,pole ,star1 which has scarcely any motion1 but appears to the eye as always occupying the same position4 ,hence a line1 ,,pp1 drawn from this star1 through the centre of the earth1 c1 represents the axis around which all the heavenly bodies perform their apparent motions4 ,the part of the celestial axis1 ,,pp1 passing through the earth1 is the earth's axis2 the north pole1 of which p is on the same side as the pole star1 and the south pole1 p1 is on the opposite side4 ,illustration3 ,fig4 #edb4--;,celestial axis4 ,we have1 therefore1 by the aid of the stars1 determined the position of the earth's axis1 and by this latter we can assign to the equator its proper place4 ,for if pp be the earth's axis1 aq is the greatest circle drawn round the earth1 equally distant from both poles1 and the plane of which cuts the earth's axis at right angles4 ,furthermore1 let us suppose the plane of the equator to be extended till it reach the celestial concave2 we thus find the place of the celestial equator1 ,a ,q1 or equinoctial1 as it is generally termed in opposition to the equator1 which always means the terrestrial equator4 ,the equinoctial divides the heavens into the northern and southern hemispheres4 ,we cannot actually describe the equinoctial and make it visible1 but we can imagine its line of direction by observing those stars through which it passes4 ,we are now in a condition to assign to an observer different stations in relation to the earth's axis on the earth's surface1 which will essentially modify the aspects under which celestial phenomena are represented4 ,one of these stations may be supposed to be at one of the two poles1 for example1 at p1 or at any one point of the equator1 as at a1 or1 finally1 on any portion of the surface of the earth which lies between the pole and the equator1 as1 for example1 o4 ,illustration3 ,fig #edc4--;,great ,nebul in ,orion4 ,,chapter ,,xxxvi ,,the ,,sun4 ,,motion ,,of ,,the ,,sun--,,the ,,seasons--,,character ,,of ,,the ,,sun--,,sunspots--,,zodiacal ,,light4 ,suppose that we rise early in the morning we shall1 as the reader will say see the sun rise--that is1 he appears to us to rise as the earth rotates4 ,by the accompanying diagram 7fig4 #edd7 we can understand how ,sol makes his appearance1 and how he comes up again2 not1 it will be observed1 after the manner stated by the ,irishman1 who declared that the sun 8went down1 and ran round during the night when nobody was looking40 ,the earth rotates from west to east1 and so the sun appears to move from east to west4 ,if we look at the diagram we shall see that after rising at ,o1 the sun advances towards the meridian in an oblique arc to ,a1 the highest or culminating point--midday4 ,he then returns1 descending to ,w2 this path is the diurnal arc4 ,at ,q similarly1 during his passage in the nocturnal arc1 he reaches the lowest or inferior culmination4 ,,hh is the meridian4 ,illustration3 ,fig4 #edd4--,sun's motion4 ,illustration3 ,fig4 #ede4--,the ecliptic4 ,on the #bast of ,march1 this path brings the sun on the 8 equinoctial0 line mentioned at the close of the last chapter4 ,day and night are then of equal duration as the arcs are equal4 ,so this is the ,vernal 7or spring7 ,equinox4 ,some weeks after the sun is at midday higher up at ,s1 so the diurnal arc being longer1 the day is longer1 7,z is the zenith1 ,z is the nadir1 ,p ,p is the celestial axis74 ,from that time he descends again towards the equinoctial to the autumnal equinox1 and so on1 the diurnal arc becoming smaller and smaller until the winter solstice is reached 7,s74 ,from what has been previously said1 it is evident that the sun has a twofold apparent motion--viz41 a circular motion obliquely ascending from the horizon1 which is explained by the rotation of the earth1 and by our position1 o1 to the earth's axis1 ,p ,p1 and also by a rising and setting motion between the solstitial points1 ,s and ,s1 which causes the inequality of the days and nights4 ,independently of the daily motion of the sun1 we observe that at the summer solstice1 on the #bast of ,june1 at midday1 the sun is at ,s1 and one half year later--viz41 on the #bast of ,december1 at midnight1 the sun is at s1 from which he arrives again in the space of half a year at ,s2 so we are able to represent this annual motion of the sun by a circle1 the diameter of which is the line1 ,s s4 ,this circle is called the ,ecliptic4 ,the plane of the ecliptic1 ,s s1 cuts the plane of the equinoctial1 ,a ,q1 at an angle of #bc1 and the axis of the ecliptic1 ,s s1 makes the same angle with the axis of the heavens1 ,p ,p4 ,the two parallel circles1 ,s s and ,s s1 include a zone extending to both sides of the equinoctial1 and beyond which the sun never passes4 ,these circles are called the ,tropics1 from 1 ,i turn1 because the sun turns back at these points1 and again approaches the equinoctial4 ,the parallel circles1 ,s s1 and ,s s1 described by the poles of the ecliptic1 ,s s1 about the celestial poles1 ,p ,p1 are called the arctic and antarctic circles4 ,whenever the sun crosses the equinoctial1 there is the equinox2 but the points of intersection are not invariably the same every year4 ,there is a gradual westerly movement1 so it is a little behind its former crossing place every year4 7,see diagram1 fig4 #edg47 ,illustration3 ,fig4 #edf4--,the ,seasons4 ,this is the 8,precession of the ,equinoxes10 because the time of the equinoxes is hastened1 but it is really a retrograde movement4 ,hipparchus discovered this motion1 which amounts to about fifty seconds in a year4 ,so the whole revolution will be completed in about #bh1jjj years4 ,illustration3 ,fig4 #edg4--,precession of ,equinoxes4 ,it is obvious1 then1 that the sun is the most important star in the universe2 and when we come to speak about the earth we shall consider the seasons1 etc41 more fully4 ,now we must endeavour to explain what the sun is like1 and this can only be done with specially darkened glasses1 for a look at the sun through an ordinary telescope may result in great1 if not permanent1 injury to the eye4 ,the sun is not solid so far as we can tell4 ,it is a mass of 8white-hot0 vapour1 and is enabled to shine by reason of its own light1 which the planets and stars cannot do2 they shine only by the sun's reflected light4 ,so we may conclude the sun to be entirely gaseous1 but1 thanks to the recent researches in spectrum analysis 7already explained71 by which the light of the sun has been examined by means of the spectroscope1 and split up into its component colours1 ,mr4 ,lockyer and other scientists have discovered that a number of elements 7metals7 exist in the sun in a fused1 or rather vapourous state1 in consequence of the intense heat4 ,hydrogen exists in the sun1 with other gases unknown to us here1 and many metals1 discovered by their spectra1 which are the same under similar circumstances4 ,the sun is supposed to be spherical in shape1--not like the earth1 flattened at the poles1--and to be composed of materials similar to what the earth is composed of1 and what it would be if it were as hot as the sun is4 ,thus we can argue by analogy from the spectra of earthly elements1 that1 as the sun and star light gives us similar spectra1 the heavenly bodies are composed of the same elements as our globe4 ,we can thus form our opinion of the sun's constitution4 ,mr4 ,neisen says3-- 8,with the aid1 therefore1 of the additional information given us by the spectroscope1 it is not very difficult to form a true idea of the probable condition of the surface of the sun1 which is all that we can see4 ,it is the upper-lying strata of a very dense atmosphere of very high temperature--an atmosphere agitated by storms1 whirlwinds1 and cyclones of all kinds1 traversed by innumerable currents1 and now and then broken by violent explosions4 ,above the brilliant surface which we see is a less dense and somewhat cooler upper stratum1 which1 though hot enough to shine quite brightly1 is quite invisible in the presence of the brighter strata beneath it40 ,illustration3 ,fig4 #edh4--,sun spots4 ,,sun ,,spots1 as they are generally called1 are hollows in the sun's vapoury substance1 and are of enormous extent2 and there are brilliant places near those spots1 which are termed facul4 ,these spots have been observed to be changing continuously1 and passing from east to west across the sun1 and then to come again at the east to go over the same space again4 ,now this fact has proved that the sun turns round upon his axis1 and although he does not move as we imagine1 from east to west1 round the earth1 the orb does move--in fact1 the sun has three motions3 one on his axis2 secondly1 a motion about the centre of gravity of the solar system1 and a progressive movement towards the planet ,hercules4 ,if we examine the surface of the sun through a proper telescope1 we shall find that the even surface we can plainly distinguish at sunset is marked1 and the brightness is greater towards the centre of the orb4 ,we can perceive various irregularities2 we shall find spots1 facul 7little torches71 etc4 ,these spots were discovered by ,galileo and other astronomers1 and were1 as we have stated1 found to be surface markings1 and not a series of bodies passing between the earth and the sun4 ,the rotation of the sun was measured1 and it was found that the orb revolved in about #be days1 and in such a manner as to be slightly inclined to the plane of the ecliptic4 ,herschel observed a spot at least #ej1jjj miles in diameter1 which is more than six times the diameter of the earth4 ,the sun spots are observed to be constantly changing1 and are naturally observed differently as the revolution proceeds4 ,the dark pole1 or 8nucleus0 7umbra71 as it is called1 is surrounded by a less dark surface called the penumbra1 but the umbra is not really dark2 it is extremely bright when viewed alone1 as has been proved by ,professor ,langley1 while the heat is even greater in proportion4 ,but the umbra of a sun spot must be below the level of the penumbra1 for the shape changed as the sun revolved on its axis4 ,the penumbra was wider on the side nearest the edge of the solar disc1 and the umbra may be due to the uprushing or downpouring of gas or vapour like 8whirlpools in the solar atmosphere40 ,near the sun spots the long streaks1 or facul1 are often observed by the borders of the disc1 and a transition of the luminous part of the photosphere#bf into darkness has been observed1 and bright bridges crossing the spots1 and then gradually getting dark1 were seen by ,m4 ,chacomac4 ,the sun spots vary in direction1 but the same general course is continued4 ,sometimes they describe curves1 sometimes lines4 ,illustration3 ,fig4 #edi4--;,direction of sun spots4 ,during solar eclipses the sun exhibits what are termed 8red prominences10 which are the luminous vapours existing around the sun4 ,when the orb is eclipsed1 we can see the bright-coloured vapours shooting out from underneath the dark shadow1 and this light is termed the 8coronal atmosphere02 the vapours are called the sun's chromosphere4 ,in the coronal atmosphere are certain curious shapes of vapour thrown up1 and frequently changing1--projecting1 in fact1 from the gaseous envelope4 ,these red prominences were first observed in #ahdb1 and in #ahea it was proved that they appertained to the sun1 for the moon hid them as the eclipse began4 ,before the prominences were discovered1 the red light surrounding the solar disc was known1 and called the 8sierra0 7now chromosphere71 or chromatosphere4 8,the luminosity of these prominences is intense10 says ,secchi1 8and they rise often to a height of #hj1jjj miles1 and occasionally to more than twice that2 then bending back1 they fall again upon the sun like the jets of our fountains4 ,then they spread into figures resembling gigantic trees1 more or less rich in branches40 ,we give some illustrations of the appearances of these prominences4 ,illustration3 ,fig4 #eej4--,solar prominences4 ,the zodiacal light is often observed4 ,it is a glow1 and frequently of a rosy tint4 ,it may be seen in ,england in ,march or ,april before sunset1 or in the autumn before sunrise2 and it is doubtful whether it be a terrestrial or an extra-terrestrial light--a lens-shaped object surrounding the sun4 ,some philosophers maintain that the light is caused by multitudes of minute bodies travelling round the sun2 but ,herr ,gronemann has lately fully discussed the observations1 and the drift of his contention is under stated3-- ,illustration3 ,fig4 #eea4--,solar prominences4 ,there are valid observations against two items in the support of the old theory--viz41 the affirmed connection of the evening and morning cones seen on the same night 7if the corresponding sides be prolonged71 and the participation of the cones in the daily motion of the heavens4 ,the zodiacal light is sometimes seen when daylight has not yet disappeared2 and1 on the other hand1 it sometimes fails to appear1 though there is complete darkness4 ,there would seem to be a real lengthening and shortening4 ,it has been observed by ,schiaparelli1 that the light is much more difficult to make out when it passes through the meridian1 than when it is only #cj above the horizon1 and is less easily seen when the air is clearest than when a sort of mist is present4 ,indeed1 the bright parts of the ,milky ,way may be seen to be weakened by mist1 while the zodiacal light at the same height is unaffected4 ,the zodiacal light has temporary variations of light intensity1 and it shows from time to time remarkable changes of form and position1 so sudden and short as to be hard to explain on the planetary hypothesis4 ,the elongations of the cones show a half-yearly period1 which is independent of the transparency of the air4 ,the cone follows the observer northwards or southwards1 so that there is no parallactic action2 and this peculiarity 7so adverse to the extra-terrestrial hypothesis7 cannot be explained by reflection or absorption of light4 ,as to spectroscopic observations1 the author finds 7#a7 that the zodiacal light consists partly of proper light2 7#b7 that its connection with polar light is but secondary1 temporary1 and accidental2 7#c7 that the cause of the second phenomenon is such that it may strengthen the zodiacal light and modify its spectrum2 and 7#d7 that the results of spectrum analysis rank with other arguments tending to find the source of the zodiacal light in the neighbourhood of the earth 7like the polar light74 ,herr ,gronemann1 then1 thinks the zodiacal light a terrestrial phenomenon1 though he will not say that it cannot be influenced by cosmic action4 ,he throws out the suggestion that the cone may be a kind of optical illusion1 arising from some fine matter--gas or dust--being more accumulated near the observer in one direction than another4 ,the apparent length of the cone might be conditioned by the conical shadow of the earth1 and the changes of length be due to cosmic and electric influences4 ,in any case1 there is need of a more scientific theory than the old one4 ,illustration3 ,fig4 #eeb4--,on the sun's disc4 ,we may conclude our brief notice of the great luminary to which we are indebted for everything1 by a resum of his distance from us1 his diameter1 and a few other plain facts and figures4 ,in the first place the actual distance of the sun from the earth has never accurately been determined1 but perhaps the next transit of ,venus will assist the observers to a nearer estimate4 ,it is quite sufficient for our purpose1 however1 to state that the sun's distance from the earth is #ib1jjj1jjj of miles4 ,the distance varies in winter and summer4 ,in the former period the sun is nearer than in summer1 and yet as the rays strike over us1 and pass us1 as it were1 we feel less heat4 ,when1 as in summer1 we are more in the focus of the rays1 we feel the greater heat4 ,we have already spoken of parallax1 and it is by finding the solar parallax that the distance of the sun from us is found4 ,this parallax has not been exactly ascertained1 or rather authorities differ1 and as difference of #jja in the solar parallax means something over #ajj1jjj miles of distance1 it is evident that exactness is almost impossible4 ,if #hhj be settled as the solar parallax1 #ib1hhj1jjj miles is the distance of the sun from the earth4 ,if #hhh be taken we have nearly #ib1jjj1jjj exactly4 ,the volume of the sun is #a1bec1jjj times that of the earth1 and yet the density of the former is only about one-fourth of the latter1 so the attraction of gravitation at the sun must be more than that of the earth's surface twenty-seven times4 ,a body dropped near the surface of the sun would fall #dcf feet in the first second1 and have attained a velocity of ten miles a minute at the end of the first second4 ,the diameter of the sun depends in our calculations upon its distance from the earth4 ,if we suppose that to be #ib1hhj1jjj miles1 the diameter is #hff1jjj miles4 ,if we take #ia1jjj1jjj of miles as the distance from the earth the diameter is #hej1dfg miles4 ,the sun makes 7apparently7 the circuit of the heavens in #cfe days1 #f hours1 #i minutes1 and #if seconds2 the transit from one vernal equinox to the next being only #cfe days1 #e hours1 #dh minutes1 #dhf seconds1 owing to the precession of the equinoxes already mentioned4 ,when we consider the power and grandeur of the sun we may well feel lost in the contemplation4 ,the sun balances the planets and keeps them in their orbits4 ,he gives us the light and heat we enjoy1 and coal-gas is merely 8bottled-up sunlight40 ,in darkness nothing will come to maturity4 ,we obtain rain and dew owing to the sun's evaporative power2 and no action could go on upon earth without the sun2 and yet we receive only about #a_/bjgjfejjjj part of its heat and light4 ,as to the colour of the sun1 ,professor ,langley states that it is really blue1 and not the white disc we see4 ,the whiteness is due to the effect of absorption exerted by the vapourous metallic atmosphere surrounding our luminary2 and if that atmosphere were removed1 his colour would change4 ,,footnotes3 #bf ,the bright part of the sun4 ,,chapter ,,xxxvii4 ,,the ,,earth4 ,,form ,,of ,,the ,,earth--,,motion ,,of ,,the ,,globe--,,rate ,,and ,,manner ,,of ,,progression--,,latitude ,,and ,,longitude--,,the ,,seasons4 ,we have learnt from our books on ,geography that the earth is shaped like an orange1--that is1 our globe is round and flattened slightly at the 8poles10 and we can easily see that the earth curves away1 if we only try the experiment mentioned in a foregoing chapter--viz41 how far a person standing 7or lying7 on the ground can see on a level4 ,our power of eyesight is not limited to three or four miles1 but a man of ordinary height standing on the plain cannot see more than three miles1 because the earth is curving away from him4 ,we know that at the seaside we can see ships gradually appear and disappear4 ,when approaching us the masts and top-sails appear first1 then the main-sails1 and then the ship itself4 ,a sailor climbing up the mast can see farther than the captain on deck1 because he can see over the curve1 as it were4 ,when the vessel is at a considerable distance we see her 8hull down0 as it is termed1--that is1 only her sails are visible to us1 and at last they disappear also4 ,if we want any other proof that the earth is round we can see when an eclipse takes place that the shadow on the moon is circular4 ,so we may be certain of one fact2 the earth is round1 it is a globe4 ,so much for the rotundity of the earth4 ,but the earth appears to us1 except in very mountainous districts1 as being almost a plane4 ,this is because of its extent2 and even from very high mountains we can only see a very small portion of the earth1 and so1 on a globe sixteen inches in diameter1 the highest hills would be only about #a_/ajj of an inch1 like a grain of sand4 ,the motion of the earth is known to most people1 though as everything upon the globe passes with it1 and a relative fixity is apparent1 this is1 of course1 not real rest4 ,the earth is moving from west to east at a tremendous rate1--viz41 nearly nineteen miles a second6 ,we think a train at sixty miles an hour a fast train2 but what should we think of an express going more than #fh1jjj miles an hour6 ,yet this is about the rate at which our globe whirls around the sun4 ,her fastest pace is really #ahe miles a second2 the least about one mile per second less4 ,that is one motion of the earth2 the other is its motion on its axis4 ,if we send a skittle ball rolling we perceive it turns round as it proceeds4 ,so the earth rotates on its axis1 ,n ,s1 in the accompanying diagram2 the extremities of the axis are called the poles4 ,the line in the middle is the equator1 which is divided into #cfj equal parts1 each being #fi-a_/aj miles in length2 so there are #ahj lines1 or rings1 drawn upon the globe from ,n to ,s1 and these are meridians4 ,in ,england the degrees are calculated from the ,greenwich meridian4 ,we can thus obtain the distance of localities east or west1 as we may briefly show 7fig4 #eed74 ,illustration3 ,fig4 #eec4--;,evidence of the spherical form of the earth4 ,illustration3 ,fig4 #eed4--,latitude and ,longitude4 ,the distance of any meridian from the first meridian is termed the longitude1 and it is employed in describing the situation of a place on the earth's surface4 ,suppose ,l 7fig4 #eed7 a city1 its longitude will be #cj1 since it lies on a meridian which is #cj from the first4 ,so1 for example1 the longitude of ,oporto is #h #cg west1 ,paris #b #bb east1 ,vienna #af #af east1 ,bagdad #dd #de east1 reckoned from the meridian of ,greenwich1 and so on4 ,at the #ahjth degree we have proceeded half round the globe1 and reached the farthest distance from the first meridian1 and are now on the opposite side of the earth1 and proceeding in a similar manner in the opposite direction we get west longitude4 ,it will readily be perceived that a knowledge of the longitude alone is not sufficient to determine the situation of a place on the earth's surface4 ,when we say1 for example1 that the longitude of a place is #cj1 it may lie on any point whatever of the line1 ,n ,l ,s1 on the whole hemisphere 7fig4 #eed74 ,this point must therefore be determined more accurately1 and hence the first meridian is divided into #ij equal parts north and south of the equator towards the poles4 ,these are called degrees of latitude1 and the lines drawn through these round the globe1 parallel to the equator1 are called circles or parallels of latitude1 and diminish as they approach the poles4 ,hence1 by the latitude of a place we mean its distance from the equator towards the poles1 and we speak of north and south latitude according as the place is situated in the northern or southern hemisphere4 ,so1 for example1 the point ,l 7fig4 #eed71 which has #cj longitude and #fj ,n4 latitude is in ,sweden4 ,the latitude is also observable by ascertaining the altitude of the polar star above the horizon when in the northern hemisphere4 ,the longitude is found by the chronometer2 for if we know the time at ,greenwich we can calculate how far we are east or west of it by seeing whether the local time be an hour 7say7 earlier or later1 and that difference shows we are #ae to the east or the west as the case may be4 ,the earth's rotation1 according to sidereal time1 is less than solar time1 as we have seen1 so we have #cfe solar days and #cff sidereal days2 so a person going round the world gains or loses a day as he travels east or west according to his reckoning1 as compared with the reckoning of his friends at home4 ,we can easily ascertain the earth's motion by watching the stars rise and set4 ,now the path in which the earth moves is called an ellipse1--very nearly a circle1--but it does not always move at the same rate exactly4 ,we will now look at the relations of the sun and the earth4 ,let us take an example4 ,suppose we have a rod1 at each end of which we fix a ball 7see diagram71 and let one ball be three times as large as the other1 the common centre of gravity will be at c1 at one quarter of the distance between the centres1 and there the bodies will be in equilibrium4 ,if these masses be set spinning into space they will revolve at that distance from each other1 the attraction of gravitation and the force in opposition to it equalizing each other4 ,illustration3 ,fig4 #eee4--;,earth and ,sun4 ,the earth1 as we know1 proceeds with a tremendous force around the sun1 not in a circle1 remember1 but in an ellipse or oval track1 from which it never moves year by year in any appreciable degree4 ,now what prevents this earth of ours from rushing off by itself into space8 ,why should not the earth fly away in a direct line8 ,the reason is because the sun holds it back4 ,the force of the sun's gravitation is just sufficient1 or we may say so enormously great1 that it suffices to retain our globe and all the other planets in their various orbits at the very same distance1 and to counteract the force which launches them through space4 ,therefore1 as we have already noticed when considering the sun1 it is to that ruler of the day that we are indebted for everything4 ,what would happen1 then1 if the earth were suddenly to increase her velocity1 or the sun to contract his mass8--,we should be flung into infinite space1 and in a short time would be frozen up completely4 ,our present diurnal course would probably proceed1 but all life and existence would cease as we whirled with distant planets through infinity4 ,suppose1 on the contrary1 we were to stop suddenly4 ,we have some of us read in a foregoing part of this volume that heat is the motion of molecules in ether1 and that when a body strikes another heat is developed by contact and friction4 ,if the earth were to be stopped suddenly1 8an amount of heat would be developed sufficient to raise the temperature of a globe of lead of the same size as the earth #chd1jjj of the ,centigrade thermometer4 ,the greater part1 if not the whole of our planet1 would be reduced to vapour01 as ,professor ,tyndall says4 ,illustration3 ,fig4 #eef4--,transit of earth across ,sun1 seen from ,mars4 ,in the diagram 7fig4 #edf1 on page #dig7 we shall at once find the explanation of the constantly-recurring seasons1 and the amount of our globe which is illuminated by the sun at various times4 ,it will be easily understood that the poles have six months day and six months night4 ,when the earth is at an equinox1 one half of the surface is illuminated and the other half in shade1 therefore the days and nights are equal4 ,but when the north pole turns more and more towards the sun1 the south pole is turning away from it in the same ratio1--the days and nights respectively are getting longer and longer1 and at the north and south poles day and night are continuous1 for the small spaces round the poles are1 during a certain period1 wholly in sunshine and shade respectively4 ,in ,march 7in the diagram1 fig4 #edf7 we see that exactly one half of the earth is illuminated1 and the other is darkened4 ,so in ,september1 when we have the opposite view4 ,in ,june the earth is more inclined apparently to the sun1 and more of the surface is exposed to it1 so the days are longer in some parts4 ,the opposite effect is visible in ,december4 ,the summer heat and winter cold are accounted for by the more or less direct force of the sun's rays1 for the more the angle of incidence is inclined the fewer rays reach the object2 and if the rays fall at an angle of #fj1 the heat is only half what it would be if they came vertically4 ,when the days are shortest the sun is lowest1 and therefore gives less heat to the earth at certain periods4 ,the wonderful precision which has adapted the position of the earth on its axis1 will be apparent from the illustration 7fig4 #eeg74 ,here we have a table and some bottles1 a candle to represent the sun1 and a ball of worsted and a knitting-needle to represent the earth and its axis4 ,suppose we place the ball in the position at a1 with its axis perpendicular to the plane of the orbit4 ,as the earth would turn and go round the sun in this supposed case1 we should find the days and nights equal1 and the sun would quickly scorch up the tropics1 and the other portions would have a never-changing spring or winter all the year for ever4 ,this would not be so pleasant1 for variety is the charm of nature1 and the salt of life4 ,so we may put a aside1 as the earth would be scarcely habitable under the supposed conditions1 and try b4 ,here we find the poles directed to the sun4 ,the whole northern hemisphere would thus be illuminated one half year1 and the southern similarly2 such rapid changes from heat to cold and back again would not suit us4 ,so we fall back upon c1 the actual appearance of the position of the earth1 and here we find all the most favourable circumstances existing for us4 ,this inclination gives rise to all the varied phenomena of the pleasant gradations of heat and cold1 summer and winter1 the charming changes of season1 and the wonderful results of the ever-recurring days and nights1 months and years1 as the earth spins round4 ,so we see that the sun does not really rise and set upon the earth2 the globe rotates1 and brings us into view of the sun1 and as we turn we lose his light4 ,illustration3 ,fig4 #eeg4--;,inclination of ,axis4 ,in the foregoing brief description we have learnt some few facts concerning our earth4 ,we have ascertained that the planet we inhabit is round2 we have also seen that the earth moves around the sun and around its own axis1 and also that it moves at a tremendous rate2 we know that that rate is just counterbalanced by the attraction of gravitation1 and the course round the sun gives us varying seasons1 day and night4 ,there are many subjects relating to the earth which will be more properly included under ,physical ,geography4 ,we may here just add the diameter of the earth1 and proceed to inquire concerning the moon4 ,the polar diameter of our globe is #g1hii miles2 the equatorial diameter #g1ibe miles4 ,it is distant from the moon #bch1ejj miles4 ,we will close this chapter with the letters and characters of the ,greek alphabet used in astronomical works to designate the stars4 ,alpha ,beta ,gamma ,delta ,epsilon ,zeta ,eta ,theta ,iota ,kappa ,lambda ,mu ,nu ,xi ,omicron ,pi ,rho ,sigma ,tau ,upsilon ,phi ,chi ,psi ,omega ,illustration3 ,fig4 #eeh4--;,a ship disappearing below the horizon4 ,,chapter ,,xxxviii4 ,,the ,,moon4 ,,what ,,is ,,it ,,like8--,,moon ,,superstitions--,,description ,,of ,,the ,,moon--,,phases--,,tides--,,eclipses4 ,from the early days of childhood every man and woman has been familiar with the moon4 ,this satellite of earth has been domesticated1 so to speak1 amongst us2 and while the sun and other stars have been glorified in poetic and prose effusions1 the moon has been always more tenderly addressed4 ,the soft 7reflected7 light of our attendant moon is much more attractive than the brilliancy of the greater light 8that rules the day40 ,the moon is regarded as our particular property1 and has awakened an interest in our minds since the time that we could1 as we fancied1 see the 8,man in the ,moon40 ,illustration3 ,fig4 #eei4--,the earth as seen from the moon4 ,in ancient times the moon was supposed to possess some light of her own1 and to be inhabited by immense creatures2 and various theories continued to be promulgated respecting her1 until the telescope came into use1 and then astronomers began to find out many new things concerning ,luna4 ,now1 what has the telescope told us regarding our moon8--,it shows us that there are mountains and craters1 and numerous traces of volcanic action4 ,at one time it was supposed that the dark masses apparent in the surface of the moon1 and which can easily be distinguished by the naked eye1 were seas1 and maps of the moon were made1 marking continents and craters4 ,if it were possible to reach the moon1 as ,m4 ,jules ,verne's travellers did1 we should find a very irregular and corrugated surface--plains and mountains without water4 ,we should be able to see the stars in the daytime1 because there is no atmosphere around the moon1 and there is a silence that 8might be felt40 ,the appearance of our earth from the moon1 and the beauty of the stars in the unclouded and waterless space around the satellite1 must be very grand1 and has been1 in a measure1 depicted in the illustration 7fig4 #eei7 on the opposite page4 ,illustration3 ,fig4 #efj4--,the ,moon3 the ring plain ,copernicus4 ,in this illustration 7fig4 #efj7 we have some idea what the moon is like4 ,we see the rugged and cratered appearance of the disc2 it is a desert waste1 so far as we can ascertain1 without inhabitants1 and1 in all probability1 without vegetation4 ,for there being no moisture amongst the plains and craters and mountains of our satellite1 we must conclude that the moon is dead4 ,it is a very interesting1--nay1 a fascinating study4 ,when we take up our telescope and look from the window at the heavens the most beautiful object within our small telescopic vision is the moon shining like a silver plate1 and we wonder what is up there4 ,with a small telescope even we can discern many interesting features in the moon at the full1 which will assist us in verifying the diagrams in books and their explanations4 ,as the moon is only a few miles away1 comparatively speaking1 and as the large telescopes now in use bring us within a measurable distance of the surface1 we are enabled to speak more positively about our changeable satellite than of any of the planets4 ,when we look steadily at the full moon we perceive upon its surface dark and light tracts called 8seas10 though they are dried up now4 ,thus we hear of the 8,sea of ,serenity10 the 8,sea of ,storms10 and the 8,sea of ,tranquillity02 and in the map upon a subsequent page you may see the names of the seas1 mountains1 and the general formations of the surface of the moon4 ,maps of the moon are now to be procured1 though no personal visits can be made to the satellite4 ,it is very interesting to observe or to read about the structure of the moon1 for we may thus learn how similar the earth and her attendant are in formation2 but one important agency--that of water--has made a considerable difference in the appearance of the formations4 ,in the moon we have mountains1 plains1 and rugged craters2 the surface is not level1 because the sunlight is visible sooner at some points than others4 ,the chief mountain chain is the ,apennines1 and has a great elevation2 many traces of volcanic agency are discoverable amid the great desolation1 and awful silence reigns throughout4 ,illustration3 ,fig4 #efa4--,telescopic appearance of the ,moon4 ,as is well known1 water has a great erosive power1 and its action disintegrates the surface of the earth with rapid persistency4 ,so the physical appearance of the globe has become much changed in the course of ages3 ravines exist where plains used to extend1 and rivers cut their way through deep gorges to the sea4 ,the sands and other deposits are overlaid1 and thus the whole outward appearance has been altered4 ,not so the moon4 ,with a very attenuated atmosphere without clouds or rain1 there is no moisture1 no lake1 no water in the moon now4 ,what may have been we can only conjecture4 ,if there ever have been lakes or seas they have all been absorbed4 ,illustration3 ,fig4 #efb4--;,formations near ,mostig4 ,low power4 ,the heat upon one side of the moon must be very great at one period1 and the cold on the opposite side intense1 as one would think--yet upon this fact authorities differ somewhat4 ,if the moon possess no atmosphere of any kind it would be fearfully cold and extremely hot at intervals1 but a surrounding medium1 even of very little density1 would modify the extremes2 and while we must accept the fact that the temperature varies very much we need not place it above #ajj of heat1 nor below #bj of cold4 ,so from close observation and comparison we are enabled to form a very fair opinion of the 8past0 of the moon1 and to ascertain that the same forces of nature which have moulded the planet we inhabit1 have been at work in the moon also4 ,when we study 8,selenography10 therefore1 we shall find a record of a history which may some day bear a parallel to the history of our physical world4 ,illustration3 ,fig4 #efc4--,the ring-plain ,copernicus1 as seen with small magnifying power4 ,the moon1 as all are aware1 moves round the earth attendant upon us1 but entirely under the control of the sun2 our satellite1 moreover1 has been the subject of many superstitions4 ,a great many rites and even domestic actions--such as the killing of fowls--were regulated by the moon2 and in ,scotland1 ,scandinavia1 and other portions of ,europe1 she has always been regarded as effecting destiny4 ,there are many interesting myths connected with the moon1 and indeed with astronomy generally1 and from a volume entitled 8,notes on ,unnatural ,history10 some very amusing extracts might be made4 ,it will not be out of place to mention a few of these myths4 ,illustration3 ,fig4 #efd4--,the walled-plain ,plato4 ,the ,chinese have an idea that a rabbit exists in the moon1 and is the cause of the shadows we see4 ,the ,buddhists think a holy hare is up there4 ,in the ,pacific ,islands there is a belief of a woman in the moon2 she was sent there because she wished her child to have a bit of it to eat2 and ,mr4 ,buchanan has versified the old ,scandinavian myth about the two children kidnapped by the moon as they returned from a well with a bucket of water slung upon a pole4 ,the ,jews placed ,jacob in the moon1 and the ,italians say that ,cain inhabits the luminary with a dog and a thorn bush4 ,in the ,inferno of ,dante this is referred to1 and we know that in ,a ,midsummer ,night's ,dream we have the moon coming out to shine upon the loves of ,pyramus and ,thisbe with the dog and the thorn-bush2 and in the ,tempest the same idea is mentioned by ,caliban4 ,readers of ,longfellow will recall the lines how 8the good ,nokomis answered0 ,hiawatha1 who asked about the moon-- 8,once a warrior1 very angry1 ,seized his grandmother1 and threw her ,up into the sky at midnight4 ,right against the moon he threw her1 #8,tis her body that you see there40 ,but modern scientific research has exploded all these charming old myths1 and laid bare the facts for us4 ,we must now resume4 ,illustration3 ,fig4 #efe4--,map of ,moon showing principal formations4 ,a ,mare ,crisium4 ,b ,palus ,somnii4 ,c ,mare ,serenitatis4 ,d ,mare ,tranquillitatis4 ,e ,mare ,fcunditatis4 ,f ,mare ,nectaris4 ,g ,sinus ,medii4 ,h ,mare ,vaporum4 ,i ,lacus ,mortis4 ,j ,mare ,frigoris4 ,k ,mare ,imbrium4 ,l ,oceanus ,procellarum4 ,m ,mare ,humorum4 ,n ,mare ,nubium4 ,o ,sinus ,iridium4 a ,apennine ,mts4 b ,caucasus4 c ,carpathians4 d ,pyrenees4 e ,altai ,mts4 f ,riphaen ,mts4 g ,doerfel ,mts4 h ,leibnitz ,mts4 i ,corderillas4 j ,d',alembert ,mts4 k ,taurus ,mts4 l ,hmus ,mts4 m ,alps4 #a ,clavius4 #b ,maginus4 #c ,maurolycus4 #d ,stfler4 #e ,tycho4 #f ,longomontanus4 #g ,wilhelm ,i4 #h ,schiller4 #i ,schickhardt4 #aj ,hainzel4 #aa ,furnerius4 #ab ,metius4 #ac ,fabricius4 #ad ,riccius4 #ae ,piccolomini4 #af ,zagut4 #ag ,apianus4 #ah ,walter4 #ai ,hell4 #bj ,pitatus4 #ba ,hesiodus4 #bb ,capuanus4 #bc ,ramsden4 #bd ,vieta4 #be ,petavius4 #be ,vendelinus4 #bg ,langrenus4 #bh ,fracastorius4 #bi ,theophilus4 #cj ,cyrillus4 #ca ,catharina4 #cb ,sacrobosco4 #cc ,almanon4 #cd ,albufeda4 #ce ,albategnius4 #cf ,hipparchus4 #cg ,ptolemy4 #ch ,alphonsus4 #ci ,purbach4 #dj ,regiomontanus4 #da ,thebit4 #db ,arzachel4 #dc ,bullialdus4 #dd ,lalande4 #de ,msting4 #df ,herschel4 #dg ,gassendi4 #dh ,mersenius4 #di ,sirsalis4 #ej ,grimaldi4 #ea ,riccioli4 #eb ,hevelius4 #ec ,condorcet4 #ed ,taruntius4 #ee ,proclus4 #ef ,cleomedes4 #eg ,romer4 #eh ,posidonius4 #ei ,plinius4 #fj ,julius ,csar4 #fa ,manilius4 #fb ,godin4 #fc ,agrippa4 #fd ,triesnecker4 #fe ,bode4 #ff ,gambart4 #fg ,eratosthenes4 #fh ,copernicus4 #fi ,reinhold4 #gj ,landsberg4 #ga ,encke4 #gb ,kepler4 #gc ,marius4 #gd ,archimedes4 #ge ,timocharis4 #gf ,euler4 #gg ,aristarchus4 #gh ,herodotus4 #gi ,struve4 #hj ,messala4 #ha ,mare ,humboldtanius4 #hb ,atlas4 #hc ,hercules4 #hd ,endymion4 #he ,eudoxus4 #hf ,aristoteles4 #hg ,linne4 #hh ,autolycus4 #hi ,aristillus4 #ij ,cassini4 #ia ,plato4 #ib ,helicon4 #ic ,pythagoras4 ,the moon moves around us in #bg;d #g;h #dcm #aadfas4 ,its diameter is about #b1afj miles1 and it is much less dense than our earth1 and so the force of gravity is less there than here4 ,its mean distance from us is #bch1hcc miles4 ,the moon goes through certain changes or phases every twenty-nine days or so2 and while rotating on its own axis our satellite goes round the earth1 so that we only see one side of the moon1 inasmuch as the two motions occupy almost exactly the same space of time4 ,so we generally see the same space of the moon1 though there is a slight variation at times4 ,this movement or swaying of the central point is called the moon's 8libration10 and is an optical effect1 due to the inequalities in the motion of the moon in its orbit1 and to the inclination of its equator and orbit to the ecliptic4 ,we append a map of the moon1 on which the mountains1 seas1 and craters can be perceived1 according to the list4 ,the hill ranges extend for hundreds of miles1 and the elevation reaches #cj1jjj feet1 and even more in places4 ,the so-called craters do not resemble volcanoes when viewed closely1 but take the form of basins or valleys surrounded by lofty hills4 ,one great plain called ,copernicus is more than fifty miles across4 ,respecting the appearance of the moon let us quote ,mr4 ,lockyer4 ,illustration3 ,fig4 #eff4--,the ,apennines and walled plain ,archimedes4 8,fancy a world without water1 and therefore without ice1 cloud1 rain1 snow2 without rivers or streams1 and therefore without vegetation to support animal life2--a world without twilight or any gradations between the fiercest sunshine and the blackest night2 a world also without sound1 for as sound is carried by the air1 the highest mountain on the airless moon might be riven by an earthquake inaudibly40 ,,phases ,,of ,,the ,,moon4 ,we have said that the moon revolves around the earth in the same time as she turns upon her own axis1 and always presents one side to us when she appears4 ,any one can ascertain this by putting a candle upon a round table1 and walk round it facing the candle4 ,the experimentalist will find that he will turn upon his own axis as well as turn around the table4 ,thus we shall see how the moon changes1 for to be as changeable as the moon is proverbial4 ,these different aspects or phases we shall now proceed to explain4 ,illustration3 ,fig4 #efg4--,phases of the ,moon4 ,the time intervening between one 8new0 moon and another is #bi;d1 #ab;h1 #ddm1 #bs1 and is termed a synodic revolution4 ,this is longer than the sidereal revolution1 because the earth is also moving in the same direction and the moon has to make up the time the earth has got on in front1 as it were4 ,so the moon travels nearly thirteen times round the earth while the latter is going round the sun4 ,the revolutions of the moon have been a measurement of time for ages1 and her varying appearances during lunation are always observed with interest4 ,the illustration 7fig4 #efg7 will assist us materially4 ,the sun's rays fall in a parallel direction upon the earth and moon1 and let us suppose that ,s is the sun in the diagram and ,t the earth2 ,c at the various points is the moon1 the capital letters1 ,a1 ,b1 ,c1 etc41 indicating the planet as she appears from the sun1 and the small letters show how she appears to us from the earth4 ,let us suppose that the sun1 earth1 and moon are in conjunction--or in a direct line4 ,the phases1 ,c and ,g1 are the moon's 8quadratures40 ,at ,a we see the sun shining on the moon1 but we only have the dark side4 ,it is then 8new0 moon2 but by degrees1 as she goes round in her orbit1 we perceive a small crescent-shaped portion1 lighted up by the sun at ,b and b4 ,at c we have the first quarter or half-moon4 ,when she is in opposition she is at full moon1 and so on to the last quarter and conjunction again4 ,illustration3 ,fig4 #efh4--;,crescent ,moon4 ,the moon's phases may be easily shown by means of a medium-sized lamp to represent the earth1 a smaller one to serve as moon1 and a light to act as sun all at the same height4 ,colour the 8lunar0 globe white1 and if we move it about the 8earth0 globe1 we shall see the various phases of the moon in the sharp shadows4 ,,the ,,tides4 ,the ebb and flow of our tidal waters depend upon the moon to a great extent4 ,the phenomenon is so common1 that we need only refer to it1 but the cause of the tides may be stated4 ,twice every day we have the tides twelve hours apart1 and the flow and ebb are merely examples of the attraction of gravitation1 which is exercised upon all bodies1 either liquid or solid4 ,the tides are highest at the equator and lowest at the poles1 because the tropics are more exposed to the influence of the lunar attraction4 ,illustration3 ,fig4 #efi4--,moon's attraction4 ,by the small diagram 7fig4 #efi7 we shall be able to see in a moment how the moon acts4 ,the moon being nearer to the earth at b1 the water will be naturally attracted to the ball1 m1 and cause high water 7a72 and a similar effect will be produced opposite1 because the earth is attracted1 so the waves are higher than the ground which has been attracted away from the water1 and the waters will flow in and cause a high tide at d1 but not so high a tide as at the opposite point1 a4 ,it can then be understood that there will be low water at the other two sides1 e and f1 because the water has been taken away1 so to speak1 for the high tides at a and d4 ,we shall learn more of this under ,physical ,geography4 ,illustration3 ,fig4 #egj4--,new ,moon4 ,the moon revolves round the earth in a changeable elliptical orbit1 intersecting the ecliptic at certain points called ,nodes4 ,when the moon is nearest to the ,earth she is said to be in perigee when farthest from us she is in apogee 7the line uniting these points is the line of apsides71 the difference in distance being about #d1jjj miles4 ,she passes the sun periodically1 and so if the moon moved in the plane of the ecliptic there would be eclipses of the sun and moon twice a month2 but as the orbit is inclined a little1 she escapes by moving north or south4 ,we will now endeavour to explain this theory4 ,,eclipses4 ,we have briefly considered the ,,sun and ,,earth and the ,,moon separately4 ,we are now about to regard the effects produced by them when they come in each other's way and cause ,,eclipses1 which are observed with so much interest4 ,there are eclipses of the sun and of the moon4 ,the former occur at the time of new moon1 and the latter at full moon2 and this will be at once understood when we remember that the sun is eclipsed by the moon passing between us and the sun2 and the moon is eclipsed because the shadow of the earth falls upon her when she is opposite the sun1 and therefore 8full40 ,readers of the voyages of ,columbus will remember that he managed to obtain supplies from negatively hostile ,jamaica savages by pretending to cause an eclipse of the moon1 which he knew was about to take place1 and to the ancients eclipses were of dire portent4 ,even in enlightened ,rome1 to ascribe an eclipse to the causes of nature was a crime4 ,the ,chinese have an idea that great dragons are devouring the moon when she is eclipsed4 ,illustration3 ,fig4 #ega4--,solar eclipse with corona4 ,there are total1 partial1 and annular eclipses4 ,the former terms speak for themselves2 the latter name is derived from 8annulus10 a ring2 for a ring of light is left around the dark portion eclipsed1 and is only seen in solar eclipses4 ,in one sense the eclipse of the sun is really an eclipse of the earth1 because it is caused by the shadow of the moon falling upon the earth4 ,illustration3 ,fig4 #egb4--,umbra and penumbra4 ,if a bright body1 ,a1 be larger than the dark body1 ,b1 there will be two kinds of shadows--viz41 the umbra and the penumbra4 ,for instance1 the umbra is the central dark part in the cut 7fig4 #egb71 and the penumbra is the lighter portion4 ,as soon as the eye is placed on the umbra1 it can perceive no part of the source of light1 ,a1 which appears to be eclipsed4 ,on the other hand1 the penumbra originates in that locality where only a portion of the light proceeding from a luminous object can fall2 hence an eye in the penumbra would see a part1 but not the whole of the illuminating body4 ,this shadow also forms a cone1 the apex of which1 if extended1 will fall before the opaque body4 ,if we receive the shadows so projected at m n1 for example1 on a white sheet1 we have in the centre a dark circle1 which is the umbra1 surrounded by the penumbra1 which gradually decreases in intensity towards the exterior 7see fig4 #egc74 ,the farther we hold the sheet from the body producing the shadow1 the umbra decreases1 and the penumbra is enlarged4 ,for where 7in solar eclipses7 the umbra falls there is totality2 within the penumbra partial eclipse only4 ,illustration3 ,fig4 #egc4--,lunar eclipse4 ,lunar ,eclipse4--,let ,a 7fig4 #egc7 be the sun1 and ,b the earth1 the length of the umbra of the latter will exceed #ajh diameters of the earth4 ,since the moon is only about thirty terrestrial diameters distant from the earth1 and as the diameter of the earth's shadow1 at this distance1 is nearly three times as large as the apparent diameter of the moon1 it follows that when the latter enters this shadow1 she must be totally eclipsed1 for at those places where the moon's shadow falls there is total eclipse4 ,if the moon's orbit were coincident with the ecliptic1 or if both moon and earth moved round the sun in the same plane1 there would be an eclipse at every conjunction1 and at every opposition1--i4e41 a solar eclipse would happen at every new moon1 and a lunar eclipse at every full moon4 ,but we have seen that the lunar orbit cuts the ecliptic only in two points2 consequently an eclipse of the moon is possible only when1 at the time of opposition1 the moon is in one of her nodes1 or in close proximity to it1 which can only occur twenty-nine times in the space of eighteen years4 ,a lunar eclipse begins on the eastern margin of the moon1 and is either total1 when her whole disc enters the umbra1 or partial1 when only part of her disc is in the shadow4 ,a total eclipse may last for two hours4 ,we shall understand this better1 perhaps1 with the diagrams4 ,illustration3 ,fig4 #egd4--,solar eclipse4 ,solar ,eclipses4--,when the moon and the sun are in conjunction1 the moon's place may be represented by ,m 7fig4 #egd7 between the earth1 ,t1 and the sun1 ,s4 ,if this conjunction occur when the moon is in one of her nodes1 or within #af of it1 the shadow of the moon will fall upon the earth1 and the sun will be eclipsed4 ,at other places the sun will not be entirely covered2 and if the moon be moved farther off1 so that its shadow will not reach the earth1 and so not cover the sun up completely1 we shall have an annular eclipse1 because a rim of the sun will be visible4 ,the lunar umbra extends from the moon by a space about equal to her distance from the earth1 and hence only a small portion1 d1 of the earth's surface enters the lunar umbra4 ,to the inhabitants of this part of the earth the sun will be totally eclipsed1 and the eclipse will be annular if only the margin of the sun's disc remain uneclipsed by the lunar shadow4 ,this is only possible when the moon is in her apogee1 or greatest distance from the earth1 where her apparent diameter is less than that of the sun1 which it cannot in general exceed more than #a #ch4 ,hence the duration of a total eclipse of the sun cannot be more than #c minutes4 ,on the contrary1 the penumbra of the moon is diffused over a much larger portion1 n m1 of the surface of the earth1 since its section is five-ninths of the earth's diameter4 ,the inhabitants of this portion of the earth do not receive light from all parts of the sun1 consequently a part of this luminary is invisible to them1 and the eclipse is said to be partial4 ,solar eclipses commence on the western margin of the sun1 and advance to the eastern4 ,on account of the proximity of the moon to us1 an eclipse of the sun is1 in all places above the horizon of which the sun appears1 visible neither at the same time1 nor is it of equal duration1 nor of equal extent3 in some parts it may not be visible at all4 ,in favourable situations1 the diameter of the umbra1 where it reaches the earth1 amounts to about #afg miles1 and on this small strip of the earth's surface only can the sun appear totally eclipsed4 ,illustration3 ,fig4 #ege4--,lord ,rosse's monster telescope4 ,,chapter ,,xxxix4 ,,the ,,planets ,,and ,,asteroids4 ,,mercury4 ,including our own globe there are eight principal planets--viz41 ,mercury1 ,venus1 ,mars1 ,jupiter1 ,saturn1 ,uranus1 and ,neptune4 ,the two first-named being between us and the sun1 are termed interior planets2 the others are exterior4 ,mercury1 ,venus1 and ,mars are smaller than ,earth4 ,the other four are much larger4 ,illustration3 ,fig4 #egf4--;,an ,orrery4 ,we have already described the planets as bodies wandering through the zodiac1 and reflecting the sun's light4 ,their orbits are very different from the moon's2 for instance1 planets take a retrograde motion as well as a direct one4 ,the sun and the planets revolving around him constitute the solar system4 ,we will commence our brief consideration of them with ,mercury1 the planet nearest to the sun4 ,the distance of ,mercury from the sun is #ce1jjj1jjj of miles1 less than half the distance our earth is from him1 and so receives much more heat and light than we do4 ,the sun to the ,mercurians1 if there be any inhabitants upon the planet1 must appear about seven times larger than he does to us4 ,mercury's year is about eighty-five days in length1 so the seasons must be shorter if they follow the same rotation as ours4 ,it passes through space with an exceedingly rapid motion1 and so probably the ancients called the swift planet ,mercury after the winged messenger of ,jove4 ,mercury is not an easy planet to observe1 owing to its proximity to the sun1 yet the ancients managed to descry it4 ,but it can be seen just before sunrise and sunset in autumn1 and in spring if the weather be clear4 ,it possesses phases similar to our moon4 ,some authorities have stated that ,mercury has an atmosphere1 but this circumstance1 as well as its formation1 is still shrouded in mystery4 ,mercury's day is a few minutes longer than ours4 ,illustration3 ,fig4 #egg4--,transit of ,mercury4 ,a transit of ,mercury is represented in the accompanying illustration 7fig4 #egg74 ,this phenomenon took place in #ahde1 but there have been many others noticed4 ,the first recorded took place in ,november #afca1 and these transits always occur in ,may or ,november4 ,,venus4 ,venus is the planet next in order1 and revolves about #ff1jjj1jjj of miles from the sun4 ,it is the nearest planet to the earth1 and is somewhat smaller than the latter4 ,this planet is both a morning and evening star1 and is very brilliant--so much so1 that any close observation with the telescope is not possible2 and when at her nearest point she is invisible as she passes between us and the sun1 and of course when fully illuminated she is directly beyond the sun1 and enclosed in his rays4 ,but under other circumstances she is distinctly visible as a crescent in the evening1 and nearly full as a morning star4 ,venus goes round the sun in #bbd days1 and her day is rather less than ours4 ,illustration3 ,fig4 #egh4--,orbit of ,venus4 ,venus has long been celebrated as the morning and evening star1 as 8,lucifer0 and 8,hesperus40 8,lucifer1 son of the morning10 is mentioned by ,isaiah4 ,that ,venus possesses an atmosphere denser than our own can scarcely be doubted4 ,the observations made during the successive transits1 particularly the last 7#ahgd71 seem to have established the fact that aqueous vapour exists around1 and water in1 ,venus4 ,no satellite can be found1 though the ancients reported such an attendant upon this planet4 ,the apparent diameter of ,venus varies considerably in consequence of her varying distances at the inferior and superior conjunction4 ,when nearest the earth1 if she presented her fully illuminated disc to our gaze1 we should see a miniature moon1 and even under the circumstances ,venus throws a shadow1 so brilliant is her light4 ,illustration3 ,fig4 #egi4--,venus1 at quadrature4 ,the transits of ,venus have been referred to1 and1 like those of ,mercury1 are simply a passing1 or 8transit10 of the planet across the illuminated disc of the sun4 ,the transits afford means to ascertain the volume and distance1 etc41 of the sun1 and this year 7#ahhb7 the next transit is expected4 ,there will not be another for more than one hundred years4 ,illustration3 ,fig4 #ehj4--,venus1 near inferior conjunction4 ,whether ,venus has a constitution similar to our globe is of course doubtful4 ,the matter is less dense than the earth1 and there is an atmosphere half as dense again as ours4 ,spots have been noticed crossing the planet1 which may have been vapours or clouds1 and the rotation of ,venus on its axis was calculated from these spots as being #bc;h #bam #bbs4 ,the seasons in ,venus must be very different from ours1 as her inclination is greater than our earth1 and as the sun is so much nearer to her than to us her tropical and polar regions are close1 and a vertical sun is scarcely enjoyed by two places for three successive days1 and she may have two winters and summers1 two springs and autumns6 ,,mars4 ,having already considered the earth1 we pass on from ,venus to ,mars4 ,the orbit of the latter planet is exterior to the earth's1 as is proved by his never appearing 8horned10 nor ever passing across the sun's disc4 ,therefore no 8transits0 of ,mars can take place as transits of ,venus and ,mercury4 ,yet ,mars is most favourably situated for astronomical observation by us1 because it turns its full disc to us4 ,venus is nearer to us than ,mars--but1 as we have explained1 when she comes nearest to us she is quite invisible4 ,astronomers have been enabled to ascertain a good deal concerning the planet of war--8the red planet ,mars40 ,mars has been considered very like the earth4 ,we perceive seas and continents1 and the shape of ,mars is like the earth4 ,but our globe is larger than ,mars1 which is much less dense1 so the force of gravitation is less also4 ,mars moves upon his axis in about twenty-four hours and a half1 and takes rather more than #fhf days to revolve round the sun4 7,see page #dhi47 ,thus its days are a little longer than1 and its years twice as long as our days and years4 ,when in 8opposition10 or on the opposite side of us from the sun1 ,mars is at his brightest4 ,this happened in ,september #ahgg4 ,he will come close again to us in #ahib4 ,illustration3 ,fig4 #eha4--,mars seen from the earth4 ,all planets are wanderers1 but of all the wanderers ,mars has the most eccentric orbit4 ,he curls about1 so to speak1 in loops and curves in a very irregular manner1 and therefore his distance from the earth varies very considerably2 and this eccentric behaviour of the warlike planet must have1 as we believe it did1 puzzled the ancients very much4 ,but--and here reason came to human aid--this very fact1 this great eccentricity of the planetary motions1 caused ,copernicus to investigate the subject with great attention1 and he at length explained the true reason of these irregular orbits from the hypothesis that it was around the sun1 and not around the earth that the planets moved in regular orbits4 ,it is quite ascertained that ,mars is very like our earth in miniature4 ,we annex a diagram of the planet1 and when it is examined with a good telescope the seas and continents can be quite distinctly perceived4 ,at the poles there appears to be a white or snowy region at varying periods1 which would lead us to the conclusion that the atmospheric changes and the seasons are similar to our own2 and as the inclination of the planet is nearly the same as the earth1 this supposition may be accepted as a fact4 ,thus we see that ,mars is the most like earth of all the planets1 and its inhabitants--if1 indeed1 it is now inhabited--must have a beautiful view of us when the weather is fine1 for we are so much larger4 ,mars is also attended by two satellites1 or moons1 as ,professor ,hall reported from ,washington in #ahgg4 ,these moons have been named ,deimos and ,phobos1 and are both very small1 their diameter being only about six miles2 but late astronomers have reasoned that they must be three times this diameter4 ,illustration3 ,fig4 #ehb4--;,earth seen from ,mars4 ,there have been numerous theories concerning ,mars being inhabited1 and of course these suggestions made respecting life on one planet may1 with varying circumstances1 be applied to another4 ,each planet may have had1 or may yet have1 to pass through what has been termed a 8life-bearing stage40 ,we on earth are at present in the enjoyment of that stage4 ,so far as we can tell1 therefore1 ,mars may be inhabited now1 as he bears much the same appearance as our planet4 ,certain changes are going on in ,mars1 and all planets1 just as they go on here in our earth1 and as they did long1 long ages before the earth was populated1 and which will continue to go on after life on the earth has ceased to exist4 ,mars is1 as we know1 much further away from the sun than earth is1 and must receive less direct heat4 ,when he was created1 or formed1 we can only conjecture1 but in all probability he cooled before the earth did1 as he is smaller4 ,here another theory concerning the state of ,mars arises1 and in support of it we may quote an ,american authority upon the planet4 8,his mass is not much more than one-ninth of the earth's1 while his surface is about one-third of hers4 ,then1 if originally formed of the same temperature1 he had only one-ninth her amount of heat to distribute4 ,if he had radiated it away at one-ninth of her rate1 his supply would have lasted as long1 but radiation takes place from the surface in proportion to the surface1 hence he parted with it three times as fast as he should have done to cool at the same rate as the earth1 and must have attained a condition which she will not attain until three times as long an interval has elapsed from the era of her first existence than has already elapsed4 ,geologists agree that the last-named period must be measured by many millions of years2 hence it follows that twice as many millions of years must elapse before our earth will be in the same condition as ,mars1 and ,mars must be three times as far on the way toward planetary decrepitude and death as our earth4 ,then assigning two hundred thousand years as the extreme duration of the period during which men capable of studying the problems of the universe have existed1 and will exist on this earth1 the theory holds that ,mars would have entered on that stage of his existence many millions of years ago1 and that the appearance of the planet itself implies a much later stage of planetary existence40 ,mars is a very interesting study1 and the reddish hue which is so distinctive is perceived in certain spots when examined by the telescope's aid4 ,these red places were discovered by ,cassini4 ,mr4 ,dawes made drawings of ,mars1 and ,mr4 ,proctor has by their aid constructed a regular map of ,mars1 and a chart of the surface of the planet4 ,there is much more land than water on ,mars1 as the bright surfaces which indicate land are much more extensive than the darker portions which betoken the existence of water4 ,but these 8markings0 are not always visible1 in consequence of something coming between us and the land on ,mars1 and this has been attributed to the production of vegetation1 which a ,french savant declared was ruddy-coloured1 and that this autumnal tint departed in the winter4 ,the seasons of ,mars are not equal1 in consequence of his wandering propensities1 and winter is warmer up there than our winter1 while summer is cooler than our summer4 ,that there are clouds and an aqueous atmosphere surrounding ,mars we learn from spectroscopic observation and analysis1 and in fine we may look upon ,mars as similar to our earth4 ,respecting the question of its habitation we take the liberty to quote ,mr4 ,richard ,proctor3-- 8,i fear my own conclusion about ,mars is that his present condition is very desolate4 ,i look on the ruddiness of tint to which ,i have referred as one of the signs that the planet of war has long since passed its prime4 ,there are lands and seas in ,mars1 the vapour of water is present in his air1 clouds form1 rains and snows fall upon his surface1 and doubtless brooks and rivers irrigate his soil1 and carry down the moisture collected on his wide continents to the seas whence the clouds had originally been formed4 ,but ,i do not think there is much vegetation on ,mars1 or that many living creatures of the higher types of ,martian life as it once existed still remain4 ,all that is known about the planet tends to show that the time when it attained that stage of planetary existence through which our earth is now passing must be set millions of years1 perhaps hundreds of millions of years ago4 ,he has not yet1 indeed1 reached that airless and waterless condition1 that extremity of internal cold1 or in fact that utter unfitness to support any kind of life1 which would seem to prevail in the moon4 ,the planet of war in some respects resembles a desolate battle-field1 and ,i fancy that there is not a single region of the earth now inhabited by man which is not infinitely more comfortable as an abode of life than the most favoured regions of ,mars at the present time would be for creatures like ourselves40 ,illustration3 ,fig4 #ehc4--;,,chart ,,of ,,mars 7,names according to ,proctor and ,green74 ,a ,peer ,continent4 ,b ,herschel ,continent4 ,c ,fontana ,land4 ,d ,secchi ,continent1 ,east4 ,e ,secchi ,continent1 ,central4 ,f ,secchi ,continent1 ,west4 ,g ,mdler ,continent4 ,h ,leverrier ,land4 #a ,herschel ,strait4 #b ,dawes ,ocean4 #c ,maraldi ,sea4 #d ,oudemans ,sea4 #e ,trouvelot ,bay4 #f ,funchal ,bay4 #g ,campani ,sea4 #h ,de la ,rue ,ocean4 ,,the ,,moons ,,of ,,mars4 ,we must devote a few lines to the satellites of ,mars1 which during the last four years have proved a very interesting study for the astronomers1 and some very interesting facts have been ascertained concerning the ruddy planet1 which is now proved not to be 8moonless ,mars10 as the poet declared4 ,there are two satellites1 which1 in consequence of their distance from him1 being so different1 vary in apparent size4 ,the outer one is twelve thousand1 the inner one about three thousand five hundred miles from the planet1 so the former would revolve in about thirty hours in a direction from west to east1 and the inner moon goes round in the same way in about seven hours and a half4 ,mars revolves in twenty-four and a half hours from west to east4 ,so the outer moon rises for him in the east1 and the inner one in the west4 ,this is accounted for by the fact that one travelling slower than ,mars rises in the east1 the other outruns him1 and comes up in the west4 ,but if we suppose ourselves upon ,mars we shall find that1 after all1 we have only one moon properly so called4 ,the outer satellite is very small and very far away1 so it is useless to give light--at most1 it is no bigger than ,mars appears to us on earth4 ,so the ,martians do not see two moons passing each other in the sky--that is1 unless their eyes are of greater range and power than ours4 ,thus they have one moon rising in the west1 appearing in all its phases every night1 while our moon takes twenty-eight days to pass through her phases2 for we must remember that ,mars' moon takes only seven hours and forty minutes to pass through its orbit1 and therefore each quarter will not occupy quite two hours4 ,,the ,,minor ,,planets1 ,,or ,,asteroids4 ,passing onward from ,mars towards ,jupiter we arrive at a number of smaller planets1 which will not concern us very much1 as they are very small and scarcely visible without a good telescope4 ,but a very interesting chapter in the history of astronomy was commenced when the discovery of these bodies was begun4 ,in old times astronomers noticed a very considerable gap between ,mars and ,jupiter1 which was remarkable when the regular progression of the distances between the planets was remembered4 ,so ,kepler was of opinion that some planet would be discovered having its orbit in that space between ,mars and ,jupiter4 ,it is1 however1 to ,piazzi1 the ,italian1 that the discovery of the zone of asteroids is due4 ,illustration3 ,dec4 #hth4 ,dec4 #ith4 ,fig4 #ehd4--;,field of view showing motion of minor planets amongst the stars4 ,piazzi was surveying the constellation ,taurus1 where he fancied he had discovered a change of place in a star which he had observed on the #ast of ,january in that year 7#ahja74 ,he was quite sure of this change next day 7the #crd of ,january71 and he expressed his opinion to ,bode and ,oriani4 ,but letters took a long time to pass in those days1 and when the other astronomers had received the advices the new star had been lost in the sun's glory4 ,but after a year1 on the #cast ,december1 #ahja1 the planet was again seen and the discovery was proved4 ,the new planet was named ,,ceres4 ,the discovery of ,ceres led to other discoveries4 ,for1 while searching for her1 ,olbers found other minor planets1 and so on to the present day4 ,now we have nearly two hundred asteroids1 and more are probably to be found in the zone beyond ,mars4 ,it would answer no purpose to give a list of the asteroids4 ,we need only remark that the first four were discovered in quick succession1 and then a lapse of thirty-eight years occurred before the fifth was found1 thus-- ,,ceres1 discovered by ,piazzi at ,palermo1 ,january #ast1 #ahja4 ,,pallas1 8 ,olbers at ,bremen1 ,march #bhth1 #ahjb4 ,,juno1 8 ,harding at ,lillienthal1 ,september #bnd1 #ahjd4 ,,vesta1 8 ,olbers at ,bremen1 ,march #bjth1 #ahjg4 ,,astr,a1 8 ,hencke at ,driessen1 ,december #hth1 #ahde4 ,since #ahdh there have been numerous minor planets discovered every year4 ,the hypothesis that all these asteroids are fragments of one large planet which has been destroyed was started by ,olbers2 and in confirmation of this view it has been determined that the asteroids have essentially the same character4 ,the orbits of these minor planets are different from the larger 8wanderers10 and cross each other1 as will be seen from the accompanying diagram1 so that a collision may one day ensue4 ,planetoids and extra zodiacal planets are titles which have been bestowed upon these bodies1 of which ,,vesta is the first in order in the system1 and revolves in #a1cbe days1 at a mean distance of #bbe1jjj1jjj of miles from the sun4 ,,juno and ,,ceres take each about four of our years to revolve in their orbits1 at greater distances still1 averaging #bfj1jjj1jjj of miles4 ,pallas and ,ceres are most alike in their periods and distance from the sun2 the principal asteroids are only about #cjj miles in diameter1 while the smaller are very tiny indeed1 and one certainly has quite disappeared4 ,illustration3 ,fig4 #ehe4--,orbit of asteroids4 ,,jupiter1 ,,the ,,giant4 ,jupiter has been well named the ,giant planet1 since his diameter is eleven times greater1 and he is thirteen hundred times larger than our planet4 ,his inclination is very small1 and you now know that under such circumstances he enjoys very small changes of seasons4 ,jupiter has four moons1 or satellites1 and an illustration of the 8,jovian ,system0 is herewith given4 ,illustration3 ,fig4 #ehf4--,the ,jovian ,system4 ,jupiter himself was well known to the ancients1 but ,galileo was the discoverer of the 8moons40 ,his telescope was1 of course1 a very imperfect instrument1 and while he was gazing at the planet he noticed three stars close by the bright disc1 two on one side1 but next day ,galileo perceived them all at the same side4 ,next time he looked there were only two1 and after many anxious observations he found out1 not only that ,jupiter had three attendant stars1 but four6 ,these moons were found to revolve round ,jupiter in times varying from nearly two days to nearly sixteen days1 according as they were at a less or greater distance from him4 ,they were found to have their times of eclipses and transits1 etc41 also4 ,these moons act with respect to ,jupiter very much as the inner planets act with respect to the sun1 for observation showed ,galileo that the satellites sometimes appeared on one side of the planet1 and at other times on the opposite side4 ,from the diagram of the ,jovian ,system we shall understand the orbits of the moons1 which are all of nearly equal size1--two thousand miles in diameter1--and cause eclipses of the sun to ,jupiter4 ,if the earth be in the same direction as the sun the moons are lost to view4 ,the satellites disappear into the shadow1 and are eclipsed at #a1 #b1 #c1 #d1 respectively1 but they do not always come into view again immediately they have passed through the planet's shadow1 because the earth is a little at one side of the sun4 ,so when the satellite gets behind the edge of ,jupiter1 his shadow being on the opposite side to the satellite's1 it is said that the 8moon0 is in 8occultation02 when it disappears in the shadow it is 8eclipsed40 ,cassini discovered the 8transit0 of ,jupiter's moons4 ,the annexed diagram illustrates the eclipses1 etc41 very clearly4 ,at the four points1 ,a ,b ,c ,d1 we have the earth2 ,j is ,jupiter with his moons2 #a #b #c #d is their orbits4 ,at a moon ,no4 #a enters his shadow1 and emerges at b4 ,from the earth at ,d a will be visible1 but not b1 because ,jupiter is in the way4 ,so at ,b1 the coming out1 or emersion1 will be visible1 but not the entrance into the shadow1 or immersion4 ,at ,a the satellite is in transit d1 on the disc of the planet1 ,j4 ,illustration3 ,fig4 #ehg4--,satellite in ,transit4 ,illustration3 ,fig4 #ehh4--;,eclipses of ,jupiter's ,moons4 ,from the observation of the eclipses of ,jupiter's moons the rate of the transmission of light was discovered by ,romer in #afge1 and its progressive motion was calculated4 ,the eclipses were noticed to take place later than the calculated time1 when the planet was approaching conjunction4 ,romer suggested that the delay was owing to the greater distance the light had to travel--a distance equal to the diameter of the earth's orbit1 or about #aij1jjj1jjj of miles4 ,the time was about sixteen minutes4 ,light was found to travel at the rate of nearly #ab1jjj1jjj of miles a minute4 ,let us now endeavour to picture ,jupiter himself4 ,here we have an illustration of the planet4 ,he is the biggest1 and the brightest1 except ,venus1 of all the planets4 ,he revolves at a distance of #dgf1jjj1jjj of miles from the sun1 and his year is equal to nearly twelve of ours1 while his day is scarcely ten hours long1 showing a rapidity more than twenty times the rate of our earth4 ,jupiter1 therefore1 must have a very much greater diameter than the earth4 ,there is much less sunlight and heat found on ,jupiter than upon ,earth1 because he is so much farther from the sun than we are1 but at the same time the heat comes at less intervals than with us4 ,and here the theory already noticed respecting the gradual cooling of the planets will be remembered4 ,jupiter1 we can easily imagine1 would take much longer to get cool than ,mars or the earth1 and1 though his rapid rotation would assist him1 he must be still in the midst of a glowing atmosphere without form and void--perhaps a furnace for cloud and vapour generation4 ,illustration3 ,fig4 #ehi4--;,jupiter4 ,now when ,jupiter is examined with the telescope it will be seen that he is crossed by belts of vapour 7see also page #dhi72 and when we consider the results of the spectrum analysis of the planet1 we may fairly assume that ,jupiter is in a very heated state1 and that we cannot really perceive the actual body of the planet at all yet4 ,there is an immense quantity of water thus surrounding ,jupiter1 and he is still in the condition in which our earth was before geology grasps its state1 and long ere vegetation or life appeared4 ,the waters have yet to be 8gathered together into one place10 and the dry land has yet to appear upon ,jupiter1 who is a very juvenile1 if a very enormous planet4 ,under these conditions we can safely assume that there are no inhabitants of ,jupiter4 ,the belts1 or zones1 of ,jupiter vary in hue1 and the continual changes which are taking place in this cloud region tend to show that disturbances of great magnitude and importance are occurring4 ,it is useless to speculate upon what will happen in ,jupiter when the disc is eventually cooled4 ,the planet1 we know1 has not nearly reached maturity2 the earth is in the full prime of its life1 and the moon is dead and deserted4 ,what the millions of years which must elapse before ,jupiter has cooled may bring forth we need not try to find out4 ,the earth will then1 in all probability1 be as dreary as the moon is now1 and we shall have returned to dust4 ,,saturn4 ,we now come to the most curious of all the planets--,saturn1 which is an immense globe surrounded by a beautiful bright ring1 or rather series of rings1 and attended by eight moons4 ,he appears to possess much the same constitution as ,jupiter1 but enveloped in an even denser atmosphere than the latter4 ,saturn's diameter is about nine times greater than the earth2 he revolves on an inclined axis in about ten hours1 and has seasonal alternations of unequal length4 ,his year is about thirty of ours 7#aj1gei days74 ,the most striking phenomena in connection with ,saturn are his rings4 ,illustration3 ,fig4 #eij4--,saturn4 ,saturn's rings are supposed to be a close agglomeration of stars1 or satellites1 revolving around the planet and encircling him in a belt4 ,the rings are apparently broad and flat and thin1 resembling roughly the horizon of a globe4 ,the globe of the planet is not exactly in the centre of the rings1 which have been measured1 and are approximately as below3-- ,diameter of exterior ring #afi1jjj miles4 ,diameter of interior ring #abd1jjj 8 ,diameter of innermost ring #ajj1jjj 8 ,interval between innermost ring and ,saturn #ai1jjj 8 ,intervals between the rings #ah1jjj 8 ,thickness of the rings #acj 8 ,breadth of the rings #cg1jjj 8 ,illustration3 ,fig4 #eia4--,saturn's rings at ,equinox4 ,the rings were first recognised as such by ,huyghens in #afei1 but ,galileo had remarked the curious appearance the planet presented4 ,cassini confirmed ,huyghens' discovery1 and found that the ring was duplicated1 and ,mr4 ,ball made the same discovery4 ,the two outermost rings are very bright1 the inner ring being darker and partially transparent1 for the ball of ,saturn can be perceived through it4 ,illustration3 ,fig4 #eib4--;,enlarging ring4 ,but the rings are not always so plainly seen as in the foregoing diagram4 ,sometimes they appear as a mere line of light on each side of the planet1 as shown in the margin4 ,this occurs at the time of the equinox 7fig4 #eia74 ,by degrees1 however1 as they become inclined1 they appear broader 7fig4 #eib74 ,the inner ring may be formed of vapour1 but the outer ones are of something more solid1 as the shadows they cast upon the planet1 and it casts upon them1 at certain times 7figs4 #eic and #eid74 ,illustration3 ,fig4 #eic4--,ring shadow4 ,saturn possesses eight moons1 seven of them revolving in orbits on the plane of the rings1 but one is more inclined4 ,these eight satellites have been named as follows3-- ---------------------------------------- ---------------------------- ,name4 ,distance from ,saturn in ,time of ,discoverer4 radii of ,saturn4 ,miles4 ,revolution4 ---------------------------------------- ---------------------------- d4 h4 min4 #a ,mimas #ccf 7about7 #abj1jjj #bb #cg ,herschel4 #b ,enceladus #dcj 8 #aej1jjj #a #h #ec ,herschel4 #c ,tethys #ecd 8 #aij1jjj #a #ba #ah ,cassini4 #d ,dione #fhd 8 #bdj1jjj #b #ag #da ,cassini4 #e ,rhea #iee 8 #cdj1jjj #d #ab #be ,cassini4 #f ,titan #bbae 8 #gij1jjj #ae #bb #da ,huyghens4 #g ,hyperion #bfgh 8 #ide1jjj #ba #g #g ,lassel and ,bond4 #h ,iapetus #fdcf 8 #b1bej1jjj #gi #j #h ,cassini4 ---------------------------------------- ---------------------------- ,but these eight moons are not so interesting as those belonging to ,jupiter1 because the great distance they are away precludes much examination of them4 ,they vary much in size1 ,titan being the largest1 and perhaps equal to ,mars1 ,iapetus being next in magnitude4 ,the light of these satellites and the rings is no doubt very great in the aggregate1 and must have a magnificent appearance in the heavens 7compare page #dic74 ,very likely there are other attendants upon ,saturn1 but owing to the brilliancy of the rings it is impossible to distinguish them4 ,illustration3 ,fig4 #eid4--,ring shadow4 ,,uranus4 ,uranus was discovered by ,herschel in #agha1 and has been called after its discoverer1 and sometimes the 8,georgium ,sidus40 ,it revolves at an enormous distance from the sun--viz41 #a1gec1jjj1jjj of miles4 ,it takes about eighty-four of our years 7#cj1fhf days7 to go round the sun1 and possesses four moons4 ,it is very much larger than the earth--about four times the diameter1 and forty times its volume4 ,we can only speculate concerning its physical constitution1 which is assumed to be similar to that of ,jupiter1 while the changes of temperature and seasons must vary immensely4 ,the names of the moons are ,ariel1 ,umbriel1 ,titania1 and ,oberon4 ,the outer pair can be seen without much difficulty4 ,,neptune4 ,the existence of this planet was determined by calculation before it had been seen at all4 ,uranus was observed to be disturbed in his orbit1 moving sometimes faster than at others2 and even before ,uranus had been discovered ,saturn and ,jupiter had been seen to be affected by some body in the system4 ,m4 ,leverrier determined to ascertain the cause of this1 and came to the conclusion that some other planet was influencing ,uranus4 ,the ,newtonian theory here received a most convincing proof4 ,while ,leverrier was calculating1 ,mr ,adams of ,cambridge leaped to the same conclusion1 and wrote the result of his calculations to ,professor ,airy1 and the planet was seen1 but not reported upon4 ,meantime ,leverrier published his calculations1 and the observers at ,berlin detected the new planet in ,september #ahdf4 ,illustration3 ,fig4 #eie4--,neptune in field of view with stars of #fth1 #gth1 #hth1 and #ith magnitudes4 ,very little can be said concerning ,neptune1 as its distance is too great for observation4 ,it is at #b1gdf1jjj1jjj of miles from the sun1 and takes #afd years to go round it 7#fj1abf days74 ,it is about the same size as ,uranus4 ,it has one moon1 which moves round the planet in #e;d #ba;h1 and is of great size4 ,,chapter ,,xl4 ,,the ,,fixed ,,stars4 ,,fixed ,,stars--,,magnitude ,,of ,,the ,,stars--,,constellations--,,description s ,,of ,,the ,,zodiacal ,,constellations--,,northern ,,and ,,southern ,,star ,,groups--,,distance ,,of ,,stars4 ,we have been considering the planets so far as they are known to astronomers1 but no doubt we shall find out others some day beyond ,neptune in space1 for it must be assumed that there are other planets wandering about in the infinite firmament4 ,at present1 however1 we cannot spare time for such speculation2 we have got to peep at the stars and their groupings4 8,what little bits of things the stars are10 a child said once in our hearing2 and there were others present who were inclined to believe that the tiny light spots we could see looked small--not because they were distant1 but because they were of no great magnitude2 and when those children were told that the tiny stars were 8suns0 like our sun1 giving heat and light millions and millions of miles away1--and1 so far as we can tell1 some are much bigger and hotter than our own sun1--they were very much surprised indeed1 and one little girl aptly quoted ,dr4 ,watts3-- 8,twinkle1 twinkle1 little star1 ,how ,i wonder what you are06 ,now let us endeavour to learn something about these apparently tiny specks1 and why they 8twinkle40 ,at a very early period in the history of astronomy the observers of the heavens grouped stars together in fancied resemblances to men or animals2 and these 8constellations10 as they are termed1 are combinations of fixed stars--that is1 of stars which do not wander about as the planets do4 ,but these so-called fixed stars have motions2 they are only relatively fixed with reference to their positions to each other as they appear to revolve daily round the earth4 ,but stars have a movement of their own1 which is termed their 8proper motion40 ,it is to ,halley that the discovery of these real star motions is due4 ,he saw three very bright stars 7,sirius1 ,aldebaran1 and ,arcturus7 were not in the places they had been assigned4 ,the sun also has been found to possess a 8proper motion10 and1 with the planets1 is travelling as determined by ,sir ,j4 ,herschel1 to a particular place in the constellation called ,hercules4 ,there are now star catalogues and star maps1 for the heavens have been as closely surveyed as the earth1 and by accurate observations it has now become possible to find the position of every star usually visible4 ,some of the stars are used as 8clock0 stars1 by which sidereal time can be calculated accurately1 and the clocks thereby corrected4 ,the stars1 though termed 8fixed10 are in perpetual movement--,arcturus at the rate of fifty miles a second1 and others less4 ,only the rates of a few are known4 ,the number of the stars is beyond our calculation1 and even the number of stars only visible in the telescope amount to millions1 and these are called telescopic stars4 ,the visible stars amount to about six thousand1 and of course these are the brightest up to the sixth magnitude4 ,there are more visible in the southern than in the northern hemisphere4 ,the magnitudes of the stars range in classes according to the brightness of the stars observed1 for this is really the test from the first magnitude to the sixth2 after that the telescopic stars are seen up to the fifteenth or sixteenth4 ,we can only see about three thousand stars at any one time from any place1 although1 as remarked above1 many millions may be observed with a good telescope1 and as many more1 probably twenty millions1 are invisible4 ,we will now proceed to detail the constellations1 which are familiar by name to everybody4 ,we have already given the names of the zodiacal groups1 which consist of many stars1 each designated by a letter of the ,greek alphabet so far as possible1 then the ,roman letters and numerals are employed4 ,thus 7,alpha7 is the most brilliant star2 7,beta7 the next bright 7,gamma7 the next1 and so on2 so the relative brilliancy of the stars in the constellation is indicated1 but not the very biggest star of the first magnitude is intended by 1 for the star in one constellation may equal in another4 ,john ,bayer originated this method in #afjc4 ,the arrangement of the constellations is plunged in the obscurity of ages1 but ,b4,c4 #cgj there were forty-five thus grouped4 ,there are northern and southern constellations which are visible above our old friends ,aries1 ,taurus1 ,cancer1 etc4 ,we will1 as in duty bound1 consider our old acquaintances first1 and then give a list of the northern and southern groups of stars2 but we shall find that the forms are in the greater part due to the imagination of the ancients1 and do not bear out our ideas of the animals they are supposed to represent1 while at the same time they cross and recross with other constellations in the skies in a very puzzling way4 ,illustration3 ,fig4 #eif4--;,aries4 ,the first constellation is ,,aries1 the ,ram1 which is celebrated in mythology as the proud possessor of the ,golden ,fleece1 which we may remember was seized and carried away by ,jason and the ,argonauts4 ,the ,hellespont is so called from ,helle1 who fell from the ,ram's back when being carried upon it over the ,black ,sea4 ,the ,ram is here represented with the equinoctial ring4 ,we perceive in ,aries two very bright stars near the head4 ,these are 77 ,arietis and 77 ,sheretan4 ,the signs and constellations do not now correspond as they used to do1 because of the change in the position of the stars1 which gives rise to the ,precession of the ,equinoxes 7vide ante41 p4 #dig71 so that the stars which two thousand years ago were in conjunction with the sun1 are much more to the eastward4 ,in olden time 7when astronomy was young71 the sun entered ,aries on the #bast ,march1 and now a change has taken place4 ,but in about another twenty thousand years1 they will all come right again4 ,this will be perceived by reference to the celestial globe4 ,the ,ram has sixty-six stars in his constitution4 ,,taurus1 the ,bull1 is the next constellation4 ,he received his name from the celebrated animal into which ,jupiter transformed himself when he wished to carry away ,europa4 ,the star ,aldebaran 77 is the end of a kind of ,v in the ,bull's face4 ,the ,pleiades are on the shoulder to the right4 ,this cluster of twinkling stars is well known1 and will guide the observer towards the imaginary ,bull1 which we must nowadays describe as rather a fanciful delineation4 ,europe is called after ,europa1 because ,jupiter1 as a ,bull1 carried her to this continent4 ,there are #ada stars in ,taurus1 according to the number found in the list of ,aratus1 and probably more4 ,illustration3 ,fig4 #eig4--,taurus4 ,,gemini1 the ,twins1 which are supposed to be ,castor and ,pollux1 though it is believed that two goats were the original sign--which statement1 taken in connection with the ram and the bull1 that were also turned out in the spring-time1 may have something to recommend it4 ,but now ,castor and ,pollux are generally recognized as the constellation4 ,during the expedition for the ,golden ,fleece1 the electric appearance1 now known as ,st4 ,elmo's ,fire1 became visible upon them1 and their effigies were placed in the forepart of ships as a good omen4 ,this led to the adoption of the 8figure-head40 ,they were made into stars when ,pollux was immortalized by ,jupiter1 for he divided the boon with his brother4 ,the planet ,uranus was discovered near this constellation1 which contains eighty-five stars4 ,illustration3 ,fig4 #eih4--;,gemini4 ,,cancer1 the ,crab1 is the next in order1 and the only derivation we can find for this is that ,juno sent a crab to attack ,hercules when he was busily engaged with the many-headed ,hydra4 ,the crab was directed to pinch the hero's foot1 but it appears rather a lame device for the ,queen to adopt4 ,the crab1 however1 was killed by ,hercules1 and placed amongst the stars by ,juno as a reward2 so he gained immortality cheaply4 ,he1 ,cancer1 contains more than eighty stars1 but none of them of any particular note4 ,some writers explain the sign as reminding the ancients of 8the retrograde movement of the sun to the north02 but as a crab does not move 8backwards10 we will still adhere to mythology as equally satisfactory at any rate4 ,cancer1 however1 was termed the 8northern gate of the sun40 ,illustration3 ,fig4 #eii4--;,cancer4 ,the next is ,,leo1 the ,lion1 which came round in summer and at the period of much heat1 so this fierce animal may have been chosen to represent that season4 ,but mythology will have us credit the ,neman ,lion sent against ,hercules by ,juno as the origin of this constellation4 ,the lion was1 like the crab1 placed amongst the stars when he was killed4 ,he is a very brilliant constellation1 and a very bright star called ,regulus is to be seen in his chest--8,cor ,leonis40 ,another very fine star of the second magnitude is observable in the tail4 ,the ,lion consists of ninety-five stars1 the principal ones being of the first and second magnitudes4 ,illustration3 ,fig4 #fjj4--,leo4 ,,virgo is supposed to be outlined by a very rich cluster of stars1 and one of the first magnitude4 ,the ,virgin is by some supposed to be ,astra1 the goddess1 but is more likely referable to a girl gleaning1 or holding an ear of corn in semblance of the harvest4 ,this constellation contains more than one hundred stars4 ,one of them in the wheat-ear is a particularly brilliant one1 and noted for its 8solitary splendour10 as no star of large magnitude is near it4 ,the ,arabs used to call it the ,solitary ,simak2 ,spica ,virginis is the modern name4 ,illustration3 ,fig4 #fja4--,virgo4 ,,libra1 which follows1 may either indicate the balance1 or scales of justice1 of ,astra1 or the equal day and night at the autumnal equinox4 ,virgil mentions ,astra's balance1 and thus we have a classical authority for the very mythological view of the two foregoing constellations4 ,libra is not very distinct2 it contains fifty-one stars1 four of which are very bright4 ,illustration3 ,fig4 #fjb4--,libra4 ,,scorpio1 the ,scorpion1 according to classical writers1 encountered ,orion1 who is also met with in the stellar universe4 ,the scorpion stung ,orion because he declared there was no living creature he could not overcome by force4 ,on the other hand1 this sign may have some reference to the unhealthy time of year1 and the prevalence of disease about the time that ,scorpio appeared4 ,a beautiful star of reddish hue and of the first magnitude is prominent amongst the brilliant assembly of the ,scorpion's forty-four stars4 ,illustration3 ,fig4 #fjc4--,scorpio4 ,,sagittarius1 the ,archer1 is1 as one can see1 a ,centaur1 and said to be ,chiron1 who was wounded by ,hercules1 and cured by being taken up to ,heaven by ,jupiter4 ,this ,chiron is represented as a great patron of the arts1 and thus the fable may be said to exemplify the proverb1 8,art is long1 time is fleeting02 for readers of mythology will find much more in the legends than is apparent on the surface4 ,but we can now only regard the ,centaur from an astronomical1 and not a philosophical standpoint4 ,sagittarius has no very brilliant stars4 ,he is close to the ,milky ,way1 and contains sixty-nine stars1 five forming a sort of ,v in the bow1 sometimes compared to a ladle or 8dipper40 ,illustration3 ,fig4 #fjd4--,sagittarius4 ,illustration3 ,fig4 #fje4--;,capricornus4 ,,capricornus1 the ,goat1 is supposed to be ,pan--8the great god ,pan10 who turned himself into a goat4 ,the sun was in ,capricornus at mid-winter1 so the 8southern gate of the sun0 was a title bestowed upon him4 ,but now the constellation is later4 ,it does not include any very striking stars1 of which there are fifty-one in the 8,goat40 ,,aquarius1 or the ,waterbearer1 may have referred to wet weather1 or as others declare1 to ,ganymede1 the ,cupbearer4 ,there are four stars in the waterpot like a ,y2 and more than one hundred stars of small brilliancy are included in this constellation4 ,but here again fancy must come to our assistance1 for without a diagram the ordinary observer could not distinguish the ,waterbearer4 ,illustration3 ,fig4 #fjg4--;,aquarius4 ,,pisces1 the ,fishes1 are not plainly defined4 ,it is supposed that ,venus and ,cupid turned themselves into fish when the ,titans assailed ,heaven4 ,this ,constellation occupies a triangle in the sky4 ,illustration3 ,fig4 #fjf4--,pisces4 ,the foregoing are the zodiacal constellations1 and may be more easily remembered by repeating an old rhyme1 which runs as follows3-- 8,the ,ram1 the ,bull1 the ,heavenly ,twins2 ,then1 next the ,crab1 the ,lion shines1 ,the ,virgin1 and the ,scales2 ,the ,scorpion1 ,archer1 and the ,goat1 ,the ,man who holds the ,watering ,pot1 ,the ,fish with ,glittering tails40 ,the arrangement of the various ,constellations at which we have so rapidly glanced1 as well as of those that follow1 has been the work of many different periods4 ,aratus and ,ptolemy are the oldest enumerators1 but modern research has added immensely to the store of knowledge4 ,many of the most prominent stars were named by ,grecian and ,arabian observers1 and many of the names are still retained--such as ,arcturus1 ,rigel1 ,capella1 and others4 ,,the ,,northern ,,constellations4 ,there are1 altogether1 thirty-five of these1 as per list on next page4 ,it is of course impossible to describe them all1 but we will make a few remarks respecting those which will be distinguished most readily1 and the manner of finding out particular stars4 ,there are star maps published1 and with a little attention and reading1 a great many very pleasant evening excursions may be made across the sky1 with or without a telescope4 ,the following is the list of the northern constellations4 ,we have put them in various types to indicate the most important4 ---------------------------------------- --------------------------- ,,no4 ,,of ,,name ,,of ,,constellation4 8,,author40 ,,stars4 ---------------------------------------- --------------------------- ,,ursa ,,major ,the ,great ,bear ,aratus #hg ,ursa ,minor ,the ,lesser ,bear 8 #bd ,perseus ,perseus 8 #ei ,auriga ,the ,waggoner 8 #ff ,botes ,the ,herdsman 7,botes7 8 #ed ,draco ,the ,dragon 8 #hj ,cepheus ,cepheus 8 #ce ,canes ,venatici ,the ,greyhounds ,hevelius #be ,hunting ,dogs ,cor ,caroli ,heart of ,charles ,halley #c ,triangulum ,the ,triangle ,aratus #af ,triangulum ,minor ,the ,little ,triangle ,hevelius #aj ,musca ,the ,fly ,bode #f ,lynx ,the ,lynx ,hevelius #dd ,leo ,minor ,the ,lesser ,lion 8 #ec ,coma ,berenices ,berenice's ,hair ,tycho ,brah #dc ,camelopardalis ,the ,giraffe ,hevelius #eh ,mons ,menelaus ,mount ,menalaus 8 #aa ,corona ,borealis ,the ,northern ,crown ,aratus #ba ,serpens ,the ,serpent 8 #fd ,scutum ,sobieski ,sobieski's ,shield4 ,hevelius #h ,hercules ,hercules ,aratus #aac ,serpentarius ,the ,serpent-bearer 8 #gd ,taurus ,poniatowski ,poniatowski's ,bull ,poczobat #g ,,lyra ,the ,harp1 or ,lyre ,aratus #bb ,vulpecula et ,anser ,fox and ,goose ,hevelius #cg ,sagitta ,the ,arrow ,aratus #ah ,,aquila ,the ,eagle 8 #ga ,delphinus ,the ,dolphin 8 #ah ,cygnus ,the ,swan 8 #ha ,,cassiopeia ,the ,lady's ,chair 8 #ee ,equuleus ,the ,little ,horse ,ptolemy #aj ,lacerta ,the ,lizard ,hevelius #af ,pegasus ,pegasus 7,flying ,horse7 ,aratus #hi ,andromeda ,andromeda 8 #ff ,tarandus ,the ,reindeer ,lemounier #ab 7,there are a few others marked in continental maps47 ---------------------------------------- --------------------------- ,the ,,great ,,bear1 or 8,charles's ,wain10 or the 8,plough10 as ,ursa ,major is variously called1 is of great value in indicating the pole star1 which1 when once known1 can never be mistaken4 ,this constellation has also been termed the 8,dipper10 and is very conspicuous in the northern hemisphere4 ,the three stars form the bear's tail1 or the handle of the 8plough02 the others form the body1 ,charles's ,wain1 or 8,karl-,wagen10 the ,german term for peasant's cart1 is represented by the quadrangle forming the cart1 and the other three stars are the horses4 ,the 8,pointers0 are the two end stars1 and if a line be followed northwards from them it will lead close to ,polaris1 the principal star in the lesser bear4 ,this pole star is of a very great brightness1 and peeps out1 almost isolated1 with a pure lustre4 ,the names of the pointers are ,dubhe and ,menak4 ,the star at the tail-tip is ,benetnasch1 then ,mizar and ,alioth4 ,megrez and ,phad are the remaining pair4 ,we append a rough outline of the bear1 for the information of those who have not yet noticed it4 ,the ,lesser ,bear is not so important as his elder brother as regards size1 but he is very useful to astronomers4 ,he resembles the ,great ,bear in appearance1 but is smaller1 and the positions of the stars are inverted4 ,in the cut on page #eee 7fig4 #fbi7 you see the little bear swinging round the polar star1 which is at the tip of the ,lesser ,bear's tail1 so any one will be enabled to find him if they look for the polar star1 and then count the three stars away from it1 and the four in the body4 ,the ,great ,bear's tail points in the other direction4 ,this movement of the earth's axis by displacing the equinoctial points1 alters the 8declination0 and 8right ascension0 of the stars 7compare page #dgc74 ,so ,polaris is gradually approaching the actual polar point4 ,in about #bjj years he will have got as close as he can1 and will then begin to recede from it1 and in about #ab1ejj years after he will reach his most distant point4 ,illustration3 ,fig4 #fjh4--,the ,great ,bear4 ,,polaris1 the ,pole ,star1 was called 8,cynosure0 by the ancients1 and thus we can understand the quotation1 8,cynosure of neighbouring eyes10 when a person or object is very attractive4 ,the pole star was the point to which all looked4 ,there are some other very important stars in these constellations4 ,for instance1 in-- ,perseus we have ,algenib and ,algol1 of second magnitude4 ,auriga we have ,capella1 of the first magnitude4 ,botes we have ,arcturus1 of the first magnitude4 ,lyra we have ,vega1 a very large and bright star4 ,aquila1 ,altair1 also a very beautiful star4 ,in ,cygnus there is ,deneb1 of the first magnitude4 ,these stars are also designated by the ,greek letters--1 lyr1 or the first in the ,lyre--that is1 ,vega2 and so on for all1 according to rank1 as already explained4 ,,southern ,,constellations4 ,we must pass on to the southern constellations1 of which there are forty-six2 the principal ones are in capital letters3-- ---------------------------------------- ------------------------------ ,,no4 ,,of ,,name ,,of ,,constellation4 8,,author40 ,,stars4 ---------------------------------------- ------------------------------ 99 ,phnix ,the ,phnix ,bayer #ac ,apparatus ,sculptoris ,the ,sculptor's ,tools ,lacaille #ab ,eridanus ,fluvius ,the ,river ,po ,aratus #hd 99 ,hydrus ,the ,water-snake ,bayer #aj ,cetus ,the ,whale ,aratus #ig ,fornax ,chemica ,the ,furnace ,lacaille #ad 99 ,horologium ,the ,clock 8 #ab 99 ,rheticulus ,rhomboidialus ,the ,rhomboidal ,net 8 #aj 99 ,xiphias ,dorado ,the ,sword-fish ,bayer #g 99 ,celapraxitels ,the ,engraver's ,tools ,lacaille #af ,lepus ,the ,hare ,aratus #ai ,columba ,noachi ,noah's ,dove ,halley #aj ,,orion ,orion ,aratus #gh ,argo ,navis ,the ship ,argo 8 #fd ,,canis ,,major ,the ,great ,dog 8 #ca ,equuleus ,pictoris ,the ,easel ,lacaille #h ,monoceros ,the ,unicorn ,hevelius #ca ,canis ,minor ,the ,lesser ,dog ,ptolemy #ad 99 ,chameleon ,the ,chameleon ,bayer #aj ,pyxis ,nautica ,the ,mariner's ,compass ,lacaille #d 99 ,piscis ,volans ,the ,flying ,fish ,bayer #h ,hydra ,the ,snake ,aratus #fj ,sextans ,the ,sextant ,hevelius #da 99 ,rober ,carolinum ,charlie's ,oak ,halley #ab ,antlia ,pneumatica ,the ,air ,pump ,lacaille #c ,crater ,the ,cup ,aratus #ca ,corvus ,the ,crow 8 #i 99,crux ,australis ,the ,southern ,cross ,royer #f ,apis ,musca ,the ,south ,fly ,bayer #d 99 ,avis ,indica ,the ,bird of ,paradise 8 #aa 99 ,circinus ,the ,compass ,lacaille #d ,centaurus ,the ,centaur ,aratus #ce ,lupus ,the ,wolf 8 #bd ,norma ,the ,square ,lacaille #ab 99 ,triangulum ,australis ,the ,southern ,triangle ,bayer #e 99,ara ,the ,altar ,aratus #i 99 ,telescopium ,the ,telescope ,lacaille #i ,corona ,australis ,the ,southern ,crown ,ptolemy #ab 99 ,pavo ,the ,peacock ,bayer #ad 99 ,indus ,the ,indian 8 #ab ,microscopium ,the ,microscope ,lacaille #aj 99 ,octans ,hadliensis ,hadley's ,octant 8 #dc 99 ,grus ,the ,crane ,bayer #ad ,toucan ,the ,toucan 8 #i ,pisces ,australis ,the ,southern ,fish ,aratus #bd 99 ,mons ,mensa ,table ,mountain ,lacaille #cj ---------------------------------------- ------------------------------ ,we need only describe ,orion and ,canis ,major1 the principal groups4 ,the former certainly constitutes the most glorious group1 and it is visible to all the world1 because the equinoctial passes through it4 ,,orion1 as we have said1 can be viewed from either hemisphere1 and so can some others2 but those marked with an asterisk in the foregoing list are not visible in the latitude of ,london4 ,illustration3 ,fig4 #fji4--,orion4 ,orion is a very brilliant constellation1 and contains two fine stars of the first magnitude1 and some of the second4 ,the former are ,betelgeux and ,rigel4 ,bellatrix is the third in order4 ,the 8belt0 is formed of three bright stars1 and the sword is visible as five stars just below4 ,canis ,major possesses ,sirius1 a very fine star 7the dog star74 ,canis ,minor has two of the first and second magnitude1 and ,hydra has one of the first4 ,the ,southern ,cross is a beautiful constellation1 invisible in our latitude1 but familiar to sailors in the ,southern ,seas4 ,,the ,,stars' ,,distance ,,and ,,magnitude4 ,illustration3 ,fig4 #faj4--,polaris4 ,when we gaze up into the sky at night1 we see the stars twinkling far away1 and we may remark here that this twinkling of the stars is due to the atmosphere and the changes in its power of refraction1 and of course the star's light changes its direction4 ,but if we ascend in a balloon into very high and rarefied strata of the air1 we will find the twinkling less4 ,we have given the number of the stars according to ,flamstead1 but the larger the telescope the greater will be the number of stars we shall see1 numbers again being too far even for our perfected instruments4 ,but we can gain some idea of the magnitude of the stars when we consider the distance to arrive at1 which is a most difficult task1 for figures seem scarcely long enough to count the millions of miles1 and no instrument can detect the parallax4 ,even supposing the parallax to be a very small fraction of a degree we should get a result equalling trillions of miles4 ,,no4 #fa in ,cygni was at one time continually observed by ,professor ,bessel1 and he found that its distance--and it is the nearest star--is sixty-two and a half trillions of miles4 ,illustration3 ,fig4 #faa4--,the ,southern ,cross4 ,let us consider what this means4 ,light comes to us from the sun 7#ia1jjj1jjj of miles7 in about eight minutes1 and travels at the rate of something like #ahf1jjj miles in a second4 ,but even at that astounding rate the light from the star called #fa ,cygni took ten years to reach the earth2 and there are stars whose light has never yet reached the earth1 although the gleam may have been travelling at #ahf1jjj miles a second for thousands of years4 ,and we may presume that though we still see the light of stars1 some of them may be dead1 but the light left is still progressing to us through space4 ,so we must conclude that some stars which look large1 as do ,vega and ,sirius for instance1 must be enormous 8suns10 a great deal larger than our sun1 and the stars are each the centre of invisible systems just as our sun is the centre of the 8solar0 system4 ,vega is a tremendous star1 and shines with her own light as do all other visible stars2 for reflected light1 so very visible in the moon1 which is close to us1 would be quite invisible at such tremendous distances4 ,so we must call these stars 8suns10 and may add an apparently astonishing fact1 that our own sun is merely one of the stars in the ,galaxy1 or 8,milky ,way06 ,,chapter ,,xli4 ,,the ,,stars--7continued74 ,,double ,,and ,,multiple ,,stars--,,coloured ,,and ,,variable ,,stars--,,clusters1 ,,groups1 ,,and ,,nebul--,,the ,,galaxy1 ,,or ,,milky ,,way--,,how ,,to ,,find ,,out ,,the ,,principal ,,stars4 ,although not very clearly visible to the naked eye1 there are in the sky some pairs of stars very close together apparently2 but when these double stars are examined with a good telescope we find that though we fancy they are two stars very close1 in reality an immense distance separates them4 ,by ,vega1 which we have already mentioned1 there is apparently a star1 which on examination will be found really to be two stars4 ,it is also in the constellations of the ,lyre1 but of much lower magnitude than ,vega4 ,but in some instances there are three or four stars thus placed together1 and the frequency of the occurrence of this fact establishes the farther fact that these combinations are not accidental--that the stars are interdependent and physically connected4 ,illustration3 ,fig4 #fab4-- ,leonis4 ,there are now at least six thousand double stars known1#bg and this is a very small proportion of the forty millions or so of suns which are believed to exist in space4 ,but of these six thousand a larger proportion have been ascertained to be physically connected4 ,more than six hundred of these pairs are double suns1 while again there are other combinations of three and perhaps more4 ,when two are thus connected we have what are termed binary systems1 and when more are associated they are called triple and multiple stars4 ,an example of the last-mentioned class is the small star above mentioned near ,vega4 ,it is ,lyr1 and is a double of a double4 ,in ordinary telescopes this will not be perceived1 but with a high power the combination will be noticed4 ,the same phenomenon is observable in one of the stars of ,hercules and in ,andromeda4 ,the revolution of these double suns1 or binary systems1 has been closely observed1 and ,professor ,newcomb has given us a list of the binary systems of short period which are well determined4 ,these are as follows3-- #db ,coron #bf years4 ,herculis #ce years4 ,struve #c1aba #dj years4 ,coron #dj years4 ,sirius #ej years4 ,cancri #eh years4 ,urs ,majoris #fc years4 ,coron ,borealis #fg years4 ,centauri #gg years4 ,ophiuchi #ib years4 ,ophiuchi #if years4 ,scorpii #ih years4 ,it must be borne in mind that although these double stars appear close together from our standpoint1 they may be far apart--one behind the other in a straight line4 ,when such 8pairs0 exist they are known as optical pairs1 or optically double stars1 as distinguished from the actually physical 8pairs0 which revolve round the centre of a system4 ,in ,orion there has been discovered a regular system1 and the in ,orion1 which appears in a common telescope a moderate star1 and to the unaided eye only a speck of light1 is really composed of seven stars--four are set in the form of a trapezium1 as figured in the diagram in the margin by dots and asterisks4 ,two of these have been ascertained to possess attendants indicated by dots1 and a seventh star was discovered by ,lassell1 and ,humboldt remarks that in all probability this apparently tiny star in the constellation ,orion constitutes a real system1 for the five smaller stars have the same proper motion as the principal one4 ,illustration3 ,fig4 #fac4--,monocerotis4 ,illustration3 ,fig4 #fad4--,trapezium of ,orion 7,herschel74 ,thus our imagination almost fails to grasp the infinity of the systems with our single sun1 and with the distant double and even triple suns round which planets revolve perfectly independent of the other systems1 as we are independent of them possessing heat and light from their own sun or suns as we receive it from ours1 day and night seasons succeeding each other1 and the wondrous varieties of the light produced by the appearance or withdrawal of a sun or two in the firmament of those most distant planets4 ,these suns being double or triple would affect each other2 the composition of the light given forth would produce--as we may assume--varying effects4 ,we know something about the light of the stars by the spectroscope1 and the colours of stars are due to the vapour which takes away a certain part of the light emitted1 leaving the remainder to descend through the atmosphere to us4 ,binary stars are most numerous of the doubles2 for instance ,castor1 ,coron1 ,rigel1 ,polaris1 ,mivac1 ,leonis1 ,virginis1 ,urs ,majoris1 ,hercules1 #cf ,andromed1 ,ophiuchi1 and ,aquil4 ,the illustration in the margin is ,castor 7or ,geminorum71 the most northerly of the ,twins4 ,the ,coron is also figured1 as are ,polaris 7see fig4 #faj ante471 ,botes1 ,rigel1 and ,leonis4 ,the cuts herewith illustrate the relative positions at the periods named of the 8doubles10 and of the revolution of suns around other suns as mentioned4 ,as a consequence of their proper motion the binary stars appear to vary in their distances from each other1 as in the topmost of the three cuts on the 7opposite7 page representing ,virginis4 ,the stars have gradually approached each other1 and so are the stars in ,castor approximating1 and when they have closed1 and have appeared almost as a single star1 as they will do1 they will take open order again4 ,illustration3 ,fig4 #fae4-- ,coron4 ,illustration3 ,fig4 #faf4--;,botes4 ,illustration3 ,fig4 #fag4--;,castor4 ,illustration3 ,fig4 #fah4--,rigel4 ,the shortest time occupied by a double star in its revolution is thirty-five years1 and we have already given some of those which have been ascertained4 ,we will close this section with a few other examples4 ,for instance1 ,virginis revolves in one hundred and fifty years1 ,castor in two hundred and forty years1 #d ,aquarii in three hundred years1 #cg ,pegasi in five hundred years4 ,there are numerous other instances up to a period of three thousand years1 and about eight hundred of these binary systems are known4 ,we have mentioned that there are two or more suns in the multiple systems4 ,these suns are the cause of the different colours of the stars4 ,,colours ,,of ,,the ,,stars4 ,the question of star-colour follows naturally the consideration of the multiple stars2 for although single stars have been observed of a ruddy colour1 there are no instances of a blue or green one unattended by a companion4 ,this colouring has been attributed to the contrast between multiple stars1 for the colours are frequently complementary2 but investigation has shown that this cannot be the case4 ,for instances have been known in which1 when two are thus associated1 and one is concealed from us1 the other is just as bright1 and retains its former colour4 ,of course in cases in which colour is apparent to the unaided vision1 only the brightest stars betray colour4 ,antares1 ,betelgeuse and ,aldebaran are red 7orange7 colour4 ,sirius and ,canopus are white4 ,arcturus and ,capella are yellowish1 so is ,pollux4 ,vega is bluish-white4 ,these appearances are1 of course1 much more marked when the stars are examined through the telescope1 and telescopic stars--which are stars unobservable without a glass--are very much coloured1 and the multiple stars give us blue1 green1 violet1 and other tints1 besides those already mentioned4 ,again1 these coloured stars do not always remain the same colour4 ,sirius was once red2 ,mars was at times white4 ,spectrum analysis shows that the colours of many are due to absorption by the vapours of some of the rays2 and the existence of certain vapours may cut off some1 and at other times other vapours may exist and cut off other rays1 and so the colours may be changed4 ,struve gives the following list of binary complements of 8multiple0 stars3-- ,pairs consisting of a blue and white principal star #ec 8 8 and a light yellow principal star #eb 8 8 a yellow or red principal star #eb 8 8 a green principal star #af ,illustration3 ,fig4 #fai4--,position of the two stars of ,virginis499 ,illustration3 ,fig4 #fbj4--,position of the two stars of ,castor499 ,illustration3 ,fig4 #fba4--,position of the two stars of ,urs ,majoris499 ,we need scarcely pursue this question farther1 though many ideas concerning the coloured stars will arise in every thoughtful reader's mind4 ,supposing that every system has its sun or suns1 can we fancy the effects of a green or blue or violet sunlight--a light unmixed8 ,to employ the words of ,sir ,john ,herschel--8,it may be more easily suggested in words than conceived in imagination what variety of illumination two suns1 a red and a green1 or a yellow and blue one1 must afford to a planet circulating round either--or what charming contrasts and graceful vicissitudes a red and a green day1 for instance1 alternating with a white one and with darkness1 might arise from the presence or absence of one or other or both above the horizon40 ,,lost ,,and ,,new ,,stars4 ,we may have perhaps read the 8,lost ,pleiad10 and wondered what has become of the star supposed to have dropped out of the cluster so well known in the constellation ,taurus--the ,pleiades4 ,there are seven stars1 of which six are visible to the average eye1 and the ancients used to declare that one of the seven sisters 7the daughters of ,atlas and ,pleione7 hid herself because she had married a mortal1 while all her sisters wedded gods4 ,it is not improbable that one of the seven1 formerly distinguishable with the unassisted eye1 may have disappeared or been lost2 but it is certain that strong eyesight can see more than seven now1 and in the telescope there are about one hundred4 ,and it is a fact that some stars whose places have been carefully marked in the catalogue have subsequently disappeared4 ,many errors may have been made1 and stars put down where no star existed1 so a succeeding observer has not been able to find the star indicated4 ,but1 on the other hand1 we may admit that stars have been lost to sight1 and to compensate us for any such disappearances new stars are frequently observed1 and these are very remarkable phenomena4 ,about #aba ,b4,c4 ,hipparchus perceived a new star1 which was visible even in the daytime1 and on subsequent occasions others came into existence--viz41 in the years #ide1 #abfd1 and #aegb4 ,in the last-mentioned year ,tycho ,brah suddenly perceived the new star1 which was at first very brilliant4 ,it grew fainter and fainter1 after first gaining in intensity1 and disappeared entirely in #aegd2 and at other times stars have been seen which remained only for a short time1 and then disappeared4 ,the star discovered by ,tycho ,brah was seen by him when walking across the fields one night1 and he encountered peasants who were gazing at the new luminary4 ,it was so bright that it threw a shadow from ,brah's stick4 ,the new arrival appeared in 8,cassiopeia10 under the lady's chair1 forming1 as pictured in the diagram1 an irregular square4 ,the strange star is the largest4 ,illustration3 ,fig4 #fbb4--;,cassiopeia4 ,some stars exhibit extraordinary fluctuations1 and one discovered by ,mr4 ,birmingham in #ahff1 decreased rapidly and sank away to about the tenth magnitude1 and then got brighter1 and again diminished in splendour4 ,the 8,eta0 ,args has also been subjected to many fluctuations likewise1 and such alterations have gained for these luminaries the name of 8,variable ,stars40 ,in the accompanying little chart there will be perceived two particular stars1 named ,algol1 8the demon10 and ,mira 8the wonderful40 ,the latter is the most celebrated for its variable qualities1 and its cycle of change occupies nearly one of our years4 ,for a few days it appears very bright1 and then fades away for about three months1 to disappear for five months1 and then it reappears again1 increasing in brilliancy up to the second magnitude for another three months or so4 ,some people account for these phenomena by stating that the sides of the star being less luminous present the dark and light portions in rotation2 but we can give no satisfactory explanation of the reason1 unless it be caused by an aggregation of spots upon its surface1 like sun-spots on our sun1 or perhaps by eclipse4 ,illustration3 ,fig4 #fbc4--,star-,map4 ,illustration3 ,fig4 #fbd4--,nebul in ,pegasus4 ,illustration3 ,fig4 #fbe4--;,dumb bell ,nebul4 ,,star-,,clusters ,,and ,,nebul4 ,,nebul and ,,star-,,clusters are numerous in the heavens4 ,the most important are the ,great ,nebul in ,orion and in ,andromeda4 ,but there are other very beautiful 8patches0 of luminous matter or cloud appearances composed of minute stars invisible to the naked eye4 ,we annex specimens of the ,nebul1 one or two having been already inserted4 ,there must be thousands of these star-clouds1 and they have been classified by ,sir ,john ,herschel from ,sir ,william's discoveries as follows3-- 7#a7 ,clusters of stars1 in which the stars are clearly distinguishable1 divided again into regular and irregular clusters4 7#b7 ,resolvable ,nebul1 which may be separated into distinct stars under powerful telescopes4 7#c7 ,nebul1 in which there is no appearance whatever of stars1 divided into classes according to brightness1 etc4 7#d7 ,planetary ,nebul4 7#e7 ,stellar ,nebul4 7#f7 ,nebulous ,stars4 ,we learn also from the foregoing authority that ,nebul affect a certain district2 that is1 they have1 as it were1 a preference for it1 and are not distributed in a random manner over the heavens1 and are found in ,leo1 ,leo ,minor1 ,ursa ,major1 ,canes ,venatici1 ,coma1 ,botes1 and ,virgo1 and more sparingly in ,aries1 ,taurus1 ,orion1 ,perseus1 ,draco1 ,hercules1 ,lyra1 etc4 ,nebul are found associated with stars1 as is the case with ,argus2 these are called nebulous stars1 and in the case of this particular star many very interesting investigations have been made4 ,the ,nebul are as equally variable as the stars they surround4 ,illustration3 ,fig4 #fbf4--,nebul in ,perseus4 ,what is termed the ,nebular ,hypothesis was put forward by ,la ,place1 and by it he endeavoured to account for the regular development of the stellar system1 which is supposed to have originated from an immense nebular cloud4 ,this immense mass would rotate and contract1 and the outer portions would separate and develop in rings like ,saturn's rings4 ,then the rings break into separate portions1 and each portion condenses into a planet1 or the small 8bits0 travel round the sun like asteroids1 and in this manner various systems were formed4 ,this theory was considered to be quite exploded when stars were discerned in nebul by the more recent telescopes2 but then the spectroscope came to our aid1 and it was discovered that there were some nebul which are simply masses of glowing gas or aggregations of stones which are dashing against each other in so forcible a manner as to produce heat and luminosity4 ,mr4 ,lockyer appears to favour the latter theory as to nebul4 ,illustration3 ,fig4 #fbg4--,nebul in ,canes ,venatici4 ,mr4 ,proctor1 however1 has put forward a hypothesis that the star or meteor showers are the original cause of the sidereal system1 and this rain of meteors has fallen for all time1 gradually consolidating into orbs4 ,the fact that the constituents of sun1 earth and planets1 comets and meteors being fundamentally the same lends probability to this hypothesis1 which is fully explained by the author4 ,,the ,,milky ,,way4 ,the ,galaxy is familiar to all readers1 and although visible all the year round1 is perceived more plainly in ,august1 ,september1 and ,october1 or at the beginning and ending of that period4 ,this zone of stars was of course well known to the ancients1 but it is to ,galileo that we owe the first important information about the ,galaxy2 he decided that it was formed of stars4 ,sir ,john ,herschel investigated the subject very closely1 and to him much of the information concerning the ,milky ,way is due4 ,it is not very distinct in the north1 but as it advances from ,cepheus southwards by the ,unicorn1 it gets clearer1 and opens out in ,argo1 and descends still south1 becoming brighter near the ,southern ,cross4 ,it then passes northward again1 dividing into two branches1 one of which dies out1 and then over ,sagittarius1 and so on to ,cygnus1 then to ,casseopeia and the starting-point4 ,the number of stars in the ,galaxy is about #ah1jjj1jjj4 ,illustration3 ,fig4 #fbh4--,the ,milky ,way4 ,in this wonderful zone of stars the centre of our system1 the sun1 is placed4 ,it was supposed to be divided as in the diagram above2 the inner portion being the stars seen in their thickness1 and the outer ring representing the stars viewed in the direction of the length and breadth4 ,but afterwards1 ,herschel modified his opinions respecting the ,milky ,way1 and since his death many astronomers--and ,mr4 ,proctor more particularly--have devoted considerable time to an examination of this wonderful zone of stars2 which1 it must be remembered1 is not a continuous stream2 it is a series of luminous patches4 ,on this point ,professor ,nichol says3-- 8,it is only to the most careless glance that the ,milky ,way appears a continuous zone4 ,let the naked eye rest thoughtfully on any part of it1 and if circumstances are favourable1 it will stand out rather as an accumulation of patches and streams of light in every conceivable variety of form and brightness2 now side by side1 now heaped on each other1 again spanning across dark spaces 444 and at other times darting off into the neighbouring skies in branches of capricious length and shape1 which gradually thin away and disappear40 ,the ,milky ,way has its greatest breadth in the 8,swan10 and in the 8,eagle0 constellation it divides itself4 ,in the 8,southern ,triangle0 the zone is brightest1 and in the 8,southern ,cross0 the hole or space1 termed by sailors the 8,coal ,sack10 is very distinct4 ,it then contracts and expands1 and there is in ,argo another gap4 ,then it is lost for a space1 then it branches out1 and soon crosses the ,equator1 dilates1 contracts1 opens out again1 and so returns to the 8,swan0 again4 ,philosophers have frequently discoursed upon this phenomenon1 but all statements must remain more or less speculative4 ,from ,kepler's to the present time astronomers have been considering the ,milky ,way1 and when the ,nebular theory was given up1 when the ,galaxy was found to be composed of stars1 there was1 as we have noticed1 the idea of the ring and the cloven disc4 ,mr4 ,r4 ,proctor has likened the ,galaxy to a coiled serpent1 and considers the openings in the ,milky ,way as evidence that the stratum of stars is limited1 and that here we can see beyond it4 ,in fact1 it would appear that it is a very complicated question2 and as the zone itself is complicated 8with outlying branches beyond the range of our most powerful telescopes10 so an actual knowledge of the ,milky ,way is beyond us at present4 ,it is composed of most extraordinary aggregations of stars1 which appear not only impossible to count1 but each one to be independent of the other4 ,thus we must conclude our rapid survey of the ,milky ,way1 and close with ,mr4 ,proctor's remark in his 8,universe of ,stars40 8,the sidereal system10 he says1 8is altogether more complicated1 altogether more varied in structure than has hitherto been supposed4 ,within one and the same region co-exist stars of many orders of real magnitude1 the greatest being thousands of times larger than the least4 ,all the ,nebul hitherto discovered1 whether gaseous or stellar1 irregular1 planetary1 ring-formed1 or elliptic1 exist within the limits of the sidereal system4 ,they all form part and parcel of that wonderful system1 whose nearer and brighter parts constitute the glories of our nocturnal heavens40 ,and a little reflection will show how true this is4 ,not very long ago in the world's life the solar system was supposed to consist of one sun with a few planets wandering around him4 ,then some more were found1 and they were called 8satellites40 ,for a long time man fancied he had reached the 8ultima thule0 of astronomy in these depths2 but the whole idea was changed when it was discovered that beyond ,mars there lie the asteroids and the host of bodies in this solar system which we cannot do more than allude to4 ,then when we consider that this 8sun0 of ours1 which we think so enormous1 and which keeps in subjection so many heavenly bodies1 and illuminates them2 when we reflect that there are in space1 and visible1 stars many times larger than our ruling star1 each a sun1 and that our sun would1 if put where the great ,sirius glows1 be but a speck in the firmament1 and his system invisible to our eyes1 we may well wonder at the magnitude of the subject1 and the ,infinite ,wisdom and ,power 8that telleth the number of the stars1 and calleth them all by their names40 ,,how ,,to ,,read ,,the ,,sky4 ,a few particulars1 to enable a reader to identify the most prominent stars1 may be given as starting-points from which some few excursions into the spangled heavens may be attempted4 ,but the suggestions must be considered with reference to the ever-varying directions of the supposed lines in consequence of the daily revolution of the sphere4 ,we have illustrated this in the cut in the margin1 wherein the ,lesser ,bear is shown as swinging round the ,polar ,star in different positions4 ,sometimes the lines of direction will be vertical1 sometimes inclined1 but all retaining their relative positions4 ,illustration3 ,fig4 #fbi4--,the 8,swing0 of the ,lesser ,bear4 ,we have already learnt that the 8pointers0 of the ,great ,bear indicate the ,polar ,star in the ,lesser ,bear1 and we can 7roughly7 estimate the distance between the pointers as #e4 ,this will give us the distance between the pointers and the ,polar ,star as #bi4 ,by following an imaginary line through the two northern stars of the 8,waggon0 7the ,bear7 away from the 8horses10 we shall find ,capella about #ej away4 ,illustration3 ,fig4 #fcj4--;,diagram of the ,pole ,star4 ,if we pass from the first star next the waggon of 8,charles's ,wain0 to the ,pole ,star1 and past it1 we shall arrive at an irregular ,w4 ,this is ,cassiopeia1 about as far beyond ,polaris as the ,bear is below it4 ,when the latter is low1 the former is at the zenith1 and so on4 ,a line drawn from the ,pole ,star through the end star of the ,great ,bear leads to ,arcturus4 ,a line taken from ,arcturus for about an equal distance will1 with the ,pole ,star1 make a triangle with ,vega4 ,the ,polar ,star may be called the ,apex4 ,regulus may be found southwards by drawing a line through the two first stars of the square in the ,bear 7opposite the pointers74 ,from ,vega1 almost opposite the ,pole ,star1 and through it about twice as far away on the other side1 is ,sirius1 a brilliant 8sun40 ,procyon will be found to the westward of ,regulus about #cj4 ,from ,procyon to the ,pole ,star a line will pass through ,pollux and ,castor4 ,another line from the pole star through the middle of the three 8horses0 in the 8,wain0 will reach ,spica ,virginis about #gj beyond4 ,so we can describe a large triangle with ,spica1 ,regulus1 and ,arcturus1 at the angles4 ,regulus is the apex1 ,spica and ,arcturus a short base line4 ,illustration3 ,fig4 #fca4--;,diagram of ,sirius1 etc4 ,from the pole star through ,capella1 passing between ,betelgeux and ,bellatrix1 we shall describe a line leading to the three stars of ,orion's belt4 ,between it and the ,pleiades is ,aldebaran4 ,there are many other stars which could be indicated2 but on a fine evening1 if the observer will mark them upon a piece of paper1 placing the pole star in the centre1 he will be able to add to his star map very rapidly4 ,in the foregoing chapters of ,astronomy we have seen how the earth and other planets move around the sun2 we have glanced at the 8fixed0 stars and their groups1 termed the constellations1 and have noted the planets and their characteristics1 with many other interesting facts4 ,there is yet a great deal to be learnt1 and much study will be required with daily 7nightly7 observations before the young reader will obtain success as a student of astronomy2 but there is no study so interesting4 ,we have seen what a very small portion of the universe is occupied by our solar system1 and what a speck our earth is on the plain of creation4 ,we find ourselves on the border-land of the incomprehensible1 and we are lost in speculations upon the unseen4 ,,footnotes3 #bg ,mr4 ,burnham has lately given a list of two hundred and fifty-one new double stars1 and in the ,astronomical ,society's proceedings there is a list of ten thousand4 ,,chapter ,,xlii4 ,,new ,,astronomical ,,appliances4 ,a ,,celestial ,,indicator--,,astronomical ,,or ,,cosmographical ,,clock--,a ,,simple ,,globe--,a ,,solar ,,chronometer4 ,having said something concerning astronomy1 we will give a few instructions respecting the instruments not already described1 and make some observations1 supplementing our directions in the previous chapter1 for many people will be glad to learn how to read the evening skies4 ,here we have an apparatus which will prove useful to amateurs2 it is a sort of celestial indicator by ,mauperin1 and will facilitate the finding of every star or constellation1 when the apparatus has been made ready by pointing the rod1 ,t1 in the direction of the object it is desired to view4 ,this rod is mounted upon a rod1 ,s1 and is movable upwards or downwards or sideways1 and in the last-named movement it will carry with it an indicator1 ,i1 which slides over the chart or diagram of the heavens4 ,the two arms of this indicator are always parallel to the plane of the rod1 ,t1 no matter in what position they may be on the chart or the inclination of the rod4 ,the extremities of this rod are terminated by an eye-slit1 and by a crescent respectively4 ,when the apparatus is set1 all one has to do is to look through the eye aperture1 ,o1 and view the star which we have chosen in the centre of the crescent1 ,c4 ,this star will be found named in the space between the arms of the sliding indicator1 ,i4 ,it is easy to perform the operation inversely--that is to say1 to find in the sky1 by means of the sighting-rod1 ,t1 the stars we have chosen on the chart between the prongs of the indicator4 ,the chart represents exactly the heavens as we see them1 and this new mode is opposed to the manner generally adopted with celestial charts1 and is very important1 for it obviates the necessity of holding the map above one's head1 its face downwards4 ,as we have already showed1 it is not difficult to find the ,polar ,star and the ,great ,bear4 ,the latter is readily recognised by its seven stars1 and the ,lesser ,bear glides around the pole as shown in the diagram on the preceding page 7fig4 #fbi74 ,now let us see how the celestial indicator will work4 ,let us take the apparatus into the open air1 and place it upon its tripod stand4 ,the upper portion will be found movable by loosening the screw1 ,v4 ,by another simple arrangement the table can be slanted1 and by turning a screw we can entirely slope the side of the chart where midnight 7minuit7 is written4 ,being placed opposite the polar star we take the upper part of the chart by the button1 ,g1 and bring it before us by a horizontal rotative movement4 ,illustration3 ,fig4 #fcb4--;,celestial ,indicator4 ,we now place the sliding indicator upon midday 7midi71 and keep it in that position while working the apparatus--that is1 until we have caught sight of the polar star in the centre of the crescent1 ,c1 by means of the eye aperture1 ,o4 ,we have now obtained the meridian1 and care should be taken to tighten the screw1 ,v4 ,then the table is raised to its fixed place upon the support2 it is regulated according to the latitude of the place1 and the apparatus is then 8oriented40 ,the upper disc is an elliptical opening1 or aperture1 which contains for every moment the stars visible upon the horizon1 and the circumference is furnished with a graduated scale of hours divided into five-minute divisions1 and this is fixed upon the apparatus4 ,the dotted line between the midday and midnight points gives the meridian4 ,the disc placed underneath is the celestial chart1 on the circumference of which we shall find the days of the months4 ,it can be moved around the rod1 ,s1 which represents the axis of the earth around which the heavens are supposed to revolve4 ,when the stars have to be observed1 the day of the month has to be brought to the time at which the observation is about to be made4 ,we can easily read off the chart by looking through the eye-piece as already explained4 ,every five minutes it is necessary to move the chart one division1 which indicates that five minutes have passed2 7other stars are1 of course1 arriving74 ,the apparatus can be packed away when done with1 or the bearings taken1 and then the trouble of getting it into position again need not be repeated4 ,a small lamp1 ,l1 throws its light upon the chart in such a way that the eyes of the observer are not incommoded1 while the table is fully illuminated4 ,it can be placed at ,l if necessary4 ,the inclination varies according to the latitude of the place when the observations are made4 ,there is an arrangement underneath which admits of this inclination according to longitude4 ,the apparatus can also be made available to ascertain what the aspect of the heavens will be upon any particular evening of the month4 ,we have only to place the chart at the day and hour1 and we shall then see upon it all the stars visible above the horizon4 ,we can thus find out at what time the stars rise and set1 and those which do not set--to find the hour at which they pass the meridian 7the line drawn between midday and midnight upon the chart71 and the time of their appearance on the horizon4 ,when the sliding indicator1 ,i1 does not show a star that is discoverable in the sky1 the observer may conclude that he is viewing a planet4 ,this apparatus is well adapted for beginners in astronomy1 as no deep preparatory study is necessary1 and the tyro can read the sky as easily as he could read a book4 ,a ,,cosmographical ,,clock4 ,we have1 in the foregoing chapters upon ,astronomy1 endeavoured to give the reader some idea respecting the inclination of the earth and its rotation1 and writers have often endeavoured to devise an apparatus which shall show the position of the globe in space1 its diurnal motion--even its inclination and the succession of seasons in its revolution round the sun4 ,but such reproductions of simultaneous movements have hitherto been obtained only on a very large scale1 which find their place well enough in the museum or lecture-room1 but which it is quite impossible to utilize in our sitting-rooms1 on our tables1 or chimney-pieces4 ,besides1 the usual apparatus employed is a very costly one1 and only serves for occasional representation2 it will not keep the facts constantly before the observer in the manner of a clock showing the time4 ,but for all who are interested in ,astronomy1 or in ,cosmography1 or even for a young person who desires merely to understand the reality of the earth's motion and how our earth is placed in the universe--for any one who deems it of use that he or she should be able to see the signs and the seasons1 and the days and years1 and how the earth revolves1 may obtain an astronomical or cosmographical clock1 which will tell him or her how the 8world wags02 a useful as well as an ornamental timepiece4 ,now this is precisely the result which the talented inventor of the astronomical clock has arrived at4 ,m4 ,mouret devoted a great portion of his life and all his available means to the realization of his great idea1 and1 sad to say1 he died miserably in an attic the very day before his great and deserving effort brought him the reward for which he had so painfully striven and devoted himself to by a life of self-denial and labour4 ,illustration3 ,fig4 #fcc4--;,cosmographical clock4 ,m4 ,mouret communicated to his globe the astronomical movement1 which our earth possesses1 by the aid of clock-work1 which conveys to it1 second by second1 at each stroke of the pendulum1 the double movement of rotation and progression4 ,the globe turns upon its axis in twenty-four hours1 and thus one can perceive1 without any mental effort1 the rotation of our planet1 and the portions of the globe which come under the influence of the sun in rotation1 just as they do actually on the earth4 ,not the least interesting attribute of this ingenious arrangement is the fact that during breakfast or dinner one can see the displacement and revolution of the earth with reference to the sun to all people in the world4 ,here1 on the meridian1 all are at midday4 ,there1 on the left1 near the circle which defines the limit between day and night1 the sun is rising and day is beginning2 opposite1 on the right1 the sun is setting and day is closing4 ,yonder is the ,pacific ,ocean in full daylight1 while almost every continent is in darkness and the inhabitants wrapped in slumber4 ,now the ,chinese are opening their eyes1 and the ,asiatic and ,european continents will soon be illuminated and awake4 ,this is the movement of the world as it has ever been since time came into its calculations4 ,the ingenious inventor1 who wished to make a clock of his apparatus1 and not being able to change its place on the earth from day to day as the time changed1 very cleverly reproduced the sun's movement of declination by making it describe a double cone at the axis of the globe4 ,at the equinoxes the poles are in a plane1 and equal day and night are shown4 ,at the winter solstice the north pole is inclined backwards at an angle #bc #bh1 and our hemisphere is in the winter season4 ,we have then only eight hours' daylight and sixteen of darkness2 six months later the pole is inclined towards the sun1 and the southern pole is plunged in darkness4 ,we have the long days and the southerners the long nights4 ,an upright dial shows the time of the country in which the globe may happen to be1 and one can ascertain at any moment what time it is anywhere else4 ,a horizontal dial indicates the day of the month1 and changes every day in a manner corresponding with the movement of the earth around the sun1 reproduced by means of the arrangement with the double cone4 ,the spectator is supposed to be turning his back to the sun4 ,we may add that these movements are all self-acting1 and there is no need to interfere with the clock1 which is wound up like ordinary timepieces4 ,by an ingenious forethought the inventor provided that the sphere should be independent of the other movements1 and it can be used for demonstration in the hands of the lecturer1 and be explained with all its motions without in any way disarranging the clock-work4 ,the globe must1 of course1 when replaced1 be put exactly at the correct day and hour4 ,a ,,simple ,,terrestrial ,,globe4 ,a terrestrial globe without any mechanism1 so long as its axis is parallel to that of the earth1 exposed to the direct rays of the sun1 represents our planet with its recurrence of day and night4 ,the figure 7#fcd7 shows us a globe without any support4 ,the axis is north and south1 and makes1 with the horizon1 an angle equal to the latitude of ,paris1 if the support1 ,a ,b1 be horizontal4 ,to make the axis of the globe parallel to the axis of our earth1 the line1 ,n ,s1 must correspond to the meridian of the place2 this can be done with the compass1 for instance4 ,the solar rays always illuminate one-half of a sphere1 no matter what its dimensions4 ,if we look at the illustration we shall see that the line of separation between the light and dark portions of the globe corresponds with that in our earth4 ,this globe1 then1 tells us the passage of light and darkness for the day1 and even for the moment of the day1 when it is turned as the earth moves4 ,the place examined should be placed in the meridian of that place 7,paris1 for instance71 and occupy the most elevated spot on the globe4 ,the earth is then in just the same position1 and daylight and darkness are shown exactly as they exist on the earth at the time4 ,if this globe be then observed for a few minutes1 the sun will be seen rising and setting1 as it were1 in various places 7we must remember we have concentrated the sun's rays1 not a lamp1 upon the globe74 ,the places on the right1 if the observer be placed facing the sun1 will come out of the shade1 and those on the left will enter it4 ,the former are then really enjoying the sunrise1 and the others are actually witnessing his setting4 ,the globe represented1 making the double revolution of our planet in the year1 will reproduce all the actual phenomena of day and night as taking place on the earth itself if we stand at a little distance so as to observe it all at once4 ,illustration3 ,fig4 #fcd4--;,a simple terrestrial globe4 ,of course1 the employment of this simple apparatus should not exclude more complicated ones1 for the former can only be used on a fine bright day4 ,but the advantage claimed for it is that in it we can imitate nature exactly4 ,illuminated1 as it is1 by the real sun1 the portions of light and shade are indicated by the rays and not by a metallic circle4 ,in order that the line of demarcation may be exactly defined1 it will be necessary that the sun's rays be concentrated upon the globe1 and that no lateral or vertical light be admitted4 ,the curtains should therefore be so arranged1 and the blinds pulled down to a certain point1 and if the stand or support be painted black it will be found an advantage4 ,if the globe be a small one1 it will be sufficient to place the stand upon an ordinary table1 without verifying the horizontal plane4 ,with a large globe the arrangement must be very exact4 ,a ,,solar ,,chronometer4 ,m4 ,flechet's chronometer1 of which we give an illustration1 is a kind of equitorial reduced to its most simple form4 ,it is possible to ascertain the exact time by it very easily4 ,it consists of a disc1 ,,ab1 divided into twenty-four hours and fractions of hours4 ,this disc turns upon itself around an arc1 ,,cd1 which has a direction parallel to the axis of the world1 and can be moved on a joint1 ,e1 according to the latitude of the place2 ,f is a lens which can be moved and presented to the sun at any time1 forming the centre of a concave and exactly spherical plate represented at ,,gh4 ,illustration3 ,fig4 #fce4--,solar chronometer4 ,when the instrument is fixed so that the axis1 ,,cd1 is parallel to the axis of the globe1 the disc1 ,,ab1 is turned so that the centre of the image of the sun1 produced by the lens1 shall fall at m4 ,the real time is found by an examination of the position of the index1 ,a1 upon the hour graduations of the disc4 ,a ,french writer1 ,ch4 ,delounay1 has mentioned this instrument1 and considers it easy of arrangement1 exact in time1 and very useful4 ,,chapter ,,xliii4 ,,physical ,,geography4--,i4 ,,geology4 ,,geography ,,and ,,geology--,,the ,,earth',s ,,crust--,,origin ,,of ,,the ,,earth--,,denudation ,,and ,,excavation ,,by ,,water--,,rocks1 ,,gravel1 ,,and ,,sand--,,classes ,,of ,,rocks4 ,illustration3 ,fig4 #fcf4--;,cliffs worn by the sea4 ,when we were at school1 and learnt the various countries of ,europe1 we had maps showing us the several divisions of one realm from another2 the mountains1 lakes1 and other prominent features of the continent were learned and repeated1 but we1 maybe1 seldom1 perhaps never1 bestowed a thought upon the formations of the mountains1 and the manner in which rivers ran down into and through lakes to the ocean4 ,there were the mountains1 there were the lakes and rivers1 and capes1 and headlands1 and there they are still1 to all intents and purposes1 the same to see1 to climb up1 to sail down1 as the case may be4 ,but the map of ,europe has undergone a visible change4 ,territory has changed hands4 ,germany has gripped ,france1 ,england has got ,cyprus1 ,turkey has been dismembered1 and ,austria is annexing territory4 ,this study is called ,geography1--,,political ,,geography1--for it marks the political boundaries4 ,the knowledge of the formation of hills1 headlands1 lakes1 rivers1 seas1 their causes1 constitution1 and effects1 how they rose1 how they exist and wax or wane during the course of centuries is ,,physical ,,geography1 which we propose to consider4 ,this tree of knowledge includes some very important branches1 almost parent stems4 ,as a magnificent oak spreads forth its brawny arms1 with smaller branches and twigs1 each of these great branches being as large as an ordinary tree1 so ,physical ,geography includes other arms such as ,geology1 ,meteorology1 ,botany1 and ,physiology--even ,astronomy in its comprehensive embrace4 ,we find it is a difficult task to separate these kindred sciences from the great tree4 ,we may have therefore to refer to earth1 air1 and water1 and their various forms in hills and mountains1 wind1 vapour1 rain1 glaciers1 and sea4 ,we must learn how this earth has been gradually cooled1 and what the various stages of its growth have done4 ,we must consider plant and animal life upon our planet1 and how the atmosphere affects them4 ,all this is ,physical ,geography1 and its satellite sciences of ,geology1 ,meteorology1 8,climatology10 ,botany1 and ,physiology4 ,illustration3 ,fig4 #fcg4--;,disintegrated granite4 8,everything must have a beginning10 and the earth must have had a beginning1 although the actual manner of the physical creation of the planet is a disputed fact4 ,we are not about to discuss the religious side of the question1 although we should undoubtedly find that ,biblical and ,geologic teaching run side by side towards the same end1 and the testimony of the earth and sky bears witness to the ,divine hand that created the universe1 which we can trace back to the dim and distant ages when 8the earth was without form and void1 and darkness was upon the face of the deep40 ,with this brief preface1 let us consider some of these aspects1 and pick up interesting facts from the ground4 ,,geology4 ,in the chemical and mineral sections of this volume we have heard something concerning the formation of the globe and its composition1 its clays1 rocks1 etc4 ,with these internal arrangements ,chemistry and ,mineralogy have dealt4 ,geology tells us about the external surface of the earth1 its stones and rocks1 and how they were formed1 and generally something about the conformation of the crust of the earth1 and its history4 ,when we speak of 8crust0 of the earth1 we do not simply mean the exterior layer of gravel1 clay1 or stone4 ,the crust is a thick one1 and our crust extends just so far as we can cut into it4 ,the surface of the sea can scarcely be termed a crust1 but we must penetrate that ever-moving liquid boundary1 and touch upon 7and examine7 what lies down below far beyond the 8full fathom five0 of the lead line4 ,in this study we must not forget our ,book of ,nature1 which is always open and inviting us to read4 ,we shall see how things are produced1 and how our physical surroundings will continue to be produced until the age of miracles returns1 and ,providence sees fit to interfere with the otherwise immutable laws which ,he in ,his wisdom has laid down for the universe4 ,it will be of no use to go back into space and imagine the world a red-hot fragment of matter1 whirling through the heaven around the sun which1 as a larger aggregation of burning atoms1 kept it1 as it now keeps it1 in its place4 ,the earth was a globe of liquid fire1 or in gaseous state1 and the atoms gradually cooled on the surface2 the fire is still under our feet4 ,the outer part would by degrees lose all its heat1 while the interior remained hot2 the planet must then have been surrounded by a steamy atmosphere1 and enveloped in vapours condensed from the air through which no light of the sun could by any appreciable degree penetrate4 ,we can give an example of this1 and it will be seen how the surface of the earth gradually became formed from the vaporous condition4 ,if any one will take the pains to evaporate any saline solution in a capsule till it is about to crystallise1 and observe attentively the pellicle of salt as it forms on the surface2 first a partial film will show itself in a few places1 floating about and joining with others1 then when nearly the whole surface is coated1 it will break up in some places and sink into the liquid beneath1 another pellicle will form and join with the remains of the first1 and as this thickens it will push up ridges and inequalities of the surface from openings and fissures in which little jets of steam and fluid will escape2 these little ridges are chains of mountains1 the little jets of steam those volcanic eruptions which were at that period so frequent1 the surface of the capsule is the surface of the earth1 and the five minutes which the observer has contemplated it1 a million years4 ,the next effect of the cooling of the earth would be the gradual condensation of the vapour of water with which it was surrounded2 this falling upon the earth formed seas and oceans1 leaving only the higher portions exposed above its level4 ,the clearing up of the dense dark clouds for the first time let in upon the earth's surface the glorious and vivifying rays of the sun1 and this great effect possibly accords with the earliest record in the ,bible of the acts of creation3 8,and ,god said1 let there be light1 and there was light40 ,this clearing up of the vapours and the subsequent rain no doubt gave rise to terribly grand electrical phenomena--thunderings and lightnings4 ,by degrees the waters got their own way1 and then many changes took place1 land and water fighting1 as it were1 for the mastery1 as they are fighting to this day4 ,but perhaps some reader may not think that the land and water of our earth are thus engaged4 ,a very few minutes' reflection will suffice to confirm our assertion4 ,look at the lofty crags in the ,alps1 for instance2 what has shattered those peaks1 and sent the masses toppling down in stone avalanches to the lower slopes1 and then into the valleys8--,water4 ,water has been in the crevices1 and was frozen there2 in freezing it expanded and loosened the crags1 which1 forced asunder1 gave an opening to more snow and ice1 and so this powerful leverage1 aided by the wind and storm1 is disintegrating our mountains4 ,illustration3 ,fig4 #fch4--;,breakers on the coast of ,cornwall4 ,it is the same by the seashore2 the cliffs are wearing away1 and the sea approaches2 at other places the sea recedes from the land1 as coral formation and embryo chalk cliffs are rising under the surface of the ocean4 ,lakes dry up1 and the meadow or farm arises on the site1 while other old spots are submerged4 ,no rest1 no change of idea1 but ever changing in physical appearance1 ,nature goes on her wondrous way1 working now as steadily1 as harmoniously1 and as surely as she did before time was1 and as she will continue to do when time shall be no more6 ,in our investigations into ,geology we cannot enter into many technical details4 ,our object in these pages is recreation2 but we shall1 even under these circumstances1 find plenty to interest1 and sufficient to lead any one who wishes to pursue the study for himself4 ,we will endeavour so to put the features of the stones and rocks before him that they will be recognized by the passer by4 ,we will try to show how the earth has been built up1 and how the great and terrible changes through which our little globe has passed have been effected4 ,in our own islands1 ,great ,britain and ,ireland1 we shall find traces of all the materials likely to be useful to us in our quest1 ,as has been well said1 8,geology is the ,physical ,geography of the past40 ,,constitution ,,of ,,the ,,earth4 ,illustration3 ,fig4 #fci4--,shells in chalk4 ,the descent from rocks to stones1 from stones to gravel1 from gravel to sand1 is evident to everyone1 so we need not insist upon the fact that sand is powdered rock1 and that an aggregation of sand particles makes stones4 ,we have heard in the ,mineralogy section that there are certain 8earths0--silica1 alumina1 lime1 etc4 ,of these 8earths10 the two former constitute the greater portion of the ,,rocks4 ,lime1 also1 is very evident1 and in limestones fossils or organic remains are abundant4 ,now we must entirely put away from our minds the old idea that the earth we live on was created at once1 or as it appeared to the first human beings4 ,our planet was prepared for man by degrees during millions of years4 ,we conclude that the earth was originally composed of certain elements1 and we find the same elements in the sun4 ,therefore1 supposing 7as is supposed7 that the earth came from the sun1 we have all the material of the globe in a fused state4 ,as the earth cooled1 rocks were formed by pressure1 and then water came1 and now we can read 8books in the running brooks1 and sermons in stones0 at our leisure4 ,illustration3 ,fig4 #fdj4--,the streamlet4 ,perhaps as someone reads this he may be walking by the seashore kicking the pebbles or seated upon the sands1 the grains of which are so very tiny4 ,he will probably find sand1 shingle1 and gravel within reach1 and perhaps the curious-looking 8pudding stone40 ,now what can we learn from these stones or sand grains or that curious bit of conglomerate8 ,perhaps the reader may be at ,ramsgate or ,margate or another place where the 8white cliffs of ,albion0 glisten in the sun4 ,take up a piece of chalk and examine it4 ,it is soft and soils your hands1 and you will throw it away1 perhaps--but don't4 ,take it home and put it under the microscope or a good magnifying glass4 ,what do you see8 ,illustration3 ,fig4 #fda4--;,cliffs showing strata4 ,you will find the remains of animals--that is1 shells and tiny bits of coral packed close together4 ,under the microscope they will become more separated1 and the grains will be distinct fragments of shells1 etc4 ,if this little bit of chalk be composed of marine animals' shells1 of course the whole cliff is composed of the same kind of material4 ,but how did the shells get into the chalk8 ,shells are chalk--carbonate of lime2 lime was deposited at the bottom of the sea1 and the infinite millions of minute animals formed themselves shells1 and left them to be piled up by ,nature's forces into cliffs during countless ages4 ,illustration3 ,fig4 #fdb4--,limestone with encrinites4 ,yes1 but how did the lime get into the water to make the shells8 ,we will endeavour to explain4 ,rain1 when falling1 takes some carbonic acid from the air1 which we know contains it4 ,this acts upon the lime in the rocks 7lime is oxide of calcium1 and calcium is an element in the earth71 so we get a bi-carbonate of lime 7soluble in water71 which rises from the rocks in springs4 ,these springs and their streams deposit lime1 as we can see in caverns where we find stalactites and stalagmites4 ,the lime is transmitted to the ocean1 and absorbed by the crinoideans and molluscs which produced shells4 ,these shells hardened and crystallized became limestone1 and whole mountains are formed of this 8organic0 rock1 which is used for so many purposes4 ,we have spoken of ,,organic ,,rocks1 but there are others1 and we ought1 perhaps1 to have spoken of that kind before the chalk put them aside4 ,let us go back to our sandy shore again and look at the ,,sedimentary ,,rocks1 which are the very first formation4 ,we have all seen sandstone1 and visitors to the ,south ,devon ,coast will remember the red cliffs near ,dawlish and ,teignmouth4 ,these are red sandstone--not the very 8old red0 so pleasantly written of by ,hugh ,miller1 but at any rate sandstone1 and composed of grains of sand4 ,when we were at ,dawlish last year a piece of the sandstone had fallen on to the beach1 and when the waves came up that stone was no doubt gradually washed away into sand1 and then fell to the earth as sediment4 ,illustration3 ,fig4 #fdc4--;,chalk cliff4 ,we said something a few pages back about the wear and tear which is always going on3 the mountain is worn away--a mass falls1 it is broken into smaller pieces2 these are carried by a river2 the mud is deposited1 and the finer particles are ground and rounded into gravel1 and finally sand4 ,beneath the current of the river1 and at the bottom of a lake or sea1 these sediments 7mud1 etc47 accumulate one on the top of the other in regular series called strata1 and then the weight and pressure acting with the soluble mineral deposits always washing down1 consolidate and bind the loose sand-grains into stone1 which1 in the course of ages1 hardens4 ,the stones thus formed from sediments such as gravel1 mud1 and sand1 are termed ,sedimentary ,rocks2 they have become rocks by enormous and continuous pressure4 ,thus3-- ,sands have become 8,sandstones02 ,gravel has become 8,pudding-stone0 7,conglomerate72 ,mud and clay have become 8,shale02 ,calcareous deposits have become 8,limestone02 ,vegetable deposits have become 8,coal40 ,so we have sandy1 clayey1 limy1 flinty1 and corally rocks under long names respectively--,arenarious1 ,argillaceous1 ,calcareous1 ,silicious2 and we may add ,bitumenous and ,ferruginous--,irony ,rocks--to the list4 ,speaking of sediments1 it is curious to note the different colours of the ,arve and the ,rhone which meet near ,geneva4 ,the white sedimentary ,arve can be traced for a long distance beside1 not mixing with1 the blue ,rhone4 ,the same effect can be traced where the latter river enters the ,lake of ,geneva4 ,so the land is being perpetually carried away and deposited2 and where water gains on land there is somewhere else always a corresponding elevation to compensate it4 ,thus places disappear1 and the sea washes over the site1 as on the ,kentish ,coast1 where ,earl ,godwin's land was inundated1 and new land is reclaimed or is elevated from the sea to make up the balance4 8,there rolls the deep1 where grew the tree2 ,oh1 earth1 what changes hast thou seen6 ,there1 where the long street roars1 has been ,the stillness of the central sea40 ,we have spoken of sedimentary and organic rocks4 ,there is yet another kind called igneous1 or fiery rocks--those upraised by volcanic action4 ,of the igneous rocks the crystalline have been evidently in a fused condition4 ,granite is an example2 lava or basalt is the usual term for volcanic rock1 and the basaltic caves of ,staffa and the ,giants' ,causeway bear testimony to the igneous or volcanic origin of the surroundings4 ,the pillars and fantastic rocks of ,ireland and ,scotland which are so remarkable1 are simply lava1 which was erupted in a molten state1 now cooled and contracted into blocks of curious regularity of form4 ,illustration3 ,fig4 #fdd4--,trap rock 7,staffa74 ,granite1 already referred to1 is another igneous rock1 and must have been forced upwards2 for as an igneous rock granite has cooled beneath the crust of the earth1 throwing out arms1 while melting1 into other formations1 and frequently being found in mountains4 ,there is another kind of igneous rocks formed by the continuous accumulation of the ashes1 etc41 vomited forth from volcanoes4 ,masses of mountain are thus produced in the course of years1 and the material thus formed is called tufa1 or tuff1 when consolidated2 and this 7now solidified7 is what caused the destruction of ,pompeii and ,herculaneum4 ,illustration3 ,fig4 #fde4--;,eruption of granite4 ,so we have two classes of ,,igneous ,,rocks1 the ,crystalline and ,fragmental 7or the 8,plutonic0 and 8,volcanic071 including basalts1 pitchstones1 pumice1 trachytes1 granite1 syenite1 etc42 and1 on the other hand1 tuff and 8volcanic0 breccia1 with felstones1 porphyries1 etc41 which have been classed as intermediary4 ,of these three classes of rocks1 the sedimentary and the organic compose the greater portion of the earth4 ,we will now glance at the crust of the earth and its various formations4 ,illustration3 ,volcanic eruption4 ,,chapter ,,xliv4 ,,crust ,,of ,,the ,,earth--,,geological ,,systems--,,eozoic1 ,,primary1 ,,secondary1 ,,tertiary1 ,,prehistoric ,,formations4 ,the crust of ,great ,britain has been carefully examined1 and from the results of investigations at various periods1 the earth has been divided into a series of strata which follow the same order of succession4 ,sometimes certain strata may not be present1 and they may be replaced by others1 but the same order of succession will be found4 ,the order is as follows1 commencing at the lowest4 ,the illustration is taken in the opposite direction3-- ,laurentian ,until recently believed to 8,eozoic40 ,cambrian be without traces of living creatures2 hence 8,eozoic40 ,palzoic1 ,silurian or ,old ,red ,sandstone ,shell-fish1 seaweed1 ,primary4 ,carboniferous ferns1 fish1 low reptiles4 ,permian ,mesozoic1 ,triassic 7,upper or ,red ,sandstone7 ,secondary4 ,oolitic ,birds1 marsupials1 reptiles4 ,cretaceous ,kainzoic1 ,eocene ,superior life4 ,mammals1 or ,miocene with great vegetable life1 on ,tertiary4 ,pliocene to plants and animals now ,post-tertiary existing4 ,man4 ,quaternary4 ,recent--,prehistoric ,illustration3 ,,tertiary ,,strata4 ,,upper ,,and ,,middle ,,secondary ,,strata4 ,,lower ,,secondary ,,strata4 ,,primary ,,strata4 ,fig4 #fdf4--,systems4 ,,the ,,pal,,zoic ,,systems4 ,,laurentian ,,system4 ,it will be perceived from the above list that the ,laurentian ,rocks are the oldest4 ,the name is derived from the ,st4 ,lawrence formations1 and was given to the strata by ,sir ,william ,logan4 ,they are metamorphosed rocks older than the ,cambrian4 ,these rocks are sedimentary1 of very old deposition1 and of a crystalline nature1 consisting of quartz1 gneiss1 etc4 ,the granite was probably formed by the fusion of its component constituents1 quartz1 mica1 and felspar1 which become crystallized by the excessive heat4 ,for a long time no traces of organisms could be detected in this or the ,cambrian systems1 but modern research has been rewarded with a little success4 ,the original deposits of micaceous gneiss1 etc41 have been altered1 and many true igneous rocks1 such as syenite and granite1 are found in them4 ,these very old rocks must have been originally deposited in strata converted by heat and pressure into crystalline rocks4 ,these rocks have been divided into two series1 under the names of lower and upper ,laurentian4 ,they are metamorphic1 and consist 8mainly of gneiss interstratified with mica-schist1 with great beds of quartz1 and massive beds of crystalline limestone1 of which one varies from #gjj to #a1ejj feet in thickness4 ,conglomerates also occur1 and there are vast deposits of magnetic and specular iron4 ,graphite1 or blacklead1 is disseminated in strings1 veins1 and beds through hundreds of feet of the lower ,laurentian1 and its amount is calculated by ,dr4 ,dawson to be equal in quantity to the coal seams of an equal area of the carboniferous rocks0 7,nicholson74 ,illustration3 ,fig4 #fdg4--,upward ,granite 7,section74 ,illustration3 ,fig4 #fdh4--;,conformable ,strata4 ,illustration3 ,fig4 #fdi4--,unconformable ,strata4 ,hitherto1 no distinctly recognisable fossil has been discovered1 with the important exception of the ,eozon ,canadense1 which has been pronounced to have been a gigantic foraminifer1 growing layer upon layer1 and thus forming reefs of limestone2 the subject1 however1 is still a matter of dispute4 ,the eozon was discovered by ,mr4 ,j4 ,m',mullen in #aheh in ,canada4 ,granite was at one time considered to be the true primitive rock4 ,gneiss is a word of ,saxon origin1 and consists of the same materials as granite in different proportions4 ,mica-schist is made up of two of the same constituents as the granite and gneiss4 ,they are without fossil traces4 ,illustration3 ,fig4 #fej4--,nereites ,cambrensis4 ,the ,,cambrian system of aqueous origin may be said to contain evidence of the dawn of organic life4 ,it is part of the clay-slate system1 and the term 8,cambrian0 is taken from the ancient name of ,wales1 where slate is plentiful4 ,mica-slate is also very important4 ,these ,cambrian rocks are of the next oldest formation to the ,laurentian1 and all the various deposits may be examined in ,wales1 where also traces of volcanic and ice action may readily be perceived4 ,in the pass of ,llanberis one immense ice-borne block is very prominent2 no agency but ice could have put it there as it rests4 ,it is estimated that the ,cambrian and 8,lower0 ,silurian rocks are from #bj1jjj to #cj1jjj feet in thickness1 and must embrace a very lengthened period4 ,the fossils of these formations show that zoophytes and certain primitive crustacea lived in the remote ages when these rocks were formed by sedimentary deposition4 ,we have scarce a trace of plant-life4 ,the organic remains include annular worms1 the first arrangement of the articulated animals according to ,cuvier4 ,the flora and fauna are1 of course1 very low in the scale of creation1 when land and sea were so differently arranged4 ,illustration3 ,fig4 #fea4--,section across ,snowdon4 ,a1 ,fossiliferous grits 7,bala series72 ,b1 ,greenstone 7intrusive72 ,c1 ,porphyry2 ,d1 ,volcanic ashes1 sometimes calcareous and fossiliferous ,bala limestone4 ,illustration3 ,fig4 #feb4--,silurian fossil4 ,the ,,silurian system was so named by ,sir4 ,r4 ,murchison1 after the territory formerly occupied by the ,silures1 but the system is1 of course1 universal4 ,we have here sandstones1 limestones1 and shales1 deposits lying upon the ,welsh slate4 ,the ,upper and ,lower ,ludlow beds1 and the 8,may ,hill0 sandstone1 then the ,lower ,silurian1 with ,caradoc beds1 and the ,tremadoc slate1 etc4 ,in this system volcanic action is observable1 and all the organic remains are those of marine animals1 such as corals1 shell-fish1 marine worms1 encrinites1 molluscs1 and other zoophytes in great variety4 ,we find also a number of graptolites1 trilobites1 echinus 7sea-urchin71 terebratula1 and many other forms4 ,illustration3 ,fig4 #fec4--,trilobite4 ,illustration3 ,fig4 #fed4--,terebratula4 ,the ,trilobites were amongst the first creatures inhabiting our globe1 and it is a curious fact to contemplate1 that their eyes 7fig4 #fee7 should have been preserved perfect2 they present one of those wonderful objects which carry one's thoughts backwards to the early ages of the world1 probably many millions of years1 and yet it is found by the peculiar structure of the eyes of these ,trilobites that they were placed at the bottom of the sea with perfect power to look upwards at the light of the sun through the transparent waters4 ,the same hand and the same power had then ,divine care and solicitude for the well-being of ,his creatures1 as great as ,he has for those of later ages1 and these animals are mentioned in ,genesis--8,let the waters bring forth abundantly the moving creature that hath life40 ,illustration3 ,fig4 #fee4--;,eye of ,trilobite4 ,thus we see that ages of comparative quiet succeeded the first great contraction of the earth's crust1 probably millions of years1 during which time the tides and currents of the ocean had to wash and wear down all the thousands of projecting rocks or inequalities1 and dissolve 7as before described7 all the lime1 depositing the sand and clay in those immense strata which form the old-named 8transition series02 this appears to have taken place over nearly the whole world at that time1 and ages upon ages must have elapsed to form such deposits as the sandstone1 claystone1 and limestone1 in alternation1 forming the 8,llandilo10 8,caradoc10 and 8,wenlock0 strata1 more than a mile in thickness2 these are by some geologists reckoned among the primary series 7by some called the 8transition rocks071 and in ,england form the 8,cambrian0 and 8,silurian0 systems which are so rich in minerals and metallic veins4 ,illustration3 ,fig4 #fef4--,limestone made up of encrinite4 ,the ,,old ,,red ,,sandstone1 or ,,devonian ,system1 is the next of the series of layers which built up our earth1 but a great gap of years separates it from the ,silurian4 ,we find the 8,old ,red0 in the ,mendips and in ,scotland4 ,the rocks in the ,west of ,england are apparently of later deposition and of marine origin1 while the 8,old ,red0 is apparently a fresh-water deposit4 ,it is very 8arenaceous10 and owes its tint chiefly to iron1 although there are circumstances in which it appears neither as a sandstone nor with a red colour2 but red sandstone describes the true formation very accurately4 ,illustration3 ,fig #feg4--;,graptolites4 ,in this water-deposited system1 whether in lakes or by the sea1 we find a considerable advance upon the ,silurian4 ,we have flora in more variety--seaweeds and ferns4 ,the remains are all aquatic4 ,we have nothing higher in the scale of creation than the fish1 the first vertebrates2 and judging by varieties a very considerable time must have elapsed during which the ,old ,red ,sandstone was deposited4 ,the dipterus--or double-winged--is herewith shown as an example of the fossil fish of the ,old ,red ,sandstone period4 ,illustration3 ,fig4 #feh4--8;,double-winged0 ,fish4 ,it is curious that no remains of any land-inhabiting animals have been discovered in this system--whether in the ,old ,red or the ,devonian formations 7the ,lower and ,upper ,red ,sandstones74 ,we can only distinguish the remains of aquatic animals or plants4 ,we may picture the great cuttle-fish1 the nautilus1 and the dipterus1 with various orders of mollusca1 and the gradual approach to the crustacea1 but no terrestrial animals have been discovered4 ,we may take it for granted then that the ,old ,red ,sandstone and ,devonian systems are different--the former being found in ,scotland and parts of ,england1 and formed of deposits in fresh or brackish water1 while in the ,devonian system the marine deposits are corals1 and all the indications of ocean life1 separated from the great inland lakes by a range of hills4 ,neither of the terms 7,old ,red ,sandstone or ,devonian7 limit geographically or descriptively the formations of this system4 ,all the rocks are clearly distributed between the ,silurian and the ,carboniferous4 ,the invertebrates in this last system have not developed very much1 but corals are very abundant1 and fish of some armoured species are plentiful and curious1 while the crustacea were enormous4 ,illustration3 ,fig4 #fei4--,palozoic ,fish4 ,trilobites1 ,brachiopods1 ,coral and ,graptolite4 ,we now arrive at the most important of all the rock formations1 the one to which we owe our national prosperity--we mean the ,,coal ,system4 ,,the ,,carboniferous ,,formation4 ,while the foregoing depositions were being made the earth was still undergoing changes4 ,the sandstones were deposited1 and the corals making use of the lime carried into the waters began to build and form masses of limestone under the sea1 pushing back the water and changing the forms and positions of land and water4 ,all this went on apparently very quietly--volcanic action was not very frequent--the water was warm4 ,but sometimes earthquakes would heave up the submarine formations into mountains1 and therefore we find the fossils of the tiny sea-animals on the hills4 ,extensive swamps were formed by partially retreating sea-water1 and their vegetation became luxuriant4 ,tree ferns and all the floral appearance of the tropics grew up and formed dense forests1 far thicker than any we know of at the present time4 ,it will readily be understood that the condition of the atmosphere must have been particularly favourable to the growth of plants1 and therefore not suitable for air-breathing animals4 ,heat and carbonic acid must have been greatly developed4 ,illustration3 ,fig4 #ffj4--,tree ,ferns4 ,we can now perceive how the gradual filling up of the earth for man's reception was taking place4 ,the rain was taking carbonic acid from the air1 for the dead plants gave it out in enormous volumes4 ,the carbonate of lime dissolved in the water-springs1 etc41 was carried to the sea for polypi to build shells from4 ,the trees were absorbing carbonic acid1 too1 and while purifying the air1 were retaining the carbon in their stems and leaves and branches1 which 7when they decayed7 remained untouched1 and accumulated in thick layers to sink down1 and by pressure be turned into coal4 ,this great effect was carried out several times2 and it is a remarkable fact that we find coal1 limestone1 and ironstone so near together1 all useful to us and to each other in the course of the working of the minerals--so we come to the ,carboniferous system4 ,illustration3 ,fig4 #ffa4--,limestone made up of corals 7,favosites polymorpha74 ,coal we have already treated of in ,mineralogy1 and coal looks at times very different from our preconceived ideas of a sedimentary rock1 which we know is regularly deposited in layers4 ,but when we split or break the coal we find its cleavage in a certain direction4 ,coal is wood squeezed and petrified by ages between enormous layers of sedimentary rocks1 and the coal-seam rests upon the soil in which the plants once grew--perhaps more than six hundred thousand years ago6 ,of course coal1 as we burn it1 was not all made at once4 ,we can trace it from the swamp as ,peat1 on to 8,lignite10 or woody coal1 through the ,tertiary and ,new ,red ,sandstone to the coal measures themselves4 ,even lower down we find the remains in more or less pure carbon forms--the anthracite and the graphite of the primary formations4 ,coal appears not to have been formed equally in all places during the period in which it originated4 ,the remains of plants found in these strata lead us to infer1 that1 during that period there existed an exceedingly vigorous and crowded vegetation1 consisting principally of tree ferns and equisetace1 of which the ,sphenopteris ,hninghausii 7fig4 #ffb71 ,pecopteris aquilina 7fig4 #ffc71 and ,neuropteris ,loshii 7fig4 #ffd71 are amongst the most beautiful that have been found1 and the flora and fauna of this period were of a more or less primitive kind or low order1 but very luxurious4 ,the former display a decided advance1 and reptiles of aquatic forms appear with large and predaceous fishes4 ,mountain limestone1 which is usually found in the coal formations1 includes metallic deposits1 and organic remains are very abundant in it4 ,the following are specimens of the fossils-- ,illustration3 ,fig4 #ffb4 ,illustration3 ,fig4 #ffc4 ,illustration3 ,fig4 #ffd4 ,illustration3 ,fig4 #ffe4-- #a4 ,bellerophon costatus4 #b4 ,spirifer glaber4 #c4 ,productus ,martini4 #d4 ,orthoceras lateralis4 ,the ,carboniferous system is a very important one1 as may be seen4 ,in these beds we have coal1 limestone1 sandstone1 and shale4 ,the ,coal ,measures consist of grit and sandstone and shale1 with coal seams4 ,the ,carboniferous ,limestone1 or 8,mountain0 ,limestone1 has no coal in it4 ,the sandstone has been termed 8,millstone ,grit10 because millstones are made from it4 ,we then have limestone shales1 and the sandstone beds4 ,each coal seam indicates a subsidence of the land and a regular series of underclay or soil in which the plants grew1--the plants themselves1--iron1 coal1 and then the shale1 and so on again1 indicating frequent changes and a long lapse of ages4 ,illustration3 ,fig4 #fff4--;,fern 7,pecopteris ligata7 from upper shale1 ,scarborough4 ,these 8,coal ,measures0 occupy an area of five hundred square miles in ,great ,britain alone2 and as we have already said1 the period which elapsed while these deposits were being laid down represents hundreds of thousands of years4 ,the deposit would increase at the rate of about three feet in a thousand years4 ,and this is only one period of the many changes to which our world has been subjected since it first began its revolution in space around the sun4 ,illustration3 ,fig4 #ffg4--,section across the carboniferous rocks of ,derbyshire and ,lancashire 7,after ,ramsay74 #a4 ,carboniferous ,limestone4 #b4 ,yoredale ,shales4 #c4 ,millstone ,grit4 #d4 ,coral ,measures4 #e4 ,permian ,limestone4 #f4 ,new ,red ,sandstone4 ,coal is usually found in 8basins0 or depressions--a sort of trough owing to the upheaval of surrounding strata which became in time denuded 7or washed away7 with any coal that was there4 ,so it is in places where it is concealed by overlying beds that protect it1 that we now find the coal saved from disturbance4 ,when we search and come upon red sandstone and grey-wacke1 we may be almost certain that we are near coal1 particularly if the surrounding rocks form a 8basin40 ,illustration3 ,fig4 #ffh4--,labyrinthodon4 ,we have now briefly sketched the ,carboniferous system1 for in our recreations we can do little more4 ,we shall find in many places in ,england tree trunks in the sandy shore1 and ample evidence that a forest has been at one time submerged in that spot4 ,so inland the land sank down again and again in successive periods--water1 mud1 soil1 vegetable growth succeeded1 to be again submerged and form a new coal seam for the use of man1 who was destined to appear after the lapse of ages4 ,,the ,,permian ,,period4 ,illustration3 ,fig4 #ffi4--;,impressions of feet of ,cheirotherium4 ,at length the land remained undisturbed4 ,it sank no more1 and the trees waved luxuriously over the buried forests of past ages1 and another cycle set in called the ,,permian1 from the ancient kingdom of ,permia1 where all the features of that period are exhibited on a very grand scale1 and which extended for several hundred miles between the ,ural mountains and the ,volga4 ,in the ,permian period we have the progression of animal life more distinctly developed than in the ,carboniferous system1 which immediately preceded it4 ,it is true there are indications in the latter that curious animals1 called the ,cheirotherium and the ,labyrinthodon1 were alive then1 and the remains of numerous insects1 such as beetles and crickets1 have been found2 but the ,permian developed them1 and reptiles1 saurians1 and lizards have been traced2 but as ,sir ,r4 ,murchison states1 throughout the whole extent the animals are of a single type4 ,we have the hand-like impressions of the feet of the ,cheirotherium1 so called from the ,greek 8cheir10 a hand4 ,the soil appears to have been very soft1 and peculiarly adapted to receive impressions1 and which having been in many places covered over with a stratum of fine sand1 and then abandoned by the sea1 the whole has hardened into stone1 and being now separated1 the one contains their footprints1 and the other perfect casts of them6 ,nor are these footmarks all that these sandstones have to tell us of their day2 for the ripples of the waves1 and even the little pits made by drops of rain as they fell1 are in this most marvellous manner preserved1 forming objects of wonder and admiration4 ,the organic remains during this period are not very abundant1 and many of the fauna of the previous systems appear to have died out1 while others appeared to meet with fuller development in succeeding ages4 ,the ,permian is also known as the ,new ,red ,sandstone1 or ,magnesian ,limestone group4 8,dias0 has also been suggested with reference to the 8,trias0 group1 8the ,upper ,new ,red ,sandstone10 which comes next4 ,the ,permian rocks are very varied1 and contain minerals1 such as copper and sulphur4 ,as the strata below the new sandstone formation was called the 8,carboniferous0 system1 from its containing much carbon in the form both of coal and carbonic acid1 so this has been called the 8,saliferous0 system1 from the occurrence in many places of strata of 8rock-salt10 or crystallised chloride of sodium1 and 7where the rain finds its way down and dissolves it7 of brine springs2 these 7in ,england7 exist chiefly in ,cheshire and ,warwickshire1 but in ,poland and ,hungary they exist on a much larger scale1 the rock-salt being nearly a thousand feet thick4 ,it has been said that these strata of salt were formed by the evaporation of salt lakes1 but it is much more probable that salt is one of the natural materials of the earth1 and that both salt lakes and oceans have become salt from dissolving out these strata wherever they have come into contact4 ,it is supposed that during the ,permian period the greater portion of the continent of ,europe was raised above the ocean1 and the deposits were formed in salt lakes1 for the appearance of the organic remains tends to establish the fact that the creatures of that period were not far from dry land even in their watery existence1 and the reptiles found confirm this view4 ,we have now to examine the ,mesozoic1 or ,secondary ,system4 ,illustration3 ,dinotherium giganteum4 ,,chapter ,,xlv4 ,,the ,,mesozoic ,,system--,,the ,,triassic1 ,,oolitic1 ,,and ,,cretaceous ,,formations--,,the ,,eocene1 ,,miocene1 ,,and ,,pliocene--,,the ,,glacial ,,period--,,pre-,,historic ,,man4 ,we trust that the general reader has gleaned from the foregoing chapter some few ideas concerning the growth of plant and animal life in the early periods of the world's existence4 ,from the ,laurentian ,system we have briefly traced the conformation of the globe at the dawn of organic life through the ,silurian ,old ,red ,sandstone and ,carboniferous formations1 indicating as we proceeded the chief points in the world's history1 and the gradual development of life through many ages4 ,there is no real or bold line of demarcation drawn between these systems4 ,as seam unites to seam1 and layer to layer1 stratum upon stratum1 so the systems almost insensibly unite1 and forms of life appear1 mature1 and die away as the babe grows into the man1 and dies away again to old age and final extinction4 ,so one system merges into another1 each and all a factor in the great work which was intended to prepare the earth for the greatest and latest development of ,nature--,,man6 ,illustration3 ,fig4 #fgj4--;,fossils of the ,trias ,group4 #a4 ,ammonites nodosus4 #b4 ,avicula socialis4 #c4 ,possidonia minuta4 #d4 ,encrinites moniliformis4 ,but all this while the earth had been1 as it still is1 undergoing continual change4 ,sometimes gradually1 in the wearing away1 or elevation of beach or headland2 sometimes suddenly1 as when mighty hills were upheaved and the deeply-laid granite or limestone was lifted to the summits of the mountains from the depths of the sea4 ,land and water came and went1 and the ever-changing earth still brought forth abundantly 8the herb yielding seed after its kind10 and the 8moving things upon the ground after their kind10 ever improving and developing till they culminated in the splendid vegetation and immense animals of the ,tertiary period1 and lay silent afterwards in the cold grasp of the great ice age for the thousands of years of the glacial epoch4 ,illustration3 ,fig4 #fga4--,plesiosaurus4 ,we now enter upon the ,,trias1 or ,new 7,upper7 ,red ,sandstone1 which is divided into ,upper and ,lower ,trias1 8,keuper0 and 8,bunter40 ,we have three principal headings in the ,secondary ,system--the ,,triassic 7the oldest71 the ,,oolitic1 and the ,,cretaceous4 ,in the first we find red sandstones and shelly limestone2 in the second1 clays and shale2 in the last1 chalk1 or white limestone4 ,in some districts there are traces of volcanic action4 ,on the top of the 8,upper ,trias10 or 8,keuper0 formation1 we have the ,lias1 which succeeds the ,rhtic beds1 and in this we find many rich traces of reptiles and birds which come now before us in the rising scale of creation4 ,in the seas of this period we have numerous crustacea1 the nautilus and the cuttle-fish4 ,the ,saurians now come before our retrospective vision4 ,it is the 8,reptile ,age0 in all its development1 and the huge labyrinthodon1 the iguanodon1 pterodactyle1 and ichthyosaurus testify to the magnitude of the fauna of the period4 ,the first mammal specimen1 a marsupial1 has been traced back to this time2 and the tropical temperature was favourable for luxuriant vegetation1 pines1 and palms4 ,illustration3 ,fig4 #fgb4--,restorations of ,saurians1 etc4 ,in the swamps or shallow waters the great reptiles disported themselves1 and seized their prey1 the water-fowl1 which now appeared in numbers1 and of enormous size4 ,nor were insects absent4 ,numbers of remains have been discovered2 beetles1 dragon-flies1 grasshoppers1 etc41 in multitudes yield us information1 while the marine fossils1 star-fish1 mollusca1 and various fishes1 are of frequent occurrence4 ,animal and vegetable life during this period must have been very rich and varied--literally leaving 8footprints in the sands of time40 ,illustration3 ,fig4 #fgc4--,pterodactylus longirostris4 ,the 8,blue ,lias0 is a term familiar to every reader4 ,it is a kind of limestone mixed with clay1 of a blue colour1 and upon this we find the ,oolitic1 or ,oolite ,system--so called because it somewhat resembles the roe of a fish4 ,the ,lias clays are used for bricks1 and ,whitby 8jet0 is also obtained from the ,upper ,lias4 ,jet is really a lignite1 or wood in the process of transmutation4 ,in this ,lias formation1 besides the numerous fossil remains already mentioned1 we find the 8snakestones0 7ammonites71 the stone-lily1 and belemnites1 with many nautili and shells4 ,illustration3 ,fig4 #fgd4--;,ichthyosaurus4 ,the ,,oolite1 or ,,jurassic1 underlies the chalk1 and overlies the ,trias formation4 ,the term 8,jurassic0 originates from the ,jura range1 which is almost entirely composed of ,oolitic strata4 ,these strata are greatly distorted by pressure1 and when we reach ,switzerland and the familiar ,alps1 we find gneiss1 crystalline1 limestones1 and schists1 into which the ,oolite has been metamorphosed4 ,the ,oolite is divided into ,upper1 ,middle1 and ,lower1 consisting of the following3-- ,pembroke ,beds4 ,upper ,oolite ,portland 8 ,kimmeridge ,clay4 ,calcareous ,grit4 ,middle ,oolite ,coral ,rag4 ,oxford ,clay4 8,cornbrash0--,forest ,marble4 ,stansfield ,slate4 ,lower ,oolite ,bath ,oolite4 ,fuller's ,earth4 ,inferior ,oolite4 ,illustration3 ,fig4 #fge4--,sketch-map of various geological formations4 ,the ,oolite formation 7see ,map7 occupies a stretch of country in ,england extending from ,yorkshire into ,dorset4 ,the ,great ,oolite holds the ,fuller's earth1 and the ,bath stone is also well known4 ,the ,stonesfield slate holds many remains of reptiles4 ,it is a kind of shelly limestone1 and is used for roofing purposes4 ,the ,forest ,marble 7so called from ,wychwood ,forest7 is a sandy limestone holding marine fossils4 ,it is used for ornaments4 ,the ,coral ,rag and ,oxford clay are rich in fossils1 and the former1 as its name implies1 is composed of ancient coral reef4 ,the ,portland beds produce the well-known building stone4 ,the ,purbecks1 of which there are three divisions1 appear to have been deposited in fresh water1 and occur in ,dorsetshire4 ,all the ,oolite strata supply organic remains4 ,we have plants and ferns1 reptiles1 and a number of new genera of conchifera and cephalopods1 star-fish1 urchins1 and the enormous bats1 and the terrible megalosaurus1 and the cetiosaurus1 steneosaurus1 and pliosaurus1 of enormous size4 ,one very remarkable bird has been found in the ,bavarian limestone of this period2 it is called the ,archopteryx1 which is described as having a leg-bone and foot like the familiar birds1 but the tail is lizard-like1 with feathers springing from each joint4 ,sponges1 corals1 and fish1 and many other forms of animal life are found in the ,oolites4 ,the reptiles must have had it all their own way in this period1 for there were both carnivorous and vegetable feeders1 and teeth of the pliosaurus have been found which measure fifteen inches1 the jaws being six feet long4 ,we have seen that corals must have built up their reefs in the waters1 which then overlaid the land we call the ,united ,kingdom4 ,there must have been great changes during this period1 and the strata are chiefly marine4 ,the ,wealden formations are the exceptions1 and in the fresh-water deposits insect forms abound4 ,the appearance and variety of animal and vegetable life must have been curious and interesting4 ,the ,weald or 8,wold0 of ,kent is often spoken of1 and it extends with the ,surrey and ,sussex ,wealden formations for some distance4 ,the strata are of fresh-water deposition1 differing in this from the chalk1 although the ,wealden beds are included in the ,cretaceous ,group1 which is composed as follows3-- ,wealden4 ,lower ,greensand4 8,gault40 ,upper ,greensand4 ,chalk ,marl4 ,upper ,chalk 7without ,flint74 ,chalk 7with ,flint74 ,maestricht4 ,the 8,wealden0 formation is divided into ,hastings sand and ,weald clay4 ,the former consists of clay and sandy beds1 and is observable at ,hastings1 and in the neighbourhood of ,tunbridge4 ,the ,weald clay consists of blue and brown clays1 with sandstone1 and the limestone known as 8,sussex ,marble10 which is formed by the paludina of the rivers4 ,there is another division often seen in ,dorsetshire1 and called the ,punfield beds1 which partake both of marine and fresh-water remains1 which are distinct in the true ,wealden and cretaceous formations1 the former being of fresh1 and the latter of salt-water origin4 ,the remains of enormous reptiles are numerous in the ,wealden formations2 crocodiles1 lizards1 turtles of gigantic size have been discovered1 and most curious fossils have been disinterred in the ,hastings district4 ,the 8,greensands0 are separated by what is termed gault1 a stiff blue clay found in ,norfolk1 ,essex1 and ,kent4 ,the ,lower ,greensand includes the well-known ,kentish rag1 or limestone1 of which so many churches are built4 ,the ,upper ,greensand is supposed to be a seashore deposit on the sides of an extensive ocean or sea1 at the bottom of which the chalk was formed4 ,after the ,wealden beds were formed1 they were covered by these greensand estuary-beds1 or littoral strata4 ,in these series new forms of life appeared1 and the waters became the receptacle of myriads of mollusca1 etc41 which in time formed the great chalk cliffs and downs so often referred to4 ,the chalk is interstratified with sand1 which as 8gault0 and 8greensand0 was probably the sand of the ocean bed before the chalk was formed upon it1 and the seas must have supported many marine reptiles1 for stony 8nodules10 or coprolites1 which are the fossil excreta of the animals1 are found1 and now used for manure1 after being buried for thousands of years4 ,examination of these remains has resulted in the discovery of the teeth and bones of fish which had been devoured by the gigantic reptiles4 ,an illustration of a shell thus discovered is annexed4 ,illustration3 ,fig4 #fgf4--;,echinus 7,hemicidarus intermedia1 ,chalk74 ,illustration3 ,fig4 #fgg4--,nautilus ,inequalis4 ,illustration3 ,fig4 #fgh4--;,ammonite from the chalk4 ,we have in a former chapter spoken of the chalk and its formation4 ,we know that it is composed of the minute foraminifera4 ,the fossil remains are very numerous in chalk and all of a marine kind1 such as the ammonites1 belemnites1 and such cephalopods1 and the echinus1 bivalve mollusca1 crustacea1 etc4 ,we have occasionally flints appearing in the chalk1 and this circumstance has given rise to some speculation as to how the flints got there1 for they consist of nearly pure silica2 and the theory of the petrifaction of sponges1 madrepores1 etc41 has been started to account for their presence4 ,dr4 ,carpenter says3 8,it may be stated1 as a fact beyond all question1 that nodular flint and other analogous concretions 7such as agates7 may generally be considered as fossilised sponges or alcyonian zoophytes1 since not only are their external forms and their superficial markings often highly characteristic of those organisms1 but when sections of them are made sufficiently thin to be transparent1 a spongy texture may be most distinctly recognised in their interior40 ,it is now generally admitted that the decaying animal matter acts upon the silicious spicul of sponges1 etc41 and the silica is thus deposited4 ,we may then surmise that at some very distant period the whole extent of the ,british ,isles was submerged1 as well as portions of the continent1 and after the strata had been deposited the sea and land were disturbed by volcanic action4 ,while the secondary strata were being deposited1 very little relative alteration took place1 as the deposits are seen to lie 8conformably40 ,but when the great convulsion which upheaved the ,apennines occurred1 the chalk was raised as we find it in the cliffs and downs1 which were the beds of seas4 ,this is the last of the great convulsions which the earth has undergone1 for the tertiary strata1 which afterwards began to be deposited1 rest in the hollows or basins 7chiefly in the chalk7 then left2 the alterations in and since these deposits appear to consist chiefly of the upheaval of certain localities1 the depression of others1 the evaporation of inland lakes1 and the wear and tear of the land from these causes1 which are still in continuous action 7as from the washing down of cliffs by the sea1 and the formation of mud deposits at the mouths of rivers71 or the volcanic agencies which in some places 7as in ,ireland7 have cast up basalt over the chalk4 ,illustration3 ,fig4 #fgi4--,mosasaurus 7,maestricht74 ,there is a sort of transition formation which is classed with the ,cretaceous ,system1 and termed 8,maestricht10 after the town in ,belgium4 ,it appears that this is an upper chalk layer1 an intermediary between the ,secondary and ,tertiary1 and here on the banks of the ,meuse we find the ,mosasaurus1 the 8lizard of the ,meuse10 of whose remains we give specimens in the illustration4 ,this transition chalk--as we may call it to distinguish it--must have been laid down at a later period than the flinty chalk1 and we find it in many places4 ,it serves therefore as a fitting introduction to the ,tertiary ,period of ,geological time4 ,,the ,,tertiary ,,period4 ,we now enter upon a period when the animal creation attained its greatest development1 the 8,age of ,mammals02 for they were then the kings of creation4 ,the ,tertiary ,period is divided into three stages1 viz4-- ,the ,,eocene1 or the ,dawning of the now existing creation4 ,the ,,miocene1 or the ,middle1 or 8minority0 of existing creation4 ,the ,,pliocene1 or the ,recent1 or still more developed period4 ,we will glance at them in that order1 which ,sir ,c4 ,lyell introduced4 ,illustration3 ,fig4 #fhj4--,skull of the ,dinotherium4 ,the ,eocene formation is shown in what is termed the 8,london ,basin10 here illustrated by a section in which we find soft sands without fossils 7,thanet ,beds71 and a kindred kind in ,surrey1 in which fossils 7marine7 are found4 ,after these we get the 8,reading and ,woolwich0 beds as we ascend4 ,these are of clay and pebbles1 etc41 with river fossils4 ,the ,oldhaven beds are included on the map2 they occur towards ,blackheath and ,herne ,bay4 ,the ,london clay is very stiff1 and in some places blue4 ,it is full of fossils of birds1 beasts1 fruits1 and vegetables1 trees1 reptiles1 and fish1 and the variety of the organic remains appears to indicate the fact that at one time the ,thames flowed through swampy ground to the sea1 in which dwelt1 in a warm climate1 immense mammalia1 such as the megatherium1 glyptodon1 tapir1 etc41 and some turtles of enormous size4 ,it is also on record from late observations that these immense animals were even mixed up1 and almost fabulous creatures inhabited the land where ,england now is4 ,we read of antelope-horses1 lion-like bears1 and camel-stags4 ,the vegetation was then of a tropical kind1 and in the deep forests and jungles these enormous animals--the mammoth dinotherium1 and such species--roamed and plunged in the swamps at the mouth of the ,thames4 ,at length these types died away1 and gave place to the elephant and the hippopotamus1 and the climate by degrees became less warm1 and still slowly decreased in temperature4 ,a glance at ,sir ,c4 ,lyell's 8,principles of ,geology0 will show us how1 as we examine the more modern strata1 we find a great increase in the ,european lands1 which may have been compensated by the submersion of the ,pacific islands4 ,during the period of the vegetation of the ,secondary epochs1 our climate 7between the lias and the chalk7 was favourable to a tropical growth4 ,enormous rivers flowed through our islands1 and gigantic crocodiles1 etc41 with flying reptiles1 were masters of the land4 ,there were numerous fishes1 but the reptiles did not appear in such very great numbers4 ,illustration3 ,fig4 #fha4--,section across the ,london ,basin 7,w4 ,whitaker74 a ,lower ,bagshot sand 7of ,hampstead74 b ,london ,clay4 c ,reading and ,woolwich beds 7including the ,oldhaven beds1 which occur in the south only74 d ,thanet sand 7crops out on the south only74 e ,chalk with flints4 f ,chalk without flints4 g ,upper ,greensand 7crops out on the south only74 h ,gault4 i ,lower ,greensand4 k ,wealden beds 7on the south only74 l ,oolitic clays 7shown only on the north1 but proved to occur on the south beyond the range of the section1 by the sub-,wealden boring1 near ,battle1 in ,sussex74 x ,old rocks1 shown by borings at ,kentish ,town and at ,meux's ,brewery1 to pass under the ,london basin4 ,these large and elephantine animals must have existed while the climate of ,northern ,europe underwent some very considerable changes4 ,we read of the woolly rhinoceros1 and the hairy elephant1 or mastodon1 which has been found in ,siberia4 ,reindeer appeared in ,england1 and we know now that these animals inhabit cold countries4 ,the mountains were considerably elevated during the latter ,tertiary period2 snow fell and ice formed upon the summits of the mountains1 while glaciers crept down the sides4 ,the warm1 almost tropical climate of the prior ages was gradually but surely giving way to the ,ice ,age2 the earth was slowly dipping1 and the sun's rays had less power4 ,professor ,ramsay says the 8assemblage of fossils found in the ,london clay point to the fact that the whole of these strata were deposited in the estuary of a great continental river comparable to the ,amazon and the ,ganges4 ,the palm-nuts and the host of other plants help to prove it1 and the remains of river tortoises1 crocodiles1 snakes1 marsupials1 and several tapir-like mammals1 all point in the same direction4 ,the estuarine conditions begun during the deposit of the ,woolwich and ,reading beds were still going on when the ,london clay was thrown down2 with this difference1 that by sinking of the area the estuary had become longer1 wider1 and deeper1 but still remained connected with a vast continent1 through which the ,eocene river flowed40 ,illustration3 ,fig4 #fhb4--;,anoplotherium commune3 palotherium magnum and minus2 and crocodile4 ,the ,miocene deposits are not so generally important in the ,united ,kingdom1 but in ,america very valuable fossils have been discovered in these strata4 ,the ,pliocene strata extend along the east of ,great ,britain1 where they are denominated 8,crag10 as ,norfolk ,crag1 ,red ,crag1 ,coralline ,crag4 ,underneath these mammalian remains have been discovered4 ,after the ,pliocene we come to the ,post-,pliocene1 which really closes the long ,tertiary period4 ,during these ages the gradual development of created beings apparently reached its height4 ,it was towards the end of the ,middle ,eocene that the great mountain chain of ,europe came into existence1 which is connected1 as any casual observer may see1 with the ,himalaya4 ,in fact1 the whole chain1 from the ,thibetian range through ,india1 the ,caucasus1 ,alps1 and ,pyrenees1 is continuous1 and formed of the same material 78nummulitic limestone074 ,there is no doubt that the whole northern hemisphere enjoyed at the commencement of the ,tertiary period a warm1 not to say tropical1 climate1 which got colder and colder4 ,we find the increase of animals and plants more fitted to the requirements of man and our present climate4 ,there are many signs of the successive increase of land in ,europe generally1 while the contrast the ,tertiary period bears to the ,secondary is very marked4 ,in the former we have extensive deposits in the waters of wide1 open seas2 in the latter the depositions were evidently made where dry land1 with its accompanying bays and lakes1 were extensive and numerous4 ,the former is marine1 the latter lacustrine and marine4 ,the seas of the ,tertiary period have lately been defined4 ,illustration3 ,fig4 #fhc4--,megatherium cuvieri 7post-,pliocene71 ,s4 ,america4 ,sir ,charles ,lyell1 in his 8,principles of ,geology10 shows us this1 and defines the ,european features at the commencement of the ,tertiary epoch4 ,at that time1 the ,british islands1 with the exception of the basins of ,london1 the ,isle of ,wight1 and ,norfolk1 had wholly emerged from the deep4 ,but a third part of ,france was still under water4 ,italy consisted only of a long and narrow ridgy peninsula1 branching off from the ,alps near ,savona4 ,turkey and ,greece1 south of the ,danube1 were laid dry2 and a tract of land extended from the ,vosges1 through central ,germany1 ,bohemia1 and the north of ,hungary1 perhaps to the ,balkan4 ,but the whole of the north of ,europe and ,asia1 from ,holland eastward to central ,tartary1 and from ,saxony and the ,carpathians northward to ,sweden1 ,lapland1 and the ,ural chain1 lay beneath the ocean4 ,the same subterranean movements1 which have subsequently raised the wide plains of our northern continents above the sea-level1 have given great additional elevation to the then existing land4 ,thus the ,alps have certainly acquired an increased height of from two thousand to four thousand feet since the commencement of the ,tertiary period4 ,the ,pyrenees1 whose highest ridge consists of marine calcareous beds1 of the age of our chalk and greensand series1 while the ,tertiary strata at their foot are horizontal1 and reach only the height of a few hundred feet above the sea1 seem to have been entirely upheaved in the comparatively brief interval between the deposition of the chalk and these ,tertiary strata4 ,the ,jura1 also1 owe a great part of their present elevation to convulsions which happened after the deposition of the ,tertiary groups4 ,on the other hand1 it is possible that some mountain-chains may have been lowered by subsidence1 as well as by meteoric degradation1 during the same series of ages in this quarter of the globe2 and on some points shallows may have been depressed into deep abysses4 ,but1 on the whole1 everything tends to show that the great predominance of land which now distinguishes the northern hemisphere has been brought about only at a recent period1 and ,sir ,charles holds that the shifting of the continents is sufficient to account for the variations of climate4 ,we have every reason to believe that before the ,glacial epoch ,england and the ,continent were united1 and during the ,glacial period ,england and ,north ,america were joined1 vi ,greenland and ,ireland4 ,mr4 ,dawkins says that ,england at that time was six hundred feet above its present level4 ,if so--and we cannot question his conclusions--the ,channel was then dry4 ,illustration3 ,fig4 #fhd4--;,cervus ,megaceros 7,megaceros ,hibernicus73 ,irish ,elk4--,post-,pliocene4 ,the 8,great ,ice ,age0 then came upon the world4 ,for the information of readers who wish to peruse the whole history of this epoch and its causes1 we may add that in ,professor ,geikie's most interesting work1 they will find full details4 ,we can only refer to it4 ,the gradual decrease of temperature upon the earth1 which was the cause of the ,glacial period extending over the north of ,europe1 has been attributed to the eccentricity of the earth's orbit2 and here astronomy steps in to our assistance4 ,we have read in the chapters on ,astronomy1 how the movement of the earth1 like a top near the end of its 8spin10 causes the 8precession of the equinoxes10 and in connection with this phenomenon the earth's orbit becomes more and more circular at certain periods of thousands of years1 and goes away from the sun4 ,we therefore receive the light and heat at a greater angle4 ,consequently1 less heat is received1 and ice is formed1 as at the ,north and ,south ,poles at present4 ,illustration3 ,fig4 #fhe4--;,drift ,ice4 ,doctor ,croll has pointed out that the great eccentricity of the earth's orbit existed about #baj1jjj years ago1 when there was a difference between the nearest and farthest position of the earth and the sun of #ab1jjj1jjj of miles at least4#bh ,this is a very considerable distance even in the enormous spaces which intervene between us and the other planets of the solar system1 and about that time the ,glacial period arrived4 ,perhaps we may make this clearer by going back to the precession of the equinoxes4 ,the earth moves in an orbit called an ellipse1 and the sun is not in the centre of this nearly circular path4 ,we can now understand that the earth comes nearer to the sun sometimes and recedes at others4 ,these points of nearest approach and greatest distance are termed perihelion and aphelion4 ,in the latter case we are about #i1jjj1jjj of miles farther from the sun than when in perihelion--that is1 when the greatest 8eccentricity0 is reached4 ,in addition to this the axis of the earth is continually changing in direction by reason of solar attraction at the equator4 ,this shifting1 as explained in the astronomical section1 is very slight every year1 and in the course of #bd1jjj years the conditions of the seasons will have completely changed round and back again1--for the northern and southern conditions will be reversed in our hemisphere4 ,day and night come twenty minutes earlier every year4 ,we are now nearer the sun in winter as shown in diagram 7page #dig72 when we change we shall be nearest the sun in summer and farthest in winter4 ,illustration3 ,fig4 #fhf4--,the ,mer de ,glace4 ,doctor ,croll1 who has done much in his most interesting paper on changes of climate#bi1 tells us how this eccentricity of the earth's orbit produced indirectly the ,glacial epoch4 ,he shows how1 if in a period of the greatest 8eccentricity0 our winter came in aphelion1 we should receive one-fifth less heat than now1 but a correspondingly greater heat in summer4 ,but if our winter under such circumstances fall 7as now7 in perihelion1 the difference between winter and summer would be practically nil1 because the sun during a period of the earth's great eccentricity 8could not warm the hemisphere whose summer happened to arrive in perihelion40 ,no doubt the sun's rays would be very powerful1 but the earth being covered with ice and snow could not be warmed2 fogs would accrue and hide the sun1 as at present in ,antarctic summers1 when the cold is very great4 ,the warm ocean currents would be stopped1 and the northern portion of our hemisphere would be1 as it undoubtedly was1 frozen over and covered with snow4 ,illustration3 ,fig4 #fhg4--,mammoth and ,irish ,elk4 ,when we consider the millions of years since the earth is supposed to have been launched into space1 we can imagine that the ,glacial periods would occur frequently1 and considering the very slow 8precession0 movement there1 and the alternating tropical climate with graduations of temperature for thousands of years they would last long4 ,the great ,glacial period is computed to have begun #bdj1jjj years ago and lasted #afj1jjj years with alternations of comparative summer2 and so the years went on1 season succeeding season1 altering the appearance of the earth1 and causing successive changes in the distribution of animal and vegetable life4 ,then the great mammalia1 the mammoth and hippopotamus1 with the hyna1 lion1 and other felid came1 and went when ,arctic animals usurped their places4 ,at the later ,glacial epoch man must have arrived in ,britain1 and 8this being so10 says ,professor ,geikie1 8it is startling to recall in imagination those grand geological revolutions of which he must have been a witness4444 ,he entered ,britain at a time when our country was joined to ,europe across the bed of the ,german ,ocean2 at a time when the winters were still severe enough to freeze over the rivers in the south of ,england2 at a time when glaciers nestled in our upland and mountain valleys1 and the ,arctic mammalia occupied the land4 ,he lived here long enough to witness a complete change of climate1 to see the ,arctic mammalia vanish from ,england1 and the hippopotamus and its congeners take their places4 ,at a later date1 and while a mild and genial climate still continued1 he beheld the sea slowly gain upon the land1 until1 little by little1 step by step1 a large portion of our country was submerged--a submergence which1 as we know1 reached in ,wales to the extent of #a1cjj feet or thereabouts40 ,we find that the land underwent many subsequent changes2 it rose from the sea1 was again covered with ice1 and many parts of ,europe were devastated by immense glaciers--that of the ,rhone extending for more than two hundred miles4 ,then came vegetation as the ice gave way1 and luxuriance of the tropics reigned2 more cold after that1 then more heat1 till the ice was finally driven to its mountain fastnesses1 and 8,britain for the last time became continental4 ,neolithic man came upon the scene2 his palolithic predecessor had1 as far as ,britain and northern ,europe are concerned1 vanished for ever40 ,the inquiry respecting the arrival and presence of man in ,britain would lead us too far in pursuit4 ,the fact has been established that man was living in the ,thames valley while tropical animals were in the country1 and he has been classed by ,professor ,boyd-,dawkins amongst the mid-pleistocene mammalia1 and at that distant period1 man as man1 and not as an intermediate form connecting the human race with the lower animals1 was present in ,europe4 ,the stone implements which have been found in river beds and in caverns1 associated with the bones of various animals1 such as the elephant1 rhinoceros1 hyna1 bear1 and others prove this4 ,these very ancient and rudely-fashioned implements have been divided into two classes1 the ,palolithic and the ,neolithic1 by ,sir ,john ,lubbock4 ,first the stone implements were used1 and stone was superseded by bronze and iron4 ,then we come to the historic period4 ,in the neolithic period we find stone implements in the lake dwellings of ,switzerland and ,constance 7as well as the ,lake of ,neuchatel71 all of which have lately developed many treasures4 ,bronze tools have also been found1 and so the gradual progress of man as a fashioner of weapons can be traced from age to age4 ,from the 8river-drift0 man we descend to the cave-man1 who is supposed to have been identical with the ,esquimaux4 ,when ,britain became an island the cave-man seems to have disappeared from our country1 and in the prehistoric age the earliest of the present inhabitants came here1 and brought with them domestic animals2 then the ,celts of the bronze age1 and then the iron4 ,the wild beasts gradually disappeared1 and domestic ones occupied their places under civilized conditions4#cj ,so we come from the 8,glacial period0 to the open door of history through the antechamber of the prehistoric time4 ,the prehistoric is the arbitrary division between the post-pliocene or pleistocene and the known 8historic0 periods of the world's history1 and we must dismiss it with a few general remarks1 for the changes which we have attempted to follow are still taking place in the earth2 volcanoes and earthquakes are unsettling the strata1 and adding to the physical and geographical record which will some day have to be written by posterity and future geologists4 ,we can see in those prehistoric times traces of men 7hunters and fishers7 existing with difficulty1 mayhap1 in the midst of enormous quadrupeds1 and fighting for existence with the bears and many other formidable foes4 ,we have noticed the stone ages1 the rough and the smooth as they may be called1 and we can picture the primitive agriculture and work of the neolithic man4 ,but it is by no means to be believed that neolithic man in ,britain was a race all over the world4 ,we may assume that in eastern climes the human race were in a more civilized condition as improvements made their way slowly westward4 ,our island history commences in the time of ,julius ,csar4 ,eastern chronicles go back many thousands of years farther4 ,illustration3 ,fig4 #fhh4--;,carboniferous ,flora4 ,it is so short a time1 geologically speaking1 since man appeared within the limits of history1 that the earth's changes1 except from direct volcanic action or water erosion1 are very trifling4 ,the change is1 as we said1 continually proceeding2 ceaselessly the earth is wearing away1 and depositing her riches where she is undisturbed by civilization and man's excavations and intrusions4 ,the rock is worn by water2 the grit is carried down and deposited to form sedimentary rocks as of old2 the lime will continue to assist the coral to be built up2 and the chalk cliffs will be born under the sea1 and our organic remains shall be found to tell remote ages that we were an enlightened people4 ,for all we can tell1 and it is by no means unlikely another recurring cycle of ,arctic and ,tropical periods will in time pass over our earth2 the bear and reindeer1 the hippopotamus and the rhinoceros1 may again inhabit our islands4 ,if our generation be destroyed1 the purely animal creation with the vegetable world will reign over the land1 and new forests will deposit new coal measures for the support and comfort of a new generation of highly organized beings1 when our remains shall have passed away to the borders of a 8prehistoric0 age4 ,we have seen in the foregoing brief sketch how the world has arrived at its present beautiful condition1--how it has been step by step prepared for us1 how nature's forces have been and are still working according to the immutable laws of the ,universe4 ,and1 after all1 how little we know6 ,what scraps of intelligence only are we able to gather up from the boundless quantity of material which must have been laid down1 yet what wondrous results scientists have been able to adduce from even these comparatively scanty specimens6 ,the sea and land are ever telling us the same old story4 ,man's research and ,bible teaching are found hand in hand in cordial and reverent agreement4 ,nothing is altered since the day that the ,divine command1 8,let there be light10 went forth into space1 and till the earth be destroyed the same forces will continue in operation1 guided by the ,hand that made it--8ever faithful1 ever sure40 ,,footnotes3 #bh ,it might reach #ad1jjj1jjj of miles at a maximum4 #bi 8,physical ,causes of ,change of ,climate10 ,phil4 ,mag41 #ahfd4 #cj ,see ,dawkins' 8,early ,man in ,britain40 ,,chapter ,,xlvi4 ,,physical ,,geography4 ,,igneous ,,rocks--,,land ,,and ,,water--,,springs1 ,,wells1 ,,and ,,geysers--,,snow ,,and ,,ice--,,their ,,effects4 ,in the foregoing pages we have chiefly considered the stratified rocks1 but we are now approaching another branch of our subject--viz41 8,physiography10 which1 as distinguished from the usual so-called ,physical ,geography1 will deal with the phenomena of the earth1 air1 and water1 thus leading us to ,meteorology as a conclusion4 ,we have arrived at a certain knowledge concerning the ,earth as a planet1 her place in the universe1 and the composition of the 8,crust10 as it is termed4 ,we have examined the stratified rocks1 which include sand and gravel1 stones1 and boulders equally4 ,to a geologist they are all 8rocks40 ,we must now examine the igneous rocks1 which bear an important part in the structure of the ,earth1 whose surface we have now more minutely to examine4 ,it has already been stated 7p4 #ega7 that igneous rocks have been upheaved while in a state of fusion--that is1 while in a melted condition4 ,these igneous1 or fire-produced rocks1 are divided into classes1 just as the unstratified rocks are1 and the divisions are called the ,,volcanic and ,,plutonic1 including 8,basic0 and 8,acidic10 according as they are possessed of less silica or more4 ,sometimes the igneous rocks are classed as volcanic1 trappean 7from trappa1 a stair1 such as in the ,giant's ,causeway71 and granitic4 ,the volcanic in such case being the modern or upper rocks1 such as lava1 scoria1 etc41 which1 having been cast up by volcanoes1 are of comparatively recent formation4 ,the ,,volcanic rocks1 then1 are of recent date1 comparatively speaking2 they form the constituent portions of the volcanoes of the present day1 and are found as basaltic formations4 ,they are traced as far back as the ,tertiary period of the globe4 ,amongst the volcanic rocks we find basalt1 augite1 porphyry1 serpentine1 pumice1 pitchstone1 felspar1 etc4 ,but no doubt volcanic action has been going on ever since the beginning of the world as it is now1 and will continue to do4 ,it is somewhat curious that the very old igneous rocks should not be more evident4 ,the ,,plutonic rocks do not differ essentially from the foregoing4 ,there is less quartz and more hornblende2 and if the ages during which these formations have been existent in the earth-depths after they became solidified be considered1 the differences will be fully accounted for4 ,the greenstones and syenites are prominent amongst the plutonic series4 ,these plutonic and volcanic rocks are separated into basic and acidic1 as already remarked1 but the line cannot be drawn very distinctly4 ,granite is the chief plutonic 7acidic7 rock1 and we frequently find it forced upwards into other strata1 its essentially eruptive character being thus decided4 ,that granite must have taken an immense time to solidify and crystallize is evident1 for no new granites are ever found4 ,we find granite in all the old mountain chains--such as the ,grampians in ,scotland1 and the ,wicklow mountains4 ,our chief ,european 7active7 volcanoes are1 so to speak1 modern1 as may be supposed when their constituents are known4 ,it may be said that granite was first deposited as sediment heated by subterranean fire1 and forced up by thermal action of water to the mountains1 where it is uncovered by a slow process of denudation and surface washings of the earth4 ,now without at present going any farther into the causes of volcanoes we can see at a glance that the eruption of the igneous rocks must have created a marked and essential difference in the physical geography of the globe4 ,it is to these eruptions that the dislocation and disturbance of the stratified formations are due4 ,the igneous rocks present ridges in the mountains2 sometimes they are rounded at the summits1 while the aqueous and metamorphic rocks are disposed in layers4 ,illustration3 ,fig4 #fhi4--;,crater of ,popocatapetl4 ,these two classes in their varieties form the land and the crust of the earth1 which is ever being acted upon by air and water4 ,the ice1 again1 polishes and scratches the valleys in which it moves4 ,the loosened boulders that tumble from the mountains are carried down by the ice1 and deposited in the glacier moraine1 whence flows a stream4 ,by degrees the stone is ground up1 and carried away in the water to form sediment in a 8delta0 at the embouchure1 or to lie beneath the surface and form rock once more4 ,the igneous rocks1 composed of lavas and ashes1 are volcanic rocks1 deposited deep down1 and then after the lapse of ages disclosed by the action of air and water4 ,the consideration of the land and water upon the globe shows us that they are distributed over the earth very unequally4 ,there is nearly three times as much water in our planet as there is land1 and these proportions could not be altered without giving rise to phenomena1 the results of which cannot be properly estimated4 ,our earth has an area of #aig1jjj1jjj of square miles2 about #eb1jjj1jjj of this is land1 and about #ade1jjj1jjj of it water2 so about three-quarters of the globe is made up of water4 ,the first portion of our subject therefore should be directed to the examination and consideration of water1 and the phenomena which arise from its presence upon the earth4 ,illustration3 ,fig4 #fij4--;,distribution of land and water4 ,we need not go into details which every geography indicates4 ,we will try to trace the sources1 not the plain effects1 which all can afterwards study from special books4 ,in a preceding portion of this volume we have explained the chemical composition of water1 and we showed by experiment that it is a fluid composed of oxygen and hydrogen gases1 in the proportions of one to two volumes respectively4 ,no matter in what form water may appear1--as water1 as ice1 or as steam1--these proportions never vary in pure water 7see p4 #ceb74 ,but water on the earth is seldom1 or never1 pure4 ,we know the difficulty we have to procure good drinking water1 and though it may be filtered1 there will remain natural salts1 which are found in different degrees in all water upon the globe4 ,we know the rain1 which is perfectly pure when condensed from the clouds1 absorbs carbonic acid1 etc41 from the atmosphere4 ,we have shown how this water as soon as it comes upon the earth attacks the rocks1 and as it progresses carries away lime4 ,after descending deep down1 it rises again in the form of ,,springs4 ,now what are these springs8 ,they are the result of percolation of rain-water through certain strata4 ,when water falls it is absorbed into the ground1 unless it happens to rest upon an impermeable rock1 in which case it becomes a rivulet4 ,but it can penetrate between the atoms of many rocks1 and thus falls through sand and harder rocks1 till it reaches a stratum which will not receive it--like clay4 ,we then find that it will flow away in a spring1 or if tapped will be an ,artesian well4 ,these water-wells are of very ancient date1 but the name is more modern4#ca ,the springs flow out1 and develop1 with the assistance of tributaries1 into rivers4 ,these again receive more tributaries1 which swell the volume of their waters1 and widen out1 carrying millions of gallons hourly to the sea with sediment and gravel and stone4 ,illustration3 ,fig4 #fia4--;,distribution of land and water4 ,water has enormous power of disintegration4 ,we have only to cast our eyes upon the illustrations in any volume of continental travel in ,europe or ,america to perceive the gorges and caons worn out by the resistless and frequently gently-flowing river to estimate the part which water plays in ,physical ,geography and ,meteorology4 ,but springs occur not only in the case mentioned2 there are mineral springs1 hot springs1 and oil springs1 all following the same rules of nature4 ,the ,artesian well has been mentioned4 ,the ,geysers of ,iceland have often been portrayed1 and are amongst the most wonderful phenomena of nature4 ,these will serve as a type of the other thermal springs1 of which the districts of the ,yellowstone in ,north ,america afford perhaps the most extraordinary instances4 ,these are intermittent springs1 and the water rises to a great height1 at intervals of about an hour and a half2 and after many successive attempts1 or trials1 as it were1 the geyser shoots up to a great height enveloped in steam4 ,the cause of these well-known phenomena have been explained by ,bunsen1 and it has already been referred to4 ,we know that at a certain air-pressure water boils at #bab 7,fahr471 but on mountains at less pressure it will boil before that degree1 because the air is rarefied4 ,so conversely1 under the ground1 it may reach #bab without boiling4 ,so the surface 7warm7 water falls1 and reaches a high temperature before it is converted into steam4 ,when it is so converted1 the vapour is formed very rapidly1 and the expansive force is tremendous1 shooting up the water and all the contents of the tube with terrific violence1 and with a beautiful effect4 ,pressure therefore alters the boiling point of water4 ,illustration3 ,fig4 #fib4--;,geyser of the ,yellowstone4 ,the mineral springs of ,bath and many continental towns owe their properties to the solvent power of water1 which assimilates the mineral atoms and gases4 ,they arise just in the same way as the ordinary spring1 the taste and smell depending upon the soil and strata4 ,perhaps the oil wells are the most curious phenomena of this kind4 ,they are excavated upon the ,artesian principle4 ,the petroleum is bored for1 as we bore for water1 and the oil rushes up with great force1 and in enormous quantities4 ,gas wells are also to be found in ,pennsylvania1 and have supplied towns with gas for years4 ,both these ,artesian wells are caused by the decay of vegetation4 ,the gas is in the coal formation1 and the oil has been pressed out from vegetable deposit1 and as anthracite is a stony coal1 petroleum is a kind of coal-tar1 of natural formation4 ,we have alluded to the river1 which emerges from the spring1 which has fallen as rain4 ,but there is another1 and1 to many minds1 a much more interesting form of the universal fluid we call water4 ,this is ice4 ,familiar as ice is1 either to the stay-at-home invalid1 the skater1 and the traveller1 there is a great deal to be said about it4 ,it is a subject we would dwell upon had we space1 for the remembrance of many a pleasant hour passed upon snow and glacier call upon us to go back again1 even though only in imagination4 ,no one who has not climbed the glacier--even the ,mer de ,glace to the ,jardin1 now such a common excursion--can fail to be struck with the beauty and grandeur of the scene presented to him1 and to carry away a fond recollection of the icy regions he penetrated4 ,illustration3 ,fig4 #fic4--;,colorado ,caon 7effects of water erosion74 ,for the ordinary hard-working man there is no change1 no rest so truly beneficial as a trip amongst the mountains and snowfields of ,europe4 ,he need not be a climber2 that is1 a climber like ,tyndall or ,whymper1 those giants of the ,alpine ,club4 ,but a stroll up to the ,bel ,alp1 the ggishhorn1 the ,riffel1 the ,montanvert1 or the ,grimsel1 will give the average pedestrian some of the finest glacier scenery in ,europe1 and which may1 we believe1 compare with any in the world for beauty4 ,these glaciers--ice-rivers--we will now consider briefly4 ,we may take the ,mer de ,glace as an example 7see the illustration1 p4 #eif74 ,that gives us a very fair idea of the ice-river1 but the cut below is a good specimen of a glacier4 ,suppose we start up from ,chamouni1 or come across from ,argentires1 we shall reach the ,montanvert by ascending through the wood1 or by the 8,chapeau10 across the ice-sea4 ,as we take the former course1 we walk alongside a white-flowing and rapid river1 the ,arve1 which unites with the ,rhone below ,geneva4 ,this river divides1 and if we keep alongside one 7the right or south branch71 we shall reach the moraine and the icy grotto1 from which the water issues4 ,it is in this way many large rivers are born4 ,the ,rhine1 the ,rhone1 the ,aar1 the ,ticino1 have all of them their sources in the ice4 ,the ,visp and the ,sass waters are other almost equally well-known examples4 ,illustration3 ,fig4 #fid4--,source of the ,rhine4 ,there used to be a grotto or cavern1 into which the tourist could enter at the source of the ,arveiron1 and here the beautiful blue of the ice could be studied4 ,from this place the ,chapeau is reached1 up a stony path amid the trees1 and from the top outside the hut we can see the ,mer de ,glace all broken and contorted4 ,the frequently occurring roar of a falling rock which heat has deprived of its icy support1 or the cracking and tumbling of ice-blocks1 may be seen and heard in the forenoon4 ,but the grandeur and majesty of the ice and snow-clad mountains is best enjoyed by moonlight4 ,on the ice we shall see huge stones and gravel and grit1 which have been carried down by the ever-moving glacier1 which is denuded in its course1 and worn down upon the surface as it slides1 scraping and grinding the valley through which it flows4 ,by passing along a path now made easy by irons1 but formerly without supports or guards1 the surface of the glacier will be reached1 and a man with a hatchet will cut steps for the timid traveller4 ,we are now upon the deep ice-river1 which has its springs in the snowy regions of the ,col de ,gant1 in the snow which is continually falling upon the heights1 and draining away to water again to form a river4 ,thus the circle of events is completed1--snow1 nv1 ice 7glacier71 water1 which last is again absorbed into the atmosphere1 and again descends as rain or snow4 ,and this is always going on by the action of the sun4 ,it may here fairly be asked how snow becomes ice4 ,why does not the snow turn into ice at once1 and form a glacier at the top of the mountain as well as at the bottom8 ,we will endeavour to make this clear4 ,snow is composed of crystals1 which assume certain definite forms1 and when first the flakes fall they are soft and powdery4 ,by degrees they melt a little1 and when unconsolidated form what is termed nv1 the border line between ice and snow4 ,this semi-icy snow descends under pressure1 and1 as it increases1 the glacier is formed by huge blocks and masses being pressed together on the steep slopes of the mountains4 ,thus the glacier descends1 rounding off rocks1 and scouring as it goes1 moving at a certain estimated rate daily1--about twenty inches on the average1--carrying stones and dbris which form the moraine1 and finally when the high temperature in the valley melts the ice1 it issues forth as a river into the plain1 or bounds down the mountain side in a cascade4 ,an excursion--and one by no means dangerous if a guide be taken--to the ,jardin1 near ,chamouni1 will reveal many interesting features of glacier formation1 and of the glaciers themselves4 ,illustration3 ,fig4 #fie4--;,glacier table4 ,physical ,geography is therefore very much indebted to the action of water as a fluid or as a solid4 ,in the former condition it erodes the rocks1 carries down the stones and gravel and sand1 forms deltas at the mouths of rivers1 and elevates plains by overflowing its banks and depositing sediment4 ,water gives beautiful scenery1 and the ever-changing features of the landscape are due to it4 ,from the time the spring emerges to the time when it has developed into a river1 bearing fine ships upon its restless waters1 the universal fluid is always at its work of destruction and benefit combined4 ,from the limpid stream we pass to the salt ocean1 the reservoir of all the waters of the globe4 ,illustration3 ,fig4 #fif4--,life under water4 ,we have in this chapter briefly considered two very important forces which have much to do with the varying conformation of the earth--viz41 fire and water in their results of volcanic action and erosion4 ,the sea will tell us something more4 ,,footnotes3 #ca ,from ,artois1 where the first ,european well of this kind existed4 ,,chapter ,,xlvii4 ,,the ,,sea ,,and ,,the ,,sky4 ,,the ,,sea--,,salt ,,water--,,waves ,,and ,,their ,,effects--,,under ,,water--,,the ,,floor ,,of ,,the ,,ocean4 ,from our childhood the sea has been the companion and playmate of thousands1 the seashore their playground4 ,men have selected it for their professional training and livelihood4 ,authors write of it1 poets apostrophize1 scientists lecture upon it1 and fathom it1 bringing up from its depths many a new fact and illustration for those who cannot study it for themselves4 ,there is nothing like it1 nothing more majestic1 more beautiful1 more life-giving than the ocean--nothing so changeable nor so true4 ,from the days when we could toddle along the beach1 picking up the shells1 we have wondered at the ocean--,what was beyond it8 ,what did it conceal8 8,what hidest thou in thy treasure-caves and cells1 ,thou hollow-sounding and mysterious main80 ,let us endeavour to find out4 ,the first thing that strikes us is the saltness of the sea4 ,sea water is salt4 ,why8 ,one reason is because salts are carried into it by rivers1 and besides1 it is more beneficial as salt water4 ,but let us look at the facts4 ,we know that the earth contains many 8salts10 as we can see by the saline springs4 ,we have already given the chemical constitution of sea water1 but it will be useful to repeat the proportions4 ,water #ifdgdcgb grains4 ,salt 7,chloride of ,sodium7 #bhjeidh 0 ,chloride of ,potassium #jgfeeb 0 ,chloride of ,magnesium #cfffeh 0 ,bromide of ,magnesium #jjbibi 0 ,sulphate of ,magnesia #bbiegh 0 ,sulphate of ,lime #jdjffb 0 ,carbonate of ,lime 7with traces of ,iodine and ,ammonia7 #jjccja 0 ---------- #ajjjjjjjj 0 ---------- ,some portions of the sea are not so salt as others1 or1 in other words1 not so dense1 and the saltness of the water prevents it being frozen so quickly as fresh water1 which freezes at #cb4 ,salt water requires to be reduced to #bh before it freezes4 ,besides the various constituents mentioned above1 sea water has been found to contain boron1 bromine1 strontia1 etc41 and even silver1 for the copper of ships has been found to be impregnated with that metal4 ,illustration3 ,fig4 #fig4--;,going out4 ,if there is so much salt in the sea1 it may be asked1 why does it not continually become greatly saltier by additions4 ,the reason is because tons of fresh water are continually pouring in1 and though we can scarcely doubt that the sea is becoming gradually more salt as years pass away1 the increase is very slight4 ,on the other hand1 evaporation is carrying water into the air and leaving the salt behind it4 ,in seas like the ,red ,sea1 where there is a great deal of evaporation and very little addition of fresh water in comparison1 the water is extremely salt and bitter4 ,the ,baltic has little salt relatively to some parts of the ,mediterranean4 ,supposing that1 as some allege1 there are rocks of salt at the bottom of the sea1 we must remember that springs of fresh water frequently bubble up to the surface of the ocean4 ,this is a very curious phenomenon1 and has been attested by ,humboldt4 ,he states that near ,cuba these springs arise with considerable force1 and the vessels trading on that coast get supplies of fresh water from these ocean springs4 ,there is1 or was1 a similar uprising in the ,gulf of ,spezzia1 and fresh water crustacea inhabit these localities4 ,these occurrences prevent the sea from becoming too salt by evaporation4 ,when salt water becomes tainted it is very offensive--much more so than fresh water4 ,if1 therefore1 the ocean were not continually in movement1 it would be very injurious4 ,so much for the water of the sea2 let us now see what it does4 ,we will glance at the surface ere we plunge into the depths4 ,in childhood1 and even in after years1 we most of us delight in watching the waves of the sea4 ,what finer sight than that we can obtain on the bold ,cornish coast with a westerly wind1 when the great ,atlantic waves come rolling in and dashing up to the tops of the ,tintagel cliffs1 wearing and grinding them away2 hissing up the sands at ,new ,quay1 or thundering on the shores of 8,bude and ,boss06 ,then the wind abates1 the sea goes down1 the billows become waves1 the waves to wavelets grow1 less and less1 until there is a mere ripple on the surface which is never still4 ,the mighty heaving of the ocean breast is the peculiarity of the sea4 ,illustration3 ,fig4 #fih4--,sea waves4 ,yet1 again1 as we stand to watch the waves1 or run from them as they sweep in foam upon the sloping sand1 we shall find that they increase or decrease in force1 and the level of the water rises or sinks by degrees4 ,the tide is flowing or ebbing as the case may be4 ,so we know the surface has another--a current motion--besides the undulation of the water4 ,the currents of the ocean are very valuable attributes1 the ,gulf ,stream in particular bringing us warmth and1 indeed1 rain4 ,there are three movements of the ocean--waves1 currents1 and tides4 ,the waves1 perhaps1 interest us most1 as they come rolling in with irregular force1 but all mightily impelled by the wind4 ,we have all noticed the ripples on a puddle2 the same action of the wind produces the grandeur of the waves of the ocean4 ,the wave comes rolling in before the wind to break against the rocks or beach1 and another forms to break in its place2 the higher the waves the more quickly they appear to move4 ,but when the wind has subsided the rolling1 or 8swell10 remains1--a long1 lazy1 undulating motion--a rocking to sleep of the billows of the sea4 ,without a ripple on the surface these huge rollers will glide towards the shore and break upon the shingle with a roaring sound which can be heard for miles1 dragging the pebbles after them as they recede with a rattling like bones and marbles4 ,the pebble ridge at ,westward ,ho6 will illustrate this vividly at times1 the sound being heard far inland like continuous thunder1 and on a calm night1 when there is no wind stirring1 the roar of the ground swell is weird and mysterious in the gloom4 ,illustration3 ,fig4 #fii4--,the ,piroroco on the ,amazon4 ,the height of waves is very varied4 ,observers say that forty-four feet is about the highest-known wave from hollow to crest4 ,waves of thirty-five feet have been often met with1 and off the ,irish coast and in the ,atlantic sailors tell of waves 8as big as houses40 ,but houses differ in size as do waves4 ,the rate which waves are estimated to travel varies with the wind-propelling force4 ,the average hurricane wave travels at about forty-five miles an hour4 ,but earthquake waves--those set in motion by subaqueous disturbance--have been known to travel at the rate of six hundred feet in a second for thousands of miles across the ocean4 ,such a one occurred after the earthquake which destroyed the town of ,arica in ,august #ahfh1 and the wave crossed the ,pacific to ,chetham ,islands1 #e1ebj miles1 in fifteen hours and twenty minutes4 ,we have many of us seen the great tidal waves1 or 8bores10 which at certain seasons rush up our rivers--the ,severn1 for instance--with great violence1 and at times forty feet high4 ,these tidal waves are also experienced in the ,ganges1 the ,amazon1 and at ,bordeaux1 as well as in ,china and elsewhere4 ,it may well be imagined that the tides also affect the land1 and the theory of these ocean movements is a very interesting study4 ,we have already referred to it under ,,astronomy1 for the ,sun's and ,moon's attraction is the main cause of the phenomenon1 which is so familiar and yet so strange4 ,but the consideration of the tides must be again entered upon here ere we proceed to view the effects of the sea upon the land1 and how the physical geographical features alter4 ,isaac ,newton rightly attributed the cause of the tides to the attraction of the moon and sun4 ,spring tides occur when both luminaries are above the meridian1 and the neap1 or low tides1 happen when the sun and moon are farthest apart4 ,the highest tides are perceived after a new or full moon2 the lowest1 after she has passed the first or third quarter4 ,in ,january the spring tide is highest of all1 because the earth is nearest to the sun then1 and his force of attraction1 added to that of the moon1 causes a very high tide4 ,with the assistance of the accompanying diagrams we shall be able to make the tidal phenomena clear4 ,illustration3 ,fig4 #gjj4--,tidal ,attraction4 ,illustration3 ,fig4 #gja4--,tidal ,attraction4 ,suppose the moon to be at ,m1 the point ,j 7the sea7 will be nearest to the moon and will be attracted1 while the earth will exercise a retarding power to a certain extent4 ,this attraction of the water from its usual level causes a kind of vacuum1 into which the surrounding water flows and causes a high tide at ,h4 ,at the opposite side the earth1 not the water1 is most attracted1 and then the water rushes in to a certain extent to fill the vacancy left by the earth's movement towards the moon4 ,another high tide is therefore caused at ,l1 but not so high as the tide upon the opposite side1 as the ,moon is so much nearer the latter4 ,the tide1 then1 is only the natural movement of the sea water to fill up the space the earth and other portions of the watery mass have vacated in obedience to lunar and solar attraction1 which is1 to a certain extent1 counterbalanced by the attraction and resistance of the earth4 ,the neap tides are caused by the opposing forces of attraction of the sun and moon4 ,the sun1 as it were1 pulls one way1 the moon the other4 ,the latter 7being nearer7 having twice the power of the former1 causes a tide indeed1 but it is a low one4 ,the spring tide occurs when sun and moon together attract the water4 ,the effects of the rise of the tide are sometimes very disastrous1 and when the wind assists the sea1 and heaps up the water1 the sight is grand in the extreme4 ,on the coast of ,schleswig1 at ,hallingen1 the sea has washed away a whole cluster of islands1 and now the waves cause tremendous inundations4 ,about every six years1 on the average1 a great flood happens for such trifles as a high tide are of no account4 ,in #acfb and in #ahcd terrible destruction was wrought2 the coffins and bodies were washed out of the graves4 ,piles of dbris are then washed up1 and sand and gravel accumulates for a time till again carried away4 ,travellers to ,france will notice the 8dunes10 or sandhills of ,calais1 as the train winds its way to ,boulogne4 ,we find that whenever the shore is flat the shingle and sand are blown inwards and form 8dunes10 and the sand is distributed far inland1 checking all vegetation1 and altering the features of the country4 ,the wearing away of rocks by the water1 the continual undermining of them by the waves1 and sometimes the disengagement of great blocks weighing many tons--all these effects of the sea tend to alter the appearance of the land4 ,we may observe the denudation in many places along the coast--the caves1 holes1 and tunnels eaten out by the water4 ,in ,norway the 8,fiords0 are very remarkable4 ,they were formed by the upheaval of the land1 and tell us of the glaciers which once filled them up4 ,thus by ice and water the solid land is ground down and eaten away hourly1 daily1 and for countless centuries1 changing the place of the hard rock into a standing water1 and the flintstone into a springing well4 ,illustration3 ,fig4 #gjb4--,the ,dunes4 ,we must now plunge beneath the waves1 never fearing the rough surface2 we shall find all smooth and quiet at the bottom of the sea4 ,,the ,,bottom ,,of ,,the ,,sea4 ,what can we tell about the bottom of the sea to which no man has ever reached living1 and from which we have no information8 ,we can lay our telegraph or telephone lines beneath the waves1 and far from the restless waves in those quiet depths where no billows can reach4 ,what treasures must lie hidden at the bottom of the sea6 ,the treasures1 the gold and silver1 the merchandize1 the wealth of centuries4 ,the sailor lies sleeping there 444 8,serene and safe ,from tempest and from billow2 ,the storms that high above him chafe ,ne'er rock his peaceful pillow06 ,what can we hope to find at the bottom of the sea we cannot reach8 ,yes1 but we can reach it4 ,by sounding with ,brooke's lead 7a cannon ball1 as shown in the illustration71 we can arrive at a certain knowledge of the composition of the ocean bed4 ,the right-hand figure of the two is the lead when being lowered1 and while it is sinking the cord remains tight4 ,so soon as it touches the bottom the weight of the cannon ball divides the line1 and the tube is easily drawn up again4 ,it has been well greased1 and so in the cavity of the rod some shells and sand are found adhering4 ,these fragments tell us the composition of the bottom of the sea4 ,here we find tiny shells1 just as we find them in chalk1 the same formation as that which piled up the cliffs which have risen from1 or been discovered1 by the sea4 ,by other ingenious contrivances water can be fetched up from the bottom of the ocean1 and the temperature can be gauged all along the sounding line4 ,the expedition of the ,challenger brought many interesting facts to light4 ,far down in these solitudes are marine animals1--crustacea1 star-fish1 seaweeds1 and shells1--all of which are carried up by the dredge worked by a steam engine2 for the resistance is very great1 and the weight supported at the depth of two miles must be considerable1 and is equal to four atmospheres4 ,a thermometer has come up crushed even in its iron case1 and so the creatures which inhabit and find means to live at the bottom of the sea must be specially fitted by ,nature for the locality4 ,illustration3 ,fig4 #gjc4--;,brooke's ,lead4 ,the configuration of the ocean bed has given rise to many different opinions4 ,it has been maintained that there are mountains and valleys1 hills and dales underneath the water1 all clothed with marine vegetation1 equal in height and depth to the terrestrial hills and vales4 ,again it has been declared that the ocean bed is level2 but we find raised portions1 which we call islands1 which may be the tops of mountains1 or portions of the mainland separated from their parent continent by an inroad of the sea1 as are our islands of ,great ,britain4 ,the sea-bed1 however1 is very irregular4 ,we find deep and steep valleys1 and high hills1 but the picturesque peaks caused by the action of air1 frost1 and water on earth are not1 of course1 represented under water4 ,between the ,irish coast and ,newfoundland we are told the bed is level for nearly four hundred miles4 ,there is a deep declivity before we reach this plain4 ,the centre of the ,atlantic is a plain1 and on it the most volcanic islands rise1 such as ,ascension and the ,azores4 ,between ,england and ,greenland there was at one time a land communication1 as we have remarked under ,,geology1 and there are submarine terraces now4 ,an immense river once ran through ,western ,europe somewhere about where our islands are4 ,illustration3 ,fig4 #gjd--,the ,drag ,net4 ,under the ,atlantic we have remains of foraminifera and other tiny animals1 with red clay and volcanic remains which must have been of submarine origin4 ,the ,pacific shows us tops of mountains as islands 7,hawaii ,isles71 and an enormous range must be hidden beneath the waters4 ,what a change in the physical geography of the earth a slight sinking of the water of the ocean would make2 ,england and the ,continent would be united1 and many sea-mountains 7islands7 discovered4 ,the greatest ocean depth is four miles and a half1 but in many places a few hundred feet less depth than at present would reveal many changes in the land4 ,every year since the world has gained its present form the streams and rivers have been pouring water1 and carrying mud1 stones1 and gravel ceaselessly into the ocean4 ,in addition to this1 the surface water washes the stones away1 animals 7corals7 build up islands from the depths1 and take up space in the ocean4 ,we know that if we put our hand in a basin full of water we displace a quantity of the fluid2 so we might imagine that1 the sea being already full1 every island formed would tend to an overflow of the sea1 and the land would be thereby buried4 ,that the sea does encroach upon the earth we know1 but it also recedes4 ,here is the balance of ,nature4 ,rivers pour in water and material4 ,the sun absorbs the water and prevents overflow2 tiny animals make shells from the material4 ,all the causes we have mentioned tend to permit the encroachment of the waters1 but volcanic action and even earthquakes act also to neutralize this tendency by upheaving hills and mountains1 which prevent the invasion of the sea by its elevation or by land depression4 ,we have seen in our chapters upon ,,geology how the ocean beds have been upheaved1 and remains of marine animals are daily found upon our highest hills4 ,thus the forces which sometimes cause such destruction in the earth are the means whereby the waters are kept in their places4 ,but for volcanic action the land might all disappear by denudation and continual wear and tear1 and be deposited at the bottom of the sea6 ,if it were not for currents1 of which many defined ones exist in the ocean1 and the never-ceasing flow and ebb of the tides1 the sea would soon lose its purity and clearness4 ,though the water is salt and becoming salter1 animalcul and all kinds of plant-animals would still increase and multiply2 so the decay of animal and vegetable matter would quickly render the ocean a source of pestilence and death to mankind1 and be most injurious to animal life generally4 ,but the movement is so ceaseless1 and the various fish and mammalia 7whales1 for instance71 by preying upon each other1 as other animals on earth do1 keep up the balance of production1 and the organic matter deposited in the sea is also cleared away4 ,that the constant currents of the sea prevent the formation and growth of seaweed is clearly shown by the great 8,sargasso ,sea10 or tract of weed 7,fucus natans71 called the ,gulf-weed4 ,this great tract embraces thousands of square miles1 and is situated in the very middle of the ,atlantic ,ocean1 where there are but few currents2 but surrounding it is the ,gulf-,stream1 an enormous current of water running at a regular rate of four or five miles an hour4 ,this ,gulf-,stream is supposed to be caused by the same laws and influences which determine the trade-winds--namely1 a constant rarefaction of the water at the tropical parts of the earth1 and a corresponding condensation at the ,arctic portions1 for warm water is much lighter than cold1 and when the waters of the tropical regions become lighter1 the heavier waters of the cold regions pressing down more forcibly tend to raise them above their proper level2 they therefore flow towards those very parts which have sunk down by their contraction1 and a constant current takes place2 this current is the ,gulf-,stream4 ,it runs from the ,gulf of ,mexico northwards towards ,newfoundland1 turning by ,iceland towards the ,british ,isles1 by ,france and ,spain1 onwards to the coasts of ,africa and ,south ,america1 the ,west ,indies1 and again to the ,gulf of ,mexico1 although the return current does not go by the name of ,gulf-,stream4 ,this great stream of water1 warmed by the tropical sun1 serves the same two purposes fulfilled by the trade-winds--namely1 a circulation and distribution of the superfluous heat of the equatorial regions1 warming the northern countries2 and cooling1 by the return of under-currents1 those in the tropics4 ,the fogs of ,newfoundland are caused by the great current of warm water entering the cold region and carrying with them surface-currents of moist air1 which the cold condenses into fog1 just as the breath is visible in a cold atmosphere4 ,england owes its moist and mild climate to the same cause4 ,the depth of the ,gulf-,stream itself is very little4 ,it is a mere layer of warm water4 7,see ,sir ,george ,nares' reports of the ,challenger expedition47 ,illustration3 ,fig4 #gje4--;,atoll1 or ,coral ,island4 ,in the foregoing pages you have now seen1 and1 we hope1 gained1 some information concerning the sea sufficient1 at any rate1 to induce you to enter more deeply into the subject than we can at present do4 ,we have learnt how the sea water is composed1 and what goes on on the surface4 ,we have discussed waves1 and referred to tides and currents1 the wearing away and the renewal of land by the sea2 we have dived beneath the surface1 and found something to interest us at the bottom of the ocean4 ,as we come up again we are surprised to find islands or reefs where none existed when we went down4 ,what has caused this sudden appearance8 ,they may have been slowly raised to the surface by coral insects1 or suddenly by volcanic action4 ,let us consider the coral1 which plays a very important part in our ,physical ,geography1 before we proceed to the volcanic island4#cb ,the low-lying islands are those formed by the skeletons of the coral insects1 and the ,coralline ,islands are some of the most wonderful productions of nature4 ,they are only found in warm climates1 between the twenty-eighth degrees of north and south latitude1 and limestone pure and simple is the chief component of the coral reef1 as it is of the mountains erupted from the depths of the sea4 8,the detritus of corals1 echinodermata shells1 reticularia1 and other living creatures10 says a writer on this subject1 8deposit not only the salts of lime extracted from the ocean1 but their own dead bodies to form the hard substance of the rock40 ,illustration3 ,fig4 #gjf4--;,gorgonia guttata 7natural size74 ,illustration3 ,fig4 #gjg4--;,coral 7,madrepora brachiata74 ,illustration3 ,fig4 #gjh4--,spicules of ,gorgonia 7magnified74 ,the coral insect is a zoophyte 7,anthozoa71 which1 as may be seen from the illustrations1 assumes curious and elegant forms1 and the coral it produces is a limy or calcareous deposit1 which is fixed upon a rocky base4 ,as years go on these accretions become greater and greater1 and at length rise above the water4 ,when a little distance below it1 the reefs form dangerous and frequently unsuspected barriers1 upon which ships are wrecked4 ,the red coral is dredged up from the ,mediterranean1 where there are extensive coral fisheries4 ,this coral is found deep in the water1 and never rises to the surface4 ,formerly there were coral reefs in the ,european seas1 but the changes of temperature stopped their production4 ,the 8atolls10 or circular coral reefs with an opening at one side1 have been described by ,professor ,darwin4 8,who10 says the great naturalist1 8would not be struck with wonder and admiration on catching sight for the first time of this vast ring of coral rock1 often many miles in diameter8 ,sometimes a low green island is seen beyond it1 with a shore of dazzling whiteness2 outside is the foaming surf of the ocean1 and within it a broad expanse of tranquil water1 of pale green colour and exquisite purity40 ,these 8atolls0 mark the situation of sunken islands1 and the extension of them and the barrier reefs would seem to indicate a slow but decided sinking of the bottom of the ,indian and other oceans2 but the 8reefs0 tell us that the land to which they are attached has not become depressed1 and may have become elevated4 ,we may then conclude that a continual rising and depression of the land is taking place in various oceans1 indicating a sinking of the ocean bed in one locality and the result of volcanic activity in another1 for no active volcanoes are found in the regions of depression4 ,we must now leave the sea and come to land again1 to consider volcanoes and volcanic action there4 ,,volcanoes ,,and ,,earthquakes4 ,the various phenomena of volcanoes form a subject very difficult to be explained1 as it is impossible to ascertain positively the cause of volcanic action4 ,whether the earth is interiorly a mass of molten rock and fire1 or whether the heat is created by the intense contractile force and movement of rocks1 and their motion thus developed into heat aided by chemical combination1 we cannot absolutely determine4 ,the theory restricting volcanic phenomena to the upper crust of the earth1 by supposing the local accumulations of hot liquid masses of rock1 which are forcibly emptied by the expansion of vapours1 may perhaps be found the true one4 ,the majority of the volcanoes are found near1 or at no very great distance from1 the sea4 ,we may therefore expect to find that water has something to do with the eruptions as it has in the case of the ,geysers4 ,but this hypothesis will scarcely hold good in every case1 though volcanoes of later ages are limited to regions very different from those in which volcanic action used to be4 ,for instance1 in ,america we have only volcanoes on the ,pacific side1 and the ,andes furnish several4 ,mexico1 ,central ,america1 and ,california possess many volcanoes1 and as far north as ,alaska we find ,mount ,elias4 ,there are plenty of extinct volcanoes in ,europe1 but the ,mediterranean produces the active vents2 and about the ,red ,sea and the ,caspian1 and even in the central chain of ,asia1 there are volcanoes far from water4 ,the ,hawaii isles1 on the other hand1 are all volcanic1 and ,australasia furnishes us with remarkable specimens2 so altogether the testimony tends to prove that where volcanic remains are apparent the sea had at one time been1 or now is1 near at hand4 ,burning mountains have been familiar to us from our childhood in pictures1 and by stirring narrative of destruction wrought by them4 ,the volcano is generally a mountain rising to a cone1 but ,vesuvius presented quite the appearance of a hollow basin at the top1 before it suddenly broke forth and buried ,herculaneum in ashes4 ,von ,buck visited it in #agii1 and declares it had at one time risen1 like an island1 from the sea4 ,there are about two hundred and seventy volcanoes at present in activity2 four in ,europe2 eleven in ,iceland and ,jan ,meyen's land2 in ,asia1 ninety-three2 in ,africa1 twenty-six2 forty-six in ,north ,america and the ,aleutian ,isles2 twenty-seven in ,central ,america and the ,antilles2 in ,south ,america1 thirty-one2 and twenty-four islands with volcanic tendencies largely developed4 ,there may be many more 8resting40 ,volcanoes1 then1 are openings or vents which communicate with the melted rock within the earth1 and the conical form of volcanoes is owing to the deposits of volcanic matter as it falls from the opening called the crater4 ,if we let a small spade full of mould run through our hands1 or from the spade1 it will form a small cone1 the heavier particles sliding to the base at a certain slope4 ,thus the volcano builds its own hill1 and inside the crater we find cones from which smoke and steam issue4 ,these cones within the cone are the points of issue of vapour and smoke1 miniature volcanoes making up a whole4 ,illustration3 ,fig4 #gji4--;,eruption of ,vesuvius1 ,august #bfth1 #ahgb4 ,the signs of eruptions are much the same1 and usually occur a couple of days before the actual outbreak takes place4 ,first smoke is perceived1 perhaps1 and the escape of various noxious gases accompanied by earthquakes occur4 ,now the eruption may commence and blow away the summit of the mountain1 as in the case of the commencement of the catastrophe of ,a4,d4 #gi1 when the whole side of ,vesuvius was torn away1 and continuous showers of ashes fell for days and nights1 burying everything1 while the hot lava poured down the sides4 ,stones and ashes with vapours are hurled into the air4 ,clouds of steam are formed1 and vivid electrical discharges take place in these clouds1 while water dashes down1 carrying stones 78volcanic bombs071 and reflected lurid flames from within are cast on the steaming clouds1 which look like fiery columns4 ,then the lava issues in a white1 hot1 steady1 irresistible stream1 covering everything1 and burning up all vegetation4 ,illustration3 ,fig4 #gaj4--;,birth of a volcano4 ,new volcanoes are continually in process of formation1 and at ,santorin for hundreds of years volcanic action has been busy in forming islands4 ,these violent efforts of ,nature frequently give rise to earthquakes1 which are the most destructive of natural convulsions4 ,the records of late occurrences are fresh in the minds of all readers1 and need not be specified4 ,the slow subsidence and gradual upheaval of the land is still going on1 but we are frequently startled by the account of a rupture of the ground or the destruction of a portion of a city4 ,the motion of the earthquake is generally in a direct line1 and undulating4 ,sometimes what are termed vertical shocks arise and destroy solidly-built edifices4 ,mountains have been overturned by earthquake shocks1 and trees have been twisted round4 ,sometimes the ground yawns into enormous fissures4 ,the sea is tossed into great waves and encroaches upon the land1 and when the sea recedes the recession of the water is followed by a more terrible invading wave sweeping all before it4 ,earth tremblings often occur far away from volcanoes1 and without any visible connection with volcanic action4 ,there are many aspects of land and water which the student of geography will remember1 but which need not be separately treated of4 ,we must1 however1 refer to plains1 plateaus1 and lakes4 ,the mountains also play a most important part in ,physical ,geography and in 8,climatology10 as they collect the vapours for rain1 and make the valleys fertile1 and thick with vegetation4 ,we have spoken of the mountains under ,,geology1 and the various formations and strata will be found enumerated there1 but now we have to do with the mountain chains in their physical aspect as regards their shape and appearance on the globe4 ,illustration3 ,fig4 #gaa4--;,earthquake fissures4 ,any elevation rising from a base more than #a1jjj feet may fairly be termed a mountain1 and solitary mountains are usually volcanic1 because eruptive rock does not produce chains of mountains4 ,the origin of mountains is probably due to the contraction and compression of the crust of the earth--not merely the surface1 but the whole thickness between us and the supposed molten interior4 ,mountains did not exist from everlasting1 for the very good reason that they are 7in most cases7 composed of stratified rocks4 ,stratified rocks are sedimentary rocks1 and must have been deposited below water1 and hardened long before they were thrust up by pressure4 ,moreover1 we find 7as has already been explained7 shells and remains of marine animals on the higher summits1 which prove to demonstration that these mountains are composed of rocks which were laid down under the sea4 ,professor ,dana was one of the first geologists to advance the theory that contraction and lateral displacement are the causes of the elevation of mountains4 ,a very good illustration of this theory was made by ,chamontier1 who covered an india-rubber balloon with a thick layer of wax1 and when it had hardened sufficiently he pricked a hole in the bladder1 which immediately contracted1 and the wax at once rose up into tiny similitudes of mountains1 showing in a sufficiently clear manner that such protuberances may be produced by the pressure of the earth's contraction1 and in such a mass as our earth the elevations would naturally be very great4 ,professor ,geikie has shown how1 by a very simple experiment1 the contortion of mountain strata is effected by pressure4 ,a number of cloths or towels placed flat on a table represent the sedimentary rocks4 ,place a board with a weight on the top1 and the towels will remain flattened4 ,but by holding two boards at the sides and pressing them together 7the weighted board still remaining71 we shall find the towels crumpled and upheaved like the ,jurassic strata shown in the illustration 7fig4 #gab74 ,professor ,heim calls the central masses wrinkles of the earth's crust4 ,so the ,alps were pressed up or heaved into the air1 the weather--rain1 frost1 snow1 and sunshine--imparting the infinite variety of 8,horn10 8,needle10 and 8,peak10 so expressively applied in ,alpine nomenclature2--the ,matterhorn1 ,wetterhorn1 ,weisshorn2 the ,pic du ,midi1 ,aiguille de ,dru1 ,aiguille ,verte1 and many other mountains in well-trodden ,switzerland will occur to the reader at once4 ,illustration3 ,fig4 #gab4--;,anticlinal and synclinal curves of the ,jura ,mountains4 ,the slopes of mountains--though to the casual observer they may appear very much the same--are very different4 ,we sometimes find a long1 easy ascent1 --more usually a steepish inclination1 perhaps #bj2--;in other places1 such as on the ,matterhorn1 an almost perpendicular face4 ,forty-five degrees rise is very steep1 and #ec is the limit of any great mountain's slope4 ,cliffs and precipices there are1 of course2 witness the terrible fall from the ,matterhorn to the glacier below--thousands of feet with one tremendous leap from the rock to the ice underneath2 but mountain slopes are not precipices4 ,as a rule1 we find that one side of a mountain chain is steeper than the opposite one4 ,it is harder to climb up from ,italy to ,switzerland than to ascend in the opposite direction4 ,the ,pyrenees are also steeper on the south side4 ,the ,scandinavian mountains likewise are steeper in the west4 ,the ,himalaya are steepest towards the sea1 so are the ,ghauts4 ,we here find a difference between the slopes of the ,,new and ,,old ,,worlds4 ,in the former we have the less precipitous mountain slopes towards the east2 in the old world they are towards the north1 and an inspection of a physical map of the world leads us to the conclusion that the ,atlantic and ,pacific ,oceans are the boundaries of entirely different degrees of slopes4 ,the ,pacific and ,indian ,oceans would appear to border the more precipitous mountain sides2 the ,atlantic and its connections those less steep4 ,as a rule1 we have the most elevated portions of the earth1 mountains1 and high tablelands1 in equatorial regions2 and within the torrid zone every terrestrial climate is to be found1 owing to the snows of the high mountains and the heat of the valleys1 which are naturally closely connected with the upheaval of mountain ranges4 ,we have already spoken of the never-ceasing influences of the air and water upon the rocks1 and we need say little about valleys4 ,there are valleys of dislocation1 denudation1 and undulation4 ,the great valley of ,western ,asia1 wherein lie the ,caspian and ,aral seas1 seems to have been caused by the upheaval of the ,caucasus and the ,persian plateau4 ,,plains are very varied4 ,we have ,european ,heaths and ,landes2 ,american ,savannahs1 ,prairies1 and ,pampas2 ,asian ,steppes1 and ,african ,deserts4 ,all of these possess certain features in common1 more or less vegetation1 and sometimes absolute sterility4 ,,plateaus1 or ,tablelands1 are elevated plains frequently undulating in character4 ,the ,plateau of ,bolivia is #ac1jjj feet high1 and extends along by the ,andes4 ,the tableland of ,quito is nearly #aj1jjj feet high1 and borders on the giants ,cotopaxi and ,chimbarazo4 ,illustration3 ,fig4 #gac4--,the ,staubbach 7,lauterbrunnen74 ,rivers and lakes add not only to the wealth of nations by their usefulness1 but1 by the additional picturesqueness of their appearance1 to the beauty of the landscape4 ,the velocity of rivers would be very much increased if it were not for the strong resistance offered by the banks and the stones to the current1 and by friction4 ,the ,rhine and the ,rhone1 if thus unimpeded1 would flow at a rate considerably over one hundred miles an hour2 and our own little stream 7the ,thames71 instead of eddying peacefully and twirling gracefully by ,medmenham or ,cookham1 would rush along at the speed of the train which so often crosses it on its way to the sea4 ,the slopes of river-beds1 like the slopes of mountains1 vary very considerably1 and the inclination of a river varies at different places2 in a distance of seven hundred miles the ,amazon only falls twelve feet1 and the current flows chiefly by impetus already acquired4 ,a slope of one foot in two hundred precludes all navigation1 and at still greater inclines rapids and cataracts are formed--the great falls wearing away the river-bed by degrees2 so it is calculated that hundreds of years ago ,niagara ,fall was much farther down the river1 and the cataract is slowly moving up stream4 ,in time1 as the rock wears away1 the height will disappear as the celebrated 8,falls10 and will become a rapid within a few miles of the lake4 ,lakes are derived from river-drainage and springs4 ,some are very salt1 owing to evaporation carrying away so much water1 and leaving the accumulated mineral salts4 ,these very salt lakes are likely to dry up1 as the supply of water is not equal to the demands of evaporation4 ,floating islands appear and disappear on many lakes4 ,derwentwater is one instance4 ,on the uses of lakes and rivers it would be superfluous to dwell4 ,we are more concerned to examine their influence on climate1 and in this sense we must also consider mountains4 ,but we will now group all the phenomena of the air and water1 and their effect upon climate1 under 8,meteorology0 in the chapters next following4 ,,footnotes3 #cb ,those who wish to study the subject fully should read 8,corals and ,coral ,reefs10 by the late ,charles ,darwin1 and ,dana's 8,coral ,islands40 ,,chapter ,,xlviii4 ,,physical ,,geography4 ,,meteorology4 ,,the ,,atmosphere--,,winds ,,and ,,air ,,currents--,,wind ,,pressure--,,storms--,,rain-,,clouds--, ,water-,,spouts--,,atmospherical ,,phenomena4 ,under this heading we shall find the atmosphere playing a very important part4 ,the air is composed of oxygen and nitrogen with some carbonic acid gas and aqueous vapour4 ,we have1 under the ,chemistry section1 discussed these constituents which unite to make up the air or atmosphere in the following proportions3-- ,oxygen #bajj ,nitrogen #ggej ,aqueous ,vapour #adb ,carbonic ,acid #jh ------- #ajjjj ,it is a fact that all over the world the same chemical result is found4 ,whether we bottle up the air in the valley1 or1 as ,gay-,lussac did1 go up to an elevation of #ba1jjj feet in a balloon1 we shall find the air of the same chemical composition4 ,in ,europe1 ,asia1 ,africa1 and ,america1 it is all the same4 ,the pressure is less as we ascend1 and we cannot manage to breathe in very high altitudes so well as upon the ground for which we were fitted1 but the air is the same4 ,the atmosphere1 then1 is not always equal in density1 nor is it quite transparent4 ,the light from sun and stars is1 to a certain extent1 lost1 and it has been calculated that the sun's rays lose one-fifth part of their brightness passing through the atmosphere4 ,we all know what the air is4 ,we breathe it1 we feel it blowing1 we witness its effects4 ,were it not composed as it is we should die or go mad2 plants would not live1 and the earth would become a desert4 ,air is everywhere--invisible2 a so-called empty vessel is full of air because an animal will live in it till the atmosphere has become vitiated by the carbonic acid from the lungs4 ,yet air1 or rather its watery portion1 is visible when condensed4 ,vapour is not perceptible4 ,but how does it become so8 ,we cannot see the air1 how can we see a portion of it8 ,we can answer this question by illustration4 ,the steam from an engine is not visible on a very hot day4 ,but when the day is damp and dull the vapour is condensed1 and becomes visible2 then air appears and is resolved into vapour again4 ,this change was effected by heating water and then cooling it1 when it came back to water again4 ,this watery vapour is always present in the atmosphere4 ,heat1 also1 is present in the atmosphere1 and the sun is the origin of that heat4 ,illustration3 ,fig4 #gad4--;,high tide and storm on the coast of ,schleswig4 ,heat1 we know1 is the effects of the rapid motion of small particles of matter1 and is radiated from our bodies--so we feel cold2 it reaches our bodies1 and we feel warm4 ,so air is heated or cooled by the sun1 not in its absence1 except when the earth and air have been so warmed during the day that the heat is given out by them long after sunset4 ,we have read of the pressure of the atmosphere in the ,,physics section1 and that warm air is lighter than cold air1 as shown in the ascension of the ,montgolfier balloon4 ,it is this variation of temperature of the atmosphere that gives birth to one great meteorological agent--viz41 the ,,wind1 which we will now consider4 ,,winds ,,and ,,air ,,currents4 ,we can easily illustrate the cause of winds4 ,suppose we have a hot room and a cold one1 and we suddenly open the door of communication between them1 the heated air which has risen to the ceiling of one room will rush out through the upper part of the opening of the door1 and the cooler current will flow in just above the floor4 ,if we place a lighted candle in the upper and lower part of the opening we shall see the flame tending outwards from the heated room1 and in an opposite direction from the cold room4 ,in the centre of the open door there will be but slight disturbance4 ,so it is in nature4 ,the warm air ascends1 cooler air rushes in to fill the space1 and a storm or a breeze is created4 ,the balance must be restored4 ,the upper current probably moves one way1 and the lower the other way4 ,thus clouds are said to be 8coming up against the wind0 when they are moving in an upper current1 or in a different direction to that the wind is blowing just above the earth's surface4 ,the wind moves1 with varying velocity4 ,we have a gentle breeze when the motion of the air is about five or six miles an hour1 a good breeze at twenty-five miles an hour1 a high wind at thirty-five1 and a gale at fifty4 ,hurricanes travel at sixty and seventy miles an hour1 and do enormous damage4 ,near the ,equator we do not find much wind1 and this fact has caused the name of the ,region of ,calms1 or 8,the ,doldrums0 of sailors1 to be bestowed upon that portion of the globe1 but this belt of calm has no fixed position4 ,it follows the sun's course1 and is the region of greatest heat1 and1 as it were1 the centre of a concentric circle of currents4 ,the hot air rises and goes away2 air rushes in north and south1 and causes what are called the ,north-,east and ,south-,east ,trades1 or ,trade ,winds1 owing to their being so useful in commerce for ships1 or to the old meaning of the word trade1 a 8regular course40 ,the calms of the ,tropic of ,cancer are called the 8,horse ,latitudes40 ,readers of the life of ,columbus will remember how his crew were affrighted at the persistency of the wind which bore him across1 for no sail requires shifting1 nor is a sheet altered while the vessel is making way with the 8,trades40 ,were the earth covered with water1 we should find the trade-winds blowing equally over the surface1 but the varying temperature of the land diverts them4 ,the rarefaction of the air in the ,sahara causes a westerly wind to prevail1 which blows towards the land1 instead of the trade wind we might expect to find4 ,the ,,monsoons1 again1 are caused in like manner1 for the ordinary 8trade0 from the south-east is changed by the elevation of the heated air in ,central ,asia into a south-west wind1 and so in the south1 in consequence of the heated air from ,australia1 the north-west trade appears as a north-east monsoon1 but is altered to a north-west wind4 ,nearly all the year round1 therefore1 we find the two winds1 which are modifications of the 8trades10 blowing in different directions and from different quarters4 ,from ,november to ,march there is a north-east wind north of the ,equator1 and a north-west wind blows south of the ,equator4 ,from ,april to ,september a south-west wind blows at the north1 and a south-east wind at the south of the line4 ,the term monsoon signifies a 8season10 and the changes of these winds give rise to tremendous storms causing great havoc4 ,,sea and ,,land breezes are really little monsoons2 they are caused by the heat of the sun in just the same way1 but with miniature results4 ,we all know the sea-breeze which comes in as the land gets hot during the day1 for the land warms more quickly than the sea under equally existing circumstances4 ,so again1 in the evening1 the land loses its heat more quickly1 and then the cool air flows out again to take the place of the warmer sea air which is continuing to ascend4 ,the intensity and regularity varies when the degrees of heat are most different between land and sea and in tropical regions2 and the varied coast formation will of course affect the wind1 but as a rule the fact may be accepted as plainly explained1 sea-breeze in the morning1 land-breeze at night1 and amateur sailors in boats at our watering-places will do well to bear this in mind4 ,there are a great number of local winds deriving their names from their direction or influence4 ,we may mention them briefly4 ,the special terms for winds are-- ,the ,north ,wind1 or ,tramontana4 ,the ,north-,east ,wind1 or ,greco4 ,the ,east ,wind1 or ,levanter4 ,the ,south-,east ,wind1 or ,sirocco4 ,the ,south ,wind1 or ,ostro4 ,the ,south-,west ,wind1 or ,libeccio4 ,the ,west ,wind1 or ,ponente4 ,the ,north-,west ,wind1 or ,maestro-,mistral4 ,illustration3 ,fig4 #gae4--,on a lee shore4 ,the ,mistral1 or ,maestrale1 is well known at ,nice as the north wind1 while at ,toulon it is a north-east wind4 ,the other winds1 such as the ,sirocco1 which in some places is a warm1 damp wind1 in ,madeira is a hot wind1 and likewise in ,sicily1 where it is equally warm and damp like steam4 ,it has different names in various countries1 such as ,samiel in ,turkey1 and sometimes as ,fhn in ,switzerland1 where it may1 however1 be a north wind--which1 as all travellers know1 is a dry and a hazy-weather breeze1 yet sometimes moist4 ,the ,simoon is a very hot wind raising sand-storms in the deserts1 and experience has shown it to be very prejudicial to life in consequence of the fine sand and the tremendous heat it carries with it4 ,egypt is subject to another hot wind1 called the ,khamsin1 and the west coast of ,africa is subject to the ,harmattan1 a dry1 easterly wind4 ,the cold1 dry wind of the ,himalaya is known as the ,tereno4 ,in ,south ,america there is the same wind1 the ,pampero blowing east and south-east4 ,the ,euroclydon1 mentioned by ,st4 ,paul1 is the modern bora over the ,adriatic4 ,malta rejoices 7or laments7 in the ,gregale1 a north-east wind4 ,there are several other terms1 such as the ,puna of ,peru1 a very drying wind2 the ,purgas in ,labrador1 the ,tourmente in ,france1 and ,guxen in ,switzerland4 ,then we have the ,hurricane1 from 8,ouracan0 of the ,caribs2 the ,typhone1 or ,tae-fun of ,china1 so called from the dreaded god ,typhon of ,egypt2 and the ,tornado--all very violent winds1 and circling round1 causing1 so to speak1 whirlwinds1 by which trees are uprooted1 and houses destroyed4 ,the measure of the velocity of wind is performed by anemometers1 which record the velocity in feet per second1 and the amount of pressure4 ,the anemometer is a well-known apparatus1 with its four arms terminating in 8cups0 and a 8tablet0 anemometer1 which is more or less disturbed or deflected from the vertical line by each gust of wind1 and thus the score of degrees is marked by an indicator1 which is moved as the tablet is deflected4 ,we annex a table of wind pressure and velocity-- ,,pressure ,,of ,,the ,,wind4 ---------------------------------------- ------------ ,velocity4 ,pressure per ----------------- sq4 foot4 ,miles ,feet per ,rouse and ,description of wind4 per hour4 second4 ,smeaton4 ---------------------------------------- ----------- #a #adg #jjje ,very gentle4 #b #bic #jjbj #c #ddj #jjdd ,light airs4 #d #ehg #jjgi #e #gcc #jabc ,light breeze4 #aj #adfg #jdib #ae #bbjj #aajg ,brisk breeze4 #bj #bicd #aifh #be #cifg #cjge ,strong breeze4 #cj #ddja #ddbi #ce #eacd #fjbg ,high wind4 #dj #ehfh #ghgc #de #ffja #iifc ,gale4 #ej #gcce #abcjj #fj #hhjb #aggae ,heavy ,gale4 #hj #aagcf #cadij ,hurricane4 #ajj #adfgj #dibjj ,tornado4 ---------------------------------------- ----------- ,the south-west wind is more constant than any other1 and the west wind in our islands is more frequent than the east2 tables have been compiled showing the average number of days upon which the winds blow from different quarters1 but need not be quoted4 ,storms can generally be anticipated by the barometer1 which falls very quickly for 8wind40 ,the quarter whence the breeze may be expected is often indicated by the streamers of clouds1 or 8mare's tails10 across the sky2 though we must admit the opposite direction to that anticipated by casual observers may often prove the right one4 ,hurricanes and tornadoes are really whirlwinds in motion4 ,the rotatory movement of the air is from right to left in the northern hemisphere1 and from left to right in the southern--that is1 in the opposite and same directions respectively as the hands of a watch move4 ,the whirlwinds are caused by two currents of air meeting at a certain angle1 just as a whirlpool is the result of opposing currents of water4 ,illustration3 ,fig4 #gaf4--;,effects of storm at ,halligen in #ahcd4 ,the use of the wind in nature cannot be over-estimated4 ,it is frequently destructive and terrible in its effects1 but these comparatively trifling damages are as nothing when weighed against the advantages conferred upon mankind by the wind and the currents of the atmosphere4 ,the north cold is tempered by the warm south wind4 ,the pollen and the seeds of plants are borne on the wings of the wind1 and the clouds are carried over the land to 8drop fatness0 upon our fields4 ,the want of free circulation of air is very injurious4 ,witness the terrible affliction of goitre1 so prevalent in the closely shut-in valleys such as the ,rhone ,valley1 where cretinism or congenital idiotcy is distressingly prevalent4 ,,vapour ,,and ,,clouds4 ,vapour1 as we have heard1 is invisible1 and is produced by heat4 ,as the visible steam 7which is invisible as it issues from the safety valve at the actual aperture1 and nearly invisible altogether on a hot day7 is produced by combustion1 so vapour is produced by the heat of the sun's rays4 ,but there are some observations to be made respecting these rays1 which are the cause of vapour1 and therefore of cloud1 rain1 dew1 frost1 ice1 snow1 and water all over the earth2 and we must look at the circumstances closely4 ,those who have followed us through this volume will remember that at the end of ,chapter ,,viii4 we remarked upon the spectrum1 and made a few observations respecting the heat spectrum1 and the velocity of light rays1 which became too rapid to be observed1 and then they developed heat--invisible heat--produced by non-luminous waves1 which proceed from the sun as surely as visible rays or light4 ,professor ,tyndall has written very pleasantly upon this subject1 and1 with his clear leading1 any reader can study for himself4 ,we have now arrived at the conclusion that there are visible and invisible rays giving us respectively light and heat4 ,these latter are the means whereby the ice is melted1 and by which water is evaporated to vapour1 and formed into ,,clouds when it is chilled or condensed4 ,here is another link in the beautiful chain constructed by ,nature4 ,we cannot penetrate far into any portion of the system of the universe without being struck with the wondrous harmony that exists between every portion of it4 ,thus heat and light1 vapour1 cloud1 rain1 dew1 and ice are all intimately connected4 ,a cloud1 then1 is a visible body of vapour in the atmosphere1 which is supported by an invisible body of vapour4 ,it will remain thus invisible so long as the atmosphere is not saturated with moisture4 ,the air can contain a great quantity of moisture without its being rendered visible1 and so when the day is hot we see no steam from the locomotive4 ,it is absorbed into the dry atmosphere4 ,but when the day is 8damp0 we find that the air has nearly as much moisture as it can carry1 and the steam is condensed1 a portion falling in tiny drops like rain4 ,this is proved every day in cold weather when ice is found in the windows--the cold air has condensed and frozen the water breathed out from our lungs1 and snow has been known to fall in a ball-room when a cold current of air was admitted4 ,people are sometimes apt to think that if the sun were very hot1 glaciers1 and such icy masses1 would diminish2 but we think after what has been said respecting the power of the sun's rays to evaporate water1 all will see that the contrary is the fact4 ,without sun-heat we should have no cloud1 and as clouds give us rain and snow and ice and glacier1 we must come quickly to the conclusion that glaciers and snow are the direct results of the heat of the sun4 ,the 8light0 rays of the sun do not penetrate snow1 and that is why our eyes are so affected in snowy regions4 ,the poor ,jeannette sufferers a short time since were blinded by reflected light1 and dark spectacles are worn on all ,alpine expeditions4 ,the invisible rays1 as we have said1 dissolve the ice into rivers4 ,the atmosphere produces clouds by expansion of vapour1 which chills or cools it1 and it descends as rain4 ,to prove that expansion cools air is easy by experiment1 but if we have no apparatus we must make use of our mouths4 ,in the body the breath is warm1 as we can assure ourselves by opening our mouths wide and breathing upon our hands4 ,but close the mouth and blow the same breath outwards through a very small aperture4 ,it is in a slight degree compressed as it issues from the lips1 and expanding again in the atmosphere feels colder4 ,air compressed into a machine and permitted to escape will form ice4 ,illustration3 ,fig4 #gag4--;,cumulus cloud4 ,water is present in clouds which assume very fantastic and beautiful forms4 ,we know nothing more enjoyable than to sit watching the masses of cumuli on a fine afternoon4 ,the grand masses built up like the ,alps appear to be actual mountains1 and yet we know they are but vapour floating in the air1 and presently to meet with clouds of an opposite disposition1 and produce a thunderstorm with torrents of rain4 ,those who will devote a few minutes every day to the steady examination of clouds1 will not be disappointed4 ,they give us all the grandeur of terrestrial scenery4 ,mountains1 plains1 white 8fleecy seas10 upon which tiny cloudlets float1 and low upon the imaginary yet apparent horizon1 rise other clouds and mimic mountains far and farther away in never-ending distance4 ,a pretty1 light1 feathery cloud1 with curling tips and fibres1 is known as cirrus1 and exists at a very great elevation4 ,gay-,lussac went up in a balloon #bc1jjj feet1 and even at that height the cirri was far above him in space4 ,we can readily understand that at such an extreme elevation they must be very cold1 and they are supposed to consist of tiny particles of ice4 ,such clouds as these are very frequently observed at night1 as cirro-cumulus around the moon1 and a yellowish halo1 apparent to all observers1 is thought to be coloured by the icy particles of the lofty cirrus4 ,the beautiful and varied phenomena of perihelia1 etc41 are due also to the snowy or icy flakes of the cirri and cirri-cumuli1 caused by the refraction of light from the frozen particles4 ,these cirri clouds are indicative of changeable weather as 8,mares' tail0 skies1 and long wisps of cloud1 foretelling storm4 ,the cirro-cumulus is the true 8mackerel0 sky1 and is formed by the cirri falling a little and breaking off into small pieces of cumulus1 which is a summer 7day7 cloud generally1 and appears in the beautifully massive and rounded forms so familiar4 ,the stratus is1 as its name implies1 a cloudy layer formed like strata of rock4 ,it is generally observable at night and in the winter4 ,it often appears suddenly in the sky consequent upon diminished pressure or a rapid fall of temperature4 ,it is low-lying cloud sometimes1 and at night forms fogs4 ,illustration3 ,fig4 #gah4--;,cirrus cloud4 ,the cirro-stratus is perceived in long parallel lines1 and indicates rain2 when made-up rows of little curved clouds it is a certain prophet of storm1 and when viewed as haze is also indicative of rain or snow4 8,mock-suns0 and halos are often observed in the cirro-stratus4 ,the nimbus is the rain-cloud1 or condition of a cloud in which rain falls from it4 ,it is upon this rain-cloud we can perceive the rainbow1 and on no other cloud1 but otherwise only in the sky4 ,we have now seen the varieties of cloud and their common origin with fogs and mists1 which differ from them only in the elevation at which they come into existence1 according to the condition of the atmosphere4 ,the uses of clouds are many and varied4 ,their first and most apparent use seems to be the collection and distribution of rain upon the earth4 ,but besides this1 they shelter us from the too great heat of the sun1 and check the evaporation at night4 ,supposing we had no clouds we should have no rain4 ,if we had no rain the earth would dry up1 and the globe would appear as the side of the moon appears--a waterless desert4 ,the invisible vapour in the atmosphere will produce cloud1 but the moon can have no atmosphere in that sense4 ,vapour will also absorb heat1 and intercept the sun's heat rays1 acting much as clouds do in preventing radiation and great changes of temperature4#cc ,all animals and plants depend upon moisture in the atmosphere as much as upon the varying degrees of warmth4 ,a dry east wind effects us all prejudicially2 warm1 soft airs influence us again in other ways4 ,air will be found drier as a rule in continents than in islands or maritime districts1 and this will account for the clearness of the sky in continental regions4 ,fogs and mists arise when the air is what is termed saturated with moisture1 and colder than the earth or waters upon it4 ,so the celebrated and dangerous fogbanks of ,newfoundland arise from the warm water of the ,gulf ,stream1 which is higher in temperature than the air already saturated4 ,and the same effect is produced when a warm wind blows against a cold mountain2 the air is cooled1 and condenses in cloud4 ,the cooling of the breath by the exterior air is exemplified in winter when we can perceive the vapour issuing from our mouths as we speak4 ,illustration3 ,fig4 #gai4--,storm clouds4 ,,rain1 ,,snow1 ,,and ,,dew4 ,rain is produced by the condensation of vapour4 8,vesicular vapours1 or minute globules of water filled with air10 compose the clouds1 and at last these vesicles form drops1 and get heavy enough to come to the ground4 ,perhaps they are not sufficiently heavy to do so1 and then they are absorbed or resolved into vapour again before they can get so far1 because the lower strata of air are not yet saturated1 and can therefore contain more moisture4 ,on the other hand1 we may experience rain from a cloudless sky4 ,this is no very uncommon case1 and occurs in consequence of the disturbance of the upper strata when warm and cold currents come into collision and condense the vapours4 ,rain is very unequally distributed4 ,we shall find that the region of calms1 which we mentioned in a former page1 is also the zone of the greatest amount of rain4 ,the heated air rises and falls back again1 there being little or no wind to carry it away4 ,the rainy season1 therefore1 sets in when a place enters the zone of calms4 ,equatorial districts have two rainy seasons1 as they enter twice a year into the region of calms1 but most places have only a wet and dry season1 while north and south of the calm region we find rainless districts1 or zones tempered by the trade winds1 which are dry winds4 ,but if we suppose--as indeed is the case in ,south ,america--that these dry winds happen to come in contact with a cool mountain1 the moisture of the air is precipitated in rain4 ,in ,australia1 on the contrary1 we have portions of land actually burnt up for want of rain1 because the mountain chain breaks the clouds1 so to speak1 on a limited corner of the island1 while the interior is parched4 ,the winds also coming over ,india from the ,bay of ,bengal discharge clouds and rain in the ,himalayan slopes4 ,so we perceive that the situation of mountain chains have much to do with the rain-fall1 and of necessity1 therefore1 with the vegetation and fertility of the land4 ,this is another noticeable link in the great chain of ,nature4 ,illustration3 ,fig4 #gbj4--,meteorological ,observatory1 ,pic du ,midi4 ,perhaps it may now be understood why westerly and south-westerly winds bring rain upon our islands1 and why the counties such as ,westmoreland and ,cumberland and those in ,wales receive more rain than any other part of the ,united ,kingdom4 ,seathwaite1 so well known to tourists in the lake district1 has the proud position of the wettest place in these islands4 ,we find that when the westerly wind sets in it has come across the warm ,atlantic water and become laden with moisture1 which1 when chilled by the mountains1 is precipitated as rain4 ,the amount of rain that falls in the ,united ,kingdom is carefully measured by rain-gauges1 some of which are extremely simple4 ,the water is caught in a funnel-mouthed tube1 and measured in a measuring glass every four-and-twenty hours4 ,thereby we can tell the annual rainfall in any given district1 whether it be twenty inches or a hundred4 ,one inch of rain actually means one hundred tons of water falling upon one acre of land4 ,therefore1 if the annual report of rainfall 7including all moisture7 be twenty inches1 we have an aggregate of #b1jjj tons of water upon every acre of surface within the district4 ,twenty inches is a very low estimate4 ,some places have an annual rainfall of forty or fifty inches4 ,in ,cumberland we find #afe inches has been recorded6 ,if we then multiply these last figures we get the enormous quantity of #af1ejj tons of water upon every acre of land in the district in one year4 ,it is reported from ,india that in the ,khasia ,hills the average is #faj inches1 which must be the maximum rainfall in the world4 ,at other places1 in the north-west provinces1 the fall is only seven inches4 ,sometimes in tropical rains we find fifteen inches of rain in a day1 and that has been exceeded4 ,we can now judge of the enormous amount of moisture carried up by the sun and dispersed over the earth in rain1 which swells our brooks and rivers1 cleanses the air of its impurities1 supplies our springs1 carries with it into the sea lime from the rocks for the shells of marine animals1 and then leaving its salts1 is again evaporated to form clouds1 which discharge the fresh water continually upon the earth in a never-ceasing rotation4 ,,snow4 8,we all know what ,,snow is10 you will say1 perhaps4 ,well1 then1 will any ordinary young reader tell me what he knows about snow8 8,it falls from the sky in white flakes10 says one4 8,it's frozen rain10 remarks another4 8,why1 snow is snow10 says a third4 8,there's nothing like it2 it's white rain-water frozen40 ,illustration3 ,fig4 #gba4--;,crystals of snow4 ,the last answer we received is the nearest of all4 ,snow is not snow1 paradoxical as that sounds4 ,snow is ,ice6 ,flakes of snow are ice-crystals--white1 because reflecting light4 ,in the section of ,,mineralogy we mentioned crystals1 which are certain definite shapes assumed by all substances1 and we gave many examples of them4 ,just as alum crystallizes and rock crystal assumes varied and beautiful forms1 so ice crystallizes into six-rayed stars4 ,it is to ,professor ,tyndall that the world is chiefly indebted for the descriptions of snow crystals and ice flowers4 ,in his work upon 8,heat as a ,mode of ,motion10 this charming writer shows us the structure of ice flowers4 ,he describes a snow shower as a 8shower of frozen flowers40 8,when snow is produced in calm air10 he says1 8the icy particles build themselves into stellar shapes1 each star possessing six rays40 ,we annex some drawings of snow crystals1 which are1 indeed1 wonderfully made4 ,hear ,professor ,tyndall once again3-- 8,let us imagine the eye gifted with a microscopic power sufficient to enable us to see the molecules which compose those starry crystals3 to observe the solid nucleus formed and floating in the air2 to see it drawing towards it its allied atoms1 and these arranging themselves as if they moved to music1 and ended by rendering that music concrete40 ,this 8six-rayed star0 is typical of lake ice also4 ,illustration3 ,fig4 #gbb4--;,ice crystal4 ,snow sometimes reaches us in a partly melted condition2 under these circumstances it is called sleet1 and snow being much lighter than rain 7ice is lighter than water71 it descends less directly1 and represents about one-tenth the depth of the rain-fall4 ,the use of snow in warming the earth is universally acknowledged1 and as it is such a bad conductor1 a man in a snow hut will soon become unpleasantly warm4 ,illustration3 ,fig4 #gbc4--;,ice crystal4 ,ice is only water in another form1 and snow is ice2 and it is the air in the snow that gives it warming properties4 ,these are all simple facts1 which any one by observation and careful reading and study may soon ascertain for himself4 ,we have another frozen fall of water from the clouds--viz41 hail1 which may possibly be the development of sleet4 ,,hail is formed by the falling rain being frozen in its descent1 or when different currents meet in the atmosphere4 ,a hail-storm is accompanied with a rushing sound1 as if the hail-stones were striking against each other4 ,they are very destructive1 and actual hail showers occur in summer more frequently than in winter1 and a peculiarity noticeable with regard to hail is its infrequent occurrence during the night4 ,records of destructive hail storms are plentiful4 ,the hail assumes a great size1 weighing sometimes as much as two ounces1 and measuring several inches round4 ,thunder and lightning are very frequent accompaniments of hail showers4 ,,dew is moisture of the atmosphere deposited on a cool surface--another form of condensation1 in fact4 ,cold water in a tumbler will produce a 8dew0 upon the outside of the glass when carried into a warm atmosphere4 ,such is the dew upon the grass4 ,it is produced by the air depositing moisture as it becomes colder after a warm day when much vapour was absorbed4 ,warm air can hold more water than cold air1 and1 the saturation point being reached1 the excess falls as dew at the dew 7or saturation7 point4 ,we have previously remarked that one use of clouds was to prevent rapid radiation of heat which they keep below4 ,under these circumstances--viz41 when a night is cloudy--we shall find much less dew upon the grass than when a night has been quite clear1 because the heat has left the atmosphere for the higher regions1 and has then been kept down by the clouds2 but on a clear night the air has become cooled rapidly by radiation1 and having arrived at saturation point1 condensation takes place4 ,dew does not fall1 it is deposited2 and may be more or less according to circumstances1 for shelter impedes the radiation1 and some objects radiate less heat than others4 ,hence some objects will be covered with dew and others scarcely wetted4 ,when the temperature of the air is very low1--down to freezing point1--the particles of moisture become frozen1 and appear as hoar-frost upon the ground4 ,thus dew and hoar-frost are the same thing under different atmospheric conditions1 as are water and ice and vapour4 ,we have now come round again almost to whence we started4 ,we have seen the land and water1 and the parts that water1 in its various forms1 plays upon the land1 and its effects in the air as rain1 etc4 ,we have noticed the winds and air currents as well as the ocean and its currents4 ,we know what becomes of rain and how it is produced1 and how the sea works upon the shore1 and how clouds benefit us4 ,there are besides some less common phenomena which we will now proceed to examine4 ,,footnotes3 #cc ,see 8,molecular ,physics0 7,tyndall74 ,,chapter ,,xlix4 ,,physical ,,geography4 ,,meteorology 7continued74 ,,atmospheric ,,phenomena--,,thunder ,,and ,,lightning--,,aurora ,,borealis--,,the ,,rainbow--,,mock ,,suns ,,and ,,mock-,,moons--,,halos--,,fata ,,morgana--,,reflection ,,and ,,refraction--,,mirage--,,spectre ,,of ,,the ,,brocken4 ,there are a great number of interesting1 and to inhabitants of these islands uncommon1--perhaps we might say fortunately uncommon1--phenomena1 which overtake the traveller in other countries4 ,we have referred to whirlwinds and tornados1 and will now mention two phenomena connected with these storms4 ,there is the water-spout1 for instance1 and sand-pillars in the desert1 which are whirled up by these winds in spiral columns of water and sand respectively4 ,the tiny whirlwind at cross-roads1 which picks up straws and leaves1 is the common appearance of whirling or crossing currents of air4 ,illustration3 ,fig4 #gbd4--,the ,waterspout4 ,waterspouts1 when they are permitted to come near a ship at sea1 or when they break upon land1 which is seldom1 are very destructive4 ,the waterspout is begun generally by the agitation of the sea1 and the cloud above drops to meet the water1 which at last unites with it1 and then the column of whirling liquid1 tremendously disturbed at the base1 advances with the prevailing wind4 ,its course is frequently changed1 and ships within its influence would be speedily wrecked4 ,the only way to save the vessel is to fire a cannon ball through the column and break it4 ,illustration3 ,fig4 #gbe4--,thunderstorm and shower of ashes from ,vesuvius4 ,a waterspout once devastated a district in the ,hartz mountains of ,saxony4 8,a long tube of vapour descended to the earth1 and several times was drawn upward again2 but at last it reached the ground1 and travelled along at the rate of four-and-a-half miles in eight minutes1 destroying everything in its way40 ,on another occasion at ,carcassonne in #ahbf1 8a reddish column was seen descending to the ground1 and a young man was caught up by it and dashed against a rock40 ,his death was instantaneous4 ,the cause of these whirling winds is supposed to be in the action of vertical currents of air which ascend heated1 and return rapidly as cold air4 ,the 8waterspouts10 etc41 are quickly formed4 ,the tornado is a monster whirlwind like a waterspout in form1 and advances at a tremendous rate--eastward as a rule4 ,it moves in leaps and bounds1 passing over some portions of the ground and descending again4 ,the current of air is directed to the centre2 the cyclone1 as mentioned1 has a spiral or rotatory movement4 ,thunder and lightning have been1 to some extent1 described under the head of ,,electricity1 but some observations may also be introduced here1 as storms of that nature appertain to meteorology distinctly4 ,electricity is always present in the atmosphere1 and arises from evaporation and condensation as well as from plants4 ,as the air becomes moist1 the intensity of the so-called 8fluid0 increases1 and more in winter than in summer4 ,clear skies are positively electric1 and when large1 heavy clouds are perceived in process of formation in a sky up to that time clear1 a storm is almost certain to follow4 ,these 8thunder clouds10 in which a quantity of electricity exists1 attract or repel each other respectively4 ,the cloud attracts the opposite kind of electricity to that within it2 and when at last a tremendous amount has been stored up in the cloud and in the air1 or in another cloud1 the different kinds seek each other1 and lightning is the result1 accompanied by a reverberation and commotion of the air strata1 called thunder4 ,lightning most frequently darts from cloud to cloud1 but often strikes the ground1 whereon and in which are good conductors1 such as wet trees1 metals1 running water1 etc4 ,the 8electric fluid0 assumes different forms--8forked10 8sheet10 and 8globular40 ,the second is perhaps the most familiar to us1 and the third kind is the least known of all4 ,there are many well-authenticated instances on record in which lightning with the form and appearance of fireballs has entered or struck houses and ships4 8,fulgarites0 are vitreous tubes formed in sandy soils by the lightning in search of subterranean water-courses1 for running water is a great conductor of electricity4#cd ,the fire-ball form of lightning has been known to enter a school-house where a number of children were1 and to singe the garments of some1 killing others4 ,the ball passed out through a pane of glass1 in which it bored a hole1 breaking every other pane1 however1 in its transit4 ,another instance occurred in which the lightning ran about the floor of a room1 and descending the stairs1 exploded without doing any injury4 ,lightning1 like the electric current of the laboratory1 will not always set fire even to inflammable objects4 ,an electric spark can be passed through gunpowder without setting fire to it1 and lightning will often shatter the object without firing it4 ,death by lightning is instantaneous1 and in all probability quite painless2 for we may argue from analogy1 that as those who have been rendered insensible by lightning have had no remembrance of seeing the flash which strikes so instantaneously1 nor of hearing thunder after it1 it is instantaneous in its effects4 ,besides1 the natural attitude is preserved1 and the face is usually peaceful and limbs uncontorted after death by lightning4 ,there are some curious electrical phenomena1 such as ,st4 ,elmo's ,fire1 already noticed under ,,electricity2 and in some parts of ,america1 in very hot weather1 such a light is perceived to issue from trees as the fire glides through the forest4 ,many instances are on record concerning the luminosity of pointed sticks1 and even of the tails and manes of horses in certain conditions of the atmosphere1 and of the universal power of electricity and its pervading influence in nature4 ,the benefits conferred by thunderstorms in purifying the air1 and in the production of ozone and nitric acid1 are very great1 and apart from the magnificent phenomena exhibited1 are well worth our attention1 though beyond our reach4 ,illustration3 ,fig4 #gbf4--;,aurora ,borealis4 ,terrestrial magnetism1 however1 is still more puzzling in its action than is electricity1 and the study of the needle1 its destination1 inclination1 and intensity1 which are marked upon charts1 just as are the weather reports of the ,times1 is an interesting one4 ,these magnetic maps are termed the charts of ,,isoclinic and ,,isodynamic lines4 ,the declination of the magnetic needle from the true north is its deviation from that point1 and the 8inclination0 is its dip towards the horizon4 ,the line of its direction being known as the magnetic meridian1 its divergence from this line constitutes its declination4 ,there are places where it does not deviate1 and these1 in direction north and south1 are called lines of 8no variation40 ,there are also places in the equatorial regions where the needle does not 8dip40 ,the line connecting such places is termed the ,magnetic ,equator1 and north or south of this the needle dips respectively to north or south in degrees coinciding with the distance from the equator4 ,the earth1 then1 acts as a magnet1 and attracts the needle1 but the magnetic poles are not identical with the terrestrial poles4 ,the north magnetic pole was reached in #ahca by ,sir ,james ,ross1 when the dip was only one minute less than #ij1 and the south magnetic pole was very nearly reached also by him in #ahdj4 ,the magnetic equator passes between these two points4 ,illustration3 ,fig4 #gbg4--,paraselen1 or mock moons4 ,it is to magnetic atmospherical disturbance that the aurora is due4 ,these northern 7or southern7 phenomena are extremely brilliant and diversified4 ,in temperate regions the aurora does not present such grand forms as in the extreme north4 ,there the spectacle is astonishingly beautiful4 ,the sky at first clouds over1 and mist is developed4 ,humboldt has eloquently described the aurora borealis1 and the beautiful changes of light1 the constant movement1 flashes1 etc41 denoting a 8magnetic0 storm1 as electrical discharges indicate an electric storm1 although the area affected by the former is far more extensive than that of the latter1 and there is no thunder accompanying the magnetic storm1 with the production of which the electricity of the earth is unassociated4 ,to the continuous flow of this electricity the aurora is due1 and the flashes are only the electric current descending towards the earth4 ,but the true reason of the phenomena may have to be yet discovered1 for nothing absolutely certain is known as to the origin of the aurora4 ,amongst the numerous effects of refraction and reflection of light the ,,rainbow is most common and the most beautiful4 ,if we hold a chandelier 8drop0 in the sunlight1 we shall see a brilliant representation of the rainbow on the wall or on the carpet4 ,the three colours--red1 yellow1 and blue--mingle or shade away into seven--red1 orange1 green1 blue1 yellow1 indigo1 and violet4 ,these colours are all found in the rainbow4 ,illustration3 ,fig4 #gbh4--,parhelia1 or mock suns4 ,the colour of the atmosphere--the usual blue tint of the sky--arises from the blue rays of the spectrum being reflected more than the rest by the aerial particles1 and the less vapour the bluer the sky1 because the vapour gives it a whitish or misty tint4 ,at sunset and sunrise the sky is red or yellow1 like gold1 or of crimson hue4 ,this is because the sun's rays have so much farther to come to us at sunrise or sunset1 as you will readily perceive if you draw a line from the sun to the sides and then to the top of the arc of the heavens4 ,the blue rays are thus lost in space1 while red and yellow1 which travel so much faster than blue1 are transmitted to the eye1 not giving the air time to absorb them4 ,if you go under water and look at the sun it will appear very fiery indeed1 and we may likewise imagine that fiery crimson rays1 which betoken atmospherical disturbance1 very often are due to the moisture through which they are transmitted4 ,wet and storm frequently succeed a crimson sunset1 which betokens much moisture in the air4 ,the sun is similarly seen through the steam issuing from an engine1 and the colours vary according to the density of the steam in its stages of condensation4 ,illustration3 ,fig4 #gbi4--,mirage at sea4 ,vapour1 we know1 is invisible and transparent1 but when it has been condensed into rain-drops1 and the sun is shining1 if we stand with our backs to the sun we see what we call the rainbow1 because a ray of light entering the drop is reflected1 and as all rays are not of equal refrangibility1 the light1 which is composed of three simple rays1 is divided and reflected into those and the complementary colours4 ,when the sun is at the horizon1 the rainbow1 to an observer on the earth 7but not on a mountain71 will appear to be a semi-circle4 ,the higher the sun rises the lower is the centre of the rainbow4 ,so we can never see rainbows at noon in summer because the sun is too high4 ,a second rainbow is not uncommon1 the second reflection producing the colours in a different order4 ,the colours in the 8original0 range from violet to red2 in the 8copy0 they extend from red to violet4 8,rainbows0 are often visible in the spray of waterfalls and fountains4 ,,halos are frequently observed surrounding the moon1 and then we are apt to prognosticate rain4 8,the nearer the wane ,the farther the rain10 is an old couplet referring to the appearance of the moon1 and is supposed to foreshadow the weather by the size of the halo1 which is caused1 as we know1 by the existence of vesicular vapour in the atmosphere4 ,,mock ,,suns1 or parhelia1 and mock-moons1 or paraselen1 are continually observed in cold climates1 where the tiny ice particles are so abundant in the air4 ,these phenomena were recognized by the ancients1 and halos round the sun can be observed by means of darkened glasses4 ,we annex an illustration of a mock sun and moon seen on the continent of ,europe4 ,readers of ,mr4 ,whymper's 8,scrambles in the ,alps0 will remember the gorgeous1 and to the guides mysterious1 fog-bow or sun-bow seen as the survivors of the first and most fatal ascent of the ,matterhorn in #ahfe were tremblingly pursuing their descent over the upper rocks of that mountain4 ,the ,,mirage1 or ,fata ,morgana1 is a very curious but sufficiently common phenomena1 and in the ,asiatic and ,african plains it is frequently observed4 ,when the weather is calm and the ground hot1 the ,egyptian landscape appears like a lake1 and the houses look like islands in the midst of a widely-spreading expanse of water4 ,this causes the mirage1 which is the result of evaporation1 while the different temperatures of the air strata cause an unequal reflection and refraction of light1 which give rise to the mirage4 ,travellers are frequently deceived1 but the camels will not quicken their usual pace until they scent water4 ,the ,fata ,morgana and the inverted images of ships seen at sea are not uncommon on ,european coasts4 ,between ,sicily and ,italy this effect is seen in the ,sea of ,reggio with fine effect4 ,palaces1 towers1 fertile plains1 with cattle grazing on them1 are seen1 with many other terrestrial objects1 upon the sea--the palaces of the ,fairy ,morgana4 ,the inverted images of ships are frequently perceived as shown in the illustration 7fig4 #gbi71 and many most extraordinary but perfectly authentic tales have been related concerning the reflection and refraction of persons and objects in the sky and on land1 when no human beings nor any of the actual objects were within the range of vision4 ,it will be well to explain this phenomenon1 and the diagrams will materially assist us in so doing1 for the appearances are certainly startling when realized for the first time4 ,the ,spectre of the ,brocken we see mimics our movements1 and we can understand it4 ,but when apparently solid buildings appear where no buildings have been erected1--when we see--as has been perceived--soldiers riding across a mountain by a path1 or ledge1 perfectly inaccessible to human beings even on foot1 we hesitate1 and think there is something uncanny in the sight4 ,let us now endeavour to explain the mirage4 ,suppose that in the annexed diagram the space enclosed between the letters ,a1 ,b1 ,c1 ,d1 be a glass vessel full of water4 ,the ship is below the horizon1 the eye being situated at ,e--the glass vessel of course representing the atmosphere charged with moisture4 ,the eye at ,e will perceive the top of the mast of the ship1 ,s1 and we may imagine a line drawn from ,e to ,s4 ,then put a 7short focus7 convex lens at a just above this 7imaginary7 line1 and a concave one1 b1 just over it4 ,through the former an inverted ship will be seen1 and an erect one through the latter at ,s and ,s respectively4 ,we now have the effect in the air just as reproduced in nature by the difference in temperature in air strata1 which cause it to act like a concave lens when the density of the water diminishes towards the centre1 and like a convex lens when it is increased4 ,illustration3 ,fig4 #gcj4--;,explanation of ,mirage4 ,this can be proved by heating the air 7by hot irons7 above the glass vessel filled with oil1 and the effects will be just the same as through the lenses4 ,dr4 ,wollaston obtained the mirage by using a clear syrup1--about one-third of the vessel full1--and filling it with water4 ,the gradual mingling of these fluids will produce the phenomenon4 ,the illustration in the margin 7fig4 #gca7 shows us the rays proceeding from the ship's hull1 and refracted into the line reaching the eye1 above the line proceeding from the mast1 so the ship appears hull uppermost2 the rays cross at x4 ,but if they did not cross before they reach the eye1 the image would appear as at s p in an erect position4 ,illustration3 ,fig4 #gca4--,the ,mirage4 ,the ,spectre of the ,brocken arises from a different cause4 ,such appearances are only shadows1--projected on thin clouds or dense vapours at sunrise1 or when the sun's rays are directed horizontally1--for of course vertical rays will throw the shadow on the ground on to the zenith4 ,balloons are also reflected thus1 and much interest has been caused by the appearance of a twin balloon1 until the aerial voyagers have discovered the cheat by seeing the shadowy aeronaut imitating their actions1 and the second balloon has been discovered to be an airy nothing4 ,,footnotes3 #cd 8,fulgarites0 are composed of melted quartz1 and on ,mount ,ararat many have been found which give a character to the formation of the lesser ,ararat4 ,,chapter ,l4 ,,physical ,,geography4 ,,climatology4 ,,weather1 ,,climate1 ,,and ,,temperature--,,isothermal ,,lines--,,isobars1 ,,weather ,,forecasts1 ,,and ,,signs ,,of ,,the ,,sky4 ,it is usually considered a sign of a paucity of ideas when one begins a conversation about the 8weather10 but there can be no doubt that there is no more interesting question in social life at certain times as to whether it will or will not rain4 ,our outdoor amusements are all dependent upon weather1 and a little cloud may throw a deep shadow over all our pleasure if we neglect to bring out an umbrella1 or to carry a waterproof4 ,we are never independent of what we term the 8capricious0 climate1 but in reality the laws of 8the ,weather10 though so imperfectly understood1 are fixed and invariable1 and if we could read the signs in the sky and learn the condition of the atmosphere1 we might leave the 8prayers for rain0 and 8for fine weather0 out of the ,church service1 for then we should understand that unless miracles are performed for us the laws of ,nature can in no wise be altered4 ,of late years weather forecasts 7not prophecies7 have come before us in our newspapers after the manner instituted by the late ,admiral ,fitzroy1 whose name has become a household word in ,england4 ,but at the commencement of the ,christian era and before that time the signs of the heavens and the behaviour of animals and birds were noted with reference to changes of weather4 ,if we read ,virgil we shall find numerous references to these portents1 and the translation usually quoted will furnish us with information which must be as true nowadays as it was in ,virgil's time1 for wild animals do not change their habits4 ,speaking of wet weather in the ,georgics the poet wrote3-- 8,the wary crane foresees it first1 and sails ,above the storm1 and leaves the hollow vales2 ,the cow looks up1 and from afar can find ,the change of heaven1 and sniffs it in the wind2 ,the swallow skims the river's watery face1 ,the frogs renew the croaks of their loquacious race2 ,the careful ant her secret cell forsakes1 ,and draws her eggs along the narrow tracks2 ,huge flocks of rising rooks forsake their food1 ,and1 crying1 seek the shelter of the wood4 99 99 99 99 99 ,the owls1 that mark the setting sun1 declare ,a starlight evening and a morning fair40 ,we might quote further selections respecting the signs in the heaven and earth mentioned1 but the foregoing verses will be sufficient to illustrate our position1 and to show us that weather forecasting is1 at any rate1 as old as the ,christian era4 ,the moon is generally supposed to influence the weather--a 8,saturday's ,moon0 being particularly objectionable1 or when she appears anew at some hours after midnight thus-- 8,when first the moon appears1 if then she shrouds ,her silver crescent1 tipped with sable clouds1 ,conclude she bodes a tempest on the main1 ,and brews for fields impetuous floods of rain40 ,illustration3 ,fig4 #gcb4--;,in the northern ,seas4 ,weather permitting1 we can go out and study the clouds as described in the foregoing chapters1 or consult the barometer1 and see which way the wind blows4 ,the child will tell us that a high 8glass0 means fine weather1 and a low barometer indicates rain1 but this is only relatively true4 ,a high glass may be falling1 a low glass may be rising4 ,a sudden fall or a sudden rise are indicative of bad1 windy weather1 or a short-lived fine period4 ,the glass may rise with a northerly wind1 and rain will supervene1 so careful observation is necessary before one can obtain even a superficial knowledge of the weather4 7,see subsequent observations on 8,weather407 ,the ,americans telegraph the results of their observations of coming storms across the ,continent1 corrected by the signs noticed and recorded by vessels arriving in ,new ,york4 ,thus they are frequently very accurate2 steady application and observation at ,sandy ,hook must give them a great deal of useful information for the 8forecasts40 ,the word ,,climate is derived from the ,greek klima1 a slope2 and thus at a glance we perceive how the aspect it presents to the rays of the sun in the earth's revolutions1 must affect the 8climate0 of a country4 ,of course the position of any portion1 the elevation and locality of the mountains1 have also a share with the soil1 winds1 rains1 and sea-board1 in determining the climate of any region4 ,many points have already been touched upon in former chapters4 ,temperature1 moisture1 and vegetation are the chief natural features which determine climate1 and we must find out the position of the land with reference to the sun first1 to ascertain the climate4 ,the more vertical the sun is the hotter the atmosphere1 for the rays strike directly upon the earth1 which radiates the warmth received4 ,these heat rays are1 as we know1 invisible4 ,the hottest portion of the earth must be at the equator for the sun is overhead1 and the rays beat down directly upon the earth4 ,the sun is also nearer than when at the horizon1 and less rays are absorbed by the atmosphere4 ,the longer the day the greater the heat4 ,illustration3 ,fig4 #gcc4--;,in the southern steppes4 ,temperature is registered by observation of the thermometer1 and the distribution of heat is represented upon a chart across which lines are drawn at places of equal temperature4 ,these lines are called 8isothermal40 ,there are also terms to denote equal winter temperature and the average summer heat--isochimines and isotheres respectively4 ,temperature decreases as we ascend from1 and increases as we descend into1 the earth4 ,this fact proves that the air is not warmed by the sun's heat1 but by radiation from the ground4 ,as we ascend we reach the line of perpetual snow1 which varies in different parts of the globe4 ,in the tropics it extends from #ae1jjj to #ah1jjj feet2 but it varies even in places of the same latitude1 according as the towns are inland or on the coast1 as in the ,pyrenees and ,caucasus1 where there is a difference of three thousand feet in the snow limit4 ,the line of the snow limit1 as a rule1 gets lower as we journey from the equator to the poles4 ,exception will be found in the ,himlaya1 where the snow line is higher on the northern side1 in consequence of the existence of the ,thibetan tableland1 which causes a higher temperature than that existing upon the abrupt southern slope4 ,countries1 therefore1 though in the same latitude1 may have different climates according to the elevation of the land4 ,the proximity to the sea is another reason for climatic difference4 ,water takes some time to become warm1 but when it has once become so it will not readily part with its heat4 ,the ,gulf ,stream1 with its warm current beating along our shores1 gives us a high temperature and a moist climate--a very different condition to ,newfoundland or ,nova ,scotia1 which are in much the same latitude as ,england and ,ireland4 ,by the sea the climate is more uniform1 and the extremes of heat and cold are not so distant4 ,we send invalids to the seaside to save them the effects of such violent changes4 ,winters are milder and summers cooler by the sea4 ,we can readily understand how such circumstances affect the vegetation1 and places which in winter may enjoy a mild and genial climate 7comparatively speaking71 may have a cold summer4 ,ferns may flourish in winter out of doors1 but wheat will not ripen in the autumn owing to the want of heat4 ,the winds also1 and the soil and aspect of a region1 all have a share in determining its climate4 ,trees bring rain by evaporation1 and a wooded country is a blessing to its inhabitants1 defending their habitations from wind and avalanches in mountainous districts4 ,but the climatic conditions are altering4 ,the ground is being more and more cleared2 the soil is more cultivated1 and moisture is being more eliminated from it4 ,therefore the air becomes warmer by the radiation of the ground1 and clouds are formed which keep the warm layers down nearer the earth4 ,mountains1 as we have seen1 affect the rain-fall in districts2 and in ,scandinavia--in ,norway chiefly--the average rain-fall is very high4 ,the sheltering effects of mountains from east or northerly winds also alter the climate1 while clay or gravel soils are cold or warm inasmuch as they absorb1 or evaporate1 moisture4 ,some surfaces being different from others give out more heat4 ,in some mountainous districts we shall find every variety of climate from the sea-level tropical heat to the rigours of the pole4 ,the greatest average temperature is north of the equator in ,africa2 the lowest in the north1 to the west of ,greenland4 ,masses of land act in a different manner to the oceans1 and the former become heated and cooled with equal rapidity1 while the sea1 as already mentioned1 is slow to lose its heat4 ,our land enjoys a mild and equable climate as a rule1 because it is surrounded by water1 and the ,gulf ,stream warms it4 ,the ,european climate1 taken altogether1 may be considered the best on the globe4 ,we will now pass on to a few observations concerning the weather1 and the means of determining it beforehand4 ,it is always a dangerous thing to act the part of a prophet1 and the uncertainty attending an uninspired foreteller's predictions must in time disparage him in the estimation of his hearers and disciples4 ,but there are signs in the sky which we can discern and render valuable by the aid of instruments4 ,we must have a reliable barometer and thermometer1 and keep a record of the average conditions of the weather1 if we wish to wear the mantle of the weather-prophet--a term now1 in ,america1 applied 7jokingly1 no doubt7 to people who are not particular in their statements of facts4 ,but without entering upon any scientific discussion1 we may state a few plain rules which can be observed1 besides the indications of a rising or falling barometer4 ,having frequently studied the aspects of the clouds1 with the assistance of the hints from the wind-currents1 we can fairly prognosticate or suggest probable changes of weather4 ,illustration3 ,fig4 #gcd4--,weather chart4 ,we have already remarked upon the colours of the sunset1 which are attributable to the vapours in the atmosphere1 and we say a red sky foretells fine weather2 a yellow sky changing into green means rain1 or rain and wind2 on the other hand1 when the red rays appear we may anticipate fine weather1 as the atmosphere is becoming less and less moist4 ,a 8low0 dawn is known as a good sign2 so when the first rays appear at1 or near the horizon1 we may anticipate a fine day1 as we may when the morning is grey4 8,evening red and morning grey0 are almost unfailing tokens of fine weather4 ,very often a yellow sunset means wind2 a wild1 crimson sky means a gale4 ,on the afternoon 7,saturday7 before the ,eurydice foundered off the ,isle of ,wight1 we particularly noted the sunset at ,gravesend2 and it was evident 7in our estimation7 that a sudden storm was imminent1 and we remarked it to our companions4 ,the sudden fall of the barometer1 and the appearance of the rising clouds early on that sad ,sunday afternoon1 approaching in dark masses from the west and north-west1 spoke of rain and 7possibly7 snow4 ,how true the forecast was the event proved4 ,when clouds are soft and thin we expect fine weather2 when they are dark and hard1 rain and wind4 ,a ragged-edged and heavy cloud indicates thunder and lightning1 with squalls when we see dark clouds flying rapidly across the mass of cumuli4 ,a 8mackerel0 sky and 8mares' tails0 generally foretell wind1 the direction and the upper currents being noted4 ,the longer the warning given by the heavens1 the longer the bad 7or fine7 weather will last2 and the converse is also true4 8,evening grey and morning red1 ,put on your hat1 you'll wet your head40 ,the cirrus is a wispy cloud1 and is often observed extending across the sky on a fine afternoon4 ,this may or may not indicate rain2 it generally points to wind4 ,if its direction be northerly and west to southerly and east1 it is a good sign1 but from west to east it is a bad sign4 ,the habits of birds and animals1 and their anxiety for shelter1 8pigs running with pieces of straw in their mouths10 and the low-flying swallow1 are all signs of approaching rain and bad weather1 and the scintillation of stars betokens moisture in the atmosphere4 ,these are well-known appearances1 but there are others regarding the winds and currents of air which require the assistance of ,admiral ,fitzroy's book4 ,for instance1 a falling barometer with rising temperature means southerly winds and rain2 in winter1 with low temperature1 snow4 ,but a rising barometer with northerly wind often means rain4 ,a rising glass after a low fall may1 and often does1 indicate more wind from the north1 and after that fine weather1 if lower temperature also supervene4 ,if warm weather continue under the circumstances1 the wind may back and blow from the southward4 8,the most dangerous shifts of wind happen soon after the barometer rises from a very low point1 or if the wind veers gradually shortly after with a rising barometer40 ,if the barometer rises with a southerly wind fine weather may be expected1 and if it falls with a northerly wind rain1 hail1 and snow are imminent1 for the rule is a fall for southerly1 and a rise for northerly winds4 ,a sudden fall with west wind indicates storm from northerly quarters 7,n4,e4 to ,n4,w474 ,an east gale veering southwards with falling glass indicates a change of storm-direction to a point from ,n4,w4 or ,n4,e41 suddenly and violently1 though a change might have been expected from the appearance of the glass4 ,a calm frequently occurs between these disturbances4 ,a backing wind--that is1 a wind going in a direction opposed to the sun's course 7and with the earth7--is a bad sign after unsettled weather4 ,the wind is said to 8veer0 when it goes with the sun4 ,the south-east wind1 with clear sky1 warm weather1 and low clouds on the horizon1 is a sign of wet4 ,a dry east wind means fine weather4 ,heavy clouds in the north-west generally bring a thunderstorm4 ,when really distant objects look very near rain must be expected4 ,there are many exceptions to weather rules1 and none can be laid down as invariable4 ,the ever-changing currents of air1 and varying moisture of the atmosphere1 give rise to barometric changes1 which should be carefully noted4 ,a little experience and close observation for one year1 with notes of signs1 and indications of temperature1 will assist any one to tell the probable change that is approaching4 ,there are a great number of signs of weather which are observable in the animal and even in the vegetable kingdom1 as well as in the moon and stars4 ,many flowers close their petals before rain comes on1 and the behaviour of domestic animals often foretells storm4 ,sheep huddling together in a corner tell us the direction from which the tempest is approaching2 sea birds fly to shore1 and land birds become restless4 ,the naturalist will observe the domestic animals which become uncomfortable and sniff the air2 the cat lies with her head down1 the brain lowest2 and frequently washes her face1 or scampers about aimlessly4 ,spiders disappear1 and worms come up to seek the expected water4 ,when fine weather is coming all nature appears glad1 but leeches sink into the water as far as they can4 ,the above are some of the domestic and common signs of coming rain1 and conversely for fine weather4 ,a wailing wind1 a cloudy mountain1 a greenish rainbow or too red a one1 a pale moon with indistinct points1 or a halo round it1 are all signs of rain and possibly wind4 ,so the most superficial observer may with these few suggestions inform himself of the chances of fine or wet weather4 ,,chapter ,,li4 ,,biology4 ,,part ,i4 ,,botany4 ,,plants ,,and ,,animals--,,structure ,,of ,,plants--,,flowering ,,plants--,,the ,,stem--,,the ,,leaves--,,forms ,,of ,,leaves4 ,,biology is derived from the ,greek word ,bios1 8life10 and logein1 8to speak10 and constitutes the science of ,,organic ,,life4 ,this science is divided into two branches3 ,,botany1 relating to the life of plants2 ,,zoology1 to the animals4 ,plants1 then1 are living things1 and as we proceed we shall find them born1 or 8germinating10 growing up as young plants1 maturing as adults1 and finally dying1 and their particles resolving into their elements4 ,there is more than one application of the text1 8,man is but as a flower of the field40 ,in the ,,geological section we noticed the progressive stages of the vegetable creation1 and if we turn back to those pages wherein the various epochs of the earth's formation are enumerated1 we shall see how plant-life developed4 ,thus we find in the ,cambrian the first traces of vegetable life in the weeds of primeval seas4 ,the ,silurian strata and the ,devonian furnish us with many fossils of marine alg1 and if we examine the succeeding periods we shall find a progressive increase and development2 pines and tree-ferns in the sandstone1 and most of the plants 7by which term we include all varieties7 were different from those at present existing in the earth4 ,illustration3 ,fig4 #gce4--;,branch of the oak4 ,we spoke of climate lately1 and referred to the vegetation having an influence upon it4 ,the same is true of the effect of climate upon vegetation4 ,the conditions of plant-life depend upon climate1 as it partly depends upon plant-life4 ,but of all the necessary conditions the first created thing is the most necessary--light4 ,without light the plant is nothing4 ,plants have many points of similarity with animals4 ,they live1 they possess organs1 their compositions contain similar substances1 such as carbon and albumen1 and close chemical analyses have found the existence of the elements oxygen1 nitrogen1 hydrogen1 and carbon in animals and plants4 ,therefore water must play a conspicuous part in all4 ,professor ,huxley puts this question in his usual clear fashion4 ,he says3-- ,illustration3 ,fig4 #gcf4--,the pine4 8,it is a very remarkable fact that not only are such substances as albumen1 gluten1 fibrin1 and syntonin known exclusively as products of animal and vegetable bodies1 but that every animal and every plant at all periods of its existence contains one or other of them1 though in other respects the composition of living bodies may vary indefinitely4 ,thus some plants contain neither starch nor cellulose1 though these substances are found in some animals2 while many animals contain no horny matter and no gelatine-yielding substance4 ,so that the matter which appears to be the essential foundation of both the animal and the plant1 is the proteid united with water1 though it is probable that in all animals and plants these are associated with more or less fatty and amyloid 7starchy and saccharine7 substances1 and with very small quantities of certain mineral bodies1 of which the most important appear to be phosphorus1 iron1 lime1 and potash4 ,thus there is a substance composed of water1 plus proteids1 plus fat1 plus amyloids1 plus mineral matters1 which are found in all animals and plants4 ,when these are alive this substance is termed ,,protoplasm40 ,illustration3 ,fig4 #gcg4--,the fir4 ,we have taken the liberty to extract the above paragraph1 as it expresses in a few words1 and very clearly1 the common origin of plants and animals4 ,we will now consider the conditions of plant life4 ,heat1 light1 and moisture are the principal necessaries1 with of course air and certain earthy matter4 ,some plants1 like some few animals1 live in darkness1 such as truffles and fungi1 as do cave-fish and bats4 ,but this is the exception1 and the sense in which plants 7or animals7 can exist without light is a very restricted one1 and only to be sustained at the expense of the plant material1 which must originally have been derived by the action of light4 ,light1 therefore1 is the great 8producer40 ,it gives life to plants upon which animals feed1 and therefore light is in one sense the beginning of all things4 ,we can now understand why light must have been created first4 ,many interesting experiments can be made to observe the effect of darkness and different coloured light 7transmitted through coloured glasses7 upon plants2 and it will be observed that although the leaves may not develop the natural green tint1 the flowers will exhibit their usual colour4 ,one effect of light upon plants is to make them green4 ,we all admire the beautiful green of the spring leaves1 and the freshness of the colours of the trees and grass4 ,but if we pluck up a plant its root is not green4 ,why then is the cleaned root not as green as the upper portion8--,because of the absence of light4 ,there is a substance called ,chlorophyl which1 when acted upon by light1 becomes green4 ,this is contained in plants1 and when the daylight falls upon it the substance turns green4 ,so1 as we said above1 plants are not green when kept in the dark4 ,celery is a common instance4 ,heat1 of course1 has much to do with the activity or vitality of plants1 and the range extends from just above freezing point to #abb ,fahr4 ,we find tiny plants blossoming in ,alpine regions close to the snow1 and others in full life in the tropics1 protected from the fierce rays by scaly coverings and huge leaves4 ,in the northern regions buds appear as soon as the surface warmth is felt1 and even when no heat can yet penetrate to the roots4 ,thus we see that ,nature fits the animal and the plant to the localities in which they live1 and they exist interdependently4 ,some can defy cold1 others flourish in drought2 some love moisture1 others live in great heat encased in prickly armour4 ,illustration3 ,fig4 #gch4--;,branch of elm4 ,with this introduction to biology we may now pass on to speak of the seeds and germination of plants1 which we divide into the flowering and non-flowering species4 ,we suppose that the appearance of various organs of plants are familiar to our readers1 and the root1 the stem1 the leaves1 and the flower itself1 as well as the seeds1 are well known1 and their uses understood generally4 ,now if we compare a mineral--say a crystal of quartz--with a plant1 we find the crystal uniform1 consisting of small particles of quartz throughout1 and it appears an aggregation from outside of these particles in a particular form4 ,it cannot grow from within4 ,but a plant can2 and it is very different in structure and appearance4 ,it receives nourishment from outside also1 but it assimilates the materials1 which are not the same as those we meet with in the plant itself4 ,the mineral1 on the contrary1 is essentially the same throughout2 it can only grow by aggregation of atoms like itself4 ,a plant1 therefore1 like an animal1 must have organs within it1 and must be capable of change in itself2 it has powers of reproduction1 and in some few instances of locomotion2 it can eat flies1 and assimilate them as an animal does4 ,a plant1 therefore1 is an organized body without external voluntary movement2 and hereby it is essentially distinct from an animal1 with which1 in organization1 it is closely connected4 ,the simplest form of the animal as of the plant1 is that of a minute vesicle or cell1 containing a fluid in which are some granular substances4 ,at this stage it could not be distinguished from the simplest plant1 if it had not the faculty of voluntary movement--the power of changing its place4 ,the animal has a locomotive power4 ,sometimes1 indeed1 it is a very limited sphere to which it is confined2 yet it may change its place for another more conducive to the exigencies of its being4 ,it is sufficient for the present to have given the most general characteristics by which plants are distinguished from the other objects that1 with them1 compose the great kingdom of ,nature4 ,a precise and clear apprehension of their varied forms and wonderful phenomena can only be obtained by a careful analysis of the nature and structure of the subjects of the vegetable kingdom4 ,the cell is the fundamental or elementary organ of plants1 and the knowledge of its metamorphoses and functions constitutes the foundation of botany4 ,we must therefore first consider the simple organs of plants4 ,,structure ,,of ,,plants4 ,it will be necessary for the reader to gain some little knowledge of the tissues and cells of plants before he proceeds to examine the organs of development1 and a microscopic examination will soon disclose the few simple tissues which are termed cells and vessels4 ,these exist in all plants of whatever nature4 ,plants are aggregations of cells1 8every one of which has its little particle of protoplasm enclosed by a casing of the substance called cellulose1 a non-nitrogenous substance nearly allied in chemical composition to starch40#ce ,the tissues are 8cellular0 and 8vascular0 respectively4 ,the cells have an outer sac or covering which is transparent1 and this cover is the cellulose above mentioned4 ,it contains 7#a7 the protoplasm1 a kind of jelly-like substance 7which holds the proteine or basis of life72 7#b7 water or cell-sap2 7#c7 the nucleus2 and 7#d7 chlorophyl4 ,this protoplasm is apparent in both plants and animals4 ,the cells containing these various substances--in which we find oxygen1 hydrogen1 nitrogen1 sulphur1 and carbon1 with phosphorus perhaps--are divided to form new cells1 and so on with most astonishing rapidity1 amounting in some instances to millions in a day1 and a case of this nature will readily be recognized in the mushroom4 ,illustration3 ,a ,b ,c ,fig4 #gci4--,plant cells4 ,cellular tissue is composed of these cells1 and vascular tissue is composed of vessels or tubes like coiled springs1 which are cells without divisions or partitions4 ,these tissues will be referred to farther on as dotted ducts or tubes4 ,illustration3 ,fig4 #gdj--;,form of cells4 ,in most of the spongy parts of plants1 as in the pulp of fruits and pith of elder1 the cells preserve the globular or oval shape represented in fig4 #gci ,a4 ,but the cells1 in consequence of that mutual pressure1 more frequently assume the form of a polygon 7fig4 #gci ,b71 the section of which is generally hexagonal4 ,the cellular tissue may generally be compared to the bubbles produced by blowing through a straw or tobacco-pipe into soap and water2 or it may be illustrated by placing balls of moist clay together1 and then pressing them more or less strongly4 ,in this manner every individual ball assumes a polygonal shape corresponding to the form of the cells represented in fig4 #gci ,c1 and which disposition is1 in many plants1 preserved with the utmost regularity4 ,such cells as are1 with tolerable equality1 extended in all directions1 are named parenchyma1 and of these are composed the tuberous parts of plants1 as the potato1 dahlia-roots1 etc41 and especially the soft1 spongy parts of the pith1 bark1 leaves1 etc4 ,we frequently1 however1 meet with cells which are extended longitudinally1 and pointed at both extremities1 as in fig4 #gdj4 ,the sections of these cells1 which are compactly arranged1 have the appearance of a hexagon4 ,they are termed woody cells1 or woody tissue 7prosenchyma71 and constitute the chief portions of the more solid parts of plants1 as the ligneous parts of trees1 shrubs1 etc4 ,very long1 flexible cells1 as those which constitute the fibres of flax and hemp1 are called bast-cells1 and appear under the microscope as round threads of uniform thickness1 whereas the fibres of cotton wool1 which rarely exceed one or two inches in length1 when magnified1 present the appearance of flattish bands with somewhat rounded margins4 ,by these marks1 the union of flax and cotton in the same web or piece of cloth may be detected4 ,occasionally the cells assume very abnormal shapes1 as the stellate or star-formed cells4 ,these are described as irregular cells4 ,as every plant1 whether small or great1 is only an aggregate of a great number of cells1 so1 also1 the life of a plant is nothing else but the sum of the activities of all the cells of which it is composed4 ,the special province of the cells is to receive from the soil or atmosphere the water necessary for the various vegetative purposes1 together with the nutritious materials dissolved in the watery and aerial fluids1 and to circulate them through the whole body of the plant4 ,the circulation within a plant is not carried on through the agency of tubular channels1 but only by the passage of sap in all directions from one cell to another4 ,illustration3 ,fig4 #gda4--,vascular tissue4 ,since the cells have no openings1 it is somewhat difficult to understand in what manner the fluid can enter into the plant from without1 and by what means it can inwardly pass from cell to cell4 ,this phenomenon1 however1 is dependent on the peculiar quality both of vegetable and animal membranes and fibres--viz41 that they are permeable by many fluids1 without being dissolved by them4 ,experiments show that this permeative action is carried on in accordance with definite laws4 ,when two fluids of unequal densities--as1 for example1 an aqueous solution of sugar and mere water--are separated from each other by a diaphragm of pig's bladder1 we perceive a constant tendency on both sides to restore the equilibrium in the density of the two fluids4 ,a portion of the water penetrates the bladder1 mixing with the solution1 and a portion of the latter finds its way to the former by the same medium4 ,in this experiment one important fact is to be observed--viz41 that the lighter fluid always passes through the separating medium more rapidly to the denser than vice vers2 consequently1 in this experiment more of the water passes through the bladder to the saccharine solution than of the latter to the water4 ,this permeative capability of the tissue of vegetables and animals is called endosmose4 ,the cells both circulate the sap and alter its condition1 so we find differing substances in the same plant4 ,the cell as described creates new cells1 and the force with which the sap rises is rather greater than the pressure of the atmosphere4 ,the vascular1 or fibrous tissues1 are illustrated in the margin 7fig4 #gda74 ,they usually contain air4 ,some plants have no vascular tissue1 and are termed cellular plants--such as mushrooms1 fungi1 mosses1 and seaweeds4 ,many contain both tissues1 and these are the more highly developed kinds4 ,illustration3 ,fig4 #gdb4--;,cells of epidermis 7leaf74 ,sometimes we find a milky juice in plants4 ,this is called latex2 and caoutchouc is always present in it4 ,this juice is contained in tiny tubular vessels1 which have their origin in the new cellular tissue of the lactiferous plants4 ,the tissue of the cuticle1 or epidermis1 which externally covers all parts of the plant while they remain green1 is of a peculiar nature1 and demands special consideration4 ,it is formed of flat tubular cells1 very much compressed1 and in close contact1 with the exception of some parts where the stomata1 or mouths1 are placed4 ,in fig4 #gdb a section of the leaf is represented1 the large transparent empty cells of the epidermis1 and above these the parenchymatous cells of the leaf filled with greenish-coloured granules4 ,in four places 7fig4 #gdc7 stomata 7s s s s7 are seen1 which have their openings surrounded by parenchymatous cells disposed in semilunar forms4 ,under each stoma 7mouth7 there is a hollow space which is connected with the intercellular passages of the leaf4 ,these stomata1 represented in fig4 #gdc1 are so numerous on the under side of the leaf1 that hundreds have been counted in the space of a square line4 ,through these minute organs an intimate connection exists between the interior of the plant and the external air4 ,illustration3 ,fig4 #gdc4--,stomata4 ,the epidermal cells not unfrequently exhibit very abnormal formations4 ,when much extended in length they appear as hairs which are frequently branched1 and in many plants they contain an irritating sap 7in the nettle1 for example74 ,bristles1 prickles1 glands1 warts1 and especially the substance which forms the well-known cork1 are all due to the metamorphosis of this exterior integument4 ,,flowering ,,plants4 ,illustration3 ,fig4 #gdd4--,water lily4 ,illustration3 ,fig4 #gde4--,transformation of petals into stamens in white water lily4 ,flowering plants have certain distinct features which cannot be mistaken1 for they grow well above ground1 and can easily be examined4 ,there are a hundred-thousand different species of flowering plants1 and a visitor to ,kew can study them there4 ,any child can tell a flower when he sees it1 but a flowering plant is no more restricted in ,,botany to actual bright blossoming plants1 than the term rock in ,,geology means a mass of stone only4 ,flowering plants may be either very gorgeous or very simple2 and so long as they contain a reproductive apparatus they are flowering plants4 ,the rose is a flowering plant1 but the oak is equally one4 ,the beech tree and the primrose are classed under the same heading4 ,flowering plants must possess stamens and pistils1 which bring forth seeds which contain an embryo1 and the germination of seeds can be easily perceived by any one who will take the trouble to soak them 7say 8scarlet runners07 in warm water1 and keep them warm in moist flannel4 ,the process may then be examined at leisure4 ,we need hardly insist1 after what we have said1 upon the necessity for some air and light1 or remind the reader that he must not keep the seeds in a close1 dark place1 though light is not so necessary at first as air4 ,the embryo connects the 8cotyledons0 or halves of the seed1 and this develops into a tiny rootlet or 8radicle10 and upwards into the stem1 the commencement of which is known in botany as a 8plumule40 ,the rootlet seeks nourishment from the ground4 ,the albumen secreted in the cotyledons feeds the embryo1 until 7in some cases7 it is exhausted and they die away4 ,in other cases they grow up and obtain food for the young plant in the air4 ,some plants have 7like wheat7 only one seed-leaf1 or cotyledon2 and these kinds are called monocotyledons1 or endogens1 in which the growth is upright4 ,the others are called dicotyledons1 or exogens4 ,so far now1 perhaps1 you may understand that the outer covering of the seed is called the testa2 the opening which may be perceived in the ordinary bean near the dark spot is the micropyle1 or little gate2 that the halves of the covering are termed cotyledons1 or cups1 and that the embryo sprouts upwards and downwards1 the upper part of the stem being the plumule1 and the lower portion the radicle4 ,even if the seed be put micropyle upwards into the ground1 or between layers of flannel1 to germinate1 you will find that the radicle will always curve downwards4 ,illustration3 ,fig4 #gdf4--,pistils of violet4 ,illustration3 ,fig4 #gdg4--,tetradynamous stamens4 ,illustration3 ,fig4 #gdh4--,polyadelphous stamens4 ,illustration3 ,fig4 #gdi4--,pistil of primrose4 ,illustration3 ,fig4 #gej4--;,diadelphous stamens4 ,illustration3 ,fig4 #gea4--;,fibrous root4 ,the root then being displayed1 it pushes its way into the ground to seek for nourishment1 and when the proper moisture has been admitted to the seedling1 which has been reposing in the cotyledons all the time1 it sprouts up rapidly4 ,the root and its fibrous extremities have been pushing and insinuating themselves into and through the ground1 and by small knobs or suckers known as spongioles1 the rootlets or fibrous parts of the root pick up sustenance for the plant1 and it is then carried by tubes to the root1 and so on throughout the plant1 and with air ducts serve to keep the plant alive4 ,the stem emanates from the plumule1 and in a short time little knots develop upon it1 which are the incipient leaves4 ,the knots are divided into nodes and internodes1 because they appear on different sides of the stem and intermediate1 so as to alternate with each other1 and are really buds4 ,the issues unite also into leaf-stalks or petioles1 and extend into the leaf-frame or skeleton as we see it when the leaf has decayed4 ,so thus we have an upward and a descending growth1 which respectively constitute the stem and root of a flowering plant4 ,illustration3 ,fig4 #geb4--,tuberous 7fasciculated7 root4 ,some trees have roots growing from the stem1 as in the banyan tree1 and roots can produce stems as well as the latter can form roots4 ,the uses of roots are so well understood that we need not particularize them4 ,in many trees we find what are termed lenticell1 like holes in the bark4 ,these fissures will put forth roots under favourable circumstances4 ,these stem roots are called adventitious1 and by taking 8cuttings0 from plants we make good use of them for propagation4 ,illustration3 ,fig4 #gec4--;,banyan tree4 ,but there are underground stems as well as those which flourish and climb above it4 8,bulbs0 and 8tubers0 are common instances of these underground stems1 or 8rhizoma10 which are horizontal4 ,the ordinary stems are termed 8aerial0 stems to distinguish them from the earthy and subterranean4 ,the aerial roots of ivy are only used for support1 and are not its proper roots1 though some parasitic plants strike into the trees and are nourished by them4 ,,the ,,stem4 ,the stem is that portion of the plant-axis which grows upwards or above ground1 and may be1 as we have just read1 subterranean4 ,as the great function of the root is to procure sustenance for the plant1 the stem assists in carrying the nourishment through the branches and leaves4 ,we shall find two forms of stem--the underground1 or root-stock1 and the stem proper4 ,there are in these two former several varieties as under3-- #a4 ,the ,,bulb1 which is a short globular stem surrounded by thick leaves1 and producing buds--as1 for example1 the onion4 #b4 ,the ,,tuber1 similar to the foregoing in shape1 having no leaves1 however2 the potato is an instance4 #c4 ,the ,,rhizome 7root-stock71 like a root only producing buds1 which roots do not4 ,the iris will serve as an example4 ,the varieties of the stem-proper are3-- 7#a7 ,filiform1 or thread-like1 simple1 or branched1 as in mosses4 7#b7 ,the culno1 a thin1 hollow1 and frequently-jointed stem4 7#c7 ,the palm or simple stem1 seen in tree-ferns and palms4 ,it is marked by the scars of dropped leaves4 7#d7 ,the stalk1 very common1 of a green hue1 and its life is limited to a twelve-month as a rule4 ,the so-called 8stem0 of the hyacinth is not a stem1 it is a stalk1 or flower-stalk1 pushed forth for a temporary purpose4 7#e7 ,the ligneous stem is the perfected kind1 and an example will be apparent in every tree4 ,illustration3 ,fig4 #ged4--,transverse section of exogenous wood1 showing the growth of nine years4 ,illustration3 ,fig4 #gee4--,section 7magnified portion7 of the small cut a4 ,illustration3 ,fig4 #gef4--,section of an endogenous stem4 ,the duration of the stem of a plant is usually the same as of the plant--so we have annuals1 biennials1 and perennials4 ,the substance of the stem determines its character1 so we may have it solid1 or soft1 hollow1 tubular1 flexible1 rigid1 or a tough stem4 ,there are fibrous1 herbaceous1 and juicy stems4 ,they may be directed uprightly1 straight1 procumbently1 arched1 or creeping1 above1 or underground1 climbing1 clinging1 floating1 or twining4 ,there are many plants with little or no stem deserving the name1 as in the onion2 and we must all remember when studying botany that it is not the place where a portion of a plant may be found that constitutes it a root or a stem4 ,the form and structure should be studied1 and its purpose in creation4 ,so stems may be underground and roots above it4 ,the root and stem1 briefly treated of in the foregoing paragraphs1 have certain points of resemblance1 inasmuch as both consist of a main or trunk line1 so to speak1 from which branches diverge as 8rootlets0 and 8twigs02 and how beautiful the latter are any one can see in a good photograph of a wintry landscape4 ,but stems have nodes and internodes1 and roots have not1 and this is the great and apparent difference4 ,the covering of plant-stems is varied1 and many instances of such clothing will occur4 ,we have woolly stems and hairy stems1 which develop into thorny ones--for thorns are only strong hairs4 ,spines and stings and prickles defend the stems1 and keep rude hands from meddling4 ,we will now cut the stem and see what it is composed of1 and how it looks inside4 ,we have only to cut it across and again perpendicularly to find out a great deal about the interior structure of the stems of branching plants 7exogens74 ,the elder1 from which the whistle of our boyish days is fashioned with a penknife1 will serve any lad for an illustration4 ,inside we find what is called 8pith10 which is cellular tissue4 ,round this is fibre1 and outside is a skin1 or the plant-cuticle4 ,we may remark that the tissues of flowering plants are characteristic of the monocotyledonous and the dicotyledonous plants4 ,of the former we append an illustration1--a section of palm-stem1--and we find bundles of vascular tissue dispersed apparently at random amongst the cellular tissue of the parenchyma1 or cellular tissue4 ,these stems do not grow by the increase of the existing vascular tissue1 but by their new production at the circumference1 and so they grow in both directions1 laterally and uprightly4 ,these plants belong to the ,,endogens1 and if ,indian corn be grown we shall have full opportunity to study the formation4 ,in cutting a fern stem we are familiar with the 8oak0 pattern of the matter it contains4 ,we have few specimens of endogens in ,england4 ,the dicotyledonous stems are common to our trees and most plants1 and may therefore be considered with advantage4 ,the stem consists of the vascular tissue called 8pith10 and we give an illustration of the cells magnified very considerably4 ,the arrow indicates the outward direction 7fig4 #geg74 ,we here perceive the vascular bundle proper surrounded by a very large-celled tissue1 aabef4 ,the almost square cells1 aa 1 form the epidermis on which follows the less dense cellular tissue of the bark4 ,the latter surrounds a half-moon-shaped bundle of bast-cells1 c1 which are separated in the direction towards the interior1 by a layer of cambium1 ddd1 from the bundles of vascular tissue1 consisting of vessels and longitudinal cells4 ,the latter tissues may be distinguished in the transverse section by the thicker walls1 gg1 and by their greater breadth1 hh4 ,it is further to be remarked that the cambium transparent tissue1 dd1 appears on both sides of the bundles of vascular tissue1 and extends to the next bundle1 and thus presents an uninterrupted circle throughout the entire circumference of the stem4 ,illustration3 ,fig4 #geg4--;,dicotyledonous stem4 ,illustration3 ,fig4 #geh4--,stem one year old4 ,on examining the section of a one-year-old dicotyledonous stem1 magnified six times1 as in fig4 #geh1 we perceive several parts clearly distinguishable from each other1 corresponding with the arrangement of the bundles of vascular tissue4 ,enclosed by the epidermis1 a1 is a large-celled tissue1 b f and m1 in which a number of vascular bundles form a circle4 ,in each of these we notice that the outer portion1 consisting of bast-shell1 c1 is separated by the cambium1 d1 from the inner woody portion1 e4 ,the cambium forms a closed circle which penetrates through all the vascular bundles4 ,in the course of the further development of the stem1 the parts1 a b c1 constitute the bark1 the vascular bundles1 e1 the wood1 and the cellular tissue1 f1 its pith4 ,the tissues1 m1 penetrating between the vascular bundles1 are called the medullary rays4 ,the cambium is to be regarded as the most important part1 since it is the source of new bundles of vascular tissue which year by year increase the circumference of the stem4 ,illustration3 ,fig4 #gei4--,stems three and five years old4 ,the growth of a dicotyledonous stem is continued by the formation of a new circle of vascular bundles on the circumference of the stem in the second year4 ,each new bundle1 as has already been shown1 is produced in the cambium1 and consequently is deposited between the wood and inner bark4 ,thus every year a new layer is deposited between the previous formation and the bark2 and a section will exhibit these concentric rings of wood obviously distinct from each other2 and as one year is requisite for the formation of a single layer of wood1 these depositions are named annual layers or rings4 ,in fig4 #gei we have a representation of a stem three years old1 and one of five years of age4 ,the number of rings in the stem do not invariably agree with the number of years the tree has been growing1 but it may be accepted as a rule4 ,the stem is the medium of communication between the roots and leaves at first2 but after a year this important duty is deputed to the cambium layers of new woody tissue1 etc41 and as time goes on the living power has accumulated immediately under the bark4 ,so although the tree be quite hollow it will live4 ,the interior has been closed up by deposition of wood and has decayed2 but the life functions being relegated to the bark1 the old tree lives on4 ,if we remove the rind all round a tree it will die4 ,,the ,,leaves4 ,when in the spring the young leaves appear upon the trees1 and as summer advances they become fully developed1 we are all grateful for the beautifully varied tints of green1 and for the shade we can so fully enjoy4 ,the study of leaves is a most interesting and instructive one1 and nobody should omit to examine them4 ,their forms are infinite1 or1 at any rate1 countless2 their size as varied as their forms4 ,many attributes of the leaf will occur to every reader1 and we will briefly describe these essential organs of plants4 ,air and light are necessary to the development of leaves1 and their principal use is to present a surface to the food material which the plant absorbs4 ,they breathe1 as it were1 and absorb the carbonic acid from the atmosphere4 ,these functions are called 8assimilation10 8transpiration10 and 8respiration10 which we will detail by-and-by4 ,illustration3 ,fig4 #gfj4--;,compound leaf4 ,illustration3 ,fig4 #gfa4--,simple leaf4 ,leaves are distinguished according to position and duration4 ,some leaves have very simple forms1 others are compound1 so to speak4 ,some are plain and rounded1 others are toothed1 like the holly4 ,the skeleton of a leaf is a very interesting study1 and it will show the beautiful structure of these common objects4 ,the delicate lines of the green leaf are 8veins10 or sap-vessels1 which convey the necessary nourishment4 ,the leaves are called the 8embryonic0 7seed-like71 the radicle1 or root-leaf1 the stalk-leaf1 and the stipules1 which grow at the base of stem-leaves1 and the floral leaves1 which bear the flowers or fruit buds4 ,leaves which are developed at the end of a chief axis are termed blossoms4 ,of course it must be understood that all the different kinds of leaves do not occur upon the same plant4 ,the leaf may be accepted to mean the stem-leaf4 ,leaves are folded up in various ways1 and the manner in which this is accomplished is termed the vernation of the plant4 ,the leaves of endogens and exogens differ in their veining4 ,the former veins do not touch2 there is none of that beautiful interlacing which we find in the exogenous leaves4 ,in the former the veins rise from base to apex1 curving as they advance1 as in the well-known lily of the valley4 ,this 8nervous system0 of the leaf is its 8venation10 and the veins distributed in the blade or lamina of the leaf are twofold1--as remarked1--ascending in curves1 or diverging from a central nerve called the 8mid-rib40 ,these lateral nerves are either parallel or 8reticulate0--that is1 net-like4 ,illustration3 ,fig4 #gfb4--,net-veined leaf4 ,we will now examine the forms of leaves which are regulated by the divergence and extension of the divisions of the mid-rib4 ,thus we get an orbicular1 or peltate leaf2 palmate1 digitate1 and pedate forms also occur1 as may be seen in the illustrations1 pages #fgb and #fgc1 where all the varied shapes can be studied4 ,the leaf consists of a petiole or stalk1 and the lamina or blade4 ,the petiole is composed of bundles of vascular tissue2 the lamina is formed by their extension1 the interstices being filled with cellular tissue4 ,so we perceive that the leaves and stems are composed of similar materials4 ,to defend the tissue a skin1 or epidermis1 is placed upon the surface of the leaf1 and this epidermis is full of breathing holes1 or pores1 called stomates 7compare page #ffd74 ,there are also cells filled with chlorophyl1 which gives the leaf its green tint4 ,illustration3 ,fig4 #gfc4--,linden tree4 ,illustration3 ,fig4 #gfd4--,stomates1 highly magnified4 ,the petiole may be absent in a leaf1 and when it is the leaves are termed sessile1 or sitting leaves4 ,these leaves sometimes coil round the stem1 and are called 8amplexicaul10 or stalk embracers4 ,these are simple leaves4 ,compound leaves are composed of several blades or lamin on a stalk1 and are seldom sessile4 ,,simple ,,leaves are almost innumerable in form and variety4 ,leaves may be equal or unequal1 acicular or linear1 rounded or oval1 cordate or obcordate1 reniform or sagittate1 perfoliate or connate1 crisp1 whorled or truncate1 retuse1 acuminate or mucronate4 ,the margins of simple leaves again are entire1 deft1 notched1 crenated1 crenulated1 sinuous1 or dentated4 ,they are pinnatifid1 multifid1 or lobed1 according to the divisions of the leaf4 ,illustration3 ,,leaves4 ,i4 ,,depending ,,on ,,form4 ,lanceolate 7,privet74 ,ovate 7,fuchsia fulgens74 ,oblong 7,primrose74 ,cordate 7,white ,bryony74 ,palmate 7vine74 ,,ii4 ,,depending ,,on ,,margin ,,and ,,arrangement4 ,serrate 7,rose74 ,biserrate 7,elm74 ,crenate 7,betony74 ,entire 7,lilac74 ,digitate 7,lupin74 ,pinnate 7,vetch74 ,bipinnate 7,acacia74 ,pinnatifid 7,crepis74 ,ternate 7,clover74 ,biternate 7,columbine74 ,,iii4 ,,depending ,,on ,,point4 ,obtuse 7,dock74 ,mucronate 7,holly74 ,retuce 7,snowball74 ,emarginate 7,bladder ,senna74 ,compound leaves are also divided into classes4 ,the pinnate1 as the rose-leaf1 the clover trefoil4 ,there are 8doubly pinnate10 the digitate1 as in the horse chestnut4 ,compound and simple leaves can be readily distinguished by inspection1 for the former are 8articulated0 to the stalk and can be separated1 but the simple leaves will be torn1 for they are confluent throughout4 ,leaves are evergreen or deciduous1 accordingly as they retain or shed themselves4 ,the ordinary leaf is deciduous2 the fir and the yew and the imported laurel are evergreens4 ,we have very few of these as natives of ,england1 the ivy1 yew1 and fir being the three most common4 ,sometimes a plant peculiar to ,killarney1 and known as the arbutus1 is included in the list4 ,but the ,scotch fir and the yew are distinctly native evergreens4 ,the detailed characteristics of leaves must be passed over until we come to the fly-catching leaves--such as ,venus' fly-trap1 the droseras1 and nepenthes1 which appear to catch and devour insects for food4 ,the ,venus' fly-trap may be examined1 and we shall find the leaves covered with tiny and very sensitive hairs4 ,often a fly happens to alight upon the leaf1 which is extended in a most innocent manner 7see illustration74 ,as soon as the fly settles the leaves close1 and the digits lock tightly together1 thus preventing the escape of the prey4 ,the droseras1 sarracenias1 and nepenthes also kill their food4 ,the sarracenias form curious cups1 into which insects are enticed in search of fluid1 and then1 as in the case of the house-haunting cockroach1 they cannot get out again4 ,the nepenthes have a cup and lid for insect-catching1 and within the cup a liquid is secreted4 ,we will close this portion of our subject with a quotation from a recent article upon botany referring to leaf arrangement4 ,the writer says3-- ,illustration3 ,fig4 #gfe4--,leaf of ,dion4 ,illustration3 ,fig #gfg4--,leaf of ,nepenthes4 ,illustration3 ,fig4 #gff4--,sarracenia4 8,efforts have been made to determine the laws to which these various modes of leaf-arrangement may be referable4 ,the result is found in the doctrine of #8,phyllotaxy1' as it is called1 the fundamental principle of the whole being that ,nature1 in the disposition of the leaves upon the stem1 works upon precisely the same idea as that which is set forth so distinctly and elegantly in the common pine-cone2 and1 on a minor scale1 in the beautiful cone of the female hop2 not to mention the quasi-cones of many species of tropical palm1 such as the ,sagus and the ,mauritia2 nor to mention either1 the very delicate repetition of the whole series in the florets of the ,rudbeckia and the ripening fruits of ,chaucer's daisy4 ,in every one of the flower and fruit arrangements mentioned1 the idea is the spiral1--the same sweet old fashion which we have had in the twining stems of the convolvulus1 the woodbine1 and the scarlet bean2 which comes out again in many a sea-shell1 and in human ringlets2 and this idea1 according to #8,phyllotaxy1' governs the position of the leaves4 ,following alternate leaves up the stem1 their sequence is clearly spiral4 ,through the non-development of internodes1 they are brought closer and closer together2 and even when the entire mass of foliage is concentrated and condensed into the rosulate form1 as in the houseleek and the ,echeverias1 the spiral prototype is still distinguishable4 ,the whole matter has been reduced to one of arithmetical exactitude2 and for those who love calculations and 8fractions10 the determination of the spirals1 their continuity and intermixture1 supplies abundance of curious entertainment4 ,all three modes of leaf-arrangement are found in certain herbaceous plants1 none disclosing this particular kind of playfulness more plainly than the common pyramidal ,loosestrife1 ,lysimachia vulgaris1 and the purple ,lythrum of the waterside1 in each of which very handsome wild flowers1 alternate1 opposite1 and whorled leaves may be found in near neighbourhood4 ,alternate and opposite leaves are also met with1 side by side1 in various species of ,myrtace2 and imperfectly1 upon young shoots of the common ash-tree4 ,the rule is1 nevertheless1 that there shall be uniformity1 and in many of the largest natural orders the rule is never broken4 ,in the ,rosace the stem leaves are invariably alternate2 in the ,gentianace they are invariably opposite40 ,illustration3 ,fig4 #gfh4--;,branch of horse chestnut4 ,,footnotes3 #ce ,dr4 ,carpenter4 ,,chapter ,,lii4 ,,flowering ,,plants4 ,,organs ,,of ,,increase ,,and ,,reproduction--,,the ,,flower--,,the ,,calyx--,,the ,,corolla--,,the ,,stamen--,,the ,,pistil4 ,some of the simplest plants are propagated by spores1 which are detached1 and fall upon the ground to vegetate2 but in the case of the higher orders the reproduction of species is a much more elaborate process1 and is carried on by means of certain organs called flowers4 ,small buds1 or ovules1 are formed1 which develop into seed4 ,plants also produce buds1 which grow upon various parts of it1 and are capable of reproducing their species4 ,we will first speak of ,,flowers4 ,flowers are not only the lovely blossoms we cut and place in our rooms1 but the reproductive organs of plants which may be very plain and simple or gorgeous and fragrant1 and in all probability the so-called flowers are few in comparison to the unrecognized flowers4 ,trees and bushes flower equally with the rose and the pink and carnation4 ,vegetables flower as well as the lily1 though we do not recognize it so well4 ,let us now examine the 8flower40 ,flowers may consist of four parts1 but it is not absolutely necessary that they should contain more than two4 ,the four portions of a complete flower are-- #a4 ,,the ,,calyx4 #b4 ,,the ,,corolla4 #c4 ,,the ,,stamen4 #d4 ,,the ,,pistil4 ,the two last mentioned are essential4 ,the four organs are placed around a pedicel or peduncle 7flower stalk71 and are known as floral whorls4 ,the ,,calyx is the outermost whorl of all when all exist4 ,the portions of the calyx are known as sepals4 ,the ,,corolla is usually the showy portion--the attraction of the flower4 ,the pieces of the corolla are called petals4 ,the sweet fluids of the plant are here concealed4 ,these parts--the calyx and corolla--are known as the floral envelopes1 or 8perianth40 ,the tulip has one whorl only1 and it is called the envelope4 ,the calyx sometimes falls before the flower is full blown1 as in the poppy4 ,its lower portion is the 8throat10 and the shape of the organ varies1 as will be seen by the illustrations4 ,illustration3 ,fig4 #gfi4-- #a4 ,tubular4 #b4 ,clavate1 or club-shaped4 #c4 ,tubinate1 or top-shaped4 #d4 ,campanulate1 or bell-shaped4 #e4 ,funnel-shaped4 #f4 ,urceolate1 or urn-shaped4 #g4 ,globular4 ,the sepals are usually three to five in number4 ,the poppy has two1 and the well-known wall-flower four free--that is1 disunited--sepals4 ,the primrose possesses five4 ,the calyx is the outside rim of all1 and we may thus remember it1 because its sepals alternate with the petals of the corolla4 ,the petals may be formed cup-fashion1 as in the lily of the valley1 and here we have these sepals and petals in groups of three each4 ,illustration3 ,fig4 #ggj4--,trimerous corolla4 ,illustration3 ,fig4 #gga4--,tetramerous4 ,illustration3 ,fig4 #ggb4--,pentamerous corolla4 ,illustration3 ,fig4 #ggc4--,monopetalous corolla4 ,the petals differ from ordinary leaves1 and in them we find all the beautiful tints and the odour we imbibe from blossoms4 ,the forms of corolla correspond to those of the calyx1 and are called by the same names4 ,but when corollas are absent the petals of course cannot provide the necessary colours for the flower4 ,then the calyx is gifted1 and the sepals are brilliant4 ,thus ,nature provides for everything4 ,corollas are found with five or ten petals1 and sometimes with three1 six1 and nine--the numbers always doubling or adding the original number4 ,there may be four petals or eight1 as in the 8tetramerous0 corolla 7fig4 #gga74 ,instances of others are illustrated1 and a plant whose petals1 sepals1 and stamens are numerically equal1 or are multiples of each other1 are termed 8symmetrical40 ,the 8regular0 flower does not vary much1 as the petals are of the same size and shape1 but there are many 8irregular0 flowers--as the pea--in which portions of the calyx or corolla are of different shapes4 ,the 8labiate0 and the 8campanulate0 are illustrated in figs4 #ggd1 #gge1 including the convolvulus and the snap-dragon4 ,these are but a few examples of an almost endless diversity4 ,the 8regular0 flowers--exemplified in the buttercup and convolvulus--always present the same figure to the observer4 ,to the petals the beautifully-varied colours of plants are due1 and though it is not possible to enter upon the subject here1 we may conclude that the various beauties of the colours of flowers are owing to light and air acting upon the various 8colouring matters0 contained in the plant4 ,seeds planted in a dark cellar will spring up pale2 admit light1 and they will become green1 for light thus acts upon the chlorophyl4 ,but the flowers of the plant are not so dependent upon light1 as can easily be proved4 ,many interesting experiments have been made upon flowers by acids and gases4#cf ,illustration3 ,fig4 #ggd4--,labiate corolla4 ,illustration3 ,fig4 #gge4--;,campanulate4 ,the ,,stamens are the next in order for our consideration4 ,they are found within the petals 7or the calyx if no petals be present74 ,stamens vary very much in different plants both in number and general features--but1 as in the case of petals1 they keep1 as a rule1 to certain numbers and doubles of them4 ,the stamen consists of two portions--a lower1 thread-like part called the filament1 and an oblong bag or head1 termed the anther4 ,this contains a powdery matter called pollen1 and is the essential part of the stamen4 ,the filament1 which corresponds to the petiole of the leaf1 may be absent1 in which case the anther is called sessile4 ,a lily will show the stamens perfectly1 the anther being prominent in many other plants also1 such as daffodils and fuchsias4 ,the stamens are very important organs with regard to the classification of plants--for number1 length1 and position1 whether free or united1 are all characteristic features4 ,the length of filaments is always the same in the same kind of plant1 and therefore is a very palpable test4 ,the anther contains the pollen1 a powdery matter1 usually yellow-coloured1 but sometimes also red1 brown1 violet1 or green-coloured4 ,pollen-grains vary from #a_/bj to #a_/cjj of a line in diameter4 ,under a powerful microscope they appear as ellipsoidal1 or sometimes spherical1 triangular1 polyhedral vesicles1 filled with a granular semi-fluid matter4 ,to effect fecundation1 the pollen-grains must come into contact with a certain part of the plant which is intended to receive them1 and which is called the ovule1 and is found in the fourth or innermost verticil of the flower1 the pistil4 ,of the further development of the ovule1 we shall have occasion to speak in the paragraph treating of the seed4 ,at the proper time the anther opens and discharges its contents1 the pollen-grains1 some of which reach the place of their destination4 ,the position of the stamens to the pistil is usually such that the latter can readily receive the pollen-grains4 ,in many plants1 however1 the stamens are too short to reach the pistils2 or the two essential organs of reproduction are in separate flowers1 or even on different plants4 ,in such cases1 the conveyance of the pollen from the anthers to the pistils is effected by the agency of the wind1 or by that of insects1 and more particularly by the bee4 ,if the anthers are removed from the flower previously to their opening1 no fruit is produced4 ,varieties of flowers and fruits are produced artificially1 by shaking the pollen of one plant upon the flowers of another1 deprived of the stamens4 ,many esteemed sorts of stock-gilliflowers and pinks have been produced in this way4 ,the pistil constitutes the fourth and innermost whorl1 and occupies accordingly the centre of the flower and the apex of the axis1 whose growth is terminated with the production of the fruit4 ,illustration3 ,fig4 #ggf4--,pistil4 ,the pistil also is formed by one or several modified leaves1 called carpels1 in this part of the flower1 and which exhibit a more marked resemblance in colour and structure to the ordinary leaves than the stamens and petals do4 ,the formation of the pistil from the leaf may be considered to proceed in this manner3 that the edges of the leaf are folded inwards and unite1 whilst the mid-rib is prolonged upwards 7fig4 #ggf;,a74 ,the place where the margins of the folded leaves are united is called suture or seam 7ventral suture1 in contradistinction to the mid-rib1 which is called the dorsal suture72 and it is here that the seed-buds or ovules are developed4 ,the pistil consists of two parts--viz41 the ovary or germen1 which contains the ovules or young seeds1 a1 and the stigma1 b1 either placed upon the ovary1 or upon the style1 or stalk1 which is between the stigma and the ovary4 ,a pistil may be of one carpel 7simple71 or of more than one 7compound74 ,the carpels or the carpellary leaves are the 8ovaries40 ,the pistil is a very important test for the classification of plants2 some trees have no pistils1 and the ovules are consequently naked4 ,such plants are called gymnosperm4 ,the conifer 7firs and pines7 are thus recognizable1 and the position of the ovule is very much that of the ordinary bud4 ,,footnotes3 #ce ,respecting artificial colouring of flowers1 see page #cbi4 ,,chapter ,,liii4 ,,flowering ,,plants 7continued74 ,,the ,,floral ,,axis--,,inflorescence--,,fruit--,,seed --,,nutrition ,,of ,,plants--,,absorption ,,of ,,constituents4 ,there are certain arrangements and mutual relations of the various portions of the flowers which we have mentioned that it is useful to consider4 ,the floral axis refers to the position of the verticils1 and inflorescence signifies the arrangement of the flowers on the stem4 ,flowers which possess both stamens and pistil are hermaphrodite2 those with only stamens are male2 those with the pistil female flowers4 ,if both organs be absent the flower is neutral4 ,plants bearing flowers in clusters form several distinct groups1 to which appropriate terms are applied indicative of their respective form of flora arrangement4 ,illustration3 ,fig4 #ggg4--7a7 ,spike4 7#b7 ,catkin4 7#c7 ,spadix4 7#d7 ,cone4 ,in the examination of this kind of inflorescence 7indefinite or axillary inflorescence71 the first object of remark is the general or primary peduncle1 termed rachis1 and which bears numerous leaflets called bracteoles or bractlets1 from whose axils arise the pedicellate or sessile flowers4 ,the lower bracts often produce no flower-buds in their axils1 and form instead a whorl surrounding the heads of flowers on the primary axis1 and which is called involucre 7as in the sun-flower1 for instance74 ,illustration3 ,fig4 #ggh4--,raceme4 ,illustration3 ,fig4 #ggi4--,panicle4 ,illustration3 ,fig4 #ghj4--;,corymb4 ,the different varieties of axillary inflorescence are determined principally by the elongation or depression of the axis1 the presence or absence of stalks to the flowers1 and the form and nature of the bracts4 ,we distinguish-- ,illustration3 ,fig4 #gha4--,umbel4 ,illustration3 ,fig4 #ghb4--;,capitulum or ball4 #a4 7#a7 ,the spike 7fig4 #ggg74 ,in this form of inflorescence1 sessile or short-stalked flowers are arranged along the rachis in the axils of the bracts2 the spike is said to be compound when small spikes or spikelets arise again from the bracts of the secondary axis4 7#b7 ,the catkin or amentum 7fig4 #ggg #b72 a spike1 usually pendulous1 which falls off1 rachis and all1 by an articulation1 as in the willow or hazel4 #c4 ,the spadix1 a thick fleshy spike 7fig4 #ggg #c72 examples1 arum and calamus4 #d4 ,the cone1 a fruit-bearing spike1 covered with scales 7fig4 #ggg #d72 examples1 the conifer4 #e4 ,the raceme or cluster1 a spike with the flowers on longer pedicels 7fig4 #ggh72 examples1 the currant4 #f4 ,the panicle1 a branching raceme 7fig4 #ggi1 ,yucca gloriosa74 #g4 ,the thyrsus1 a dense panicle1 with longer peduncles in the middle than at the extremities2 example1 lilac4 #h4 ,the corymb1 a raceme1 in which the lower flower stalks are elongated and raised to nearly a level with the upper 7fig4 #ghj7--;example1 cerasus mahaleb4 #i4 ,the compound or branching corymb1 a corymb in which the secondary axis again sub-divides2 example1 ,pyrus terminalis4 #aj4 ,the umbel3 in this form the primary axis is greatly depressed1 and the peduncles arise from a common point1 and spread out like radii of nearly equal length1 a whorl of bracts 7involucre7 surrounding the common base4 ,in the compound umbel 7fig4 #gha71 ,daucus carota1 the secondary axis ends in small umbels surrounded by bracts1 which is termed an involucel4 ,this is observable in the umbelliferous plants--carrot1 parsley1 hemlock1 etc4 ,illustration3 ,fig4 #ghc4--;,inflorescence4 ,a very peculiar kind of inflorescence1 which characterises the great family of the composit1 is illustrated by fig4 #ghc4 ,we see here the enlarged floral axis or receptacle1 a1 surrounded by several whorls or bracts1 b b1 which constitute a general involucre2 the membranous bracts1 7pale71 b b1 seen in the receptacle1 bear in their axils the sessile florets1 c and d1 which either have a calyx1 e e1 or not4 ,the florets on the receptacle are either all of them tubular 7d7 or ligulate 7tongue or strap-shaped72 florets 7c7 are associated with the tubular ones4 ,the receptacle is not always flat1 but frequently presents a convex1 globular1 conical1 concave1 etc41 shape4 ,in the absence of pale the receptacle is said to be naked4 ,the florets at the margin1 or circumference1 are termed marginal flowers1 or flowers of the ray2 the florets in the disc 7centre71 central flowers1 or flowers of the disc4 ,some plants bear male and female flowers on the same stem4 ,these are termed moncious plants4 ,the oak is an instance4 ,the dicious plants are those which bear stamens and pistil1 or separately1 on different plants1 like willows4 ,we will now glance at the functions of the stamens and pistil4 ,the ovule has been mentioned as a tiny body in the ovary1 and it consists of a nucleus1 and cellular tissue surround it1 leaving a small hole called the micropyle1 into which the pollen tube enters after passing through the ovary4 ,as in the animal creation1 the unions of different families succeed best2 no close relationship will fertilize so well as with other flowers4 ,fertilization is accomplished in two ways2 7#a7 by the action of the wind1 by which the pollen is carried away to other plants2 and 7#b7 by means of insects--the bee particularly4 ,these flowers have distinctive qualities relatively4 ,in the case of the pine the pollen is powdery2 so those plants which are thus fertilized are the dicious species1 which include the poplar1 the oak1 and the birch1 as well as the pines4 ,these are all wind-carried pollen plants4 ,the nettle is illustrated here with male and female flowers4 ,illustration3 ,fig4 #ghd4--,male flower of nettle4 ,plants fertilized by insects are visited by them1 and they carry away upon their heads1 or bodies1 the pollen1 which is then thrust into the stigma by the insect2 or perhaps birds may carry the pollen in the same way after sipping the nectar1 and thus playing an unconscious1 but most important1 part in the economy of nature4 ,illustration3 ,fig4 #ghe4--;,female flower of nettle4 ,we always find the ovule at the termination of an axis2 it is unable to form a seed alone4 ,the pollen grains must fertilize it1 and in consequence many ovules come to nought4 ,the ovule is produced in the pistil1 which1 as before stated consists essentially of two parts--the ovary and the stigma2 the latter secretes a fluid to hold the pollen4 ,we annex the representation of a highly-magnified pistil 7vertical section1 fig4 #ghf;a74 ,the pollen grains are indicated by d1 attached to stigma1 c1 projecting through the style1 b1 into the ovary1 a1 and passing through the ovules4 ,illustration3 ,fig4 #ghf4--;,erect ovule4 ,with the transmission of the pollen to the ovary of the pistil1 the functions of the anther and stigma terminate2 accordingly these parts of the flower rapidly wither and decay after fertilization4 ,the filaments1 the style1 and the petals speedily participate in the decay1 but the sepals remain sometimes persistent in an altered form4 ,the ovary and its contents alone proceed in their further development1 and undergo material changes1 in which1 however1 the bracts and the calyx often participate4 ,the fully developed and matured ovule1 the seed1 is1 of course1 regarded as the essential part of the fruit2 the enlarged ovary forms the pericarp1 enclosing the seed4 ,the form of the pericarp determines the external appearance of the denomination of the fruit4 ,the structure of the fruit1 and the arrangement of its parts depends in a great measure upon the number and position of the carpellary leaves in the pistil1 and the manner and extent of their union1 and the extent to which their edges are folded inwards4 ,illustration3 ,fig4 #ghg4--;,dorstenia4 ,illustration3 ,fig4 #ghh4--;,dandelion4 ,illustration3 ,fig4 #ghi4--;,apple4 ,illustration3 ,fig4 #gij4--;,follicles of larkspur4 ,illustration3 ,fig4 #gia4--,sycamore fig4 ,the carpellary leaves occupy the summit of the floral axis4 ,the axis terminates either in one single carpel1 in which case the ovary is one-celled1 or unilocular2 or the axis is surrounded by several carpels1 in which case the manner of their union determines the number of cells in the ovary4 ,,the ,,fruit4 ,illustration3 ,fig4 #gib4--,sycamore fig4 ,illustration3 ,fig4 #gic4--;,fruit of a composite4 ,illustration3 ,fig4 #gid4--,section of a berry4 ,the carpels are the chief agents in the formation of the fruit1 and they form the endocarp 7core71 and sometimes the whole pericarp1 or seed-vessel4 ,upon the nature of the various parts and the changes they undergo during the ripening of the seeds the nature of the fruit depends4 ,the fruits are classified1 some being the produce of a single carpel1 others of several united carpels4 ,illustration3 ,fig4 #gie4--,umbelliferous plant and its fruit4 ,fruit1 in botany1 is by no means limited to the juicy products of trees or plants which are so refreshing in the summer weather1 and so acceptable in any form4 ,in plant life the herb yielding seed produces a fruit equally with the orange or the apple4 ,the fruit is the outcome of the varied processes of the plant4 ,we may trace the plant from its tiny1 sometimes very minute seed1 through stem to flower and seed again4 8,in the final struggle1 even when life is hopeless1 and starvation1 in consequence of drought1 is imminent--when all is hopeless and barren1 the plant will make an effort to produce its fruit and flower40 ,this is a very touching and interesting fact in nature--this last attempt to beautify the earth and to propagate its species for the use of man4 ,illustration3 ,fig4 #gif4--,three-celled capsule4 ,illustration3 ,fig4 #gig4--,poppy4 ,fruit1 then1 is not limited to the market and the stall4 ,this statement scarcely needs proof2 but if we consider for a moment the number of 8wild0 fruits--the parents1 probably1 of our table-fruits--we find many we cannot eat4 ,in short1 out of the hundred thousand plants which bear flowers scarce one two-hundredth part serve us as producers of edible fruits4 ,illustration3 ,fig4 #gih4--,three-celled capsule4 ,illustration3 ,fig4 #gii4--,water melon4 ,the fruit is the result of the flower1 and if any objection be made by readers on the part of the common fig1 it will be found that this appreciated fruit really consists of male and female flowers that are fertilized by the action of minute insects1 which enter and depart 7sometimes they die1 and are found dead and black in the figs74 ,no blossom is perceived on the tree1 because within the green sac the so-called 8seeds0 7really the fruits7 are developing4 ,a fig is a sac full of fruits4 ,the legume or pod is formed of a single carpel bearing seeds4 ,we annex illustrations of the pod4 ,the covering is called the pericarp1 and the parts when opened separate into valves4 ,dehiscent fruits shed their seeds1 indehiscent fruits do not2 they lie within the seed-vessel1 like the acorns and nuts4 ,these are dry fruits1 but there are others of a soft nature1 such as apples or gooseberries4 ,illustration3 ,fig4 #hjj4--,legume4 ,illustration3 ,fig4 #hja4--,legume opened4 ,illustration3 ,fig4 #hjb4--,legume 7pea74 ,illustration3 ,fig4 #hjc4--;,gland 7acorn74 ,illustration3 ,fig4 #hjd4--,stobule 7hop74 ,illustration3 ,fig4 #hje4--;,drupe 7plum74 ,illustration3 ,fig4 #hjf4--;,berry 7currant74 ,fruits are variously named1 and underneath will be found a list4 ,we have the aggregate1 like the mulberry1 etc42 the dehiscent fruit of one carpel like the pea1 etc42 the simple fruits as cherry1 nettle1 wheat1 etc4 ,the dandelion fruit is often a precious object in children's estimation1 as it is blown away to ascertain the time4 ,there are indehiscent fruits with many carpels1--the common buttercup1 for instance1 and the strawberry4 ,a list is added4 a4 ,,fruits ,,which ,,are ,,the ,,produce ,,of ,a ,,solitary ,,carpel4 #a4 ,the gymnospermous fruit1 where the seed lies naked in the axils of the ligneous bracts1 as in the cone of the fir and spruce tribe4 #b4 ,the legume or pod1 which is formed of a solitary carpel bearing seeds on the ventral suture4 ,it characterises the pea and bean tribe 7leguminos74 #c4 ,the follicle is a mature carpel containing several seeds1 and opening by the ventral suture4 ,there are usually several follicles aggregated together2 examples1 larkspur1 monkshood1 evergreen4 b4 ,,fruits ,,which ,,are ,,the ,,produce ,,of ,,several ,,carpels ,,united4 #d4 ,the capsule consists of two or more carpels1 either simply laterally united 7one-celled or unilocular capsule71 or folded inwards towards the axis1 but without reaching it 7spuriously multilocular capsule71 or uniting with the axis 7bilocular1 trilocular1 multilocular capsule74 ,examples of capsular fruit--mignonette1 balsam1 violet1 poppy1 etc4 #e4 ,the siliqua or long pod is formed of two carpels1 and longitudinally divided into two parts by a spurious dissepiment called the replum2 examples--cabbages1 stock1 wallflower1 etc4 ,the silicula is a broad and short pod2 examples--,iberis1 shepherd's-purse1 etc4 #f4 ,the cariopse 7caryopsis1 having the appearance of a nut71 is a monospermous or one-seeded fruit1 with an indehiscent membranous pericarp1 closely investing the seed or incorporated with it2 examples--rye1 wheat1 and other grains4 ,illustration3 ,fig4 #hjg4--;,capsule 7poppy74 ,illustration3 ,fig4 #hjh4--,siliqua 7shepherd's purse1 wallflower74 ,illustration3 ,fig4 #hji4--;,caryopsis 7wheat74 #g4 ,the achnium is a dry1 monospermous1 indehiscent fruit with one seed2 examples--cashew1 ranunculus1 strawberry1 etc4 #h4 ,the nut or glans is a one-celled1 indehiscent fruit1 with a hardened coriaceous or ligneous pericarp2 examples--hazel-nut1 acorn1 etc4 ,the nucula1 or little nut1 is a cariopse1 with a solid coriaceous pericarp2 examples--buckwheat hemp1 etc4 ,illustration3 ,fig4 #haj4--,nut 7hazel-nut74 #i4 ,the berry 7bacca7 is a pulpy1 succulent fruit1 with soft rind2 examples--the gooseberry and the currant4 ,the pepo or peponida 7pumpkin71 illustrated by the fruit of the gourd and melon1 and the hesperidium1 illustrated by the fruit of the orange and lemon1 are modifications of the berry4 ,illustration3 ,fig4 #haa4--,strawberry4 #aj4 ,the drupe 7drup1 unripe olives72 the mesocarp is generally pulpy and succulent1 the endocarp hard2 examples--the cherry1 the peach1 the plum1 etc4 #aa4 ,the pome 7pomum1 or apple72 the outer parts of the pericarp form a thick cellular1 eatable mass2 the endocarp 7core7 is scaly or horny1 and encloses the seeds within separate cells2 examples--the apple1 pear1 etc4 ,fruits consisting of the floral envelopes and the ovaries of several flowers united into one1 are termed multiple or anthocarpous2 the sorosis 7cluster-fruit3 example--the pine-apple1 the breadfruit1 the mulberry71 the sycosis 7fig-fruit71 and the strobilus 7fir-cone71 form varieties of the anthocarpous or multiple fruit4 ,,non-,,flowering ,,plants4 ,the cryptogamia or acrogens is the botanical term for these plants1 of which we must be very brief in our description1--not that the subject is not worthy of a much larger space than we can devote to it1 but our pages are not elastic4 ,there are numbers of plants without pistils or stamens properly so called4 ,they are hidden from human observation--buried out of sight2 and in the fern1 moss1 and other primitive plants they are thus hidden4 ,there are several families of the cryptogamia1 but two main sections include them all--viz41 the cormogens and thallogens4 ,these are sometimes known as cormophytes and thallophytes1 but the former will be our terms1 and they include the ferns1 alg1 lichens1 and mosses1 with many other families1 which we do not propose to examine in this summary sketch4 ,the microscope will here be a great aid if not always absolutely necessary for any close investigation4 ,illustration3 ,fig4 #hab4--,liverwort4 ,illustration3 ,fig4 #hac4--;,hypnum4 ,we are all familiar with the appearance of ferns1 and we may commence with a few observations concerning them4 ,they are an extensive family and very beautiful1 some of the tropical species being particularly noticeable for elegance4 ,we are here mostly concerned with the development of the plant4 ,the polypod ferns fructify under the leaves or 8fronds10 which open from a ball4 ,the seed-cases or sorri are situated at the back of the fronds in brown spots1 and when examined they will be found to be collections of capsules like tiny cases4 ,there is a kind of band at the upper part which at the proper time is extended1 and tearing open the capsule releases the seeds4 ,these seeds or 8spores0 are very minute1 and not properly seeds but buds1 every one of which can generate seeds4 ,so if we try to grasp in imagination the generating powers of a few fern fronds1 we shall miserably fail in the attempt4 ,illustration3 ,fig4 #had4--;,horsetail4 ,illustration3 ,fig4 #hae4--;,bryum4 ,some ferns have the 8spores0 upon the summit of the frond4 ,the osmundas belong to this family1 and are known to all as the 8flowering fern10 a contradiction palpable enough under the circumstances4 ,the beautiful dust upon some ferns has been mistaken for 8spores0 by many people1 but it is merely a natural ornament of the plant4 ,the venation and vernation of ferns are very curious1 but in the determination of ferns the only sure way is to consider the sorri and the venation4 ,the differences that puzzle may be little or great1 but when the sorri have been examined all doubts will be set aside4 ,there are about three thousand varieties of ferns known1 and we give a few illustrations of them1 although any detailed description is out of the question1 for we have to mention the beautiful mosses of which there are in ,britain more than five hundred different species1 all extremely beautiful1 perfectly innocuous1 and even beneficial4 ,,the ,,mosses ,,and ,,alg4 ,these plants are extremely lowly in the score of creation1 and also in stature4 ,very few mosses attain any elevation1 only the 8sporangia0 shoot up1 and the plants are very delicately formed1 the leaves being all of the same pattern4 ,they are common in damp situations1 and thrive in woods1 streams1 and banks4 ,the ,fontinalis is a river moss1 while the ,hypnum is found in hedges4 ,the ,lycopodiace or the club-moss family is intermediate between ferns and mosses4 ,they are found in warm1 moist climates1 and contain a sort of brimstone4 ,they grow well with ferns under glass4 ,illustration3 ,fig4 #haf4--;,diatoma vulgaris4 ,illustration3 ,fig4 #hag4--;,club-moss4 ,the ,musci or moss-family proper are useful in various ways4 ,we have also the liverworts1 which bear some resemblance to lichens4 ,they grow between stones near water1 or in damp situations4 ,there are two distinct families1 both beautiful when examined1 and are named ,marchantiace1 and ,jungeramanniace1 or scale moss4 ,illustration3 ,fig4 #hah4--,scale-moss4 ,illustration3 ,fig4 #hai4--,various diatomace4 ,the ,thallogens or ,thallogen include alg1 lichens1 and fungi1 which are the lowest of the plants1 and all very much alike4 ,the alg are termed 8protophytes10 and consist of living cells propagating by subdivision1 or union4 ,the thallogens have therefore no distinct axes1 leaves1 or stomata4 ,the alg are thus simply cellular plants found in salt or fresh water1 hot and cold4 ,they sometimes appear as 8slime40 ,some contain silicia1 and are termed ,diatomace1 and these propagate by subdivision1 and when they die their shelly covering remains1 and we find the shells or cases in all earthy formations4 ,these diatomace have been raised from the beds of oceans1 and ,atlantic soundings have revealed their presence1--as mud1 when examined1 proves to be these remains of vegetable shells4 ,thus the infinitely little in the animal and vegetable worlds meet at the bottom of the sea1 as well as on dry land4 ,there are marine and fresh-water alg--the former familiar to us as seaweeds which possess air-bladders that children love to explode1 and which assist the alg to float4 ,they attach themselves to rocks1 generally at the base2 the lovely colours of seaweeds are well known4 ,they will be recognized under the name of 8tangle0 7fucus71 which1 when burned1 gives kelp and barilla1 which is full of iodide and sodium4 ,the ,sargasso ,sea is composed of miles of alg which live in the open ocean4 ,the ,carrageen or ,irish moss is very nutritious and useful in consumptive cases4 ,indeed1 all alg1 if not absolutely useful1 are certainly not deleterious4 ,the 8bladder-wrack0 was formerly useful for the production of soda4 8,the life-history of one of these uni-cellular plants in its most simple form1 can scarcely be better exemplified than in the ,palmogea macrococca1 one of those humble forms of vegetation which spreads itself as a green slime over damp stones1 walls1 etc4 ,when this slime is examined with a microscope1 it is found to consist of a multitude of green cells1 each surrounded by a gelatinous envelope2 the cell which does not seem to have any distinct membranous wall is filled with granular particles of a green colour1 and a #8nucleus' may sometimes be distinguished through the midst of these4 ,when treated with tincture of iodine1 however1 the green contents of the cell are turned to a brownish hue1 and a dark-brown nucleus is distinctly shown4 ,other cells are seen1 which are considerably elongated1 some of them beginning to present a sort of hour-glass contraction across the middle2 in these is commencing that curious multiplication by duplicative subdivision which is the mode in which increase nearly always takes place throughout the vegetable kingdom40#cg ,illustration3 ,fig4 #hbj4--;,bladder wrack4 ,illustration3 ,fig4 #hba4--,lichen4 ,,lichens are numerous1 and may be found upon the bark of trees in dry forms of grey and yellow growth1 and on walls and old stones in our graveyards4 ,on the hills we find them growing upon the granite1 and it would appear that they prefer stone to any other holding ground4 ,the ,arctic lichens form the principal food of the useful reindeer1 and 8,iceland moss0 is represented as wholesome for man4 ,lichen is derived from the ,greek term for 8wart40 ,the ,,fungi are very important1 and with them we will close our summary4 ,they include the favourite mushrooms and poisonous toad-stools1 with many other 8fungous growths10 from the 8mould0 on the jam pot to the mushroom4 ,some of these fungi are peculiar to the substances upon which they exist1 and are in numerous instances destructive4 ,the microscopic fungus ,puccinea graminis is the parasite which fixes itself to corn1 and produces the disease known as mildew1 and the ,uredo segetum 7another microscopic fungus7 causes the 8smut02 the 8bunt0 is caused by the ,uredo ftida1 and the 8spur0 or 8ergot10 which attacks rye1 is caused by the ,acinula clavis4 ,these fungi completely destroy the grain of corn in which they form1 and propagate in the most rapid manner2 the ergot is moreover a dangerous poison to those who eat the bread made of rye infected by it4 ,the truffle is a kind of underground fungus1 and is esteemed a dainty4 ,mushrooms are also fungi1 and several species are sufficiently wholesome2 these are the field mushroom and the fairy-ring mushroom4 ,illustration3 ,fig4 #hbb4--;a a1 ,mould from an old bone2 b1 ,mould from jam4 ,any organic substance will shortly become covered with this 8mould0 or mildew4 ,the air is so full of the germs of animal and vegetable life that1 as it penetrates everywhere1 the smallest supply must contain some germs2 and these1 under a powerful microscope1 present most beautiful forms and colours4 ,we annex 7fig4 #hbb7 some of these forms highly magnified4 ,they are deposited by the air1 and the substance into which they happen to fall determines the kind of life which is to inhabit it4 ,a few of these spores only come to maturity4 ,we again take the liberty to quote ,dr4 ,carpenter on this subject4 ,he says3-- 8,there are scarcely any microscopic objects more beautiful than some of those forms of mould or mildew which are so commonly found growing upon the surface of jams and preserves1 especially when they are viewed with a low magnifying power and by reflected light2 for they present themselves as a forest of stems and branches of extremely varied and elegant forms1 loaded with fruit of singular delicacy of conformation1 all glistening brightly on a dark ground4 8,the universality of the appearance of these simple forms of fungi upon all spots favourable to their development1 has given rise to the belief that they are spontaneously produced by decaying substances1 but there is no occasion for this mode of accounting for it1 since the extraordinary means adopted by nature for the production and diffusion of the germs of these plants adequately suffices to explain the facts of the case4 8,the number of sporules which any one fungus may develop is almost incalculable2 a single individual of the 8puff-ball0 tribe has been computed to send forth no fewer than ten millions4 ,and their minuteness is such that they are scattered through the air in the finest possible dust1 so that it is difficult to conceive of a place from which they should be excluded40 ,illustration3 ,fig4 #hbc4--;,eatable mushroom 7,agaricus campestris74 ,illustration3 ,fig4 #hbd4--,seeds with pappi4 ,pure water exposed to the air does not afford nourishment to the germs which fall into it1 till a sufficient number of them shall have been deposited to form a food for those which come after them2 but if we mix with the water any soluble vegetable or animal matter1 in a short time the microscope will detect the growth of the germs that are being deposited1 for where nourishment is1 there only can they be developed4 ,these germs are capable of existing for an indefinite period1 either floating in the water1 or blown about by the air1 and have been detected hundreds of miles from land2 the rigging and sails of ships far away from shore are often covered with what sailors suppose to be sand blown from the land1 but which are organic substances1 either vegetable or animal4 ,according to ,humboldt1 the ,red ,sea has derived its name from the fact that at certain seasons the surface of the water has a reddish appearance1 and this 7as he says7 he was fortunate enough to observe1 which colour he found to be due to myriads of red fungi1 which had formed on the surface4 ,the seeds of some plants are furnished with minute wings or plumes1 which cause them to be borne on the air or floated on the water 7fig4 #hbd71 to fertilise some barren spot1 perhaps a coral reef1 which has at length reached the surface of the water1 and which ascends no higher1 for the little creatures which built it are aquatic1 and cannot live exposed to the air2 this coral reef now becomes a receptacle for seaweed and fungi1 which float on the surface of the ocean are washed on to the reef1 die1 decay1 and leave behind a thin layer of mould1 which process being repeated again and again1 forms an elevated edge to the reef1 enclosing a lake1 or 8lagoon0 as it is called1 the waters of which evaporate1 and the space is filled up in the same way as the edge was formed1 together with the excrements of birds1 etc41 forming layer after layer of mould1 and the surface becomes fit for the growth of larger seeds1 as the cocoa-nut1 banana1 etc41 which are drifted on to it by the waves2 in this way a coral reef becomes an island fit to be inhabited by man and other animals4 ,it is impossible for any person not accustomed to observe the manner of the propagation of the fungi1 to understand a written description1 for the fructification of these plants are very varied in the manner of the development of the spores4 ,they are not generally hurtful1 but much caution should be observed in the matter of the mushroom1 which may be distinguished by the pale pink and black of the under part4 ,there are many poisonous fungi1 but the greater number are harmless1 though they are not intended for food4 ,they simply clear away the decaying growths1 and act as safety-valves to ,nature by carrying away what is not required1 to give it to the air again to be renewed into life4 ,the vegetable kingdom forms the link between the minerals and the animals4 ,the vegetable derives food and nourishment from water1 carbonic acid1 and ammonia1 which are1 as we already know1 made up of certain elements1 and thus supply us all with food4 ,they give out oxygen for the use of animals1 and are thus1 in another sense1 the source of life4 ,the growth of a plant is very interesting1 and we may conclude by following it4 ,the seed is sown1 and the cells of the 8cellular tissue0 become developed1 passing some upwards1 some downwards1 to form a radicle or plumule1 as explained4 ,the latter carries up the cotyledon1 which begins to decompose carbonic acid from the atmosphere1 and fixing the carbon as woody fibre4 ,the leaves are then formed and more fibres1 and so on for every leaf2 thus the number of woody fibres which form the trunk of a tree is in proportion to the number of leaves which that tree has borne1 from which we come to the conclusion that the size of the trunk of a tree is the sum of all its branches4 ,while all this is going on1 the cellular tissue of the downward part or radicle also becomes developed and divides out into roots1 on the surface and at the extremities of which are minute cellular bodies called 8spongioles0 7from their power of absorbing moisture71 which take up the fluid of the earth which surrounds them2 this moisture ascends through the vessels of the plant till it arrives at the surface of the leaves1 where it is exposed to the action of light and sunshine4 ,the ascent of the moisture of the earth was first correctly explained by ,du ,trochet1 and is owing to a peculiar power which he discovered1 and which is called 8,endosmose02 this consists in the tendency which a fluid has to penetrate a membrane on the other side of which is a fluid of greater density than itself4 ,this may be seen by the following experiment3 obtain a piece of glass tubing about a foot long1 having the end blown out into the form of a bell1 as in fig4 #hbe1 tie a piece of bladder over the expanded end and fill it partly with syrup or gum-water1 so that this shall rise in the stalk about an inch2 place this in a glass of water with the bladder downwards1 and the fluid will be seen slowly to rise in the stalk1 so that in perhaps an hour it will rise to the top4 ,this apparatus resembles one of the spongioles at the extremity of the fibre of a root4 ,illustration3 ,fig4 #hbe4--;,endosmose4 ,the rain falling through the air carries with it a certain amount of carbonic acid and ammonia1 which the air always contains1 and it is the whole source of the nitrogen which forms a very important part of the bodies of plants and animals4 ,when the rain arrives at the surface of the earth1 it sinks down into it and carries with it all soluble vegetable or animal matter which it meets with1 together with any soluble earthy matter which may exist in the soil2 this forms the sap of the tree4 ,when it arrives at the surface of the leaf1 the watery part of it combines with the carbonic acid of the air 7through the influence of light71 and appropriating its carbon1 gives out the oxygen2 this is the true respiration of plants1 and is exactly the reverse of what takes place during the respiration of animals1 in which case oxygen is absorbed and carbonic acid given off4 ,the carbon thus retained by the plant combines with the elements of the water to form the solid green substance called chlorophyl1 which is the basis of all the tissues of the plant2 the ammonia is also decomposed1 and its nitrogen combining with the oxygen and hydrogen of the water1 and the carbon of the carbonic acid forms those compounds which constitute the most nourishing parts of vegetables1 such as albumen1 gluten1 etc41 and of which all the animal tissues are built up1 for the production of these organic substances takes place in the vegetable only1 animals simply appropriating them for their food4 ,the sap which reaches the leaf is not all converted into chlorophyl1 but also into those peculiar juices which are found in plants1 some of which contain sugar1 some gum1 others 7as the pine tribe7 turpentine1 and in the laurel tribe camphor1 all of which are substances containing much carbon2 moreover the solid wood and bark are deposited from these juices as they descend from the leaf after having been acted on by light 7or the actinic power associated with it74 ,now1 as the water1 ammonia1 and carbonic acid which descend with the rain are from the air1 and as the vegetable is formed wholly by their absorption1 it may be fairly said that the vegetable kingdom 7and therefore the animal7 feeds upon the air1 and that the trees do not grow out of the earth1 but into it4 ,,classification ,,of ,,plants4 ,for the groundwork of the system of classification which universally obtains at present1 we are indebted to ,linnus1 a ,swede1 born in #agjg4 ,in his classification of plants1 ,linnus followed two different methods4 ,in the one1 he based his division of plants in classes and orders1 upon certain peculiarities in the floral organs4 ,this system1 being thus founded on characters taken from certain parts of the plant only1 without reference to others1 and having something artificial in it1 has for that reason been termed the artificial system1 but it is now more generally known as the ,linnan system4 ,in the other method1 he arranged the plants according to certain general resemblances and affinities1 in natural orders or families4 ,this system1 which is known as the natural system1 has subsequently been much improved4 ,we use the term species1 to designate a number of individual plants1 which1 in all essential and unvarying characters1 resemble each other more closely than they do any other plant2 the term genus or kind1 to designate an assemblage of nearly allied species1 agreeing with one another in general structure and appearance more closely than they do with any other species4 ,here1 too1 it must be obvious1 that while all parts of the plant may furnish specific characters1 the character of the genera are taken exclusively from the parts of fructification4 ,in the name of a plant both the genus and the species are given4 ,the name designating the genus is called the generic name of the plant1 the one designating the species1 the specific or trivial name4 ,thus1 for instance1 we have the genus ,viola1 which includes the species ,viola odorata1 sweet violet2 ,viola canina1 dog violet2 ,viola tricolor1 heart's-ease4 ,it is necessary to give the ,latin names of plants1 as the common name differs1 not only in different countries1 but even in different parts of the same country4 ,an assemblage or group of allied genera1 agreeing in their general characters1 though differing in their special conformation1 is called an order or family of plants4 ,the sunflower1 the daisy1 the aster1 and the dahlia1 are1 for example1 plants of different genera1 but which1 all of them1 belong to the same order or family4 ,all plants are divided into three primary classes--viz41 ,dicotyledons1 ,monocotyledons1 and ,acotyledons1 as has been stated already4 ,a proper degree of familiarity with the systematic classification of plants is of the very highest importance to the student4 ,a successful pursuit of this branch of the botanical science presupposes a thorough knowledge of the structure and physiology of plants1 and requires1 moreover1 the aid of attentive observation1 and also some diligence in collecting and arranging plants4 ,,the ,,artificial ,,or ,,linn,,an ,,system ,,of ,,classification4 ,in this system plants are divided into twenty-four classes2 twenty-three of these contain the ,dicotyledons and ,monocotyledons indiscriminately2 the twenty-fourth class contains the ,acotyledons4 ,the first twenty-three classes are founded on the number1 position1 relative lengths1 and connection of the stamens4 ,the twenty-fourth comprises the plants with inconspicuous flowers4 ,every class is subdivided again into several orders4 ,this division depends1 in the first thirteen classes1 on the number of the styles2 in classes ,,xiv4 and ,,xv4 on the nature of the fruit2 in classes ,,xvi4 to ,,xviii4 and ,,xx4 to ,,xxii4 on the number of stamens2 in classes ,,xix4 and ,,xxiii4 on the perfection of the flower4 ,in class ,,xxiv4 the orders are formed according to natural affinities4 ,,tabular ,,view ,,of ,,the ,,linn,,an ,,system ,,of ,,classification4 ,a4--,,flowers ,,present 7,phanerogamia74 ,i4 ,stamens and pistil in every flower 7hermaphrodite74 #a4 ,stamens free4 a4 ,stamens of equal length1 or not differing in definite proportions4 ,number of ,stamens4 #a ,class #a4 ,monandria4 #b 0 #b4 ,diandria4 #c 0 #c4 ,triandria4 #d 0 #d4 ,tetrandria4 #e 0 #e4 ,pentandria4 #f 0 #f4 ,hexandria4 #g 0 #g4 ,heptandria4 #h 0 #h4 ,octandria4 #i 0 #i4 ,enneandria4 #aj 0 #aj4 ,decandria4 #aa-ai 0 #aa4 ,dodecandria4 #bj or inserted on calyx 0 #ab4 ,icosandria4 more 0 receptacle 0 #ac4 ,polyandria4 b4 ,stamens of different lengths1 two long and two short 0 #ad4 ,didynamia4 four long and two short 0 #ae4 ,tetradynamia #b4 ,stamens united by filaments in one bundle 0 #af4 ,monadelphia4 0 0 in two bundles 0 #ag4 ,diadelphia4 0 0 in more than two bundles 0 #ah4 ,polyadelphia4 0 by anthers 7compound flowers7 0 #ai4 ,syngenesia4 0 with pistil on a column 0 #bj4 ,gynandria4 ,,ii4 ,stamens and pistil in different flowers 7unisexual7 on the same plant 0 #ba4 ,moncia4 on different plants 0 #bb4 ,dicia4 ,,iii4 ,stamens and pistil in the same or in different flowers1 on the same or on different plants 0 #bc4 ,polygamia4 ,b4--,,flowers ,,absent 0 #bd4 ,cryptogamia ,,tabular ,,view ,,of ,,classes ,,and ,,orders4 ---------------------------------------- ---------------------------- ,classes4 ,orders4 ,examples4 ---------------------------------------- ---------------------------- ,i4--,,monandria ,monogynia one style ,hippuris4 ,one stamen4 ,digynia two styles ,callitriche4 ,,ii4--,,diandria ,monogynia one style ,syringa4 ,two stamens4 ,digynia two styles ,anthoxanthum4 ,trigynia three do4 ,,iii4--,,triandria ,monogynia one style ,iris4 ,three stamens4 ,digynia two styles ,hordeum4 ,trigynia three do4 ,holosteum4 ,,iv4--,,tetrandria ,monogynia one style ,scabiosa4 ,four stamens4 ,digynia two styles ,gentiana4 ,trigynia three do4 ,v4--,,pentandria ,monogynia one style ,borago4 ,five stamens4 ,digynia two styles ,fniculum4 ,trigynia three do4 ,sambucus4 ,tetragynia four do4 ,parnassia4 ,pentagynia five do4 ,linum4 ,polygynia six and more do4 ,myosurus4 ,,vi4--,,hexandria ,monogynia one style ,lilium4 ,six stamens4 ,digynia two styles ,oxyria4 ,trigynia three do4 ,rumex4 ,tetragynia four do4 ,alisma4 ,polygynia many do4 ,,vii4--,,heptandria ,monogynia one style ,trientalis4 ,seven stamens4 ,digynia two styles ,trigynia three do4 ,heptagynia seven do4 ,,viii4--,,octandria ,monogynia one style ,daphne4 ,eight stamens4 ,digynia two styles ,chrysosplenium4 ,trigynia three do4 ,polygonum4 ,tetragynia four do4 ,paris4 ,,ix4--,,enneandria ,monogynia one style ,nine stamens4 ,trigynia three styles ,hexagynia six do4 ,butomus4 ,x4--,,decandria ,monogynia one style ,pyrola4 ,ten stamens4 ,digynia two styles ,dianthus4 ,trigynia three do4 ,silene4 ,pentagynia five do4 ,lychnis4 ,decagynia ten do4 ,,xi4--,,dodecandria ,monogynia one style ,lythrum4 ,twelve to nineteen ,digynia two styles ,agrimonia4 stamens4 ,trigynia three do4 ,reseda4 ,pentagynia five do4 ,dodecagynia twelve do4 ,sempervivum4 ,,xii4--,,icosandria ,monogynia one style ,prunus4 ,twenty or more ,digynia two styles ,cratgus4 stamens inserted ,trigynia three do4 ,sorbus4 on the calyx4 ,pentagynia five do4 ,polygynia many do4 ,rosa4 ,,xiii4--,,polyandria ,monogynia one style ,papaver4 ,many stamens ,digynia two styles ,ponia4 inserted on the ,trigynia three do4 ,aconitum4 receptacle4 ,tetragynia four do4 ,pentagynia five do4 ,nigella4 ,hexagynia six do4 ,polygynia many do4 ,ranunculus4 ,,xiv4--,,didynamia ,gymnospermia four naked seeds ,lavandula4 ,two long and two ,angiospermia seeds in capsules ,linaria4 short stamens4 ,labiate and ,personate ,flowers4 ,,xv4--,,tetradynamia ,siliculosa broad and short pod ,capsella4 ,four long and two 7silicula71 and short stamens4 style ,cruciferous ,siliquosa long pod 7siliqua72 ,brassica4 ,flowers4 stigma sessile ,,xvi4--,,monadelphia ,pentandria five stamens ,erodium4 ,stamens united in ,enneandria nine do4 one bundle4 ,decandria ten do4 ,geranium4 ,dodecandria #aa-ai do4 ,malva4 ,polyandria many do4 ,,xvii4--,,diadelphia ,pentandria five stamens ,stamens united in 7two above and three below47 two bundles 7one ,hexandria six stamens ,fumaria4 generally 7three right1 three left1 or containing nine three above and three below47 enclosed in a ,octandria eight stamens ,polygala4 tube1 and one 7four above and four below1 free74 all united at the base47 ,papilionace4 ,decandria ten stamens ,pisum1 ,trifolium 7one above and nine below1 ,genista4 united in a cleft tube surrounding the ovary47 ,,xviii4--,,polyadelphia ,pentandria five bundles ,stamens united in 7each bundle bearing five more than two anthers #be stamens47 bundles4 ,dodecandria twelve stamens 7each bundle bearing three anthers #cf stamens47 ,icosandria many stamens in ,citrus4 bundles1 inserted on the calyx 7#bj stamens in bundles bearing an unequal number of anthers47 ,polyandria many stamens in ,hypericum4 three1 five1 and nine bundles1 inserted on the receptacle4 ,,xix4--,,syngenesia ,polygamia qualia1 florets all ,lactuca4 ,five stamens1 hermaphrodite4 filaments free1 ,polygamia superflua1 florets of ,aster4 anthers united1 the disc hermaphrodite1 those flower of the ray pistilliferous and monopetalous1 fertile4 florets united on ,polygamia frustranea1 florets ,helianthus4 a disc4 ,composit4 of the disc hermaphrodite1 ,in the first four those of the ray neutral4 orders only a ,polygamia necessaria1 florets ,calendula4 common calyx4 of the disc staminiferous1 of the ray pistilliferous4 ,polygamia segregata1 a common ,echinops4 calyx including all the florets1 and a separate involucre for each4 ,monogamia1 anthers united1 flowers not compound4 ,,xx4--,,gynandria ,diandria two anthers ,orchis4 ,stamens and ,triandria three do4 pistil united4 ,tetrandria four do4 ,pentandria five do4 ,hexandria six do4 ,aristolochia4 ,decandria ten do4 ,dodecandria #aa-ai do4 ,polyandria twenty or more do4 ,,xxi4--,,mon,,cia ,monandria one stamen ,arum4 ,stamens and pistils ,diandria two stamens ,lemna4 in different ,triandria three do4 ,carex4 flowers on the ,tetrandria four do4 ,urtica4 same plant4 ,pentandria five do4 ,amaranthus4 ,hexandria six do4 ,heptandria seven do4 ,polyandria more than seven do4 ,quercus4 ,monadelphia stamens united ,pinus4 ,syngenesia stamens united by their anthers4 ,gynandria stamens and styles united ,,xxii4--,,di,,cia ,monandria one stamen ,salix4 ,stamens and pistils ,diandria two stamens in different ,triandria three do4 ,ficus4 flowers on ,tetrandria four do4 ,viscum4 different plants4 ,pentandria five do4 ,cannabis4 ,hexandria six do4 ,loranthus4 ,octandria eight do4 ,populus4 ,enneandria nine do4 ,laurus4 ,decandria ten do4 ,dodecandria #aa-ai do4 ,stratiotes4 ,polyandria many do4 ,monadelphia stamens united in ,juniperus4 one bundle4 ,syngenesia stamens united by the anthers4 ,gynandria stamens and styles united4 ,,xxiii4--,,polygamia ,moncia1 hermaphrodite1 ,acer4 ,stamens and pistil staminiferous1 and in the same1 or in pistilliferous flowers on the different flowers1 same plant4 on the same or on ,dicia on two plants ,fraxinus4 different plants4 ,tricia on three plants ,,xxiv4--,,cryptogamia ,filices ,ferns ,aspidium4 ,organs of ,musci ,mosses ,spagnum4 fructification ,hepatic ,liverworts ,marchantia4 concealed 7flowers ,lichenes ,lichens ,cetraria4 inconspicuous74 ,alg ,seaweeds ,fucus4 ,fungi ,mushrooms ,agaricus4 ---------------------------------------- ---------------------------- ,with all its imperfections1 the artificial system has this advantage1 that the character on which it is founded is sufficiently conspicuous 7that is1 of course1 with the plants in full flower7 to render it generally easy to ascertain the class and order of a plant4 ,at all events1 it may serve as a useful artificial key1 and as such may be combined advantageously with the natural system4 #aad4 ,,natural ,,system 7,,jussieu',s74 ,classes4 ,i4 ,acotyledons #ast ,class4 ,,ii4 ,monocotyledons ,mono-hypogyn 7stamens hypogynous7 #bnd 0 ,mono-perigyn 7stamens perigynous7 #crd 0 ,mono-epigyn 7stamens epigynous7 #dth 0 ,,iii4 ,dicotyledons4 ,monoclines1 flowers hermaphrodite4 ,epistamine 7stamens epigynous7 #eth 0 ,apetal 7no petals7 ,peristamine 7stamens perigynous7 #fth 0 ,hypostamine 7stamens hypogynous7 #gth 0 ,monopetal 7petals united7 ,hypocoroll 7corolla hypogynous7 #hth 0 ,pericoroll 7corolla perigynous7 #ith 0 ,epicoroll 7corolla epigynous7 ,synanther 7anthers united7 #ajth 0 ,chorisanther 7anthers free7 #aath 0 ,polypetal 7petals distinct7 ,epipetal 7petals epigynous7 #abth 0 ,peripetal 7petals perigynous7 #acth 0 ,hypopetal 7petals hypogynous7 #adth 0 ,diclines1 flowers unisexual1 or without a perianth4 #aeth 0 ,this system1 being likewise founded partly on individual organs1 is also1 to a certain extent1 artificial2 and1 strictly speaking1 every natural method of botanic classification must partake more or less of an artificial character1 as many orders of plants merge so insensibly into others that their respective limits cannot be accurately or rigorously defined4 ,,footnotes3 #cg ,carpenter on the ,microscope4 ,,chapter ,,liv4 ,,zoology4 ,,classification ,,of ,,animals--,,vertebrates ,,and ,,invertebrates--,,protozoa--,,hydrozoa- -,,actinozoa4 ,zoology treats of life--of organized beings which are capable of voluntary motion4 ,plants exist1 animals live and move4 ,both are organic beings1 but the latter possess the faculty of will and spontaneous movement4 ,the animal can leave a place and enjoy other surroundings1 the plant cannot4 ,we have already crossed the borderland which connects the plant and the animal4 ,we have seen plants almost animals4 ,we could commence this section with animals which are almost plants1 so closely do the divisions approach each other4 ,,zoology is the science of the knowledge of animals as ,,botany is of the knowledge of plants4 ,where there is vegetation there are animals1 not quadrupeds or bipeds necessarily1 but numbers of small1 it may be invisible1 creatures which exist upon the vegetable kingdom--the alg and minute creations of globules and cells1 the infusoria already mentioned1 the corals1 etc4 ,and in the 8protozoa10 or first specimens of animal life1 we have a similarity to the vegetable kingdom2 we then get by gradual steps to other more perfect beings1 each after his kind1 till we arrive at the most perfect animal--,,man4 ,illustration3 ,fig4 #hbf4--;,echinus1 or ,sea-,urchin4 ,animals are divided into two families1 the ,,invertebrate and the ,,vertebrate4 ,the former has no spine nor skeleton2 the latter has both4 ,these again are divided into sub-families1 classes1 and orders1 as follows4 ,man is an animal--but what is an animal8 ,we can scarcely tell in a few words4 ,linnus defined the difference between the animal and the plant1 for the former1 said he1 live1 grow1 and feel1 while the latter live and grow4 ,we have protozoa in the animal kingdom consisting of a single cell or blood corpuscle1 some others without mouths or digestive organs1 some have no head2 some1 as in the tape-worm1 only a so-called head1 with suckers or attachments1 after which it develops joints1 which are at first imperfect1 but gradually mature as they are pushed farther away by new-issuing joints4 ,animals1 therefore1 do not all possess organs1 nor is there any common organ by which all animals can be classed4 ,the indispensable in one is absent in another1 and while our mouths and digestive apparatus are all important1 in other animals suckers and no digestive apparatus at all is quite sufficient4 ,some have one mouth1 some several2 some have mouths and a proboscis to assist them1 some only the trunk and no mouth--so called--at all1 as in some insects4 ,illustration3 ,fig4 #hbg4--,polypidom4 ,the organisms which could not be distinguished from vegetables were termed zoophytes1 or plant animals1 and1 were space available1 a comparison might be instituted between the extremes of growth of the animals and plants1 from the largest whales to the tiny microscopic protozoa1 and from the mould upon jam to the gigantic trees of ,california1 one leaf of which it is said will shelter twenty men from rain4 ,cuvier spent many years in perfecting his systematic arrangements of animals1 and this classification1 though many rearrangements have been made as modern discovery progressed1 may be regarded as the fundamental system of all4 ,professor ,agassiz adopted it with modifications4 ,professor ,nicholson has made a somewhat different arrangement1 but essentially there will be found but slight difference between them4 ,we append both these arrangements for comparison3-- ,,agassiz-,,cuvier4 ,,invertebrata4 ,,branch ,i4--,,radiata4 ,class ,i4--,polypi #b orders ,including actinoids and halcyonoids4 0 ,,ii4--,acalephs #c 0 hydroids1 discophor1 ctenophor4 0 ,,iii4--,echinoderms #d 0 crinoids1 asteroids1 echinoids4 ,,branch ,,ii4--,,mollusca4 ,class ,i4--,acephala #d orders bryoza1 brachiopods1 tunicata1 and lamellibranchiata4 0 ,,ii4--,gasteropoda #c 0 pipteropoda1 heteropoda1 and gasteropoda 7proper74 0 ,,iii4--,cephalopoda #b 0 tetrabranchiata1 and dibranchiata4 ,,branch ,,iii4--,,articulata4 ,class ,i4--,worms #c orders trematods 7including leeches1 etc471 nematoids1 and annelides4 0 ,,ii4--,crustacea #d 0 rotifera1 crinopods1 tetradecapods1 and decapods4 0 ,,iii4--,insects #c 0 myriapods1 arachnoids1 and insects proper4 ,,branch ,,iv4--,,vertebrata4 ,class ,i4--,myzontes #b orders myxinoids and cyclostomes4 0 ,,ii4--,fishes proper4 0 ,,iii4--,ganoids #c 0 clacanths1 axipenseroids1 and sauroids4 0 ,,iv4--,selachiens #c 0 chimr1 galeodes1 and batides4 0 ,v4--,amphibians #c 0 ccili1 ichthyodi1 and anoura4 0 ,,vi4--,reptiles #d 0 serpents1 saurii1 rhizodontes1 and testudinata4 0 ,,vii4--,birds #d 0 natatores1 grall1 rasores1 and incessores4 0 ,,viii4--,mammalia #c 0 marsupiaia1 herbivora1 and carnivora4 ,in the vertebrated animals the blood is red in consequence of the minute cells 7corpuscles7 which contain the colouring matter4 ,in invertebrate animals these red cells are absent1 and so the animals are white-blooded4 ,some animals1 again1 are cold-blooded like the fish2 birds and mammalia have warm blood4 ,it is worthy of remark that the higher we advance in the scale the fewer the offspring of the animal4 ,the animalcules multiply at the rate of many billions a day1 and even one codfish is stated to contain more than nine millions of eggs4 ,a mackerel will produce #ejj1jjj2 and so on1 as we rise1 we find mammals with seldom more than ten young at a time1 down to one single offspring4 ,we could fill pages with the account of the differences existing between animals created for such different purposes and fitted to inhabit different climates1 their mode of feeding and catching prey4 ,the manner of bringing forth and rearing the young1 and the temperament and temper of the animal creation would fill a volume1 but we cannot now stay to examine these various characteristics4 ,the following is the arrangement now usually adopted3-- ,,nicholson4 ,,invertebrates4 ,,protozoa4 ,the lowest forms of animal life--microscopic animals4 ,gregarinida ,cell forms2 worm-like4 ,rhizopoda ,ameb1 foraminifera1 radiolaria1 sponges4 ,infusoria4 ,suctoria1 ciliata1 etc4 ,c,,lenterata 7,,the ,,old ,,radiata74 ,,hydrozoa4 ,intermediary1 having a mouth and receptacle separated by no alimentary canal4 ,polypes and ,zoophytes1 ,actinozoa4 ,medus1 millipores1 corals1 sea-anemones1 tubipora1 siphonophera1 etc4 ,,echinodermata4 ,star-fishes1 sea-urchins1 sea-cucumbers1 and crinoids4 ,,annulosa4 ,entozoa ,tape-worms1 etc4 ,rotifera ,wheel-,animalcul4 ,annelida ,worms1 leeches4 ,cerripida ,barnacles4 ,crustacea ,shell-fish4 ,insecta ,various insects4 ,arachnida ,spiders1 scorpions1 etc4 ,,mollusca4 ,,mulloscoida--,,polyzoa4 ,acephala of headless pupa4 ,tunicata ,brachiopoda ,lamellibranchiata 7bivalves74 ,encephala with head4 ,pteropoda4 ,gasteropoda 7univalves74 ,cephalopoda1 cuttle-fish1 etc4 ,,vertebrata4 ,,ichthyopsida4 ,class ,i4--,fishes ,various orders4 0 ,,ii4--,amphibia ,frogs1 toads1 salamanders1 etc4 ,,sauropsida4 0 ,,iii4--,reptilia ,tortoises1 smaller snakes1 lizards1 etc4 0 ,,iv4--,birds ,various orders4 ,,mammalia4 ,class ,i4--,non-,placental ,marsupials4 0 ,,ii4--,placental ,edentata1 cetacea1 ungulata1 quadrumana1 bimana1 etc4 ,we will adopt the latter order as being the more modern1 and endeavour to make the various classes of the invertebrates clear to the mind1 if we cannot present them to the vision1 of the reader4 ,in our sketch of ,botany we remarked upon the similarity existing between the cells of plants and animals1 and although there are1 of course1 differences1 there are many points of resemblance in these cells4 ,plants have their lowest representatives called ,protophytes4 ,animals which correspond to this class are termed ,protozoa1 from the ,greek1 proton1 first1 and zon1 animal4 ,the former are1 as already mentioned1 seen amongst the alg1 consisting of simple cells1 and protozoa cannot easily be distinguished from them except in the matter of nutriment1 for some protozoa have no mouth except in the infusoria class4 ,the cells are very much alike1 and ,dr4 ,carpenter sums them up briefly as follows3-- 8,the animal cell1 in its most complete form1 is comparable in most parts of its structure to that of the plant1 but differs from it in the entire absence of the #8cellulose wall' or of anything that represents it1 the cell-contents being enclosed in only a single limitary membrane1 the chemical composition of which1 being albuminous1 indicates its correspondence with the primordial utricle4 ,in its young state it seems always to contain a semi-fluid plasma1 which is essentially the same as the protoplasm of the plant1 save that it does not include chlorophyl granules1 and this may either continue to occupy its cavity 7which is the case in cells whose entire energy is directed to growth and multiplication71 or may give place1 either wholly or in part1 to the special product which it may be the function of the cell to prepare4 ,like the vegetable cell1 that of animals very commonly multiplies by duplicative subdivision1 it also 7especially among protozoa7 may give origin to new cells by the breaking up of its contents into several particles40 ,illustration3 ,fig4 #hbh4--;,animalcul found in stagnant water4 ,a1 ,cyclops ,quadracornis4 ,b1 ,anguillula4 ,fluviatillis4 ,c1 ,actinophrys4 ,sol4 ,d1 ,coleps ,hirtus4 ,e1 ,vorticella4 ,f1 ,ambba princeps4 ,g1 ,acineta mystacina4 ,h1 ,oxytrycha4 ,i1 ,triophthalamus dorsalis4 ,j1 ,polyarthra4 ,the protozoa are microscopic creatures consisting of one or more cells1 and are infinitely little1 thousands existing in a drop of water4 ,they have no distinction of sexes1 and their generation takes place by subdivision or blending of cells4 ,the infusoria are the highest of the protozoa1 and were formerly included amongst the radiata4 ,their numbers are infinite1 and in a drop of water 7see fig4 #hbh7 some very interesting specimens will be found4 ,these infusoria are merely sarcode1 or a jelly-like substance1 and some have cilia1 or hairy appendages1 with which they agitate the water and cause a kind of current which brings them food4 ,it is this partaking of food which has served to divide the lowest animal from the lowest vegetable creations4 ,there is no progressive increase of development from the lowest plant to the highest animal4 ,the animal begins by himself1 as it were1 as the plant1 and both grow up in different directions4 ,the protozoa exist upon organic substances1 while plants absorb inorganic substances and assimilate them4 ,the ,gregarinid are very tiny cells1 and though microscopically minute1 they sometimes develop into worm-like or elongated oval bodies4 ,they inhabit the intestines of crustacea1 worms1 and cockroaches1 as well as of higher animals4 ,they are capable of certain motion1 but are not furnished even with the 8false feet0 7pseudo podia7 of the rhizopoda1 the next animal in these very low scales of creation4 ,of the ,rhizopoda the ,,ameb are very interesting1 and we find them in our veins as well as in the stagnant green water of the pond4 ,they are simply sarcode or jelly1 and1 as the name implies1 the ameb can change their appearance 7amoibos1 changing74 ,they possess a kind of crawling1 progressive motion1 and under the microscope will be perceived to develop a tiny bud1 as it were1 which is the 8false foot0 that assists its progress4 ,these ameb are in our blood moving about1 and are always altering their form1 and when warm they move more quickly in the red blood corpuscles or cells1 but excessive heat will kill them4 ,these curious creatures feed by the foot they protrude2 and by drawing in the 8process0 as it is termed1 they can collect within themselves the nourishment they require4 ,of course they have no mouth1 and if we can conceive a creature of this kind which thrusts out from a jelly-bag a tiny lump1 and pulls it in again at any time and place it likes1 we have an idea of an ameba4 ,the pond ameba is somewhat different from the others1 inasmuch as it possesses an outer and inner portion or layer which are different in density4 ,there is what is termed a contractile vesicle which 8beats0 as a heart beats1 but this is very primitive4 ,there is really no structure whatever in these rhizopoda1 and1 as we have seen1 their shape is always undergoing change4 ,the outer and inner layers of the ameb are called 8the ectosarc0 and 8endosarc0 respectively2 the latter contains the darker portion--the nucleus4 ,the ,foraminifera have already been mentioned in the chapters on ,geology4 ,we find these minute creatures must have had a great deal to do with the building up of rocks1 as they have the power to make tiny coverings for themselves1 which have been built into rocks by the addition of sandy particles1 and consolidated by pressure4 ,here we have a most wonderful instance of the tiniest creatures producing the greatest masses of the earth4 ,the body is merely sarcode1 the shell is carbonate of lime4 ,the foraminifera produce false feet in abundance1 which surround the cell like fine hairs or rays4 ,they live in the sea1 and when they die the shells descend upon the ocean floor1 where they undergo many changes and become converted into rock4 ,the ooze of the great oceans is composed of these shells1 and is practically a chalky deposit2 the shells are being built up as in former ages with the curious nummulites of the ,eocene formation1 which are amongst the most interesting of fossils4 ,,sponges4 ,we must go on at once to the ,sponges1 which form such an interesting subject as they are so familiar to us all4 ,sponge is not often regarded by the public as an animal1 and though perhaps authorities may not have yet concluded in what category they should be placed1 we may consider them here according to the list4 ,we find the spongida both in fresh and salt water1 and they have given rise to much discussion as to whether they should be classed as animals at all4 ,but that question having been finally settled1 we can proceed to examine a sponge in its native state1 and we shall find both skeleton and 8flesh40 ,the skeleton is hard and composed of needles of 8tiny0 texture4 ,the flesh is 8sarcode10 and the animal possesses no mouth1 but is full of holes 7pores7 and canals through which the water is continually distributed4 ,the outer layer of the sponge is formed of ultimate components of the living substance of the sponge 7like the ameb we have been considering74 ,each contains a nucleus1 and when joined together form the outer layer of the body4 ,beneath is a wide cavity communicating with the exterior by means of minute holes1 and filled with water4 ,the cavity separates the superficial layer from the deeper substance1 which is of the same character4 ,in the water passages of the sponge are cilia which induce a cement1 and the interior canals develop into chambers lined with sponge particles1 and the water carries particles to the sponge1 which represents a kind of sub-aqueous city1 where the people are arranged about the streets and roads in such a manner that each can easily appropriate his food from the water as it passes along4#ch ,illustration3 ,fig4 #hbi4--;,fragment of sponge 7magnified74 ,sponge1 then1 is a mass of living organisms--tiny living creatures capable of feeding and of movement1 resembling ameb or perhaps infusoria1 with cilia1 to enable them to obtain nourishment by a kind of inhalation or respiration4 ,they are reproductive by sexual and a-sexual processes which produce spongell4 ,the living sponge is a beautifully coloured animal1 and grows upon almost any solid foundation2 and in the autumn the parent sponge displays a number of yellow dots or 8gemmules10 which are the young4 ,these are soon cast off and left to shift for themselves1 and seek their fortunes1 helpless as they appear1 in the wide and stormy sea4 ,at last they find a resting-place1 and fix themselves for ever1 growing up and reproducing their species until they are carried off to be sold and used in civilized countries for domestic purposes4 ,we must leave these curious animalcul and glance at the ,,infusoria1 which constitute a higher branch1 but microscopic and universal1 and include those called ,flagellate1 ,ciliate1 and ,tentaculate4 ,the first have whip-like cilia1 or feelers1 or filaments1 which are ever in motion to cause a movement of the water and carry food to the animal4 ,you will find plenty of infusoria in any stagnant water1 and when placed under the microscope a mouth may be perceived1 but no stomach1 nor any apparent receptacle for food1 which appears to enter at once into the body substance4 ,the other kinds capture their food by seizure by the tentacles1 or by agitating the cilia1 like the flagellata1 and thus whipping the nourishment towards the mouth1 as children will draw in a toy boat to land by agitating the water in the given direction4 ,these cilia1 or hairs1 serve for organs of locomotion as well as of capture4 ,these creatures are called ,infusoria1 because they exist in vegetable 8infusions0 exposed to the atmosphere4 ,illustration3 ,fig4 #hcj4--,structure of polypidoms4 ,decaying vegetable or animal substances1 such as the leaves of trees1 grass1 a piece of flesh1 etc41 affused with water and exposed to air and warmth1 will speedily1 upon microscopic examination1 be found peopled with numbers of most active minute creatures of the most varied forms4 ,these animalcules are found also in the stagnant pools around our cities1 in the waters of rivers1 harbours1 and lakes1 and even in the ocean4 ,in reference to the origin of these animalcules1 the view was long entertained that they were generated spontaneously1 that the decaying vegetable and animal substances were decomposed and resolved into these simple beings4 ,more accurate experiments have shown1 however1 that the infusoria are produced from ova1 or germs1 which are probably carried about in the dried-up state1 in the form of minute particles of dust1#ci ready to develop themselves in any spot which may afford them the requisite moisture and nutriment4 ,in this respect they resemble the microscopic fungi1 whose germs are diffused in the same way4 ,when once they have obtained the means of development1 they multiply with incredible celerity4 ,if the decaying vegetable or animal substances be carefully excluded from contact with the air1 or if the air be heated before it is admitted to them1 no infusoria will appear4 ,they are rarely developed on mountains of a certain height1 where the atmosphere is free from foreign bodies4 ,though these animalcules are so exceedingly minute1 yet the forms exhibited by them are extremely various1 and some of them present also considerable variety in the forms assumed by the same individual under different circumstances4 ,in many species the soft body is enclosed in a firm integument1 strengthened by a deposit of siliceous matter2 these envelopes1 which are often preserved after the death of the animals1 are termed the shields1 and the animalcules encased in them are called loricated infusoria4 ,the remarkable discovery has been made that large distinct beds of former formations are entirely made up of the accumulated remains of these animalcules4 ,illustration3 ,fig4 #hca4--,volvox globator4 ,we arrive at the ,,hydrozoa after leaving the ,infusoria1 and find ourselves in the sea1 and far from land1 where it will be difficult for us to ascertain the characteristics of these interesting animals4 ,but fortunately we can obtain much nearer home1 and occasionally in a private aquarium1 a specimen of the hydrozoa which will serve our purpose1 as it has served before to introduce readers to the study of these water-polypes1 some of which are so like plants that they are frequently mistaken for them4 ,the hydrozoa present a 8definite histological structure10 says ,professor ,huxley2 8the body always exhibits a separation into at least two distinct layers of tissue1 an outer and an inner40 ,the ,hydras1 or fresh-water polypes1 which may be found in nearly every pond adhering to the duckweed1 appears like tubes1 and if touched will curl up into tiny knobs4 ,but if let alone they will adhere to a glass by their single foot1 or sucker1 which can be moved at pleasure4 ,illustration3 ,fig4 #hcb4--,the hydra4 ,the foot1 or sucker1 is continued to a slender cylindrical stalk1 from the end of which radiate a number of tentacles1 or 8feelers10 growing around the mouth1 and serving to convey or attract food to the animal which is1 so to speak1 all stomach4 ,there is no breathing apparatus1 and what food it cannot digest is expelled from the mouth4 ,the peculiarity which has given the hydra its name is1 that no matter into how many pieces you cut this polype1 the parts cut off will all develop into little polypes perfect as their parent4#dj ,but germination is carried on naturally by buds thrown out1 and cast 7by 8gemmation071 or by the ordinary sexual production of ova4 ,the outer and inner skins of the hydra are called the ectoderm and endoderm1 and the animal is quite capable of locomotion1 walking1 or rather moving1 backwards1 by raising and planting its sucker or foot1 and by swimming4 ,the prey is captured by the tentacles and by the darting out of tiny spears from the cells or 8thread cells0 which contain them on the surface of the body4 ,the well-known 8,portuguese man-of-war10 an ocean polype1 has these 8harpoons0 greatly developed1 and can inflict serious pain as of many stinging nettles2 the sensation is exceedingly painful1 and lasts some time4 ,the ,,medusid are known to the seaside visitor as the jelly-fish1 and the other ,acaleph1 the 8hidden-eyed0 medus1 include the ,portuguese man-of-war mentioned above1 and many other umbrella-like animals4 ,they have received the name of medus from ,medusa1 whose long1 snaky locks the tentacles of the animals are supposed to be like4 ,some of these 8floating umbrellas0 are very dangerous1 and will inflict severe stings upon any one in their vicinity4 ,the tentacles or filaments extend for a long distance1 and bathers should be cautious4 ,we have often watched them1 and they are beautiful to contemplate particularly at night1 and in ,kingstown ,harbour1 near ,dublin1 many exceedingly fine specimens have been obtained4 ,the pulsation of the 8umbrella0 or bell1 enables the animal to swim1 and the even undulations of this beautiful covering are apparently caused by nervous contractions4 ,the jelly-fish have no resemblance to 8fish10 and scarcely appear to exist2 they are of no use to man1 and when removed from the water dwindle by little and little to a tiny film and nothing more--they dissolve into air and water4 ,cases have been known and tales told of how farmers collected hundreds of these jelly-fish for manure1 and when the cart reached the field1 to the man's astonishment1 nothing was left but what appeared cobweb in the place of the load of fish4 ,illustration3 ,fig4 #hcc4--,medusa4 ,the ,cyclippe is a very common specimen1 and moves by means of its cilia2 ,cestum ,veneris--the zone or girdle of ,venus--is another curious example4 ,it appears like a glass ribbon about five inches wide and perhaps four or five feet long4 ,the cilia when in motion are very brilliant in colouring1 and the creature undulates through the water in a remarkable manner4 ,the luminosity of the medus is clearly perceived1 the so-called phosphorescence being due chiefly to the minute jelly-fish which abound near the surface of the sea4 ,it appears impossible1 for most1 at any rate1 if not all1 these medus to sink beneath the surface1 for they can be found in hundreds cast ashore1 melting away into film4 ,we might imagine that they would be provided with some means of sinking themselves1 but being apparently only air and water1 it is necessary for them to remain upon the surface to exist at all4 ,illustration3 ,fig4 #hcd4--,sea cucumber4 ,the term ,acaleph1 by which they are known1 means 8stinging0 fish or sea-nettles1 the ,greek word meaning nettle4 ,the ,,actinozoa comprise corals and the popular sea anemones 7actinid74 ,they resemble the hydrozoa in possessing tentacles1 and also the two inner and outer tissues of the body4 ,but they differ from the hydrozoa in their interior arrangement in the possession of a kind of stomach between the 8body cavity0 and the mouth which the hydrozoa do not possess4 ,the appearance of the sea anemone is well known4 ,it fixes itself by the flat base and hangs out its tentacles to obtain food4 ,when we touch an anemone with a stick we perceive how it contracts itself1 but there is no nervous system nor any respiration4 ,the reproduction of its species is carried on within1 not as in other animals1 like the hydra1 by exterior budding4 ,illustration3 ,fig4 #hce4--;,coral4 ,the corals belong to the same class as the sea anemones1 and are called zoanthid4 ,we have already in previous portions of this volume mentioned the 8coral0 building polypes1 but we may again describe them here4 ,we have the black coral or antipathid1 which live in masses and are united by a stem4 ,they grow upon this fleshy trunk and cover it in time 8just as a trunk of a tree is covered by the bark40 ,this stem is called a cnosarc1 which secretes the coral1 or skeleton4 ,the madrepores are the greatest producers of the coral of commerce4 ,illustration3 ,fig4 #hcf4--;,coral4 8,if we examine a simple coral of this group10 says ,professor ,nicholson1 8we find that we have to deal with an animal in all important respects identical with an ordinary sea anemone1 but having a more or less complicated skeleton developed in its interior40 ,this skeleton is the corallum1 and it is composed1 as most people are aware1 of calcareous matter deposited within the polype itself2 in the former case the development or formation is exterior to the polype4 ,a single polype will thus secrete a deposit1 and a colony of them produce a compound skeleton1 and as they throw out buds or young polypes1 the manufacture of skeletons goes on by secretion4 ,the ,tubipores are like pipes1 and the coral has been termed the 8organ-pipe40 ,it is formed cylindrically and joined externally4 ,as under ,,geology we have examined the question of coral reefs1 we need not here recapitulate the descriptions given in that section4 ,illustration3 ,fig4 #hcg4--;,coral4 ,doctor ,bariel writes of these animals as follows3--8,by far the greater part of the ,zoanthoid polypes1 as they grow1 deposit in the cellular substance of the flesh of their back an immense quantity of calcareous matter which enlarges as the animal increases in size1 and1 in fact1 fills up those portions of the substance of the animal1 which by the growth of new parts are no longer wanted for its nourishment1 and in this manner they form a hard and strong case1 amongst the folds of which they contract themselves so as to be protected from external injury1 and by the same means they form for themselves a permanent attachment which prevents their being tossed about by every wave of the element in which they live4 ,the stony substances so formed are called corals1 and their mode of formation causes them exactly to represent the animal which secretes them4 ,the upper surface is always furnished with radiating plates1 the remains of the calcareous particles which are deposited in the longitudinal folds of the stomach40 ,,footnotes3 #ch ,huxley4 8,classification of ,animals40 #ci ,that the presence of millions of such ova in the air should not be detected1 will appear very natural indeed1 if we reflect that the animalcules are only #a_/aejj to #a_/bjjj part of a line in diameter1 and that the ova are a thousand times smaller4 #dj ,hercules conquered the 8,hydra10 which is represented in mythology as capable of reproducing two heads for each one cut off by the warrior4 ,,chapter ,,lv4 ,,echinodermata--,,annulosa--,,entozoa-- ,,insecta4 ,,sea-,,urchins--,,star-,,fishes--,,feat hery ,,stars--,,sea-,,cucumbers--,,worms--,,l eeches--,,rotifers--,,tape ,,worms--,,insects4 ,the ,,echinodermata or spiny-skinned1 are most commonly represented by the sea-urchins and star-fishes of our coasts4 ,in some of the classes locomotion is performed by means of these spines or prickles1 which serve as legs4 ,in others1 movement is carried on by suckers and tubes as in the star-fishes1 these tubes being also the means whereby the animal obtains its food4 ,illustration3 ,fig4 #hch4--,sea-urchin 7echinus71 with and without spines4 ,they have a digestive system1 and possess a curiously horny skin even when spines are absent4 ,the mouth is in the centre4 ,we give an illustration of the sea-urchin1 and of a section of a spine1 which is a beautiful object when seen under the microscope1 for these spines can be made quite transparent when cut across and ground4 ,the shelly covering is porous1 and as the animal grows the shell is added to at the edges4 ,underneath will be found the mouth1 which has teeth fitted for devouring the small crustacea4 ,these sea-urchins abound1 and their porous shells may be picked up frequently after a storm4 ,the star-fishes are well known to all searchers amongst the rocks and those who study the shore1 and are often taken home for an aquarium4 ,they are very voracious1 however1 and when one is examined in a glass of sea-water1 the observer will detect many suckers protruding from each of the rays4 ,it is by means of these suckers1 which are put forth from innumerable little holes called 8ambulacral apertures10 that the star-fish makes his way up the rocks and along the ocean bed4 ,the stomach of the star-fish is extensive1 and situated in the centre of the rays wherein is a digestive apparatus4 ,the rays are composed of detached but beautifully fitted pieces1 so united as to be flexible1 and around the mouth and in strong frame-work4 ,the star-fish has no teeth1 but manages to dispose of a vast quantity of matter1 which if left alone would be injurious in decay4 ,thus ,nature has provided a shore scavenger to devour what would be harmful1 just as the vulture on land eats the carrion4 ,besides this kind of refuse food1 the star-fish eats small crustaceans1 and oysters fall victims to him4 ,by embracing the shell the star-fish manages to insert itself1 and if it cannot bring the oyster out to its mouth1 it will quietly turn out its mouth into the oyster-shell1 and save the bivalve any trouble in the matter4 ,some writers declare that the star-fish stupefies or poisons its victim1 and then the shell opens4 ,these asteroidea can reproduce a ray that has been injured or cut off1 or they can break themselves to pieces if caught4 ,the brittle stars and feather stars appertain to the order of the ,ophiuroida or 8serpent-armed10 because the rays are more flexible and thin than the common star-fish4 ,but they differ very much from the star-fish in the arrangement1 as well as in the shape of their arms4 ,the former possesses rays which form an appendage of the stomach and enclose it4 ,in the brittle stars the rays are limbs1 and could be detached without taking the life of the animal1 except in so far as to deprive it of means to obtain its food4 ,the body is quite independent of the rays1 the mouth occupying the centre1 and is surrounded by minute suckers4 ,the stars are much more flexible than the star-fishes1 their rays are longer1 and serve either as feet1 fins1 tentacles1 or arms4 ,illustration3 ,fig4 #hci4--,spine of echinus 7,a1 natural size2 ,b1 a section magnified74 ,the crinoids also belong to the ,echinodermata1 and resemble plants more than star-fish4 ,they are fixed upon a stalk like a flower1 growing upright from the sea-bottom1 and the body is called a calyx1 which is composed of a ventral and dorsal surface4 ,the arms branch out from the calyx1 just as a small tree does1 and if we can imagine one of the last planted trees on the ,thames embankment reduced to half a finger's length or less1 we have a sort of idea of the crinoid 8in the rough40 ,a polype supported on a stem branching out in feathery1 grassy-looking arms represents the ,encrinites1 the remains of which are found as fossils4 ,the arms of the crinoids are subdivided1 and quite a flowery crown may in time result4 ,the animal obtains its food by the motion of cilia4 ,the stem and the branches are jointed1 as it were1 and capable of flexible movement in any direction4 ,the crinoids remain stationary during their lives4 ,the care taken by the star-fish of its young is remarkable4 ,it carries the eggs about in its suckers and with great caution4 ,the young remain attached to the mother until they are able to go about alone1 and then the physical attachments die off1 and the asteroidea goes forth to seek its fortune in the sea4 ,the echinus1 already mentioned1 is a most elaborately constructed animal2 the plates being secreted from the soft parts are ever being renewed as the animal gets older and larger4 ,the whole subject is well worth a long independent study1 of which it is here impossible for us to give the results4 ,the sea-cucumbers are more like the familiar garden slug than any other animal1 and are surmounted by a fringe round the mouth which looks like leaves4 ,the surface is moist1 and has no horny covering like the 8urchin10 or star fish1 but the suckers are present and are used for locomotion4 ,the tentacles round the mouth serve as prehensile organs4 ,the 8alimentary canal0 is most curiously curved1 and of great length1 and the animal can turn itself 8inside out0 with great facility if alarmed4 ,it possesses a kind of breathing apparatus1 and may be classed as the most highly organized of all the ,echinodermata4 ,these cucumbers are much esteemed by the ,chinese1 and 8trepang10 as they are called1 are caught by thousands in ,australian waters4 ,,annulosa4 ,the worm-like animals are divided into sections1 which include intestinal worms1 entozoa1 annelida1 and crustacea1 with the worms1 spiders1 and insects classed in each section4 ,we may at once perceive what a very extensive division the ,annulosa is1 and we must devote some space to it4 ,illustration3 ,fig4 #hdj4--;,earth worm 7lumbricus terrestris71 leech 7hirudo medicinale74 ,the ,rotifers1 or 8wheel animalcul10 are included in this class2 they stand almost alone1 and certainly invisible to the naked eye4 ,they are very curious animals1 as will be seen from the accompanying illustration4 ,the motion of the cilia around the mouth gives the whirling movement from which their name is derived 7fig4 #hda74 ,the ,,annelides1 or worms1 include earth-worms1 water-worms1 leeches1 etc4 ,the appearance of the earth-worm is so common that few people comparatively studied it until ,mr4 ,darwin's book took the amateur reader by surprise and delighted him1 and to that volume we must refer our readers for details of these very interesting animals1 termed annelides because of the rings appearing upon their bodies4 ,the common leech is well known in medicine4 ,it is curiously enough an inhabitant of ponds and lakes1 and in such conditions has no opportunities for tasting the warm blood for which it develops such a liking when opportunity offers4 ,this is really a remarkable fact1 that the animal should be placed in a position naturally in which its most natural tendencies should remain unsatisfied4 ,the progression of the leech is performed by undulating movements and the prehensile action of the suckers--head and tail4 ,the eyes are ten in number1 near the mouth and at the top of the head4 ,the mouth is furnished with numerous tri-radiate teeth1 but in some leeches they are not sharp1 as in the 8medicinal0 variety4 ,it is known that both sexes are represented in every leech1 but they are not self-reproductive4 ,the earth-worm1 so familiar to all1 has been lately raised into importance4 ,it lives in clay1 and bores its way through the ground4 ,it feeds upon organic matter contained in the earth1 and when it has assimilated the nourishing particles1 it ejects the remainder in small heaps of soft dirt1 which are visible after rain particularly4 ,the worm1 by its burrowing1 turns up the land1 and vastly increases its fertility4 ,illustration3 ,fig4 #hda4--,wheel animalcule 7rotifer vulgaris74 ,the earth-worm in its outer structure resembles the leech1 but1 as any one will at once perceive1 the worm is not furnished with suckers by which it can assist itself to move4 ,instead of these rounded terminals the worm is finely pointed1 and thus capable of boring its way through the earth4 ,progression is accomplished by moving first the head portion and then the next1 so that a regular series of movements is necessary4 ,the minute spines or bristles of the worm prevent its body being retracted by muscular effort4 ,the vital organs are rather forward of the centre of the body1 and so if a worm be cut behind them it will survive and reproduce a tail4 ,but the portion cut off will not be found alive1 nor is it capable of forming a new perfect worm as generally supposed4 ,there are many other orders of worms which we can only indicate--viz41 the ,tubicol which surround themselves with a hard case2 the ,errantia1 or sea-worms1 sand-worms1 etc41 like the lobworm used for bait1 and the naiads of our fresh-water ponds1 all of which are suited to the aquatic life they lead4 ,indeed1 of all the annelides1 the earth-worm is the only specimen that is suited for living upon land4 ,as regards the last mentioned1 we may add that worms do not prey upon dead bodies as is so generally imagined4 ,they are vegetable feeders1 and do not burrow very deeply4 ,the transparent condition of the ,rotifers renders them easy of observation under the microscope1 and we find a nervous system1 intestines1 and a developed stomach4 ,they are fresh-water inhabitants4 ,the ,entozoa or 8intestinal0 worms claim a brief notice at our hands4 ,the entozoa are those beings which inhabit1 as parasites1 the intestines and other parts of animals4 ,their history is still obscure1 but there seems to be about twenty varieties of these creatures1 and a great number of animals have their peculiar entozoa4 ,the best known in the human subject are the 8,ascaris0 or thread-worm1 the 8,lumbricus ,teres0 or long-worm1 and the 8,tnia0 or tape-worm2 this last is jointed1 and grows to several yards in length4 ,the development of these ,tnia is one of the most curious performances of nature4 ,each of the joints shown in the illustration below 7fig4 #hdb7 is a perfected and mature proglottis1 containing the ova or eggs1 which can only be brought to perfection when swallowed by a warm-blooded animal 7not the same from which they emanated74 ,the head within the embryo then holds to the tissues and penetrates to the alimentary canal1 where only it can redevelop joints from the so-called head1 which has no organs and merely pushes out immature joints which are continued1 and they become more mature the farther they are pushed out by the new ones4 ,the 8measles0 of the pig are produced by the ova of these worms4 ,illustration3 ,fig4 #hdb4--,tape worm 7proglottides74 ,,myriapoda4 ,the 8many-footed0 annulosa include the centipedes and millipedes1 and may be regarded as a connecting link between the worms and the insects4 ,the heads of these animals are distinct from the body4 ,the millipedes can be any day found under a large stone in a field which has not been tilled1 or any place where a stone has been suffered to remain for some time undisturbed4 ,these specimens are of the pill-millipede order1 because they roll themselves up into a ball when disturbed4 ,the myriapods of this country are not of large dimensions1 but in tropical climates they attain a great size4 ,the giant centipede has been found in ,south ,america more than a foot long1 and is capable of inflicting severe wounds1 its tenacity being extraordinary and equalling that of the bull-dog when once it has gripped its enemy4 ,the myriapods have no wings2 they possess antenn1 and numerous1 never less than eighteen1 feet1--frequently twenty pairs1 but never a thousand1 much less 8ten thousand0 feet1 as the class name indicates4 ,they are provided with strong forceps or 8foot-jaws10 which supply a poison for killing their enemies4 ,the millipedes and centipedes are known scientifically as ,iulid and ,scolopendrid respectively1 and in most points of internal arrangement resemble insects1 such as breathing by spiracles or 7stomates71 and trach or tubes4 ,some of the centipedes possess electric qualities1 and can administer a shock to an opponent4 ,,insecta4 ,insects inhabit the world around us in myriad forms in air and earth and water4 ,some exist for a very brief space in the air2 others live under water1 or in trees1 or in the ground2 some burrow and hide in chinks of rocks and under stones4 ,the numbers are countless1 and all have some function to perform as palpably as the busy honey-bee1 or as mysteriously as the giddy1 careless butterfly4 ,illustration3 ,fig4 #hdc4--;,anatomy of the external skeleton of an insect4 ,insects are divided into three distinct parts1--viz41 the head1 the thorax1 and the abdomen1 and each of these parts has a pair of legs attached to it1 as will be perceived from the accompanying diagram4 ,along the body are tubes called trach1--for insects do not breathe by lungs1--by which the air is carried into the system of the insect1 by the 8spiracles0 or openings of fine network1 to prevent dust entering the air-passages4 ,the head is joined to the body by a constricted neck1 the part of the body to which it is joined is called the thorax1 and to this is added the posterior part or abdomen2 this part is extremely various in form in different insects2 in some it is round and full1 in others long and extended4 ,the antenn arise from the head1 and are generally composed of eleven pieces variously disposed2 these wonderful organs are possessed of great sensibility1 and they certainly serve to convey information to the insect1 of the nature of one of the special senses2 it was formerly thought to be simply that of touch very much refined1 or of smell1 but it is now generally considered to be that of hearing1 or a modification of it4 ,the forms of the antenn are very various2 fig4 #hde represents that of the cockchafer 7,melolontha vulgaris74 ,the legs proceed from the thorax as do the wings1 the abdomen giving rise to none of the extremities2 the feet of insects are all pretty much upon the same model1 some being more developed than others1 they have a pair of hooks or claws for catching and clinging to rough surfaces1 and a pair of cushions or pads1 covered in some cases with suckers4 ,illustration3 ,fig4 #hdd4--,spiracle4 ,illustration3 ,fig4 #hde4--;,antenna of cockchafer 7melolontha vulgaris74 ,the foot of the common house-fly is most beautifully fitted for its progression and support4 ,we have often wondered how the fly manages to support itself back downwards on the ceiling1 or walk up glass4 ,we give a cut of the fly's foot 7fig4 #hdf74 ,illustration3 ,fig4 #hdf4--;,foot of fly1 magnified4 ,the eyes of insects are also marvellous4 ,there are only two1 but each one is composed of numerous cells 7ocelli71 and look like a honey-comb4 7,see illustration1 fig4 #hdg47 ,illustration3 ,fig4 #hdg4--;,compound eye4 #a4 ,perpendicular section2 #b4 ,surface4 ,insects swarm in innumerable companies1 and no one who has not seen the locusts descending upon the earth can form more than a faint idea of the devastation they occasion in an incredibly short time4 ,these1 as well as thousands of other insects1 exist in myriads1 and we must content ourselves1 on this occasion1 by merely noting the different orders and their characteristics1 after we have mentioned some of the attributes common to all4 ,the term 8insect0 means cut into or divided1 and so the insecta are divided1 as already mentioned1 into three parts1--head1 thorax1 and abdomen1--the thorax being subdivided into three rings1 pro-thorax1 meso-thorax1 and meta-thorax--beginning1 middle1 and end4 ,all insects have six legs1 and usually two or four wings1 though some have no wings at all4 ,the legs are united to the thorax1 the antenn and eyes to the head4 ,the abdomen contains the important sexual organs1 a sting or defensive weapon1 and in females the egg chamber4 ,insects breathe by tubes in the sides1 and consume a great quantity of air4 ,their powers of flying and leaping are too familiar to need dwelling upon4 ,the wings display beautiful colours like those observable in the soap-bubble1 others are covered with scales or hairs4 ,the mouths vary very much with the species1 as the manner of obtaining food is by suction or gnawing4 ,the blood of insects is pale and thin4 ,the various transformations which insects undergo are always a subject of interest for the young student4 ,the ugly forms which develop in beautiful creations are more astonishing than the change of the 8ugly duckling0 into the graceful swan4 ,illustration3 ,fig4 #hdh4--,larva4 ,illustration3 ,fig4 #hdi4--,pupa4 ,insects come to maturity only after undergoing successive changes from the egg to the perfect animal4 ,the eggs 7some of which are very beautiful7 are first deposited in some safe place1 either attached to a leaf or tied up in a small bundle by silken threads spun by the parent insect1 and in some nutritious substance1 so that when it comes to life it may at once have food2 this is sometimes in manure1 sometimes in flesh1 and sometimes under the skin of a living animal 7few are exempt from this infliction71 where they remain for a time and then come forth as maggots1 caterpillars1 etc42 in this state they are called larv1--these are generally active creatures and eat most voraciously1 which seems to be the principal act of this state of their existence4 ,these larv frequently change their skins as they grow1 and at last they assume the next stage of their life1 the pupa or chrysalis state1 which is one generally of complete inactivity2 many of these larv weave themselves a covering of a sort of silk1 to defend them while in the pupa state1--such as the silkworm1 whose covering 7cocoon7 is the source of all the silk of commerce1--others merely place themselves in a situation of security4 ,the pupa remains dormant for a certain time1 and then becomes the imago or perfect insect 7the last state of its existence71 such as a moth1 a butterfly1 a beetle1 etc4 ,these are of different sexes1 and in due time produce a batch of eggs and then die2 these eggs are often incredible in numbers1 amounting to many thousands--but few escape the watchful eyes of other insects and of birds who feed upon them4 ,but there are some of the insecta which do not undergo metamorphosis2 the ,,aptera or wingless insects include these1 as the flea and such parasites which bore into other animals1 and deposit their eggs within them4 ,illustration3 ,fig4 #hej4--;,imago4 ,insects have very little means for making themselves audible1 at least so far as can be ascertained4 ,the humming of bees and flies and other insects are1 of course1 not intended to represent the voice4 ,the cricket's 8chirp10 as people commonly imagine1 but the sound is attributable to the rubbing together of the wings or wing-cases1 as is the noise produced by the field-cricket4 ,there is a very peculiar sound attributable to the 8,death-,watch10 a ticking1 and to nervous people terrible warning of dissolution4 ,it may reassure some one1 perhaps1 to know that this 8unearthly sound0 is caused simply by the insect beating its head against a piece of wood to attract its mate1 as the female glow-worm lights her lamp to guide her lord to her bower4 ,the ,,insecta may simply be divided into nine orders3-- #a ,,coleoptera4 ,beetle tribe4 ,case-winged4 #b ,,orthoptera4 ,locusts1 crickets1 etc4 ,straight-winged4 #c ,,neuroptera4 ,dragon-flies1 etc4 ,nerve-winged4 #d ,,hymenoptera4 ,bees1 ants1 wasps1 etc4 ,membrane-winged4 #e ,,strepsiptera4 ,parasites of the foregoing4 ,twisted-winged4 #f ,,lepidoptera4 ,moths and butterflies4 ,scale-winged4 #g ,,hemiptera4 ,bugs1 water-boatmen4 ,half-winged4 #h ,,diptera4 ,house-fly1 gnat4 ,two-winged4 #i ,,apraniptera4 ,fleas1 8chigos40 ,wingless4 7,of these the metamorphoses of #a1 #c1 #d1 #f1 and #h are complete74 ,illustration3 ,fig4 #hea4--,the ,stag-,beetle 7,lucanus cervus74 ,the ,,coleoptera are well represented in ,england as beetles4 ,they have four wings1 but the outer pair serve as coverings to the inner ones4 ,they are termed ,elytra1 and are horny in texture4 ,these beetles are short-lived1 but useful as scavengers1 and serve to manure the ground by burying objectionable matter4 ,the larv of beetles eat tremendously4 ,the stag-beetle is a formidable-looking animal1 and the lady-bird is well known as an enemy to the aphides on our rose trees4 ,the tiger-beetle1 cockchafer1 and various water-beetles belong to this family4 ,the scarabee1 or sacred ,egyptian beetle1 also will be found classed with the coleoptera4 ,many of these beetles are excellent scavengers1 and some called burying beetles remove the soil underneath the carcases of birds and other small dead animals1 letting them fall down below the ground level2 the beetles then lay their eggs in the body1 so that sustenance may be at hand for the young when hatched4 ,the ,,orthoptera include our cockroaches1 miscalled 8black beetles10 the locusts1 crickets1 etc4 ,the ravages of the locust are well known4 ,the larv of the orthoptera has no wings1 but otherwise is very like the grown insect4 ,they change their skins frequently before they become perfect insects4 ,passing the 8nerve-winged0 dragon-flies and caddis1 whose larv case is so familiar and useful as bait1 we come to the very important and interesting order of ,,hymenoptera1 with four membranous wings4 ,in this rank we find bees1 wasps1 and ants1 the first and last named being proverbial for industry and examples of almost superhuman reasoning powers1 and a similitude to man's arrangements in labour and house-building marvellous to contemplate4 ,a study of the habits of ants1 bees1 and wasps will reveal a state of society existing amongst them which more nearly resembles man in feelings and habits1 for these insects possess means of oral communication4 ,illustration3 ,fig4 #heb4--;,honey-lapping apparatus of wild sea-bee 7,halictus71 7a1 magnified2 a b1 more highly magnified74 ,all these insects are armed with a sting1 or other offensive weapon4 ,the ant possesses the 8formic0 acid1 which derives its name from the possessor4 ,the destructive white ants will eat away a wooden house very quickly1 sapping and mining it in all directions till it is a mere skeleton4 ,the habits of bees are so well known and have been so often described that we need not detail them4 ,the manner in which the ants 8milk0 the aphides is curious and interesting4 ,illustration3 ,fig4 #hec4--,scales from moth's wing 7magnified74 ,the ,,strepsiptera order includes very few species1 so we may pass quickly to the ,,lepidoptera1 the butterflies and moths1 whose beautiful colourings and markings have attracted us all from childhood4 ,there are about #ab1jjj species of the lepidoptera1 and they are divided into 8moths0 and 8butterflies10 the former being seen in twilight1 or darkness1 the latter in sunlight4 ,they can readily be distinguished by the antenn1 those of the butterfly being tipped1 or knobbed4 ,the silkworm belongs to this family4 ,these insects undergo complete metamorphosis4 ,the remaining two orders of insects include the house-flies and gnats2 and the flea1 and jigger1 or chigo1 which penetrates the skin and lays its eggs in the flesh1 causing thereby dangerous inflammation4 ,,crustacea4 ,this class includes a number of familiar animals such as the barnacle1 the crab1 the lobster1 shrimp1 etc42 and curious as it may appear are closely related to our spiders4 ,their cases or coverings are all articulated or disposed in distinct segments4 ,they breathe through gills or by tubes1 and possess legs1 or appendages for walking1 eating1 or guidance4 ,they are generally marine creatures4 ,illustration3 ,fig4 #hed4--;,crustacea4 #a4 ,lobster 7,astacus marinus72 #b4 ,cray-fish 7,astacus fluviatilis72 #c4 ,crab 7,cancer pagurus72 #d4 ,shrimp 7,crangon vulgaris72 #e4 ,prawn 7,palmon serratus74 ,the shell of the crustacea is composed largely of lime1 and of course becomes very hard in time4 ,it is formed from the skin4 ,the body1 like that of an insect1 is composed of head1 thorax1 and abdomen1 divided into twenty-one segments1 of which seven occupy the head1 seven the thorax1 and the remainder the abdomen4 ,twenty segments are furnished with legs1 or feelers1 or claws--a pair to a segment4 ,the lobster or crayfish will give excellent examples of the anatomy of the macrura or lobster kind of crustacea4 ,the heart is situated in the back4 ,the following table given by ,professor ,nicholson will explain the 8segments and appendages0 of the lobster3-- #ast ,segment1 ,eyes4 #bnd 0 ,lesser antenn #crd 0 ,greater antenn4 ,head #dth 0 ,pair of biting jaws4 #eth 0 ,first pair of chewing jaws4 #fth 0 ,second pair of chewing jaws4 #gth 0 ,first pair of foot jaws4 #hth 0 ,second pair of foot jaws4 #ith 0 ,third pair of foot jaws4 #ajth 0 ,first pair of legs 7claws74 ,thorax #aath 0 ,second pair of legs 7small claws74 #abth 0 ,third pair of legs 7small claws74 #acth 0 ,fourth pair of legs4 #adth 0 ,fifth pair of legs4 #aeth 0 ,ground appendages4 #afth 0 ,swimmerets4 #agth 0 0 ,abdomen #ahth 0 0 #aith 0 0 #bjth 0 ,large swimmerets4 #bast 0 ,no appendages 7tail fin74 ,the tail is1 as may be supposed1 the great aid to locomotion in the lobster family1 and they can swim backwards with great rapidity by its assistance4 ,lobsters shed their claws when alarmed1 and are easily caught by a glittering bait4 ,the hermit crabs are interesting creatures1 but do not possess the horny coat of the crab or lobster4 ,they are therefore compelled to inhabit an empty shell1 into which they thrust themselves1 holding to the bottom of it by their tail1 while a large claw guards the entrance4 ,when the animal gets too big for his house he moves to another1 leaving the old home for another hermit of the shore4 ,the crabs have no developed tails1 and are therefore called brachyura--8short-tailed10 and they are walking creatures4 ,there are king crabs1 land crabs1 and the common swimming crab4 ,these animals can shed their shells as other crustaceans1 and a curious fact is they shed them whole4 ,how the claws come out must remain more or less a mystery4 ,raumur investigated the action of the crayfish1 and noticed that as the casting time approached the crustacea retired to some hiding-place and remained without eating4 ,the shell becomes gradually loosened1 and at last by putting its feet against a stone and pushing backwards the animal jerks himself away4 ,it must be a painful operation1 for the mill-like teeth of the stomach are also rejected1 and the joints do not give way4 ,after a while a new shell appears1 and is cast in due time as before4 ,the eyes of the crustacea are situated in front1 and are composed like the insects1 or are simple1 like spiders4 ,they possess a sense of hearing evidently4 ,the eggs of the lobster are carried by the female1 and they are termed the 8coral0 in consequence of their red and beadlike appearance4 ,our space will not admit of our saying much more concerning the interesting crustacea1 though the barnacles1 so well known by sight by all dwellers at the sea1 and called ,cirripedia1 which fix themselves to rocks and ships1 deserve notice4 ,the young are capable of movement1 and this fact was first discovered in #ahcj4 ,it resembled a mussel1 but when kept in sea-water it adhered to the vessel which retained it4 ,the cirripedia are so called from the cirri or arms which they possess1 and by which they are enabled to entangle or catch their food1 as in a net4 ,they hold themselves by a 8foot stalk40 ,the goose-mussel1 or barnacle1 is very common1 but must not be confounded with the limpet4 ,dr4 ,baird gives the following description of them3--8,the cirripeds are articulated animals contained within a hard covering composed of several pieces and consisting of calcified chitine4 ,the body of the animal is enclosed in a sac lined with the most delicate membrane of chitine1 which in one group is prolonged into a peduncle and contains the ova2 the body is distinctly articulated and placed with the back downwards4 ,,arachnida--,,spiders4 ,there are many families of arachnida besides the well-known garden and house spiders4 ,the sea spiders1 though classed with the arachnida1 are sometimes placed amongst the crustacea4 ,we have the 8tick0 and the cheese-mite and the scorpions2 all of which belong to the spider family4 ,but the true spiders are known by the joining of the two upper segments1 the thorax and head being united 7cephalo-thorax74 ,the pretty and marvellous webs are spun from abdominal glands through small apertures4 ,the fluid hardens in its passage sufficiently to be woven into threads to resist the struggles of the captured prey4 ,the forms of these webs vary1 but some spiders do not catch their victims in the net2 they pounce upon them cat fashion4 ,the large house spider is well known to all4 ,the garden spider is seen in the illustration 7fig4 #hee7 with the scorpion4 ,the habits of spiders will be found a very interesting study1 and many volumes have been devoted to them4 ,the water spider is a frequent inmate of an aquarium1 and the bubble of air he takes down with him to breathe serves as a means of living while he is seeking his aquatic prey4 ,illustration3 ,fig4 #hee4--;,arachnida4 #a4 ,spider 7,epeira diadema72 #b4 ,scorpion 7,scorpio74 ,we will close our rapid survey of the invertebrate animals with a glance at the ,,mollusca1 which are divided into six classes 7see page #gjc74 ,the first is the ,tunicata1 which have no shell or hard covering1 and come under the denomination of molluscoids1 and belong to a lower order4 ,the true mollusca include the ,brachiopoda1 which have a pair of shells4 ,they are called 8arm-footed0 because a long cord or tendon passes through one of the shells1 and fixes the mollusc to the rock4 ,the ,lingula of this class have been discovered in very old formations such as the ,devonian period1 and indeed appear to have been amongst the first created animals4 ,illustration3 ,fig4 #hef4--,mollusca4 #a4 ,nautilus 7,argonauta72 #b4 ,clio ,borealis2 #c4 ,mussel 7,mytilus edule74 ,the ,lamellibranchiata include the oyster1 cockle1 mussel1 etc4 ,they are well known1 and scarcely need description4 ,the ,pteropoda have no shell4 ,the ,gasteropoda are very numerous1 and periwinkles1 whelks1 snails1 etc41 belong to this class4 ,they progress by a muscular 8mantle10 which is extended and contracted4 ,the 8horns0 have eyes at the extremities4 ,when they retire into their 8houses0 they can close the door by a kind of lid called the 8operculum40 ,the ,cephalopods include the nautilus and the cuttle fish1 the terrible squid1 or octopus1 etc4 ,wonderful tales are told of the tenacity and ferocity of the 8,poulpes10 and no doubt in long-past ages these animals attained a gigantic growth4 ,they are very unpleasant enemies1 and the cold1 slimy grasp of the long tentacles is apt to give one the 8horrors10 while the terrible head and beak fill one with dismay4 ,the poulpes are very formidable opponents1 and discretion will certainly be the better part of valour when they appear in our vicinity4 ,we must here close our sketch of the ,invertebrates1 and we regret that the limits of our volume will not permit us to continue this interesting subject1 nor can we find space1 at present1 for even the barest description of the ,vertebrate animals4 ,illustration3 ,the sun-fish 7,orthagoriscus74 ,,chapter ,,lvi4 ,,the ,,analysis ,,of ,,chance ,,and ,,mathematical ,,games4 ,,magic ,,squares--,,the ,,sixteen ,,puzzle--,,solitaire--,,equivalents4 ,we will now proceed to draw our readers' attention to several experiments very famous at a former period1 but which our own generation has completely overlooked4 ,we refer to the ,analysis of ,chance1 a science still known under the title of ,calculation of ,probabilities1 formerly cultivated with so much ardour1 but to-day almost fallen into oblivion4 ,originating in the caprice of the clever ,chevalier de ,mr1 who in #afed suggested the game to ,pascal1 the analysis of chance has given rise to investigations of an entirely novel kind1 and attempts have been made to measure the mathematical degree of credence to be given to simple conjectures4 ,we will first recapitulate the principles laid down by ,laplace on this subject4 ,we know that of a certain number of events1 one only can happen1 but nothing leads us to the belief that one will happen more than the other4 ,the theory of chance consists in reducing all the events of the same kind to a certain number of equally possible cases1 such1 that is to say1 that we are equally undecided about1 and to determine the number of cases favourable to the event1 whose probability we are seeking4 ,the ratio of this number to that of all possible cases is the measure of this probability1 which is thus a fraction1 the numerator of which is the number of favourable cases1 and the denominator the number of all possible cases4 ,when all the cases are favourable to an event1 its probability changes to certainty1 and it is then expressed by the unit4 ,probabilities increase or diminish by their mutual combination2 if the events are independent of each other1 the probability of the existence of their whole is the product of their particular probabilities4 ,thus the probability of throwing an ace with one dice being #a_/f1 that of throwing two aces with two dice is #a_/cf4 ,each of the sides of one dice combining with the six sides of the other1 there are thirty-six possible cases1 among which one only gives the two aces4 ,when two events depend on each other1 the probability of the double event is the product of the probability of the first event by the probability that1 that event having occurred1 the other will occur4 ,this rule helps us to study the influence of past events on the probability of future events4 ,if we calculate priori the probability of the event that has occurred and an event composed of this and another expected event1 the second probability divided by the first1 will be the probability of the expected event1 inferred from the observed event4 ,the probability of events serves to determine the hope or fear of persons interested in their existence4 ,the word hope here expresses the advantage which someone expects in suppositions which are only probable4 ,this advantage in the theory of chances is the product of the hoped-for sum by the probability of obtaining it2 it is the partial sum which should arise when one does not wish to run the risks of the event1 supposing that the apportionment corresponds to the probabilities4 ,this apportionment is only equitable when we abstract from it all foreign circumstances2 because an equal degree of probability gives an equal title to the hoped-for sum4 ,this advantage is called mathematical hope4 ,nevertheless1 the rigorous application of this principle may lead to an inadmissible consequence4 ,let us see what ,laplace says4 ,paul plays at heads and tails1 on the understanding that he receives two shillings if he succeeds at the first throw1 four shillings if he succeeds at the second1 eight at the third1 and so on4 ,his stake on the game1 according to calculation1 must be equal to the number of throws2 so that if the game continues indefinitely1 the stake also continues indefinitely4 ,yet1 no reasonable man would venture on this game even a moderate sum1 #b for example4 ,whence1 therefore1 comes this difference between the result of the calculation1 and the indication of common-sense8 ,we soon perceive that it proceeds from the fact1 that the moral advantage which a benefit procures for us is not proportional to this advantage1 and that it depends on a thousand circumstances1 often very difficult to define1 but the chief and most important of which is chance4 ,in fact1 it is evident that a shilling has much greater value for one who has but a hundred than for a millionaire4 ,we must1 therefore1 distinguish in the hoped-for good between its absolute and its relative value2 the latter regulates itself according to the motives which cause it to be desired1 while the former is independent4 ,in the absence of a general principle to appreciate this relative value1 we give a suggestion of ,daniel ,bernouilli which has been generally admitted4 ,the relative value of an extremely small sum is equal to its absolute value1 divided by the total advantage of the interested person4 ,on applying the calculus to this principle1 it will be found that the moral hope1 the growth of chance due to expectations1 coincides with the mathematical hope1 when chance1 considered as a unit1 becomes infinite in proportion to the variations it receives from expectations4 ,but when these variations are a sensible portion of the unit1 the two hopes may differ very greatly from each other4 ,in the example cited1 this rule leads to results conformable to the indications of common-sense4 ,we find1 in point of fact1 that if ,paul's fortune amounts only to #h1 he cannot reasonably stake more than #gs4 on the game4 ,at the most equal game1 the loss is always1 relatively greater than the gain4 ,supposing1 for example1 that a person possessing a sum of #d1 stakes #b on a game of heads or tails1 his money after placing his stake will be morally reduced to #c #aas4 #j;d4--that is to say1 this latter sum will procure him the same moral advantage as the condition of his funds after his stake4 ,whence we draw this conclusion3 that the game is disadvantageous1 even in the cases where the stake is equal to the product of the sum hoped for by the probability4 ,we may1 therefore1 form an idea of the immorality of games in which the hoped-for sum is below this product4 ,illustration3 ,fig4 #heg4--,the game of the needle4 ,jacques ,bernouilli has thus laid down the result of his investigations on the calculation of probabilities4 ,an urn containing white and black balls is placed in front of the spectator1 who draws out a ball1 ascertaining its colour1 and puts it back in the urn4 ,after a sufficient number of draws1 the total number of extracted balls divided by the total number of balls represents a fraction very near to that which has for a numerator the real number of white balls existing in the urn1 and for the denominator the total number of balls4 ,in other words1 the ratios of the number either of extracted white balls1 or the whole of the white balls to the total number1 tend to become equal2 that is1 the probability derived from this experiment approaches indefinitely towards a certainty4 ,the two fractions may differ from each other as little as possible1 if we increase the number of draws4 ,from this theorem we deduce several consequences4 #a4 ,the relations of natural effects are nearly constant when these effects are considered in a great number4 #b4 ,in a series of events indefinitely prolonged1 the action of regular and constant causes affects that of irregular causes4 ,applications4--,the combinations presented by these games have been the subject of former researches regarding probabilities4 ,we will complete our exposition with two more examples4 ,two persons1 ,a and ,b1 of equal skill1 play together on the understanding that whichever beats the other a certain number of times1 shall be considered to have won the game1 and shall carry off the stakes4 ,after several throws the players agree to give up without finishing the game2 and the point then to be settled1 is in what manner the money is to be divided between them4 ,this was one of the problems laid before ,pascal by the ,chevalier de ,mr4 ,the shares of the two players should be proportional to their respective probabilities of winning the game4 ,these probabilities depend on the number of points which each player requires to reach the given number4 ,a's probabilities are determined by starting with the smallest numbers1 and observing that the probability equals the unit1 when player ,a does not lose a point4 ,thus1 supposing ,a loses but one point1 his chance is #ab1 #cd1 #gh1 etc41 according as ,b misses one1 two1 or three points4 ,supposing ,a has missed two points1 it will be found that his chance is as #ad1 #ab1 #aaf1 etc41 according as ,b has missed one1 two1 or three points1 etc4 ,or we may suppose that ,a misses three points1 and so on4 ,we should note1 en passant1 that this solution has been modified by ,daniel ,bernouilli1 by the consideration of the respective fortune of the players1 from which he deduces the idea of moral hope4 ,this solution1 famous in the history of science1 bears the name of the ,petersburgh problem1 because it was made known for the first time in the 8,memoires de l',acadmie de ,russie40 ,we will now describe the game of the needle4 ,it is a genuine mathematical amusement1 and its results1 indicated by theory1 are certainly calculated to excite astonishment4 ,the game of the needle is an application of the different principles we have laid down4 ,if we trace on a sheet of paper a series of parallel and equi-distant lines1 ,,aa#a1 ,,bb#a1 ,,cc#a1 ,,dd#a1 and throw down on the paper at hazard a perfectly cylindrical needle1 a b1 the length of which equals half the distance between the parallel lines 7figs4 #heh and #hei71 we shall discover this curious result4 ,if we throw down the needle a hundred times1 it will come in contact with one of the parallel lines a certain number of times4 ,dividing the number of attempts with the number of successful throws1 we obtain as a quotient a number which approaches nearer the value of the ratio between the circumference and the diameter in proportion as we multiply the number of attempts4 ,this ratio1 according to the rules of geometry1 is a fixed number1 the numerical value of which is #cadaeibf4 ,after a hundred throws we generally find the exact value up to the two first figures3 #ca4 ,how can this unexpected result be explained8 ,the application of the calculus of probabilities gives the reason of it4 ,the ratio between the successful throws and the number of attempts1 is the probability of this successful throw4 ,the calculation endeavours to estimate this probability by enumerating the possible cases and the favourable events4 ,the enumeration of possible cases exacts the application of the principle of compound probabilities4 ,it will be easily seen that it suffices to consider the chances of the needle falling between two parallel lines1 ,,aa#a and ,,bb#a 7fig4 #heh71 and then to consider what occurs in the interval1 m n1 equal to the equi-distance4 ,to obtain a successful throw1 it is necessary then3-- #a4 ,that the middle of the needle should fall between m and l1 the centre of m o4 #b4 ,that the angle of the needle with m o will be smaller than the angle1 m c b4 ,the calculation of all these probabilities and their combination by multiplication1 according to the rules of compound probabilities1 gives as the final expression of probability the number4 ,illustration3 ,fig4 #heh4--,the needle game4 ,illustration3 ,fig4 #hei4--,the needle game4 ,this curious example justifies the theorem of ,bernouilli relating to the multiplication of events2 there is no limit to the approximation of the result1 when the attempts are sufficiently prolonged4 ,when the length of the needle is not exactly half the distance between the parallel lines1 the practical rule of the game is as follows3 ,the ratio between the number of throws and the number of successful attempts must be multiplied by double the ratio between the length of the needle and the distance between the parallel lines4 ,in the case cited above1 the double of the latter ratio equals the unit4 ,we will give an application to this4 ,a needle two inches long is thrown #aj1jjj times on a series of parallel lines1 two-and-a-half inches apart2 the number of successful throws has been found to equal #ejjj4 ,we take the ratio #ajij_/ejji1 and multiply it by the ratio #ajjj_/fcf and the product is #cadba4 ,the true value is #cadae4 ,we have an approximation of #f_/ajjjj4 ,the dimensions indicated in this experiment are those which present in a given number of attempts the most chances of obtaining the greatest possible approximation4 ,we will conclude these remarks on games by some observations borrowed from ,laplace4 ,the mind has its illusions like the sense of sight2 and just as the sense of touch corrects the latter1 reflection and calculation correct the former4 ,the probability founded on an every-day experience1 or exaggerated by fear or hope1 strikes us as a superior probability1 but is only a simple result of calculation4 ,in a long series of events of the same kind1 the mere chances of accident sometimes offer these curious veins of good or bad fortune1 which many persons do not hesitate to attribute to a kind of fatality4 ,it often happens in games which depend both on chance and the cleverness of the players1 that he who loses1 overwhelmed with his want of success1 seeks to repair the evil by rash playing1 which he would avoid on another occasion2 he thus aggravates his own misfortune and prolongs it4 ,it is then1 however1 that prudence becomes necessary1 and that it is desirable to remember that the moral disadvantage attaching to unfavourable chances is increased also by the misfortune itself4#da ,mathematical games1 formerly so much studied1 have recently obtained a new addition in the form of an interesting game1 known as the 8,boss0 puzzle4 ,it has been introduced from ,america1 and consists of a square box1 in which are placed sixteen small wooden dice1 each bearing a number 7fig4 #hfj74 ,no4 #af is taken away1 and the others are placed haphazard in the box1 as shown in fig4 #hfa4 ,the point is then to move the dice1 one by one1 into different positions1 so that they are at last arranged in their natural order1 from one to fifteen2 and this must be accomplished by slipping them from square to square without lifting them from the box4 ,if the sixteenth dice is added1 the game may be varied1 and we may seek another solution of the problem1 by arranging the numbers so that the sum of the horizontal1 vertical1 and diagonal lines gives the number #cd4 ,in this form the puzzle is one of the oldest known4 ,it dates from the time of the primitive ,egyptians1 and has often been investigated during the last few centuries1 belonging1 as it does1 to the category of famous magic squares1 the principles of which we will describe4 ,the following is the definition given by ,ozanam1 of the ,academy of ,sciences1 at ,paris1 at the end of the seventeenth century4 ,the term magic square is given to a square divided by several small equal or broken squares1 containing terms of progression which are placed in such a manner that all those of one row1 either across1 from top to bottom1 or diagonally1 make one and the same sum when they are added1 or give the same product when multiplied4 ,it is therefore evident from this definition1 that there are two kinds of magic squares1 some formed by terms of arithmetical progression1 others by terms of geometrical progression4 ,we must also distinguish the equal from the unequal magic squares4 ,illustration3 ,fig4 #hfj4--,the sixteen puzzle4 ,illustration3 ,fig4 #hfa4--,the numbers placed at hazard1 and ,no4 #af removed4 ,we give here several examples of magic squares with terms of mathematical progression1 among them the square of #cd1 giving one of the solutions to the puzzle just described 7fig4 #hfb74 ,we also give an example of a magic square composed of terms of geometrical progression4 ,the double progression for examples #a1 #b1 #d1 #h1 #af1 #cb1 #fd1 #abh1 #bef1 as here arranged 7fig4 #hfc71 forms such a square that the product obtained by multiplying the three terms of one row1 or one diagonal1 is #d1jif1 which is the cube of the mean term #af4 ,the squares have been termed magic1 because1 according to ,ozanam1 they were held in great veneration by the ,pythagoreans4 ,in the time of alchemy and astrology1 certain magic squares were dedicated to the seven planets1 and engraved on a metal blade which sympathized with the planet4 ,to give an idea of the combinations to which the study of magic squares lends itself1 it is sufficient to add that mathematicians have written whole treatises on the subject4 ,frnicle de ,bessy1 one of the most eminent calculators of the seventeenth century1 consecrated a part of his life to the study of magic squares4 ,he discovered new rules1 and found out the means of varying them in a multitude of ways4 ,thus for the magic square1 the root of which is #d1 only sixteen different arrangements were known4 ,illustration3 ,fig4 #hfb4--;,examples of magic squares formed by terms of arithmetical progression4 ,illustration3 ,fig4 #hfc4--,magic square formed by terms of geometrical progression4 ,frnicle de ,bessy found #hhj new solutions4 ,an important work from the pen of this learned mathematician has been published under the title of 8,carrs ou ,tables ,magiques10 in the 8,memoirs de l',acadmie ,royale des ,sciences10 from #afff-afii1 vol4 v4 ,amateurs1 therefore1 who are accused of occupying themselves with a useless game1 unworthy the attention of serious minds1 will do well to bear in mind the works of ,frnicle1 and better still1 to consult them4 ,we have so far considered only the first part of the puzzle4 ,we may now examine the problem to which specially it has given rise4 ,we are quite in accord with ,m4 ,piarron de ,mondesir1 who has been so good as to enlighten us upon the subject1 which is really much more difficult than it appears4 ,a ,french paper once proposed to give a prize of #ejj francs to any individual who would solve the following problem3-- ,throw the numbers out of the box1 replace them at hazard1 then in arranging them place them in the following order 7,a fig4 #hfd74 ,illustration3 ,fig4 #hfd4--,the ,sixteen ,puzzle4 ,now nobody solved this problem1 because in nine cases out of ten it is impossible to do so4 ,the first twelve numbers will come correctly into their places1 and even #ac can be put in its place without much trouble2 but1 instead of getting the last row right we shall find it will come out like ,b1 viz41 #ad1 #ae1 #ac1 in the large majority of instances4 ,so any case can be solved in one of the two results given above1 and we can tell in advance1 without displacing a number1 in which way the puzzle will eventuate4 ,illustration3 ,fig4 #hfe4--;,example #a4 ,illustration3 ,fig4 #hff4--;,example #b4 ,let us give this problem our attention for a few minutes1 and we shall not find it difficult4 ,take the first example4 ,we will throw the cubes out of the box and put them back in the order shown in fig4 #hfe4 ,we see now that #a occupies the place of #aa1 #aa that of #g1 #g that of #h1 #h that of #f1 #f of #ae1 #ae of #a4 ,this much is evident without any study4 ,we formulate these figures as follows1 beginning with #a and working from figure to figure till we are led to #a again1 and so on4 #ast4 ,series4--#a1 #aa1 #g1 #h1 #f1 #ae1 #a 7#f7 even4 ,counting the number of different cubes we have #f2 and we put 7#f7 in a parenthesis4 ,we call the first series even because #f is an even number4 ,we now establish1 by the same formula1 a second series commencing with #b1 and going back to it1 thus-- #bnd ,series4--#b1 #d1 #b 7#b7 even4 #crd ,series4--#c1 #e1 #aj1 #ab1 #c 7#d7 even4 #dth ,series4--#i1 #ac1 #ad1 #i 7#c7 uneven4 ,we have now four series1 the total number of points equal #ae1 as there ought to be1 for one cube is absent4 ,let us now take another example 7see fig4 #hff71 and by working as before we have four series again1 viz3-- #ast ,series4--#a1 #g1 #a 7#b7 even4 #bnd ,series4--#b1 #aa1 #c1 #h1 #d1 #ae1 #b 7#f7 even4 #crd ,series4--#e1 #ab1 #ac1 #e 7#c7 uneven4 #dth ,series4--#i1 #ad1 #aj1 #i 7#c7 uneven4 ,this gives us only #ad as a total1 because #f has not been touched at all4 99 99 99 99 99 ,and now for the rule1 so that we may be able to ascertain in advance1 when we have established our series1 whether we shall find our puzzle right or wrong at the end4 ,we must put aside all unplaced numbers and take no notice of uneven series4 ,only the even series must be regarded4 ,thus if we do not find #a1 or if we find #b1 #d1 or #f1 the problem will come into ,a as a result4 ,if we find #a1 #c1 #e1 or #g1 the case will eventuate as in ,b 7fig4 #hfd74 ,let us apply the rule to the problems we have worked1 and then the reason will be apparent4 ,in the first we find three even series2 the problem will then end as in ,b diagram 7fig4 #hfd71 for the number of like series is odd4 ,in the second we find two even series 7pairs72 we shall find our problem work out as in diagram ,a 7fig4 #hfd71 for the number of like series is even1 one pair in each4 ,we are now in possession of a simple rule1 both rapid and infallible1 and which will save considerable trouble1 as we can always tell beforehand how our puzzle will come out4 ,any one can test the practicability of the rules for himself1 but we may warn the reader that he will never be able to verify every possible instance1 for the possible cases are represented by the following sum-- #bcdefghiajaaabacadae4 ,that is to say1 #a1cjg1fgd1cfh1jjj in all4 ,,solitaire4 ,this somewhat ancient amusement is well known1 and the apparatus consists of a board with holes to receive pegs or cups to receive the balls1 as in the illustrations 7figs4 #hfg and #hgj47 ,the usual solitaire board contains thirty-seven pegs or balls1 but thirty-three can also be played very well4 ,many scientific people have made quite a study of the game1 and have published papers on the subject4 ,m4 ,piarron de ,mondesir has given two rules which will prove interesting4 ,the first is called that of equivalents1 and supposes the game to be played out to a conclusion2 the second1 called the ring-game1 admits of a calculation being made so that the prospects of success can be gauged beforehand4 ,the method of play is familiar1 so we need not detail it4 ,it is simply 8taking0 the balls by passing over them in a straight line4 ,the method of 8equivalents0 consists in replacing one ball with two others1 as we will proceed to explain by the diagram 7fig4 #hfh74 ,illustration3 ,fig4 #hfg4--,solitaire4 ,suppose we try the #cc game1 which consists in filling every hole with the exception of the centre one1 and in 8taking0 all the balls1 leaving one solitary in the centre at the last4 ,suppose an inexperienced player arrives at an impossible solution of five balls in #d1 #aa1 #ae1 #bh1 and #cj4 ,to render the problem soluble1 and to win his game1 ,i will replace ,no4 #aa by two equivalents1 #i and #aj1 the ball #bh by two others1 #bc and #af1 and the ball #cj by #be and #ah4 ,these substitutions will not change the 8taking off10 for ,i can take #aj with #i1 #bc with #af1 and #be with #ah4 ,but by so doing ,i substitute for an irreducible solution of five balls a new system of eight 7those shown with the line drawn through them in the diagram71 which can easily be reduced to the desired conclusion1 and the game will be achieved4 ,there are in reality three terminations possible to the problem--the single ball1 the couple1 and the tierce2 that is1 you may have only one left1 or two placed diagonally1 such as #i-ag1 #be-bi1 or a system of three in a straight line1 #i-af-bc4 ,by the 8equivalents0 you can always succeed in solving the problem desired4 ,we will now point out four transformations which are very easy to effect1 and result from the rule of 8equivalents40 #a4 ,replacement of the two balls1 situated on the same line and separated by an empty cup1 by one put into that cup4 ,thus ,i can replace #bc and #be by a single ball at #bd4 #b4 ,suppression of tierces4 ,and by the above movement ,i suppress the tierce #i-af-bc4 #c4 ,correspondent 8cases0 are two holes situated in the same line and separated by two cups4 ,if two corresponding cups are filled1 ,i can suppress the balls which occupy them4 ,so ,i can put aside #d and #bc4 ,illustration3 ,fig4 #hfh4--;,correspondents and equivalents4 #d4 ,it is permissible to move a ball into one of the correspondent cups if it be vacant2 thus ,i can put #aj into #bi4 ,these are the four transformations which can be made evident with the rings1 without displacing the balls4 ,to do this we need have only seven rings large enough to pass over the balls and to surround the holes in which they rest4 ,let us take an example4 ,solitaire with #cc holes 7fig4 #hfi74 ,final solution of the single ball4 #ast ,vertical row3 #g and #ba are occupied1 and the intermediate hole #ad1 being empty1 ,i place a ring upon #ad4 #bnd ,vertical row3 ,no4 #h takes #ae1 and comes into #bb2 ,i place a ring on #bb4 #crd ,vertical row3 ,i suppress the corresponding balls1 #d-bc and #af-ca1 there now only remains #i1 so ,i place a ring on #i4 #dth ,vertical row3 ,i suppress the correspondents #aj-bi1 put #b into #ag1 and ,i place a ring upon #ag4 #eth ,vertical row3 ,i suppress correspondents #f-be1 put #cc into #ah1 and ,i place a ring upon #ah4 #fth ,vertical row3 ,no4 #ab takes #ai and comes to #bf2 ,i place a ring on #bf4 #gth ,vertical row3 ,no4 #bj is the only ball2 ,i place a ring on #bj4 7,it must be understood that these operations should be proceeded with mentally2 the balls must not be disturbed47 ,we have thus reduced the problem to seven ringed balls1 which are #ad1 #bb1 #i1 #ag1 #ah1 #bf1 and #bj which are indicated on the diagram by the line drawn through each vertically4 ,they are all comprised in the three horizontal rows1 #c1 #d1 #e4 ,illustration3 ,fig4 #hfi4--,single ball solution4 ,we can now set to work upon these three rows in the same manner as before1 considering the rings as balls4 #crd row3 ,we find 7and leave7 a ring upon #i4 #dth row3 ,the two corresponding rings1 #ag-bj1 neutralize each other1 and we suppress them4 ,we carry #ad to #ag1 and take #ag with #ah1 which comes into #af4 ,we leave a ring on #af4 #eth row3 ,carry the ring #bf to #bc1 take #bc with #bb1 which comes thus to #bd1 and we leave a ring on #bd4 ,we now have reduced our problem to three rings1 #i1 #af1 and #bd1 all in the central square1 indicated in the diagram by horizontal bars4 ,it is easy to see that #i will take #af and #bd and come into #be1 and #be will remain alone--as was intended to be done--a single ball upon the board1 indicated by the circle around it in the cut4 ,by playing the 8equivalent0 method you will always arrive at this result--a single ball in ,no4 #be4 ,it may now be perceived how we cannot only arrive at a satisfactory solution1 but by means of the rings ascertain whether we shall succeed in our game without disturbing a single ball4 ,after some experience we may even learn to dispense with the rings altogether4 ,illustration3 ,fig4 #hgj4--,solitaire board4 ,,footnotes3 #da ,from 8,la ,nature40 ,notice of ,m4 ,ch4 ,boutemps4 ,,chapter ,,lvii4 ,,the ,,magic ,,top--,,the ,,gyroscope ,,and ,,scientific ,,games ,we will not do our readers the injustice to suppose that they are not familiar with the ordinary top1--the delight of all school-boys and young people1--of which1 therefore1 we forbear giving any description2 but we now desire to give some details of the construction of the wonderful magic top4 ,it is composed of a large disc1 with an axis turning on two pivots connected with a circle of iron4 ,when in repose1 this plaything exhibits nothing of a remarkable character2 it is completely inert1 obeying1 like all other bodies1 the laws of gravity4 ,but when we come to give the disc a movement of rapid rotation1 this inert instrument seems to assume a vitality of its own if we attempt to move it2 it resists1 and seems to thrust back the hand1 and executes movements even in a contrary direction4 ,besides this1 it appears to be freed1 in a certain measure1 from the laws of gravity2 if we place it on its pivot1 instead of falling1 as it would when the disc is motionless1 it preserves the upright or inclined position in which we place it1 the upper extremity of the axis slowly describing a horizontal circle round the fulcrum of the other extremity4 ,few persons are sufficiently familiar with the theory of mechanics to understand these phenomena1 and it often happens that such a top purchased to amuse a child becomes an object of wonder and interest to his seniors4 ,we do not pretend here to explain mathematically the reason of the facts before us1 but the mechanical principle on which this top is constructed is of such great scientific importance1 that we will1 in a few words1 explain it to our readers4 ,it is sufficient to have a little knowledge of mechanics to be aware that a body in motion1 subjected to the action of a force tending to give it a directly contrary motion1 will follow a movement in a third direction1 which is termed the resultant of the two others2 and this resultant approaches nearer to one of the original directions1 in proportion as the corresponding movement is more rapid in relation to the other4 ,if1 for example1 you strike a billiard ball1 which is rolling past you1 in such a manner that you drive it regularly along in the same direction1 it appears only to obey a part of the given impulsion1 and continues its course in an oblique direction1 the speed with which it commenced rolling combining with the impulsion to produce a resultant movement4 ,if it is rolling very quickly1 and you strike it gently1 it will scarcely turn out of its course4 ,if1 on the contrary1 it is moving slowly1 and receives a violent shock1 it will run off almost exactly in the direction in which it has been struck4 ,illustration3 ,fig4 #hga4--,the magic top4 ,now that which occurs in this example of a body tending to two movements at the same time1 is also produced when it is a question of movements of rotation1 so that if a force acts upon a body in rotation in such a manner as to give it a movement of the same kind round another axis1 a third movement will be originated round a third axis1 the direction of which will be nearest to that in which the rotation is most rapid4 ,let us apply this very simple principle to our top1 and we shall see that magic has nothing whatever to do with these movements1 which at first glance appears so extraordinary4 ,having set it in motion1 we rest it on its pivot1 its axis in a horizontal position2 we then find that we have two movements before us2 first1 that which we gave the top ourselves1 and secondly1 the movement of rotation which occurs round a second axis equally horizontal passing through the fulcrum and perpendicular line to the first4 ,a movement of rotation therefore originates round a third axis placed between the two first1 but whilst the real axis of the top1 obeying this resultant movement1 takes up its new position1 the law of gravity continuing to act1 displaces and moves it a little further1 so that in endeavouring to reach its centre of gravity1 it turns round its fulcrum 7fig4 #hga74 ,from this explanation1 it will be easily seen that the more rapid the movement given to the top1--that due to gravity remaining constant1--the nearer will be the axis of the resultant movement to its real axis1 and consequently the slower will be the movement of rotation of the whole round the pivot4 ,thus this apparently incomprehensible phenomenon is easily explained by gravity1 vertical force producing a movement of rotation in a horizontal plane4 ,one can also explain by analogous reasoning1 and calculation of passive resistance1 why the axis of the top gradually inclines in proportion as the speed of the latter diminishes1 and the speed of rotation round the fulcrum increases2 why it falls immediately if an obstacle is opposed to the latter movement1 and finally1 why it produces on the hand which holds it1 movements which astonish persons so intensely who behold it for the first time4 ,the principle we have just described is often enunciated1 by saying that every body in rapid rotation rests in its plane1 and can only be driven out by a considerable force2 this1 however1 is a defective formula4 ,the principle should be stated in the following manner4 ,a body in rapid rotation tends to remain in its plane2 that is1 its axis rests parallel with itself1 and instead of obeying any force tending to divert its direction1 it produces in consequence of the combination of two simultaneous movements1 a displacement of the axis1 generally much feebler and of a different kind from that which this force exercises on the same body in repose4 ,one of the most charming applications of this theory is due to ,m4 ,foucault4 ,the ,gyroscope1 which bears his name1 is a heavy disc1 the axis of which is supported by a 8,cardan0 balance1 so that1 whatever is the position of the contrivance1 it is possible to preserve it in a constant direction4 ,therefore if the disc is1 by means of special mechanism1 put in rapid rotation1 we may give it all kinds of possible displacement without changing the plane in which the gyroscope moves4 ,supposing then that its connection with the suspension is fixed in a relatively immovable manner1 but attracted by a movement towards the ground1 the plane of rotation of the disc will not entirely participate in this movement4 ,it is true1 it will be carried into the movement of general removal1 but it will remain constantly parallel with itself1 and only appears displaced in comparison with the surrounding objects1 which obey more completely than itself the movement of the globe's rotation round its poles4 ,thus can we demonstrate the movement of our planet4 ,in virtue of the same principle1 we see every day passing before our eyes a crowd of phenomena with which we are so familiar that they do not excite our attention4 ,thus it is because the hoop tends to remain in its plane of rotation that it rolls on without falling or deviating1 and for the same reason that tops rotate vertically on their points1 or when they are running down1 describe a series of concentric circles2 and for the same reason again1 a juggler is able so easily to hold on the point of a stick a plate which he puts in rapid rotation1 etc4 ,it is also owing to this property of rotating bodies that we have been enabled to make use of cylindrical or conical projectiles in artillery4 ,the coiled riflings of the cannon causing the projectiles to turn round very rapidly1 their axis preserves an invariable direction during their whole course1 until they finally strike the object at which they are aimed4 ,without this rotation they would pirouette in an irregular manner in the air1 and besides any precision in firing being impossible1 the resistance of the air would diminish their range to an enormous extent4 ,the ,gyroscope1 an instrument now familiar to most scientific persons1 is still a problem of which the solution has not yet been found4 ,it may be called the paradox of mechanics1 for although it depends on gravitation1 it appears to be entirely indifferent to it4 ,an ,american scientist has applied electricity to the gyroscope1 so as to make its movements as continuous as possible1 and to enable us to study it more at leisure and with better results4 ,the gyroscope is mounted on a pedestal which tapers to a point1 and supports the instrument4 ,the bar of the gyroscope on which the electro-magnets are fixed rests upon the top of the pedestal4 ,one of the extremities of the bobbin is fixed to the cavity1 when the bar and support join1 the other extremity communicates with the bar which joins the nuts of the magnets4 ,an insulator of hardened caoutchouc is so placed that it just touches the axis of the wheel twice in every revolution of that wheel4 ,its plane of rotation is at right angles to the magnets1 and carries an armature of soft iron which turns very close to the magnet without touching it4 ,the armature is put en rapport with the surface of contact of the cylinder1 so that when the armature approaches it is attracted2 but immediately afterwards1 as it reaches the opposite side1 the current is interrupted1 and the impulse acquired is sufficient to move the wheel to the spot where the armature can again come under the influence of the magnet4 ,the magnets1 the wheel1 and all the parts of the instrument together can move around in any direction4 ,when two or four ,bunsen cells are put in connection with the gyroscope1 the wheel turns with tremendous rapidity1 and by permitting the magnets to work 7an operation which requires some little dexterity71 the wheel not only sustains itself1 but also the magnets and the other subjects which are between it and the extremity of the pedestal--in opposition to the laws of gravitation4 ,the wheel1 besides turning rapidly around its axis2 revolves slowly around the point of the column in the same direction taken by the lower part of the wheel4 ,when attaching the arms and counter-poise of the machine1 so that the wheel and the magnets may balance themselves exactly on the pointed pedestal1 the machine remains stationary4 ,but if we give any preponderance to the wheel and magnets the rotation of the apparatus is in a direction opposite to that which would result from turning the upper part of the wheel4 ,the gyroscope illustrates the persistence with which a body that submits to rotation maintains itself in the plane of its rotation1 notwithstanding the force of gravitation4 ,it also shows the result of the combined action of two forces tending to produce rotation around two separate axes1 which are1 however1 situated in the same plane4 ,the rotation of the wheel round its axis is produced in the present case by the electro-magnet2 and the tendency of the wheel to fall1 or to turn in a vertical plane parallel to its axis1 results in the rotation of the entire instrument upon a new axis1 which coincides with the pointed pedestal4 ,,the ,,american ,,money-,,box4 ,during a recent visit to ,london1 as ,i was one day walking in the ,crystal ,palace1 my attention was attracted by a curious money-box1 surmounted by a pictorial representation of one of the ,london streets4 ,the carriages1 horses1 and pedestrians were represented by figures cut out of cardboard1 arranged in a groove4 ,a large placard bore this inscription3 8,notice to visitors3 ,throw a penny in the money-box2 and the figures will perform40 ,i at once responded to this invitation1 and immediately beheld the little tableaux become moving and life-like2 the cabs rolled along1 and the passers-by walked up and down the street4 ,a number of visitors followed my example1 and there is no doubt the money-box was full at the end of the day4 ,this ingenious contrivance for obtaining money in so easy a manner1 and without having recourse to a 8show-man10 appeared to me worthy of investigation and description4 ,the ,scientific ,american 7,new ,york7 has recently given an explanation of this curious contrivance1 and we will here quote what has been published on the subject4 8,among the inventions intended to obtain contributions of money from the visitors at the ,philadelphia ,exhibition10 says the ,american writer1 8we will describe the singular money-boxes placed in the salons of the principal hotels and the galleries of the exhibition1 etc4 ,these contrivances all consisted of a case or box1 with a glass front1 through which can be seen a landscape in miniature1 with trees1 houses1 figures1 etc41 all cut out of cardboard1 and painted with great nicety4 ,on the box was a label requesting the visitor to drop a coin into it and await the result of the contribution4 ,when the penny has fallen in it puts in motion some hidden machinery1 and then we see the people in the miniature landscape all in motion1 riding or walking or hunting1 as the case may be40 ,another box is even more successful1 for it places in the hands of the contributor a photograph of some celebrated person4 ,but to obtain the photograph we must contribute six pennies4 ,the carte will not come out if we do not put in the proper coins1 and the apparatus is perfectly fair and honest4 ,the illustration1 fig4 #hgb1 shows the apparatus1 which is very simple4 ,on the left the ordinary box is seen1 on the right there is a longitudinal section of it4 ,at the top of the lower portion1 where the money is received in1 is a hollow support1 ,a1 which sustains the box in which the photographs are placed upon an inclined plane1 and resting against the glass4 ,the pieces of money1 in falling1 strike the extremity of a vertical balance1 which immediately turns a toothed wheel1 ,c4 ,this wheel has as many teeth as there are pieces of money necessary to purchase the photograph or carte de visite4 ,upon the escapement wheel is a ratchet arrangement1 ,d1 the shaft being moved by a cord rolled around it and attached to a spring1 ,e4 ,a bolt1 ,f1 moved by a spring1 is kept constantly pressed against the 8snail10 ,d4 ,illustration3 ,fig4 #hgb4--;,american money-box4 ,thus at each revolution1 as the parts of the machinery are animated by the same movement1 the bolt is withdrawn sufficiently to permit a carte to fall1 and then the card next following will be ready resting upon the bolt4 ,the photographs being placed upon an inclined plane1 are pushed forward by a movable frame1 ,g1 which has a roller at the base4 ,so as one card falls out another is immediately replaced close to the glass4 ,we have remarked that the wheel has six teeth1 so that as one piece of money dropped in moves it one-sixth of its revolution1 six pieces will be necessary to produce the card4 ,of course wheels can be made with one or more teeth1 and the payment may be varied for valuable objects at the desire of the possessor4 ,the invention is not only a plaything4 ,it can be made useful in the distribution of pamphlets1 or newspapers1 which can be introduced into the box folded uniformly4 ,they can also be used in omnibuses or tram-cars1 and tickets may be given by the machine on payment of the proper sum of money4 ,we will close this chapter with an illustration of a spiral bottle1 which can be done in the manner now to be described1 so that the bottle will actually become a glass spring4 ,take a mixture of #ahj grammes of lampblack1 #fj grammes of gum arabic1 #bc grammes of adraganth1 and #bc grammes of benzoin4 ,make these ingredients into a paste by the addition of water1 and fashion a pencil of the charcoal thus obtained4 ,this pencil1 when heated1 will cut the glass wherever it is applied4 ,the process is commenced by scraping the bottle with a file and following the instrument with the red-hot pencil4 ,wherever the hot pencil is applied1 the glass will be cut as shown in the illustration herewith4 ,it will be necessary to blow upon the heated pencil to maintain the incandescence as long as possible4 ,the bottle as cut and representations of the instruments are given in the cut 7fig4 #hgc74 ,illustration3 ,fig4 #hgc4 ,spiral bottle4 ,,chapter ,,lviii4 ,,scientific ,,objects ,,for ,,the ,,household4 ,illustration3 ,fig4 #hgd4--,reading wheel desk4 ,at the beginning of the seventeenth century there was at ,lyons a very remarkable mansion built by a man named ,nicholas ,grollier de ,servire4 ,this house was filled with all the most remarkable curiosities and inventions of the period4 ,the owner belonged to an ancient family4 ,his great-uncle1 ,jean ,grollier1 had amassed a magnificent library1 the best in ,france4 ,his father was also a celebrated adherent of ,henry ,,iv41 and ,m4 ,servire himself had inherited much scientific taste and intelligence from his ancestors4 ,his house was full of curiosities1 ingenious machines1 and mysterious clocks1 concerning some of which things we shall have something to say in this chapter4 ,m4 de ,servire's ingenuity was first apparent in the circular reading desk1 or wheel-desk1 on which he put all the books he was likely to require within a certain time4 ,he seated himself by this revolving desk1 and then was enabled to read any book or paper he desired by merely turning the wheel with his hands and thus bringing it under his vision4 ,in these days it is equally possible to collect useful articles either of an electric nature or otherwise4 ,we have already described the electric pen and the writing machine1 with some other things which might be included in our list of domestic appliances1 but the ,chromograph has not been yet illustrated4 ,illustration3 ,fig4 #hge4--,the chromograph4 ,,the ,,chromograph4 ,when we have written with a certain well-known violet 8ink0 upon a sheet of paper and applied it to a soft gelatinous surface and rubbed it a few times1 we shall obtain an impression of the writing on the gelatine4 ,by pressing blank sheets of paper upon this we may pull off quite a number of copies of our letter or circular4 ,this practice is now so well known that it is scarcely necessary to detail it4 ,the layer of gelatine is made up as follows1 and any of the recipes will suffice4 #a4 ,gelatine #ajj grammes1 water #cge grammes1 glycerine #cge grammes1 kaolin #ej grammes4 7,lebaigue47 #b4 ,gelatine #ajj grammes1 dextrine #ajj grammes1 glycerine #ajjj grammes1 sulphate of baryta q4s4 7,w4 ,wartha47 #c4 ,gelatine #ajj grammes1 glycerine #a1bjj grammes1 bouillie de sulphate de baryta1 strained1 #ejj cubic centimtres4 7,w4 ,wartha47 #d4 ,gelatine #a gramme1 glycerine #cj #d grammes1 water #b grammes4 7,kwaysser and ,husak47 ,illustration3 ,fig4 #hgf4--,the chromograph4 ,the 8mixture0 is shaken until it cools to the point of thickening1 and then poured into a zinc vessel4 ,the kaolin or the sulphate of baryta makes the composition white4 ,it can be treated again with gelatine and molasses employed for printing rollers4 ,when the proofs have been taken from the frame the surface may be rubbed with a damp sponge1 and then it will be ready for use again immediately4 ,the introduction of dextrine facilitates the cleansing of the surface plate4 ,,the ,,campylometer4#db ,this instrument1 constructed by ,lieutenant ,gaumet1 is very easily carried in the pocket1 and by a very simple process gives 7#a7 the length of any line1 straight or curved1 traced on a map or plan2 7#b7 the actual length corresponding to a 8graphical0 length on maps of the scale of #a_/hjjjj or #a_/ajjjjj1 or on maps which are multiples of these numbers4 ,the instrument consists of a toothed disc1 the circumference of which is dentated exactly in five centimtres4 ,the faces of this disc each carry a system of divisions2 one is divided into four parts1 the other into five4 ,the circumference of the disc 7#e centimtres7 corresponds to the #d kilomtres of the scale of #a_/hjjjj1 and to #e kilomtres of that of #a_/ajjjjj4 ,the division #a_/dj of the disc in the former scale measures #ajj mtres1 and is in it the same as #a_/ej of the other scale4 ,illustration3 ,fig4 #hgg4--,the campylometer4 ,the toothed disc moves upon a micro-metric screw1 the markings of which are #jjjae of a mtre1 and a small 8rule0 or 8reglet0 carries equal graduations1 as the screw representing lengths so follow3-- #a4 #e1 #aj1 #ae1 #bj #ej centi4 according to metric scale4 #b4 #e1 #aj1 #ae1 #bj #ej kil4 scale #a_/ajjjjj2 #c4 #d1 #h1 #ab1 #af #dj kil4 #a_/hjjjj2 ,the micro-metric screw is fixed in a frame so made as to form a kind of indicator or guide at one side4 ,to make use of the campylometer1 bring the zero of the disc opposite the zero of the rule 7reglet71 then place the instrument on the map in a perpendicular position2 the point will serve as guide1 and move the disc upon the line1 whether direct or sinuous1 of which you wish to ascertain the length4 ,when this has been done1 note the last graduation of the 8reglet0 beyond which the disc has stopped1 add to the value of this graduation the complementary length shown by the division of the disc which is opposite the 8reglet40 ,to find the length of a material line we must add to the number of centimtres shown by the upper graduation the complement in millimtres furnished by the division to the #a_/ejth4 ,for example1 suppose we read #bj upon the upper scale1 #ce the division to the #a_/ej opposite the 8reglet02 the length obtained is #bj centimtres plus #ce millimtres1 or #jbce mtres4 ,if we are measuring upon a map on the #a_/ajjjjj scale1 the upper graduations represent kilomtres1 the complementary divisions on the #a_/ej scale hundredths of mtres4 ,for example1 suppose again #bj be the superior graduation1 #ce the division to the #a_/ej of the disc as before2 the distance measured is #bj kilomtres plus #c1ejj mtres1 or #bc1ejj mtres4 ,on the map the lower graduation of the 8reglet0 is used4 ,for instance1 if #ab be the upper graduation of the division to #a_/dj of the distance opposite to the 8reglet10 the distance measured will be #ab1gjj mtres4 ,the campylometer has been specially constructed for maps on the #a_/hjjjj and #a_/ajjjjj scales1 and calculations can be made easily for any maps whose scales are multiples or sub-multiples of these4 ,but the instrument will serve equally well for all maps or plans of which the numerical scale is known4 ,we must multiply the length of the line expressed in millimtres by the denominator of the scale divided by #a1jjj4 ,so upon an ,english map to the #a_/fccfj1 a length of #aee millimtres corresponds to a 8natural0 length of #fc1cfj multiplied by #aee1 or #ihbjhj mtres4 ,thus we perceive that the employment of the campylometer does not necessitate the tracing of a graphic scale1 but only the knowledge of the numerical scale4 ,when the former only is known1 the campylometer may be used in the following manner3-- ,having traced with the disc the line you wish to measure1 carry the instrument to the zero of the scale and let it run inversely the length of that scale1 until the zero of the disc returns opposite to the zero of the 8reglet40 ,the point at which the disc is stopped on the scale indicates the length of the line measured upon the map4 ,if the scale be smaller than the line measured1 repeat the operation as many times as may be necessary4 ,if it is desirable to ascertain upon a map of a scale of #a_/bjjjj the distance represented by #a1bjj mtres1 we have only to place the toothed disc so that its position marks four times the required distance--that is1 #d1hjj mtres on the map of #a_/hjjjj 7for #d times #bj #hj74 ,then move the disc in the given direction until the zero returns opposite the zero of the 8reglet02 this limit will mark the extremity of the length required4 ,explanations are not easy upon paper1 but the instrument is found very easy in actual use4 ,it is employed by the military staff for calculating distances of any kind1 curves or straight lines4 ,on the march1 or even on horseback1 the campylometer can be employed4 ,,mysterious ,,clocks4 ,the clocks represented in the two following illustrations 7figs4 #hgh and #hgi71 are well worthy of being placed in the house of any amateur of science4 ,they are made of transparent crystal1 and though all mechanism is cleverly concealed they keep capital time4 ,the former clock 7fig4 #hgh7 is the invention of ,robert ,houdin1 and consists of two crystal discs superposed and enclosed in the same frame4 ,one carries the usual numerals1 the other moves upon its centre with the minute hand attached1 and its rotation induces by the ordinary method the movement of the hour hand4 ,the requisite motion is transmitted to the dial by gear disposed along the circumference and hidden within the metallic frame1 and is itself put in motion by clockwork1 enclosed in the pedestal of the timepiece4 ,illustration3 ,fig4 #hgh4--;,houdin's clock4 ,m4 ,cadot1 in his clock 7fig4 #hgi71 retains the plates1 but adopts the rectangular form1 so as to preclude all idea of rotation1 and to puzzle those who are acquainted with the working of ,houdin's clock4 ,the minute hand cannot1 in this instance1 be fixed to the second glass plate1 it preserves its independence4 ,this movable plate has only a very slight angular movement around its centre1 which oscillation or 8play0 is permitted in the interior of the rectangular dial4 ,a little spring movement1 hidden in the central nut of the 8hand10 provides in progressive rotation the oscillation of the transparent plate1 which cannot be perceived to move4 ,to produce this 8balance0 motion the plate is supported upon a bar in the lower part of the metal frame4 ,after the direct oscillation of which we have spoken1 a little spring puts the machinery back4 ,the direct displacement is produced by a vertical piston which raises the end of the bar4 ,this piston rests upon a bent lever communicating with a wheel with thirty triangular teeth4 ,finally this wheel turns upon its axis once in an hour by a clockwork arrangement in the pedestal of the clock4 ,each tooth takes two minutes to pass1 and the movement is communicated to the minute hand1 which thus goes round the dial in the hour4 ,the hour hand is controlled by a delicate arrangement hidden in the base4 ,the illustration and notes will explain the working4 ,illustration3 ,fig4 #hgi4--,m4 ,cadot's clock4 ,m4 ,henri ,robert has also invented a very interesting clock1 and one calculated to excite much curiosity 7fig4 #hha74 ,illustration3 ,fig4 #hhj4--a4 ,front view4 #b4 ,profile4 #c4 ,detail of movement between the glasses4 #d4 ,detail of movable plate4 a4 ,base of clock4 b4 ,framework4 c4 ,space for movement4 d4 ,wheel support4 e4 ,cogwheel4 ,we can see nothing but a crystal dial1 perfectly transparent1 upon the surface of which two 8hands0 move1 as upon an ordinary clock face4 ,there is no machinery visible1 and electricity may be credited with the motive power1 because the dial is suspended by two wires4 ,but they will soon be perceived not to be connected with the hands1 and all search for the mechanism will be fruitless4 ,the hands1 moreover1 turn backwards or forwards1 and may be moved by a treacherous finger1 but will always return as by a balanced motion to their position1 not the hour which they were at1 but to the time which it actually is4 ,they will take their proper place notwithstanding all efforts to the contrary1 and will then1 if let alone1 indicate the time as steadily as ever4 ,illustration3 ,fig4 #hha4--,m4 ,robert's clock4 ,the hands of this very mysterious timepiece carry their own motive power1 and consist of unequally balanced levers1 so to speak1 in which the clockwork arrangement is intended to disturb the equilibrium4 ,this property is employed to indicate the hour and the minute1 as we will attempt to show4 ,the minute hand is the balance1 and it is very exactly poised4 ,in the round box fitted to the end of this hand a plate of platinum is displaced by clockwork4 ,the centre of gravity being displaced every instant by the revolution of the weight which goes round once in an hour1 the minute hand is forced to follow1 and carries the hour hand with it4 ,by the hidden arrangements the hands are dependent one upon the other1 but remain independent in movement4 ,if they be moved backwards or forwards they will return automatically to their respective places1 and if turned quickly round the minute hand will return to the proper minute1 and the hour hand to the hour4 ,the mechanism is simple and ingenious2 the principle1 however1 is not absolutely novel1 and before ,m4 ,robert applied it many attempts had been made to move indicators by the machinery they themselves contained4 ,but ,m4 ,robert has succeeded in adapting the idea beneficially and usefully1 giving it a practical as well as an elegant shape4 ,a ,,new ,,calculating ,,dial4 ,illustration3 ,fig4 #hhb4--;,a new calculating dial4 ,fig4 #hhc4--,reverse view4 ,the small instrument herewith illustrated 7figs4 #hhb and #hhc7 is very serviceable for calculators1 and its size adapts it for the waistcoat pocket4 ,it can be used to calculate by addition1 subtraction1 multiplication1 and division4 ,logarithms can be found1 and the powers and roots of numbers--even trigonometrical calculations may be made by its aid4 ,we need not go into any details regarding the principle of the little 8circle40 ,such explanations are only wearying and unsatisfactory at best4 ,the principle is1 simply stated1 the theorem that the logarithm of the product of two numbers is equal to the sum of their logs4 ,the size of the dial will of course regulate the length of the calculation4 ,the instrument depicted permits of calculation to three figures with exactitude4 ,m4 ,boucher1 the inventor1 hopes to succeed in perfecting an instrument of small size which will combine all desiderata1 and calculate to high powers4 ,,the ,,pedometer4 ,we all know how useful it is to be able to calculate distances approximately when upon an excursion or walking tour1 and much trouble is taken by many tourists to ascertain the number of miles they may have walked in a certain time4 ,the rapid success which the ,pedometer has gained is a testimony to the need it has adapted itself to fill4 ,the pedometer is much like an ordinary watch in appearance and size4 ,we perceive a dial with figures and spaces to show the number of paces walked4 ,the cut represents the mechanism1 which is exceedingly simple4 ,in the fig4 #hhd1 ,b is a counter-poise at the extremity of a lever1 which oscillates around an axis1 ,a4 ,a screw1 ,v1 serves to limit the extent of these oscillations1 and a spring which acts upon the counter-poise holds the latter to the upper end4 ,the apparatus is completed by a movement which counts the number of oscillations of the lever4 ,so much being understood1 it will be presumed that if we give to the instrument an 8up-and-down0 movement1 the spring which holds the counter-poise1 ,b1 being too weak to compensate the force of inertion of the latter1 it gives way and presses against the screw1 ,v4 ,when the opposite movement takes place the counter-poise is at the end of its course1 and so on4 ,thus during a walk each step produces an oscillation which the counter registers4 ,illustration3 ,fig4 #hhd4--,pedometer4 ,in the hands of a careful observer1 such a pedometer is capable of registering exact results1 and the number of paces being counted1 a very good idea of the number of yards and miles passed over can be arrived at4 ,,footnotes3 #db ,kampulos1 a curve2 metron1 measure4 ,,chapter ,,lix4 ,,science ,,and ,,domestic ,,economy4 ,all branches of applied science are capable of giving us important hints and rendering us great service in all the conditions of our daily life1 and as we have at various times throughout this volume mentioned useful domestic inventions applicable for use by means of water1 air1 etc41 we may describe some more particularly relating to the inside of the house1 and the science of domestic economy4 ,illustration3 ,fig4 #hhe4--;,double window4 ,sometimes during the winter we may feel it very difficult1 if not impossible1 to keep the room warm4 ,this we can do1 however1 by means of double windows4 ,why is it that the double window as used in ,russia keeps out the cold so well8 ,is it because the room is defended against frost by two windows instead of there being only one to resist it8--,not entirely4 ,such an explanation is not sufficient4 ,if one be protected against the exterior cold1 it is1 thanks to the mass of air which is imprisoned1 between the two windows4 ,extraordinary as it may appear1 the air is a very bad conductor of heat1 and forms the best insulator that one can find4 ,the heat of the apartment is then perfectly retained by means of the air between the double windows4 ,in the same way the double window is not less useful during the summer1 for it prevents the entrance of the heated air into the house4 ,the double window may therefore be compared to the bournous of the ,arab and the cloak of the ,spaniard1 which preserves from heat as well as guards against cold4 ,the double windows also perform another service4 ,the glasses form a hot-house4 ,the sun heats the air which is enclosed1 and thus between the panes ferns and even vines will flourish4 ,the windows are very easy to make1 and in the event of any reader desiring to construct one or more1 we give the dimensions4 7,see fig4 #hhe47 ,t ,t1 is the exterior frame of the window4 ,the two panes are mounted on a frame of wood1 and are represented by ,a ,a and ,b ,b ,the sashes are represented apart1 ,p and ,p are the shutters of sheet iron1 which1 if the walls be not so thick as represented1 can be replaced by a spring-blind1 which descends between the windows4 ,,sewing ,,machine ,,worked ,,by ,a ,,dog4 ,animals have been employed for all time to draw carriages and the plough1 etc4 ,but these animal 8motors0 are usually employed under defective conditions1 and therefore without full profit4 ,the inert mass of the animals remains quite unutilized1 his force only is employed1 and there are many objections on the score of humanity1 as well as from a mechanical standpoint1 and great muscular tension with suffering may be inflicted upon an animal which is continually mounting a wheel or such contrivance for raising water4 ,there was in the ,paris ,exhibition a threshing machine put in motion by a horse walking upon a pair of rollers which constituted an 8endless0 way1 and we will now briefly describe a machine which utilizes animal force and weight4 ,it is the invention of ,m4 ,richard of ,paris1 who has made many mechanical apparatus for industrial purposes4 ,illustration3 ,fig4 #hhf4--,sewing machine worked by a dog4 ,the principle of the invention 7fig4 #hhf7 consists in the animal utilizing all the force resulting from his dead-weight4 ,a small box contains the dog very easily4 ,in the illustration we see the dog at rest1 and in that case he maintains his centre of gravity and exercises no force upon the wheel4 ,but when the box is inclined1 the mere weight of the animal is sufficient merely to turn the wheel in the direction of the arrows4 ,the dog1 finding himself sliding away1 naturally endeavours to move forward1 and the rotation of the wheel is continued2 the best results are obtained when the body is placed entirely upon the descending line1 and this result is owing only to the weight of the animal4 ,there is a resting-place1 just above and outside the 8endless0 way traversed by the dog4 ,a basin with water is also provided for the animal4 ,m4 ,robert was let to this discovery in the following way3--,he employs a large number of sewing-machine hands1 and finding that the working of the machines had an injurious effect upon the health of the workers1 he determined to substitute1 in part1 other labour for that of female hands4 ,he then thought out his 8quadrupedal motors10 which are worked by intelligent dogs4 ,there is very little trouble or expense connected with the working1 so a great saving is effected1 as the dogs cost little1 and are cheaply fed4 ,the result is that ,m4 ,robert has four heavy machines occasionally at work1 which are kept in motion by dogs at a very small expense4 ,a ,,clock-,,lamp4 ,illustration3 ,fig4 #hhg4--;,a clock-lamp4 ,the illustration 7fig4 #hhg7 represents an ingenious arrangement1 which1 by means of combustion of oil in a lamp1 indicates the hour of the night4 ,the design explains itself4 ,two vertical tubes are fixed above the reservoir of oil4 ,the left tube contains oil1 and is marked with the hours2 the right tube burns the oil as a lamp4 ,the apparatus is so constructed by the inventor1 ,m4 ,h4 ,behn1 that a certain quantity of oil is consumed exactly in one hour between two graduations of the hour-tube4 ,a reflector placed beside the lamp enables one to see the time by night very plainly4 ,,an 8,,alarum0 ,,lamp4 ,illustration3 ,fig4 #hhh4--;,an 8alarum0 lamp4 ,the apparatus represented below 7fig4 #hhh7 is an ordinary 8alarum0 lamp4 ,it is surmounted by a petroleum lamp1 which carries a burner that remains lighted all night1 and which serves as a night-light4 ,the 8alarum0 carries an index1 represented by the dotted lines in the illustration1 and the hands are fixed 7with the index7 to the hour you wish to rise in the morning4 ,the index is fitted with an arrangement which lets loose a vertical bar represented on the right of the figure4 ,this bar is held by a spring1 and carries a toothed rack which acts upon and raises the wick4 ,at the proper time the bar is loosed1 and the lamp-wick is raised1 diffusing a strong and sudden light through the apartment4 ,this illumination1 in concert with an alarum-bell1 generally succeeds in awaking the heaviest sleeper4 ,a ,,good ,,petroleum ,,lamp4 ,this lamp 7fig4 #hhi7 burns gazoline without the least odour or danger of explosion4 ,it will serve equally well for petroleum or naphtha4 ,the gazoline used ought to be #ffj grammes weight to the litre4 ,illustration3 ,fig4 #hhi4--;,a good petroleum lamp4 ,the central portion of the lamp under consideration has an orifice1 ,a ,b1 which extends through the upper part1 and by which the air is admitted to the centre of the flame4 ,two vertical plates divide the air-current into four portions4 ,the chimney-rest1 or gallery1 forms with the glass three concentric envelopes1 so arranged in stages that the air1 when it reaches the plates1 may be more and more carried under the flame4 ,the orifices1 a b1 carefully regulated1 give access to the exterior air4 ,including the central one1 there are four currents of air1 of which three strike against the flame4 ,these are very excellent conditions for obtaining perfect combustion1 and1 consequently1 there is an entire absence of smell and smoke1 while the light is very powerful4 ,we may add that any glass will be found suitable to this lamp1 and that1 in consequence of the separation of the hot air by the currents mentioned1 all danger of the glasses breaking from over-heating is avoided4 ,in provincial districts1 where lamp-glasses are not plentiful1 this characteristic will be appreciated4 ,the lamp can only be filled when it is extinguished1 and thus the chances of explosion are practically obviated4 ,a burner of twelve lines will give double the light of a moderator of the same capacity1 and cost only a penny or less per hour4 ,the light is perfectly still and clear4 ,a ,,new ,,tap4 ,this new tap is the invention of ,m4 ,guyonnet1 a ,frenchman4 ,the illustration 7fig4 #hij7 gives a very good idea of its construction1 and it permits the gradual release of the liquid without any of the sudden rush which ordinary taps1 or 8bungs10 are apt to do4 ,the plug is covered with indiarubber1 and follows a double curve1 which reduces the force of the liquid1 and the indiarubber removes any incrustation from the bung hole into which it may be fitted1 and closes the aperture effectively without force4 ,illustration3 ,fig4 #hij4--;,a new tap4 ,in order to guard against a contingency1 which1 however1 is an unlikely one1 the 8envelope0 7casing7 has been made in two pieces1 one of which can never be displaced2 the head only can be moved1 and it is easily detached4 ,the plug adapts itself to the aperture as a button to the buttonhole1 and only costs about three halfpence 7#ae centimes74 ,ice has no effect upon the aperture of the barrel1 thanks to the indiarubber covering of the plug4 ,so1 altogether1 such a tap will be found useful and very cheap4 ,,the ,,trapeze ,,and ,,swing4 ,we may here notice the simple trapeze and swing for children1 which can be easily fitted up in any house between two rooms4 ,the advantages of gymnastics for the young are incontestable1 but practically there are difficulties in the way1 particularly for those living in towns1 but a skilful ,american has solved the problem in an ingenious way4 ,he has found means to suspend the trapeze and a swing between the doorposts of a room without nails or any unsightly wood supports4 ,the trapeze is simply suspended as represented in the accompanying illustrations4 ,illustration3 ,fig4 #hia4--,the house swing4 ,illustration3 ,fig4 #hib4--,the house trapeze4 ,the bar1 ,b 7see fig4 #hib71 is of wood1 terminating in screws enclosed in the grooves of the wood1 at the extremity of which indiarubber discs are fixed 7,c and ,c74 ,when the bar is placed between the side posts of the open door and with the indiarubber in contact with the sides1 the bar1 ,b1 is vigorously screwed in the direction of the arrow1 and this motion is transmitted to the indiarubber discs which press against the door1 and the apparatus remains fixed4 ,the trapeze cords1 or the swing ropes1 can be fastened to the bar with hooks1 as shown in the illustration1 and the solidity and safety of the bar may be tested by putting heavy weights upon the ropes before venturing upon the swing1 or trapeze4 ,even violent exercises may be indulged in without any fear of falling if the bar be firmly screwed against the sides of the door4 ,,simple ,,toys4 ,the accompanying illustration shows us a circlet of paper1 very thin1 fastened upon a frame1 with paper wings fixed to the radii4 ,this 8screw0 fashioned wings and the circlet can be kept up in the air by means of a hand screen4 ,the effect will be observable in the rapid revolution of the little paper wheel1 which must be very light and thin4 7,see fig4 #hic47 ,illustration3 ,fig4 #hic4--,the paper wheel4 ,there are many toys which can be controlled by the use of indiarubber springs4 ,the bicyclist in the cut 7fig4 #hid7 is an instance in point4 ,he turns around a pivot1 and the tension of the spring keeps the machine in its place4 ,illustration3 ,fig4 #hid4--,the bicycle toy4 ,the swimming-fish 7fig4 #hie7 is moved by an indiarubber spring1 much as the drawing-room kite is elevated in the air4 ,the spring of indiarubber is twisted to make the fish swim1 and the caoutchouc is adapted to a toothed wheel which has a clock-work motion that gives the tail a motion sideways and round1 acting like a propeller1 and thus the fish swims4 ,illustration3 ,fig4 #hie4--,the fish4 ,it is perhaps as well to say how these fish are managed1 because then children will not break them1 when they have been purchased1 to see what is inside4 ,very young students are very fond of analyses of this nature1 but synthesis1 or putting together1 is a far superior occupation in these circumstances to analysis1 and to put together more lawful than to pull asunder4 ,,tree-,,felling ,,by ,,steam4 ,the machine constructed a few years ago by ,messrs4 ,ransome1 and which was tried at ,roupell ,park1 near ,london1 seems to combine all the desiderata in the matter of mechanical tree-felling4 ,many experiments have been previously made by people to cut down trees by means of steam machinery1 but none of them included all the conditions necessary for success4 ,the ,ransome ,machine cut down four large trees in forty minutes4 ,illustration3 ,fig4 #hif4--,ransome's tree-felling machine4 ,the apparatus1 as shown in the illustration1 is not unlike1 in appearance1 the perforating machines employed in boring rocks1 in which the drill is replaced by a saw4 ,the cylinder is small1 and works at high pressure2 a piston moves the saw in a guide-frame4 ,the machine is firmly fixed against the tree1 and the support is fastened by a chain4 ,a rack arrangement provides for the turning of the machine as the saw continues to cut its way through the trunk of the tree4 ,the weight is not excessive1 and the necessary steam is supplied by a portable furnace and boiler1 which communicates with the saw-motion by a flexible tube4 ,the saw can cut through a horizontal as well as through a perpendicular trunk--thus timber can be rapidly cut up4 ,another ingenious sawing machine is that invented by ,mr4 ,w4 ,w4 ,giles1 of ,chicago1 ,united ,states1 ,america4 ,this apparatus is about eight feet long1 and one extremity is fixed to the trunk of the tree to be operated on4 ,illustration3 ,fig4 #hig4--,sawing machine4 ,the operator sits upon a ledge or saddle at the opposite end1 and putting his feet upon the treadles1 pushes them and the saw forward2 this movement is assisted by the weight of the hands on the lever4 ,the saw1 under these circumstances1 cuts into the wood with great force1 and when the operator pushes the lever forward he brings the force of his legs to bear at the same time1 and carries the saw back again4 ,so feet1 hands1 dead weight with the saw itself1 combine at once upon the tree1 and the blade quickly does its work4 ,the saw is three feet long and is very easily manipulated4 ,a ,,way ,,of ,,preserving ,,grapes4 ,remarkable progress has been made of late years in the conservation of various articles of food1 and we may here speak of the preservation of the grape4 ,we will first mention ,m4 ,r4 ,charmoux's method1 which is called the 8,fresh ,grape0 system4 ,the portion of the building used for the business is on the first floor1 as nearly as possible in the centre of the building1 so as to be guarded from damp4 ,two windows are sufficient for all purposes1 one to the north1 and one to the south4 ,they may be merely kept shut on ordinary occasions1 but when frost comes they must be draped and 8packed0 with nets filled with moss or dried seaweed4 ,the principal one of the windows is to admit of the cleansing of the room and for the admission of air in the summer time1 when there are not many grapes left4 ,illustration3 ,fig4 #hih4--;,grape preserving4 ,in winter the apartment may be warmed by hot air1 and if this cannot be managed the ordinary means must be resorted to to keep up the temperature4 ,the upper clusters of grapes should first be picked1 for shade conduces to longevity of the fruit1 and the #bjth ,october is about the time to commence4 ,a fine day should be chosen2 a cloudy day will suit provided there is no dew or dampness in the air4 ,the finest bunches are cut first1 and care must be taken to separate them at the end of the stalk1 having three 8eyes0 under the grape and two above it4 ,the leaves should be at once cut off1 and the grapes put with great caution into boxes or baskets to be taken to the preserving house1 where each stalk is plunged into a phial holding about #abe grammes of water1 into which1 two or three days previously1 a teaspoonful of wood charcoal has been put4 ,illustration3 ,fig4 #hii4--;,hanging the grapes4 ,the phials are suspended as shown in the accompanying illustration 7fig4 #hii71 and then certain precautions must be observed3 they must not be disturbed1 nor must any draught be admitted1 as the temperature must not descend below #a to #b cent4 ,there is no necessity to change the water in the bottles2 very little will evaporate between ,november and ,may1 when the process ought to be finished1 but the phials must neither be corked nor concealed4 ,in the dry process the same house can be used1 and stagings are employed4 ,these frames are furnished with grooved boxes inclined towards each other1 and lined with very dry fern-leaves or straw 7fig4 #ijj74 ,some days after the phials have been filled cut the grapes successively at the first time1 which generally begins about the #fth to the #abth of ,november4 ,the grapes are then put in baskets and carefully carried to the preserving room1 where they are ranged in the boxes so as not to touch4 ,each box contains about six kilogrammes of grapes4 ,illustration3 ,fig4 #ijj4--;,drying process4 ,all the time of the conservation process care must be taken to eradicate all grapes which change colour or alter in any way4 ,if dampness be feared have a lighted stove in the room for a time4 ,grapes are also preserved en espalier1 but not so well4 ,sometimes a mouldy smell will be perceived in the room2 to prevent this ventilators should be placed in the ceiling1 which must1 however1 never be opened until the mouldy smell renders such a proceeding absolutely necessary4 ,,chapter ,,lx4 ,,some ,,curious ,,modes ,,of ,,transit4 ,we have already noticed some novel means of locomotion in the water and in the air1 and now a few of the means whereby locomotion is attained as a recreation or as an exhibition may be mentioned4 ,illustration3 ,fig4 #ija4--,new car4 ,for instance1 here is a very curious vehicle1 and the explanation of it we give in the words of the anonymous inventor3-- 8,my vehicle will carry four people without counting the driver4 ,it is strong1 easy to draw1 and can turn in a horse's length4 ,the driver completely controls the animal1 and no dust is thrown up to inconvenience the sitters1 for by the time it rises the car is well in advance of it4 ,it is cheap2 the harness is simple and safe4 ,the horse is sheltered from heat and rain and flies4 ,if he should fall1 there is no more than ordinary danger to life and limb than if he fell in a carriage2 and1 last of all1 no very showy animal is needed1 so long as his wind is sound1 and his legs and tail respectable4 ,travellers in this 8trap0 can sit in any position1 back to back1 or face to face1 two and two4 ,the weight is all near the collar1 and the animal is under control most perfectly4 ,illustration3 ,fig4 #ijb4--,side view of vehicle4 8,the estimated cost is #dj2 the horse about #dj1 or less2 harness 7say71 #g1 which contrasts favourably with the expenses of an ordinary one horse vehicle40 ,,endless ,,rails4 ,these adjuncts to locomotion can be adapted to any kind of vehicle1 and are in pieces about two feet long1 articulated1 and resting upon a base to give the necessary stability4 ,the endless rail entirely envelopes the wheels all along the train1 and the right and left rails are quite independent of each other1 and as the vehicles advance the rails are put down and raised again when the carriages have passed4 ,in front there are two distributing wheels governed by the tractive power1 so that as the engine1 or the animal drawing the train turns aside1 the rails are still laid down parallel as before1 but the hind wheels will not permit of very sharp curves4 ,there are wheels also at the rear of the train1 and as on curves one wheel will pass over more rail than another1 and in the hinder wheels a differential arrangement is used1 and when one goes back the other advances as much1 and so the relative distance is kept up1 for the rail does not alter in length at all4 ,the wheels have double flanges to retain them on the line4 ,illustration3 ,fig4 #ijc4--;,endless rails4 ,the system1 considered from a mechanical point of view1 gives striking results1 and very little effort is required to put the train in motion4 ,the resistance is very small1 and much greater weights can1 of course1 be transported upon the endless rail than upon the ordinary road4 ,the experiment has been tried in the ,tuilleries ,gardens in ,paris4 ,three carriages filled with children are drawn by two goats without any fatigue1 and in the ordinary goat carriages at least twelve of the animals would be necessary--that is1 four to each carriage4 ,the economy of this mode of transport is therefore incontestable4 ,the usual rate is about three-and-a-half to four miles an hour1 so it is not adapted for travellers1 but for merchandise4 ,the system might be applied to numerous vehicles on all kinds of roads for horses and oxen1 in mines and factories1 and in colonial plantations4 ,m4 ,ader1 the inventor1 intended the system to be applied in the ,landes1 where the rails would lie close upon the sandy soil1 and the expense of 8metalling0 roads would be entirely done away with4 ,the adoption of the endless rail method of conveyance would prove a fortune to the ,landes1 where pine forests abound1 and the wood and resin which is lost for want of transport could be removed and sold to advantage4 ,the endless rail may also be used upon the ordinary road in places where the highways are out of repair4 ,illustration3 ,fig4 #ijd4--,the ,nina4 ,,the ,,smallest ,,steamboat ,,in ,,the ,,world4 ,the picture 7fig4 #ijd7 shows us the ,nina1 the tiniest steamer afloat4 ,the keel is somewhat over twelve feet in length1 and about three feet wide1 the depth of water ten inches4 ,a speed of about five-and-a-half miles an hour can be obtained with a pressure of one hundred pounds4 ,it is a twin-screw 8ship0 with propellers of three blades4 ,the ,nina was built on the lines of the ,nautilus1 of cedar and oak1 and coppered4 ,it is stated to be a marvel of solidity and lightness4 ,the chimney is movable1 and can be lowered at pleasure if a bridge be too low4 ,there is ample room for provisions for the occupant in a frame which can be attached to the sides or fixed astern4 ,the boat is easily carried in sections1 and can be transported easily from place to place4 ,the weights of the various portions are as follows3--,the hull #ij lb41 boiler #hj lb41 engine #be lb41 machinery #bj lb42 total1 #bae lb4 ,forty pounds of good charcoal can be packed into the sides of the boat in racks4 ,the rudder can be so connected by wires that the feet will perform the function of steering1 thus leaving the hands free to attend to the engine1 so the occupant is perfectly at liberty to go where and how he pleases4 ,illustration3 ,fig4 #ije4--;,an old chaise4 ,for river navigation or calm sea-steaming the ,nina is admirably adapted1 and any one who can be stoker1 steersman1 and engineer1 as well as passenger and crew1 will enjoy a trip in such a boat4 ,such a steamer costs about #bej1 but it might be less4 ,it may be added that the ,nina has uniformly behaved well1 and was built by ,fordham of ,new ,york4 ,a ,,mechanical ,,carriage4 ,a distinguished savant of the seventeenth century1 ,ozanam by name1 a member of the ,academy of ,science1 gave in #afic a curious description of a mechanical carriage1 which may perhaps be regarded as the parent of the velocipede and the bicycle4 ,we here reproduce the engravings from ,ozanam's work and his words4 8,some years ago10 wrote the philosopher in #afic1 8there may have been seen in ,paris a chaise10 as in the picture1 8and which a servant1 by pressing alternately upon treadles0 7as in the detail71 8caused to progress by turning two small wheels hidden in a frame between the hinder pair of wheels of the chaise4 ,the description ,i give as ,i received it from ,m4 ,richard1 the doctor of ,rochelle4 8,a ,a is a roller attached to the box behind the vehicle1 ,b is a pulley1 over which the cord that works with the treadles passes2 ,c and ,d are the treadles1 with pedals1 ,f ,f4 ,the wheels1 ,h ,h1 being thus put in motion1 the large wheels are moved1 and when the hind wheels move forward1 the foremost ones must advance also1 and the sitter has only to guide the machine by the reins he holds attached to the guiding axle40 ,illustration3 ,fig4 #ijf4--,the movement4 ,,the ,,end4 ,,index4 ,aberration1 ,chromatic1 #ajd4 0 of sphericity1 #aje4 ,absorption of light1 #ie4 ,acid1 ,acetic1 #daa4 0 ,citric1 #dad4 0 ,formic1 #dae4 0 ,lactic1 #dae4 0 ,malic1 #dad4 0 ,oxalic1 #dad4 0 ,tannic1 #dad4 0 ,tartaric1 #dad4 ,acoustics1 ,instruments for1 #ahj4 0 ,the science of1 #aff4 ,actinozoa1 ,the1 #gaj4 ,action and reaction1 #ce4 0 ,catalytic1 #cbh4 0 ,electro-chemical1 #bbj4 ,adhesion of fluids1 #be4 ,aerolites1 ,meteorites or1 #dic4 ,age1 ,the great ice1 #eie4 ,agricultural1 ,science in1 #g4 ,air1 ,composition of1 #cdj4 0 ,composition of the1 #de4 0 ,as motive power1 #eg4 0 ,experiments with1 #de4 0 ,movement by heat1 #hb4 0 ,pressure of1 in bodies1 #bib4 0 0 on mountains1 #ee4 0 0 the1 #de4 0 ,science in open1 #f4 0 ,weight of the1 #ej4 0 pump1 ,experiments1 #de4 0 0 ,description1 #ea4 0 0 ,sprengel's1 #ea4 ,alarum lamp1 ,a new1 #gfj4 ,albumen1 #dbb4 ,alchemists1 ,celebrated1 #ccf4 ,alchemy1 #ccf4 ,alcoholic thermometers1 #hj4 ,alcohol1 #dai4 ,alembic1 ,the1 #ceg4 ,alg1 ,mosses and1 #fhh4 ,alkali1 ,definition of an1 #caj4 ,alphabets1 ,telegraphic1 #bch1 #bda4 ,alps1 ,electric clouds in the1 #bia4 ,alum1 #ddj4 ,aluminum1 #cic1 #dci4 ,amber1 #dba4 ,ameb1 ,the1 #gje4 ,ammonia1 ,uses of1 #cfa4 ,ammonite1 #ah4 ,ammonium1 #cic1 #dcg4 0 never found1 #cfe4 ,amorphous crystals1 #dca4 ,ansthetic1 ,a new1 #ac4 ,analysis of chance1 #gbf4 0 ,spectrum1 #ade4 ,anamorphoses1 #ace4 ,anatomy of the eye1 #ajb4 ,anemones1 ,sea1 #gaj4 ,angles1 how to measure1 #dgd4 ,animal electricity1 #bhc4 ,animals1 ,classifications of1 #gja4 0 ,vertebrate1 etc41 #gjj4 ,annelid1 ,the1 #gad4 ,annulosa1 ,the1 #gad4 ,anthelion1 ,an1 #cjj4 ,antimony1 ,uses of1 #djd1 #ddf4 ,apparatus for ,botanists1 #ag4 0 ,geologists1 #ag4 0 ,mineralogists1 #ag4 ,appliances1 ,astronomical1 #eeg4 ,aqua regia1 #cbe4 ,aquarium1 ,a home-made1 #i4 ,aquarius constellation1 #edj4 ,aquatic experiments1 #i4 ,arachnida1 ,the1 #gbc4 ,arc1 ,voltaic1 #bbc4 ,archimedes1 ,principle of1 #fh4 0 ,story of1 #fh4 ,areometer1 ,use of the1 #bg4 ,aries1 ,constellation1 #ecf4 ,arsenic1 #chf1 #ddf4 ,artesian wells1 #fjd4 ,ascents1 ,celebrated balloon1 #cja4 ,ascent1 ,gay-,lussac's1 #bih4 ,astatic galvanometer1 ,the1 #bbg4 ,asteroids1 ,the1 #ebg4 ,astra1 ,discovery of1 #ebh4 ,astronomers1 ,celebrated1 #dfh4 ,astrology1 ,early practice of1 #dfg4 ,astronomy1 ,definition of1 #dff4 0 ,history of1 #dff4 0 ,terms used in1 #dga4 ,atmosphere1 ,composition of1 #cdj4 0 the same1 #fbh4 ,atmospheric boat1 ,the1 #deb4 0 electricity1 #bhc4 ,atom1 ,definition of an1 #cji4 ,atomic or combining weight1 #cji4 0 theory1 ,the1 #cji4 ,attraction1 ,capillary1 #be1 #fd4 0 ,chemical1 #be4 0 ,molecular1 #fe4 0 of cohesion1 #bd4 ,audiphone1 ,the1 #ahe4 0 ,uses of the1 #ahe4 ,augites1 #dci4 ,aurora borealis1 ,cause of1 #fdf4 ,autophone1 ,principle of1 #ahd4 0 ,use of the1 #ahc4 ,axis1 ,floral1 #fgi4 ,azimuth compass1 ,the1 #bfj4 ,azote1 #cei4 ,balance1 ,chemists'1 #bf4 0 ,hydrostatic1 #bf4 0 ,laws of1 #be4 ,balard1 ,experiments of1 #bg4 ,ballooning1 ,sensational1 #cjb4 ,balloons1 ,accidents to1 #big4 0 ,early ascents in1 #bif4 0 ,endeavours to steer1 #cjf4 0 ,filling1 #cje4 0 ,principle of1 #cje4 ,band1 ,a phantom1 #aif4 ,barium1 #cic4 ,barometer1 ,aneroid1 ,the1 #ec4 0 ,glycerine1 ,the1 #ed4 0 ,pascal's1 #eb4 0 ,weather forecasts1 #feb4 ,barometers1 ,various1 #ec4 ,barytes1 #cic1 #dch4 ,bases1 ,definitions of1 #caj1 #dae4 ,batteries1 ,different galvanic1 #bbb4 ,battery1 electric1 ,description1 #bjh4 ,beaches1 ,mirage on1 #ah4 ,bear1 ,the ,great1 #edb4 ,bell1 diving1 ,the1 described1 #ef4 ,bernard ,palissy1 ,saying of1 #a4 ,bessemer process1 ,the1 #cii4 ,bicyclist1 ,a toy1 #gfe4 ,binocular vision1 #ada4 ,biology1 ,meaning of1 #feh4 ,bird1 ,m4 ,tatin's artificial1 #dea4 ,birds1 ,mechanical1 #ddi4 ,blue ,john1 #cie4 0 ,lias1 ,the1 #ehf4 ,boat1 ,atmospheric1 #deb4 ,bores1 or tidal waves1 #fac4 ,boron1 #chf4 0 ,mineral nature of1 #dce4 0,boss0 puzzle1 ,the1 #gca4 ,botanists1 ,apparatus for1 #ag4 ,botany1 ,introduction to1 #feg4 ,boxes1 ,scientific money1 #gde4 ,breezes1 ,sea and land1 #fcj4 ,british ,isles1 ,date of the1 #eic4 ,bromine1 where found1 #cfg4 ,bronze ,age1 ,the1 #eih4 ,bulb1 ,what is a1 #ffg4 0 ,wollaston's1 #ia4 ,bullets formed by electricity1 #bfd4 ,bunter formation1 ,the1 #ehe4 ,buoyancy of water1 ,the1 #fg4 ,burglar-detector1 ,a new1 #aie4 ,butterflies1 ,capture of1 #af4 ,cabinets1 ,optical1 #ih4 ,cadot's clock1 #geb4 ,csum1 #cic4 ,calamine1 #djc4 ,calcium1 #cic1 #dcg4 ,calculation1 ,machine for1 #gee4 ,caloric1 ,theory of1 #gb4 ,calyx1 ,the1 #fge4 ,cambrian system1 #ege4 ,camera obscura1 ,the1 #adj4 0 photographic1 ,the1 #aea4 ,camphor1 #dba4 ,campylometer1 ,construction1 #gej4 0 ,use of the1 #gdi4 ,cancer1 ,constellation1 #ech4 ,candle1 ,the burning of1 #aee4 ,capillarity1 #be4 0 ,description of1 #fd1 #be4 ,capillary attraction1 #fd1 #be4 ,capricornus1 ,constellation1 #eci4 ,carbon1 ,importance of1 #cfh4 0 ,mineral nature of1 #dce4 ,carbonic acid1 #cdc4 0 ,danger of1 #cgd4 ,carboniferous formation1 ,the1 #egh4 ,carbonization1 ,slow1 #dbc4 ,card1 to perforate by electricity1 #bae4 ,caseine1 #dbb4 ,castelli1 ,experiment of1 #gh4 ,catalepsy1 ,how to induce1 #ab4 0 in fowls1 #ab4 ,cataleptic fowl1 ,the1 #ab4 ,cell1 ,a botanical1 #ffa4 ,cells1 ,animal1 #gjd4 0 ,plant1 #ffa4 ,cellular tissues1 #ffa4 ,cementation1 #cih4 ,centre of ,gravity1 #be4 0 magnitude1 #cd4 0 parallel forces1 #cd4 ,centrifugal force1 #dc4 ,cephalopods1 #gbe4 ,ceres1 ,discovery of1 #ebh4 ,chalk1 ,fossils of the1 #ehi4 ,chance1 ,analysis of1 #gbf4 ,chemical attraction1 #be4 ,chemistry1 ,early history of1 #ccf4 0 ,introduction to1 #cjg4 0 ,organic1 #daj4 0 ,sleight of hand and1 #cce4 0 ,the science of1 #bb4 0 without a laboratory1 #cac4 ,children11 ,simply-made toys for1 #gfd4 0 ,trapeze and swing for1 #gfc4 ,chladni's figures1 #aie4 ,chlorine1 #cff4 0 ,uses of1 #cfg4 ,chloroform1 ,use of1 #dbj4 ,chlorophane1 #ccc4 ,chlorophyl1 ,definition of1 #ffj4 ,chromatic aberration1 #ajd4 ,chromosphere1 ,the sun's1 #dii4 ,chromium1 #djd1 #ddf4 ,chromograph1 ,the1 #gdh4 ,chronograph1 ,the1 #dgh4 ,chronometers1 ,solar1 ,use of1 #efc4 ,circles1 ,optical illusions with1 #aca4 ,circulating fountain1 ,the1 #ded4 ,cirripeds1 ,the1 #gbc4 ,classification of animals1 #gja4 0 plants1 #fid4 ,clay1 ,uses of1 #cba4 ,cleavage attribute of minerals1 #dcb4 ,clepsydra1 ,the1 #dgi4 ,climate1 ,differences in1 #fec4 0 ,meaning of the term1 #feb4 ,climatology1 #fea4 ,clock1 ,a cosmographical1 #eei4 0 ,cadot's1 #geb4 0 ,houdin's1 #geb4 0 ,roberts'1 #gec4 ,clock-lamp1 ,a1 #gei4 ,clocks1 ,ancient1 #dgi4 0 ,mysterious1 #geb4 0 ,watches and1 #dgi4 ,clouds1 ,causes of1 #fcd4 0 ,classification of1 #fce4 0 ,electricity in1 #bhg4 0 ,vapour and1 #fcd4 ,coal1 ,formation of1 #cge4 ,coal found in basins1 #eha4 0 measures1 ,animal life of1 #egh4 0 period1 ,plants of the1 #hj4 ,cobalt1 ,nickle and1 #dja1 #dde4 ,cock1 ,a cataleptic1 #ab4 ,cohesion attribute of minerals1 #dca4 0 ,attraction of1 #bd4 ,coke ovens1 #cgj4 ,coleoptera1 ,the1 #gbj4 ,collection of insects1 #h4 ,colouring of flowers1 ,artificial1 #cbi4 ,colours1 ,star1 #edh4 ,coma1 #daf4 ,combustion1 #cde4 ,comets1 ,celebrated1 #dib4 0 distinguished by1 #dia4 ,commutator1 ,the1 #bcf4 ,compass1 ,azumith1 ,the1 #bfj4 0 ,invention of the1 #bei4 0 ,mariners'1 ,to make1 #bja4 0 ,ordinary form of the1 #bei4 ,compensation in optics1 #acb4 ,composition of the atmosphere1 #cdj4 ,conduction of electricity1 #bjb4 ,conductors1 electric1 ,list of1 #baj4 0 ,heat1 #hi4 ,constellations1 ,northern1 #eda4 0 ,southern1 #edc4 0 ,the chief1 #ecf4 ,copper1 #dja1 #dde4 ,coral insect1 ,the1 #fbj4 0 islands1 #fai4 ,corals1 #gaj4 ,cords1 ,knots1 and puzzles1 #gge4 ,corolla1 ,the1 #fge4 ,cost of light1 #aja4 ,crabs1 #gbc4 0 ,hermit1 #gbc4 ,crust1 ,the earth's1 #eff4 ,crustacea1 ,the1 #gbb4 ,crystallization1 ,instantaneous1 #cai4 ,crystallography1 #dbd4 0 ,the study of1 #dbg4 ,crystals1 ,definition of term1 #dbf4 0 ,forms of1 #dbg4 0 ,systems of1 #dbg1 et4 seq4 ,cucumbers1 ,sea1 #gad4 ,cups1 ,volta's crown of1 #bbj4 ,curiosity1 ,the age of1 #h4 ,currents1 ,air1 winds1 and1 #fbi4 ,curves1 ,various sound1 #agf4 ,cyanogen1 #cgh4 ,daguerreotypes described1 #aeb4 ,dark spot1 ,the1 #acd4 ,dazzling top1 ,the1 #abh4 ,dead ,sea1 ,drowning in the1 #fg4 ,decomposition1 #dbc4 ,definition of physics1 #bb4 ,definitions1 ,scientific1 #d4 ,density1 ,laws about1 #bd4 ,despatch1 ,the pneumatic1 #eg4 ,devonian system1 #egf4 ,dew1 ,hail and1 #fda4 ,diamonds1 ,cutting of1 #cfi4 ,dip1 ,magnetic1 #bef4 ,discharges1 ,electric1 #bad4 ,discoveries1 ,astronomical1 #dfh4 ,discs1 ,rotating use of1 #ajh4 ,distances1 ,measurement of1 #dhb4 ,distillation1 ,sublimation and1 #hf4 ,dogs1 ,new work for1 #geh4 ,double stars1 ,list of1 #edg4 ,dress1 ,boyton's swimming1 #dfj4 ,drops1 ,prince ,rupert's1 #ha4 ,drummond light1 ,the1 #afj4 ,dunes1 ,history of the1 #fae4 ,dyes1 ,hair1 #cbf4 ,ear1 ,anatomy of the1 #aff4 ,earth1 ,constitution of the1 #efh4 0 ,crust of the1 #eff4 0 ,facts about the1 #ejh4 0 ,formation of the1 #eff4 0 ,form of the1 #ejd4 0 ,latitude and longitude of1 #ejd4 0 ,motion of the1 #ejd4 0 ,rate of motion of the1 #ejd4 0 ,stoppage of the1 #ejg4 0 ,track of the1 #ejf4 ,earthquakes1 ,motion of1 #fbc4 0 ,volcanoes and1 #fbj4 ,ebullition1 #hc4 0 ,temperature for1 #hc4 ,echo1 ,causes of1 #aga4 0 ,definition of an1 #aga4 ,eclipses1 ,causes of1 #eah4 0 ,lunar1 #eai4 0 ,solar1 #eai4 ,ecliptic1 ,the1 #dig4 ,egg1 electric1 ,the1 #bad4 ,elasticity1 ,motion by1 #cf4 ,electric egg1 ,the1 #bad4 0 light1 ,how to produce1 #bfe4 0 machine1 ,to make an1 #bjg4 0 pen1 ,the1 #bdh4 0 toys1 #bgi4 ,electricity a mystery1 #aig4 0 ,animal and other1 #bhb4 0 ,conduction of1 #bjb4 0 decomposes water1 #bbf4 0 ,derivation of1 #aig4 0 ,domestic lighting by1 #bga4 0 in clouds1 #bhg4 0 in medicine1 #bcj4 0 ,negative and positive1 #bjc4 0 ,novel applications of1 #bej4 0 not to be played with1 #bje4 0 ,static and dynamic1 #bji4 0 ,velocity of1 #bab4 ,electro-magnetism1 #bee1 #bfj4 ,electro-motograph1 ,the1 #bfb4 ,electroplating1 #bbg4 ,electrotyping1 #bbi4 ,electrodes1 ,poles or1 #bba4 ,electrolysis1 #bbf4 ,electrometer1 ,torsion1 ,the1 #bji4 ,electrophorus1 ,how to make1 #aih4 0 ,peiffer's1 #bgi4 ,electroscope1 ,to make an1 #bjf4 ,elements1 ,definition of the1 #cjg4 0 ,electrical relation1 #daj4 0 ,phial of the four1 #dg4 0 ,table of the1 #cjh4 ,emulsion process1 ,the1 #aec4 ,encrinites1 ,the1 #gac4 ,endless rails1 ,use of1 #gga4 ,endogens1 ,enogens and1 #ffe4 ,endosmose1 #ffc1 #fib4 ,energy changed into heat1 #ia4 ,entozoa1 ,the1 #gaf4 ,eocene formation1 ,the1 #eia4 ,epidermis of plants1 #ffd4 ,epsom salts1 #cie4 ,equator1 ,magnetic1 #bef4 ,equilibrium1 ,laws of1 #bh4 ,equatorial1 ,the1 #dgh4 ,equinoctial1 ,the1 #die4 ,equinoxes1 ,precession of the1 #dig4 0 ,solstices and1 #dif4 ,eruption1 ,signs of an1 #fba4 ,estimation1 ocular1 ,illusions of1 #aaf4 ,ether1 #dai4 0 ,stillness of1 #afh4 0 ,the nature of1 #ic4 ,eudrometer1 ,use of the1 #cec4 ,europe1 ,geological date of1 #eic4 ,eusthenes1 ,experiment by1 #ch4 ,evaporation defined1 #hc4 0 ,laws of1 #hd4 ,exogens1 ,endogens and1 #ffe4 ,experiments1 ,some of ,edison's1 #bfi4 ,eye1 ,accommodation in the1 #ajc4 0 ,light in the1 #adb4 0 ,the1 an optical instrument1 #ajb4 ,faculae1 what they are1 #dih4 ,fata ,morgana1 ,the1 #fdi4 ,felspars1 #ddb4 ,fertilization of plants1 #fhb4 ,fibrine1 #dbb4 ,figures1 ,chladni's1 #aie4 ,fiords1 ,norwegian1 #fae4 ,fire1 ,green1 #cic4 0 ,red1 #cie4 ,fish1 ,a fossil1 #egg4 0 ,electric1 #bhd4 0 ,magic1 #bha4 0 ,new swimming toy1 #gfe4 0 ,star1 #gac4 ,fishes1 how they breathe1 #ceh4 ,fixed stars1 ,the1 #ece4 ,flames1 ,sensitive1 #aie4 0 ,singing1 #aie4 ,flowers1 artificial1 ,colouring of1 #cbi4 0 what are they1 #fge4 ,fluorine1 #cfh4 ,flying1 ,earliest attempts at1 #bid4 ,foraminifera1 ,the1 #gje4 ,force1 ,centrifugal1 #dc4 0 ,definition of a1 #d4 ,forces1 ,natural1 #bb4 0 ,parallel centre of1 #cd4 ,formation1 ,carboniferous1 #egh4 0 ,eocene1 #eia4 0 ,jurassic1 #ehf4 0 ,lias1 #ehf4 0 ,maestricht1 #eij4 0 ,miocene1 #eic4 0 ,oolite1 #ehf4 0 ,permian1 #ehb4 0 ,trias1 #ehe4 0 ,wealden1 #ehh4 ,fountain1 ,circulating1 #dec4 ,fracture1 attribute of minerals1 #dcc4 ,franklin1 ,experiments of1 #bje4 ,fraunhofer1 ,discovery of1 #adc4 ,freezing machinery1 #cfc4 0 mixtures1 #hi4 ,friction1 ,definition of1 #dj4 0 ,inertia and1 #ce1 et sq4 ,frogs1 ,electrified1 #bag4 0 ,tree1 #aa4 ,fruit1 ,definition of1 #fhd4 0 ,how formed1 #fhc4 ,fruits produced by one carpel1 #fhe4 0 0 several1 #fhe4 ,fulgarites1 #fdd4 ,fungi1 #fij4 0 ,destructive1 #fij4 0 ,edible1 #fia4 0 ,propagation of the1 #fib4 ,fusee1 ,the1 #dha4 ,fusion1 ,definition of1 #hh4 ,future ages1 ,the1 #eii4 ,galaxy1 ,the1 #eec4 ,galena1 ,use of1 #dja4 ,galileo1 ,tube of1 #adh4 ,galleries1 ,whispering1 #agb4 ,galvani1 defeated by ,volta1 #bah4 0 ,discovery of1 #bag4 ,galvanometer1 ,astatic1 #bbg4 0 ,pungent1 #bbg4 0 1 ,use of the1 #bbc4 ,galvanoscope1 ,the1 #bbg4 ,game1 ,the needle1 #gbi4 ,games1 ,mathematical1 #gbf4 ,garnets1 ,mineral nature of1 #ddb4 ,gas1 ,coal1 #cge4 0 companies' profits1 #cgg4 0 ,definition of1 #d4 0 harmonicon1 ,the1 #cea4 0 ,laughing1 #cfa4 0 ,marsh1 #cdg4 ,gases1 ,liquids and1 #dd4 ,gauges1 ,rain1 #fch4 ,gazogene1 ,use of the1 #cgc4 ,gemini1 ,constellation1 #ecg4 ,gems1 ,the precious1 #ddc4 ,generation of heat1 #gg4 ,generator1 gramme1 ,the1 #bfh4 ,geography1 ,geology and1 #efd4 0 ,physical1 #fja4 0 ,sources of1 #fjc4 ,geologists1 ,apparatus for1 #ag4 ,geology1 what it teaches1 #efe4 ,germany1 experiment in1 #ac4 ,geysers1 ,the1 #fje4 0 ,theory of the1 #hd4 ,ghost1 ,pepper's1 #ach4 0 stories1 #afa4 ,ghosts1 ,explanations about1 #afa4 0 substantial1 #adb4 ,gilding1 ,processes of1 #djg4 ,glacial period1 ,cause of the1 #eie4 0 ,the1 #eie4 ,glaciers1 ,ice-rivers and1 #fjf4 ,glass1 ,facts about1 #chd4 0 perforated by electricity1 #bae4 ,glauber's salt1 #cic4 ,globe1 ,motion of the1 #ejd4 0 ,spherical form of the1 #ejd4 ,globes1 terrestrial1 ,use of1 #efb4 ,gold1 ,nuggets of1 #djg1 #ddg4 0 resists acid1 #cbe4 0 the king of metals1 #cbe4 ,goniometer1 ,use of the1 #dca4 ,gramme generator1 ,the1 #bfh4 ,grapes1 method of preserving1 #gfh4 ,grapes1 ,room for preserving1 #gfh4 ,graphite1 ,plumbago or1 #cgj4 ,gravitation1 ,force of1 #d1 #dhf4 0 ,laws of1 #b4 ,gravity1 ,centre of1 #be4 0 less in the air1 #bd4 0 same in all bodies1 #bd4 ,green fire1 #cic4 ,grit1 ,millstone1 #eha4 ,grotto del ,cave1 ,the1 #cgd4 ,gulf ,stream1 ,the1 #fah4 ,gum1 #dah4 ,gymnotus1 ,electricity of the1 #bhd4 ,gyroscope1 ,principle of the1 #bgg4 0 ,the1 #gdb4 0 ,the electric1 #gdc4 ,hail1 ,dew and1 #fda4 ,halos1 ,lunar1 #fdh4 ,harmonograph1 ,construction1 #age4 ,havre1 ,mirage at1 #ai4 ,heat1 a series of vibrations1 #gd4 0 ,absorption of1 #ge4 0 ,conduction of1 #hi4 0 ,definition of1 #gb4 0 ,development of1 #gg4 0 ,expansion by1 #ha1 #hb4 0 ,generation of1 #gg4 0 ,how to study1 #ge4 0 ,latent1 #hi4 0 light and1 ,connection of1 #id4 0 ,mechanical equivalents1 #gd4 0 ,material theory of1 #gb4 0 produces changes of state1 #hi4 0 ,radiant1 #ij4 0 ,reflection and refraction1 #ib4 0 ,science of1 #gb4 0 ,sources of1 #gg4 0 ,specific1 #hh4 0 spectrum1 ,the1 #adf4 0 the movement of particles1 #ia4 0 ,theory of1 #gb4 ,history1 ,natural1 #d4 ,holland1 ,sailing on land in1 #dfc4 ,home-made aquarium1 ,a1 #i4 ,hope1 ,mathematical1 #gbg4 0 ,moral1 #gbg4 ,horn1 ,alexander's1 #ahc4 ,hornblend1 #dci4 ,horoscopes1 ,early study of1 #dfg4 ,horses1 ,electric government of1 #bej4 ,houdin's clock1 #geb4 ,household1 ,scientific objects for1 #gdg4 ,hydraulic ,lift1 ,the1 #ga4 0 press1 ,the1 #fa4 ,hydraulics1 #gj4 ,hydrogen1 ,apparatus for1 #cbb4 0 ,bubbles of1 #cea4 0 ,how to generate1 #cej4 ,hydrometers1 ,table of1 #dbj4 ,hydrophilus1 ,the1 #aj4 ,hydrostatics1 ,principles of1 #fa4 ,hydrozoa1 ,the1 #gjh4 ,hymenoptera1 ,the1 #gba4 ,hypnotism1 #ac4 ,ice1 ,how to freeze1 #gf4 0 ,the age of1 #eie4 ,ice-rivers1 ,glaciers and1 #fjf4 ,ice-yachts1 ,canadian1 #dfc4 ,iceland1 ,geysers in1 #fje4 ,igneous rocks1 #ega4 ,illusions1 ,optical1 #aaf4 0 0 ,more about1 #abi4 ,images1 ,accidental1 #aab4 ,implements1 ,neolithic1 #eih4 0 ,palolithic1 #eih4 ,inclination1 ,magnetic1 #bef4 ,indicator1 ,use of the celestial1 #eeh4 ,inertia1 ,definition of1 #e4 0 ,experiments in1 #cg4 0 ,friction and1 #ce1 et sq4 0 ,laws of1 #ce4 ,inflorescence1 #fgi4 0 ,varieties of1 #fhj4 ,infusoria1 ,divisions of the1 #gjg4 0 ,how to capture1 #ae4 0 ,origin of1 #gjg4 0 ,study of1 #g4 ,inks1 how made1 #dad4 ,insects1 #gag4 0 ,anatomy of1 #gag4 0 ,collection of1 #h4 0 ,eyes of1 #gah4 0 ,feet of1 #gah4 0 ,orders of1 #gbj4 0 ,palace for1 #aj4 0 ,preservation of1 #h4 0 ,transformations of1 #gai4 ,insulators1 electric1 ,list of1 #baj4 ,integrator1 ,boys' mechanical1 #bfd4 ,intensity of sound1 #aga4 ,iodine1 #cfh4 ,iron age1 ,the1 #eih4 0 ,bar1 #cig4 0 ,mineral nature of1 #ddc4 0 ,ores of1 #ddd4 0 ,pig or cast1 #cig4 0 ,pyrophoric1 #cbb4 0 unites with oxygen1 #cba4 0 whence obtained1 #cif4 ,irradiation1 ,laws of1 #ajf4 ,islands1 ,coralline1 #fai4 ,isoclinic lines1 #beg4 ,isodynamic lines1 #beg4 ,isogenic lines1 #beg4 ,jar1 ,leyden1 ,home-made1 #aii4 ,jardin1 ,the1 near ,chamouni1 #fjg4 ,jelly-fish1 #gji14 ,jersey1 ,mirage in1 #ai4 ,juggling1 ,balance experiments1 #ca4 ,juno1 ,discovery of1 #ebh4 ,jupiter1 ,appearance of1 #ecj4 0 ,moons of1 #ebi4 0 ,the planet1 #ebh4 ,jurassic formation1 ,the1 #ehf4 ,keuper formation1 ,the1 #ehe4 ,kinetic theory1 ,the1 #gb4 ,kite1 ,a new1 #ddh4 0 ,franklin's1 #bhf4 ,knots and cords1 ,puzzle of1 #gge4 ,laboratory1 ,chemistry without1 #cac4 ,lactoscope1 ,the1 #aeg4 ,ladd1 ,lontin and1 #bge4 ,lakes1 #fbg4 ,lamp1 ,a good petroleum1 #gfa4 0 ,a new alarum1 #gfj4 0 ,dobereiner's1 #djh4 0 ,gay-,lussac's1 #cbg4 0 ,the ,edison1 #bfi4 0 ,the safety1 #cdg4 0 ,the ,swan1 #bga4 ,land1 ,sailing on1 #dfc4 0 ,water and1 #fjc4 ,lantern1 ,magic1 #aeh4 ,lapis-lazuli1 #ddb4 ,latent heat1 #hi4 ,latex1 what it is1 #ffc4 ,latitude1 ,longitude and1 #eje4 ,laughing gas1 #cfa4 ,laurentian system1 ,the1 #egc4 ,lead1 #dja1 #ddf4 0 ,crystallization of1 #cbc4 ,leaning1 ,laws concerning1 #cc4 0 towers1 ,laws of1 #cc4 ,leaves1 ,anatomy of1 #fga4 0 ,arrangement of1 #fgc4 0 ,the1 #fgj4 0 ,varieties of1 #fga4 0 ,various1 #aej4 ,leech1 ,the1 #gad4 ,lenses1 ,description of various1 #aej4 ,leo1 ,constellation1 #ech4 ,lepidoptera1 ,the1 #gba4 ,leyden jar1 ,to make a1 #aii4 ,lias1 ,the1 #ehf4 ,libra1 ,constellation1 #eci4 ,lichens1 #fhi4 ,lift1 ,hydraulic1 #ga4 ,light1 a vibratory motion1 #ic4 0 ,absorption of1 #ie4 0 and its sources1 #ic4 0 ,cost of1 #aja4 0 ,decomposition of1 #adc4 0 ,definition of1 #ic4 ,lightning1 ,different kinds of1 #bhi4 ,light distributed in rays1 #id4 0 electric1 ,how to produce1 #bfe4 0 0 ,first discovery of1 #bba4 0 heat and1 ,connection of1 #id4 0 in the eye1 #adb4 0 of an electric spark1 #aai4 0 oxy-hydrogen1 ,the1 #afj4 0 ,polarization of1 #aee4 0 producer of life1 #ffj4 0 ,reflection of1 #ie4 0 ,refraction of1 #if4 0 ,velocity of1 #id4 0 what made up of1 #adc4 0 ,zodiacal1 #ejj4 ,lightning1 ,forked and sheet1 #bhi4 0 ,colour of1 #bhh4 ,lights1 ,bengal1 how made1 #djd4 0 ,comparison of1 #ii4 ,lime1 ,salts of1 #cic1 #dcg4 ,lines1 ,isoclinic1 #beg4 0 ,isodynamic1 #beg4 0 ,isogonic1 #beg4 0 ,isothermal1 #fec4 0 oblique1 ,influence of1 #aba4 ,linnan system1 ,the1 #fie4 ,liquids1 ,definition of1 #d4 0 ,displacement of1 #fi4 0 ,gases and1 #dd4 ,lithium1 #cic4 ,longitude1 ,latitude and1 #eje4 ,lontin1 ,ladd and1 #bge4 ,ludion1 ,the1 #eg4 ,luminous paint1 #afj4 0 surfaces1 ,laws of1 #ajg4 ,machine1 electric1 ,to make an1 #bjg4 0 ,tree-felling1 #gfg4 0 ,writing1 #bdf4 ,machines1 ,electro-magnetic1 #bgb4 ,maestricht formation1 ,the1 #eij4 ,magic squares1 #gcb4 0 top1 ,the1 #gdj4 ,magnesian limestone1 ,the1 #ehc4 ,magnesium1 #cie1 #dci4 ,magnet1 ,a natural1 #bca4 0 ,definition of a1 #bca4 ,magnetic dip1 ,the1 #bef4 0 inclination1 #bef4 ,magnetism1 ,electro1 #bee4 0 ,terrestrial1 #fde4 ,magnetization1 #bcb4 ,magnets in ancient times1 #bed4 ,magnitude1 ,centre of1 #cd4 ,man1 cave1 ,the1 #eih4 0 during the ,glacial ,period1 #eig4 0 prehistoric1 #eig4 0 river-drift1 ,the1 #eih4 ,manganese1 #djj1 #dde4 ,mars1 ,moons round1 #ebf4 0 ,the planet1 #ebc4 ,mathematical games1 #gbf4 ,matter1 ,definition of1 #d4 ,medullary rays1 ,the1 #ffi4 ,medus1 ,the1 #gji4 0 ,phosphorescence of1 #gdj4 ,megaphone1 ,mr4 ,edison's1 #ahc4 ,membrane tympani1 ,the1 #aff4 ,menagerie for insects1 #aj4 ,menisques in a barometer1 #fe4 ,mercury1 ,all about1 #eba4 0 ,fulminating1 #dbj4 0 ,uses of1 #dje1 #ddf4 ,mesozoic period1 ,the1 #ehd4 ,metals1 ,characteristics of1 #chh4 0 ,classification of1 #chi1 #dji4 0 ,common and precious1 #cbj4 0 in the spectroscope1 #adf4 0 ,noble1 #dje4 0 ,specific gravity of1 #chi4 0 what they are1 #chh4 ,meteorites1 aerolites1 or1 #dic4 ,meteorology1 #fbh4 0 ,phenomena of1 #bj4 ,meteors1 what are they8 #dij4 ,mica1 #ddc4 ,microscope1 ,invention of the1 #adi4 0 periscopic1 ,the1 #aej4 0 ,the spectrum1 #adg4 ,microscopes1 ,reflecting1 #aej4 ,milk1 ,constituents of1 #dbb4 0 ,sugar of1 #dbc4 ,milky way1 ,the1 #eec4 ,millstone grit1 #eha4 ,mineralogists1 ,apparatus for1 #ag4 ,mineralogy1 ,crystallography1 #dbd4 ,mineral waters1 #cgb4 ,minerals1 ,amorphous1 #dca4 0 ,classification of1 #dbd1 #dbe4 0 ,definition of the term1 #dbd4 0 ,synoptical table of the1 #dce4 ,miocene formation1 ,the1 #eic4 ,mirage at ,havre1 #ai4 0 ,cause of1 #fdi4 0 in ,jersey1 #ai4 0 on beaches1 #ah4 ,mirrors1 ,remarks on1 #ie4 ,mistral1 ,the1 #fca4 ,mixtures1 ,freezing1 #hi4 ,molecule1 ,definition of a1 #cji4 ,molluscs1 #gbd4 ,money-boxes1 ,scientific1 #gde4 ,montgolfier1 ,discovery of1 #b4 0 ,early balloons of1 #bie4 ,monsoon1 ,the1 #fcj4 ,moon1 ,description of the1 #eaj4 0 ,eclipses of the1 #eai4 0 ,influences of on weather1 #feb4 0 its influence on the tides1 #eag4 0 ,motion of the1 #eac4 0 ,phases of the1 #eae4 0 ,rate of progression of the1 #eac4 0 ,superstitions concerning1 #eaj1 #eac4 0 ,surface of the1 #eaa4 0 ,planetary1 #dhi4 ,morphine1 #daf4 ,morse system1 ,the1 #bda4 ,morse's telegraph1 #bcc4 ,mosses1 ,alg and1 #fhh4 ,motion1 ,causes of1 #dj4 0 ,definition of1 #dj4 0 ,perpetual1 #da4 ,mould1 ,vegetable1 #fij4 ,mountain strata1 ,contortion of1 #fbe4 0 ,what is a1 #fbd4 ,mountains1 ,causes of1 #fbd4 0 ,slopes of1 #fbe4 ,movements1 ,synthesis of1 #abd4 ,multiplier1 ,first use of the1 #bcb4 ,mural circle1 ,the1 #dgh4 ,musical pitch1 #aic4 ,muslin1 ,incombustible1 #cac4 ,myriapoda1 ,the1 #gaf4 ,natural ,history1 #d4 0 ,philosophy1 #d4 0 system1 ,the1 #fii4 ,nature1 ,balance of1 #fag4 0 ,forces of1 #bb4 0 ,need for knowing about1 #c4 0 ,nothing mute in1 #ba4 0 ,smooth polish of1 #ad4 0 ,phenomena of1 #c4 0 what it is1 #b4 ,near-sightedness1 #adj4 ,nebul1 #eea4 ,needle1 ,game of the1 #gbi4 0 ,the magnetic1 #bca4 0 machine1 ,the1 #bch4 ,negative and positive electricity1 #bjb4 ,neptune1 ,the planet1 #ecd4 ,nichol's prism1 #aef4 ,nicholson's classes of plants1 #gjb4 ,nickel1 cobalt and1 #dja1 #dde4 ,nicotine1 #daf4 ,nina1 ,the1 #ggc4 ,nitrogen1 #cei4 0 ,compounds of1 #cei4 0 ,monoxide1 #cfa4 ,nitrogenous substances1 #dbb4 ,nodal points1 ,the1 #aid4 ,nodes of sound waves1 #afi4 ,noise distinguished from sound1 #afg4 ,nomenclature1 ,astronomical1 #dga4 ,normandy1 ,a trip in1 #f4 ,object1 ,a natural1 #c4 ,oils1 ,fats and1 #dba4 0,old ,red0 a fresh-water deposit1 #egg4 ,oolite formation1 ,the1 #ehf4 ,opium1 #daf4 ,optical cabinets1 #ih4 ,optics1 ,the science of1 #ic4 ,organic chemistry1 #daj4 ,orion constellation1 #edd4 ,orthoptera1 ,the1 #gba4 ,oxidation1 #cdi4 ,oxygen1 ,discovery of1 #cdh4 0 consumed by breathing1 #cdb4 0 ,how to obtain1 #cdh4 ,oysters1 ,light from shells of1 #afj4 ,ozone1 ,use of1 #cdd4 ,paint1 ,luminous1 #afj4 ,palace1 ,insects1 #aj4 ,palozoic systems1 #egc4 ,pallas1 ,discovery of1 #ebh4 ,paper wheel toy1 #gfd4 ,parachutes1 ,descents by1 #cjd4 ,parallax1 ,explanation of1 #dhd4 0 ,illustrations of1 #dhc4 0 ,use of1 #dhe4 ,para-magnetic and dia-magnetic1 #beh4 ,paraselen1 ,cause of1 #fdh4 ,paris1 ,great snowfall in1 #bj4 ,pedometer1 ,the1 #gef4 ,peiffer's electrophorus1 #bgi4 ,pen1 electric1 ,the1 #bdh4 ,pencil1 ,edison's ,pneumatic1 #ded4 ,pendulum1 ,description of the1 #db4 0 ,the1 #dha4 0 ,variations in the1 #db4 ,period1 ,the ,glacial1 #eie4 ,permian formation1 ,the1 #ehb4 0 0 ,fauna of1 #ehb4 ,phantom band1 ,a1 #aif4 ,pharaoh's serpents1 #cae4 ,phases of the ,moon1 #eae4 ,phenakistoscope1 ,the1 #aaj1 #aba4 ,phenomena1 ,atmospheric1 #fdb4 0 ,chemical1 #bb4 0 ,meteorological1 #bj4 0 ,nature1 #c4 0 of contrast1 #aab1 #aac4 0 ,physical1 #bb4 ,phial of the four elements1 #dg4 ,philosophy1 ,natural1 #d4 ,phonograph1 ,edison's1 #aij4 ,phosphorescence1 #cca4 ,phosphorus1 ,bologna1 #ccc4 0 how obtained1 #cha4 ,photography1 ,camera for1 #aea4 0 ,instantaneous1 #aec4 ,photometers1 #aja4 ,photometry1 #aja4 ,photophone1 ,the1 #aee4 ,photosphere1 ,the1 #dii4 ,phraseology1 ,chemical1 #cch4 ,physics1 ,meaning of1 #bb4 0 ,mechanical1 #ca4 ,pile1 ,a microscopic1 #bjj4 0 hermetic1 ,the1 #bhc4 0 ,volta's first1 #bai4 0 ,zamboni1 #bba4 ,pins1 scarf1 ,electrical1 #bha4 ,pisces1 ,constellation1 #edj4 ,pistil1 ,the1 #fgh4 ,pistils1 ,use of1 #ffe4 ,pitch1 ,musical1 #aic4 ,plains1 #fbf4 ,planet1 ,the giant1 #ebh4 ,planets1 ,comparative sizes of1 #dhg4 0 ,list of the1 #dhg4 0 ,minor1 #dhi1 #ebg4 0 ,moons of the1 #dhi4 ,plant1 ,definition of a1 #ffa4 ,plants1 ,classification of1 #fid4 0 ,flowering1 #ffd4 0 ,growth of1 #ffe4 0 ,moncious1 #fha4 0 ,non-flowering1 #fhf4 0 ,similarity of1 to animals1 #feh4 0 ,structure of1 #ffa4 ,plateaus1 ,tablelands or1 #fbf4 ,plating1 ,electro1 #bbg4 ,platinum1 ,all about1 #cbg4 0 ,uses of1 #djh1 #ddg4 ,plumbago1 ,graphite or1 #cgj4 ,plutonic rocks1 ,the1 #fja4 ,pneumatic despatch1 ,the1 #eg4 ,polaris1 ,the star1 #edb4 ,polarization of light1 #aee4 ,polarizer1 ,use of a1 #aef4 ,poles1 ,electrodes or1 #bba4 ,pompeii1 ,paintings at1 #aba4 ,porcelain1 ,manufacture of1 #dda4 ,porosity1 ,definition of1 #e4 ,positive and negative electricity1 #bjb4 ,portuguese man-of-war1 ,the1 #gji4 ,potassium1 #cij1 #dcg4 0 ,compounds of1 #cia4 ,praxinoscope1 ,the1 #aaj1 #abc4 0 theatre1 ,the1 #abf4 ,prehistoric man1 #eig4 ,preservation of insects1 #h4 ,press1 ,hydraulic1 #fa4 ,pressure1 ,fluid application of1 #fc4 0 on the ocean bed1 #faf4 ,prism1 ,nichols'1 #aef4 ,probabilities1 ,science of1 #gbf4 ,protoplasm1 ,definition of1 #fei4 ,protozoa1 ,definition of1 #gjd4 ,protractor1 ,use of the1 #dge4 ,pump1 ,the common1 #eg4 ,punctum ccum1 ,the1 #acd4 ,puzzle1 ,the 0,boss10 #gca4 ,pyrites1 ,crystallized1 #ah4 0 ,iron1 #ddd4 ,pyrometer1 ,the1 #ia4 ,quadrant1 ,use of the simple1 #dgf4 ,quarry1 ,derivation of the term1 #dbg4 ,quartz1 ,varieties of1 #dcf4 ,quicksilver4 ,see ,mercury4 ,quinine1 #daf4 ,radiant heat1 #ij4 ,rain1 ,causes of1 #fcg4 0 ,distribution of1 #fcg4 0 ,measurement of1 #fch4 0 water1 ,the1 #ga4 ,river-beds1 ,slope of1 #fbf4 ,rainbow1 ,the1 #fdg4 ,rays1 ,medullar1 #ffi4 ,reaction1 ,action and1 #ce4 ,recreation1 ,science and1 #a4 ,red fire1 #cie4 ,reflection of heat1 #ib4 0 light1 #ie4 0 sound1 #aga4 ,refraction of heat1 #ib4 ,reaction of1 light1 #if4 0 sound1 #aga4 ,refractions1 ,table of1 #dgi4 ,reptiles1 ,the age of1 #ehe4 ,repulsion in air-particles1 #dh4 ,ruins1 #dba4 ,rest1 ,no absolute1 #dj4 ,rhizome1 ,definition of1 #ffg4 ,rhone1 ,colours of the1 #egj4 ,robert's clock1 #gec4 ,robin's spectres1 #ach4 ,rocks1 ,acidic1 #fjb4 0 ,basic1 #fjb4 0 ,igneous1 #ega1 #fja4 0 ,plutonic1 #fja4 0 ,sedimentary1 #egj4 0 ,volcanic1 #fja4 ,roots1 ,various1 #fff4 ,rubidium1 #cic4 ,sagittarius1 ,constellation1 #eci4 ,sailing on railroads1 #dfe4 ,salt1 ,glauber's1 #cic4 0 ,epsom1 #cie4 0 what meant by in chemistry1 #caa4 ,sandstone1 ,old ,red1 #egf4 0 ,upper ,red1 #ehe4 ,sassoline1 ,boron or1 #dce4 ,satellites1 ,planetary1 #dhi4 ,saturn1 ,rings of1 #ecb4 0 ,satellites of1 #ecb4 0 ,the planet1 #ecb4 0 ,tree of1 #cbc4 ,sawing1 ,machine for1 #gfg4 ,scale1 diagonal1 ,use of the1 #dgg4 ,scarf-pins1 ,electrical1 #bha4 ,scavengers1 ,nature's1 #gac4 ,scenograph1 ,description1 #aec4 ,scheele1 ,apparatus used by1 #bh4 ,science and ,recreation1 #a4 0 ,definitions of1 #a-e4 0 ,domestic economy and1 #geg4 0 in the open air1 #f4 ,scorpio1 ,constellation1 #eci4 ,sea1 ,at the bottom of the1 #fae4 0 ,saltness of the1 #faj4 0 ,the1 #faj4 0 anemones1 #gaj4 0 bed1 ,irregularity of the1 #fag4 0 cucumbers1 #gad4 0 urchins1 #gab4 0 water1 ,buoyancy of1 #fg4 0 0 ,composition of1 #faj4 ,sealing-wax1 ,experiments with1 #aig4 ,seasons1 ,recurrence of the1 #ejg4 ,sedimentary rocks1 #egj4 ,selenium1 #chf4 0 ,mineral nature of1 #dce4 ,selenography1 #eaj et sq4 ,semaphore1 ,the1 #bcb4 ,serpents1 ,pharaoh's1 #cae4 ,sewing-machines1 ,motive power1 #geh4 ,shadows1 comic1 #aeh4 ,shot1 how made1 #djc4 ,signalling1 #ahc4 ,silicon1 ,silica and1 #chc1 #dcf4 ,silurian system1 #ege4 ,silver dissolved by nitric acid1 #cbf4 0 how obtained1 #djf1 #ddg4 0 ,uses of1 #djf4 ,simoon1 ,the1 #fca4 ,sky1 ,how to read the1 #eee4 0 why blue1 #fdg4 ,sleet1 ,cause of1 #fdj4 ,sleight of hand1 ,chemistry and1 #cce4 ,smelting1 ,melting and1 #cif4 ,snow1 ,causes of1 #fci4 0 ,great falls of1 #bj4 0 what it is1 #fci4 ,soap1 how made1 #cia4 ,soap-bubbles1 ,notes on1 #ih4 ,sodium1 #cib1 #dcg4 0 ,experiments with1 #cag4 ,solar chronometers1 #efc4 0 spectrum1 ,the1 #adc4 ,solid1 ,definition of1 #d4 ,solitaire1 explanation of puzzles1 #gcf4 0 ,the game of1 #gce4 ,solstices1 ,equinoxes and1 #dif4 ,sound impossible without air1 #afc4 0 ,intensity of1 #aga4 0 ,reflection of1 #aga4 0 ,refraction of1 #aga4 0 transmitted by solids1 #agd4 0 ,velocity of1 #afi4 0 ,velocity of1 varies1 #agj4 0 what it is1 #afg4 0 whence it arises1 #afg4 ,sound-waves1 ,nodes of1 #afi4 0 to see1 #agc4 ,sounds1 musical and unmusical1 #afg4 ,sources of heat1 #gg4 ,space1 what it is1 #d4 ,spar1 ,derbyshire1 #cie4 ,spark1 ,electric duration of1 #bac4 0 ,light of an electric1 #aai4 ,speaking tubes1 #agb4 ,specific gravity1 #fh4 0 ,huxley's definition of1 #gj4 0 of metals1 #chi4 ,specific heat1 #hh4 ,spectacles1 ,different glasses for1 #aej4 ,spectra1 ,composition of1 #adg4 0 ocular1 #adc4 ,spectral illusions1 #afa4 ,spectre1 a visible1 #afa4 0 of the ,brocken1 ,the1 #fej4 ,spectres1 ,impalpable1 #abf4 0 ,m4 ,robin's1 #ach4 ,spectroscope1 ,discovery of the1 #ade4 0 ,uses of the1 #ade4 ,spectroscopy1 ,science of1 #ade4 ,spectrum analysis1 #ade4 0 heat1 #adf4 0 solar1 #adc4 ,sphericity1 ,aberration of1 #aje4 ,spider tribe1 ,the1 #gbc4 ,sponges1 ,nature of1 #gjf4 0 ,reproduction of1 #gjf4 ,spots1 ,sun1 #dih4 ,springs1 ,causes of1 #fjd4 ,squares1 ,magic1 #gca4 ,stamens1 ,the1 #fgg4 0 ,uses of1 #ffe4 ,starch1 ,notes about1 #dag4 ,star1 pole1 ,the1 #did4 ,star-fish1 #gac4 ,stars1 ,clusters of1 #eea4 0 ,colours of the1 #edh4 0 ,distance of the1 #edd4 0 ,double and multiple1 #edf4 0 ,falling1 #dij4 0 ,fixed1 #ece4 0 ,lost1 #eej4 0 ,magnitude of the1 #eed4 0 ,motions of1 #ece4 0 ,new1 #eej4 0 ,number of the1 #ecf4 0 ,radiating form of1 #aje4 0 ,showers of1 #dia4 ,state1 ,changes of1 produced by heat1 #hi4 ,static electricity1 #bji4 ,steam1 ,definition of1 #ia4 0 ,tree-felling by1 #gff4 ,steamer1 ,the smallest1 #ggc4 ,stem1 ,parts of the1 #ffg4 0 ,the1 #ffg4 0 ,varieties of the1 #ffg4 ,stems1 ,tree1 #ffh4 ,stereoscope1 ,principle of the1 #ada4 0 ,reflecting1 #ada4 0 ,refracting1 ,the1 #ada4 ,stone1 ,pudding1 #efh4 ,stories1 ,ghost1 #afa4 ,strata1 ,list of geological1 #egc4 ,strepsiptera1 ,the1 #gba4 ,strings1 ,vibration of1 #agj4 ,strontium1 #cie1 #dch4 ,strontium1 ,luminous sulphates1 #ccc4 ,structure of plants1 #ffa4 ,strychnine1 #daf4 ,sublimation and distillation1 #hf4 ,substances1 ,indifferent1 #dag4 ,substances1 ,nitrogenous1 #dbb4 ,sucker1 ,the school-boy's1 #dh4 ,sugar1 ,refining of1 #dah4 ,sulphur1 ,mineral1 #dce4 0 ,uses of1 #cgi4 ,sun1 ,density of the1 #ejc4 0 ,distance of the1 #ejc4 0 ,eclipses of the1 #eai4 0 ,form of the1 #dih4 0 ,motion of the1 #dif4 0 ,power of the1 #ejc4 0 ,spots on the1 #dih4 0 ,volume of the1 #ejc4 ,suns1 mock1 ,cause of1 #fdh4 ,sunset1 ,colours of the1 #fee4 ,surfaces1 luminous1 ,laws of1 #ajg4 ,swan lamps1 ,the1 #bga4 ,swimming1 ,new apparatus for1 #deh4 ,swing1 ,simple child's1 #gfc4 ,symbols1 ,chemical table of1 #cjh4 ,synthesis of movements1 #abe4 ,syphon recorder1 ,thomson's1 #bdd4 ,syren1 ,the1 #aid4 ,syringes1 ,an effect of atmospheric pressure1 #fc4 ,system1 ,cambrian1 #ege4 0 ,coal1 #egh4 0 ,devonian1 #egf4 0 ,laurentian1 #egc4 0 ,silurian1 #ege4 0 ,the ,solar1 #dhg4 ,systems1 ,palozoic1 #egc4 ,tablelands1 ,plateaus or1 #fbf4 ,tadpoles in aquaria1 #aj4 ,talking head1 ,how to work1 #ace4 ,tangent galvanometer1 ,the1 #bbg4 ,tanning1 #dad4 ,tanning1 ,process of1 #dad4 ,tap1 ,a new kind of1 #gfb4 ,tape-worms1 #gaf4 ,tar1 ,uses of1 #cgh4 ,taurus1 ,constellation1 #ecg4 ,telegraph1 ,automatic1 #bdc4 0 electric1 ,discovery of1 #bcb4 0 0 ,ordinary form of1 #bcd4 ,telegraphic system1 ,new1 #bdd4 ,telegraphs1 ,early1 #bcb4 ,telegraphy1 ,practical1 #bci4 0 ,submarine1 #bdc4 ,telephone1 ,description of the1 #ahf4 0 ,invention of the1 #ahf4 ,telescope1 ,achromatic1 #adi4 0 ,description of the1 #adg4 0 ,divided1 explained1 #ace4 0 ,introduction of the1 #dfi4 0 reflector1 ,the1 #adi4 ,telescopes1 #adi4 ,tellurium1 #chf4 ,terminations1 ,chemical1 #ccg4 ,tertiary period1 ,the1 #eia4 ,thaumatrope1 ,the1 #aaj1 #aba4 ,theatre1 ,the praxinoscope1 #abf4 ,theory1 atomic1 ,the1 #cji4 ,thermo-dynamics1 ,definition of1 #gc4 ,thermometer1 ,how to make a1 #gi4 0 ,invention of the1 #gh4 ,thermometers1 ,alcoholic1 #hj4 ,thunder1 ,causes of1 #bia4 ,thunderstorms1 ,precautions1 #bhc4 ,tides1 ,ebb and flow of1 #fab4 0 ,influence of the moon1 #eag4 0 ,science of the1 #fad4 ,time1 ,ancient measurements of1 #dgi4 0 ,equation of1 #dhb4 0 ,sidereal1 #dgh4 ,tin1 ,crystallization of1 #cbd4 0 ,uses of1 #djc1 #ddf4 ,tissues1 ,cellular and vascular1 #ffa4 ,top1 ,the dazzling1 #abh4 0 ,the magic1 #gdj4 ,topophone1 ,description of the1 #ahj4 0 ,invention of the1 #ahj4 ,tops1 ,chromatic1 #aji4 0 in optical physiology1 #ajh4 ,torpedo1 ,electricity of the1 #bhe4 ,torsion electrometer1 ,the1 #bji4 ,towers1 leaning1 ,laws of1 #cc4 ,toys1 ,electric1 #bgi4 0 ,simple1 #gfd4 ,tramways1 ,electric1 #bgb4 ,transit1 ,curious modes of1 #ggj4 0 instrument1 ,how to use1 #dgg4 ,trapeze1 ,simple home-made1 #gfb4 ,tree-felling1 ,steam power for1 #gff4 0 frogs1 #aa4 ,trias1 ,the1 #ehe4 0 ,upper and lower1 #ehe4 ,trolly-sailing1 #dfe4 ,trumpets1 ,speaking1 #agb4 ,tube1 ,galileo's1 #adh4 ,tube well1 ,the1 #dee4 ,tuber1 ,definition of the1 #ffg4 ,tubes1 ,speaking1 #agb4 ,tuning-fork1 ,the1 #aic4 ,type casting1 #dje4 0 metal1 #djd4 ,union1 ,chemical1 involves heat1 #caa4 ,uranus1 ,the planet1 #ecc4 ,vacuum1 ,torricellian1 #ea4 ,vanessa algina1 #af4 ,vapour1 ,clouds and1 #fcd4 0 what it is1 #fbi4 ,variations of the compass1 #beg4 ,varnishes1 #dba4 ,vascular tissues1 #ffa4 ,vehicle1 ,a new two-wheeled1 #ggj4 ,velocipede1 ,new water1 #dfa4 ,velocipedes1 ,ancient1 #gge4 ,velocity1 ,acceleration of1 #da4 0 ,definition of1 #bc4 0 ,facts about1 #bc4 0 of ,electricity1 #bab4 0 of light1 #id4 0 ,retarded1 #da4 ,ventilation1 ,notes on1 #cdd4 ,venus1 ,the planet1 #ebb4 ,vessels1 connected1 ,laws of1 #fb4 ,vesta1 ,discovery of1 #ebh4 ,views1 ,dissolving1 #afj4 ,vinegar1 how prepared1 #dah4 ,virgo1 ,constellation1 #ech4 ,vision1 ,binocular1 #ada4 0 ,definition of1 #ajc4 0 ,field of1 #adj4 0 ,the eye and1 #adj4 ,vivaria1 #af4 ,volcanic rocks1 ,the1 #fja4 ,volcanoes1 ,earthquakes and1 #fbj4 0 ,formation of new1 #fbc4 0 ,number of1 #fba4 ,voltaic arc1 ,the1 #bbc4 ,volume1 ,weight and1 #ei4 ,waste1 none in nature1 #cda4 ,watches1 ,clocks and1 #dhj4 ,water a compound body1 #cec4 0 a form of matter1 #ei4 0 ,action of1 in ,geography1 #fjh4 0 ,all about1 #ei4 0 as ice1 #cee4 0 as steam1 #cee4 0 ,buoyancy of1 #fg4 0 ,chemistry of1 #ceb4 0 decomposed by electricity1 #bbf4 0 ,distillation of1 #cef4 0 ,effects of heat on1 #hb4 0 ,evaporation of1 #g4 0 freezing by evaporation1 #he4 0 ,fresh1 in the sea1 #faa4 0 hot1 grows lighter1 #ha4 0 ,land and1 #fjc4 0 ,mineral1 #cgb4 0 ,petrification of1 #ceg4 0 ,pressure of1 #fj4 0 ,sea1 composition of1 #faj4 0 ,spring1 #cec4 0 sustained by air1 #ei4 0 ,the force of1 #fj4 0 the unit of specific gravity1 #gj4 ,water-press1 ,the1 #fa4 ,water-ram1 ,the1 #ga4 ,waterspout1 ,cause of the1 #fdc4 ,waterspouts1 ,how to destroy1 #fdc4 ,water-wheels1 #ga4 ,waves1 ,height of the1 #fac4 0 ,hurricane1 #fac4 0 ,movement of the1 #fab4 0 ,standing and progressive1 #afi4 0 ,tidal1 #fac4 ,way1 ,milky1 #eec4 ,wealden formations1 ,the1 #ehh4 0 0 ,fauna of1 #ehi4 0 0 ,flora of1 #ehi4 ,weather1 ,danger of forecasting1 #fee4 0 forecasts1 #fea4 0 indications1 #fef4 0 ,rules for prophesying1 #fef4 ,weather-glass1 ,the1 #ec4 ,weight1 ,combining or atomic1 #cji4 0 ,definition of1 #bb4 ,well tube1 ,the1 #dee4 ,wells1 ,artesian1 #fjd4 0 ,gas1 #fjf4 0 ,instantaneous1 #deg4 0 ,oil1 #fjf4 ,wheatstone's telegraph1 #bdb4 ,whispering galleries1 #agb4 ,wind1 ,pressure of the1 #fcb4 0 ,use of the1 #fcc4 ,wind1 ,velocity of the1 #fcj4 ,windows1 ,double1 #geg4 ,winds1 ,air currents and1 #fbi4 0 ,cause of1 #fbi4 0 ,list of local1 #fca4 0 ,trade1 #fcj4 ,wine1 ,spirits of1 #dah4 ,wire-drawing1 #cih4 ,wollaston's bulb1 #ia4 ,world1 ,study of the1 #a4 ,worms1 ,the1 #gad4 ,writing machine1 ,the1 #bdf4 ,wings1 ,best form for1 #dej4 ,yachts1 ,canadian ice1 #dfc4 0 ,double sailing1 #dfb4 ,yellow spot1 ,the1 #adj4 ,zamboni pile1 #bba4 ,zeolites1 #ddj4 ,zinc1 ,use of1 #djc1 #ddf4 ,zodiac1 ,signs of the1 #dga4 ,zodiacal light1 ,the1 #ejj4 ,zoology1 ,definition of1 #gjj4 ,zootrope1 ,the1 #aba4 99 99 99 99 99 ,transcriber's ,notes ,obvious typographical errors have been silently corrected but variations in hyphenation and all other spelling and punctuation remains unchanged4 ,italics are represented thus italic and bold thus bold4 ,the following corrections have been made3 ,ramur has been corrected to ,raumur throughout4 ,page #id 8,there are seven primary colours in the sunlight1 which is white4 ,these can be divided or 8dispersed10 and the shortest rays of the spectrum are found to be red1 the longest violet40 has been corrected to longest red and shortest violet4 ,page #aji4 8,if1 for instance1 we place on a disc covered with blue and red sectors of equal size1 a black disc1 of which the sectors are alternately filled in or empty1 the disc1 as it turns round1 will appear blue if the black sectors of the upper disc exactly cover the red sectors of the lower disc2 and it appears red1 if1 on the contrary1 the blue sectors are covered with the black20 red has been added4 ,page #bch4 ,the footnote ,monvel's 8,course of ,physics40 appears1 but there is no reference to it in the text4 ,page #ecc4 ,the time of revolution of ,saturn's ,moons was given in d4 h4 sec41 this has been corrected to d4 h4 min4