,illustration3 ,,the ,,two ,,oceans4 7#a7 ,arial ,ocean4 7#b7 ,greatest height attained by ,messrs4 ,glaisher and ,coxwell1 being #cf1ifj feet1 or seven miles above the sea level4 7#c7 ,arial ,alps1 or stratum of clouds #ae1jjj feet in depth4 7#d7 ,highest bird-region4 ,,weather ,,warnings ,,for ,,watchers ,,by ,,the 8,,clerk0 ,,himself4 ,,with ,,concise ,,tables ,,for ,,calculating ,,heights 8,the actuating force of every wind that blows2 of every mighty current that streams through ocean depths2 the motive cause of every particle of vapour in the air1 of every mist and cloud and raindrop1 is ,,solar ,,radiation40--,george ,warington4 ,,london ,,houlston ,,and ,,sons ,,paternoster ,,square1 ,e4,c4 #ahgg ,the right of translation is reserved4 ,entered at ,stationers' ,hall4 ,,list ,,of ,,works ,,of ,,reference4 ,,boutan ,,et ,d',,almeida4 ,cours ,elmntaire de ,physique4 ,,buchan1 ,a4 ,introductory ,text-book of ,meteorology4 ,w4 ,blackwood and ,sons1 #ahga4 ,,cazin1 ,,achille4 ,la ,chaleur4 ,hachette and ,co41 #ahfh4 ,,crampton1 ,,rev4 ,,jos41 ,m4,a4 ,the ,three ,heavens4 ,w4 ,hunt and ,co41 #ahgf4 ,,chambers' ,encyclopdia4 ,w4 and ,b4 ,chambers1 #ahge4 ,,drew1 ,,john4 ,practical ,meteorology4 ,van ,voorst1 #ahgj4 ,,fitzroy1 ,,the ,,late ,,admiral4 ,weather ,book and ,barometer ,manual4 ,,flammarion1 ,,camille4 ,l',atmosphere4 ,,guillemin ,,amed,e4 ,les ,forces de la ,nature4 ,,glaisher1 ,j41 ,f4,r4,s4 ,hygrometrical ,tables4 ,taylor and ,francis1 #ahfi4 ,,hartley1 ,w4 ,n4 ,air and its ,relations to ,life4 ,longmans1 #ahge4 ,,herschel1 ,,sir ,,john ,f4 ,w4 ,meteorology1 from ,ency4 ,brit4 ,a4 and ,c4 ,black1 #ahfj4 ,,kaemtz1 ,l4 ,f4 ,complete ,course of ,meteorology4 ,baillire ,london4 ,,martin',s ,natural ,philosophy4 ,simpkin1 ,marshall and ,co41 #ahfh4 ,,tyndall1 ,,john1 ,d4,c4,l41 c4 ,heat1 a ,mode of ,motion4 ,fifth ,edition4 ,longmans1 #ahge4 ,,rodwell4 ,dictionary of ,science4 ,e4 ,moxon and ,co41 #ahga4 ,,proctor4 ,science ,byways4 ,smith1 ,elder and ,co41 #ahge4 ,,scott1 ,r4 ,h41 ,m4,a41 ,f4,r4,s4 ,instructions in the ,use of ,meteorological ,instruments1 #ahge4 ,,warington1 ,,george4 ,phenomena of ,radiation4 ,,contents4 ,,page ,actinometer #aj thrioscope #af ,altitude tables #cg ,anemograph #hd ,anemometers1 velocity #hj ,aneroid barometer #ce ,atmidometer #be ,atmospheric electricity #hi ,barograph #ch ,barometer precautions #dj description of #bi construction of #bf self-recording #cf warnings #dc syphon #cj wheel #cc corrections of #bg ,beaufort's scale of wind force #gf weather notation #hb ,black bulb in vacuo #ab ,boiling-point thermometer #cf ,calorification #h ,condensation #de ,capacity1 correction #bg ,capillarity1 correction #bh ,centigrade thermometer #bj ,cirro-cumulus cloud #ef ,cirro-stratus cloud #ef ,cirrus cloud #eb ,clouds1 forms of #eb amount of #eg ,compass bearings #ga ,conversion of thermometer scales #bc ,cumulo-stratus cloud #ef ,cumulus cloud #ec ,dew-point #dh ,electrification #hf ,electrometers1 forms of #ij ,electroscope #hi ,evaporation1 measurement of #bd ,fahrenheit's thermometer #bj ,fortin's barometer #bg ,freezing-point #bj ,frost1 management of hygrometer in #ej ,gold-leaf electroscope #hi ,glass1 storm #da ,heights1 measurement of #cg ,hours of observation #ci ,howard's cloud nomenclature #eb ,hygrometer1 ,daniell's #dg ,hygrometer1 ,mason's #dh ,hygrometer precautions #ej ,kew verification #db ,lightning #ij conductors #ia ,mean sea-level #bh ,maximum thermometers #af ,meteorology1 list of works on #d ,minimum thermometers #ag ,mountain barometers #ce ,motion #fg ,nimbus clouds1 form of #eg ,ozone1 determination of #ia ,ozonometer #ib ,packing barometers #cb ,position of barometers #cc ,pyrheliometer #i ,pressure anemometer #gi ,psychrometer #di ,radiation1 solar #i ,radio-solar thermometer #ac ,rain1 measurement of #fj ,rain gauges #fb to #fg ,rarefaction #bf ,raumur's scale #bj ,regnault's hygrometer #dg ,robinson's anemometer #ha ,solar radiation #i ,six's thermometer #ah ,standard barometer #bh ,stevenson's thermo-screen #ea ,stratus cloud #ee ,suspension of barometers #dj ,sympiesometer #da ,temperature1 correction for #bg ,terrestrial radiation #ac ,thermographs #bc ,thermometer scales #bj screens #ej radiation #aa1 #ad standard #ba ,true bearings of wind direction #ga ,vernier1 principle of #cj setting the #ca ,weather warnings #dj1 #dd1 #ec1 #ed1 #ee1 #ef1 #eg1 #eh1 #ei1 #fj1 #gc1 #gg1 #id ,wet and dry bulb hygrometer #ej ,wind1 registration of #he gauges #gi scales #gf1 #hc vane #gh ,,preface4 ,the late ,admiral ,fitzroy entertained the opinion that the various phenomena which go to form what we call 8weather0 are 8measurable at any place1 and that having these measurements at various places over a given area1 such as the ,british ,isles1 we ought to be able to foresee the peculiar results as regards the direction and force of air currents which have their distinctive weather characteristics in relation to temperature1 rainfall1 and electrical manifestations40 ,a conviction of the soundness of this opinion has induced the writer to make the present compilation1 in the hope that many who have hitherto avoided the subject of meteorology and the weather may find interesting matter1 where before all seemed dull and technical4 ,any attempt at rigid mathematical accuracy is disclaimed at the outset2 the leading principles involved in weather forecasting and storm prevision will1 however1 be stated in a sufficiently definite manner to divest the subject of the mystery in which it has hitherto seemed to be enshrined1 and thus enable the unscientific reader to become weather-wise1 and casual observers to note weather phenomena with some degree of method and precision4 ,on page #d will be found a list of works which have proved useful aids in making the present compilation4 ,the writer desires to acknowledge his indebtedness to the various authors and publishers1 and especially to ,mr4 ,strachan1 for permission to quote from his able pamphlet on 8,weather ,forecasts1 and ,storm ,prevision10 and to reproduce the valuable table on page #cg1 for ,calculating ,heights of ,mountains1 from the fourth edition of his handy 8,pocket ,meteorological ,register40 ,the publication of ,weather ,reports in the daily journals must have convinced the most indifferent that much greater importance is now attached to weather phenomena than formerly2 and this conviction will be deepened when it is remembered that a ,parliamentary grant of #aj1jjj is annually expended in support of the ,meteorological ,office and its seven fully organized observatories in this country1 while ,america expends no less a sum than #hj1jjj annually in the pursuit of weather wisdom2 and the leading nations of ,europe have also established meteorological observatories in suitable localities4 ,the balloon ascents of ,messrs4 ,glaisher and ,coxwell attracted much attention to the instruments used in estimating atmospheric phenomena1 and awakened a desire to know something of the functions of a barometer1 thermometer1 hygrometer1 c41 and especially of the classification of those important weather-warners1 clouds4 ,these subjects will be found duly noted in their order1 and every phenomenon being traced to its source1 ,solar ,radiation1 it is hoped that these pages may prove generally acceptable1 and be deemed not altogether unworthy of 8,,the ,,clerk ,,of ,,the ,,weather40 ,,weather ,,warnings4 ,the two great ,forces of ,nature are ,gravitation and ,heat1 which always act in opposition to each other4 ,,weather is the result of the action of these forces on matter1 and where one form of force is in excess of another1 changes are produced which become apparent to our senses1 or are indicated by suitable instruments4 ,,the ,,matter composing the earth on which we live is of three kinds--solid1 liquid1 and gaseous4 ,,the ,,force incessantly acting on these is the radiant heat of the sun4 ,,the ,,results of this incessant action are3-- #a4 ,,calorification1 or ,heating1 which1 besides being appreciable by our senses1 is indicated by the ,,thermometer4 #b4 ,,evaporation1 which alters the weight of the air indirectly1 by the diffusion of aqueous vapour through it4 ,this alteration of weight is indicated by the ,,barometer1 the accompanying increase of moisture being indicated by the ,,hygrometer4 #c4 ,,rarefaction1 which alters the weight of the air directly4 #d4 ,,condensation1 producing fog1 dew1 rain1 hail1 and snow2 all sufficiently apparent when they occur1 but estimated accurately only by the ,rain ,gauge1 or ,,pluviometer4 #e4 ,,motion1 producing winds1 which we are able to appreciate in the gentle breeze and the awful cyclone1 the force and velocity of which are indicated by the ,,anemometer4 #f4 ,,electrification1 producing lightning1 thunder1 magnetic phenomena1 and chemical change1 respectively indicated by the ,,electrometer1 ,,magnetometer1 and ,,ozonometer4 ,i4--,,calorification4 ,before considering in detail these results of the action of solar radiation on our globe1 an attempt to realize the immensity of this stupendous force will materially aid in the general comprehension of the subject4 ,the earth is a sphere somewhat less than #h1jjj miles in diameter2 and if we assume1 with the gifted author#a of 8,the ,phenomena of ,radiation10--8that it is about #ia1cjj1jjj miles from the sun1 and moves around it in a slightly elliptical orbit1 occupying rather more than #cfe days2 that its shape is globular1 somewhat flattened at its two extremities2 that it rotates upon its own axis in the space of #bd hours1 that axis being inclined to the annual orbit at an angle of #bc-a_/b--;if we further assume that solar radiation is of such kind and quantity as it is1 we are enabled to account for the total amount of light and heat the earth receives1 for the superior temperature and illumination of equatorial regions1 as compared with polar1 with the gradations of intermediate zones1 for the alternation of day and night1 and the annual progression of the seasons4 ,footnote #a3 ,george ,warington1 ,f4,c4,s4 8,the actuating force of every wind that blows2 of every mighty current that streams through ocean depths2 the motive cause of every particle of vapour in the air of every mist and cloud and raindrop1 is ,,solar ,,radiation4 8,the delicate tremor of the sun's surface particles1 shot hither through thirty million leagues of fine intangible ther1 has power to raise whole oceans from their beds1 and pour them down again upon the earth4 ,we are apt to measure solar heat merely by the sensation it produces on our skin1 and think it small and weak accordingly2 a good coal fire will heat us more4 ,but its true measure is the work it does4 ,judged by this standard1 its immensity is overpowering4 ,to take a single instance3 the average fall of dew in ,england is about five inches annually2 for the evaporation of the vapour necessary to produce this trifling depth of moisture1 there is expended daily an amount of heat equal to the combustion of sixty-eight tons of coal for every square mile of surface1 or1 for the whole of ,england1 #d1jjj1jjj tons4 ,compare now the size of ,england with that of the whole earth--only #a_/cchhth part2 extend the calculation to rain1 as well as dew1 the average fall of which on the whole earth is estimated at five feet annually1 or twelve times greater2 and then estimate the sum of #d1jjj1jjj #c1chh #ab #afb1fbd1jjj1jjj tons1 or about #c1jjj times as much as is annually raised in the whole world2 and we have the number of tons of coal required to produce the heat expended by the sun merely in raising vapour from the sea to give us rain during a single day40 ,illustration3 #a4 ,pouillet's ,pyrheliometer4 ,scale about #a_/h4 ,,solar ,,radiation4 ,seeing1 then1 that solar radiation plays so important a part in the production of the natural phenomena classed under the head of ,meteorology1 a description of the mode of estimating its amount will prove interesting1 and enable the reader to realize the existence of this mighty power4 ,m4 ,pouillet devised for this purpose the apparatus known as the ,,pyrheliometer1 which registers the power of parallel solar rays by the amount of heat imparted to a disc of a given diameter in a given time4 ,it consists of a flat circular vessel of steel ,a having its outside coated with lamp-black ,b4 ,a short steel tube is attached to the side opposite to that covered with lamp-black1 and the vessel is filled with mercury4 ,a registering thermometer ,c1 protected by a brass tube ,d1 is then attached1 and the whole is inverted and exposed to the sun1 as shown at ,fig4 #a4 ,the purpose of the second disc1 ,e1 is to aid in so placing the apparatus that it shall receive direct parallel rays4 ,it is obvious that if the shadow of the upper disc completely covers the lower one1 the sun's rays must be perpendicular to its blackened surface4 8,the surface on which the sun's rays here fall is known2 the quantity of mercury within the cylinder is also known2 hence we can express the effect of the sun's heat upon a given area by stating that it is competent1 in five minutes1 to raise so much mercury so many degrees in temperature40#b ,footnote #b3 ,tyndall1 8,heat a ,mode of ,motion40 ,sir ,john ,herschel also designed an instrument for observing the heating power of the sun's rays in a given time1 to which the title ,actinometer is given4 ,it consists of a ,thermometer with a long open scale and a large cylindrical bulb1 thus combining the best conditions for extreme sensibility4 ,an observation is made by exposing the instrument in the shade for one minute and noting the temperature4 ,it is then exposed to the sun's rays for one minute1 and a record of the temperature made4 ,it is again placed in the shade for one minute1 and the mean of the two shade readings being deducted from the solar reading shows the heating power of the sun's rays for one minute of time4 ,illustration3 #b4 ,herschel's ,actinometer4 ,scale about #a_/h4 ,the stimulus imparted to the study of this class of phenomena by the publications of ,professor ,tyndall's researches on ,radiant ,heat has induced a demand among ,meteorologists for instruments capable of yielding more available indications than those just described4 ,this demand has been most efficiently supplied by the ingenuity of scientists and instrument makers4 ,illustration3 #c4 ,improved ,solar ,radiation ,thermometer in ,vacuo4 ,scale about #a_/c4 ,the early form of ,solar ,radiation ,thermometer was a self-registering maximum thermometer1 with blackened bulb1 having its graduated stem1 only1 enclosed in an outer tube4 ,errors arising from terrestrial radiation and the variable cooling influences of arial currents are all obviated in the improved and patented ,solar ,radiation ,thermometer shown at ,fig4 #c1 which consists of a self-registering maximum thermometer1 having its bulb and stem dull-blackened1 in accordance with the suggestion of the ,rev4 ,f4 ,w4 ,stow1 and the whole enclosed in an outer chamber of glass1 from which the air has been completely exhausted4 ,the perfection of the vacuum in the enclosing chamber is proved by the production of a pale white phosphorescent light1 with faint stratification and transverse bands when tested by the spark from a ,ruhmkorff coil4 ,due provision is made for this by the attachment of platinum wires to the lower side of the tube1 and when tested by a syphon pressure gauge1 the vacua have been proved to exist to within #a_/ejth of an inch of pressure4 ,it will thus be seen that the indications are preserved from errors arising from atmospheric currents1 and from the absorption of heat by aqueous or other vapours1 the whole of the solar heat passing through the vacuum direct to the blackened bulb4 ,the contained mercury expanding1 carries the recording index to the highest point1 and thus is obtained a registration of the maximum amount of solar radiation during the twenty-four hours4 ,the great advantage accruing from the high degree of perfection to which this instrument has been brought is1 uniformity of construction1 which renders the observations made at different stations intercomparable4 ,an enlarged view of the thermometer is given at ,fig4 #c1 showing the platinum wire terminations1 whereby the vacuum is tested4 ,the ,rev4 ,fenwick ,w4 ,stow thus directs the manner in which the solar radiation thermometer should be used3-- #a4 ,place the instrument four feet above the ground1 in an open space1 ,fig4 #d1 with its bulb directed towards the ,s4,e4 ,it is necessary that the globular part of the external glass should not be placed in contact with or very near to any substance1 but that the air should circulate round it freely4 ,thus placed1 its readings will be affected only by direct sunshine and by the temperature of the air4 #b4 ,one of the most convenient ways of fixing the instrument will be to allow its stem to fit into and rest upon two wooden collars fastened across the ends of a narrow slip of board1 which is nailed in its centre upon a post steadied by lateral supports 7,fig4 #d74 #c4 ,the maximum temperature of the air in shade should be taken by a thermometer placed on a stand in an open situation4 ,any stand which thoroughly screens it from the sun1 and exposes it to a free circulation of air1 will do for the purpose4 #d4 ,the difference between the maxima in sun and shade1 thus taken1 is a measure of the amount of solar radiation4 ,illustration3 #d4 ,solar ,radiation ,thermometer1 black bulb and stem in vacuo1 on #d feet stand4 ,scale about #a_/bj4 ,the remarkable phenomenon recently discovered by ,mr4 ,crookes1 in which light is apparently converted into motion1 has1 at the suggestion of ,mr4 ,strachan1 received an interesting application to meteorology4 ,the arrangement is shown at ,fig4 #e1 where a ,solar ,radiation ,thermometer has a ,crookes' ,radiometer attached to it1 which1 in addition to forming an efficient test as to the perfection of the vacuum1 will1 it is hoped1 aid in eventually establishing a relation between intensity of radiation1 as shown by the thermometer1 and the number of revolutions of the radiometer4 ,the instrument has so recently been devised that any positive statement as to its usefulness would be premature2 it may1 however1 prove a valuable auxiliary to the solar thermometer1 and eventually be so far improved as to become a more definite exponent of solar radiation than the thermometer4 ,illustration3 #e4 ,radio-,solar ,thermometer4 ,scale about #a_/d4 ,,terrestrial ,,radiation4 ,it is an established fact1 confirmed by careful experiments1 that a mutual interchange of heat is constantly going on between all bodies freely exposed to view of each other1 thus tending to establish a state of equilibrium4 ,it has further been ascertained that1 as the mean temperature of the earth remains unchanged1 8it necessarily follows that it emits by radiation from and through the surface of its atmosphere1 on an average1 the exact amount of heat it receives from the sun40 ,this process commences slowly at sunset1 and proceeds with great rapidity at and after midnight1 attaining its maximum effect in a long night1 in perfect calm1 under a cloudless sky1 resulting in the condensation of vapour in the form of dew1 or hoar-frost1 when the temperature of the surface-air is reduced to the dew-point4#c ,footnote #c3 ,see page #dg4 ,the extent to which heat thus escapes by radiation under varying conditions of sky is measured by a ,self-registering ,terrestrial ,minimum ,thermometer1 the bulb of which is placed over short grass1 and 8a thermometer so exposed under a clear sky always marks several degrees below the temperature of the air1 and its depression affords a rude measure of the facility for the escape of heat afforded under the circumstances of exposure40#d ,footnote #d3 ,herschel4 ,illustration3 #f4 ,terrestrial ,radiation ,thermometer4 ,scale about #a_/f4 ,illustration3 #g4 ,improved ,cylinder ,jacket ,terrestrial ,minimum ,thermometer4 ,scale about #a_/ab4 ,fig4 #f shows the ordinary spherical bulb thermometer employed for this purpose1 and ,fig4 #g the improved ,cylinder ,jacket ,thermometer1 which1 by exposing a larger surface of spirit to the air1 gives an instrument possessing an amount of sensibility in no way inferior to that of mercury4 ,there is a drawback to the use of these thermometers enclosed in outer tubes1 arising from moisture getting into the outer cylinder or jacket1 and frequently preventing the observer from reading the thermometer4 ,this has recently been removed by making a perfectly ground joint of glass 7analogous to a glass stopper in a bottle7 as a substitute for the old form of packing at the open end of the tube1 the other end being fused into contact with the outer cylinder to keep it in its place4 ,the intrusion and condensation of moisture thus becomes impossible1 while the scale is protected from corrosion or abrasion4 ,this 8ground socket0 arrangement is shown at ,fig4 #h4 ,illustration3 #h4 ,ground ,socket ,minimum ,thermometer4 ,scale about #a_/d4 ,radiation from the earth upwards proceeds with great rapidity under a cloudless sky1 but a passing cloud1 or the presence even of invisible aqueous vapour in the air1 is sufficient to effect a marked retardation1 as is beautifully illustrated by ,sir ,john ,leslie's thrioscope1 shown at ,fig4 #i1 which consists of a vertical glass tube1 having a bore so fine that a little coloured liquid is supported in it by the mere force of cohesion4 ,each end of the tube terminates in a glass bulb containing air4 ,a scale1 having its zero in the middle1 is attached to the tube1 and the bulb ,a is enclosed in a highly polished sphere of brass4 ,the upper bulb ,b is blackened1 and placed in the centre of a highly-gilt and polished metallic cup1 having a movable cover ,f4 ,these outer metallic coverings protect the bulbs from extraneous sources of heat4 ,so long as the upper bulb is covered1 the liquid in the tube stands at zero on the scale1 but immediately on its removal radiation commences1 the air contained in ,b contracts1 while the elasticity of that contained in ,a forces the liquid up the tube to a height directly proportionate to the rapidity of the radiation4 ,illustration3 #i4 thrioscope4 ,scale about #a_/g4 ,,shade ,,temperature4 ,self-registering ,maximum ,thermometers are made in two ways4 ,in the first1 the index is a small portion of the mercurial column separated from it by a minute air bubble4 ,the noontide heat expands the mercury1 and the subsequent contraction as the temperature decreases affects only that portion of the mercury in connection with the bulb1 leaving the disconnected portion to register the maximum temperature4 ,in the second form the tube is ingeniously contracted just outside the bulb1 so that the mercury extruded from the bulb by expansion cannot return by the mere force of cohesion1 but remains to register the highest temperature4 ,illustration3 #aj4 ,self-registering ,maximum ,thermometer4 ,scale about #a_/e4 ,there is a modification of this latter form produced by the addition of a supplementary chamber just outside the bulb and over the column1 from which1 as expansion proceeds1 the mercury flows by gravitation1 but into which it cannot return until1 as in the other forms1 the instrument is readjusted for a new observation1 by unhooking the bulb end and lowering it until the mercury flows into its place4 ,illustration3 #aa4 ,self-registering ,minimum ,thermometer4 ,scale about #a_/e4 ,self-registering ,minimum ,thermometers are of two kinds1--spirit and mercurial4 ,fig4 #ab shows one of ,rutherford's ,alcohol ,minimum ,thermometers1 which will be seen to consist of a bulb and tube attached to a scale1 which latter may be either of wood1 glass1 or metal4 ,the tube contains an index of black glass4 ,illustration3 #ab4 ,self-registering ,minimum ,thermometer4 ,scale about #a_/e4 ,the ,thermometer is 8set0 for observation by slightly raising the bulb end until the index slides to the extreme end of the column of spirit4 ,it is then suspended in the shade with the bulb end a little lower than the other4 ,the contraction of the spirit consequent on a fall of temperature draws the index back1 but a subsequent expansion does not carry it forward1 it remains at the lowest point to which the spirit has contracted to register the minimum temperature4 ,a very useful modification of this instrument is made for gardeners and general horticultural purposes1 in which the scale is of cast zinc with raised figures1 which being filed off flush after the whole has been painted of a dark colour are easily legible at a little distance4 ,the advantage of alcohol for the indication of very low temperatures is that it has never been frozen4#e ,footnote #e3 ,mercury freezes at -#ci ,f4 ,fig4 #ac shows a set of ,maximum and ,minimum and ,wet and ,dry ,bulb ,thermometers1 with incorrodible porcelain scales1 suspended on a mahogany screen4 ,instruments of this quality are generally engine-divided on the stem1 and if1 in addition to this1 they are verified by comparison with standard instruments at the ,kew ,observatory1 they may be regarded as standards1 and employed for accurate scientific observations4 ,illustration3 #ac4 ,standard ,set of ,instruments on ,screen4 ,scale about #a_/f4 ,six's ,self-registering ,thermometer consists of a long tubular bulb1 united to a smaller tube more than twice its length1 and bent twice1 like a syphon1 so that the larger tube is in the centre1 while the smaller one terminates at the top1 on the right hand1 in a pear-shaped bulb1 as shown in the cut 7,fig4 #ad74 ,this bulb1 and the tube in connection with it1 are partly filled with spirit2 the long central bulb and its connecting tube are completely filled1 while the lower portion of the syphon is filled with mercury4 ,a steel index1 prevented from falling by a hair tied round it1 to act as a spring1 moves in the spirit in each of the side tubes4 ,the scale on the left hand has the zero at the top1 and that on the right at the bottom4 ,when setting the instrument1 the indices are brought into contact with the mercury by passing a small magnet down the outside of each tube4 ,then1 should a rise of temperature take place1 the spirit in the central bulb expands1 forcing down the mercury in the left hand tube and causing it to rise in the right1 and vice versa for a diminution of temperature4 ,it should be always used and carried upright1 and the indices should be drawn gently down by the magnet into contact with the mercury2 and1 when a reading is taken1 the ends of the indices nearest the mercury indicate the maximum and minimum temperatures which have been attained during the stated hours of observation4 ,illustration3 #ad4 ,six's ,thermometer4 ,scale about #a_/g4 ,six's form of thermometer has been extensively used for ascertaining deep sea temperatures4 ,illustration3 #ae4 ,deep ,sea ,maximum and ,minimum ,registering ,thermometer4 ,scale about #a_/e4 ,evaporation and the mechanical action of winds keep up a constant circulating motion of the ocean1 the currents of which tend to equalize temperature4 ,the most important of these is known as the ,gulf ,stream1 taking its name from the ,gulf of ,mexico1 out of which it flows at a velocity sometimes of five miles an hour1 and in a width of not less than fifty miles4 ,it has an important effect on the climate of ,great ,britain1 and of all lands subject to its influence1 its temperature as it leaves the ,gulf of ,mexico being #he ,f41 diminishing to #ge off the coast of ,labrador1 and still further as it nears northern latitudes4 ,observations on the temperature of the ocean are therefore included in the scope of meteorology1 and are ascertained by the use of thermometers of special construction 7,fig4 #ae74 ,in the earlier experiments made for ascertaining the temperature of the ocean at a depth of #ae1jjj feet1 where the pressure is equal to three tons on the square inch1 it was found that a considerable error occurred in the indications in consequence of this enormous pressure2 accordingly the central elongated bulb of the ordinary ,six's ,thermometer 7see page #ai7 is shortened and enclosed in an outer bulb nearly filled with spirit1 which1 while effectually relieving the thermometer bulb from undue pressure1 allows any change to be at once transmitted to it1 and thus secures the registration of the exact temperature4 ,the arrangement possesses the further advantage of making the instrument stronger1 more compact1 and more capable of resisting such comparatively rough treatment as it would receive on board ship4 ,the honour of constructing the first thermometer1 which was an ,air and ,spirit ,thermometer1 is ascribed to ,galileo2 it assumed a practical shape in #afbj1 at the hands of ,drebel1 a ,dutch physician4 ,hailey substituted mercury for spirit in #afig2 ,raumur improved the instrument in #agcj1 and ,fahrenheit in #agdi4 ,more recently the instrument has been perfected by the scales being graduated on the actual stem of the instrument4 ,for many years it was exclusively used by chemists and men of science2 it afterwards received numerous applications in the arts and manufactures2 and is now considered an essential in every household4 ,thermometers are instruments for measuring temperature by the contraction or expansion of fluids in enclosed tubes4 ,the tubes1 which are of glass1 have spherical1 cylindrical1 or spiral bulbs blown on to one end2 they have also an exceedingly fine bore1 and when mercury or spirit is enclosed in them these fluids1 in contracting and expanding with variations of temperature1 indicate degrees of heat in relation to two fixed points--viz41 the freezing and boiling points of water4 ,care is taken to exclude all air before sealing1 so that the upper portion of the tube inside shall be a perfect vacuum1 and thus offer no resistance to the free expansion of the mercury4 ,in graduating1 or dividing the scales1 the points at which the mercury remains stationary in melting ice and boiling water are first marked on the stem1 and the intervening space divided into as many equal parts as are necessary to constitute the scales of ,fahrenheit1 ,raumur1 or ,celsius1 the last being known as the ,centigrade 7hundred steps7 scale1 from the circumstance of the space between the freezing and boiling points of water being divided into one hundred equal parts 7,fig4 #af74 ,illustration3 #af4 ,comparison of ,thermometer ,scales4 ,scale about #a_/e4 ,illustration3 #ag4 8,legible0 ,scale ,thermometer4 ,scale about #a_/e4 ,,graduation ,,of ,,thermometers4--,when the fluid 7either mercury or spirit7 has been enclosed in the hermetically sealed tube1 it becomes necessary1 in order that its indications may be comparable with those of other instruments1 that a scale having at least two fixed points should be attached to it4 ,as it has been found that the temperature of melting ice or freezing water is always constant1 the height at which the fluid rests in a mixture of ice and water has been chosen as one point from which to graduate the scale4 ,it has been also found that with the barometer at #biije the boiling-point of water is also constant1 and when a thermometer is immersed in pure distilled water heated to ebullition1 the point at which the mercury remains immovable is1 like the freezing-point1 carefully marked1 the tube is then calibrated and divided as shown in ,fig4 #af4 ,the zero of the scales of ,raumur and ,centigrade is the freezing-point of water1 marked1 in each case1 #j1 while the intervening space1 up to the boiling-point of water1 is divided1 in the former case1 into #hj parts1 and in the latter to #ajj4 ,in the ,fahrenheit scale1 the freezing-point is represented at #cb1 and the boiling-point at #bab1 the intervening space being divided into #ahj1 which admits of extension above and below the points named1 a good thermometer being available for temperature up to #fbj ,fahr4 ,the use of the ,raumur scale is confined almost exclusively to ,russia and the north of ,germany1 while the ,centigrade scale is used throughout the rest of ,europe4 ,the ,fahrenheit scale is confined to ,england and her colonies1 and to the ,united ,states of ,america4 ,illustration3 #ah4 ,gridiron-bulb ,thermometer4 ,scale about #a_/e4 ,circumstances sometimes arise in which it becomes necessary to convert readings from one scale into those of the others1 according to the following rules3-- #a4 ,to convert ,centigrade degrees into degrees of ,fahrenheit1 multiply by #i1 divide the product by #e1 and add #cb4 #b4 ,to convert ,fahrenheit degrees into degrees of ,centigrade1 subtract #cb1 multiply by #e1 and divide by #i4 #c4 ,to convert ,raumur degrees into degrees of ,fahrenheit1 multiply by #i1 divide by #d1 and add #cb4f #d4 ,to convert ,raumur degrees into degrees of ,centigrade1 multiply by #e and divide by #d4g ,footnote #f3 #h ,r #ej ,f4 ,footnote #g3 #h ,r #aj ,c4 ,for the production of continuous records1 the ,meteorological ,committee of the ,royal ,society have adopted an instrument called a ,thermograph1 or self-recording wet and dry bulb thermometer1 which is largely aided by photography4 ,the bulbs of the thermometers are necessarily placed in the open air1 and at a suitable distance from any wall or other radiating surface2 the tubes are of sufficient length to admit of their being brought inside the building1 in due proximity to the recording apparatus placed in a chamber from which daylight is rigidly excluded4 ,illustration3 #ai4 ,thermograph and ,self-recording ,hygrometer4 ,scale about #a_/ah4 ,the essential conditions in such an apparatus are3--#a4 ,a means of denoting the height of the mercurial column in the stem of a thermometer in relation to a fixed horizontal line4 #b4 ,a time scale denoting the exact moment at which the atmosphere reached the temperature indicated by the mark4 #c4 ,as the marks are produced chemically1 and not mechanically 7as in the ,anemograph71 a dark room4 ,a description of the drawing on page #bc will best show how very efficiently1 through the ingenuity of ,mr4 ,,beckley1 these conditions have been obtained3--,s1 wet bulb thermometer2 ,t1 atmospheric thermometer2 ,b1 screw for adjusting thermometers2 ,c ,c1 paraffin lamps or gaslights2 ,d ,d1 condensers1 concentrating the light on the mirrors ,r ,r2 ,r ,r1 mirrors reflecting light through air-speck in thermometers ,v ,v2 ,e ,e1 slits through which light passes from mirrors ,r ,r2 ,f ,f1 photographic lenses1 producing image of air-speck from both thermometers on cylinder ,g2 ,g1 revolving cylinder or drum carrying photographic paper2 ,h1 clock1 turning cylinder ,g round once in #dh hours2 ,i1 shutter to intercept light four minutes every two hours2 leaving white time-line on developing latent image4 ,,ii4--,,evaporation4 ,solar heat rarefies the air by driving its particles asunder2 it also vaporises water from the surface of river1 lake1 and ocean1 diffusing the vapour through the atmosphere4 ,great interest attaches to the subject of ,evaporation1 on account of its connection with rainfall and water supply4 ,it is to be regretted1 therefore1 that the results hitherto obtained in the endeavour to measure its rate and quantity do not merit much confidence as regards their applicability to the evaporation occurring in nature1 owing to the exceptional manner in which the observations have been made4 ,there is this uncertainty about evaporation1 that all the experiments relate to that taking place from an exposed water surface of a1 comparatively speaking1 infinitesimally small area1 and can therefore have but a very partial applicability to the conditions occurring in nature4 ,there are two main reasons for this statement4 ,firstly1 the proportion of the surface of the land on the earth which is covered with lakes and rivers is very limited1 and the experiments above indicated throw no light on the evaporation from the soil4 ,secondly1 the evaporation from the surface of a small atmometer erected on the ground1 with comparatively dry air all around it1 is certainly very different from that which would take place from an equal area in the centre of a large water surface1 such as a lake4 ,it is of course easy to make experiments on the evaporation from the soil by means of a balance atmometer1 but in order that these should possess a practical value1 the investigation must be extended so as to include a wide variety of soils1 c41 c4 ,as regards the second point which has been raised1 it is recommended by the ,vienna ,congress to erect atmometers in the centre of water surfaces2 but it is not a very easy matter to conduct such experiments with accuracy1 owing to the risk of in-splashing from waves4 ,illustration3 #bj4 ,atmidometer4 ,scale about #a_/e4 ,,babington',s ,,atmidometer measures evaporation from water1 ice1 or snow1 and in form resembles a hydrometer1 with the difference that the stem bears a scale graduated to grains and half grains1 and is surmounted by a light1 shallow copper pan4 ,when in use1 the hydrometer-like instrument is immersed in a glass vessel having a hole in the cover1 through which the stem protrudes4 ,the copper pan is then placed on the top1 and sufficient water1 ice1 or snow placed therein to sink the stem to the zero of the scale4 ,as the evaporation proceeds1 the stem rises2 and1 if the time of commencing the experiment is noted1 the rate as well as the amount of evaporation is indicated in grains4 ,,iii4--,,rarefaction4 ,the diffusion of aqueous vapour through the air and the rarefying influence of heat jointly effect an alteration in the weight of the atmosphere4 ,this alteration of weight is determined by the ,barometer1 an instrument invented by ,,torricelli1 in #afdc1 and in so perfect a form that in its essential features it has not been superseded4 ,illustration3 #ba4 and #bb4 ,construction of ,barometer4 ,scale about #a_/ah4 ,the mode of construction is illustrated by ,figs4 #ba and #bb4 ,it consists in hermetically sealing a glass tube about three feet long and filling it with mercury4 ,the finger is placed over the open end of the tube1 which is then inverted and placed in a cistern of mercury and the finger withdrawn4 ,the left-hand figure shows the result2 the mercury is seen to fall some three or four inches1 leaving an empty space at the top of the tube1 which is called the 8,torricellian vacuum40 ,the mercury is prevented from falling lower than is shown1 by the external pressure of the atmosphere on the cistern4 ,the weight of this column1 therefore1 represents the weight or pressure of a corresponding column of air many miles in height2 and so close is the relation between the column of mercury and the external air that the height of the former changes with the slightest variation in the weight of the latter1 and the instrument thus becomes a measure of the weight of the air1 from which property its name is derived1 the ,greek words baros and metron signifying respectively 8weight0 and 8measure40 ,when the mercury in the barometer tube falls1 that in the cistern rises in corresponding proportion1 and vice versa1 so that there is an ever-varying relation between the level of the mercury in the tube and the mercury in the cistern1 which affects the accuracy of the readings4 ,in ,m4 ,fortin's cistern this difficulty is obviated by the use of a glass1 with flexible leather bottom and a brass adjusting screw1 as shown in the cut4 ,through the top of the cistern is inserted a small ivory point1 the lower end of which corresponds with the zero of the scale2 and1 to secure uniformity1 the level of the mercury in the cistern should be adjusted by the screw at each observation1 until the ivory point appears to touch its own reflection on the surface4 ,the reading is then taken4 ,illustration3 #bc4 ,fortin's ,cistern4 ,scale about #a_/f4 ,in making barometric observations for comparison with others1 it is necessary that all should be reduced to the common temperature of #cb ,f41 and for this purpose tables have been calculated which will be found to save much time4 ,tables also for reducing observations of the barometer to sea level1 an operation equally indispensable with the other corrections to make the readings intercomparable1 have been published by direction of the ,meteorological ,committee4 ,for the ,british ,isles the mean sea-level at ,liverpool has been selected by the ,ordnance ,survey as their datum1 and the height of any station may be ascertained by first noting the nearest ,ordnance ,bench ,mark thus 1 and purchasing that portion of the ,ordnance map which includes the station1 near to which the ,bench ,mark will be found with the height above sea-level duly entered4 ,the levellings made for railways will also furnish the desired information4 ,failing both these1 the observer should select two or more of the stations nearest his locality for which official ,meteorological ,reports are published daily in the ,times and other journals2 and taking observations of his barometer at #h a4m41 for a few weeks1 should compare them with the mean of the observations at those stations4 ,the comparison should be omitted when the barometer pressure is not steady4 ,illustration3 #bd4 ,error of ,capillarity4 ,scale about #a_/b4 ,illustration3 #be4 ,standard ,barometer4 ,scale about #a_/g4 ,a ,standard ,barometer is constructed on ,,fortin',s principle1 and should have its tube about half an inch bore1 enclosed in a brass body having at its upper end two vertical openings1 in which the vernier works4 ,the mercury is seen through these openings1 aided by light reflected from a white opaque glass reflector let into the mahogany board behind4 ,the scale is divided on one side into ,english inches and #bjths1 and may have on the other ,french millimetres1 the vernier enabling a reading to be taken1 in each case respectively1 of #a_/ejjth of an inch and #a_/ajth of a millimetre4 ,in making the instrument1 the mercury is boiled in the tube1 to ensure the complete exclusion of air and moisture2 while ,,fortin',s principle of cistern ensures a constant level from whence to take the readings4 ,a sensitive thermometer with scale1 engine-divided on stem1 is attached to the brass mount1 which is perforated to admit the attenuated bulb of the thermometer into absolute contact with the glass tube of the barometer1 to ensure its indicating the same temperature as the contained mercury4 ,the instrument is suspended by a ring from a brass bracket attached to a mahogany board1 and the lower end passes through a larger ring having three screws for adjusting it vertically4 ,a 8reading0 is taken in the following manner3--#a4 ,note the temperature by the attached thermometer4 #b4 ,raise or lower the mercury in the cistern by turning the screw underneath until the reflected image of the ivory point on the mercury seems to be in contact with the ivory itself4 ,by the milled head at the side1 the vernier is adjusted until its lower edge just touches the top of the mercurial column1 the scale and vernier then indicate the height of the barometer in inches1 #ajths1 #ajjths1 and #ajjjths4 ,high-class instruments1 such as that here described1 yield exact readings2 but1 in order to note them accurately1 it is important that the eye1 the zero edge of the vernier1 the top of the mercurial column1 and the back of the vernier should be in the same horizontal plane2 conditions which may be obtained after some practice4 ,the accompanying illustration shows a form of barometer which1 though not much used in this country1 is deservedly popular on the ,continent as a standard station barometer4 ,it is called a ,syphon ,barometer1 and was designed by ,gay-,lussac4 ,the open end of the tube is bent up in the form of a syphon1 the short limb being from six to eight inches long2 it is furnished with metal scales and verniers1 and is mounted on a mahogany board with attached thermometer4 ,these barometers require no correction for capillarity or capacity1 each surface of mercury being equally depressed by capillary attraction1 and the quantity of mercury falling from the long limb occupies the same space in the short limb4 ,the usual correction for temperature must1 however1 be applied4 ,a scale of inches1 measured from a zero point taken near the bend of the tube1 furnishes the means of measuring the long and short columns4 ,the difference of readings is the height of the barometer4 ,the ,,vernier is a movable scale for subdividing parts of a fixed scale1 and was first applied to that purpose by its inventor1 ,m4 ,,pierre ,,vernier1 in #afcj4 ,in the barometer the parts to be divided are inches1 which by the aid of this invention are subdivided into #ajths1 #ajjths1 and #ajjjths4 ,fig4 #bg shows the scale of a standard barometer divided into #a_/b-ajths1 or #je of an inch4 ,the ,vernier ,c ,d is made equal to #bd of such divisions1 and is divided into #be equal parts1 from whence it follows that one division on the scale is #a_/beth of #je larger than one on the vernier1 so that it shows a difference of #jjb of an inch4 ,the vernier reads #j1 or zero1 upwards2 ,d1 therefore1 indicates the top of the mercurial column4 ,illustration3 #bf4 ,syphon ,barometer4 ,scale about #a_/ab4 ,in ,fig4 #bg1 zero on the vernier is exactly in line with #bi inches and #e_/ajths of the fixed scale2 the reading1 therefore1 is #biejj inches4 ,the vernier line a falls short of a division of the scale by #jjb-;inch2 b1 by #jjd2 c1 by #jjf2 d1 by #jjh2 and the succeeding line by #jaj4 ,if the vernier be adjusted to make a coincide with z on the scale1 it will have moved through #jjb-;inch2 and if #a on the vernier be moved to coincide with y on the scale1 the space measured will be #jaj-;inch4 ,consequently1 the figures #a1 #b1 #c1 #d1 #e1 on the vernier1 measure #ajjths1 and the intermediate lines even #ajjjths of an inch4 ,in ,fig4 #bh the zero of the vernier is between #bife and #bigj on the scale4 ,glancing up the vernier and scale1 the second line above #c will be found in a direct line with one on the scale2 this gives #jc and #jjd to add to #bife1 so that the actual reading is #bifhd4 ,in those instances where no line on the vernier is found precisely to coincide with a line on the scale1 and doubt arises as to which to select from two equally coincident lines1 the rule is to take the intermediate #ajjjth of an inch4 ,illustration3 #bg4 and #bh4 ,the ,vernier4 ,for household and marine barometers such minute subdivisions of the scale are unnecessary1 and the scales of such instruments are therefore divided only to #ajths1 and the verniers made only to read to #ajjths of an inch1 which is effected by making the vernier #i_/ajths or #aa_/ajths of an inch long1 and dividing it into #aj equal parts4 ,in 8taking a reading0 it is important that it should be done as quickly as possible1 as the heat from the body and the hand is sufficient to interfere with that accuracy which is necessary where the intention is to compare the readings with those made by other observers4 ,this facility is soon acquired by a little practice4 ,illustration3 #bi4 ,farmer's ,barometer4 ,scale about #a_/g4 ,pediment ,household ,barometers1 though not so imposing in appearance as the ,wheel ,barometer1 yield direct readings without the intervention of the mechanical appliances necessary for moving a needle over an extended dial4 ,their mountings are for the most part in oak1 walnut1 and other woods1 the scales are of ivory1 porcelain1 or enamelled glass1 and in their graduation due regard is paid to the relative proportions of cistern and tube1 so that the conditions essential to the production of a ,standard ,barometer are very closely attained4 ,in common with other barometers1 it should hang in the shade in a vertical position1 so that light may be seen through the tube4 ,as a purchaser would receive it in what is called a 8portable0 state1 it will be necessary on first suspending it to take the pinion key1 fit it on the square-headed pin at the bottom of the instrument1 and turn gently to the left till the screw stops4 ,the effect of this is to lower the base of the cistern1 and allow the mercury in the tube to fall to its proper level4 ,the key should then be replaced for use in moving the vernier4 ,to make this kind of ,barometer portable for travelling it should be unhung1 very gradually sloped until the mercury is at the top of the tube1 when1 the instrument being upside down1 the base of the cistern is screwed up by turning the pinion key gently to the right until it stops4 ,care should be taken to avoid concussion1 and to have the cistern end always uppermost1 or the instrument lying flat4 ,fig4 #bi shows a useful form of barometer for the farmer1 combining as it does three instruments in one1 for the thermometer on the right hand of the scale having its bulb covered with muslin kept moist by communication with a cistern of water enables the two thermometers to be employed as a ,hygrometer1 the use of which is described at page #ej4 ,this barometer should be suspended in a place where it will be exposed as much as possible to the external air1 but not in sunshine4 ,illustration3 #cj4 ,wheel ,barometer4 ,scale about #a_/f4 ,in ,wheel ,barometers the varying height of a column of mercury is shown by the movement of a needle on a divided circular dial1 by adopting the syphon form of barometer tube1 concealed behind the dial and frame4 ,an iron or glass float sustained by the mercury in the open branch 7,fig4 #ca7 is suspended by a counterbalance a little lighter than itself4 ,the axis of the pulley has the needle attached to it1 and consequently moves the needle with the rise and fall of the mercury4 ,it is obvious1 therefore1 that if the atmospheric pressure increases the float falls and the needle turns to the right1 and if it diminishes the needle turns in the opposite direction4 ,the divisions on the scale represent inches1 tenths1 and hundredths in the rise and fall of a column of mercury1 and these can be read with great facility1 as one inch occupies the space of six or more on this very open scale1 according to size of dial 7,fig4 #cj74 ,the wording is arbitrary1 and indicates the probable weather that may be expected4 ,important improvements have recently been effected in this form of household barometers1 so that they may be recommended as good weather indicators where facility of reading is a desideratum4 ,illustration3 #ca4 ,mechanism of ,wheel ,barometer4 ,scale about #a_/h4 ,since the more scientific 8,pediment0 has attained so high a degree of popularity1 a certain amount of unmerited obloquy has attached itself to the ,dial or ,wheel ,barometer invented by ,dr4 ,hooke4 ,it must be conceded that the standard form of pediment barometers in which the height of the mercury is seen at a glance is more strictly an 8instrument of precision10 but it should not be forgotten1 although a delicate mechanism intervenes between the mercury and the observer1 it is so arranged that a tenth of an inch rise or fall causes a movement of the index over an inch of space4 ,the ,aneroid ,barometer indicates variations in atmospheric pressure by the elevation and depression of the sides of an elastic metallic box from which the air is exhausted and which is kept from complete collapse by a powerful spring4 ,in cases where extreme accuracy is not indispensable1 the portability and sensibility of this instrument recommend it for use by tourists and fishermen4 ,it is 8quick in showing the variations of atmospheric pressure40#h 8,the ,aneroid readings may be safely depended upon40#i 8,its movements are always consistent40#aj 8,atmospheric changes are indicated first by the ,aneroid40#aa ,it is especially adapted for determining mountain altitudes1 some being furnished with a scale of feet1 enabling the observer to read off the height by direct observation1 and if adjusted once a year by comparison with a mercurial standard is quite trustworthy4 ,it is fully described in a small pamphlet entitled 8,the ,aneroid ,barometer3 ,how to ,buy1 and ,how to ,use it10 by a ,fellow of the ,meteorological ,society4 ,footnote #h3 ,admiral ,fitzroy4 ,footnote #i3 ,james ,glaisher1 ,esq41 ,f4,r4,s4 ,footnote #aj3 ,james ,belville1 ,esq41 ,royal ,observatory1 ,greenwich4 ,footnote #aa3 ,sir ,leopold ,mc,clintock4 ,illustration3 #cb4 ,aneroid ,barometer4 ,full size4 ,by a suitable arrangement of clockwork1 revolving a cylinder bearing prepared paper1 the aneroid barometer forms an admirable self-recording instrument1 showing at a glance the height of the barometer3 whether it is falling or rising1 for how long it has been doing so1 and at what rate the change is taking place1 whether at the rate of #a_/ajth per hour1 or #a_/ajth in twenty-four hours--facts which can only be obtained by very frequent and regular observations from an ordinary barometer1 but which are nevertheless essential to a reliable 8weather forecast40#ab ,footnote #ab3 ,the ,aneroid ,barometer3 ,how to ,buy and ,how to ,use it4 ,by a ,fellow of the ,meteorological ,society4 ,post free for six stamps1 from any bookseller or optician4 ,the height of mountains may also be determined by the temperature at which water boils1 as this depends on the pressure of the atmosphere1 and according to ,deschanel1 8just as we can determine the boiling-point of water when the external pressure is given1 so if the boiling-point be known we can determine the external pressure10 and as this varies with the elevation above sea-level1 the boiling-point of water also varies4 ,these facts induced ,wollaston to attempt the determination of heights of mountains by an apparatus which he called the ,barometric ,thermometer1 subsequently modified by ,regnault and called a ,hypsometer1 but now more generally known as a ,boiling-point ,thermometer4 ,illustration3 #cc4 ,boiling-point ,thermometer4 ,scale about #a_/c4 ,a portable form of boiling-point thermometer is shown at ,fig4 #cc1 which is much used by ,alpine travellers1 and forms a trustworthy check on the aneroid and barometer4 ,,concise ,,tables ,,for ,,calculating ,,heights ,,by ,,means ,,of ,,barometer ,,or ,,aneroid1 ,,and ,,also ,,by ,,the ,,boiling-,,point ,,thermometer4 ---------------------------------------- ------------------ ,boiling- ,bartr4 point of at lower ,,barometer ,,at ,,upper ,,station4--,,inches4 ,water for ,station4 pressure in -------------------------------- next col4 ,in4 #cj #bi #bh #bg #bf #be #bd #bc ---------------------------------------- ----------- #bacgh #ca #hei #hgc #hhi #ije #iba #ici #ieg #igg #babac #cj 4444 #hhh #ijd #ibj #icg #iee #igd #iid #bajdc #bi 4444 4444 #iai #icf #iec #iga #iiaajab #bjhfg #bh 4444 4444 4444 #ieb #igj #ihiajjiajbh #bjfhg #bg ,factor ,a4 #ihhajjgajbhajej #bjeja #bf 4444 4444 4444 4444 4444 #ajbgajdhajgj #bjcji #be 4444 4444 4444 4444 4444 4444 #ajfiajib #bjaaa #bd 4444 4444 4444 4444 4444 4444 4444 #aaae ---------------------------------------- ------------------ ---------------------------------------- ------------------ ,boiling- ,bartr4 point of at lower ,,barometer ,,at ,,upper ,,station4--,,inches4 ,water for ,station4 pressure in -------------------------------- next col4 ,in4 #bb #ba #bj #ai #ah #ag #af #ae ---------------------------------------- ----------- #bacgh #ca #iihajbjajdcajfhajieaabdaaeeaahh #babac #cj #ajaeajchajfbajhgaaaeaaddaagfabaj #bajdc #bi #ajccajefajhaaajgaaceaafeaaihabcc #bjhfg #bh #ajeaajgeaajjaabgaaefaahgabbjabeg #bjfhg #bg #ajgcajigaabbaaejaahjabaaabdfabhc #bjeja #bf #ajicaaahaadeaagcabjcabcfabgaacji #bjcji #be #aaafaadaaafiaaihabbiabfbabiiacch #bjaaa #bd #aadjaaffaaidabbdabefabijacbgacfg #aiije #bc #aafdaaiaabbjabeaabhdacaiacehacii #aifib #bb 4444 #abahabdhabhjacadacejacijadcc #aidga #ba 4444 4444 #abghacajacdfachcadbdadfi #aibda #bj 4444 4444 4444 #acdcachjadaiadfaaejg #aijjj #ai 4444 4444 4444 4444 #adafadegaejjaedh #ahgej #ah 4444 4444 ,factor ,a4 4444 #adigaedbaeib #ahdhg #ag 4444 4444 4444 4444 4444 4444 #aehhafci #ahbaj #af 4444 4444 4444 4444 4444 4444 4444 #afij #agibj #ae 4444 4444 4444 4444 4444 4444 4444 4444 ---------------------------------------- ------------------ -------------------------------------- ,height ,d4 in #a1jjj additive4,latitude4 ,c4 --------------------- feet4 ,mean ,factor -----------------------------------,temp erature4 ,b4 #b #e #j #bg -------------------- #d #aa #aj #be #aj #jiea #f #ag #bj #bj #bj #jigc #h #bc #cj #ad #cj #jiif #aj #cj #dj #jf #dj #ajah #ab #cg #de #jj #ej #ajdj #ad #dd #ej -#je #fj #ajfb #af #eb #fj -#ac #gj #ajhd #ah #fj #gj -#bj #hj #aabg ---------------------------------------- --------------- ,,rule ,i4--,if the temperature of boiling water be observed at either or both ,stations1 find the equivalent pressure in the #bnd column1 and calculate the height as for barometer4 ,,rule ,,ii4--,the readings of the ,barometer being corrected and reduced to #cb ,f41 multiply the difference of pressure between the ,stations by factor ,a1 found in line with pressure at lower ,station1 and under that at upper ,station2 multiply again by factor ,b1 corresponding to the mean temperature of the air at the ,station2 apply as many times ,c as there are thousand feet in the height1 corresponding to the latitude2 and add ,d1 the correction for gravity4 ,,example4--,at the top of ,snowdon1 lat4 #ec ,n41 an aneroid read #bfdh1 correction -#jah1 the pressure at sea-level was #biia2 the temperature of the intermediate air was #eg2 find the height4 ,lower ,station #biia inches4 ,upper #bfcj ----- #cfa ,factor ,a #icc ----- #ajhc #ajhc #cbdi ----- #ccfh 7neglecting decimals47 ,factor ,b #a4jee ----- #afhdj ,n4,b4--,in taking out the quantities1 if accuracy #afhdj is aimed at1 it will be necessary to #ccfh proportion for parts in the usual manner ----- with such ,tables4 #ceec ,cor4 ,c #c #a -#c ,cor4 ,d #aj ---- ,height #cefj feet4 ,the illustration 7,fig4 #cc7 shows the instrument with the telescopic tube drawn out for use1 and the thermometer surrounded by the vapour of boiling water4 ,the lamp is protected from wind by a perforated japanned tin case covered with wire gauze4 ,when the boiler is charged and the lamp ignited the mercury ascends1 and the point at which it becomes stationary shows the temperature1 which will give the elevation in feet above the sea-level on reference to the table supplied by the optician from whom the instrument is purchased4 ,illustration3 #cd4 ,barograph4 ,scale about #a_/f4 ,a highly-refined automatic arrangement is adopted at some observatories called a ,barograph1 which1 by the aid of photography1 becomes a self-recording mercurial barometer4 ,it is simpler in its arrangement than the thermograph1 and includes a clock of superior construction1 causing a cylinder bearing photographic paper to make one complete revolution in forty-eight hours4 ,a double combination of achromatic lenses brings to a focus rays passing through a slit placed in front of the mercurial column1 behind which is a strong gaslight or paraffin lamp1 the rays of which are condensed upon the slit by a combination of two plano-convex lenses4 ,although a barometer is an instrument artificially constructed by man1 it should not be forgotten that when once made the column of mercury is placed in a passive or quiescent state in direct relation with the great forces of nature1 so that its indications become to some extent natural phenomena4 ,this is aptly illustrated by what is called the 8daily fluctuation0 of the barometer which occurs in all countries1 though the hours and extent vary with the latitude1 diminishing as the latitude increases1 according to a definite law4 ,the phenomena does not admit of a satisfactory explanation1 but is doubtless connected with the daily variations of temperature and of vapour in the air4 ,the mercury falls naturally 7so to speak7 from nine or ten to between three and four p4m42 it then rises till between nine and ten p4m4 ,it falls again about four a4m41 and rises again about ten a4m4 ,it is usually highest at nine a4m4 and nine p4m41 and lowest at three a4m4 and three p4m4 ,these natural elevations and depressions of the mercury should be allowed for in reading the barometer1 as any rise or fall in opposition to the natural rise and fall possesses for that reason increased importance4 ,for instance1 fine weather may be expected if the mercury rises between nine a4m4 and three p4m42 in like manner rain may be expected should a fall take place between three p4m4 and nine p4m4 ,it will be inferred from the preceding facts that there are certain hours better suited for 8taking a reading0 than others4 ,when one observation only is made daily1 noon is the best time1 two observations should be made at nine a4m4 and nine p4m41 and for three the best hours are nine a4m4 7maximum71 noon 7mean71 and three p4m4 7minimum74 ,the opinion generally entertained that a high barometer is an indication of fine weather1 and a low one a warning of bad weather1 is open to exception1 and an increased value would attach to the indications of the instrument in proportion as the following points are noted and allowed for3-- #a4 ,the actual height of the mercury4 #b4 ,whether it is rising or falling4 #c4 ,the rate of rise and fall4 #d4 ,whether the rise or fall has been long continued4 ,the state of the barometer foretells coming weather1 and when the present weather disagrees with the barometer a change will soon take place4 ,a fall of half a tenth1 or more1 in an hour is a sure warning of a storm1 a rapid rise is a warning of unsettled weather4 ,the barometer is generally lowest with wind from the ,s4,w41 and highest with wind ,n4,e41 or with a calm4 ,n4,e4 and ,s4,w4 may be called the wind's poles1 and the difference of height due to direction only from one of these bearings to another amounts to about half an inch4 ,,barometer ,,precautions4 ,if vacuum suspected1 cause mercury to strike top of tube4 ,a clear metallic 8click0 indicates a good vacuum4 ,a dull 8thud0 indicates air or moisture4 ,in latter case return to optician1 but if unable ,incline very gently until nearly inverted1 when ,air if present will ascend in a bubble into the cistern4 ,suspend barometer in good light out of sunshine4 ,let no heat of fire or lamp affect it4 ,let no sudden changes of temperature affect it4 ,it must hang absolutely vertically4 ,note temperature of attached thermometer before reading barometer4 ,then adjust mercury in cistern to touch ivory point4 ,then adjust vernier and take reading quickly4 ,ascertain height above sea-level according to direction4 ,the ,storm ,glass 7,fig4 #cf7 is a glass bottle1 ten inches long1 containing a mixture of camphor1 nitre1 sal-ammoniac1 alcohol1 and water4 ,as 8temperature affects the mixture much10 an arrangement has recently been designed in which the stem of a thermometer is immersed in the fluid1 as shown at ,fig4 #cg1 thus imparting a higher value to its indications4 ,the late ,admiral ,fitzroy says-- 8,since #ahbe1 we have generally had some of these glasses1 as curiosities rather than otherwise2 for nothing certain could be made of their variations until lately1 when it was fairly demonstrated that if fixed undisturbed in free air1 not exposed to radiation1 fire1 or sun1 but in the ordinary light of a well-ventilated room1 or1 preferably1 in the outer air1 the chemical mixture in a so-called storm glass varies in character with the direction of the wind--not its force40 ,the quarter from which the wind or storm is blowing is indicated by the substance adhering more closely to the bottom of the glass opposite to the point whence the wind or tempest arises4 ,the ,sympiesometer is an instrument used chiefly at sea for purposes of comparison with the mercurial and aneroid barometers4 ,its indications result partly from the pressure and partly from the temperature of the atmosphere2 it would1 therefore1 be more correctly named a ,thermo-,barometer4 ,illustration3 #ce4 #cf4 #cg4 ,storm ,glass1 or ,chemical ,weather ,glass4 ,scale about #a_/e4 ,the height of the atmosphere has been variously estimated3--,by ,bravais1 from the duration of twilight1 at #ff to nearly #ajj miles2 by ,dalton1 in #ahai1 from observations of the auroral light1 at #ajb miles2 by ,sir ,john ,herschel1 from similar observations in #ahfa1 at #hc miles2 from observations of meteors1 from #ajj to #bjj miles2 by ,liais1 in #ahei1 from observations on the polarisation of the sky1 at no less than #bab miles4 ,the density of the atmosphere diminishes with distance from the earth's surface1 in accordance with the following rule3--8,at a height of seven miles the density of the atmosphere is reduced to one-fourth the density at the sea-level1 and for every additional seven miles1 the rarity of the air is similarly quadrupled40 ,,note ,,on ,,the ,,verification ,,of ,,instruments ,,at ,,the ,,kew ,,observatory4 ,the ,kew ,committee of the ,royal ,society receive1 for verification and comparison with the standard instruments of the ,kew ,observatory1 barometers1 thermometers1 and other instruments intended for meteorological observation or scientific investigations4 ,any persons ordering instruments of opticians may direct them to be previously forwarded to the observatory for verification4 ,a scale of charges is issued by the ,committee which is exclusive of packing and carriage1 or of rail expenses1 when a special messenger is sent out4 ,the ,meteorological ,office1 ,victoria ,street1 ,london1 also receives and forwards instruments for verification to the ,kew ,observatory4 ,the ,committee wish it to be understood that they cannot undertake the verification of an inferior class of instruments 7such as barometers mounted upon wooden frames1 and thermometers not graduated on the stem71 and that the superintendent of the observatory may at his discretion decline to receive such instruments as he may consider unfit for scientific observation4 ,,barometer ,,warnings4 ,may be ,expected ----- ,increasing storm ,if mercury falls during a high wind from ,s4,w41 ,s4,s4,w41 ,w4 or ,s4 ,violent but short ,if the fall be rapid4 ,less violent but of longer ,if the fall be slow4 continuance ,a violent storm from the ,if the mercury falls suddenly while the ,n4,w4 or ,n4 wind is due ,w4 ,n4,w41 ,n41 or ,n4,e4 winds1 or ,if the mercury having been at its usual less wind1 or less rain1 or height1 #biie1 is steady or rising1 less snow while the thermometer falls and the air becomes drier4 ,wind and rain from ,s4,e41 ,s41 ,if the mercury falls1 while the and ,s4,w4 thermometer rises and the air becomes damp4 ,a violent storm from ,n4,w41 ,when the mercury falls suddenly with a ,n41 or ,n4,e4 ,w4 wind4 ,snow ,if the mercury falls when the thermometer is low4 ,less wind1 or a change to ,when the mercury rises1 after having ,n41 or less wet been some time below its average height4 ,strong wind or heavy squalls ,with the first rise of the mercury from ,n4,w41 ,n41 or ,n4,e4 after it has been very low 7say #bi74 ,improved weather ,when a gradual continuous rise of the mercury occurs with a falling thermometer4 ,winds from ,s4 or ,s4,w4 ,if the mercury suddenly rising1 the thermometer also rises4 ,heavy gales from ,n4 ,soon after the first rise of the mercury from a very low point4 ,unsettled weather ,with a rapid rise of the mercury4 ,settled weather ,with a slow rise of the mercury4 ,very fine weather ,with a continued steadiness of the mercury with dry air4 ,stormy weather with rain 7or ,with a rapid and considerable fall of snow7 the mercury4 ,threatening1 unsettled ,with an alternate rising and falling of weather the mercury4 ,much wind1 rain1 hail1 or ,when the mercury falls considerably4 ,if snow1 with or without the thermometer be low 7for the season7 lightning the wind will be ,n41 if high1 from ,s4 ,lightning only ,when the mercury is low1 the storm being beyond the horizon4 ,fine weather ,with a rosy sky at sunset4 ,wind and rain ,when the sky has a sickly greenish hue4 ,rain ,when the clouds are of a dark ,indian red4 ,bad weather or much wind ,when the sky is red in the morning4 ,,explanatory ,,card4 ,,by ,,the ,,late ,,vice-,,admiral ,,fitzroy1 ,f4,r4,s41 ,,etc4 ,,weather ,,glasses4 ,,the ,,barometer ,,rises ,,the ,,barometer ,,falls for ,northerly wind for ,southerly wind 7including from ,north-west1 by 7including from ,south-east1 by the the ,north1 to the ,eastward71 ,south1 to the ,westward71 for dry1 or less wet weather1--for for wet weather1--for stronger less wind1--or for more than one wind1--or for more than one of of these changes3-- these changes3-- ,,except on a few occasions when ,,except on a few occasions when rain1 hail1 or snow comes from the moderate wind with rain 7or ,northward with strong wind4 snow7 comes from the ,northward4 -------------------------- ,for change of wind toward ,for change of wind toward ,northerly directions1-- ,southerly directions1-- ,a ,,thermometer ,,falls4 ,a ,,thermometer ,,rises4 ,moisture or dampness in the air 7shown by a ,hygrometer7 increases ,,before rain1 fog1 or dew4 -------------------------- ,on barometer scales the following ,add one-tenth of an inch to the contractions may be useful3-- observed height for each hundred feet the ,barometer is above the ,,rise ,,fall half-tide level4 ,,for ,,for ,the average height of the ,barometer1 in ,england1 at the ,,north ,,south sea-level1 is about #biid inches2 and the average temperature ,n4,w4--,n4--,e4 ,s4,e4--,s4--,w4 of air is nearly #ej degrees 7,london latitude74 ,,dry ,,wet ,the ,thermometer falls about ,,or ,,or one degree for each three hundred feet of elevation from the ground1 ,,less ,,more but varies with wind4 ------ ,,wind4 ,,wind4 8,when the wind shifts against the sun1 ------ ------ ,trust it not1 for back it will run40 ------ ,,except ,,except ,first rise after very low ,indicates a stronger blow4 ,,wet ,,from ,,wet ,,from ------ ,long foretold--long last1 ,,north4 ,,north4 ,short notice--soon past4 7,in ,south ,latitude read ,south for ,north47 ,,iv4--,,condensation4 ,dew is a deposition of moisture from the air1 resulting from the condensation of the aqueous vapour of the atmosphere on substances which have become cooled by the radiation of their heat4 ,this is1 in fact1 the substance of ,dr4 ,wells's famous ,theory of ,dew1 enunciated in #ahad1 and which1 according to ,dr4 ,tyndall1 8has stood the test of all subsequent criticism1 and is now universally accepted10 and by which all the phenomena of dew may be explained4 ,dr4 ,wells's experiments were interesting and conclusive4 ,he exposed definite weights 7#aj grains7 of wool to the air on clear nights1 one on a four-legged stool1 the other under it1 the upper portion gained #ad grains in weight1 the lower only #d grains4 ,on an evening when one portion of wool1 protected by a curved pasteboard roof1 gained only #b grains1 a similar portion on the top of the miniature roof gained #af grains4 ,a little reflection will suggest the explanation3 radiation from the wool was arrested by the pasteboard cover1 while the portion fully exposed to the sky lost all its heat1 and thus condensation ensued4 ,dr4 ,wells speaks with such candour1 and so pointedly1 on this fact and its consequences1 that his words may be advantageously quoted3 8,i had often1 in the pride of half-knowledge1 smiled at the means frequently employed by gardeners to protect tender plants from cold1 as it appeared to me impossible that a thin mat1 or any such flimsy substance1 could prevent them from attaining the temperature of the atmosphere1 by which alone ,i thought them liable to be injured4 ,but when ,i had learned that bodies on the surface of the earth become during a still and serene night colder than the atmosphere1 by radiating their heat to the heavens1 ,i perceived immediately a just reason for the practice ,i had before deemed useless40 ,familiar instances of the formation of dew will have been noted by many 8watchers20 e4 g41 breathing on a cold pane of glass1 a tumbler of cold water becoming dew-covered on being brought into a warm room1 the outside of a tankard of iced claret cup1 c4 ,when1 radiation is so free and rapid that the temperature is below the freezing point1 the dew freezes as it forms1 producing hoar-frost4 ,in our climate the air is never completely dry1 nor completely saturated with moisture1 and the amount of aqueous vapour held in suspension is very variable4 ,this fact has important bearings on many branches of industry1 as also on the hygienic qualities of the atmosphere4 ,the consideration that a certain amount of moisture in the air is necessary to the continuance of health will suggest the importance of maintaining that due proportion in the atmosphere of sick rooms1 where the artificial heat so injudiciously used1 often disturbs the healthful hygrometric condition of the air4 ,mr4 ,,glaisher is of opinion that the medical profession should enforce1 as far as lies in their power1 the use of this simple and effective instrument1 which gives indications so important to the comfort of the patient4 ,the amount of moisture in the air is estimated by the use of instruments called ,hygrometers1 which may be thus classified3-- #a4 ,hygrometers of ,absorption4--,made with hair1 oatbeard1 catgut1 seaweed1 grass1 chloride of calcium4 #b4 ,hygrometers of ,condensation4--,regnault's1 ,daniell's1 ,leslie's1 ,dyne's4 #c4 ,hygrometers of ,evaporation4--,mason's ,psychrometer1 or ,wet and ,dry ,bulb ,thermometers4 ,by an ingenious application of the affinity of the oatbeard for moisture1 ,damp ,detectors are constructed for tourists1 commercial travellers1 c41 to test moisture and avoid the consequences of sleeping in damp beds4 ,they are strongly gilt1 and resemble in size and shape a lady's watch4 ,illustration3 #ch4 ,damp ,detector4 ,scale about #b_/c4 ,in ,saussaure's ,hygrometer the frame is of brass1 and the scale of the same metal silvered4 ,it has an attached thermometer1 and the indications are the result of the contraction and expansion of a prepared human hair1 consequent upon its absorbing or yielding moisture4 ,the scale is divided on the arc of a circle1 and an index needle1 working on an enlarged arc1 multiples the indications4 ,regnault's ,hygrometer 7,fig4 #ci7 consists of a thin and highly polished silver tube or bottle1 into the neck of which is inserted a delicate thermometer4 ,the bottle has a lateral tubular opening1 to which is attached a flexible tube with an ivory mouthpiece4 ,ether is poured into the silver tube in sufficient quantity to cover the bulb of the thermometer4 ,the ether is then agitated by breathing through the flexible tube until1 by the rapid evaporation thus produced1 a condensation of moisture takes place1 readily observable on the bright polished silver surface1 and the temperature indicated by the thermometer at that moment is the dew-point4 ,illustration3 #ci4 ,regnault's ,hygrometer4 ,scale about #a_/aj4 ,daniell's ,hygrometer1 or ,dew-point ,thermometer 7,fig4 #dj71 consists of a glass tube1 bent twice at right angles1 each extremity terminating in a bulb about #a-a_/b inch in diameter1 supported on a brass stand1 to which a thermometer is attached to indicate the temperature of the surrounding air4 ,the lower bulb is of blackened glass1 to facilitate the observation of the dew-point2 it is about three parts filled with pure ether1 and contains a very delicate thermometer4 ,the upper bulb at the extremity of the short stem is transparent1 but covered with thin muslin1 upon which1 when an observation is made1 pure ether is slowly dropped4 ,the evaporation rapidly lowers the temperature1 until a moment arrives at which dew condenses on the black bulb4 ,a quick eye is necessary to note this and the temperature shown by the thermometer simultaneously1 the latter showing the degree at which the atmosphere is saturated with moisture at the time of observation4 ,to avoid error1 it is usual to note the temperature at which the dew disappears1 and take the mean of the two temperatures4 ,illustration3 #dj4 ,daniell's ,hygrometer4 ,scale about #a_/e4 ,dyne's ,hygrometer1 for showing the dew-point by direct observation1 by means of iced water and black glass1 enables the observer to dispense with the use of ether1 and shows the dew-point with great distinctness4 ,illustration3 #da4 ,mason's ,hygrometer4 ,scale about #a_/f4 ,the hygrometer in most general use is the wet and dry bulb thermometer1 and for which ,mr4 ,glaisher has calculated an elaborate set of tables1 a brief abstract of which sufficient for general purposes is subjoined4 ,for finding the ,degree of ,humidity of the ,air from ,observations of a ,dry ,bulb and a ,wet ,bulb ,thermometer1 sometimes called ,mason's ,psychrometer4 ---------------------------------------- -------------- ,,difference ,,between ,,dry ,,bulb ,,and ,,wet ,,bulb ,,readings4 ,,temperature ------------------------------------ ,,by ,,the ,,dry ,,bulb #b #d #f #h #aj #ab ,,thermometer4 ------------------------------------ ,,degree ,,of ,,humidity4 ---------------------------------------- --------- #cd #gi #fc #ej 444 444 444 #cf #hb #ff #ec 444 444 444 #ch #hc #fh #ef #de 444 444 #dj #hd #gj #eh #dg 444 444 #db #hd #ga #ei #di 444 444 #dd #he #gb #fj #ej 444 444 #df #hf #gc #fa #ea 444 444 #dh #hf #gc #fb #eb #dd 444 #ej #hf #gd #fc #ec #de 444 #eb #hf #gd #fd #ed #df 444 #ed #hf #gd #fd #ee #dg 444 #ef #hg #ge #fe #ef #dh 444 #eh #hg #gf #ff #eg #di 444 #fj #hh #gf #ff #eh #ej #dc #fb #hh #gg #fg #eh #ej #dd #fd #hh #gg #fg #ei #ea #de #ff #hh #gh #fh #fj #eb #de #fh #hh #gh #fh #fj #eb #df #gj #hh #gh #fi #fa #ec #dg #gb #hi #gi #fi #fa #ed #dh #gd #hi #gi #gj #fb #ee #dh #gf #hi #gi #ga #fc #ee #di #gh #hi #gi #ga #fc #ef #ej #hj #ij #hj #ga #fc #ef #ej #hb #ij #hj #gb #fd #eg #ea #hd #ij #hj #gb #fd #eg #ea #hf #ij #hj #gb #fd #eh #eb ---------------------------------------- --------- ,the total quantity of aqueous vapour which at any temperature can be diffused in the air being represented by #ajj1 the percentage of vapour actually present will be found in the table opposite the temperature of the dry thermometer1 and under the difference between the dry bulb and wet bulb temperatures4 ,the degree of humidity for intermediate temperatures and differences to those given in the table can be easily estimated4 ,thus dry bulb #ea1 wet bulb #df1 give #fi for the degree of humidity4 ,the instrument1 as shown at page #dh1 consists of two thermometers attached to a support1 which may be either slate or wood4 ,the bulb of one of the thermometers has some thin muslin tied over it1 and is kept moist by the capillary action of a thread dipping into a cistern of water placed underneath4 ,it will be obvious that the amount of evaporation will be in proportion to the dryness of the air1 and that the differences of temperature indicated by the two thermometers will be greatest when the atmosphere is dry1 and least when the air is damp4 ,illustration3 #db4 ,board of ,trade ,thermometer ,screen4 ,scale about #a_/i4 ,,hygrometer ,,precautions4 ,hygrometers should be exposed in the shade free from air-currents4 ,the covering of the wet bulb must be very thin4 ,the supply of water must be carefully regulated4 ,the bulb must be constantly moist1 yet not too wet4 ,the supply of water must be ample in dry weather4 ,in damp weather water must not drip from the wet bulb4 ,water reservoir should be as far as possible from the dry bulb4 ,dry bulb must never receive moisture from any source4 ,use distilled1 rain1 or softest water procurable1 for wet bulb4 ,when lime deposits from use of hard water change muslin and worsted4 ,replenish reservoir after1 or long before1 taking an observation4 ,well wash muslin and worsted before using4 ,also wash occasionally while in use4 ,change muslin twice a month or according to condition4 ,dust and blacks must not be allowed to accumulate on muslin4 ,when wet bulb is frozen1 wet with ice-cold water by brush4 ,the water will first freeze1 then cool to air-temperature4 ,after which wet bulb falls a trifle lower than dry one4 ,then temperature of evaporation may be noted4 ,in thick fog wet bulb reads above dry bulb4 ,in cold calm weather1 wet bulb reads above dry bulb4 ,this is owing to the air being perfectly saturated4 ,covered bulb cannot therefore show temperature as well as uncovered4 ,in such cases both readings are assumed to be identical4 ,it is important that the instrument should be protected not only from the sun's direct rays1 from rain and snow1 but also from wind1 the currents of which would1 by increasing evaporation1 cause the wet bulb thermometer to indicate a temperature not strictly due to the hygrometric condition of the atmosphere4 ,for this purpose ,thermometer ,screens are employed4 ,illustrations of two forms are shown at ,figs4 #db and #dc2 they should be placed facing the north at a distance of four feet from the ground4 ,fig4 #db shows the form adopted by the ,board of ,trade1 for marine service1 while ,fig4 #dc shows ,mr4 ,stevenson's double-louvred screen with perforated bottom1 which ensures free ingress and egress of air1 the exclusion of snow and rain1 and the direct rays of the sun4 ,professor ,wild recommends overlapping segments of sheet zinc for the construction of these screens1 as possessing the advantage over wood of becoming sooner in thermic equilibrium with the surrounding air1 and thus preventing radiation4 ,stevenson's ,screen should be erected on legs four feet high1 and should stand over grass on open ground4 ,it should not be under the shadow of trees1 nor within twenty feet of any wall4 ,illustration3 #dc4 ,stevenson's ,thermometer ,screen4 ,scale about #a_/aj4 ,,clouds4 ,the important office performed by clouds in the economy of nature entitles them to extended consideration4 ,a cloud may be defined as 8water-dust10 since aqueous vapour diffused through the air is invisible until the temperature is sufficiently lowered to produce condensation2 no satisfactory explanation1 however1 has yet been given of the mode of suspension of this water-dust1 nor why it remains suspended in opposition to gravitation4 ,it is tolerably certain that electricity is not without its influence1 though the apparently stationary character of some clouds is deceptive1 for while there may be no apparent motion in the mass the particles constituting the mass are undergoing continuous renewal1 which justifies the assertion of ,espy that every cloud is either a forming or dissolving cloud4 ,aeronauts in ascending from the earth pass through many successive alternations of cloud-strata and clear air which owe their existence to the varying temperature and degrees of humidity of the atmospheric currents so superposed4 ,luke ,howard in his ,askesian ,lectures1 #ahjb1 divides clouds into three primary modifications3 cumulus1 stratus1 and cirrus1 with intermediate forms resulting from combinations of the primaries1 viz41 cirro-cumulus1 cirro-stratus1 cumulo-stratus1 and cumulo-cirro-stratus or nimbus4 ,this nomenclature is now universally adopted4 ,illustration3 #dd4 ,cirrus4 ,,cirrus1 or mare's tail cloud1 appears as parallel1 flexuous1 or diverging streaks or fibres1 partly straight4 ,it is the lightest and the highest of all clouds1 being seldom less than three miles1 and often ten miles1 above the earth1 and shows the greatest variety of form4 ,on account of its great height it is assumed to consist of minute snowflakes or crystals of ice1 the refractions and reflections from which produce the halos1 coron1 and mock suns and moons which occur chiefly in this cloud and its derivatives4 ,it retains its varied outlines longer than any other cloud2 at sunrise it is the first to welcome the sun's rays1 and at sunset the last to part with them4 ,it is the most useful of all clouds for weather warnings4 #a4 ,serene1 settled weather may be expected when groups and threads of cirri are seen during a gentle wind after severe weather4 #b4 ,a change to wet may be expected when1 after continued fair weather1 filaments1 or bands of cirri 7apparently stationary71 with converging ends1 travel across the sky4 #c4 ,rain or snow1 and windy1 variable weather may be expected when cirri with fine tails vary much in a few hours4 #d4 ,continued wet weather may be undoubtedly expected when horizontal sheets of cirri fall quickly and pass into the cirro-stratus4 #e4 ,a storm of wind and rain may be expected within forty-eight hours when fine threads of cirri seem brushed backward from the south-west4 ,illustration3 #de4 ,cumulus4 ,,cumulus4--,this modification of cloud is most frequently seen on bright summer days1 and is appropriately called 8the day cloud0 and 8the summer cloud40 ,it is formed only in the daytime1 in summer calms1 and results from the rise of vapours from rivers1 lakes1 and marshes into the colder regions of the air1 the lower portions of which are readily saturable4 ,they are characterized by a horizontal base1 from which they rise in dense conical and hemispherical masses rivalling mountains in their magnitude4 ,their formation is due to the convection of heat from the earth's surface1 which renders the lower atmospheric strata capable of holding a larger amount of aqueous vapour and simultaneously establishes an upward current1 which reaching the colder regions of the air brings about the condensation of the aqueous vapour into the elegant and ever-beautiful forms admired alike 8by saint1 by savage1 and by sage40 ,these begin as mere specks1 which enlarge until the sky is nearly covered in the afternoon1 and towards sunset they generally disappear1 their tops becoming cirri when the air is dry4 #a4 ,fine1 calm1 warm weather may be expected when cumuli are of moderate size and of pleasing form and colour4 #b4 ,cold1 tempestuous1 rainy weather may be expected when cumuli cover the sky1 rolling over each other in dense1 dark1 and abrupt masses4 #c4 ,thunder may be expected when cumuli of hemispherical form are characterized by an extreme silvery whiteness4 #d4 ,rain may be expected when cumuli increase in number towards evening1 sinking at the same time into the lower portions of the air4 ,illustration3 #df4 ,stratus4 ,,stratus4--,as its name implies1 this is a horizontal sheet of cloud formed near the earth at night 7whence it has been called 8the night cloud07 by the condensation of moist air from rivers1 lakes1 and marshes1 or damp ground which has lost its day-heat by radiation1 especially in calm clear evenings1 after warm days4 ,it appears as a white mist near1 and sometimes touching1 the earth4 ,it attains its maximum density about midnight1 but is dissipated by the rays of the morning sun4 ,its formation1 watched from a height over a large city1 is highly interesting1 and is attributed by ,sir ,john ,herschel to the soot suspended over such localities1 each particle of which acts as 8an insulated radiant1 collects dew on itself1 and sinks down rapidly as a heavy body40 ,still more interesting is it to observe from a similar elevation the dissipation of this cloud when the sun has attained such an altitude that its rays fall on the upper surface of the stratus cloud1 which then heaves like the billows of the ocean1 while the whole mass seems to rise spontaneously from the earth1 and speedily vanishes 8into air1 into thin air40 #a4 ,the finest and most serene weather may be expected when stratus clouds present the appearances just described4 ,,cirro-,,cumulus1 or 8mackerel sky10 is a well-known form of cloud occurring in small roundish masses1 looking like flocks of sheep at rest1 and often at great heights4 ,it is seldom seen in winter4 #a4 ,increased heat may be expected when cirro-cumuli appear4 #b4 ,a storm or thunder may be expected when cirro-cumuli occur mingled with cumulo-stratus in very dense1 round1 and close masses4 #c4 ,warm wet weather1 and a thaw1 may be expected when cirro-cumuli occur in winter4 ,,cirro-,,stratus 8appears to result from the subsidence of the fibres of cirrus to a horizontal position1 at the same time approaching laterally4 ,the form and relative position when seen in the distance frequently give the idea of shoals of fish40 ,it is called 8the vane cloud0 and 8mackerel-backed sky40 #a4 ,rain1 snow1 and storm may be expected when cirro-stratus is seen alone or mingled with cirro-cumulus1 especially if the cirro-cumulus passes away4 #b4 ,fair weather may be expected when from a mixture of cirro-stratus and cirro-cumulus the former disappears1 leaving the latter in possession of the sky4 #c4 ,thunder and heat are generally attended by waved cirro-stratus4 ,,cumulo-,,stratus4--,this form of cloud results from the mingling of the cumulus and cirro-stratus2 it appears sometimes as a thick bank of cloud with overhanging masses4 ,the cloud known as 8distinct0 cumulo-stratus appears as a cumulus surrounded by small fleecy clouds4 #a4 ,thunder may be expected when 8distinct0 cumulo-stratus appear4 #b4 ,sudden atmospheric changes may be expected when cumulo-stratus appear4 ,illustration3 #dg4 ,nimbus4 ,,nimbus1 ,,or ,,cumulo-,,cirro-,,stratus4--,the name of this cloud at once suggests that it is produced by a combination of the three primary forms of cloud4 ,the nimbus is popularly known as 8the rain cloud40 ,it is really a system of clouds1 having its origin chiefly in the tendency of the cumulo-stratus to spread1 overcast the sky1 and settle down to a dense horizontal black or grey sheet1 above which spreads the cirrus1 and from below which rain begins to fall4 #a4 ,a cessation of rain may be expected when the grey lower portion of nimbus begins to break up4 #b4 ,a thunderstorm may be expected when the nimbus character of the cloud is very perfect4 #c4 ,very copious showers may be expected when the cirri projected from the top of the rain-cloud are very numerous4 ,,amount ,,of ,,clouds4--,any record of the proportion of sky covered by cloud should be made on a scale of #j to #aj4 ,a clear sky is registered #j1 and a sky wholly obscured as #aj1 any intermediate condition being represented by #e--g1 or other figures deemed appropriate by the observer4 ,the kind of cloud should be noted1 as also the direction in which it is driven by the wind1 whether in the upper or lower strata of the air4 ,this operation may be assisted by an ingenious arrangement1 exhibited by ,mr4 ,goddard in #ahfb1 and called a 8cloud reflector10 obtainable at any optician's4 ,observations at the ,greenwich ,observatory establish the facts that the least amount of cloud exists during the night1 especially in ,may and ,june1 and the greatest amount at midday1 and in winter2 also that from ,november to ,february three-fourths of the heavens are obscured by sun-repelling clouds4 ,,height ,,of ,,clouds4--,great diversity of opinion exists on this point4 ,it is asserted1 on the one hand1 that the region of clouds does not extend beyond five miles above sea-level1 but ,glaisher has attained a height of #cf1ifj feet1 and from thence saw clouds floating at a great height above him2 and it is considered probable that cirri are often ten miles above the earth4 ,,velocity ,,of ,,clouds4--,this is of two kinds3 #ast4 ,velocity of ,propagation2 and #bnd4 ,velocity of ,motion4 ,the first occurs when at a given altitude the dew-point is suddenly attained1 when the sky on one occasion was covered from the eastern to the western horizon at the rate of #cjj miles per hour4 ,the second is dependent on the force of atmospheric currents1 which is much greater in the upper regions of the air than in those nearer the earth4 ,accurate observations of the shadows of clouds1 borne across the fields on a summer's day1 warrant the assertion that an apparently slow motion of clouds is equal to eighty miles an hour1 while a velocity of #abj miles is attained without impressing the observer with the idea of rapidity4 ,on the subject of clouds ,admiral ,fitzroy says3-- ,may be ,expected ----- ,fine weather ,when clouds are 8soft-looking or delicate40 ,wind ,when clouds are hard-edged or oily-looking4 ,less wind ,in proportion as the clouds look softer4 ,more wind ,the harder1 more 8greasy10 rolled1 tufted1 or ragged the clouds look4 ,rain ,when small-inky-looking clouds appear4 ,wind and rain ,when light scud clouds are seen driving across heavy masses4 ,wind only ,when light scud clouds are seen alone4 ,change of wind ,when high upper clouds cross the sun1 moon1 or stars in a direction different from that of the lower clouds1 or the wind then felt below4 ,wind ,with tawny or copper-coloured clouds4 ,the following 8,weather ,warnings0 may be gathered from the ,,colour ,,of ,,the ,,sky3-- ,whether clear or cloudy1 a rosy sky at sunset presages fine weather2 a sickly greenish hue1 wind and rain2 a red sky in the morning1 bad weather1 or much wind or rain2 a grey sky in the morning1 fine weather2 a high dawn 7i4 e41 when the first indications of daylight are seen above a bank of clouds71 wind2 a low dawn 7i4 e41 when the day breaks on or near the horizon71 fair weather4 ,light1 delicate1 quiet tints or colours1 with soft1 indefinite forms of clouds1 indicate and accompany fine weather2 but gaudy or unusual hues1 with hard1 definitely outlined clouds1 foretell rain and probably strong wind4 ,also a bright yellow sky at sunset presages wind2 a pale yellow1 wet2 orange or copper-coloured1 wind and rain3 and thus1 by the prevalence of red1 yellow1 green1 grey1 or other tints1 the coming weather may be told very nearly2 indeed1 if aided by instruments1 almost exactly4 ,after fine1 clear weather the first signs in a sky of a coming change are usually light streaks1 curls1 wisps1 or mottled patches of white distant cloud1 which increase and are followed by an overcasting of murky vapour that grows into cloudiness4 ,this appearance1 more or less oily or watery as wind or rain will prevail1 is an infallible sign4 ,usually1 the higher and more distant such clouds seem to be1 the more gradual1 but general1 the coming change of weather will prove4 ,misty clouds1 forming or hanging on heights1 show wind and rain coming1 if they remain1 increase1 or descend2 if they rise or disperse1 the weather will improve or become fine4 ,may be ,expected ----- ,fine weather ,when the sky is grey in the morning4 ,wind ,with a high dawn4 ,fair weather ,with a low dawn4 ,wind ,when the sky at sunset is of a bright yellow4 ,rain ,when the sky at sunset is of a pale yellow4 ,wind and rain ,when the sky is orange or copper colour4 ,fine weather ,when the sky has light1 delicate1 quiet tints and soft1 indefinite forms of clouds4 ,rain and wind ,when the sky has gaudy1 unusual hues1 with hard1 definite outlined clouds4 ,fair weather ,when sea-birds fly out early and far to seaward4 ,stormy weather ,when sea-birds hang about the land1 or fly inland4 ,fair weather ,when dew is deposited4 ,its formation never begins under an overcast sky1 or when there is much wind4 ,rain ,on what is called a good hearing day4 ,rain ,when remarkable clearness of atmosphere1 especially near the horizon1 exists1 distant objects1 objects1 such as hills1 being unusually visible or well defined4 ,,rain4 ,the atmosphere at a given temperature is capable of retaining only a given quantity of aqueous vapour1 invisibly diffused through it1 at which temperature it is said to be saturated4 ,should the temperature from any cause be lowered1 the aqueous vapour at once becomes visible in the form of either cloud1 dew1 rain1 snow1 or hail4 ,it has already been shown that1 although marshes and rivers1 inland seas and lakes1 yield by evaporation watery vapours to the air1 the ocean is the great source of rain1 whence it is lifted in vast quantities by the sun's radiant heat1 to be subsequently condensed by passing into cooler regions1 or by contact with cold mountain peaks1 falling to earth as a fertilizing shower or a devastating flood4 ,sir ,john ,herschel accounts for the formation of raindrops by saying3--8,in whatever part of a cloud the original ascensional movement of the vapour ceases1 the elementary globules of which it consists being abandoned to the action of gravity1 begin to fall4 ,the larger globules fall fastest1 and if 7as must happen7 they overtake the slower ones1 they incorporate1 and the diameter being thereby increased1 the descent grows more rapid1 and the encounters more frequent1 till at length the globule emerges from the lower surface of the cloud at the #8vapour plane' as a drop of rain1 the size of the drops depending on the thickness of the cloud stratum and its density40 ,rain is very unequally distributed1 there being portions of the torrid zone where it never falls1 one locality in ,norway where it falls three days out of four1 and another on the western side of ,patagonia1 at the base of the ,andes1 where it falls every day4 ,the quantities recorded as having fallen at one time in some localities are simply appalling4 ,a fall of one inch is considered a very heavy rain in ,great ,britain1 and this fact will enable the reader partially to realize the following stupendous recorded falls3--,loch ,awe1 ,scotland1 #g inches in #cj hours2 ,joyeuse1 ,france1 #ca inches in #bb hours2 ,gibraltar1 #cc inches in #bf hours2 hills above ,bombay1 #bd inches in one night2 and on the ,khasia ,hills1 where the annual rainfall is #fjj inches1 #cj inches have been known to fall on each of five successive days4 ,mr4 ,g4 ,j4 ,symons1 the able editor of the 8,meteorological ,magazine10 and indefatigable superintendent of #b1jjj ,rain ,gauges throughout the ,united ,kingdom1 has compiled a table1 showing the equivalents of rain in inches1 its weight per acre1 and bulk in gallons1 the following portion of which1 while very useful to the farmer1 will enable the curious reader to make some interesting calculations1 based on the figures quoted above3-- ,,table ,,showing ,,equivalent ,,of ,,inches ,,of ,,rain ,,in ,,gallons1 ,,and ,,weight ,,per ,,acre4 ,inches of ,rain ,tons per ,acre ,gallons per ,acre #ja #aj #bbfb #jb #bj #debe #jc #cj #fghg #jd #dj #ijdi #je #ej #aacab #jf #fa #acegd #jg #ga #aehcf #jh #ha #ahjih #ji #ia #bjcfa #a;in4 #aja #bbfbc ,the instruments called ,rain ,gauges or ,pluviometers are1 as their name implies1 constructed to measure the amount of rain falling in any given locality1 and those in most general use have this principle in common3 that the graduated glass always bears a definite relation to the area of the receiving surface4 ,a very extraordinary and hitherto unexplained fact in connection with the fall of rain1 and which justifies the opinion that its formation is not limited to the region of visible cloud1 is that a series of rain gauges placed at different elevations above the soil are found to collect very different quantities of rain1 the amount being greater at the lower level4 ,thus1 twelve months' observations by ,dr4 ,heberden determined that the amount of rain on the top of ,westminster ,abbey was only twelve inches1 that on a house close by but much lower eighteen inches1 and on the ground during the same interval of time twenty-two inches4 ,accordingly1 ten inches is the height at which meteorologists have agreed the edge of the rain gauge should be placed from the ground4 ,the spot chosen should be perfectly level1 and at least as far distant from any building or tree as the building or tree is high1 and1 if the gauge cannot be equally exposed to all points1 a south-west aspect is preferable4 ,it is also important that the rain gauge should be well supported1 in order to avoid its being blown over by the wind2 and1 should frost follow a fall of rain1 the instrument should be conveyed to a warm room to thaw before measuring the collected contents4 ,the graduated glass furnished with each instrument should stand quite level when measuring the rain1 and the reading be taken midway between the two apparent surfaces of the water4 ,the best form of rain gauge is that in use in the ,meteorological ,office4 ,illustration3 #dh4 ,howard's ,rain ,gauge4 ,scale about #a_/e4 ,howard's ,rain ,gauge consists of a vertical glass receiver1 or bottle1 through the neck of which the long terminal tube of a circular funnel1 five inches in diameter1 is inserted4 ,a metal collar or tube fits over the outside of the neck of the receiver1 and aids in keeping the funnel level1 while the tube extends to within half an inch of the bottom1 thus ensuring the retention of every drop of rain which falls within the area of the funnel4 ,the glass vessel furnished with the instrument is graduated to #ajjths of an inch4 ,a modification of this instrument is made with a glass tube at the side graduated to inches1 #ajths1 and #ajjths1 showing the amount of rainfall by direct observation1 thus dispensing with the use of a supplementary graduated measure4 ,in ,glashier's ,rain ,gauge special provision is made1 in two ways1 to prevent possible loss by evaporation1 even in the warmest months of the year4 #a4 ,the receiving vessel is partly sunk beneath the soil1 thus keeping the contents cool4 #b4 ,the receiving surface of the funnel1 accurately turned to a diameter of eight inches1 terminates at its lower extremity in a curved tube1 which1 by always retaining the last few drops of rain1 prevents evaporation4 ,the graduated vessel1 in this instance also1 is divided to #ajjths of an inch1 having due regard to the larger area1 #h in4 of the funnel4 ,for use in tropical climates1 where1 as has been shown1 the rainfall is excessive1 a modification of this instrument is supplied by the instrument makers1 having an extra large receiver and tap for drawing off the collected rain4 ,luke ,howard1 in his 8,climate of ,london10 says3 8,it must be a subject of great satisfaction and confidence to the husbandman to know at the beginning of a summer1 by the certain evidence of meteorological results on record1 that the season1 in the ordinary course of things1 may be expected to be a dry and warm one1 or to find1 in a certain period of it1 that the average quantity of rain to be expected for the month has fallen4 ,on the other hand1 when there is reason1 from the same source of information1 to expect much rain1 the man who has courage to begin his operations under an unfavourable sky1 but with good ground to conclude1 from the state of his instruments and his collateral knowledge1 that a fair interval is approaching1 may often be profiting by his observations1 while his cautious neighbour1 who #8waited for the weather to settle1' may find that he has let the opportunity go by40 ,this superiority1 however1 is attainable by a very moderate share of application to the subject1 and by the keeping of a plain diary of the barometer and rain gauge1 with the hygrometer and vane under his daily notice4 ,illustration3 #di4 ,symons's ,rain ,gauge4 ,scale about #a_/g4 ,symons's ,rain ,gauge resembles ,howard's1 but has the advantage of having the glass receiver enclosed in a black or white japanned metal or copper jacket with openings permitting an approximate observation of the collected rain4 ,the metal jacket is also furnished with strong iron spikes1 which are firmly pressed into the soil1 as shown at ,fig4 #di1 thus ensuring perfect steadiness by its power to resist the wind4 ,the graduated measure contains half an inch of rain 7for a #e inch circle7 divided into #ajjths4 ,illustration3 #ej4 ,symons's ,storm ,rain ,gauge4 ,scale about #a_/ab4 ,mr4 ,symons has devised another rain gauge of so ingenious and interesting a character that it needs only to become generally known among amateur meteorologists to be in universal demand4 ,by its means an observer at a distant window may read off the rain as it falls4 ,it is shown at ,fig4 #ej1 where the usual #e-;inch funnel surmounts a long glass tube attached to a black board bearing a very open scale marking tenths of an inch in white lines2 a white float inside the tube constitutes the index1 which rises as the rain increases in quantity4 ,if1 as sometimes happens during a thunderstorm1 the rainfall is excessive1 a second tube on the left permits the measurement of a second inch of rain4 ,it will be obvious that if the time at which the rain begins to fall be noted the rate at which it falls1 as well as the quantity1 is indicated at sight by this instrument4 ,illustration3 #ea4 ,beckley's ,pluviograph4 ,scale about #a_/g4 ,crossley's ,registering ,rain ,gauge has a receiving surface of #ajj square inches4 ,the rain falling within this area passes through a tube to a vibrating bucket1 which sets in motion a train of wheels1 and these move the indices on three dials1 recording the amount of rain in inches1 #ajths1 and #ajjths4 ,printed directions are furnished with each instrument1 and the simplicity of the mechanism ensures due accuracy4 ,a test measure1 holding exactly five cubic inches of water1 sent with each gauge1 affords the means of checking its readings from time to time4 ,beckley's ,pluviograph possesses the exceptional merit of recording with equal precision all rainfalls1 from a slight summer shower to a heavy storm of rain4 ,it may be placed in a hole in the ground1 with the receiving surface raised the standard height of ten inches above its level4 ,fig4 #ea illustrates the construction of the instrument4 ,illustration3 #eb4 #ec4 ,stutter's ,self-recording ,rain ,gauge4 ,scale about #a_/g4 ,the funnel has a receiving surface of #ajj square inches1 protected by a lip #a-a_/d inch deep1 to retain the splashes4 ,the rain flows into a copper receiving vessel on the right1 which1 floating in a cistern of mercury1 sinks and draws down with it a pencil1 which records the event on a white porcelain cylinder moved by a clock4 ,when the receiving vessel is full the syphon comes into action1 rapidly drawing off the whole of the water1 the vessel rising almost at a bound1 the action being recorded by a vertical line on the porcelain cylinder4 ,two or more cylinders are supplied with each instrument2 and1 as the pencil marks are readily removed by a little soap and water1 a clean one may be always kept at hand for exchange once in every twenty-four hours4 ,the ,rev4 ,e4 ,stutter's ,self-recording ,rain ,gauge is ingenious1 and for a self-recording instrument is very moderate in price1 while it efficiently shows the rainfall for every hour in the twenty-four 7,figs4 #eb1 #ec74 ,an eight-day clock with its upright spindle revolves a small funnel with a sloping tube1 the end of which passes successively over the mouth of the twelve or twenty-four compartments in the rim of the instrument2 beneath each compartment is placed a tube1 as shown in the sectional figure4 ,all rain received by the outer funnel drips into the smaller revolving funnel1 and flows down the sloping tube1 the end of which is timed to take an hour in passing over each compartment1 so that the rain1 for example1 which falls between twelve and one o'clock will be found in the tube marked #a4 ,each tube can contain half an inch of rain1 and any overflow falls into a vessel beneath1 and can be measured2 the tube which has overflown shows the hour4 ,v4--,,motion4 ,wind is air in motion4 ,the motion of the air is caused by inequality of temperature4 ,the earth becomes warmed by the sun1 and radiates the heat thus acquired back upon the air1 which1 expanding and becoming lighter1 ascends to higher regions1 while colder and denser currents rush in to occupy the vacated space4 ,two points are to be noted in connection with this rush of air which we call wind1 viz41 its direction and velocity or force4 ,both are estimated scientifically by instruments called ,anemometers1#ac while mariners and the dwellers on our coasts have a nomenclature of their own by which to indicate variation in the force of the wind1 founded on the amount of sail a vessel can carry with safety at the time4 ,in the matter of direction winds are classed as constant1 periodical1 and variable4 ,footnote #ac3 ,anemos1 the wind2 metron1 measure4 ,,constant ,,winds4--,the ,trade ,winds4--,the violent contrast between the temperature of the equator and the poles is well known1 and from the vast area included within the tropics ascending currents of rarefied air are incessantly rising and being as incessantly replaced by a rush of cold air from the poles to the equator4 ,were the earth stationary1 this interchange would be of the simplest kind2 on arriving within the influence of the ascending equatorial current the air from the poles would be carried to the higher regions and turning over would proceed to the poles1 and1 becoming cold and dense in traversing the higher stratum1 would descend and resume its course ad infinitum4 ,the revolution of the earth on its axis changes all this3 the first effect is that the air at the equator is borne along with the earth at the rate of seventeen miles a minute from west to east1 a rate which diminishes at #fj of latitude to one-half that velocity1 until at the poles it is nothing2 consequently a slow north wind flowing to the equator is continually passing over places possessing a higher velocity than itself1 and not immediately acquiring that velocity1 there is according to the law of the composition of forces a compromise effected resulting in a north-east wind4 ,in a similar manner the same process in the southern hemisphere results in a south-east wind4 ,these winds have acquired the name of ,trade ,winds on account of the facilities afforded to navigation by their constancy4 ,the ,north ,trades occur in the ,atlantic between #i and #cj and in the ,pacific between #i and #bf4 ,the ,south ,trades occur in the ,atlantic between lat4 #d ,n4 and #bb ,s4 and in the ,pacific between latitude #d ,n4 and #bc-a_/b ,s4 ,these limits extend northward with the sun from ,january to ,june1 and southward from ,july to ,december4 ,parallel to the equator and extending between #b and #c on each side is a broad belt1 where the north and south trades neutralize each other1 producing what is called the 8,region or ,belt of ,calms40 ,though wind is absent1 thunderstorms and heavy rains are of daily occurrence4 ,when ,humboldt ascended ,teneriffe the trade wind was blowing at its base in the usual direction1 but on arriving at the summit he found a strong wind blowing in the opposite direction4 ,observation has shown that this upper current prevails north and south of the equator1 and that1 after passing the limit of the trade winds1 it descends to form the south-west winds of the north temperate zone and the north-west winds of the south temperate zone2 the westing being due to the same cause as the easting in the regular trades1 viz41 the rotation of the earth on its axis4 ,these winds are called the ,return ,trades1 but are not equal in constancy to the regular trade winds4 ,,periodical ,,winds4--,land and ,sea ,breezes occur on the coasts1 chiefly in tropical countries1 but sometimes in ,great ,britain during the summer months when the land during the day becomes very hot1 causing an ascending column of air1 which is replaced by a comparatively colder stream flowing inwards from the sea4 ,at sunset the conditions are reversed1 the earth becomes rapidly cooled by radiation1 the sea continuing comparatively warm1 the air over it ascends1 and its place is supplied by a cold breeze1 which 8blows off the shore10 as illustrated by the diagrams and the following experiment--,in the centre of a large tub of water float a water plate containing hot water1 imagine the former to be the ocean and the latter the heated land1 rarefying the air over it4 ,light a candle and blow it out and hold it while still smoking over the cold water1 when the smoke will be seen to move towards the plate4 ,the reverse of this takes place if the tub be filled with hot water and the water plate with cold4 ,when this phenomenon takes place on a large scale1 as in the case of the north trade winds being drawn from their course by the heated shores of ,southern ,asia1 the gigantic sea breeze thus produced is called the south-west monsoon4 ,this occurs from ,april to ,october1 when the sun is north of the equator4 ,when the sun is south of the equator--that is1 from ,october to ,april--the analogue of the land breeze is produced1 and is called the north-east monsoon4 ,,variable ,,winds4--,the character of this class of winds is determined by the physical configuration of the country in which they occur4 ,some tracts are marked by luxuriant vegetation1 others are bare4 ,here mountains lift their awful fronts and 8midway leave the storm10 there an arid plain extends itself to the seashore1 or inland1 towards a chain of lakes4 ,within the tropics these purely local conditions are insufficient to overcome the force of the prevalent atmospheric currents3 such1 however1 is not the case beyond the tropical zone4 ,there the variable winds prevail1 for which space permits only the mention of their names3--,the ,simoom 7from the ,arabic samma1 hot71 peculiar to the hot sandy deserts of ,africa and ,western ,asia4 ,the ,sirocco blows over the two ,sicilies as a hot wind from the south4 ,it extends sometimes to the shores of the ,black and ,caspian seas1 spreading death among animals and plants4 ,the ,solano prevails at certain seasons in the south of ,spain3 its direction is south-east4 ,the ,harmattan is another wind of the same class1 peculiar to ,senegambia and ,guinea4 ,the ,puna ,winds blow for four months over a barren tableland called the ,puna1 in ,peru4 ,they are a portion of the south-east trade winds1 which1 having crossed the ,pampas1 are thereby deprived of moisture1 and become the most parching wind in the world4 ,the ,east ,winds1 peculiar to the spring in ,britain1 blowing as they do through ,russia1 over ,europe1 are a portion of the great polar current1 distinctive of that season of the year4 ,they are dry and parching1 every one being familiar with the unpleasant bodily sensations attendant on this much-abused and yet most beneficent wind4 ,the ,etesian ,winds are drawn from the north across the ,mediterranean by the great heat of the ,african desert4 ,the ,mistral is a strong north-west wind peculiar to the south-east of ,france4 ,the ,pampero is a north-west wind1 blowing in summer from the ,pampas of ,buenos ,ayres4 ,as long ago as the year #afjj ,lord ,bacon remarked that the preponderating tendency of the wind was decidedly to veer with the sun's motion1 thus passing from ,n4 through ,n4,e41 ,e41 ,s4,e41 to south1 thence through ,s4,w41 ,w4,n4,w41 to ,n42 also1 that it often makes a complete circuit in that direction1 or more than one in succession 7occupying sometimes many days in so doing71 but that it rarely backs1 and very rarely or never makes a complete circuit in the contrary direction4 ,the merit of having first demonstrated that this tendency is a direct consequence of the earth's rotation is due to ,professor ,dove1 of ,berlin1 who has also shown that the three systems of atmospheric currents just treated of1 viz41 the constant1 periodical1 and variable winds1 are all amenable to the same influence4 ,as to the mode of observing the wind1 ,admiral ,fitzroy recommends that a true east and west line should be marked about the time of the equinox1 and the north1 south1 and other points of the compass being added1 to take the bearings of the wind in relation to a dial so prepared1 the indications of the lower stratum of clouds in conjunction with vanes and smoke being preferred to any other4 ,the direction of the wind should always be given according to true1 and not to compass bearings4 ,two points to the westward nearly represents the amount of 8,variation of the ,compass0 for the ,british ,isles1 which yields the following table for the conversion of directions observed by the compass in ,great ,britain and ,ireland to approximate true bearings4 ---------------------------------------- ---------------- ,compass bearings4 ,n ,,nne ,,ne ,,ene ,e ,,ese ,,se ,,sse ,true bearings4 ,,nnw ,n ,,nne ,,ne ,,ene ,e ,,ese ,,se ---------------------------------------- ---------------- ,compass bearings4 ,s ,,ssw ,,sw ,,wsw ,w ,,wnw ,,nw ,,nnw ,true bearings4 ,,sse ,s ,,ssw ,,sw ,,wsw ,w ,,wnw ,,nw ---------------------------------------- ---------------- 8,one may call a very simple diagram1 a circle divided by a diameter from north-east to south-west1 the thermometer compass4 ,while the wind is shifting from south-west1 by west1 north-west1 and north to north-east1 the thermometer is falling1 but while shifting from north-east1 by east1 south-east and south1 towards south and south-west1 the thermometer is rising4 ,now the barometric column does just the reverse4 ,from north-east the barometer falls as the wind shifts through the east to south-east1 south1 and south-west1 and from the south-west1 as the wind shifts round northward to north-east1 the barometer rises--it rises to west1 north-west1 north1 and north-east4 8,the effect of the wind thus shifting round when traced upon paper by a curve1 seems certainly wave-like to the eye2 but ,i believe it to be simply consequent on the wind shifting round the compass1 and indicating alteration in the barometric column4 8,if the wind remained north-east1 say three weeks1 there would be no wave at all--there would be almost a straight line along a diagram 7varying only a little for strength74 ,the atmospheric line1 in such a case1 remains at the same height1 and the barometer remains at #cj inches and 7say7 some three or four-tenths1 for weeks together4 ,so likewise when the wind is south-westerly a long time1 or near that point1 the atmospheric line remains low1 towards #bi inches4 ,thus1 such #8atmospheric waves' may be an optical delusion4 8,the diagram alluded to above shows how the barometer and thermometer may be used in connection with each other in foretelling wind1 and consequently weather1 that is coming on1 because as the one rises1 the other generally falls1 and if you take the two together and confront with their indications the amount of moisture in the air at any time1 you will scarcely be mistaken in knowing what kind of weather you are likely to have for the next two or three days1 which for the gardener1 the farmer1 soldier1 sailor1 and traveller must be frequently of considerable importance40#ad ,footnote #ad3 ,the late ,admiral ,fitzroy4 ,we are indebted to ,m4 ,buys ,ballot1 a ,dutch meteorologist1 for an invaluable generalization1 the importance of which it is almost impossible to over-estimate4 ,this distinguished savant says3--8,it is a fact above all doubt that the wind that comes is nearly at right angles to the line between the places of highest and lowest barometer readings4 ,the wind has the place of lowest barometer at its left hand1 and is stronger in proportion as the difference of barometer readings is greater40 ,these facts have been variously stated by other writers2 for example3 8,stand with your back to the wind1 and the barometer will be lower on your left hand than on your right20 8,facing the wind the centre of depression bears in the right-hand direction10 statements which can be verified at any time by a brief study of the 8,weather ,charts0 now published in the daily journals4 ,the value of the law consists in its connecting the surface winds of our planet with the actual pressure of the air itself1 and it admits of the following tabulation3-- ---------------------------------------- ------------ ,the wind is ,the wind is ,the wind is ,the wind is ,,northerly ,,southerly ,,easterly ,,westerly when the when the when the when the ,,barometer ,,barometer ,,barometer ,,barometer is1 in the is1 in the is1 in the is1 in the ,n4 ,n4 ,n4 ,high4 ,n4 ,low4 about about ,s4 ,low4 ,s4 ,high4 ,s4 equal4 ,s4 equal4 ,e4 ,e4 ,e4 ,low4 ,e4 ,high4 about about ,w4 ,high4 ,w4 ,low4 ,w4 equal4 ,w4 equal4 ---------------------------------------- ------------ which can be verified by the reader from the daily ,weather ,charts in the newspapers4 ,the above are deductions from ,buys ,ballot's ,law1 still further impressed on the memory by taking four outline maps of the ,british ,isles1 inserting the names of ,thurso1 ,penzance1 ,yarmouth1 and ,valentia1 with barometer readings of the kind above named at each place1 and then drawing a large arrow in red ink across the centre of each map in the direction appropriate to the readings4 ,mr4 ,strachan1 in his able pamphlet on 8,weather ,forecasts10 puts the matter thus3 8,it follows from ,ballot's ,law that in the northern temperate zone the winds will circulate around an area of low atmospherical pressure in the reverse direction to the movement of the hands of a watch1 and that the air will flow away from a region of high pressure1 and cause an apparent circulation of the winds around it1 in the direction of watch hands40 ,and as the result of a careful digest of data contained in the eleventh number of meteorological papers1 published by the ,board of ,trade1 he has established the following valuable propositions4 ,as introductory to the propositions1 it should be stated that the positions of observations were the following3-- ,places4 ,latitude4 ,longitude4 ,nairn #eg #bi ,n4 #d #ac ,w4 ,brest #dh #bh #d #bi ,w4 ,valentia #ea #ef #aj #ai ,w4 ,yarmouth #eb #cg #a #dd ,e4 ,portrush 7or ,greencastle7 #ee #ab #f #dj ,w4 ,shields #ee #j #a #bg ,w4 ,nairn and ,brest are situated nearly on the same meridian1 about #edj geographical miles apart4 ,valentia and ,yarmouth are nearly on the same parallel of latitude1 about #dej miles apart4 ,portrush and ,shields1 distant #ahj miles1 are on a parallel which is nearly as remote from the parallel of ,nairn as that of ,valentia and ,yarmouth is from the one passing through ,brest2 and ,shields is about as much to the westward of ,yarmouth as ,portrush is to the eastward of ,valentia4 ,when observations have not been obtainable for ,brest1 those made at ,penzance have been used instead4 ,proposition #a4--,whenever the atmospherical pressure is greater at ,brest than at ,nairn1 while it is of the same or nearly the same value at ,valentia and ,yarmouth1 being gradually less from south to north1 the winds over the ,british ,isles are westerly4 ,proposition #b4--,whenever the pressure at ,nairn is greater than at ,brest1 while its values at ,valentia and ,yarmouth are equal1 or nearly so1 the winds over the ,british ,isles are easterly4 ,proposition #c4--,whenever the pressure at ,valentia is greater than at ,yarmouth1 while its values at ,brest and ,nairn are nearly equal1 the winds over the ,british ,isles are northerly4 ,proposition #d4--,whenever the pressure at ,yarmouth exceeds that at ,valentia1 while there is equality of pressure at ,nairn and ,brest1 the winds of the ,british ,isles are southerly4 ,proposition #e4--,whenever the pressure of the atmosphere is equal1 or nearly so1 at ,brest1 ,valentia1 ,nairn1 and ,yarmouth1 and generally uniform1 the winds over the ,british ,isles are variable in direction and light in force4 ,the data from which the foregoing propositions were deduced1 and indeed all other cases calculated by ,mr4 ,strachan1 show in every well marked instance that when the atmospherical pressure was 7#a7 greater in the south than in the north1 the wind had westing2 7#b7 greater in the north than in the south1 the wind had easting2 7#c7 greater in the east than in the west1 the wind had southing2 7#d7 greater in the west than in the east1 the wind had northing2 7#e7 uniformly high1 or uniformly low1 variable light winds 7with fine weather in the former case1 and vapoury or wet weather in the latter74 ,conditions 7#a7 and 7#c7 give winds from the ,s4,w4 quarter4 ,conditions 7#a7 and 7#d7 give winds from the ,n4,w4 quarter4 ,conditions 7#b7 and 7#d7 give winds from the ,n4,e4 quarter4 ,conditions 7#b7 and 7#c7 give winds from the ,s4,e4 quarter4 ,these principles may be employed to set forth the mode of foretelling the impending change of wind as regards its direction and force2 for the atmospherical pressure may change-- 7a7 uniformly over the whole area of observation2 7b7 by increasing in the south1 or 7which causes a similar statical force7 by decreasing in the north2 7c7 by increasing in the north1 or 7which has the same effect7 by decreasing in the south2 7d7 by increasing in the west1 or 7which has the same effect7 by decreasing in the east2 7e7 by increasing in the east1 or 7which has the same effect7 by decreasing in the west2 ---------------------------------------- -------------------------------- ,scale1 #j to #f4 ,pressure in pounds per square foot4 ,miles per hour4 ,seaman's ,nomenclature4 ,scale1 #j to #ab4 ,beaufort ,scale4 ---------------------------------------- --------------------------- #jj #jjj #b ,calm #j #je #jbe #e ,light ,air #a ,just sufficient to make steerage way4 ,breeze #aj #ajjaj ,light #b ,with which a ship with #a to #b knots4 #ae #bbeae ,gentle #c all sail set would go #c to #d #bj #djjbj ,moderate #d in smooth water4 #e to #f #be #fbebg ,fresh #e ,royals1 c4 #cj #ijjce ,strong #f ,in which ,single ,reefs and ,t4,g4 ,sails4 -- -- #db -- -- ,double ,reefs and ,jib1 c4 ,gale she could #ce -- #ej ,moderate #g #djafjjfj ,fresh #h ,triple ,reefs1 c4 #debjbe-- ,strong #i just carry ,close ,reefs and ,courses4 #ejbejjgj ,whole #aj ,in which she could just bear close-reefed ,maintopsail and reefed ,foresail4 #eecjbehj ,storm #aa ,under ,storm ,staysails or ,trysails4 #fjcfjjij ,hurricane #ab ,bare ,poles4 ---------------------------------------- --------------------------- ,with 7a7 similar wind and weather will continue4 7b7 winds will veer towards west4 7c7 east4 7d7 north4 7e7 south4 8,the probable strength of wind will be in proportion to the rate of increase of statical force1 or differences of barometrical readings4 ,the position of least pressure must be carefully considered2 as1 in accordance with the law1 the wind will blow around that locality4 ,the same remark applies to areas of high pressure1 which1 however1 very rarely occur in a well-defined manner over the ,british ,isles40 ,referring to the table on page #gf1 the scale #j to #f was formerly used by meteorological observers at land stations1 and it was intended to express1 when the square of the grade was obtained1 the pressure of the wind as given in the second column4 8,the velocity is an approximation as near as can be obtained1 from the values assigned by ,neumayer1 ,stow1 ,laughton1 ,scott1 ,harris1 ,james1 c40#ae ,footnote #ae3 ,strachan's 8,portable ,meteorological ,register10 #dth edition4 ,few meteorological axioms are better established than that which embodies the fact that 8every wind brings its weather10 and the primary cause of wind being the motion of the air induced by rarefaction1 it is obvious that there is a constant tendency for the equatorial and polar currents in any locality to establish an equilibrium1 and this consideration is found to facilitate weather predictions for extended periods4 ,thus1 in consequence of the unusual prevalence of east winds in the spring of #ahfb1 a wet summer was predicted4 ,the prediction was fully borne out by an incessant continuance of south-west winds1 with clouded skies and the usual accompaniment of deluges of rain4 ,these winds continuing1 with slight intermissions only1 till the spring of the following year1 less than the usual number of south-west winds was looked for during the summer2 the result fully justified the anticipation1 the summer of #ahfc being fine and warm1 especially during the earlier portion4 ,similarly1 without committing the inaccuracies of ,murphy in #ahch1 the summer of #ahgg may be reasonably expected to be a dry and cool one from the long continuance of warm and wet months in the winter of #ahgf-g4 ,the scientific research and mechanical ingenuity directed of late years to producing trustworthy estimates of the direction1 pressure1 and velocity of the wind1 have resulted in the production of a series of instruments1 possessing great precision and accuracy4 ,illustration3 #ed4 ,wind ,vane4 ,scale about #a_/bj4 ,the direction of the wind is indicated by vanes1 a very efficient form of which is shown at ,fig4 #ed1 the velocity by revolving cups1 and the pressure by the pressure plate and by calculation from the known velocity4 ,the ,pendulum ,anemometer 7,fig4 #ef7 shows in a simple manner the direction and pressure of the wind4 ,the peculiarly shaped vane ensures the surface of the swinging pressure plate ,b being always kept towards the wind4 ,the pendulum plate hangs1 during a calm1 quite vertically1 indicating zero1 and as the pressure increases it will be raised through all degrees of elevation from #a to #ab4 ,the vane is perforated with holes large enough to be visible at some distance from the ground1 the #e and #aj being specially larger1 so that the angle to which the pressure plate is raised can be quickly noted4 ,illustration3 #ee4 ,compass ,bearings4 ,scale about #a_/bj4 ,there is a simple contrivance 7for the convenience of travellers7 called a ,portable ,wind ,vane1 or ,anemometer1 ,it is furnished with a compass and bar needle1 c41 and will tell the true direction of the wind to within a half point4 ,illustration3 #ef4 ,prestel's ,pendulum ,anemometer4 ,scale about #a_/ab4 ,illustration3 #eg4 ,lind's ,anemometer4 ,scale about #a_/e4 ,lind's ,anemometer or ,wind ,gauge ranks among the earliest forms of instruments designed to estimate the force of the wind4 ,it consists of a glass syphon1 the limbs of which are parallel to each other1 mounted on a vertical rod1 on which it freely oscillates by the action of the vane which surmounts it4 ,the upper end of one limb of the syphon is bent outward at right angles to the main direction1 and the action of the vane keeps this open end of the tube always towards the quarter from whence the wind blows4 ,between the limbs of the syphon is placed a scale graduated from #j to #c in inches and #ajths1 the zero being in the centre of the scale4 ,when the instrument is used1 it is only necessary to fill the tube with water to the zero of the scale1 and then expose it to the wind4 ,the natural consequence of wind acting on the surface of the water is to depress it in one limb and raise it in the other1 and the sum of the depression and elevation is the height of a column of water which the wind is capable of sustaining at the time of observation4 ,sudden gusts of wind are apt to produce a jumping effect on the water in the tube1 and to diminish this the bend of the syphon is contracted4 ,a brass plate is attached to the foot of the instrument1 bearing the letters indicating the cardinal points of the compass1 to show the direction of the wind4 ,dr4 ,robinson1 of ,armagh1 introduced an instrument1 in #ahej1 which consists of four hemispherical copper cups attached to the arms of a metal cross4 ,the vertical axis upon which these are secured has at its lower extremity an endless screw placed in gear with a train of wheels and pinions4 ,each wheel is graduated respectively to #a_/ajth1 #a mile1 #aj miles1 #ajj miles1 #a1jjj miles1 and these revolve behind a fixed index1 the readings of which are taken according to the indications on the dials4 ,dr4 ,robinson entertained the theory that the cups 7measuring from their centres7 revolved with one-third of the wind's velocity2 and this theory having been fully supported by experiment1 due allowance has been made in graduating the wheels so that the true velocity is obtained by direct observation4 ,in an improved form of this anemometer the hemispherical cups are retained1 but the index portion of the instrument consists of two graduated concentric circles1 the inner one representing five miles divided into #ajths1 and the outer one bearing #ajj divisions1 each of which is equivalent to five miles4 ,at the top of the dial is a fixed index1 which1 as the toothed wheel revolves1 marks on the inner circle the miles 7up to five7 and #ajths of miles the wind has travelled1 while a movable index1 which revolves with the wheel1 indicates on the outer circle the passage of every five miles4 ,illustration3 #eh4 ,improved ,anemometer4 ,scale about #a_/e4 ,this instrument can be made very portable by removing the arms bearing the cups1 when the whole may be packed with iron shaft in a case #ae #ac #d inches4 ,it may be placed in any desired position by screwing the iron shaft supplied with it into the hole provided for the purpose1 and fixing the apparatus on a pole or on an elevated stand1 if possible1 in an open space exposed to the direct action of the wind4 ,if1 when placing the instrument1 the hands stand at #j1 the next reading will1 of course1 show the number of miles the wind has traversed2 but1 should they stand otherwise1 the reading may be noted and deducted from the second reading1 thus3 ,suppose the fixed index points to #be and the movable index to #abe1 the reading after #ab hours may be #bjj on the outer circle and #cj on the inner circle3 these added together yield #bjc4 ,by deducting the previous reading #abge1 we have the true reading--viz41 #gee miles as the distance travelled by the wind4 ,having obtained the velocity of the wind in this manner in miles per hour1 the table on page #hc1 from ,col4 ,sir ,henry ,james's 8,instructions for ,taking ,meteorological ,observations10 will enable the observer to calculate the pressure in pounds per square foot4 ,,weather ,,notation4 ,the following letters are used to denote the state of the weather3-- b denotes blue sky1 whether with clear or slightly hazy atmosphere4 c cloudy1 that is detached opening clouds4 d drizzling rain4 f fog4 h hail4 l lightning4 m misty1 or hazy so as to interrupt the view4 o overcast1 gloomy1 dull4 p passing showers4 q squally4 r rain4 s snow4 t thunder4 u ugly1 threatening appearance of sky4 v unusual visibility of distant objects4 w wet1 that is dew4 ,a letter repeated denotes much1 as rr1 heavy rain2 ff1 dense fog2 and a figure attached denotes duration in hours1 as #adr1 #ad hours' rain4 ,by the combination of these letters all the ordinary phenomena of the weather may be recorded with certainty and brevity4 ,examples4--bc1 blue sky with less proportion of cloud2 cb1 more cloudy than clear2 #brrllt1 heavy rain for two hours1 with much lightning1 and some thunder4 ,,velocity ,,and ,,pressure ,,of ,,the ,,wind4 ,the ,pressure varies as the ,square of the ,velocity1 or ,p ,v#b4 ,the ,square of the ,velocity in ,miles per ,hour multiplied by #ejj gives the ,pressure in lbs4 per square ,foot1 or ,v#b #jje ,p4 ,the ,square ,root of #bjj times the ,pressure equals the ,velocity1 or 7#bjj ,p7 ,v4 ,the subjoined ,table is calculated from this data1 by ,,col4 ,,sir ,,henry ,,james1 of the ,ordnance ,survey ,office4 ---------------------------------------- --------------------------- ,pressure in lbs4 per ,square ,foot4 ,velocity in ,miles per ,hour4 ,pressure in lbs4 per ,square ,foot4 ,velocity in ,miles per ,hour4 ,pressure in lbs4 per ,square ,foot4 ,velocity in ,miles per ,hour4 ,pressure in lbs4 per ,square ,foot4 ,velocity in ,miles per ,hour4 ,pressure in lbs4 per ,square ,foot4 ,velocity in ,miles per ,hour4 ---------------------------------------- ------------------ oz4 lbs4 lbs4 lbs4 lbs4 #jjh #ajjj #fgecfgdbaggeeiehabhgegehbhcige #hiafb #jbe #agfg #gjjcgdafahjjfjjjjbijjgfaegdjjj #hiddb #jej #bejj #gbechjghahbefjdaebibegfdhedjbe #higba #jge #cjfa #gejchgbiahejfjhbgbiejgfhaadjej #ijjjj #ajj #cece #ggecicgjahgefabcgbigeggacfdjge #ijbgg #bjj #ejjj #hjjdjjjjaijjfafddcjjjggdeidajj #ijeec #cjj #fabc #hbedjfbjaibefbjdhcjbeggghadabe #ijhbi #djj #gjga #hejdabcaaiejfbddicjejghajbdaej #iaajd #ejj #gije #hgedahccaigefbhaicjgeghdbadage #iacgh #fjj #hffj #ijjdbdbfbjjjfcbdecajjghgdjdbjj #iafea #gjj #iced #ibedcjaabjbefcfcicabegijefdbbe #iaibc #hjjajjjj #iejdcehhbjejfdjcacaejgicgbdbej #ibaie #ijjajfjf #igeddaehbjgefddbjcagegifhfdbge #ibdff #ajjjaaahjajjjddgbabajjfdhjgcbjjhjjjjdcj j #ibgcf #aajjaagbfajbedebgfbabefeaibcbbehjcaadcb e #icjje #abjjabbdgajejdehbebaejfeegdcbejhjfbbdce j #icbgc #acjjabgdgajgedfcfhbagefeiedcbgehjicbdcg e #iceda #adjjacbbhaajjdfijdbbjjffccbccjjhabdjddj j #ichjh #aejjacficaabedgdcdbbbeffgjhccbehaedgddb e #idjgd #aaejdgiehbbejfgjhbccejhahecddej #idcci lbs4 #aagedhdgfbbgefgdecccgehbaehddge #idfjd #ajjadadbabjjdhihibcjjfghbccdjjhbdfbdejj #idhfh #abeaehaaabbedidigbcbefhaijcdbehbgfddebf #iecic #aejagcbjabejejjjjbcejfheefcdejhcjffdeej #ieaca #ageahgjhabgeejdigbcgefhibjcdgehccffdege #iefee #bjjbjjjjacjjejiijbdjjfibhbcejjhcfffdfjj #ieiaf #bbebabacacbeeadghbdbefifdacebehcifddfbe #ifagf #bejbbcfjacejeaifabdejgjjjjceejhdbfadfej #ifdcf #bgebcdebacgeebddjbdgegjcefcegehdefgdfge #iffie #cjjbddidadjjebiaebejjgjgajcfjjhdhebdgjj #ifiec #cbebedieadbeecchebebegajfccfbehe #adfdgbe #igbaa #cejbfdegadejecheabeejgadadcfejheddjdgej #igdfg #cgebgchfadgeedcacbegegagfccfgehegcbdgge #iggbd #djjbhbhdaejjedggbbfjjgbaaacgjjhfjbcdhjj #igigi #dbebiaedaebeeebbfbfbegbdefcgbehfcacdhbe #ihbcd #dejcjjjjaeejeefggbfejgbhjacgejhffjbdhej #ihdhh #dgecjhbbaegeefabdbfgegc #adccggehfhijdhge #ihgdb #ejjcafbbafjjefefhbgjjgcdhdchjjhgaggdijj #ihiid #ebecbdjcafbeegjjhbgbegchbdchbehgdfddibe #iibdg #eejccaffafejegdaebgejgdafachejhggdidiej #iidih #egecciaaafgeeghgibggegddihchgehhjcddige #iigdi #fjjcdfdaagjjehcjibhjjgdhcccijjhhcagejjj #ajjjjj #fbececeeagbeehgcfbhbegeaffcibehhfjj #fejcfjeeagejeiafjbhejgedihciejhhhha ---------------------------------------- ------------------ ,this is the only table hitherto much in use for converting velocity into pressure1 and was prepared by ,smeaton and others4 ,it does not1 however1 express the true relation1 which has yet to be determined4 ,the ,anemograph1 or ,self-,recording ,wind ,gauge1 has for its object the registration of the velocity and direction of the wind from day to day4 ,figs4 #ei and #fj show the form designed and arranged by ,mr4 ,beckley1 of the ,kew ,observatory1 which has been adopted by the ,meteorological ,office4 ,illustration3 #ei4 ,anemograph4 ,scale about #a_/bj4 ,portion for exterior of observatory4 ,it consists of a set of hemispherical cups and vanes1 which are exposed on the roof of the house1 and of the recording apparatus1 which is placed inside the house4 ,the motion imparted to the hemispherical cups by the wind is communicated to the steel shaft ,b1 which1 passing through the hollow shaft ,c1 and having at its lower end an endless screw1 works into a series of wheels in the iron box ,d1 which reduces the angular velocity #g1jjj times4 ,at the required distance the motion1 having emerged at ,e1 is connected with ,f1 where1 by means of bevelled wheels1 it moves the spiral brass registering pencil ,c1 which is arranged so that each revolution records #ej miles of velocity on the prepared paper ,h4 ,the direction of the wind is indicated by the arrow ,l1 which is kept in position by the fans ,m4 ,these communicate1 by an endless screw and train of wheels1 through the shaft ,c and the box ,d to the recording apparatus1 consisting of a spiral brass pencil1 which in one revolution records variations through the cardinal points of the compass1 on the same prepared paper as that which receives the record of velocity4 ,illustration3 #fj4 ,anemograph4 ,scale about #a_/bj4 ,portion for interior of observatory4 ,the paper is held on the drum by two small clips1 and may be readily changed1 by unclamping the cross ,v1 without disturbing the drum or any other part of the instrument4 ,illustration3 #fa4 ,self-recording ,magnetometer1 ,kew ,observatory4 ,,vi4--,,electrification4 ,william ,gilbert1 a physician of ,colchester1 first showed in #afjj that the earth as a whole has the properties of a magnet1 and consequently that the directive action exerted by it upon a compass needle represents only a special case of the mutual action of two magnets4 ,in #ahde1 ,faraday established the fact that susceptibility to magnetic force is not1 as was generally believed1 confined to iron1 nickel1 and a few other substances1 but is a property of all substances4 ,according to ,balfour ,stewart1 auror and earth currents may be regarded as secondary currents resulting from changes in the earth's magnetism4 ,magnetic phenomena are included under the general term terrestrial magnetic elements1 and consist of magnetic declination1 inclination1 and intensity4 ,these are for convenience determined separately2 the first by an instrument called a ,declinometer1 and the second by an ,inclinometer or ,dipping ,needle4 ,the ,declinometer is also made to serve the additional purpose of measuring the intensity of the earth's magnetic force1 which it effects on a principle similar to that by which the force of gravity is determined by the oscillations of a pendulum of known length on any given portion of the earth's surface4 ,the declinometer needle is made to oscillate1 and the number of oscillations in a given time counted2 due allowance being made for the strength of the needle1 it is obvious that the force which restores the needle to rest can be estimated4 ,to ascertain the angle of declination1 the zero line of the compass card is made to coincide with the geographical north and south line2 and the angle which the direction of the needle makes with this line is then read off on a graduated circle over which the needle turns4 ,the magnetic inclination or dip of the needle is estimated by observing the inclination to a horizontal plane of a needle turning on the vertical plane which passes through the magnetic north and south points4 ,illustration3 #fb4 ,fig4 #fb shows a simple form of magnetic needle suspended on a fine steel point1 which is supported by a brass stand2 the addition of a graduated circle would constitute such an arrangement a ,declinometer4 ,illustration3 #fc4 ,illustration3 #fd4 ,fig4 #fc gives the appearance of the dipping needle1 or ,inclinometer1 and ,fig4 #fd an arrangement by which both kinds of terrestrial as well as local attraction may be shown4 ,these components of the earth's magnetism undergo not only an annual but a daily and even hourly variation1 apparently connected in some occult manner with the frequency of the sun's spots4 ,the needle sometimes suffers such exceptional perturbations as to suggest the idea of a magnetic storm4 ,these disturbances are usually accompanied 7in polar regions7 by luminous phenomena called auror4 ,continuous automatic records of them1 therefore1 is of great value1 as facilitating inductive research which may lead to valuable practical results4 ,accordingly the ,royal ,society have adopted for the ,kew and other observatories the form of ,magnetograph1 or ,self-recording ,magnetometer1 shown at ,fig4 #fa1 by means of which the variations just referred to are registered by the oscillations of three magnets on photographically prepared paper1 stretched on a drum revolved by clockwork4 ,one magnet is suspended in the magnetic meridian by a silk thread1 and1 by the aid of a mirror attached1 it describes on the cylinder1 moved by clockwork in the centre pier1 all the variations in the magnetic declination4 ,the other two components of the magnetic force of the earth are given by the other magnets4 ,that recording the vertical variations rests on two agate edges under a glass shade1 while the horizontal component magnet is suspended by a double silk thread1 under the shade to the right of the picture1 being retained by the tension of the thread in a position nearly at right angles to the magnetic meridian4 ,the clock box in the centre covers the three revolving cylinders bearing the sensitive photographic paper1 and to each magnet is attached a semicircular mirror1 which reflects the rays from a gas jet to one of the cylinders1 and thus describes by a curved line the oscillations of the magnet4 ,a second semicircular mirror is fixed to the pier on which the instrument stands1 and consequently describes a straight line1 or zero1 from whence the curves are measured4 ,to avoid errors attending sudden changes of temperature1 underground vaults are always chosen for magnetic observations1 and also on account of light being more easily and perfectly excluded4 ,,atmospheric ,,electricity4 ,since the performance of ,franklin's famous kite experiment1 by which he determined the identity of lightning with the electrical discharge from a machine1 much attention has been devoted1 not only to that form of atmospheric electricity which displays itself in the thunder-cloud1 but to the electric condition of the air in all states of the weather4 ,these researches have established the fact that the air is always in an electrical condition1 even when the sky is clear and free from thunder-clouds4 ,the instruments employed for ascertaining the kind and intensity of atmospheric electricity are called ,electroscopes4 ,fig4 #fe shows a modification of ,saussure's ,electroscope1 the basis of which is a narrow-mouthed flint glass bottle with a divided scale to indicate the degree of divergence of the gold leaves or straws4 ,to protect the lower part from rain1 it is covered by a metallic shield about five inches in diameter4 ,bohnenberger's ,electroscope indicates the presence and quality of feeble electric currents4 ,peltier's ,electrometer yields the same result by the deflection of a magnetic needle4 ,this latter has been in use at ,brussels for thirty years1 and at ,utrecht for twenty years1 and is highly recommended4 ,illustration3 #fe4 ,electroscope4 ,scale about #a_/g4 ,singer's ,atmospheric ,electroscope is an efficient form of the instrument in which an ordinary gold-leaf electrometer has attached to its circular brass plate a brass rod two feet in length1 with a clip at its upper extremity to receive a lighted paper or cigar fusee4 ,the electricity of the air in immediate contact with the flame1 causes1 by induction1 electricity of the opposite nature to accumulate at the upper extremity1 where it is constantly carried off by the convection currents in the flame1 leaving the conductor charged with the same kind and power of electricity as that contained in the air at the time of the experiment4 ,the principle of this method was initiated by ,volta1 and has been extended and applied by ,sir ,william ,thomson in his ,water-dropping ,collector1 which consists of an insulated cistern from which water escapes through a jet so fine that it breaks into drops immediately after leaving the nozzle of the tube4 ,the result of this is that in half a minute from the starting of the stream the can is found to be electrified to the same extent as the air at the point of the tube4 ,the scale value of each instrument has to be separately determined by repeated comparative experiments1 and involves much delicacy of manipulation4 ,it is chiefly important for the ordinary observer to know that the occurrence of thunder and lightning should be always noted in the column headed 8,remarks40 ,illustration3 #ff4 ,lightning ,conductor4 ,scale about #a_/aj4 ,the destructive effects of lightning are too well known to need description here2 the means1 however1 by which these may be averted demand a brief notice4 ,lightning when discharged from a cloud will always choose the better of any two conductors which may present themselves4 ,the stone of a church steeple and the wood of a ship's mast are bad conductors1 but a galvanized iron wire rope is the best possible conductor1 and accordingly this material is now generally employed for the purpose4 ,a lightning conductor consists of three parts3 #a1 the rod1 which extends beyond the summit of the building1 #b1 the conductor1 which connects the rod with the underground portion1 and #c1 the part underground4 ,the connection between each of these must be absolutely perfect1 or the conductor will be faulty4 ,the top is usually of solid copper tipped with platinum 7,fig4 #ff71 the body of galvanized iron rope1 so as to adapt itself to the inequalities of the building and yet have no sharp turns in it1 while the part underground is of solid iron rod4 ,this latter portion should extend straight underground for two feet1 and being bent at right angles away from the wall1 should rest in a horizontal drain #aj to #ae feet long filled with charcoal1 and be again bent downwards into a well of water4 ,should water not be available1 it should rest in the centre of a hole #ae feet deep and #aj inches in diameter1 tightly packed with charcoal1 which1 while conducting the electricity from the rod into the earth1 serves also to preserve the iron from rusting4 ,,ozone4 ,the atmosphere1 besides holding the vapour of water diffused throughout its mass1 contains also minute traces of carbonic acid and ammonia1 and a very remarkable substance called ,ozone4 ,oxygen1 one of the component gases of the atmosphere1 is capable of existing in two conditions2 one in which it is comparatively passive1 and another in which it possesses exceptional chemical activity1 dependent apparently upon its electrical condition1 and in which state it possesses a peculiar smell which has caused it to be named ozone4#af ,the characteristic odour is always observable near a powerful electric machine when it is being worked1 near a battery used for the decomposition of water1 and in the air after the passage of a flash of lightning4 ,its presence is most marked near the sea-coast1 and in localities remarkable for their salubrity2 and on account of its influence on health1 it has been proposed by ,schonbein and others to include ozonometrical observations with the ordinary meteorological observations4 ,footnote #af3 ,greek ozo1 ,i smell4 ,although in minute quantities it is favourable to health1 when existing in undue proportion it irritates the mucous membrane of the nose and throat1 producing painful sores4 ,it attacks india-rubber1 bleaches indigo1 and oxidizes silver and mercury1 differing in all these points from ordinary atmospheric oxygen4 ,the chemical energy it possesses 7which exceeds that of ordinary oxygen as much as the latter exceeds atmospheric air as an oxidizing agent7 affords the means of ascertaining its presence and quantity4 ,it liberates iodine from its combination with potassium1 and free iodine colours starch a deep blue4 ,schonbein1 the discoverer of ozone1 found that when strips of paper previously saturated with starch and iodide of potassium and dried were exposed freely to the air but protected from rain and the direct action of the sun1 they underwent a peculiar discoloration 7when immersed in water7 after an exposure of #bd hours4 ,a scale of tints numbered from one to ten afforded the means of comparative observation1 and thus the ,ozonometer was constructed1 and a means established of registering the amount of ozone in the air of various localities from day to day4 ,schonbein also observed that the proportion of ozone was largely augmented after heavy falls of snow4 ,for the exposure of the ozone papers1 an ozone cage is employed1 as shown at ,fig4 #fg4 ,illustration3 #fg4 ,ozone ,cage4 ,scale about #a_/f4 ,ozone may be prepared artificially as a disinfectant by cautiously mixing without friction or concussion equal parts of peroxide of manganese1 permanganate of potash1 and oxalic acid4 ,for a room containing #a1jjj cubic feet1 two teaspoonfuls of the powder1 placed in a dish and moistened with water occasionally1 will develop the ozone and disinfect the surrounding air without producing cough4 ,the most important and interesting series of facts1 however1 connected with ozone are those established by the researches of ,m4 ,houzeau1 who states3-- #a4 ,that country air contains an odorous oxidizing substance1 with the power of bleaching blue litmus1 without previously reddening it1 of destroying bad smells1 and of bluing iodized red litmus4 #b4 ,that this substance is ozone4 #c4 ,that the amount of ozone in the air at different times and places is variable1 but this is at most #a_/gjj1jjj of its volume1 or #a volume of ozone in #gjj1jjj of air4 #d4 ,that ozone is found much more frequently in the country than in towns4 #e4 ,that ozone is in greatest quantity in spring1 less in summer1 diminishes in autumn1 and is least in winter4 #f4 ,it is most frequently detected on rainy days1 and during great atmospheric disturbances4 #g4 ,that atmospheric electricity is apparently the great generator of ozone4 ,the subject is one of great interest in its bearings on health1 and opens a wide field of scientific research1 as may be inferred from the opinion expressed by the ,vienna ,congress1 which is that 8the existing methods of determining the amount of ozone in the atmosphere are insufficient1 and the ,congress therefore recommends investigations for the discovery of better methods40 ,mr4 ,lowe has published the valuable weather warnings tabulated on page #id1 which are interesting as showing from a given number of observations the value of each phenomenon3-- ---------------------------------------- ----------------------------- ,no4 of ,followed in observations4 #bd hours by -------------------------- ,,dew4 ,fine4 ,rain4 ,dew profuse #bda #aif #dc ,dew from #ast ,april to #cjth ,sept4 #ahe #afa #bd ,dew from #ast ,oct4 to #cjth ,march #ef #cg #ai ,,clouds4 ,white stratus in the valley #bbi #bja #bh ,coloured clouds at sunset #ce #bf #i ,,sun4 ,solar halos #bjd #acc #ga ,sun red and shorn of rays #cd #ca #c ,mock suns #ce #ai #f ,sun shone through thin cirro-stratus #ac #f #g ,sun pale and sparkling #ea #bg #bd ,,frost4 ,white frost #gc #ei #ad ,,moon4 ,lunar halos #ajb #ea #ea ,mock moons #i #g #b ,lunar burr #fd #dg #ag ,moon shining dimly #ah #ab #f ,moon rose of a red colour #h #g #a ,,stars4 ,falling stars abundant #he #fe #bj ,stars bright #hc #fd #ai ,stars dim #ed #cb #bb ,stars scintillated #ad #ab #b ,,aurora4 ,aurora borealis #gf #di #bg ,,animals4 ,bats flying about in the evening #fa #de #af ,toads in the evening #ag #ab #e ,landrails clamorous #ad #ac #a ,ducks and geese noisy #aj #g #c ,spiders hanging on webs in the evening #h #e #c ,fish rise in the lake #ae #i #f ,,smoke4 ,smoke rising perpendicularly #f #e #a ---------------------------------------- ---------------------------- ,among the animals whose movements give weather warnings few are more trustworthy than the leech4 ,the reader may verify this by placing one in a broad glass bottle1 tied over with perforated leather1 or bladder4 ,if placed in a northern aspect1 the leech will be found to behave in the following manner3-- #a4 ,on the approach of fine or frosty weather1 according to the season1 it will be found curled up at the bottom4 #b4 ,on the approach of rain1 snow1 or wind1 it will rise excitedly to the surface4 #c4 ,thunder will cause it to be much agitated1 and to leave the water entirely4 ,,periods4--,m4 ,kppen states1 as the result of his examination into the chances of a change of weather1 that the weather has a decided tendency to preserve its character4 ,thus1 at ,brussels1 if it has rained for nine or ten days successively1 the next day will be wet also in four cases out of five2 and the chance of a change decreases with the length of time for which the weather from which the change is to take place has lasted4 ,in the case of temperature for five-day periods1 the same principle holds good2#ag for if a cold five-day period sets in after warm weather1 we can bet two to one that the next such period will be cold too2 but if the cold has lasted for two months1 we can bet nearly eight to one that the first five days of the next month will be cold too4 ,the chance of change is1 however1 greater for the five-day periods than for single days4 ,similar results follow for the months1 but here again the chance of change shows an increase4 ,footnote #ag3 8,recent ,progress in ,weather ,knowledge10 by ,r4 ,h4 ,scott1 ,f4,r4,s4 8,if we revert to the instance first cited1 that of rain1 the result is1 not that if it once begins to rain the chances are in favour of its never ceasing2 all that is implied is1 that the chances are against its ceasing on a definite day1 and that they increase with the length of time the rain has lasted4 ,the problem is similar to that of human life3 the chance of a baby one year old living another year is less than that of a man of thirty4 8,the practical meaning of all this is1 that although we know that a compensating anomaly for all extraordinary weather exists somewhere on the earth's surface1 e4g41 the very common case of intense cold in ,america1 while we have a mild winter in ,britain1 there is no reason as yet ascertained to anticipate that this compensation will occur at any given place during the year4 ,in other words1 when definite conditions of weather have thoroughly established themselves1 it is only with great difficulty that the courses of the atmospheric currents are changed40 ,to bring within the limits of a popular pamphlet a notice of the various phenomena classed under the head of ,meteorology1 it has been necessary to exercise the utmost brevity4 ,brief1 however1 as the treatment has been1 reference has been made to the sciences of ,heat1 ,light1 ,electricity1 ,magnetism1 ,gravitation1 ,astronomy1 ,chemistry1 ,geography1 and ,geology1 thus corroborating the testimony of ,sir ,john ,herschel1 who states that 8it can hardly be impressed forcibly enough on the attention of the student of nature that there is scarcely any natural phenomenon which can be fully and completely explained in all its circumstances without a union of several--perhaps of all--the sciences2 and it cannot be doubted that whatever walk of science he may determine to pursue1 impossible as it is for a finite capacity to explore all with any chance of success1 he will find it illuminated in proportion to the light which he is enabled to throw upon it from surrounding regions4 ,but1 independently of this advantage1 the glimpse which may thus be obtained of the harmony of ,creation1 of the unity of its plan1 of the theory of the material universe1 is one of the most exalted objects of contemplation which can be presented to the faculties of a rational being4 ,in such a general survey he perceives that science is a whole whose source is lost in infinity1 and which nothing but the imperfection of our nature obliges us to divide4 ,he feels his nothingness in his attempts to grasp it1 and he bows with humility and adoration before that ,supreme ,intelligence who alone can comprehend it1 and who #8in the beginning saw everything that ,he had made1 and behold it was very good4'0 ,j4 ,,and ,w4 ,,rider1 ,,printers1 ,,london4 ---------------------------------------- -------------------------------- ,transcriber's note3 ,footnotes moved to end of paragraph4 ,all scale values in illustration captions retained4 ,the value may not be visually correct4 ,all fractions regularised to numerator_/denominator4 ,page #c1 #8,reaumur's' changed to #8,raumur's1' 8,raumur's scale0 ,page #i1 closing single quote changed to double quote4 ,page #ab1 full stop appended to illustration caption1 8,scale about #a_/bj40 ,page #af1 full stop appended to illustration caption1 8#i40 ,page #ag1 semicolon changed to full stop1 8444it has never been frozen40 ,page #bc1 first footnote changed from 8#h ,r #ah ,f40 to 8#h ,r #ej ,f40 ,page #bg1 #8vice vers' changed to #8vice versa1' 8444proportion1 and vice versa14440 ,page #cj1 dash changed to space1 8#biejj inches40 ,page #cd1 #8,hook' changed to #8,hooke1' 8444invented by ,dr4 ,hooke40 ,page #cg1 #8,aneriod' changed to #8,aneroid1' 8444by means of ,barometer or ,aneroid14440 ,page #ci1 space changed to stop1 8444between nine and ten p4m40 ,page #db1 space inserted between #8no' and #8less1' 8444at no less than #bab miles40 ,page #df1 illustration number added to caption1 8#ch4 ,damp ,detector40 ,page #ea1 comma moved to after #8weather1' 8,in cold calm weather14440 ,page #eg1 #86' changed to #81' 8cloud reflector10 ,page #eh1 #8#b4' changed to #8#bnd41' 8444and #bnd4 ,velocity of ,motion410 ,page #gd1 degrees changed to minutes1 8#eg #bi ,n40 ,page #gi1 #8,guage' changed to #8,gauge1' 8,lind's ,anemometer or ,wind ,gauge4440 ,page #hc1 powers changed from subscripts to superscripts1 8,v#b40 ,page #hg1 reference in text to ,fig4 #fe changed to ,fig4 #fd1 8444and ,fig4 #fd an arrangement4440 ,page #id1 full stops added after #8,,stars' and #8,,animals4'