,illustration3 ,,gassendi4 ,nov4 #g4 #ahfg #aj ,p4,m4 ,,the ,,moon3 ,,considered ,,as ,a ,,planet1 ,a ,,world1 and ,a ,,satellite4 ,,by ,,james ,,nasmyth1 ,c4,e4 ,,and ,,james ,,carpenter1 ,f4,r4,a4,s4 ,,late ,,of ,,the ,,royal ,,observatory1 ,,greenwich4 ,,with ,,twenty-,,four ,,illustrative ,,plates ,,of ,,lunar ,,objects1 ,,phenomena1 ,,and ,,scenery2 ,,numerous ,,woodcuts1 c4 ,,london3 ,,john ,,murray1 ,,albemarle ,,street4 #ahgd4 ,,london3 ,,bradbury1 ,,agnew1 ,,co41 ,,printers1 ,,whitefriars4 ,,to ,,his ,,grace ,,the ,,duke ,,of ,,argyll1 ,,in ,,recognition ,,of ,,his ,,long ,,continued ,,interest ,,in ,,the ,,subject ,,of ,,which ,,it ,,treats1 ,this ,volume ,,is ,,most ,,respectfully ,,dedicated ,,by ,,the ,,authors4 ,,preface4 ,the reason for this book's appearance may be set forth in a few words4 ,a long course of reflective scrutiny of the lunar surface with the aid of telescopes of considerable power1 and a consequent familiarity with the wonderful details there presented1 convinced us that there was yet something to be said about the moon1 that existing works on ,astronomy did not contain4 ,much valuable labour has been bestowed upon the topography of the moon1 and this subject we do not pretend to advance4 ,enough has also been written for the benefit of those who desire an acquaintance with the intricate movements of the moon in space2 and accordingly we pass this subject without notice4 ,but very little has been written respecting the moon's physiography1 or the causative phenomena of the features1 broad and detailed1 that the surface of our satellite presents for study4 ,our observations had led us to some conclusions1 respecting the cause of volcanic energy and the mode of its action as manifested in the characteristic craters and other eruptive phenomena that abound upon the moon's surface4 ,we have endeavoured to explain these phenomena by reference to a few natural laws1 and to connect them with the general hypothesis of planet formation which is now widely accepted by cosmologists4 ,the principal aim of our work is to lay these proffered explanations before the students and admirers of astronomy and science in general2 and we trust that what we have deduced concerning the moon may be taken as referring to a certain extent to other planets4 ,some reflections upon the moon considered as a world1 in reference to questions of habitability1 and to the peculiar conditions which would attend a sojourn on the lunar surface1 have appeared to us not inappropriate4 ,these1 though instructive1 are rather curious than important4 ,more worthy of respectful consideration are the few remarks we have offered upon the moon as a satellite and a benefactor to the inhabitants of this ,earth4 ,in reference to the ,illustrations accompanying this work1 more especially those which represent certain portions of the lunar surface as they are revealed by the aid of powerful telescopes1 such as those which we employed in our scrutiny1 it is proper that we should say a few words here on the means by which they have been produced4---- ,during upwards of thirty years of assiduous observation1 every favourable opportunity has been seized to educate the eye not only in respect to comprehending the general character of the moon's surface1 but also to examining minutely its marvellous details under every variety of phase1 in the hope of rightly understanding their true nature as well as the causes which had produced them4 ,this object was aided by making careful drawings of each portion or object when it was most favourably presented in the telescope4 ,these drawings were again and again repeated1 revised1 and compared with the actual objects1 the eye thus advancing in correctness and power of appreciating minute details1 while the hand was acquiring1 by assiduous practice1 the art of rendering correct representations of the objects in view4 ,in order to present these ,illustrations with as near an approach as possible to the absolute integrity of the original objects1 the idea occurred to us that by translating the drawings into models which1 when placed in the sun's rays1 would faithfully reproduce the lunar effects of light and shadow1 and then photographing the models so treated1 we should produce most faithful representations of the original4 ,the result was in every way highly satisfactory1 and has yielded pictures of the details of the lunar surface such as we feel every confidence in submitting to those of our readers who have made a special study of the subject4 ,it is hoped that those also who have not had opportunity to become intimately acquainted with the details of the lunar surface1 will be enabled to become so by aid of these ,illustrations4 ,in conclusion1 we think it desirable to add that the photographic illustrations above referred to are printed by well-established pigment processes which ensure their entire permanency4 ,,contents4 ,,page ,,chapter ,i4 ,,on ,,the ,,cosmical ,,origin ,,of ,,the ,,planets ,,of ,,the ,,solar ,,system4 #a ,origination of ,material ,things--,celestial ,vapours--,nebul--,their vast ,numbers--,sir ,w4 ,herschel's ,observations and ,classification--,buffon's ,cosmogony--,laplace's ,nebular ,hypothesis--,doubts upon its ,validity--,support from ,spectrum ,analysis ,,chapter ,,ii4 ,,the ,,generation ,,of ,,cosmical ,,heat4 #aa ,conservation of ,force--,indestructibility of ,force--,its ,convertibility into ,heat--,dawn of the ,doctrine--,mayer's ,deductions--,joule's ,experiments--,mechanical ,equivalent of ,heat--,gravitation the ,source of ,cosmical ,heat--,calculations of ,mayer and ,helmholtz--,the ,moon as an ,incandescent ,sphere--,not necessarily ,burning--,loss of ,heat by ,radiation--,cooling of ,external ,crust--,commencement of ,selenological ,history ,,chapter ,,iii4 ,,the ,,subsequent ,,cooling ,,of ,,the ,,igneous ,,body4 #ai ,cooling commenced from ,outer ,surface--,contraction by ,cooling--,expansion of ,molten ,matter upon ,solidification--,water not exceptional--,similar ,behaviour of ,molten ,iron--,floating of ,solid on ,molten ,metal--,currents in a ,pot of ,molten ,metal--,bursting of ,iron ,bottle by ,congelation of ,bismuth within--,evidence from ,furnace ,slag--,from the ,crater of ,vesuvius--,effects of ,contraction of ,moon's ,crust and ,expansion of ,interior--,production of ,ridges and ,wrinkles--,theory of ,wrinkles--,examples from shrivelled ,apple and ,hand ,,chapter ,,iv4 ,,the ,,form1 ,,magnitude1 ,,weight1 ,,and ,,density ,,of ,,the ,,lunar ,,globe4 #ca ,form of ,moon--,not perfectly ,spherical--,bulged towards ,earth--,diameter--,angular ,measure--,linear ,measure--,parallax of ,moon--,distance--,area of ,lunar ,sphere--,solid ,contents--,mass of ,moon--,law of ,gravitation--,mass determined by ,tides and other ,means--,density--,how obtained--,specific ,gravity of ,lunar ,matter--,force of ,gravity at ,surface--,how determined--,weights of similar ,bodies on ,earth and ,moon--,effects of like ,forces acting against ,gravity on ,earth and ,moon ,,chapter ,v4 ,,on ,,the ,,existence ,,or ,,non-,,existence ,,of ,a ,,lunar ,,atmosphere4 #ci ,subject of ,controversy--,phenomena of ,terrestrial ,atmosphere--,no ,counterparts on ,moon--,negative ,evidence from ,solar ,eclipses--,no ,twilight on ,moon--,evidence from ,spectrum ,analysis--,from ,occultations of ,stars--,absence of ,water or ,moisture--,cryophorus--,no ,reddening of ,sun's ,rays by ,vapours on ,moon--,no ,air or ,water to complicate ,discussions of ,lunar ,volcanic ,phenomena ,,chapter ,,vi4 ,,the ,,general ,,aspect ,,of ,,the ,,lunar ,,surface4 #ea ,pre-,telescopic ,ideas--,human ,countenance--,other supposed ,resemblances--,portrait of ,full ,moon--,permanence of ,features--,rotation of ,moon--,solar ,period and ,solar ,day on ,moon--,libration--,diurnal--,in ,latitude--,in ,longitude--,visible and ,invisible ,hemispheres--,telescopic ,scrutiny--,galileo's ,views--,features ,visible with ,low ,power--,low ,powers on small and large ,telescopes--,salient ,features--,craters--,plains--,bright ,streaks--,mountains--,higher ,telescopic ,powers--,detail ,scrutiny of ,features therewith--,discussion of ,high ,powers--,education of ,eye--,highest practicable ,power--,size of smallest ,visible ,objects ,,chapter ,,vii4 ,,topography ,,of ,,the ,,moon4 #fe ,reasons for ,mapping the ,moon--,early ,maps--,labours of ,langreen--,hevelius--,riccioli--,cassin i--,schroeter--,modern ,maps--,lohrman's--,beer and ,maedler's--,excellence of the last--,measurement of ,mountain ,heights--,need of a ,picture ,map--,formation of our own--,skeleton ,map--,table of conspicuous ,objects--,descriptions of special ,objects--,copernicus--,gassendi--,eudox us and ,aristotle--,triesnecker--,theophilus1 ,cyrillus1 and ,catharina--,thebit--,plato--,valley of the ,alps--,pico--,tycho--,wargentin--,arist archus and ,herodotus--,walter--,archimedes and the ,apennines ,,chapter ,,viii4 ,,on ,,lunar ,,craters4 #hi ,use of term ,crater for ,terrestrial and ,lunar ,formations--,truly ,volcanic ,nature of ,lunar ,craters--,terrestrial and ,lunar ,volcanic ,areas compared--,similarity--,difference only in ,magnitude--,central ,cone--,found in great and small ,lunar ,craters--,formative ,process of ,terrestrial ,volcanoes--,example from ,vesuvius--,vast ,size of ,lunar ,craters--,reasons assigned--,origin of ,moon's ,volcanic ,force--,aqueous ,vapour ,theory untenable--,expansion upon ,solidification ,theory--,formative ,process of a ,lunar ,crater--,volcanic ,vent--,commencement of ,eruption--,erection of ,rampart--,hollowing of ,crater--,formation of ,central ,cone--,of ,plateau--,various ,heights of ,plateaux--,coneless ,craters--,filled-up ,craters--,multiple ,cones--,craters on ,plateau--,double ,ramparts--,landslip ,terraces--,rutted ,ramparts--,overlapping and ,superposition of ,craters--,source-,connection of such--,froth-like ,aggregations of ,craters--,majestic ,dimensions of ,larger ,craters ,,chapter ,,ix4 ,,on ,,the ,,great ,,ring-,,formations ,,not ,,manifestly ,,volcanic4 #aag ,absence of ,central ,cones--,vast ,diameters--,difficult of ,explanation--,hooke's ,idea--,suggested ,cause of ,true ,circularity--,scrope's ,hypothesis of ,terrestrial ,tumescences--,rozet's ,tourbillonic ,theory--,dana's ,ebullition ,theory ,,chapter ,x4 ,,peaks ,,and ,,mountain ,,ranges4 #abd ,paucity of extensive ,mountain ,systems on ,moon--,contrast with ,earth--,lunar ,mountains found in less disturbed ,regions--,lunar ,apennines1 ,caucasus1 and ,alps--,valley of ,alps--8,crag and ,tail0 ,contour--,isolated ,peaks--,how produced--,analogy from ,freezing ,fountain--,terrestrial ,counterparts and their ,explanation by ,scrope--,blowing ,cone on ,teneriffe--,comparative ,gentleness of ,mountain-forming ,action--,relation between ,mountain ,systems and ,crater ,systems--,wrinkle ,ridges ,,chapter ,,xi4 ,,cracks ,,and ,,radiating ,,streaks4 #acc ,description--,divergence from ,focal ,craters--,experimental ,explanation of their ,cause--,radial ,cracking of ,crust--,outflow of ,matter therefrom--,analogy from 8,starred0 ,ice--,no ,shadows cast by ,streaks--,their probable ,slight ,elevation--,open ,cracks--,great ,numbers--,length--,depth--,in-fallen ,fragments--,shrinkage a ,cause of ,cracks--,lateness of their ,production ,,chapter ,,xii4 ,,colour ,,and ,,brightness ,,of ,,lunar ,,details3 ,,chronology ,,of ,,formations1 ,,and ,,finality ,,of ,,existing ,,features4 #adc ,absence of ,conspicuous ,colour--,slight ,tints of 8,seas0--,cause--,probable ,variety of ,tints in small ,patches--,diversity of ,brightness of ,details--,most ,conspicuous at ,full ,moon--,classification of ,shades--,exaggerated ,contrasts in ,photographs--,brightest ,portions probably the latest formed--,chronology of ,formations--,large ,craters older than ,small--,mountains older than ,craters--,bright ,streaks comparatively recent--,cracks most recent of all ,features--,question of existing ,change--,evidence from ,observation--,paucity of such ,evidence--,supposed ,case of ,linn--,theoretical ,discussion--,relative ,cooling ,tendencies of ,earth and ,moon--,earth nearly assumed its final ,condition--,moon probably cooled ,ages upon ,ages ago--,possible slight ,changes from ,solar ,heating--,disintegrating ,action ,,chapter ,,xiii4 ,,the ,,moon ,,as ,a ,,world3 ,,day ,,and ,,night ,,upon ,,its ,,surface4 #aee ,existence of ,habitants on other ,planets--,interest of the ,question--,conditions of ,life--,absence of these from ,moon--,no ,air or ,water and intense ,heat and ,cold--,possible ,existence of ,protogerms of ,life--,a ,day on the ,moon imagined--,instructiveness of the ,realization--,length of ,lunar ,day--,no ,dawn or ,twilight--,sudden ,appearance of ,light--,slowness of ,sun in ,rising--,no ,atmospheric ,tints--,blackness of ,sky and ,visibility of ,stars and fainter ,luminosities at ,noon-day--,appearance of the ,earth as a ,stationary ,moon--,its ,phases--,eclipse of ,sun by ,earth--,attendant ,phenomena--,lunar ,landscape--,height essential to secure a ,point of ,view--,sunrise on a ,crater--,desolation of ,scene--,no ,vestige of ,life--,colour of ,volcanic ,products--,no ,atmospheric ,perspective--,blackness of ,shadows--,impressions on other ,senses than ,sight--,heat of ,sun untempered--,intense ,cold in ,shade--,dead ,silence--,no ,medium to conduct ,sound--,lunar ,afternoon and ,sunset--,night--,the ,earth a ,moon--,its ,size1 ,rotation1 and ,features--,shadow of ,moon upon it--,lunar ,night-,sky--,constellations--,comets and ,planets--,no ,visible ,meteors--,bombardment by ,dark ,meteoric ,masses--,lunar ,landscape by ,night--,intensity of ,cold ,,chapter ,,xiv4 ,,the ,,moon ,,as ,a ,,satellite3 ,,its ,,relation ,,to ,,the ,,earth ,,and ,,man4 #aga ,the ,moon as a ,luminary--,secondary ,nature of ,light-giving ,function--,primary ,office as a ,sanitary ,agent--,cleansing ,effects of the ,tides--,tidal ,rivers and ,transport thereby--,the ,moon a 8,tug0--,available ,power of ,tides--,tide-,mills--,transfer of ,tidal ,power ,inland--,the ,moon as a ,navigator's ,guide--,longitude found by the ,moon--,moon's ,motions--,discovered by ,observations--,grouped into ,theories--,represented by ,tables--,the ,nautical ,almanac--,the ,moon as a ,long-,period ,timekeeper--,reckoning by 8,moons0--,eclipses the ,starting-,points of ,chronologies--,furnish indisputable ,dates--,solar ,surroundings revealed by ,eclipses when ,moon screens the ,sun--,solar ,corona--,moon as a ,medal of ,creation1 a ,half-formed ,world--,abuses of the ,moon--,superstitions--,erroneous ,ideas regarding ,moonlight pourtrayed by ,artists and ,authors--,the ,moon and the ,weather--,errors and ,facts--,atmospheric ,tides--,warmth from ,moon--,paradoxical ,effect in cooling the ,earth ,,chapter ,,xv4 ,,concluding ,,summary #ahd ,,list ,,of ,,plates4 ,,plate ,,page ,gassendi ,frontispiece ,i4--,summit of ,vesuvius #bf ,,ii4--,wrinkled ,hand and ,apple #cj ,,iii4--,full ,moon ,photograph #eb ,,iv4--,picture-,map of the ,moon ,to face each other4 ,v4--,skeleton ,map #fh ,,vi4--,terrestrial and ,lunar ,volcanic ,areas ,compared #hh ,,vii4--,progressive ,series of ,craters #ib ,,viii4--,copernicus #if ,,ix4--,the ,lunar ,apennines1 c41 c4 #ajj ,x4--,aristotle and ,eudoxus #ajd ,,xi4--,triesnecker #ajh ,,xii4--,theophilus1 ,cyrillus1 and ,catharina #aab ,,xiii4--,arzachael1 ,ptolemy1 and the ,railway #aaf ,,xiv4--,plato1 the ,valley of the ,alps1 ,pico1 c4 #abj ,,xv4--,mercator and ,campanus #abd ,,xvi4--,tycho and its ,surroundings #abh ,,xvii4--,wargentin #acb ,,xviii4--,aristarchus and ,herodotus #acf ,,xix4--,glass ,globe ,cracked by ,internal ,pressure #adj ,,xx4--,overlapping ,craters #adh ,,xxi4--,lunar ,crater4 ,ideal ,landscape #aef ,,xxii4--,solar ,eclipse as it would be seen from the ,moon #afd ,,xxiii4--,group of ,mountains4 ,ideal ,lunar ,landscape #agj ,,the ,,moon4 ,,chapter ,i4 ,,on ,,the ,,cosmical ,,origin ,,of ,,the ,,planets ,,of ,,the ,,solar ,,system4 ,in this ,chapter we propose to treat briefly of the probable formation of the various members of the solar system from matter which previously existed in space in a condition different from that in which we at present find it--i4e41 in the form of planets and satellites4 ,it is almost impossible to conceive that our world with its satellite1 and its fellow worlds with their satellites1 and also the great centre of them all1 have always1 from the commencement of time1 possessed their present form3 all our experiences of the working of natural laws rebel against such a supposition4 ,in every phenomenon of nature upon this earth--the great field from which we must glean our experiences and form our analogies--we see a constant succession of changes going on1 a constant progression from one stage of development to another taking place1 a perpetual mutation of form and nature of the same material substance occurring3 we see the seed transformed into the plant1 the flower into the fruit1 and the ovum into the animal4 ,in the inorganic world we witness the operation of the same principle2 but1 by reason of their slower rate of progression1 the changes there are manifested to us rather by their resulting effects than by their visible course of operation4 ,and when we consider1 as we are obliged to do1 that the same laws work in the greatest as well as the smallest processes of nature1 we are compelled to believe in an antecedent state of existence of the matter that composes the host of heavenly bodies1 and amongst them the earth and its attendant moon4 ,in the pursuit of this course of argument we are led to inquire whether there exists in the universe any matter from which planetary bodies could be formed1 and how far their formation from such matter can be explained by the operation of known material laws4 ,before the telescope revealed the hidden wonders of the skies1 and brought its rich fruits into our garner of knowledge concerning the nature of the universe1 the philosophic minds of some early astronomers1 ,kepler and ,tycho ,brahe to wit1 entertained the idea that the sun and the stars--the suns of distant systems--were formed by the condensation of celestial vapours into spherical bodies2 ,kepler basing his opinion on the phenomena of the sudden shining forth of new stars on the margin of the ,milky ,way4 ,but it was when the telescope pierced into the depths of celestial space1 and brought to light the host of those marvellous objects1 the nebul1 that the strongest evidence was afforded of the probable validity of these suppositions4 ,the mention of 8nebulous stars0 made by the earlier astronomers refers only to clusters of telescopic stars which the naked eye perceives as small patches of nebulous light2 and it does not appear that even the nebula in ,andromeda1 although so plainly discernible as to be often now-a-days mistaken by the uninitiated for a comet1 was known1 until it was discovered by means of a telescope1 in #afab1 by ,simon ,marius1 who described it as resembling a candle shining through semi-transparent horn1 as in a lantern1 and without any appearance of stars4 ,forty years after this date ,huygens discovered the splendid nebula in the sword handle of ,orion1 and in #affe another was detected by ,hevelius4 ,in #affg ,halley 7afterwards ,astronomer ,royal7 discovered a fourth2 a fifth was found by ,kirsch in #afha1 and a sixth by ,halley again in #agad4 ,half a century after this the labours of ,messier expanded the list of known nebul and clusters to #ajc1 a catalogue of which appeared in the 8,connaissance du ,temps0 7the ,french 8,nautical ,almanac07 for the years #aghc-aghd4 ,but this branch of celestial discovery achieved its most brilliant results when the rare penetration1 the indomitable perseverance1 and the powerful instruments of the elder ,herschel were brought to bear upon it4 ,in the year #aggi this great astronomer began to search after nebul with a seven-inch reflector1 which he subsequently superseded by the great one of forty feet focus and four feet aperture4 ,in #aghf he published his first catalogue of #ajjj nebul2 three years later he astonished the learned world by a second catalogue containing #ajjj more1 and in #ahjb a third came forth comprising other #ejj1 making #bejj in all6 ,this number has been so far increased by the labours of more recent astronomers that the last complete catalogue1 that of ,sir ,john ,herschel1 published a few years ago1 contains the places of #ejfc nebul and clusters4 ,at the earlier periods of ,herschel's observations1 that illustrious observer appears to have inclined to the belief that all nebul were but remote clusters of stars1 so distant1 so faint1 and so thickly agglomerated as to affect the eye only by their combined luminosity1 and at this period of the nebular history it was supposed that increased telescopic power would resolve them into their component stars4 ,but the familiarity which ,herschel gained with the phases of the multitudinous nebul that passed in review before his eyes1 led him ultimately to adopt the opinion1 advanced by previous philosophers1 that they were composed of some vapoury or elementary matter out of which1 by the process of condensation1 the heavenly bodies were formed2 and this led him to attempt a classification of the known nebul into a cosmical arrangement1 in which1 regarding a chaotic mass of vapoury matter as the primordial state of existence1 he arranged them into a series of stages of progressive development1 the individuals of one class being so nearly allied to those in the next that1 to use his own expression1 not so much difference existed between them 8as there would be in an annual description of the human figure were it given from the birth of a child till he comes to be a man in his prime40 7,philosophical ,transactions1 ,vol4 ,,ci41 pp4 #bga1 et seq47 ,his category comprises upwards of thirty classes or stages of progression1 the titles of a few of which we insert here to illustrate the completeness of his scheme4 ,class #a4 ,of extensive diffused nebulosity4 7,a table of #eb patches of such nebulosity actually observed is given1 some of which extend over an area of five or six square degrees1 and one of which occupies nine square degrees47 0 #f4 ,of milky nebulosity with condensation4 0 #ae4 ,of nebul that are of an irregular figure4 0 #ag4 ,of round nebul4 0 #bj4 ,of nebul that are gradually brighter in the middle4 0 #be4 ,of nebul that have a nucleus4 0 #bi4 ,of nebul that draw progressively towards a period of final condensation4 0 #cj4 ,of planetary nebul4 0 #cc4 ,of stellar nebul nearly approaching the appearance of stars4 ,in a walk through a forest we see trees in every stage of growth1 from the tiny sapling to the giant of the woods1 and no doubt can exist in our minds that the latter has sprung from the former4 ,we cannot at a passing glance discern the process of development actually going on2 to satisfy ourselves of this1 we must record the appearance of some single tree from time to time through a long series of years4 ,and what a walk through a forest is to an observer of the growth of a tree1 a lifetime is to the observer of changes in such objects as the nebul4 ,the transition from one state to another of the nebulous development is so slow that a lifetime is hardly sufficient to detect it4 ,nor can any precise evidence of change be obtained by the comparison of drawings or descriptions of nebul at various epochs1 with whatever care or skill such drawings be made1 for it will be admitted that no two draughtsmen will produce each a drawing of the most simple object from the same point of view1 in which every detail in the one will coincide exactly with every detail in the other4 ,there is abundant evidence of this in the existing representations of the great nebula in ,orion2 a comparison of the drawings that have been lately made of this object1 with the most perfect instruments and by the most skilful of astronomical draughtsmen1 reveals varieties of detail and even of general appearance such as could hardly be imagined to occur in similar delineations of one and the same subject2 and any one who himself makes a perfectly unbiassed drawing at the telescope will find upon comparison of it with others that it will offer many points of difference4 ,the fact is that the drawing of a man1 like his penmanship1 is a personal characteristic1 peculiar to himself1 and the drawings of two persons cannot be expected to coincide any more than their handwritings4 ,the appearance of a nebula varies also to a great extent with the power of the telescope used to observe it and the conditions under which it is observed2 the drawings of nebul made with the inferior telescopes of a century or two centuries ago1 the only ones that1 by comparison with those made in modern times1 could give satisfactory evidence of changes of form or detail1 are so rude and imperfect as to be useless for the purpose1 and it is reasonable to suppose that those made in the present day will be similarly useless a century or two hence4 ,since then we can obtain no evidence of the changes we must assume these mysterious objects to be undergoing1 ipso facto1 by observation of one nebula at various periods1 we must for the present accept the prim facie evidence offered 7as in the case of the trees in a forest7 by the observation of various nebul at one period4 8,the total dissimilitude10 says ,herschel at the close of the observations we have alluded to1 8between the appearance of a diffusion of the nebulous matter and of a star1 is so striking1 that an idea of the conversion of the one into the other can hardly occur to any one who has not before him the result of the critical examination of the nebulous system which has been displayed in this his paper4 ,the end ,i have had in view1 by arranging my observations in the order in which they have been placed1 has been to show that the above mentioned extremes may be connected by such nearly allied intermediate steps1 as will make it highly probable that every succeeding state of the nebulous matter is the result of the action of gravitation upon it while in a foregoing one1 and by such steps the successive condensation of it has been brought up to the planetary condition4 ,from this the transit to the stellar form1 it has been shown1 requires but a very small additional compression of the nebulous matter40 ,where the researches of ,herschel terminated those of ,laplace commenced4 ,herschel showed how a mass of nebulous matter so diffused as to be scarcely discernible might be and probably was1 by the mere action of gravitation1 condensed into a mass of comparatively small dimensions when viewed in relation to the immensity of its primordial condition4 ,laplace demonstrated how the known laws of gravitation could and probably did from such a partially condensed mass of matter produce an entire planetary system with all its subordinate satellites4 ,the first physicist who ventured to account for the formation of the various bodies of our solar system was ,buffon1 the celebrated ,french naturalist4 ,his theory1 which is fully detailed in his renowned work on natural history1 supposed that at some period of remote antiquity the sun existed without any attendant planets1 and that a comet having dashed obliquely against it1 ploughed up and drove off a portion of its body sufficient in bulk to form the various planets of our system4 ,he suggests that the matter thus carried off 8at first formed a torrent the grosser and less dense parts of which were driven the farthest1 and the densest parts1 having received only the like impulsion1 were not so remotely removed1 the force of the sun's attraction having retained them30 that 8the earth and planets therefore at the time of their quitting the sun were burning and in a state of liquefaction20 that 8by degrees they cooled1 and in this state of fluidity they took their form40 ,he goes on to say that the obliquity of the stroke of the comet might have been such as to separate from the bodies of the principal planets small portions of matter1 which would preserve the same direction of motion as the principal planets1 and thus would form their attendant satellites4 ,the hypothesis of ,buffon1 however1 is not sufficient to explain all the phenomena of the planetary system2 and it is imperfect1 inasmuch as it begins by assuming the sun to be already existing1 whereas any theory accounting for the primary formation of the solar system ought necessarily to include the origination of the most important body thereof1 the sun itself4 ,nevertheless1 it is but due to ,buffon to mention his ideas1 for the errors of one philosophy serve a most useful end by opening out fields of inquiry for subsequent and more fortunate speculators4 ,laplace1 dissatisfied with ,buffon's theory1 sought one more probable1 and thus was led to the proposition of the celebrated nebular hypothesis which bears his name1 and which1 in spite of its disbelievers1 has never been overthrown1 but remains the only probable1 and1 with our present knowledge1 the only possible explanation of the cosmical origin of the planets of our system4 ,although ,laplace puts forth his conjectures1 to use his own words1 8with the deference which ought to inspire everything that is not a result of observation and calculation10 yet the striking coincidence of all the planetary phenomena with the conditions of his system gives to those conjectures1 again to use his modest language1 8a probability strongly approaching certitude40 ,laplace conceived the sun to have been at one period the nucleus of a vast nebula1 the attenuated surrounding matter of which extended beyond what is now the orbit of the remotest planet of the system4 ,he supposed that this mass of matter in process of condensation possessed a rotatory motion round its centre of gravity1 and that the parts of it that were situated at the limits where centrifugal force exactly counterbalanced the attractive force of the nucleus were abandoned by the contracting mass1 and thus were formed successively a number of rings of matter concentric with and circulating around the central nucleus4 ,as it would be improbable that all the conditions necessary to preserve the stability of such rings of matter in their annular form could in all cases exist1 they would break up into masses which would be endued with a motion of rotation1 and would in consequence assume a spheroidal form4 ,these masses1 which hence constituted the various planets1 in their turn condensing1 after the manner of the parent mass1 and abandoning their outlying matter1 would become surrounded by similarly concentric rings1 which would break up and form the satellites surrounding the various planetary masses2 and1 as a remarkable exception to the rule of the instability of the rings and their consequent breakage1 ,laplace cited the case of ,saturn surrounded by his rings as the only instances of unbroken rings that the whole system offers us2 unless indeed we include the zodiacal light1 that cone of hazy luminosity that is frequently seen streaming from our luminary shortly before and after sunset1 and which ,laplace supposed to be formed of molecules of matter1 too volatile to unite either with themselves or with the planets1 and which must hence circulate about the sun in the form of a nebulous ring1 and with such an appearance as the zodiacal actually presents4 ,this hypothesis1 although it could not well be refuted1 has been by many hesitatingly received1 and for a reason which was at one time cogent4 ,in the earlier stages of nebular research it was clearly seen1 as we have previously remarked1 that many of the so-called nebul1 which appeared at first to consist of masses of vapoury matter1 became1 when scrutinised with telescopes of higher power1 resolved into clusters containing countless numbers of stars1 so small and so closely agglomerated1 that their united lustre only impressed the more feeble eye as a faint nebulosity2 and as it was found that each accession of telescopic power increased the numbers of nebul that were thus resolved1 it was thought that every nebula would at some period succumb to the greater penetration of more powerful instruments2 and if this were the case1 and if no real nebul were hence found to exist1 how1 it was argued1 could the nebular hypothesis be maintained8 ,one of the most important nebul bearing upon this question was the great one in the sword handle of ,orion1 one of the grandest and most conspicuous in the whole heavens4 ,on account of the brightness of some portions of this object1 it seemed as though it ought to be readily resolvable1 supposing all nebul to consist of stars1 but all attempts to resolve it were in vain1 even with the powerful telescopes of ,sir ,john ,herschel and the clear zenithal sky of the ,cape of ,good ,hope4 ,at length the question was thought to be settled1 for upon the completion of ,lord ,rosse's giant reflector1 and upon examination of the nebula with it1 his lordship stated that there could be little1 if any1 doubt as to its resolvability1 and then it was maintained1 by the disbelievers in the nebular theory1 that the last stronghold of that theory had been broken down4 ,but the truths of nature are for ever playing at hide and seek with those who follow them3--the dogmas of one era are the exploded errors of the next4 ,within the past few years a new science has arisen that furnishes us with fresh powers of penetration into the vast and secret laboratories of the universe2 a new eye1 so to speak1 has been given us by which we may discern1 by the mere light that emanates from a celestial body1 something of the chemical elements of which it is composed4 ,when ,newton two hundred years ago toyed with the prism he bought at ,stourbridge fair1 and projected its pretty rainbow tints upon the wall1 his great mind little suspected that that phantom riband of gorgeous colours would one day be called upon to give evidence upon the probable cosmical origin of worlds4 ,yet such in truth has been the case4 ,every substance when rendered luminous gives off light of some colour or degree of refrangibility peculiar to itself1 and although the eye cannot detect any difference between one character of light and another1 the prism gives the means of ascertaining the quality and degree of refrangibility of the light emanating from any source however distant1 and hence of gaining some knowledge of the nature of that source4 ,if1 for instance1 a ray of light from a solid body in combustion is passed through a prism1 a spectrum is produced which exhibits light of all colours or all degrees of refrangibility2 if the light from such a body1 before passing through the prism1 be made to pass through gases or certain metallic vapours1 the resulting spectrum is found to be crossed transversely by numbers of fine dark lines1 apparently separating the various colours1 or cutting the spectrum into bands4 ,the solar spectrum is of this class2 the once mysterious lines first observed by ,wollaston1 and subsequently by ,fraunhoffer1 and known as 8,fraunhoffer's lines10 have now been interpreted1 chiefly by the sagacious ,german chemist ,kirchoff1 and identified as the effects of absorption of certain of the sun's rays by chemical vapours contained in his atmosphere4 ,the fixed stars yield spectra of the same character1 but varying considerably in feature1 the lines crossing the stellar spectra differing in position and number from those of the sun1 and one star from another1 proving the stars to possess varied chemical constitutions4 ,but there is another class of spectra1 exhibited when light from other sources is passed through the prism4 ,these consist1 not of a luminous riband of light like the solar spectrum1 but of bright isolated lines of coloured light with comparatively wide dark spaces separating them4 ,such spectra are yielded only by the light emitted from luminous gases and metals or chemical elements in the condition of incandescent vapour4 ,every gas or element in the state of luminous vapour yields a spectrum peculiar to itself1 and no two elements when vapourized before the prism show the same combinations of luminous lines4 ,now in the course of some observations upon the spectra of the fixed stars by ,dr4 ,huggins1 it occurred to that gentleman to turn his telescope1 armed with a spectroscope1 upon some of the brighter of the nebul1 and great was his surprise to find that instead of yielding continuous spectra1 as they must have done had their light been made up of that of a multitude of stars1 they gave spectra containing only two or three isolated bright lines2 such a spectrum could only be produced by some luminous gas or vapour1 and of this form of matter we are now justified in declaring1 upon the strength of numerous modern observations1 these remarkable bodies are composed2 and it is a curious and interesting fact that some of the nebul styled resolvable1 from the fact of their exhibiting points of light like stars1 yield these gaseous spectra1 whence ,dr4 ,huggins concludes that the brighter points taken for stars are in reality nuclei of greater condensation of the nebular matter3 and so the fact of the apparent resolvability of a nebula affords no positive proof of its non-nebulous character4 ,these observations--which have been fully confirmed by ,father ,secchi of the ,roman ,college--by destroying the evidence in favour of nebul being remote clusters1 add another attestation to the probability of the truth of the nebular hypothesis1 and we have now the confutation of the luminologist to add to that of the astronomers who1 in the person of the illustrious ,arago1 asserted that the ideas of the great author of the 8,mcanique ,cleste0 8were those only which by their grandeur1 their coherence1 and their mathematical character could be truly considered as forming a physical cosmogony40 ,confining1 then1 our attention to the single object of the universe it is our task to treat of--the ,moon--and without asserting as an indisputable fact that which we can never hope to know otherwise than by inference and analogy1 we may assume that that body once existed in the form of a vast mass of diffused or attenuated matter1 and that1 by the action of gravitation upon the particles of that matter1 it was condensed into a comparatively small and compact planetary body4 ,but while the process of condensation or compaction was going on1 another important law of nature--but recently unfolded to our knowledge--was in powerful operation1 the discussion of which law we reserve for a separate ,chapter4 ,,chapter ,,ii4 ,,the ,,generation ,,of ,,cosmical ,,heat4 ,in the preceding ,chapter we endeavoured to show how the action of gravitation upon the particles of diffused primordial matter would result in the formation1 by condensation and aggregation1 of a spherical planetary body4 ,we have now to consider another result of the gravitating action1 and for this we must call to our aid a branch of scientific enquiry and investigation unrecognized as such at the period of ,laplace's speculations1 and which has been developed almost entirely within the past quarter of a century4 ,the 8great philosophical doctrine of the present era of science10 as the subject about to engage our attention has been justly termed1 bears the title of the 8,conservation of ,force10 or--as some ambiguity is likely to attend the definition of the term 8,force0--the 8,conservation of ,energy40 ,the basis of the doctrine is the broad and comprehensive natural law which teaches us that the quantity of force comprised by the universe1 like the quantity of matter contained in it1 is a fixed and invariable amount1 which can be neither added to nor taken from1 but which is for ever undergoing change and transformation from one form to another4 ,that we cannot create force ought to be as obvious a fact as that we cannot create matter2 and what we cannot create we cannot destroy4 ,as in the universe we see no new matter created1 but the same matter constantly disappearing from one form and reappearing in another1 so we can find no new force ever coming into action--no description of force that is not to be referred to some previous manner of existence4 ,without entering upon a metaphysical discussion of the term 8force10 it will be sufficient for our purpose to consider it as something which produces or resists motion1 and hence we may argue that the ultimate effect of force is motion4 ,the force of gravity on the earth results in the motion or tendency of all bodies towards its centre1 and1 similarly1 the action of gravitation upon the atoms or particles of a primeval planet resulted in the motion of those particles towards each other4 ,we cannot conceive force otherwise than by its effects1 or the motion it produces4 ,and force we are taught is indestructible2 therefore motion must be indestructible also4 ,but when a falling body strikes the earth1 or a gunshot strikes its target1 or a hammer delivers a blow upon an anvil1 or a brake is pressed against a rotating wheel1 motion is arrested1 and it would seem natural to infer that it is destroyed4 ,but if we say it is indestructible1 what becomes of it8 ,the philosophical answer to the question is this--that the motion of the mass becomes transferred to the particles or molecules composing it1 and transformed to molecular motion1 and this molecular motion manifests itself to us as heat4 ,the particles or atoms of matter are held together by cohesion1 or1 in other words1 by the action of molecular attraction4 ,when heat is applied to these particles1 motion is set up among them1 they are set in vibration1 and thus1 requiring and making wider room1 they urge each other apart1 and the well-known expansion by heat is the result4 ,if the heat be further continued a more violent molecular motion ensues1 every increase of heat tending to urge the atoms further apart1 till at length they overcome their cohesive attraction and move about each other1 and a liquid or molten condition results4 ,if the heat be still further increased1 the atoms break away from their cohesive fetters altogether and leap off the mass in the form of vapour1 and the matter thus assumes the gaseous or vaporous form4 ,thus we see that the phenomena of heat are phenomena of motion1 and of motion only4 ,this mutual relation between heat and work presented itself as an embryo idea to the minds of several of the earlier philosophers1 by whom it was maintained in opposition to the material theory which held heat to be a kind of matter or subtle fluid stored up in the inter-atomic spaces of all bodies1 capable of being separated and procured from them by rubbing them together1 but not generated thereby4 ,bacon1 in his 8,novum ,organum10 says that 8heat itself1 its essence and quiddity1 is motion and nothing else40 ,locke defines heat as 8a very brisk agitation of the insensible parts of an object1 which produces in us that sensation from whence we denominate the object hot2 so what in our sensation is heat1 in the object is nothing but motion40 ,descartes and his followers upheld a similar opinion4 ,richard ,boyle1 two hundred years ago1 actually wrote a treatise entitled 8,the ,mechanical ,theory of ,heat and ,cold10 and the ingenious ,count ,rumford made some highly interesting and significant experiments on the subject1 which are described in a paper read before the ,royal ,society in #agih1 entitled 8,an ,inquiry concerning the ,source of ,heat excited by ,friction40 ,but the conceptions of these authors remained isolated and unfruitful for more than a century1 and might have passed1 meantime1 into the oblivion of barren speculation1 but for the impulse which this branch of inquiry has lately received4 ,now1 however1 they stand forth as notable instances of truth trying to force itself into recognition while yet men's minds were unprepared or disinclined to receive it4 ,the key to the beautiful mechanical theory of heat was found by these searching minds1 but the unclasping of the lock that should disclose its beauty and value was reserved for the philosophers of the present age4 ,simultaneously and independently1 and without even the knowledge of each other1 three men1 far removed from probable intercourse1 conceived the same ideas and worked out nearly similar results concerning the mechanical theory of heat4 ,seeing that motion was convertible into heat1 and heat into motion1 it became of the utmost importance to determine the exact relation that existed between the two elements4 ,the first who raised the idea to philosophic clearness was ,dr4 ,julius ,robert ,mayer1 a physician of ,heilbronn in ,germany4 ,in certain observations connected with his medical practice it occurred to him that there must be a necessary equivalent between work and heat1 a necessary numerical relation between them4 8,the variations of the difference of colour of arterial and venous blood directed his attention to the theory of respiration4 ,he soon saw in the respiration of animals the origin of their motive powers1 and the comparison of animals to thermic machines afterwards suggested to him the important principle with which his name will remain for ever connected40 ,next in order of publication of his results stands the name of ,colding1 a ,danish engineer1 who about the year #ahdc presented a series of memoirs on the steam engine to the ,royal ,society of ,copenhagen1 in which he put forth views almost identical with those of ,mayer4 ,last in publication order1 but foremost in the importance of his experimental treatment of the subject1 was our own countryman1 ,dr4 ,joule of ,manchester4 8,entirely independent of ,mayer1 with his mind firmly fixed upon a principle1 and undismayed by the coolness with which his first labours appear to have been received1 he persisted for years in his attempts to prove the invariability of the relation which subsists between heat and ordinary mechanical power40 7,we are quoting from ,professor ,tyndall's valuable work on 8,heat considered as a ,mode of ,motion407 8,he placed water in a suitable vessel1 agitated the water by paddles1 and determined both the amount of heat developed by the stirring of the liquid and the amount of labour expended in its production4 ,he did the same with mercury and sperm oil4 ,he also caused discs of cast iron to rub against each other1 and measured the heat produced by their friction1 and the force expended in overcoming it4 ,he urged water through capillary tubes1 and determined the amount of heat generated by the friction of the liquid against the sides of the tubes4 ,and the results of his experiments leave no shadow of doubt upon the mind that1 under all circumstances1 the quantity of heat generated by the same amount of force is fixed and invariable4 ,a given amount of force1 in causing the iron discs to rotate against each other1 produced precisely the same amount of heat as when it was applied to agitate water1 mercury1 or sperm oil4 99 99 99 99 ,the absolute amount of heat generated by the same expenditure of power1 was in all cases the same40 8,in this way it was found that the quantity of heat which would raise one pound of water one degree ,fahrenheit in temperature1 is exactly equal to what would be generated if a pound weight1 after having fallen through a height of #ggb feet1 had its moving force destroyed by collision with the earth4 ,conversely1 the amount of heat necessary to raise a pound of water one degree in temperature1 would1 if all applied mechanically1 be competent to raise a pound weight #ggb feet high1 or it would raise #ggb pounds one foot high4 ,the term #8foot pounds' has been introduced to express in a convenient way the lifting of one pound to the height of a foot4 ,thus the quantity of heat necessary to raise the temperature of a pound of water one degree ,fahrenheit being taken as a standard1 #ggb foot-pounds constitute what is called the mechanical equivalent of heat40 ,by a process entirely different1 and by an independent course of reasoning1 ,mayer had1 a few months previous to ,joule1 determined this equivalent to be #ggad foot-pounds4 ,such a remarkable coincidence arrived at by pursuing different routes gives this value a strong claim to accuracy1 and raises the ,mechanical ,theory of ,heat to the dignity of an exact science1 and its enunciators to the foremost place in the ranks of physical philosophers4 ,in linking together the labours of the two remarkable men above alluded to1 ,prof4 ,tyndall remarks1 that 8,mayer's labours have in some measure the stamp of profound intuition1 which rose however to the energy of undoubting conviction in the author's mind4 ,joule's labours1 on the contrary1 are an experimental demonstration4 ,mayer thought his theory out1 and rose to its grandest applications4 ,joule worked his theory out1 and gave it the solidity of natural truth4 ,true to the speculative instinct of his country1 ,mayer drew large and mighty conclusions from slender premises2 while the ,englishman aimed above all things at the firm establishment of facts4444 ,to each belongs a reputation which will not quickly fade1 for the share he has had1 not only in establishing the dynamical theory of heat1 but also in leading the way towards a right appreciation of the general energies of the universe40 ,but from these generalities we must pass to the application of the mechanical theory of heat to our special subject4 ,we have learnt that every form of motion is convertible into heat4 ,we know that the falling meteor or shooting star1 whose motion is impeded by friction against the earth's atmosphere1 is heated thereby to a temperature of incandescence4 ,let us then suppose that myriads of such cosmical particles came into collision from the effect of their mutual attraction1 or that the component atoms of a vast nebulous mass violently converged under the like influence4 ,what would follow8 ,obviously the generation of an intense heat by the arrest of converging motion1 such a heat as would result in the fusion of the whole into one mass4 ,mayer1 in one of his most remarkable papers 78,celestial ,dynamics07 remarks that the 8,newtonian theory of gravitation1 whilst it enables us to determine1 from its present form1 the earth's state of aggregation in ages past1 at the same time points out to us a source of heat powerful enough to produce such a state of aggregation--powerful enough to melt worlds3 it teaches us to consider the molten state of a planet as the result of the mechanical union of cosmical masses1 and to derive the radiation of the sun and the heat in the bowels of the earth from a common origin40 ,and the same laws that governed the formation of the earth1 governed also the formation of the moon3 the variations of ,nature's operations are quantitative only and not qualitative4 ,the ,divine ,will that made the earth made the moon also1 and the means and mode of working were the same for both4 ,the geological phenomena of the earth afford unmistakeable evidence of its original fluid or molten condition1 and the appearance of the moon is as unmistakeably that of a body once in an igneous or molten state4 ,the enigma of the earth's primary formation is solved by the application of the dynamical theory of heat4 ,by this theory the generation of cosmical heat is removed from the quicksands of conjecture and established upon the firm ground of direct calculation3 for the absolute amount of heat generated by the collision of a given amount of matter is 7of course1 with some little uncertainty7 deducible from a mathematical formula4 ,mayer has computed the amount of heat that the matter of the earth would have generated1 if it had been formed originally of only two parts drawn into collision by their mutual attraction1 and has found that it would be from #j to #cb1jjj or #dg1jjja ,centigrade degrees1 according as one part was infinitely small as compared with the other1 or as the two parts were of equal size4 ,professor ,helmholtz1 another labourer in the same field of science1 has computed the amount of heat generated by the condensation of the whole of the matter composing the solar system3 this he finds would be equivalent to the heat that would be required to raise the temperature of a mass of water equal to the sum of the masses of all the bodies of the system to #bh1jjj1jjj 7twenty-eight million7 degrees of the ,centigrade scale4 ,these examples afford abundant evidence of sufficient heat having been generated by the aggregation of the matter of the moon to reduce it to a state of fusion1 and so to produce1 from a nebulous chaos of diffused cosmical matter1 a molten body of definite outline and size4 ,it is requisite here to remark that fusion does not necessarily imply combustion4 ,it has been frequently asked1 ,how can a volcanic theory of the lunar phenomena be upheld consistently with the condition that it possesses no atmosphere to support ,fire8 ,to this we would reply that to produce a state of incandescence or a molten condition it is not necessary that the body be surrounded by an atmosphere4 ,the intensely rapid motion of the particles of matter of bodies1 which the dynamical theory shows to be the origin of the molten state1 exists quite independently of such external matter as an atmosphere4 ,the complex mixture of gases and vapours which we term 8air10 has nothing whatever to do with the fusion of substances1 whatever it may have to do with their combustion4 ,combustion is a chemical phenomenon1 due to the combination of the oxygen of that air with the heated particles of the combustible matter3 oxygen is the sole supporter of combustion1 and hence combustion is to be regarded rather as a phenomenon of oxygen than as a phenomenon of the matter with which that oxygen combines4 ,the greatest intensity of heat may exist without oxygen1 and consequently without combustion4 ,in support of this argument it will be sufficient to adduce1 upon the authority of ,dr4 ,tyndall1 the fact that a platinum wire can be raised to a luminous temperature and actually fused in a perfect vacuum4 ,but while the mass of condensing cosmical matter was thus accumulating and forming the globe of the moon1 the heat consequent upon the aggregation of its particles was suffering some diminution from the effect of radiation4 ,so long as the radiated heat lost fell short of the dynamical heat generated1 no effect of cooling would be manifest2 but when the vis viva of the condensing matter was all converted into its equivalent of heat1 or when the accession of heat fell short of that radiated1 a necessary cooling must ensue1 and this cooling would be accompanied by a solidification of that part of the mass which was most free to radiate its heat into surrounding space3 that part would obviously be the outer surface4 ,with the solidification of this external crust began the 8year one0 of selenological history4 ,the phenomena attendant upon the cooling of the mass we will consider in the next ,chapter4 ,,chapter ,,iii4 ,,the ,,subsequent ,,cooling ,,of ,,the ,,igneous ,,body4 ,in the foregoing ,chapters we have endeavoured to show1 by the light of modern science1 first1 how diffused cosmical matter was probably condensed into a planetary mass by the mutual gravitation of its particles1 and secondly1 how1 the after destruction of the gravitative force1 by the collision of the converging particles of matter1 resulted in the generation of such sufficient heat as to reduce the whole mass to a molten condition4 ,our present task is to consider the subsequent cooling of the mass1 and the phenomena attendant upon or resulting therefrom4 ,this brief ,chapter is important to our subject1 as we shall have frequent occasion to refer to the leading principle we shall endeavour to illustrate in it1 in subsequently treating of the causes to which the special selenological features are to be attributed4 ,first1 then1 as regards the cooling of the igneous mass that constituted the moon at the inconceivably remote period when possibly that body was really a 8lesser light0 shining with a luminosity of its own1 due to its then incandescent state1 and not simply a reflector1 as it is now1 of light which it receives from the sun4 ,if we could conceive it possible that the igneous mass in the act of cooling parted with its heat from the central part first and so began to solidify from its centre1 or if it had been possible for the mass to have cooled uniformly and simultaneously throughout its whole depth1 or that each substratum had cooled before its superstratum1 we should have had a moon whose surface would have been smooth and without any such remarkable asperities and excresences as are now presented to our view4 ,but these suppositions are inadmissible3 on the contrary we are compelled to consider that the portion of the igneous or molten body that first cooled was its exterior surface1 which1 radiating its heat into surrounding space1 became solid and comparatively cool while the interior retained its hot and molten condition4 ,so that at this early stage of the moon's history it existed in the form of a solid shell inclosing a molten interior4 ,now at this period of its formation1 the moon's mass1 partly cooled and solidified and partly molten1 would be subject to the influence of two powerful molecular forces3 the first of these would consist in the diminution of bulk or contraction of volume which accompanies the cooling of solidified masses of previously molten substances2 the second would arise from a phenomenon which we may here observe is by no means so generally known as from its importance it deserves to be3 and as we shall have frequent occasion to refer to it as one of the chief agencies in producing the peculiar structural characteristics of the moon's surface1 it may be well here to give a few examples of its action1 that our reference to it hereafter may be more clearly understood4 ,the broad general principle of the phenomenon here referred to is this3--that fusible substances are 7with a few exceptions7 specifically heavier while in their molten condition than in the solidified state1 or in other words1 that molten matter occupies less space1 weight for weight1 than the same matter after it has passed from the melted to the solid condition4 ,it follows as an obvious corollary that such substances contract in bulk in fusing or melting1 and expand in becoming solid4 ,it is this expansion upon solidification that now concerns us4 ,water1 as is well known1 increases in density as it cools1 till it reaches the temperature of #ci ,fahrenheit1 after which1 upon a further decrease of temperature1 its density begins to decrease1 or in other words its bulk expands1 and hence the well-known fact of ice floating in water1 and the inconvenient fact of water-pipes bursting in a frost4 ,this action in water is of the utmost importance in the grand economy of nature1 and it has been accepted as a marvellous exception to the general law of substances increasing in density 7or shrinking7 as they decrease in temperature4 ,water is1 however1 by no means the exceptional substance that it has been so generally considered4 ,it is a fact perfectly familiar to iron-founders1 that when a mass of solid cast-iron is dropped into a pot of molten iron of identical quality1 the solid is found to float persistently upon the molten metal--so persistently that when it is intentionally thrust to the bottom of the pot1 it rises again the moment the submerging agency is withdrawn4 ,as regards the amount of buoyancy we believe it may be stated in round numbers to be at least two or three per cent4 ,it has been suggested by some who are familiar with this phenomenon that the solid mass may be kept up by a spurious buoyancy imparted to it by a film of adhering air1 or that surface impurities upon the solid metal may tend to reduce the specific gravity of the mass and thereby prevent it sinking1 and that the fact of floatation is not absolutely a proof of greater specific lightness4 ,but in controversion of these suggestions1 we can state as the result of experiment that pieces of cast-iron which have had their surface roughness entirely removed1 leaving the bright metal exposed1 still float on the molten metal1 and further that when1 under the influence of the great heat of the molten mass1 the solid is gradually melted away1 and consequently any possible surface impurities or adhering air must necessarily have been removed1 the remaining portion continues to float to the last4 ,the inevitable inference from this is that in the case of cast-iron the solid is specifically lighter than the molten1 and1 therefore1 that in passing from the molten to the solid condition this substance undergoes expansion in bulk4 ,we are able to offer a confirmation of this inference in the case of cast-iron by a remarkable phenomenon well known to iron-founders1 but of which we have never met with special notice4 ,when a ladle or pot of molten iron is drawn from the melting furnace and allowed to stand at rest1 the surface presents a most remarkable and suggestive appearance4 ,instead of remaining calm and smooth it is the scene of a lively commotion3 the thin coat of scoria or molten oxide which forms on the otherwise bright surface of the metal is seen1 as fast as it forms at the circumference of the pot1 to be swept by active convergent currents towards the centre1 where it accumulates in a patch4 ,while this action is proceeding1 the entire upper surface of the metal appears as if it were covered with animated vermicules of scoria1 springing into existence at the circumference of the pot1 and from thence rapidly streaming and wriggling themselves towards the centre4 ,illustration3 ,fig4 #a4 ,our illustration 7,fig4 #a7 is intended1 so far as such means can do so1 to convey some idea of this remarkable appearance at one instant of its continued occurrence4 ,to interpret our illustration rightly it is necessary to imagine this vermicular freckling to be constantly and rapidly streaming from all points of the periphery of the pot towards the centre1 where1 as we have said1 it accumulates in the form of a floating island4 ,we may observe that the motion is most rapid when the hot metal is first put into the cool ladle3 as the fluid metal parts with some of its heat and the ladle gets hot by absorbing it1 this remarkable surface disturbance becomes less energetic4 ,now if we carefully consider this peculiar action and seek a cause for the phenomenon1 we shall be led to the conclusion that it arises from the expansion of that portion of the molten mass which is in contact with or close proximity to the comparatively cool sides of the ladle1 which sides act as the chief agent in dispersing the heat of the melted metal4 ,the motion of the scoria betrays that of the fluid metal beneath1 and careful observation will show that the motion in question is the result of an upward current of the metal around the circumference of the ladle1 as indicated by the arrows ,a1 ,b1 ,c in the accompanying sectional drawing of the ladle 7,fig4 #b74 ,the upward current of the metal can actually be seen when specially looked for1 at the rim of the pot1 where it is deflected into the convergent horizontal direction and where it presents an elevatory appearance as shown in the figure4 ,it is difficult to assign to this effect any other cause than that of an expansion and consequent reduction of the specific gravity of the fluid metal in contact with or in close proximity to the cooler sides of the pot1 as1 according to the generally entertained idea that contraction universally accompanies cooling1 it would be impossible for the cooler to float on the hotter metal1 and the curious surface-currents above referred to would be in contrary direction to that which they invariably take1 i4e41 they would diverge from the centre instead of converging to it4 ,the external arrows in the figure represent the radiation of the heat from the outer sides of the pot1 which is the chief cause of cooling4 ,illustration3 ,fig4 #b4 ,turning from cast-iron to other metals we find further manifestations of this expansive solidification4 ,bismuth is a notable example4 ,in his lectures on ,heat1 ,dr4 ,tyndall exhibited an experiment in which a stout iron bottle was filled with molten bismuth1 and the stopper tightly closed4 ,the whole was set aside to cool1 and as the metal within approached consolidation the bottle was rent open by its expansion1 just as would have been the case had the bottle been filled with water and exposed to freezing temperature4 ,mercury affords another example4 ,thermometers which have to be exposed to ,arctic temperatures are generally filled with spirit instead of quicksilver1 because the latter has been found to burst the bulbs when the cold reached the congealing point of the metal1 the bursting being a consequence of the expansion which accompanies the act of congelation4 ,silver also expands in passing from the fluid to the solid state1 for we are informed by a practical refiner that solid floats on molten silver as ice floats on water2 it also1 as likewise do gold and copper1 exhibits surface converging currents in the melting-pot like those depicted above for molten iron4 ,it may1 however1 be objected that metals are too distantly related to volcanic substances to justify inferences being drawn from their behaviour in explanation of volcanic phenomena4 ,with a view therefore of testing the question at issue with a substance admitted as closely allied to volcanic material1 we appealed to the furnace slag of iron-works4 ,the following are extracts from the letters of an iron manufacturer of great experience#b to whom we referred the question3-- 8,i beg to inform you that cold slag floats in molten slag in the same way cold iron floats in molten iron4 8,i filled a box with hot molten slag run quickly from a blast furnace2 the box was about #e feet square by #b feet deep1 and ,i dropped into the slag a piece of cold slag weighing #af lbs41 when it came to the top in a second4 ,i pushed it down to the bottom several times and it always made its appearance at the top3 indeed a small portion of it remained above the molten slag40 ,illustration3 ,fig4 #c4 ,here then we have a substance closely allied to volcanic material which manifests the expansile principle in question2 but we may go still further and give evidence from the very fountain-head by instancing what appears to be a most cogent example of its operation which we observed on the occasion of a visit to the crater of ,vesuvius in #ahfe while a modified eruption was in progress4 ,on this occasion we observed white-hot lava streaming down from apertures in the sides of a central cone within the crater and forming a lake of molten lava on the plateau or bottom of the crater2 on the surface of this molten lake vast cakes of the same lava which had become solidified were floating1 exactly in the same manner as ice floats in water4 ,the solidified lava had cracked1 and divided into cakes1 in consequence of its contraction and also of the uprising of the accumulating fluid lava on which it floated1 more and more space being thus afforded for it to separate1 on account of the crater widening upwards1 while through the joints or fissures the fluid lava could be seen beneath4 ,but for the decrease in density and consequent expansion in volume which accompanied solidification1 this floating of the solidified lava on the molten could not have occurred4 ,reference to ,fig4 #c1 which represents a section of the crater of ,vesuvius on the occasion above referred to1 will perhaps assist the reader to a more clear idea of what we have endeavoured to describe4 ,a ,a are the streams of white-hot lava issuing from openings in the sides of the central cone1 and accumulating beneath the solidified crust ,b ,b in a lake of molten lava at ,c ,c2 the solidified crust ,b ,b as it was floated upwards dividing into separate cakes as represented in ,fig4 #d4 7,see also ,plate ,i47 ,illustration3 ,fig4 #d4 ,illustration3 ,,plate ,i4 ,,crater ,,of ,,vesuvius4 #ahfe4 ,let us now consider what would be the effect produced upon a spherical mass of molten matter in progress of cooling1 first under the action of the above described expansion which precedes solidification1 and then by the contraction which accompanies the cooling of a solidified body4 ,the first portion of such a mass to part with its heat being its external surface1 this portion would expand1 but there being no obstacle to resist the expansion there would be no other result than a temporary slight enlargement of the sphere4 ,this external portion would on cooling form a solid shell encompassing a more or less fluid molten nucleus1 but as this interior has in its turn1 on approaching the point of solidification1 to expand also1 and there being1 so to speak1 no room for its expansion1 by reason of its confinement within its solid casing1 what would be the consequence8--the shell would be rent or burst open1 and a portion of the molten interior ejected with more or less violence according to circumstances1 and many of the characteristic features of volcanic action would be thus produced3 the thickness of the outer shell1 the size of the vent made by the expanding matter for its escape1 and other conditions conspiring to modify the nature and extent of the eruption4 ,thus there would result vast floodings of the exterior surface of the shell by the so extruded molten matter1 volcanoes1 extruded mountains1 and other manifestations of eruptive phenomena4 ,the sectional diagram 7,fig4 #e7 will help to convey a clear idea of this action4 ,basing our reasoning on the principle we have thus enunciated1 namely1 that molten telluric matter expands on nearing the point of solidification1 and which we have endeavoured to illustrate by reference to actual examples of its operation1 we consider we are justified in assuming that such a course of volcanic phenomena has very probably occurred again and again upon the moon2 that this expansion of volume which accompanies the solidification of molten matter furnishes a key to the solution of the enigma of volcanic action2 and that such theories as depend upon the agency of gases1 vapour1 or water are at all events untenable with regard to the moon1 where no gases1 vapour1 or water1 appear to exist4 ,illustration3 ,fig4 #e4 ,a ,a4 ,the solidified crust cooling1 contracting1 and cracking2 the cracking action enhanced by the expansion of the substratum of molten matter1 ,b ,b ,b1 which1 expanding as it approaches the point of solidification1 injects portions of the molten matter up through the contractile cracks1 and results in producing craters1 mountains of exudation1 and districts flooded with extruded lava1 ,c ,c ,c4 ,the nucleus of intensely hot molten matter4 ,that an upheaving and ejective force has been in action with varying intensity beneath the whole of the lunar surface is manifest from the aspect of its structural details1 and we are impressed with the conviction that the principle we have set forth1 namely the paroxysms of expansion which successively occurred as portions of its molten interior approached solidification1 supply us with a rational cause to which such vast ejective and upheaving phenomena may be assigned4 ,many features of terrestrial geology likewise require such an expansive force whereby to explain them2 we therefore venture to recommend this source and cause of ejective action to the careful consideration of geologists4 ,illustration3 ,fig4 #f4 ,illustration3 ,fig4 #g4 ,when the molten substratum had burst its confines1 ejected its superfluous matter1 and produced the resulting volcanic features1 it would1 after final solidification1 resume the normal process of contraction upon cooling1 and so retreat or shrink away from the external shell4 ,let us now consider what would be the result of this4 ,evidently the external shell or crust would become relatively too large to remain at all points in close contact with the subjacent matter4 ,the consequence of too large a solid shell having to accommodate itself to a shrunken body underneath1 is that the skin1 so to term the outer stratum of solid matter1 becomes shrivelled up into alternate ridges and depressions1 or wrinkles4 ,in its attempt to crush down and follow the contracting substratum1 it would have to displace the superabundant or superfluous material of its former larger surface by thrusting it 7by the action of tangential force7 into undulating ridges as in ,fig4 #f1 or broken elevated ridges as in ,fig4 #g1 or overlappings of the outer crust as in ,fig4 #h1 or ridges capped by more or less fluid molten matter extruded from beneath1 as indicated in ,fig4 #i1 a class of action which might occur contemporaneously with the elevation of the ridge or subsequently to its formation4 ,illustration3 ,fig4 #h4 ,illustration3 ,fig4 #i4 ,a long-kept shrivelled apple affords an apt illustration of this wrinkle theory2 another example may be observed in the human face and hand1 when age has caused the flesh to shrink and so leave the comparatively unshrinking skin relatively too large as a covering for it4 ,we illustrate both of these examples by actual photographs of the respective objects1 which are reproduced on ,plate ,,ii4 ,whenever an outer covering has to accommodate and apply itself to an interior body that has become too small for it1 wrinkles are inevitably produced4 ,the same action that shrivels the human skin into creases and wrinkles1 has also shrivelled certain regions of the igneous crust of the earth4 ,a map of a mountainous part of our globe affords abundant evidence of such a cause having been in action2 such maps are pictures of wrinkles4 ,several parts of the lunar surface1 as we shall by-and-by see1 present us with the same appearances in a modified degree4 ,to the few primary causes we have set forth in this chapter--to the alternate expansion and contraction of successive strata of the lunar sphere1 when in a state of transition from an igneous and molten to a cooled and solidified condition1 we believe we shall be able to refer well nigh all the remarkable and characteristic features of the lunar surface which will come under our notice in the course of our survey4 ,illustration3 ,,plate ,,ii4 ,,back of ,,hand ,,shrivelled ,,apple4 ,,to ,,illustrate the ,,origin of ,,certain ,,mountain ,,ranges ,,by ,,shrinkage of the ,,globe4 ,,chapter ,,iv4 ,,the ,,form1 ,,magnitude1 ,,weight1 ,,and ,,density ,,of ,,the ,,lunar ,,globe4 ,we have not hitherto had occasion to refer to what we may term the physical elements of the moon3 by which we mean the various data concerning form1 size1 weight1 density1 c4 of that body1 derived from observation and calculation4 ,to this purpose1 therefore1 we will now devote a few pages1 confining ourselves to such matters as specially bear upon the requirements of our subject1 omitting such as are irrelevant to our purpose1 and touching but lightly upon such as are commonly known1 or are explained in ordinary elementary treatises on astronomy4 ,first1 then1 as regards the form of the moon4 ,the form of the lunar disc1 when fully illuminated1 we perceive to be a perfect circle2 that is to say1 the measured diameters in all directions are equal2 and we are therefore led to infer that the real form of the moon is that of a perfect sphere4 ,we know that the earth and the rest of the planets of our system are spheroidal1 or more or less flattened at the poles1 and we also know that this flattening is a consequence of axial rotation2 the extent of the flattening1 or the oblateness of the spheroid1 depending upon the speed of that rotation4 ,but in the case of the moon the axial rotation is so slow that the flattening produced thereby1 although it must exist1 is so slight as to be imperceptible to our observation4 ,we might therefore conclude that the moon is a perfectly spherical body1 did not theory step in to show us that there is another cause by which its form is disturbed4 ,assuming the moon to have been once in a fluid state1 it is demonstrable that the attraction of the earth would accumulate a mass of matter1 like a tidal elevation1 in the direction of a line joining the centres of the two bodies3 and as a consequence1 the real shape of the moon must be an ellipsoid1 or somewhat egg-shaped body1 the major axis of which is directed towards the earth4 ,that some such phenomenon has obtained is evident from the coincidence of the times of orbital revolution and axial rotation of the lunar sphere4 8,it would be against all probability10 says ,laplace1 8to suppose that these two motions had been at their origin perfectly equal20 but it is sufficient that their primitive difference was but small1 in which case the constant attraction by the earth of the protuberant part of the moon would establish the equality which at present exists4 ,it is1 however1 sufficient for all purposes with which we are concerned to regard the moon as a sphere1 and the next point to be considered is its size4 ,to determine this1 two data are necessary--its apparent or angular diameter1 and its distance from the earth4 ,the first of these is obtained by measuring the angle comprised between two lines directed from the eye to two opposite 8limbs0 or edges of the moon4 ,if1 for instance1 we were to take a pair of compasses and1 placing the joint at the eye1 open out the legs till the two points appear to touch two opposite edges of the moon1 the two legs would be inclined at an angle which would represent the diameter of the moon1 and this angle we could measure by applying a divided arc or protractor to the compasses4 ,in practice this measurement is made by means of telescopes attached to accurately divided circles2 the difference between the readings of the circle when the telescope is directed to opposite limbs of the moon giving its angular diameter at the time of the observation4 ,but from the fact that the orbit of the moon is an ellipse1 it is evident that she is at some times much nearer to us than at others1 and1 as a consequence1 her apparent magnitude is variable3 there is also a slight variation depending upon the altitude of the moon at the time of the measure2 the mean diameter1 however1 or the diameter at mean distance from the centre of the earth has1 from long course of observation1 been found to be #ca #i4 ,to convert this apparent angular diameter into real linear measurement1 it is necessary to know either the distance of the moon from the earth1 or in astronomical language as leading to a knowledge of that distance1 what is the amount of the moon's parallax4 ,parallax1 generally1 is an apparent change of position of an object arising from change of the point of view4 ,the parallax of a heavenly body is the angle which the earth would subtend if it were seen from that body4 ,supposing an observer on the moon could measure the earth's angular diameter1 just as we measure that of the moon1 his measurement would represent what is called the parallax of the moon4 ,but we cannot go to the moon to make such a measurement2 nevertheless there is a simple method1 explained in most treatises on astronomy1 which consists in observing the moon from stations on the earth widely separated1 and by which we can obtain a precisely similar result4 ,without detailing the process1 it is sufficient for us to know that the angle which would be subtended by the earth if seen from the moon1 or the moon's parallax1 is according to the latest determination1 equal to #a #ed #e4 ,this value1 however1 varies considerably with the variations of distance due to the elliptic orbit of the moon3 the number we have given represents the mean parallax1 or the parallax at mean distance4 ,but we have to turn these angular measurements into miles4 ,to effect this we have only to work a simple rule of three sum4 ,it will easily be understood that1 as the angular diameter of the earth seen from the moon is to the angular diameter of the moon seen from the earth1 so is the diameter of the earth in miles to the diameter of the moon in miles4 ,the diameter of the earth we know to be #giab miles3 putting this therefore in its proper place in the proportion sum1 and duly working it out by the schoolboy's rule1 we get3-- #a4 #ed4 #e 3 #ca4 #i 33 #giab miles4 3 #bafj miles4 ,and #bafj miles is therefore the diameter of the lunar globe4 ,knowing the diameter1 we can easily obtain the other elements of magnitude4 ,according to the well-known relation of the diameter of a sphere to its area1 we find the area of the moon to be #ad1feg1jjj square miles3 or half that number1 #g1cbh1ejj miles1 as the area of the hemisphere at any one time presented to our view4 ,and similarly1 from the relation of the solidity of a sphere to its diameter1 we find the solid contents of the moon to be #ebgf millions of cubic miles of matter4 ,comparing these data with corresponding dimensions of the earth1 we find that the diameter of the moon is #a_/cffe2 the area #a_/acdbde2 and the volume #a_/diahfe1 of the respective elements of the earth4 ,those who prefer a graphical to a numerical comparison1 may judge of the sizes of the two bodies by the accompanying illustration 7,fig4 #aj74 ,to gain an idea of their distance from each other it is necessary to suppose the two discs in the diagram to be #cj inches apart2 the real distance of the moon from the earth being about #bch1gij miles at its mean position4 ,illustration3 ,fig4 #aj4 ,next1 we come to what is technically termed the mass1 but what in common language we may call the weight of the moon4 ,it is important to know this1 because the weight of a body taken in connection with its size furnishes us with a knowledge of its density1 or the specific gravity of the material of which it is composed4 ,but it is not quite so easy to determine the mass as the dimensions of the moon3 to measure it1 we have seen is easy enough2 to weigh it is a comparatively difficult matter4 ,to solve the problem we have to appeal to ,newton's law of universal gravitation4 ,this law teaches us that every particle of matter in the universe attracts every other particle with a force which is directly proportional to the mass1 and inversely proportional to the distance of the attracting particles4 ,there are several methods by which this law is applied to the measurement of the mass of the moon4 ,one of the simplest is by the agency of the ,tides4 ,we know that the moon1 attracting the waters1 produces a certain amount of elevation of the aqueous covering of the earth2 and we know that the sun produces also a like elevation1 but to a much smaller extent1 by reason of its much greater distance4 ,now measuring accurately the heights of the solar and lunar tides1 and making allowance for the difference of distance of the sun and moon from the earth1 we can compare directly the effect that is due to the sun with the effect that is due to the moon3 and since the masses of the two bodies are just in proportion to the effects they produce1 it is evident that we have a comparison between the mass of the sun and that of the moon2 and knowing what is the sun's mass we can1 by simple proportion1 find that of the moon4 ,another method is as follows3--,the moon is retained in her orbital path by the attraction of the earth2 if it were not for this attraction she would fly off from her course in a tangential line4 ,she has thus a constant tendency to quit her orbit1 which the earth's attraction as constantly overcomes4 ,it is evident from this that the earth pulls the moon towards itself by a definite amount in every second of time4 ,but while the earth is pulling the moon1 the moon is also pulling the earth3 they are pulling each other together2 and moreover each is exerting a pull which is proportional to its mass4 ,knowing1 then1 the mass of the earth1 which we do with considerable accuracy1 we can find what share of the whole pulling force is due to it1 the residue being the moon's share3 the proportion which this residue bears to the earth's share gives us the proportion of the moon's mass to that of the earth1 and hence the mass of the moon4 ,there are yet two other methods3 one depending upon the phenomena of nutation1 or the attraction of the sun and moon upon the protruberant matter of the terrestrial spheroid2 and the other upon a displacement of the centre of gravity of the earth and moon1 which shows itself in observations of the sun4 ,by each and all of these methods has the lunar mass been at various times determined1 and it has been found1 as the latest and best accepted value1 that the mass of the moon is one-eightieth that of the earth4 ,from the known diameter of the earth we ascertain that its volume is #bei1cfj millions of cubic miles3 and from the various experiments that have been made to determine the mean density of the earth1 it has been found that that mean density is about #e times that of water2 that is to say1 the earth weighs #e times heavier than would a sphere of water of equal size4 ,now a cubic foot of water weighs #fbcbaa pounds1 and from this we can find by simple multiplication what is the weight of a cubic mile of water1 and1 similarly1 what would be the weight of #bei1cfj cubic miles of water1 and the last result multiplied by #e will give the weight of the earth in tons3 ,the calculation1 although extremely simple1 involves a confusing heap of figures2 but the result1 which is all that concerns us1 is1 that the weight of the earth is #ehdb trillions of tons3 and since1 as we have above stated1 the mass of the earth is #hj times that of the moon1 it follows that the weight of the moon is #gc trillions of tons4 ,the cubical contents of a body compared with its weight gives us its density4 ,in the moon we have #ebgf millions of cubic miles of matter1 the total weight of which is #gc trillions of tons4 ,now1 #ebgf millions of cubic miles of water would weigh about #ba trillions of tons2 and as this number is to #gc as #a is to #cd1 it is clear that the density of the lunar matter is #cd greater than water3 and inasmuch as the earth is #e times denser than water1 we see that the moon is about #jfb as dense as the earth1 or that the material of the moon is lighter1 bulk for bulk1 than the mean material of the terraqueous globe in the proportion of #fb to #ajj1 or1 nearly1 #f to #aj4 ,this specific gravity of the lunar material 7#cd7 we may remark is about the same as that of flint glass or the diamond3 and curiously enough it nearly coincides with that of some of the arolites that have from time to time fallen to the earth2 hence support has been claimed for the theory that these bodies were originally fragments of lunar matter1 probably ejected at some time from the lunar volcanoes with such force as to propel them so far within the sphere of the earth's attraction that they have ultimately been drawn to its surface4 ,reverting1 now1 to the mass of the moon3 we must bear in mind that the mass or weight of a planetary body determines the weight of all objects on its surface4 ,what we call a pound on the earth1 would not be a pound on the moon2 for the following reason3--,when we say that such and such an object weighs so much1 we really mean that it is attracted towards the earth with a certain force depending upon its own weight4 ,this attraction we call gravity2 and the falling of a weight to the earth is an example of the action of the law of universal gravitation4 ,the earth and the weight fall together--or are held together if the weight is in contact with the earth--with a force which depends directly upon the mass of the two1 and upon the distance between them4 ,newton proved that the attraction of a sphere upon external objects is precisely as if the whole of its matter were contained at its centre4 ,so that the attractive force of the earth upon a ton weight at its surface1 is the attraction which #ehdb trillions of tons exert upon one ton situated #cief miles 7the radius of the earth7 distant4 ,if the weight of the earth were only half the above quantity1 it is clear that the attraction would be only half what it is2 and hence the ton weight1 being pulled by only half the force1 would only be equal to half a ton2 that is to say1 only half as much muscular force 7or any other force but gravity7 would be required to lift it4 ,it is plain1 therefore1 that what weighs a pound on the earth could not weigh a pound on the moon1 which is only #a_/hj of the weight of the earth4 ,what1 then1 is the relation between a pound on the earth and the same mass of matter on the moon8 ,it would seem1 since the moon's mass is #a_/hj of the earth1 that the pound transported to the moon ought to weigh the eightieth part of a pound there2 and so it would if the distance from the centre of the moon to its surface were the same as the distance of the centre of the earth from its surface4 ,but the radius of the moon is only #a_/cffe that of the earth2 and the force of gravity varies inversely as the square of the distance between the centres of the gravitating masses4 ,so that the attraction by the moon of a body at its surface1 as compared with that of the earth1 is #a_/hj multiplied by the square of #a_/cffe2 and this1 worked out1 is equal to #a_/f4 ,the force of gravity upon the moon is1 therefore1 #a_/f of that on the earth2 and hence a pound upon the earth would be little more than #b ounces on the moon2 and it follows as a consequence that any force1 such as muscular exertion1 or the energy of chemical1 plutonic or explosive forces1 would be six times more effective upon the moon than upon the earth4 ,a man who could jump six feet from the earth1 could with the same muscular effort jump thirty-six feet from the moon2 the explosive energy that would project a body a mile above the earth would project a like body six miles above the surface of the moon4 ,it is the practice1 in elementary and popular treatises on astronomy1 to state merely the numerical results in giving data such as those embodied in the foregoing pages2 and uninitiated readers1 not knowing the means by which the figures are arrived at1 are sometimes disposed to regard them with a certain amount of doubt or uncertainty4 ,on this account we have thought it advisable to give1 in as brief and concise a form as possible1 the various steps by which these seemingly unattainable results are obtained4 ,the data explained in the foregoing text are here collected to facilitate reference4 ,diameter of ,moon #bafj miles #a_/cffe that of earth4 ,area #ad1feg1jjj square miles #a_/acdbd 0 0 ,area of the #g1cbh1ejj square miles visible hemisphere ,solid contents #ebgf millions of cubic miles #a_/diahf 0 0 ,mass #gc trillions of tons #a_/hj 0 0 ,density #cci 7water #a7 #jfb 0 0 ,force of #a_/f 0 0 gravity at surface ,mean distance #bch1gij miles4 from earth ,,chapter ,v4 ,,on ,,the ,,existence ,,or ,,non-,,existence ,,of ,a ,,lunar ,,atmosphere4 ,at the close of the preceding chapter we stated that any force acting in opposition to that of gravity would be six times more effective on the moon than on the earth4 ,but1 in fact1 it would in many cases be still more so2 at all events1 so far as projectile forces are concerned2 for the reason that 8the powerful coercer of projectile range10 as the earth's atmosphere has been termed1 has no counterpart1 or at most a very disproportionate one1 upon the moon4 ,the existence of an atmosphere surrounding the moon has been the subject of considerable controversy1 and a great deal of evidence on both sides of the question has been offered from time to time1 and is to be found scattered through the records of various classes of observations4 ,some of the more important items of this evidence it is our purpose to set forth in the course of the present chapter4 ,with the phenomena of the terrestrial atmosphere1 with the effects that are attributable to it1 we are all well familiar1 and our best course therefore is to examine1 as far as we are able1 whether counterparts of any of these effects are manifested upon the moon4 ,for instance1 the clouds that are generated in and float through our air would1 to an observer on the moon1 appear as ever changing bright or dusky spots1 obliterating certain of the permanent details of the earth's surface1 and probably skirting the terrestrial disc1 like the changing belts we perceive on the planet ,jupiter1 or diversifying its features with less regularity1 after the manner exhibited by the planet ,mars4 ,if such clouds existed on the moon it is evident that the details of its surface must be1 from time to time1 similarly obscured2 but no trace of such obscuration has ever been detected4 ,when the moon is observed with high telescopic powers1 all its details come out sharp and clear1 without the least appearance of change or the slightest symptoms of cloudiness other than the occasional want of general definition1 which may be proved to be the result of unsteadiness or want of homogeneity in our own atmosphere2 for we must tell the uninitiated that nights of pure1 good definition1 such as give the astronomer opportunity of examining with high powers the minute details of planetary features1 are very few and far between4 ,out of the three hundred and sixty-five nights of a year there are probably not a dozen that an astronomer can call really fine3 usually1 even on nights that are to all common appearance superbly brilliant1 some strata of air of different densities or temperatures1 or in rapid motion1 intervene between the observer and the object of his observation1 and through these1 owing to the ever-changing refractions which the rays of light coming from the object suffer in their course1 observation of the delicate markings of a planet is impossible3 all is blurred and confused1 and nothing but bolder features can be recognized4 ,it has in consequence sometimes happened that a slight indistinctness of some minute detail of the moon has been attributed to clouds or mists at the lunar surface1 whereas the real cause has been only a bad condition of our own atmosphere4 ,it may be confidently asserted that when all indistinctness due to terrestrial causes is taken account of or eliminated1 there remain no traces whatever of any clouds or mists upon the surface of the moon4 ,this is but one proof against the existence of a lunar atmosphere1 and1 it may be argued1 not a very conclusive one2 because there may still be an atmosphere1 though it be not sufficiently aqueous to condense into clouds and not sufficiently dense to obscure the lunar details4 ,the probable existence of an atmosphere of such a character used to be inferred from a phenomenon seen during total eclipses of the sun4 ,on these occasions the black body of the moon is invariably surrounded by a luminous halo1 or glory1 to which the name 8corona0 has been applied2 and1 further1 besides this corona1 apparently floating in it and sometimes seemingly attached to the black edge of the moon1 are seen masses of cloud-like matter of a bright red colour1 which1 from the form in which they were first seen and from their flame-like tinge1 have become universally known as the 8red-flames40 ,it used to be said that this corona could only be the consequence of a lunar atmosphere lit up as it were by the sun's rays shining through it1 after the manner of a sunbeam lighting up the atmosphere of a dusty chamber2 and the red flames were held by those who first observed them to be clouds of denser matter floating in the said atmosphere1 and refracting the red rays of solar light as our own clouds are seen to do at sunrise and sunset4 ,but the evidence obtained1 both by simple telescopic observation and by the spectroscope1 from recent extensively observed eclipses of the sun has set this question quite at rest2 for it has been settled finally and indisputably that both the above appearances pertain to the sun1 and have nothing whatever to do with the moon4 ,illustration3 ,fig4 #aa4 ,the occurrence of a solar eclipse offers other means in addition to the foregoing whereby a lunar atmosphere would be detected4 ,we know that all gases and vapours absorb some portion of any light which may shine through them4 ,if then our satellite had an atmosphere1 its black nucleus when seen projected against the bright sun in an eclipse would be surrounded by a sort of penumbra1 or zone of shadow1 in contact with its edge1 somewhat like that we have shown in an exaggerated degree in the annexed cut 7,fig4 #aa71 and the passage of this penumbra over solar spots and other features of the solar photosphere would to some extent obscure the more minute details of such features4 ,no such dusky band has however been at any time observed4 ,on the contrary1 a band somewhat brighter than the general surface of the sun has frequently been seen in contact with the black edge of the moon3 this in its turn was held to indicate an atmosphere about the moon2 but ,sir ,george ,airy has shown that a lunar atmosphere1 if it really did exist1 could not produce such an appearance1 and that the cause of it must be sought in other directions4 ,if this effect were really due to the passage of the solar rays through a lunar atmosphere a similar effect ought to be produced by the passage of the sun's rays through the terrestrial atmosphere3 and we might hence expect to see the shadow of the earth projected on the moon during a lunar eclipse surrounded by a sort of bright zone or halo3 we need hardly say such an appearance has never manifested itself4 ,similarly as we stated that the delicate details of solar spots would be obscured by a lunar atmosphere1 small stars passing behind the moon would suffer some diminution in brightness as they approached apparent contact with the moon's edge3 this fading has been watched for on many occasions1 and in a few cases such an appearance has been suspected1 but in by far the majority of instances nothing like a diminution of brightness or change of colour of the stars has been seen2 stars of the smallest magnitude visible under such circumstances retain their feeble lustre unimpaired up to the moment of their disappearance behind the moon's limb4 ,again1 in a solar eclipse1 even if there were an atmosphere about the moon not sufficiently dense to form a hazy outline or impair the distinctness of the details of a solar spot1 it would still manifest its existence in another way4 ,as the moon advances upon the sun's disc the latter assumes1 of course1 a crescent form4 ,now if air or vapour enveloped the moon1 the exceedingly delicate cusps of this crescent would be distorted or turned out of shape4 ,instead of remaining symmetrical1 like the lower one in the annexed drawing 7,fig4 #ab71 they would be bent or deformed after the manner we have shown in the upper one4 ,the slightest symptom of a distortion like this could not fail to obtrude itself upon an observer's eye2 but in no instance has anything of the kind been seen4 ,reverting to the consequences of the terrestrial atmosphere3 one of the most striking of these is the phenomenon of diffused daylight1 which we need hardly remind the reader is produced by the scattering or diffusion of the sun's rays among the minute particles of vapour composing or contained in that atmosphere4 ,were it not for this reflexion and diffusion of the sun's light1 those parts of our earth not exposed to direct sunshine would be hidden in darkness1 receiving no illumination beyond the feeble amount that might be reflected from proximate terrestrial objects actually illuminated by direct sunlight4 ,twilight is a consequence of this reflexion of light by the atmosphere when the sun is below the horizon4 ,if1 then1 an atmosphere enveloped the moon1 we should see by diffused light those parts of the lunar details that are not receiving the direct solar beams2 and before the sun rose and after it had set upon any region of the moon1 that region would still be partially illuminated by a twilight4 ,but1 on the contrary1 the shadowed portions of a lunar landscape are pitchy black1 without a trace of diffused-light illumination1 and the effects that a twilight would produce are entirely absent from the moon4 ,once1 indeed1 one observer1 ,schroeter1 noticed something which he suspected was due to an effect of this kind3 when the moon exhibited itself as a very slender crescent1 he discovered a faint crepuscular light1 extending from each of the cusps along the circumference of the unenlightened part of the disc1 and he inferred from estimates of the length and breadth of the line of light that there was an atmosphere about the moon of #ecgf feet in height4 ,this is the only instance on record1 we believe1 of such an appearance being seen4 ,illustration3 ,fig4 #ab4 ,spectrum analysis would also betray the existence of a lunar atmosphere4 ,the solar rays falling on the moon are reflected from its surface to the earth4 ,if1 then1 an atmosphere existed1 it is plain that the solar rays must first pass through such atmosphere to reach the reflecting surface1 and returning from thence1 again pass through it on their way to the earth2 so that they must in reality pass through virtually twice the thickness of any atmosphere that may cover the moon4 ,and if there be any such atmosphere1 the spectrum formed by the moon's light1 that is1 by the sun's light reflected from the moon1 would be modified in such a manner as to exhibit absorption-lines different from those found in the spectrum of the direct solar rays1 just as the absorption-lines vary according as the sun's rays have to pass through a thinner or a denser stratum of the terrestrial atmosphere4 ,guided by this reasoning1 ,drs4 ,huggins and ,miller made numerous observations upon the spectrum of the moon's light1 which are detailed in the 8,philosophical ,transactions0 for the year #ahfd2 and their result1 quoting the words of the report1 was 8that the spectrum analysis of the light reflected from the moon is wholly negative as to the existence of any considerable lunar atmosphere40 ,upon another occasion1 ,dr4 ,huggins made an analogous observation of the spectrum of a star at the moment of its occultation1 which observation he records in the following words3--8,when an observation is made of the spectrum of a star a little before1 or at the moment of its occultation by the dark limb of the moon1 several phenomena characteristic of the passage of the star's light through an atmosphere might possibly present themselves to the observer4 ,if a lunar atmosphere exist1 which either by the substances of which it is composed1 or by the vapours diffused through it1 can exert a selective absorption upon the star's light1 this absorption would be indicated to us by the appearance in the spectrum of new dark lines immediately before the star is occulted by the moon40 8,if finely divided matter1 aqueous or otherwise1 were present about the moon1 the red rays of the star's light would be enfeebled in a smaller degree than the rays of higher refrangibilities40 8,if there be about the moon an atmosphere free from vapour1 and possessing no absorptive power1 but of some density1 then the spectrum would not be extinguished by the moon's limb at the same instant throughout its length4 ,the violent and blue rays would lay behind the red rays40 8,i carefully observed the disappearance of the spectrum of ,piscium at its occultation of ,january #d1 #ahfe1 for these phenomena2 but no signs of a lunar atmosphere were detected40 ,but perhaps the strongest evidence of the non-existence of any appreciable lunar atmosphere is afforded by the non-refraction of the light of a star passing behind the edge of the lunar disc4 ,refraction1 we know1 is a bending of the rays of light coming from any object1 caused by their passage through strata of transparent matter of different densities2 we have a familiar example in the apparent bending of a stick when half plunged into water4 ,there is a simple schoolboy's experiment which illustrates refraction in a very cogent manner1 but which we should1 from its very simplicity1 hesitate to recall to the reader's mind did it not very aptly represent the actual case we wish to exemplify4 ,a coin is placed on the bottom of an empty basin1 and the eye is brought into such a position that the coin is just hidden behind the basin's rim4 ,water is then poured into the basin and1 without the eye being moved from its former place1 as the depth of water increases1 the coin is brought by degrees fully into view2 the water refracting or turning out of their course the rays of light coming from the coin1 and lifting them1 as it were1 over the edge of the basin4 ,now a perfectly similar phenomenon takes place at every sunrise and sunset on the earth4 ,when the sun is really below the horizon1 it is nevertheless still visible to us because it is brought up by the refraction of its light by the dense stratum of atmosphere through which the rays have to pass4 ,the sun is1 therefore1 exactly represented by the coin at the bottom of the basin in the boy's experiment1 the atmosphere answers to the water1 and the horizon to the rim or edge of the basin4 ,if there were no atmosphere about the earth1 the sun would not be so brought up above the horizon1 and1 as a consequence1 it would set earlier and rise later by about a minute than it really does4 ,this1 of course1 applies not merely to the sun1 but to all celestial bodies that rise and set4 ,every planet and every star remains a shorter time below the horizon than it would if there were no atmosphere surrounding the earth4 ,to apply this to the point we are discussing4 ,the moon in her orbital course across the heavens is continually passing before1 or occulting1 some of the stars that so thickly stud her apparent path4 ,and when we see a star thus pass behind the lunar disc on one side and come out again on the other side1 we are virtually observing the setting and rising of that star upon the moon4 ,if1 then1 the moon had an atmosphere1 it is clear1 from analogy to the case of the earth1 that the star must disappear later and reappear sooner than if it has no atmosphere3 just as a star remains too short a time below the earth's horizon1 or behind the earth1 in consequence of the terrestrial atmosphere1 so would a star remain too short a time behind the moon if an atmosphere surrounded that body4 ,the point is settled in this way3--,the moon's apparent diameter has been measured over and over again and is known with great accuracy2 the rate of her motion across the sky is also known with perfect accuracy3 hence it is easy to calculate how long the moon will take to travel across a part of the sky exactly equal in length to her own diameter4 ,supposing1 then1 that we observe a star pass behind the moon and out again1 it is clear that1 if there be no atmosphere1 the interval of time during which it remains occulted ought to be exactly equal to the computed time which the moon would take to pass over the star4 ,if1 however1 from the existence of a lunar atmosphere1 the star disappears too late and reappears too soon1 as we have seen it would1 these two intervals will not agree2 the computed time will be greater than the observed time1 and the difference1 if any there be1 will represent the amount of refraction the star's light has sustained or suffered1 and hence the extent of atmosphere it has had to pass through4 ,comparisons of these two intervals of time have been repeatedly made1 the most recent and most extensive was executed under the direction of the ,astronomer-,royal several years ago1 and it was based upon no less than #bif occultation observations4 ,in this determination the measured or telescopic semidiameter of the moon was compared with the semidiameter deduced from the occultations1 upon the above principle1 and it was found that the telescopic semidiameter was greater than the occultation semidiameter by two seconds of angular measurement or by about a thousandth part of the whole diameter of the moon4 ,sir ,george ,airy1 commenting on this result1 says that it appears to him that the origin of this difference is to be sought in one of two causes4 8,either it is due to irradiation#c of the telescopic semidiameter1 and ,i do not doubt that a part at least of the two seconds is to be ascribed to that cause2 or it may be due to refraction by the moon's atmosphere4 ,if the whole two seconds were caused by atmospheric refraction this would imply a horizontal refraction of one second1 which is only #a_/bjjj part of the earth's horizontal refraction4 ,it is possible that an atmosphere competent to produce this refraction would not make itself visible in any other way40 ,this result accords well1 considering the relative accuracy of the means employed1 with that obtained a century ago by the ,french astronomer ,du ,sjour1 who made a rigorous examination of the subject founded on observations of the solar eclipse of #agfd4 ,he concluded that the horizontal refraction produced by a possible lunar atmosphere amounted to #ae--;a second and a half--or about #a_/adjj of that produced by the earth's atmosphere4 ,the greater weight is of course to be allowed to the more recent determination in consideration of the large number of accurate observations upon which it was based4 ,but an atmosphere #b1jjj times rarer than our air can scarcely be regarded as an atmosphere at all4 ,the contents of an air-pump receiver can seldom be rarefied to a greater extent than to about #a_/ajjj of the density of air at the earth's surface1 with the best of pneumatic machines2 and the lunar atmosphere1 if it exist at all1 is thus proved to be twice as attenuated as what we are accustomed to recognise as a vacuum4 ,in discussing the physical phenomena of the lunar surface1 we are1 therefore1 perfectly justified in omitting all considerations of an atmosphere1 and adapting our arguments to the non-existence of such an appendage4 ,and if there be no air upon the moon1 we are almost forced to conclude that there can be no water2 for if water covered any part of the lunar globe it must be vapourised under the influence of the long period of uninterrupted sunshine 7upwards of #cjj hours7 that constitutes the lunar day1 and would manifest itself in the form of clouds or mists obscuring certain parts of the surface4 ,but1 as we have already said1 no such obliteration of details ever takes place2 and1 as we have further seen1 no evidence of aqueous vapour is manifested upon the occasion of spectrum observations4 ,since1 then1 the effects of watery vapour are absent1 we are forced to conclude that the cause is absent also4 ,those parts of the moon which the ancient astronomers assumed1 from their comparatively smooth and dusky appearance1 to be seas1 have long since been discovered to be merely extensive regions of less reflective surface material2 for the telescope reveals to us irregularities and asperities covering well nigh the whole of them1 which asperities could not be seen if they were covered with water2 unless1 indeed1 we admit the possibility of seeing to the bottom of the water1 not only perpendicularly1 but obliquely4 ,some observers have noticed features that have led them to suppose that water was at one time present upon the moon1 and has left its traces in the form of appearances of erosive action in some parts4 ,but if water ever existed1 where is it now8 ,one writer1 it is true1 has suggested as possible1 that whatever air1 and we presume he would include whatever water also1 the moon may possess1 is hidden away in sublunarean caves and hollows2 but even if water existed in these places it must sometimes assume the vapoury form1 and thus make its presence known4 ,illustration3 ,fig4 #ac4 ,illustration3 ,fig4 #ad4 ,sir ,john ,herschel pointed out that if any moisture exists upon the moon1 it must be in a continual state of migration from the illuminated or hot1 to the unilluminated or cold side of the lunar globe4 ,the alternations of temperature1 from the heat produced by the unmitigated sunshine of #ad days' duration1 to the intensity of cold resulting from the absence of any sunshine whatever for an equal period1 must1 he argued1 produce an action similar to that of the cryophorus in transporting the lunar moisture from one hemisphere to the other4 ,the cryophorus is a little instrument invented by the late ,dr4 ,wollaston2 it consists of two bulbs of glass connected by a bent tube1 in the manner shown in the annexed illustration1 fig4 #ac4 ,one of the bulbs1 ,a1 is half-filled with water1 and1 all air being exhausted1 the instrument is hermetically sealed1 leaving nothing within but the water and the aqueous vapour which rises therefrom in the absence of atmospheric pressure4 ,when the empty bulb1 ,b1 is placed in a freezing mixture1 a rapid condensation of this vapour takes place within it1 and as a consequence the water in the bulb ,a gives off more vapour4 ,the abstraction of heat from the water1 which is a natural consequence of this evaporation1 causes it to freeze into a solid mass of ice4 ,now upon the moon the same phenomenon would occur did the material exist there to supply it4 ,in the accompanying diagram let ,a represent the illuminated or heated hemisphere of the moon1 and ,b the dark or cold hemisphere2 the former being probably at a temperature of #cjj above1 and the latter #bjj below ,fahrenheit's zero4 ,upon the above principle1 if moisture existed upon ,a it would become vapourised1 and the vapour would migrate over to ,b1 and deposit itself there as hoarfrost2 it would1 therefore1 manifest itself to us while in the act of migrating by clouding or dimming the details about the boundary of the illuminated hemisphere4 ,the sun1 rising upon any point upon the margin of the dark hemisphere1 would have to shine through a bed of moisture1 and we may justly suppose1 if this were the case1 that the tops of mountains catching the first beams of sunlight would be tinged with colour1 or be lit up at first with but a faint illumination1 just as we see in the case of terrestrial mountains whose summits catch the first1 or receive the last beams of the rising or setting sun4 ,nothing of this kind is1 however1 perceptible3 when the solar rays tip the lofty peaks of lunar mountains1 these shine at once with brilliant light1 quite as vivid as any of those parts that receive less horizontal illumination1 or upon which the sun is almost perpendicularly shining4 ,all the evidence1 then1 that we have the means of obtaining1 goes to prove that neither air nor water exist upon the moon4 ,two complicating elements affecting all questions relating to the geology of the terraqueous globe we inhabit may thus be dismissed from our minds while considering the physical features of the lunar surface4 ,fire on the one hand and water or the other1 are the agents to which the configurations of the earth's surface are referrable3 the first of these produced the igneous rocks that form the veritable foundations of the earth1 the second has given rise to the superstructure of deposits that constitute the secondary and tertiary formations3 were these last removed from the surface of our planet1 so as to lay bare its original igneous crust1 that crust1 so far as reasoning can picture it to us1 would probably not differ essentially from the visible surface of the moon4 ,in considering the causes that have given birth to the diversified features of that surface1 we may1 therefore1 ignore the influence of air and water action and confine our reasoning to igneous phenomena alone3 our task in this matter1 it is hardly necessary to remark1 is materially simplified thereby4 ,,chapter ,,vi4 ,,the ,,general ,,aspect ,,of ,,the ,,lunar ,,surface4 ,we have now reached that stage of our subject at which it behoves us to repair to the telescope for the purpose of examining and familiarising ourselves with the various classes of detail that the lunar surface presents to our view4 ,that the moon is not a smooth sphere of matter is a fact that manifested itself to the earliest observers4 ,the naked eye perceives on her face spots exhibiting marked differences of illumination4 ,these variations of light and shade1 long before the invention of the telescope1 induced the belief that she possessed surface irregularities like those that diversify the face of the earth1 and from analogy it was inferred that seas and continents alternated upon the lunar globe4 ,it was evident1 from the persistence and invariability of the dusky markings1 that they were not due to atmospheric peculiarities1 but were veritable variations in the character or disposition of the surface material4 ,fancy made pictures of these unchangeable spots3 untutored gazers detected in them the indications of a human countenance1 and perhaps the earliest map of the moon was a rough reproduction of a man's face1 the eyes1 nose and mouth representing the more salient spots discernible upon the lunar disc4 ,others recognised in these spots the configuration of a human form1 head1 arms and legs complete1 which a ,french superstition that lingers to the present day held to be the image of ,judas ,iscariot transported to the moon in punishment for his treason4 ,again1 an ,indian notion connects the lunar spots with a representation of a roebuck or a hare1 and hence the ,sanskrit names for the moon1 mrigadhara1 a roebuck-bearer1 and 'sa'sabhrit1 a hare-bearer4 ,of these similitudes the one which has the best pretensions to a rude accuracy is that first mentioned2 for the resemblance of the full moon to a human countenance1 wearing a painful or lugubrious expression1 is very striking4 ,our illustration of the full moon 7,plate ,,iii47 is derived from an actual photograph2#d the relative intensities of light and shade are hence somewhat exaggerated2 otherwise it represents the full moon very nearly as the naked eye sees it1 and by gazing at the plate from a short distance1#e the well-known features will manifest themselves1 while they who choose may amuse themselves by arranging the markings in their imagination till they conform to the other appearances alluded to4 ,we may remark in passing that by one sect of ancient writers the moon was supposed to be a kind of mirror1 receiving the image of the earth and reflecting it back to terrestrial spectators4 ,humboldt affirmed that this opinion had been preserved to his day as a popular belief among the people of ,asia ,minor4 ,he says1 8,i was once very much astonished to hear a very well educated ,persian from ,ispahan1 who certainly had never read a ,greek book1 mention when ,i showed him the moon's spots in a large telescope in ,paris1 this hypothesis as a widely diffused belief in his country3 #8,what we see in the moon1' said the ,persian1 #8is ourselves2 it is the map of our earth4'0 ,quite as extravagant an idea1 though perhaps a more excusable one1 was that held by some ancient philosophers1 to the effect that the spots on the moon were the shadows of opaque bodies floating in space between it and the sun4 ,illustration3 ,,plate ,,iii4 ,,full ,,moon4 ,an observer watching the forms and positions of the lunar face-marks1 from night to night and from lunation to lunation1 cannot fail to notice the circumstance that they undergo no easily perceptible change of position with respect to the circular outline of the disc2 that in fact the face of the moon presented to our view is always the same1 or very nearly so4 ,if the moon had no orbital motion we should be led from the above phenomenon to conclude that she had no axial motion1 no movement of rotation2 but when we consider the orbital motion in connection with the permanence of aspect1 we are driven to the conclusion--one1 however1 which superficial observers have some difficulty in recognising--that the moon has an axial rotation equal in period to her orbital revolution4 ,since the moon makes the circuit of her orbit in twenty-seven days and one-third 7more exactly #bg;d4 #g;h4 #dcm4 #aas47 it follows that this is the time of her axial rotation1 as referred to the stars1 or as it would be made out by an observer located at a fixed position in space outside the lunar orbit4 ,but if referred to the sun this period appears different2 because the moon while revolving round the earth is1 with the earth1 circulating around the sun4 ,suppose the three bodies1 moon1 earth1 and sun1 to be in a line at a certain period of a lunation1 as they are at full moon3 by the time the moon has completed her twenty-seven days' journey around the earth1 the latter will have moved along twenty-seven days' march of its orbit1 which is about twenty-seven degrees of celestial longitude3 the sun will apparently be that much distant from a straight line passing through earth and moon1 and the moon must therefore move forward to overtake the sun before she can assume the full phase again4 ,she will take something over two days to do this2 hence the solar period of her revolution becomes more than twenty-nine days 7to be exact1 #bi;d4 #ab;h4 #ddm4 #bs4 #hg74 ,this is the length of a solar day upon the moon--the interval from one sunrise to another at any spot upon the equator of our satellite1 and the interval between successive reappearances of the same phase to observers on the earth4 ,the physical cause of the coincidence of times of rotation and revolution was touched upon in a previous chapter4 ,we have said that the moon continuously presents to us the same hemisphere4 ,this is generally true1 but not entirely so4 ,galileo1 by long scrutiny1 familiarised himself with every detail of the lunar-disc that came within the limited grasp of his telescopes1 and he recognised the fact that according as the position of the moon varied in the sky1 so the aspect of her face altered to a slight degree2 that certain regions at the edge of her disc1 alternately came in sight and receded from his view4 ,he perceived1 in fact1 an apparent rocking to and fro of the globe of the moon2 a sort of balancing or libratory motion4 ,when the moon was near the horizon he could see spots upon her uppermost edge1 which disappeared as she approached the zenith1 or highest point of her nightly path2 and as she neared this point1 other spots1 before invisible1 came into view1 near to what had been her lower edge4 ,galileo was not long in referring this phenomenon to its true cause4 ,the centre of motion of the moon being the centre of the earth1 it is clear that an observer on the surface of the latter1 looks down upon the rising moon as from an eminence1 and thus he is enabled to see more or less over or around her4 ,as the moon increases in altitude1 the line of sight gradually becomes parallel to the line joining the observer and the centre of the earth1 and at length he looks her full in the face3 he loses the full view and catches another side face view as she nears the horizon in setting4 ,this phenomenon1 occurring as it does1 with a daily period1 is known as the diurnal libration4 ,but a kindred phenomenon presents itself in another period1 and from another cause4 ,the moon rotates upon her axis at a speed that is rigorously uniform4 ,but her orbital motion is not uniform1 sometimes it is faster1 and at other times slower than its average rate4 ,hence1 the angle through which she moves along her orbit in a given time1 now exceeds1 and now falls short of the angle through which she turns upon her axis4 ,her visible hemisphere thus changes to an extent depending upon the difference between these orbital and axial angles1 and the apparent balancing thus produced is called the libration in longitude4 ,then there is a libration in latitude due to the circumstance that the axis of the moon is not exactly perpendicular to the plane of her orbit2 the effect of this inclination being1 that we sometimes see a little more of the north than of the south polar regions of our satellite1 and vice vers4#f ,the extent of the moon's librations1 taking them all and in combination into account1 amounts to about seven degrees of arc of latitude or longitude upon the moon1 both in the north-south and east-west directions4 ,and taking into account the whole effect of them1 we may conclude that our view of the moon's surface1 instead of being confined to one half1 is extended really to about four-sevenths of the whole area of the lunar globe4 ,the remaining three-sevenths must for ever remain a terra incognita to the habitants of this earth1 unless1 indeed1 from some catastrophe which it would be wild fancy to anticipate1 a period of rotation should be given to the moon different from that which it at present possesses4 ,some highly fanciful theorists have speculated upon the possible condition of the invisible hemisphere1 and have propounded the absurd notion that the opposite side of the moon is hollow1 or that the moon is a mere shell2 others again have urged that the hidden half is more or less covered with water1 and others again that it is peopled with inhabitants4 ,there is1 however1 no good reason for supposing that what we may call the back of the moon has a physical structure essentially different from the face presented towards us4 ,so far as can be judged from the peeps that libration enables us to obtain1 the same characteristic features 7though of course with different details7 prevail over the whole lunar surface4 ,the speculative ideas held by the philosophers of the pre-telescopic age1 touching the causes which produced the inequalities of light and shade upon the moon1 received their coup de grce from the revelations of ,galileo's glasses4 ,our satellite was one of the earliest objects1 if not actually the first1 upon which the ,florentine turned his telescope2 and he found that the inequalities upon her surface were due to differences in its configuration analogous to the continents and islands1 and 7as might then have been thought7 the seas of our globe4 ,he could trace1 even with his moderate means1 the semblance of mountain-tops upon which the sun shone while their lower parts were in shadow1 of hills that were brightly illuminated upon their sides towards the sun1 of brightly shining elevations1 and deeply shadowed depressions1 of smooth plains1 and regions of mountainous ruggedness4 ,he saw that the boundary of sunlight upon the moon was not a clearly defined line1 as it would be if the lunar globe were a smooth sphere1 as the ,aristotelians had asserted1 but that the terminator was uneven and broken into an irregular outline4 ,from these observations the ,florentine astronomer concluded that the lunar world was covered not only with mountains like our globe1 but with mountains whose heights far surpassed those existing upon the earth1 and whose forms were strangely limited to circularity4 ,galileo's best telescopes magnified only some thirty times1 and the views which he thus obtained1 must have been similar to those exhibited by the smaller photographs of the moon produced in late years by ,mr4 ,de la ,rue and now familiar to the scientific public4 ,of course there is in the natural moon as viewed with a small telescope a vivid brilliancy which no art can imitate1 and in photographs especially there is a tendency to exaggeration of the depths of shade in a lunar picture4 ,this arises from the circumstance that various regions of the moon do not impress a chemically sensitized plate as they impress the retina of the eye4 ,some portions1 notably the so-called 8seas0 of the moon1 which to the eye appear but slightly duller than the brighter parts1 give off so little actinic light that they appear as nearly black patches upon a photograph1 and thus give an undue impression of the relative brightness of various parts of the lunar surface4 ,doubtless by sufficient exposure of the plate in the camera-telescope the dark patches might be rendered lighter1 but in that case the more strongly illuminated portions1 which after all are those most desirable to be preserved1 would be lost by the effect which photographers understand as 8solarization40 ,in speaking of a view of the moon with a magnifying power of thirty1 it is necessary to bear in mind that the visible features will differ considerably with the diameter of the object-glass of the telescope to which this power is applied4 ,the same details would not be seen alike with the same power upon an object-glass of #aj inches diameter and one of #b inches4 ,the superior illumination of the image in the former case would bring into view minute details that could not be perceived with the smaller aperture4 ,he who would for curiosity wish to see the moon1 or any other object1 as ,galileo saw it1 must use a telescope of the same size and character in all respects as ,galileo's3 it will not do to put his magnifying power upon a larger telescope4 ,with large telescopes1 and low powers used upon bright objects like the moon1 there is a blinding flood of light which tends to contract the pupil of the eye and prevent the passage of the whole of the pencil of rays coming through the eye-piece4 ,although this last result may be productive of no inconvenience1 it is clearly a waste of light1 and it points to a rule that the lowest power that a telescope should bear is that which gives a pencil of light equal in diameter to the pupil of the eye under the circumstances of brightness attendant upon the object viewed4 ,in observing faint objects this point assumes more importance1 since it is then necessary that all available light should enter the pupil4 ,the thought suggests itself that an artificial enlargement of the pupil1 as by a dose of belladonna1 might be of assistance in searching for faint objects1 such as nebul and comets3 but we prefer to leave the experiment for those to try who pursue that branch of astronomical observation4 ,a merely cursory examination of the moon with the low power to which we have alluded is sufficient to show us the more salient features4 ,in the first place we cannot help being struck with the immense preponderance of circular or craterform asperities1 and with the general tendency to circular shape which is apparent in nearly all the lunar surface markings2 for even the larger regions known as the 8seas0 and the smaller patches of the same character seem to repeat in their outlines the round form of the craters4 ,it is at the boundary of sunlight on the lunar globe that we see these craterform spots to the best advantage1 as it is there that the rising or setting sun casts long shadows over the lunar landscape1 and brings elevations and asperities into bold relief4 ,they vary greatly in size1 some are so large as to bear an estimable proportion to the moon's diameter1 and the smallest are so minute as to need the most powerful telescopes and the finest conditions of atmosphere to perceive them4 ,it is doubtful whether the smallest of them have ever been seen1 for there is no reason to doubt that there exist countless numbers that are beyond the revealing powers of our finest telescopes4 ,from the great number and persistent character of these circumvallations1 ,kepler was led to think that they were of artificial construction4 ,he regarded them as pits excavated by the supposed habitants of the moon to shelter themselves from the long and intense action of the sun4 ,had he known their real dimensions1 of which we shall have to speak when we come to describe them more in detail1 he would have hesitated in propounding such a hypothesis2 nevertheless it was1 to a certain extent1 justified by the regular and seemingly unnatural recurrence of one particular form of structure1 the like of which is1 too1 so seldom met with as a structural feature of the surface of our own globe4 ,the next most striking features1 revealed by a low telescopic power upon the moon1 are the seemingly smooth plains that have the appearance of dusky spots1 and that collectively cover a considerable portion--about two-thirds--of the entire disc4 ,the larger of these spots retain the name of seas1 the term having been given when they were supposed to be watery expanses1 and having been retained1 possibly to avoid the confusion inevitable from a change of name1 after the existence of water upon the moon was disproved4 ,following the same order of nomenclature1 the smaller spots have received the appellations of lakes1 bays and fens4 ,we see that many of these 8seas0 are partially surrounded by ramparts or bulwarks which1 under closer examination1 and having regard to their real magnitude1 resolve themselves into immense mountain chains4 ,the general resemblance in form which the bulwarked plains thus exhibit to the circular craters of large size1 would lead us to suppose that the two classes of objects had the same formative origin1 but when we take into account the immense size of the former1 and the process by which we infer the latter to have been developed1 the supposition becomes untenable4 ,another of the prominent features which we notice as highly curious1 and in some phases of the moon--at about the time of full--the most remarkable of all1 are certain bright lines that appear to radiate from some of the more conspicuous craters1 and extend for hundreds of miles around4 ,no selenological formations have so sorely puzzled observers as these peculiar streaks1 and a great deal of fanciful theorizing has been bestowed upon them4 ,as we are now only glancing at the moon1 we do not enter upon explanations concerning them or any other class of details2 all such will receive due consideration in their proper order in succeeding chapters4 ,we thus see that the classes of features observable upon the moon are not great in number3 they may be summed up as craters and their central cones1 mountain chains1 with occasional isolated peaks1 smooth plains1 with more or less of irregularity of surface1 and bright radiating streaks4 ,but when we come to study with higher powers the individual examples of each class we meet with considerable diversity4 ,this is especially the case with the craters1 which appear under very numerous variations of the one order of structure1 viz41 the ring-form4 ,a higher telescopic power shows us that not only do these craters exist of all magnitudes within a limit of largeness1 but seemingly with no limit of smallness1 but that in their structure and arrangement they present a great variety of points of difference4 ,some are seen to be considerably elevated above the surrounding surface1 others are basins hollowed out of that surface and with low surrounding ramparts2 some are merely like walled plains or amphitheatres with flat plateaux1 while the majority have their lowest point of hollowness considerably below the general level of the surrounding surface2 some are isolated upon the plains1 others are aggregated into a thick crowd1 and overlapping and intruding upon each other2 some have elevated peaks or cones in their centres1 and some are without these central cones1 while the plateaux of others again contain several minute craters instead2 some have their ramparts whole and perfect1 others have them breached or malformed1 and many have them divided into terraces1 especially on their inner sides4 ,in the plains1 what with a low power appeared smooth as a water surface becomes1 under greater magnification1 a rough and furrowed area1 here gently undulated and there broken into ridges and declivities1 with now and then deep rents or cracks extending for miles and spreading like river-beds into numerous ramifications4 ,craters of all sizes and classes are scattered over the plains2 these appear generally of a different tint to the surrounding surface1 for the light reflected from the plains has been observed to be slightly tinged with colour1 ,the tint is not the same in all cases3 one large sea has a dingy greenish tinge1 others are merely grey and some others present a pale reddish hue4 ,the cause of this diversity of colour is mysterious2 it has been supposed to indicate the existence of vegetation of some sort2 but this involves conditions that we know do not exist4 ,the mountains1 under higher magnification1 do not present such diversity of formation as the craters1 or at least the points of difference are not so apparent2 but they exhibit a plentiful variety of combinations4 ,there are a few perfectly isolated examples that cast long shadows over the plains on which they stand like those of a towering cathedral in the rising or setting sun4 ,sometimes they are collected into groups1 but mostly they are connected into stupendous chains4 ,in one of the grandest of these chains1 it has been estimated that a good telescope will show #cjjj mountains clustered together1 without approach to symmetrical order4 ,the scenery which they would present1 could we get any other than the 8bird's eye view0 to which we are confined1 must be imposing in the extreme1 far exceeding in sublime grandeur anything that the ,alps or the ,himalayas offer2 for while on the one hand the lunar mountains equal those of the earth in altitude1 the absence of an atmosphere1 and consequently of the effects produced thereby1 must give rise to alternations of dazzling light and black depths of shade combining to form panoramas of wild scenery that1 for want of a parallel on earth1 we may well call unearthly4 ,but we are debarred the pleasure of actually contemplating such pictures by the circumstance that we look down upon the mountain tops and into the valleys1 so that the great height and close aggregation of the peaks and hills are not so apparent4 ,to compare the lunar and terrestrial mountain scenery would be 8to compare the different views of a town seen from the car of a balloon1 with the more interesting prospects by a progress through the streets40 ,some of the peculiarities of the lunar scenery we have1 however1 endeavoured to realize in a subsequent ,chapter4 ,a high power gives us little more evidence than a low one upon the nature of the long bright streaks that radiate from some of the more conspicuous craters1 but it enables us to see that those streaks do not arise from any perceptible difference of level of the surface--that they have no very definite outline1 and that they do not present any sloping sides to catch more sunlight1 and thus shine brighter1 than the general surface4 ,indeed1 one great peculiarity of them is that they come out most forcibly where the sun is shining perpendicularly upon them2 hence they are best seen where the moon is at full1 and they are not visible at all at those regions upon which the sun is rising or setting4 ,we also see that they are not diverted by elevations in their path1 as they traverse in their course craters1 mountains1 and plains alike1 giving a slight additional brightness to all objects over which they pass1 but producing no other effect upon them4 ,to employ a commonplace simile1 they look as though1 after the whole surface of the moon had assumed its final configuration1 a vast brush charged with a whitish pigment had been drawn over the globe in straight lines radiating from a central point1 leaving its trail upon everything it touched1 but obscuring nothing4 ,whatever may be the cause that produces this brightness of certain parts of the moon without reference to configuration of surface1 this cause has not been confined to the formation of the radiating lines1 for we meet with many isolated spots1 streaks and patches of the same bright character4 ,upon some of the plains there are small areas and lines of luminous matter possessing peculiarities similar to those of the radiating streaks1 as regards visibility with the high sun1 and invisibility when the solar rays fall upon them horizontally4 ,some of the craters also are surrounded by a kind of aureole of this highly reflective matter4 ,a notable specimen is that called ,linn1 concerning which a great hue and cry about change of appearance and inferred continuance of volcanic action on the moon was raised some years ago4 ,this object is an insignificant little crater of about a mile or two in diameter1 in the centre of an ill-defined spot of the character referred to1 and about eight or ten miles in diameter4 ,with a low sun the crater alone is visible by its shadow2 but as the luminary rises the shadow shortens and becomes all but invisible1 and then the white spot shines forth4 ,these alternations1 complicated by variations of atmospheric condition1 and by the interpretations of different observers1 gave rise to statements of somewhat exaggerated character to the effect that considerable changes1 of the nature of volcanic eruptions1 were in progress in that particular region of the moon4 ,in the foregoing remarks we have alluded somewhat indefinitely to high powers2 and an enquiring but unastronomical reader may reasonably demand some information upon this point4 ,it might have been instructive to have cited the various details that may be said to come into view with progressive increases of magnification4 ,but this would be an all but impossible task1 on account of the varying conditions under which all astronomical observations must necessarily be made4 ,when we come to delicate tests1 there are no standards of telescopic power and definition4 ,assuming the instrument to be of good size and high optical character1 there is yet a powerful influant of astronomical definition in the atmosphere and its variable state4 ,upon two-thirds of the clear nights of a year the finest telescopes cannot be used to their full advantage1 because the minute flutterings resulting from the passage of the rays of light through moving strata of air of different densities are magnified just as the image in the telescope is magnified1 till all minute details are blurred and confused1 and only the grosser features are left visible4 ,and supposing the telescope and atmosphere in good state1 there is still an important point1 the state of the observer's eye1 to be considered4 ,after all it is the eye that sees1 and the best telescopic assistance to an untrained eye is of small avail4 ,the eye is as susceptible of education and development as any other organ2 a skilful and acute observer is to a mere casual gazer1 what a watchmaker would be to a ploughman1 a miniature painter to a whitewasher4 ,this fact is not generally recognized2 no man would think of taking in hand an engraver's burin1 and expecting on the instant to use it like an adept1 or of going to a smithy and without previous preparation trying to forge a horse-shoe4 ,yet do folks enter observatories with uneducated eyes1 and expect at once to realize all the wonderful things that their minds have pictured to themselves from the perusal of astronomical books4 ,we have over and over again remarked the dissatisfaction which attends the first looks of novices through a powerful telescope4 ,they anticipate immediately beholding wonders1 and they are disappointed at finding how little they can see1 and how far short the sight falls of what they had expected4 ,courtesy at times leads them to express wonder and surprise1 which it is easy to see is not really felt1 but sometimes honesty compels them to give expression to their disappointment4 ,this arises from the simple fact that their eyes are not fit for the work which is for the moment imposed upon them2 they know not what to look for1 or how to look for it4 ,the first essay at telescopic gazing1 like first essays generally1 serves but to teach us our incapability4 ,to a tutored eye a great deal is visible with a comparatively low power1 and practised observers strive to use magnifying powers as low as possible1 so as to diminish1 as far as may be1 the evils arising from an untranquil atmosphere4 ,with a power so small as #cj or #dj1 many exceedingly delicate details on the moon are visible to an eye that is familiar with them under higher powers4 ,with #bjj we may say that every ordinary detail will come out under favourable conditions2 but when minute points of structure1 mere nooks and corners as it were1 are to be scrutinised1 #cjj may be used with advantage4 ,another hundred diameters almost passes the practical limit4 ,unless the air be not merely fine1 but superfine1 the details become 8clothy0 and tremulous2 the extra points brought out by the increased power are then only caught by momentary glimpses1 of which but a very few are obtained during a lengthy period of persistent scrutiny4 ,we may set down #bej as the most useful1 and #cej the utmost effective power that can be employed upon the particular work of which we are treating4 ,could every detail on the moon be thoroughly and reliably represented as this amount of magnification shows it1 the result would leave little to be wished for4 ,but it may be asked by some1 what is the absolute effect of such powers as those we have spoken of1 in bringing the moon apparently nearer to our eyes8 and what is the actual size of the smallest object visible under the most favourable circumstances8 ,a linear mile upon the moon corresponds to an angular interval of #jhg of a second2 this refers to regions about the centre of the disc2 near the circumference the foreshortening makes a difference1 very great as the edge is approached4 ,perhaps the smallest angle that the eye can without assistance appreciate is half a minute2 that is to say1 an object that subtends to the eye an arc of less than a half a minute can scarcely be seen4#g ,since there are #fj seconds in a minute1 it follows that we must magnify a spot a second in diameter upon the moon thirty times before we can see it2 and since a second represents rather more than a mile1 really about #bjjj yards1 on the moon1 as seen from the earth1 the smallest object visible with a power of #cj will be this number of yards in diameter or breadth4 ,to see an object #bjj yards across1 we should require to magnify it #cjj times1 and this would only bring it into view as a point2 #bj yards would require a power of #cjjj1 and #a yard #fj1jjj to effect the same thing4 ,since1 as we have said1 the highest practicable power with our present telescopes1 and at ordinary terrestrial elevations1 is #cej1 or for an extreme say #djj1 it is evident that the minutest lunar object or detail of which we can perceive as a point must measure about #aej yards3 to see the form of an object1 so as to discriminate whether it be round or square1 it would require to be probably twice this size2 for it may be safely assumed that we cannot perceive the outline of an object whose average breadth subtends a less angle than a minute4 ,arago put this question into another shape3--,the moon is distant from us #bcg1jjj miles 7mean74 ,a magnifying power of a thousand would show us the moon as if she were distant #bcg miles from the naked eye4 #bjjj would bring her within #aah miles4 #djjj 0 0 0 #ei 0 #fjjj 0 0 0 #ci 0 ,mont ,blanc is visible to the naked eye from ,lyons1 at the distance of about #ajj miles2 so that to see the mountains of the moon as ,mont ,blanc is seen from ,lyons would require the impracticable power of #bejj4 ,,chapter ,,vii4 ,,topography ,,of ,,the ,,moon4 ,it is scarcely necessary to seek the reasons which prompted astronomers1 soon after the invention of the telescope1 to map the surface features of the moon4 ,they may have considered it desirable to record the positions of the spots upon her disc1 for the purpose of facilitating observations of the passage of the earth's shadow over them in lunar eclipses2 or they may have been actuated by a desire to register appearances then existing1 in order that if changes took place in after years these might be readily detected4 ,scheiner was one of the earliest of lunar cartographers2 he worked about the middle of the seventeenth century2 but his delineations were very rough and exaggerated4 ,better maps--the best of the time1 according to an old authority--were engraved by one ,mellan1 about the years #afcd or #afce4 ,at about the same epoch1 ,langreen and ,hevelius were working upon the same subject4 ,langreen executed some thirty maps of portions of the moon1 and introduced the practice of naming the spots after philosophers and eminent men4 ,hevelius spent several years upon his task1 the results of which he published in a bulky volume containing some #ej maps of the moon in various phases1 and accompanied by #ejj pages of letter-press4 ,he rejected ,langreen's system of nomenclature1 and called the spots after the seas and continents of the earth to which he conceived they bore resemblance4 ,riccioli1 another selenographer1 whose map was compiled from observations made by ,grimaldi1 restored ,langreen's nomenclature1 but he confined himself to the names of eminent astronomers1 and his system has gained the adhesion of the map-makers of later times4 ,cassini prepared a large map from his own observations1 and it was engraved about the year #afib4 ,it appears to have been regarded as a standard work1 for a reduced copy of it was repeatedly issued with the yearly volumes of the ,connaissance des ,temps1 7the 8,nautical ,almanac0 of ,france7 some time after its publication4 ,these small copies have no great merit3 the large copper plate of the original was1 we are told by ,arago1 who received the statement from ,bouvard1 sold to a brazier by a director of the ,french ,government ,printing-,office1 who thought proper to disembarrass the stores of that establishment1 by ridding them of what he considered lumber6 ,la ,hire1 ,mayer1 and ,lambert1 followed during the succeeding century1 in this branch of astronomical delineation4 ,at the commencement of the present century1 the subject was very earnestly taken up by the indefatigable ,schroeter1 who1 although he does not appear to have produced a complete map1 produced a topograph of the moon in a large series of partial maps and drawings of special features4 ,schroeter was a fine observer1 but his delineations show him to have been an indifferent draughtsman4 ,some of his drawings are but the rudest representations of the objects he intended to depict2 many of the bolder features of conspicuous objects are scarcely recognizable in them4 ,a bad artist is as likely to mislead posterity as a bad historian1 and it cannot be surprising if observers of this or future generations1 accepting ,schroeter's drawings as faithful representations1 should infer from them remarkable changes in the lunar details4 ,it is much to be regretted that ,schroeter's work should be thus depreciated4 ,lohrman of ,dresden1 was the next cartographer of the moon2 in #ahbd he put forth a small but very excellent map of #ae inches diameter1 and published a book of descriptive text1 accompanied by sectional charts of particular areas4 ,his work1 however1 was eclipsed by the great one which we owe to the joint energy of ,,mm4 ,beer and ,maedler1 and which represents a stupendous amount of observing work carried on during several years prior to #ahcf1 the date of their publication4 ,the long and patient labour bestowed upon their map and upon the measures on which it depends1 deserve the highest praise which those conversant with the subject can bestow1 and it must be very long before their efforts can be superseded4 ,beer and ,maedler's map has a diameter of #cg inches3 it represents the phase of the moon visible in the condition of mean libration4 ,the details were charted by a careful process of triangulation4 ,the disc was first divided into 8triangles of the first order10 the points of which 7conspicuous craters7 were accurately laid down by reference to the edges of the disc3 one hundred and seventy-six of these triangles1 plotted accurately upon an orthographic projection of the hemisphere1 formed the reliable basis for their charting work4 ,from these a great number of 8points of the second order0 were laid down1 by measuring their distance and angle of position with regard to points first established4 ,the skeleton map thus obtained was filled up by drawings made at the telescope3 the diameters of the measureable craters being determined by the micrometer4 ,beer and ,maedler also measured the heights of one thousand and ninety-five lunar mountains and crater-summits3 the resulting measures are given in a table contained in the comprehensive text-book which accompanies their map4 ,these heights are found by one of two methods1 either by measuring the length of the shadow which the object casts under a known elevation of the sun above its horizon1 or by measuring the distance between the illuminated point of the mountain and the 8terminator0 in the following manner4 ,in the annexed figure 7,fig4 #ae7 let the circle represent the moon and ,m a mountain upon it3 let ,s ,a be the line of direction of the sun's rays1 passing the normal surface of the moon at ,a and just tipping the mountain top4 ,a will be the terminator1 and there will be darkness between it and the star-like mountain summit ,m4 ,the distance between ,a and ,m is measured3 the distance ,a ,b is known1 for it is the moon's radius4 ,and since the line ,s ,m is a tangent to the circle the angle ,b ,a ,m is a right angle4 ,we know the length of its two sides ,,ab1 ,,am1 and we can therefore by the known properties of the right-angled triangle find the length of the hypothenuse ,,bm3 and since ,,bm is made up of the radius ,,ba plus the mountain height1 we have only to subtract the moon's radius from the ascertained whole length of the hypothenuse and we have the height of the mountain4 ,,mm4 ,beer and ,maedler exhibited their measures in ,french toises3 in the heights we shall have occasion to quote1 these have been turned into ,english feet1 upon the assumption that the toise is equal to #fci ,english feet4 ,the nomenclature of lunar features adopted by ,beer and ,maedler is that introduced by ,riccioli3 mountains and features hitherto undistinguished were named by them after ancient and modern philosophers1 in continuance of ,riccioli's system1 and occasionally after terrestrial features4 ,some minute objects in the neighbourhood of large and named ones were included under the name of the large one and distinguished by ,greek or ,roman letters4 ,illustration3 ,fig4 #ae4 ,illustration3 ,,plate ,,iv4 ,,picture ,,map ,,of ,,the ,,moon4 ,illustration3 ,,plate ,v4 ,skeleton ,map of ,moon ,to ,accompany ,picture ,map1 ,chap4 ,,vii ,the excellent map resulting from the arduous labours of these astronomers is simply a map3 it does not pretend to be a picture4 ,the asperities and depressions are symbolized by a conventional system of shading and no attempt is made to exhibit objects as they actually appear in the telescope4 ,a casual observer comparing details on the map with the same details on the moon itself would fail to identify or recognize them except where the features are very conspicuous4 ,such an observer would be struck by the shadows by which the lunar objects reveal themselves3 he would get to know them mostly by their shadows1 since it is mainly by those that their forms are revealed to a terrestrial observer4 ,but such a map as that under notice indicates no shadows1 and objects have to be identified upon it rather by their positions with regard to one another or to the borders of the moon than by any notable features they actually present to view4 ,this inconvenience occurred to us in our early use of ,beer and ,maedler's chart1 and we were induced to prepare for ourselves a map in which every object is shown somewhat1 if imperfectly1 as it actually appears at some period of a lunation4 ,this was done by copying ,beer and ,maedler's outlines and filling them up by appropriate shading4 ,to do justice to our task we enlarged our map to a diameter of six feet4 ,upon a circle of this diameter the positions and dimensions of all objects were laid down from the ,german original4 ,then from our own observations we depicted the general aspect of each object3 and we so adjusted the shading that all objects should be shown under about the same angle of illumination--a condition which is never fulfilled upon the moon itself1 but which we consider ourselves justified in exhibiting for the purpose of conveying a fair impression of how the various lunar objects actually appear at some one or other part of a lunation4 ,the picture-map thus produced has been photographed to the size convenient for this work3 and in order to make it available for the identification of such objects as we may have occasion to refer to1 we have placed around it a co-ordinate scale of arbitrary divisions by which any object can be found as by the latitude and longitude divisions upon a common geographical map4 ,we have also prepared a skeleton map which includes the more conspicuous objects1 and which faces the picture map 7,plates ,,iv4 and ,v47 ,the numbers on the skeleton map are those given in the second column of the accompanying table4 ,the table also gives the co-ordinate positions of the various craters1 the names of which are1 for convenience of reference1 printed in alphabetical order4 ,name4 ,number4 ,map ,ordinates4 ,abulfeda #ajg #cjj #abjg ,agrippa #aea #cab #aajj ,airy #ic #cdg #abcj ,albategnius #aji #cee #aaig ,aliacensis #fa #ceh #acaj ,almanon #id #bij #abbc ,alpetragius #ib #djh #abbd ,alphonsus #aaj #cif #abji ,apianus #fb #ccf #abic ,apollonius #aed #fe #ajie ,arago #aeb #bdg #ajhg ,archimedes #aia #djc #ieh ,aristarchus #agf #fbc #iib ,aristillus #aij #cgj #icc ,aristotle #bji #cjj #hdf ,arzachael #hd #cie #abdj ,atlas #bbh #bjg #hff ,autolycus #ahi #cfh #iee ,azophi #gf #cjg #abfh ,bacon #ag #cbe #adbj ,baily #bjg #bfj #hed ,barocius #cd #cah #ache ,bessel #agi #bgd #ajja ,bettinus #aa #dhh #addi ,bianchini #bae #eaf #hfc ,billy #aba #fdc #abad ,blancanus #ab #dcg #addh ,bonpland #aaj #dhe #aagf ,borda #ef #aeb #acaj ,boscovich #afj #caa #ajfh ,bouvard #dj #fff #acdc ,briggs #aif #fhj #igb ,bullialdus #hf #eja #abee ,burg #bjf #bee #hge ,calippus #aii #cbd #ijc ,campanus #ga #ebc #abij ,capella #ajd #agh #aahj ,capuanus #dc #eje #acbh ,casatus #g #dcg #adgj ,cassini #bjj #cee #hig ,catherina #ie #bdg #abdj ,cavalerius #add #gab #ajie ,cavendish #hh #fce #abgd ,cichus #dd #dgc #acbh ,clavius #ac #dah #adce ,cleomides #ahc #ajg #igj ,colombo #ih #abh #abbg ,condamine #bad #dhg #hdb ,condorcet #afd #de #ajdg ,copernicus #adg #dih #ajgj ,cyrillus #if #bce #abac ,damoiseau #abd #fib #aagb ,davy #aac #dcb #aaih ,deambrel #abi #bfh #aace ,delisle #aie #eeg #ieb ,descartes #ajf #bhe #aaic ,diophantus #aid #eee #ifc ,doppelmayer #gj #ehf #abif ,encke #adj #eig #aajf ,endymion #bbg #bjf #hch ,epigenes #bbc #cij #gie ,erastothenes #afh #ddf #ajdj ,eudoxus #bjh #big #hhj ,fabricius #ce #bjj #acfh ,fernelius #cg #cea #acdh ,firmicus #aef #eh #ajgg ,flamsteed #abf #fbh #aade ,fontana #abb #fei #abcj ,fontenelle #bba #dcj #hac ,fourier #fg #fbe #acjg ,fracastorius #gh #bje #abgj ,furnerius #eb #aag #accj ,gambart #ach #dgb #aabb ,gartner #bbd #bfe #hbc ,gassendi #ij #eig #abcc ,gauricus #df #dce #acbe ,gauss #bja #ajc #ijc ,gay ,lussac #afi #eja #ajch ,geber #hc #bif #abdh ,geminus #ahg #acj #icj ,grard #bah #fcg #hhh ,goclenius #aja #aah #aahe ,godin #ace #cac #aaag ,grimaldi #abe #gjh #aafc ,gruemberger #f #dad #adeh ,guerik #aad #dfe #aaif ,guttemberg #ajb #aci #aahc ,inghirami #bg #fac #achi ,isidorus #ajc #afg #aahj ,kant #aje #beh #aahe ,kepler #adf #fjj #ajhj ,kies #gb #dig #abhh ,kircher #aj #dge #adeh ,klaproth #h #dce #adfg ,la ,caille #gd #cge #abfh ,lagrange #fh #fgj #acac ,la ,hire #agg #edc #iic ,lalande #aag #dcd #aaec ,lambert #aic #dif #igh ,landsberg #abg #edj #aacj ,langreen #ajj #fc #aagg ,letronne #abj #fbj #aaij ,licetus #ba #cda #acif ,lichtenberg #aig #ffe #idi ,linnus #ahh #cag #ieg ,littrow #ahe #bje #iid ,lohrman #adc #gac #aabh ,longomontanus #bc #deg #adjf ,lubiniezky #ia #eac #abce ,macrobius #ahb #acg #ajjb ,maginus #bb #djj #adjd ,mairan #bag #efg #hie ,manilius #afg #cbb #ajci ,manzinus #d #cac #adfj ,maraldi #aha #ahf #ajjh ,marius #aga #fej #ajee ,maskelyne #acb #aie #aaaj ,mason #bjd #bcg #hhh ,maupertius #bac #dhg #heh ,maurolycus #cc #cah #acgj ,menelaus #afe #bhc #ajcj ,mercator #fe #ead #acjb ,mersenius #hi #fag #abeg ,messala #bjb #adj #ije ,messier #aca #ajh #aadj ,metius #cf #ahh #ajei ,moretus #e #cie #adfe ,moesting #abh #daf #aacb ,neander #eg #ahg #acaj ,nearchus #ah #bfh #adbj ,newton #a #daj #adgg ,nonius #di #cfe #accb ,olbers #agb #gcj #ajgg ,pallas #adi #chf #ajie ,parrot #ajh #ceh #abaf ,petavius #hj #ie #abge ,phocylides #be #eee #adaf ,piazzi #da #fej #acce ,picard #afc #hc #ajdg ,piccolomini #eh #bag #acaj ,pico #baa #dai #hgc ,pitatus #fc #dda #acjb ,plana #bje #bdh #hhh ,plato #baj #dah #hdh ,playfair #ge #cce #abge ,pliny #afe #bdb #ajcd ,poisson #fj #cbh #acaj ,polybius #hb #bde #abef ,pontanus #ei #bij #acjb ,posidonius #ahf #bbb #idc ,proclus #afb #aad #ajde ,ptolemy #aaa #cie #aahb ,purbach #gc #chg #abhd ,pythagoras #bbj #ecj #hab ,pytheas #agh #dig #ajjd ,ramsden #db #ebi #acbe ,reamur #aah #cgc #aadf ,reiner #ade #fgc #ajhe ,reinhold #aci #eae #aaab ,repsold #bai #fjb #heg ,rheita #ea #afa #acdb ,riccioli #adb #gbg #aach ,riccius #ej #bcg #acce ,ritter #acd #bfj #aaaf ,roemer #ahd #ahc #igf ,ross #afa #bej #ajec ,sabine #acc #bej #aabj ,sacrobosco #gg #bge #abgg ,santbech #gi #aeg #abfh ,saussure #ca #cif #acgg ,scheiner #ad #dee #adce ,schickard #bh #eij #acge ,schiller #bd #eac #adaj ,schroeter #acg #dbc #aajg ,schubert #aee #bc #aajh ,segner #af #eac #adce ,seleucus #agd #fij #iih ,sharp #baf #edb #hgg ,short #b #cig #adgd ,silberschlag #aeg #cbj #ajha ,simpelius #c #ceh #adgg ,snell #ee #aac #abif ,soemmering #acf #dbh #aabb ,stadius #adh #def #ajgj ,stevinus #ec #aai #acjg ,stoefler #cb #cef #acfh ,strabo #bbf #bcb #haf ,struve #bjc #ahc #hhg ,taruntius #aec #aag #ajij ,taylor #acj #bgf #aafb ,thales #bbe #bdc #hah ,thebit #he #djh #abfh ,theophilus #ig #bbc #abjj ,timus #bbb #chc #hjh ,timocharis #aib #dea #igj ,tobias ,mayer #agj #ede #ajcj ,triesnecker #aej #cee #ajih ,tycho #cj #dcj #adbc ,ukert #aei #cga #ajge ,vasco de ,gama #agc #gbh #ajdi ,vendelinus #ii #fh #abaf ,vieta #fi #fdc #abig ,vitello #ff #eeh #acjg ,vitruvius #ahj #bja #ajbj ,vlacq #ai #bej #adja ,zuchius #ae #ejg #addb ,the strong family likeness pervading the craters of the moon renders it unnecessary that we should attempt a description of each one of them or even of one in twenty4 ,we have1 however1 thought that a few remarks upon the salient features of a few of the most important may be acceptable in explanation of our illustrative plates2 and what we have to say of the few may be taken as representative of the many4 ,,copernicus1 #adg--7dih--ajgj74 ,plate ,,viii4 ,this may deservedly be considered as one of the grandest and most instructive of lunar craters4 ,although its vast diameter 7#df miles7 is exceeded by others1 yet1 taken as a whole1 it forms one of the most impressive and interesting objects of its class4 ,its situation1 near the centre of the lunar disc1 renders all its wonderful details1 as well as those of its immediately surrounding objects1 so conspicuous as to establish it as a very favourite object4 ,its vast rampart rises to upwards of #ab1jjj feet above the level of the plateau1 nearly in the centre of which stands a magnificent group of cones1 three of them attaining the height of upwards of #bdjj feet4 ,the rampart is divided by concentric segmental terraced ridges1 which present every appearance of being enormous landslips1 resulting from the crushing of their over-loaded summits1 which have slid down in vast segments and scattered their dbris on to the plateau4 ,corresponding vacancies in the rampart may be observed from whence these prodigious masses have broken away4 ,the same may be noticed1 although in a somewhat modified degree1 around the exterior of the rampart4 ,in order to approach a realization of the sublimity and grandeur of this magnificent example of a lunar volcanic crater1 our reader would do well to endeavour to fix his attention on its enormous magnitude and attempt to establish in his mind's eye a correct conception of the scale of its details as well as its general dimensions1 which1 as they so prodigiously transcend those of the largest terrestrial volcanic craters1 require that our ideas as to magnitude of such objects should be1 so to speak1 educated upon a special standard4 ,it is for this reason we are anxious our reader1 when examining our illustrations1 should constantly refer the objects represented in them to the scale of miles appended to each plate1 otherwise a just and true conception of the grandeur of the objects will escape him4 ,copernicus is specially interesting1 as being evidently the result of a vast discharge of molten matter which has been ejected at the focus or centre of disruption of an extensively upheaved portion of the lunar crust4 ,a careful examination of the crater and the district around it1 even to the distance of more than #ajj miles on every side1 will supply unmistakable evidence of the vast extent and force of the original disruption1 manifested by a wonderfully complex reticulation of bright streaks which diverge in every direction from the crater as their common centre4 ,these streaks do not appear on our plate1 nor are they seen upon the moon except at and near the full phase4 ,they show conspicuously1 however1 by their united lustre on the full moon1 ,plate ,,iii4 ,every one of those bright streaks1 we conceive1 is a record of what was originally a crack or chasm in the solid crust of the moon1 resulting from some vastly powerful upheaving agency over the site of whose focus of energy ,copernicus stands4 ,the cracking of the crust must have been followed by the ejection of subjacent molten matter up through the reticulated cracks2 this1 spreading somewhat on either side of them1 has left these bright streaks as a visible record of the force and extent of the upheaval2 while at the focus of disruption from whence the cracks diverge1 the grand outburst appears to have taken place1 leaving ,copernicus as its record and result4 ,many somewhat radial ridges or spurs may be observed leading away from the exterior banks of the great rampart4 ,these appear to be due to the more free egress which the extruded matter would find near the focus of disruption4 ,the spur-ridges may be traced fining away for fully #ajj miles on all sides1 until they become such delicate objects as to approach invisibility4 ,several vast open chasms or cracks may be observed around the exterior of the rampart4 ,they appear to be due to some action subsequent to the formation of the great crater--probably the result of contraction on the cooling of the crust1 or of a deep-seated upheaval long subsequent to that which resulted in the formation of ,copernicus itself1 as they intersect objects of evidently prior formation4 ,under circumstances specially favourable for 8fine vision10 for upwards of #gj miles on all sides around ,copernicus1 myriads of comparatively minute but perfectly-formed craters may be observed4 ,the district on the south-east side is specially rich in these wonderfully thickly-scattered craters1 which we have reason to suppose stand over or upon the reticulated bright streaks2 but1 as the circumstances of illumination which are requisite to enable us to detect the minute craters are widely adverse to those which render the bright streaks visible1 namely1 nearly full moon for the one and gibbous for the other1 it is next to impossible to establish the fact of coincidence of the sites of the two by actual simultaneous observation4 ,at the east side of the rampart1 multitudes of these comparatively minute craters may also be detected1 although not so closely crowded together as those on the west side2 but among those on the east may be seen myriads of minute prominences roughening the surface2 on close scrutiny these are seen to be small mounds of extruded matter which1 not having been ejected with sufficient energy to cause the erupted material to assume the crater form around the vent of ejection1 have simply assumed the mound form so well known to be the result of volcanic ejection of moderate force4 ,were we to select a comparatively limited portion of the lunar surface abounding in the most unmistakable evidence of volcanic action in every variety that can characterize its several phases1 we could not choose one yielding in all respects such instructive examples as ,copernicus and its immediate surroundings4 ,,gassendi1 #ij--7eig--abcc74 ,frontispiece4 ,an interesting crater about #ed miles diameter2 the height of the most elevated portion of the surrounding wall from the plateau being about #ifjj feet4 ,the centre is occupied by a group of conical mountains1 three of which are most conspicuous objects and rise to nearly #gjjj feet above the level of the plateau4 ,as in other similar cases1 these central mountains are doubtless the result of the expiring effort of the eruption which had formed the great circular wall of the crater4 ,the plateau is traversed by several deep cracks or chasms nearly one mile wide4 ,both the interior and exterior of the wall of the crater are terraced with the usual segmental ridges or landslips4 ,a remarkable detached portion of the interior bank is to be seen on the east side1 while on the west exterior of the wall may be seen an equally remarkable example of an outburst of lava subsequent to the formation of the wall or bank of the crater2 it is of conical form and cannot fail to secure the attention of a careful observer4 ,interpolated on the north wall of the crater may be seen a crater of about #ah miles diameter which has burst its bank in towards the great crater1 upon whose plateau the lava appears to have discharged itself4 ,the neighbourhood of ,gassendi is diversified by a vast number of mounds and long ridges of exudated matter1 and also traversed by enormous chasms and cracks1 several of which exceed one mile wide and are fully #ajj miles in length1 and1 as is usual with such cracks1 traverse plain and mountain alike1 disregarding all surface inequalities4 ,numbers of small craters are scattered around2 the whole forming an interesting and instructive portion of the lunar surface4 ,,eudoxus1 #bjh 7#big--hhj71 and ,,aristotle1 #bji 7#cjj--hdf74 ,plate ,x4 ,two gigantic craters1 ,eudoxus being nearly #ce miles in diameter and upwards of #aa1jjj feet deep1 while ,aristotle is about #dh miles in diameter1 and about #aj1jjj feet deep 7measuring from the summit of the rampart to the plateau74 ,these two magnificent craters present all the true volcanic characteristics in a remarkable degree4 ,the outsides as well as the insides of their vast surrounding walls or banks display on the grandest scale the landslip feature1 the result of the over-piling of the ejected material1 and the consequent crushing down and crumbling of the substructure4 ,the true eruptive character of the action which formed the craters is well evinced by the existence of the groups of conical mountains which occupy the centres of their circular plateaux1 since these conical mountains1 there can be little doubt1 stand over what were once the vents from whence the ejected matter of the craters was discharged4 ,on the west side of these grand craters may be seen myriads of comparatively minute ones 7we use the expression 8comparatively minute10 although most of them are fully a mile in diameter74 ,so thickly are these small craters crowded together1 that counting them is totally out of the question2 in our original notes we have termed them 8,froth craters0 as the most characteristic description of their aspect4 ,the exterior banks of ,aristotle are characterized by radial ridges or spurs3 these are most probably the result of the flowing down of great currents of very fluid lava4 ,to the east of the craters some very lofty mountains of exudation may be seen1 and immediately beyond them an extensive district of smaller mountains of the same class1 so thickly crowded together as under favourable illumination to present a multitude of brilliant points of light contrasted by intervening deep shade4 ,on the west bank of ,aristotle a very perfect crater may be seen1 #bg miles in diameter1 having all the usual characteristic features4 ,about #dj miles to the east of ,eudoxus there is a fine example of a crack or fissure extending fully #ej miles--#cj miles through a plain1 and the remaining #bj miles cutting through a group of very lofty mountains4 ,this great crack is worthy of attention1 as giving evidence of the deep-seated nature of the force which occasioned it1 inasmuch as it disregards all surface impediments1 traversing plain and group of mountains alike4 ,there are several other features in and around these two magnificent craters well worthy of careful observation and scrutiny1 all of them excellent types of their respective classes4 ,,triesneker1 #aej 7#cee--ajih74 ,plate ,,xi4 ,a fine example of a normal lunar volcanic crater1 having all the usual characteristic features in great perfection4 ,its diameter is about #bj miles1 and it possesses a good example of the central cone and also of interior terracing4 ,the most notable feature1 however1 in connection with this crater1 and on account of which we have chosen it as a subject for one of our illustrations1 is the very remarkable display of chasms or cracks which may be seen to the west side of it4 ,several of these great cracks obviously diverge from a small crater near the west external bank of the great one1 and they subdivide or branch out1 as they extend from the apparent point of divergence1 while they are crossed or intersected by others4 ,these cracks or chasms 7for their width merits the latter appellation7 are nearly one mile broad at the widest part1 and after extending to fully #ajj miles1 taper away till they become invisible4 ,although they are not test objects of the highest order of difficulty1 yet to see them with perfect distinctness requires an instrument of some perfection and all the conditions of good vision4 ,when such are present1 a keen and practised eye will find many details to rivet its attention1 among which are certain portions of the edges of these cracks or chasms which have fallen in and caused interruptions to their continuity4 ,,theophilus1 #ig 7#bbc--abjj74 ,,cyrillus1 #if 7#bce--abac74 ,,catharina1 #ie 7#bdg--abdj74 ,plate ,,xii4 ,these three magnificent craters form a very conspicuous group near the middle of the south-east quarter of the lunar disc4 ,their respective diameters and depths are as follows3-- ,theophilus1 #fd miles diameter2 depth of plateau from summit of crater wall1 #af1jjj feet2 central cone1 #ebjj feet high4 ,cyrillus1 #fj miles diameter2 depth of plateau from summit of crater wall1 #ae1jjj feet2 central cone1 #ehjj feet high4 ,catharina1 #fe miles diameter2 depth of plateau from summit of crater wall1 #ac1jjj feet2 centre of plateau occupied by a confused group of minor craters and dbris4 ,each of these three grand craters is full of interesting details1 presenting in every variety the characteristic features which so fascinate the attention of the careful observer of the moon's wonderful surface1 and affording unmistakable evidence of the tremendous energy of the volcanic forces which at some inconceivably remote period piled up such gigantic formations4 ,theophilus by its intrusion within the area of ,cyrillus shows in a very striking manner that it is of comparatively more recent formation than the latter crater4 ,there are many such examples in other parts of the lunar disc1 but few of so very distinct and marked a character4 ,the flanks or exterior banks of ,theophilus1 especially those on the west side1 are studded with apparently minute craters1 all of which when carefully scrutinized are found to be of the true volcanic type of structure2 and minute as they are1 by comparison1 they would to a beholder close to them appear as very imposing objects2 but so gigantic are the more notable craters in the neighbourhood1 that we are apt to overlook what are in themselves really large objects4 ,it is only by duly training the mind1 as we have previously urged1 so as ever to keep before us the vast scale on which the volcanic formations of the lunar surface are displayed1 that we can do them the justice which their intrinsic grandeur demands4 ,we trust that our illustrations may in some measure tend to educate the mind's eye1 so as to derive to the full the tranquil enjoyment which results from the study of the manifestation of one of the ,creator's most potent agencies in dealing with the materials of his worlds1 namely1 volcanic force4 ,so rich in wonderful features and characteristic details is this magnificent group and its neighbourhood1 that a volume might be filled in the attempt to do justice1 by description1 to objects so full of suggestive subject for study4 ,,thebit1 #he--7djh--abfh74 ,a crater about #cb miles in diameter and about #igjj feet deep1 devoid of a central cone4 ,it appears on the upper part and near the middle of ,plate ,,xiii4 ,the plateau has five minute craters upon it4 ,on the east outside are two small craters1 the lesser of which1 about #bge miles diameter1 has a central cone4 ,we specially note this fact1 because it is the smallest crater but one in which we have detected a central cone3 no doubt1 however1 many smaller craters possess this unmistakable stamp of true volcanic origin1 but so minute are the specks of light which the central cones of such very small craters reflect1 that they fail to be visible to us4 ,east of ,thebit is a very remarkable straight cliff #fj miles long by about #ajjj feet high1 called by some observers the 8,railway10 and apparently the result either of an upheaval or of a down-sinking of the surface of the circular area across whose diameter it stretches4 ,under moderate magnifying power1 this cliff appears straight1 but with higher power and under favourable conditions1 its face is seen to be serrated1 and along the upper edge may be detected several very minute craters4 ,a more conspicuous small crater is seen at the north end of the cliff4 ,to the east of the cliff nearly opposite the centre are two craters1 from the east side of the larger of which proceeds a fine crack parallel to the cliff and passing through a dome-shaped hill of low eminence4 ,,plato1 #baj 7#dah--hah74 ,plate ,,xiv4 ,this crater1 besides being a conspicuous object on account of its great diameter1 has many interesting details in and around it requiring a fine instrument and favourable circumstances to render them distinctly visible4 ,the diameter of the crater is #gj miles2 the surrounding wall or rampart varies in height from #djjj to upwards of #hjjj feet1 and is serrated with noble peaks which cast their black shadows across the plateau in a most picturesque manner1 like the towers and spires of a great cathedral4 ,reference to our illustration will convey a very fair idea of this interesting appearance4 ,on the north-east inside of the circular wall or rampart may be observed a fine example of landslip1 or sliding down of a considerable mass of the interior side of the crater's wall4 ,the landslip nature of this remarkable detail is clearly established by the fact of the bottom edge of the downslipped mass projecting in towards the centre of the plateau to a considerable extent4 ,other smaller landslip features may be seen1 but none on so grand and striking a scale as the one referred to4 ,a number of exceedingly minute craters may be detected on the surface of the plateau4 ,the plateau itself is remarkable for its low reflective power1 which causes it to look like a dingy spot when ,plato is viewed with a small magnifying power4 ,the exterior of the crater wall is remarkable for the rugged character of its formation1 and forms a great contrast in that respect to the comparatively smooth unbroken surface of the plateau1 which by the way is devoid of a central cone4 ,the surrounding features and objects indicated in our illustration are of the highest interest1 and a few of them demand special description4 ,,the ,,valley ,,of ,,the ,,alps 7#cgj--hfj74 ,plate ,,xiv4 ,this remarkable object lays somewhat diagonally to the west of ,plato2 when seen with a low magnifying power 7#hj or #ajj71 it appears as a rut or groove tapering towards each extremity4 ,it measures upwards of #ge miles long by about six miles wide at the broadest part4 ,when examined under favourable circumstances1 with a magnifying power of from #bjj to #cjj1 it is seen to be a vast flat-bottomed valley bordered by gigantic mountains1 some of which attain heights upwards of #aj1jjj feet2 towards the south-east of this remarkable valley1 and on both sides of it1 are groups of isolated mountains1 several of which are fully #hjjj feet high4 ,this flat-bottomed valley1 which has retained the integrity of its form amid such disturbing forces as its immediate surroundings indicate1 is one of the many structural enigmas with which the lunar surface abounds4 ,to the north-west of the valley a vast number of isolated mounds or small mountains of exudation may be seen2 so numerous are they as to defy all attempts to count them with anything like exactness2 and among them1 a power of #bjj to #cjj will enable an observer1 under favourable circumstances1 to detect vast numbers of small but perfectly-formed craters4 ,,pico1 #baa 7#dai--hgc74 ,plate ,,xiv4 ,this is one of the most interesting examples of an isolated volcanic 8mountain of exudation10 and it forms a very striking object when seen under favourable circumstances4 ,its height is upwards of #hjjj feet1 and it is about three times as long at the base as it is broad4 ,the summit is cleft into three peaks1 as may be ascertained by the three-peaked shadow it casts on the plain4 ,five or six minute craters of very perfect form may be detected close to the base of this magnificent mountain4 ,there are several other isolated peaks or mountains of the same class within #cj or #dj miles of it which are well worthy of careful scrutiny1 but ,pico is the master of the situation1 and offers a glorious subject for realizing a lunar day-dream in the mind's eye1 if we can only by an effort of imagination conceive its aspect under the fiercely brilliant sunshine by which it is illuminated1 contrasted with the intensely black lunar heavens studded with stars shining with a steady brightness of which1 by reason of our atmosphere intervening1 we can have no adequate conception save by the aid of a well-directed imagination4 ,,tycho1 #cj 7#dcj--adbc74 ,plate ,,xvi4 ,this magnificent crater1 which occupies the centre of the crowded group in our ,plate1 is #ed miles in diameter1 and upwards of #af1jjj feet deep1 from the highest ridge of the rampart to the surface of the plateau1 whence rises a grand central cone #ejjj feet high4 ,it is one of the most conspicuous of all the lunar craters1 not so much on account of its dimensions as from its occupying the great focus of disruption from whence diverge those remarkable bright streaks1 many of which may be traced over #ajjj miles of the moon's surface1 disregarding in their course all interposing obstacles4 ,there is every reason to conclude that ,tycho is an instance of a vast disruptive action which rent the solid crust of the moon into radiating fissures1 which were subsequently occupied by extruded molten matter1 whose superior luminosity marks the course of the cracks in all directions from the crater as their common centre of divergence4 ,so numerous are these bright streaks when examined by the aid of the telescope1 and they give to this region of the moon's surface such an extra degree of luminosity1 that1 when viewed as a whole1 their locality can be distinctly seen at full moon by the unassisted eye as a bright patch of light on the southern portion of the disc4 7,see ,plate ,,iii47 ,the causative origin of the streaks is discussed and illustrated in ,chapter ,,xi4 ,the interior of this fine crater presents striking examples of the concentric terrace-like formations that we have elsewhere assigned to vast landslip actions4 ,somewhat similar concentric terraces may be observed in other lunar craters2 some of these1 however1 appear to be the results of some temporary modification of the ejective force1 which has caused the formation of more or less perfect inner ramparts3 what we conceive to be true landslip terraces are always distinguished from these by their more or less fragmentary character4 ,on reference to ,plate ,,iii41 showing the full moon1 a very remarkable and special appearance will be observed in a dingy district or zone immediately surrounding the exterior of the rampart of ,tycho1 and of which we venture to hazard what appears to us a rational explanation3 namely1 that as ,tycho may be considered to have acted as a sort of safety-valve to the rending and ejective force which caused1 in the first instance1 the cracking of this vast portion of the moon's crust--the molten matter that appears to have been forced up through these cracks1 on finding a comparatively free exit by the vent of ,tycho1 so relieved the district immediately around him as to have thereby reduced1 in amount1 the exit of the molten matter1 and so left a zone comparatively free from the extruded lava which1 according to our view of the subject1 came up simultaneously through the innumerable fissures1 and1 spreading sideways along their courses1 left everlasting records of the original positions of the radiating cracks in the form of the bright streaks which we now behold4 8,,wargentin10 #bf 7#ege--adjb74 ,plate ,,xvii4 ,this object is quite unique of its kind--a crater about #ec miles across that to all appearance has been filled to the brim with lava that has been left to consolidate4 ,there are evidences of the remains of a rampart1 especially on the south-west portion of the rim4 ,the general aspect of this extraordinary object has been not unaptly compared to a 8thin cheese40 ,the terraced and rutted exterior of the rampart has all the usual characteristic details of the true crater4 ,the surface of the high plateau is marked by a few ridges branching from a point nearly in its centre1 together with some other slight elevations and depressions2 these1 however1 can only be detected when the sun's rays fall nearly parallel to the surface of the plateau4 ,to the north of this interesting object is the magnificent ring formation ,schickard1 whose vast diameter of #abc miles contrasts strikingly with that of the sixteen small craters within his rampart1 and equally so with a multitude of small craters scattered around4 ,there are many objects of interest on the portion of the lunar surface included within our illustration1 but as they are all of the usual type1 we shall not fatigue the attention of our readers by special descriptions of them4 ,,aristarchus1 #agf 7#fc--iib71 and ,,herodotus1 #age 7#fcb--iif74 ,plate ,,xviii4 ,these two fine examples of lunar volcanic craters are conspicuously situated in the north-east quarter of the moon's disc4 ,aristarchus has a circular rampart nearly #bh miles diameter1 the summit of which is about #gejj feet above the surface of the plateau1 while its height above the general surface of the moon is #bfjj feet4 ,a central cone having several subordinate peaks completes the true volcanic character of this crater3 its rampart banks1 both outside and inside1 have fine examples of the segmental crescent-shaped ridges or landslips1 which form so constant and characteristic a feature in the structure of lunar craters4 ,several very notable cracks or chasms may be seen to the north of these two craters4 ,they are contorted in a very unusual and remarkable manner1 the result probably of the force which formed them having to encounter very varying resistance near the surface4 ,some parts of these chasms gape to the width of two to three miles1 and when closely scrutinized are seen to be here and there partly filled by masses which have fallen inward from their sides4 ,several smaller craters are scattered around1 which1 together with the great chasms and neighbouring ridges1 give evidence of varied volcanic activity in this locality4 ,we must not omit to draw attention to the parallelism or general similarity of 8strike0 in the ridges of extruded matter2 this appearance has special interest in the eyes of geologists1 and is well represented in our illustration4 ,aristarchus is specially remarkable for the extraordinary capability which the material forming its interior and rampart banks has of reflecting light4 ,although there are many portions of the lunar surface which possess the same property1 yet few so remarkably as in the case of ,aristarchus1 which shines with such brightness1 as compared with its immediate surroundings1 as to attract the attention of the most unpractized observer4 ,some have supposed this appearance to be due to active volcanic discharge still lingering on the lunar surface1 an idea in which1 for reasons to be duly adduced1 we have no faith4 ,copernicus1 in the remarkable bright streaks which radiate from it1 and ,tycho also1 as well as several other spots1 are apparently composed of material very nearly as highly reflective as that of ,aristarchus4 ,but the comparative isolation of ,aristarchus1 as well as the extraordinary light-reflecting property of its material1 renders it especially noticeable1 so much so as to make it quite a conspicuous object when illuminated only by earth-light1 when but a slender crescent of the lunar disc is illuminated1 or when1 as during a lunar eclipse1 the disc of the moon is within the shadow of the earth1 and is lighted only by the rays refracted through the earth's atmosphere4 ,there are no features about ,herodotus of any such speciality as to call for remark1 except it be the breach of the north side of its rampart by the southern extremity of a very remarkable contorted crack or chasm1 which to all appearance owes its existence to some great disruptive action subsequent to the formation of the crater4 ,,walter1 #dh 7#cgh--acai71 and adjacent ,intrusive ,craters4 ,plate ,,xx4 ,this ,plate represents a southern portion of the moon's surface measuring #agj by #bcj miles4 ,it includes upwards of #bjj craters of all dimensions1 from ,walter1 whose rampart measures nearly #gj miles across1 down to those of such small apparent diameter as to require a well practized eye to detect them4 ,in the interior of the great crater ,walter a remarkable group of small craters may be observed surrounding his central cone1 which in this instance is not so perfectly in the centre of the rampart as is usually the case4 ,the number of small craters which we have observed within the rampart is #bj1 exclusive of those on the rampart itself4 ,the entire group represented in the ,plate suggests in a striking manner the wild scenery which must characterize many portions of the lunar surface2 the more so if we keep in mind the vast proportions of the objects which they comprise1 upon which point we may remark that the smallest crater represented in this ,plate is considerably larger than that of ,vesuvius4 ,,archimedes1 #aia 7#djc--ieh71 ,,autolycus1 #ahi 7#cfh--iee71 ,,aristillus1 #aij 7#cgj--icc71 and the ,,apennines4 ,plate ,,ix4 ,this group of three magnificent craters1 together with their remarkable surroundings1 especially including the noble range of mountains termed the ,apennines1 forms on the whole one of the most striking and interesting portions of the lunar surface4 ,if the reader is not acquainted with what the telescope can reveal as to the grandeur of the effect of sunrise on this very remarkable portion of the moon's surface1 he should carefully inspect and study our illustration of it2 and if he will pay due regard to our previously repeated suggestion concerning the attached scale of miles1 he will1 should he have the good fortune to study the actual objects by the aid of a telescope1 be well prepared to realize and duly appreciate the magnificence of the scene which will be presented to his sight4 ,were we to attempt an adequate detail description of all the interesting features comprised within our illustration1 it would1 of itself1 fill a goodly volume2 as there is included within the space represented every variety of feature which so interestingly characterizes the lunar surface4 ,all the more prominent details are types of their class2 and are so favourably situated in respect to almost direct vision1 as to render their nature1 forms1 and altitudes above and depths below the average surface of the moon most distinctly and impressively cognizable4 ,archimedes is the largest crater in the group2 it has a diameter of upwards of #eb miles1 measuring from summit to summit of its vast circular rampart or crater wall1 the average height of which1 above the plateau1 is about #dcjj feet2 but some parts of it rise considerably higher1 and1 in consequence1 cast steeple-like shadows across the plateau when the sun's rays are intercepted by them at a low angle4 ,the plateau of this grand crater is devoid of the usual central cone4 ,two comparatively minute but beautifully-formed craters may be detected close to the north-east interior side of the surrounding wall of the great crater4 ,both outside and inside of the crater wall may be seen magnificent examples of the landslip subsidence of its overloaded banks2 these landslips form vast concentric segments of the outer and inner circumference of the great circular rampart1 and doubtless belong to its era of formation4 ,two very fine examples of cracks1 or chasms1 may be observed proceeding from the opposite external sides of the crater1 and extending upwards of #ajj miles in each direction2 these cracks1 or chasms1 are fully a mile wide at their commencement next the crater1 and narrow away to invisibility at their further extremity4 ,their course is considerably crooked1 and in some parts they are partially filled by masses of the material of their sides1 which have fallen inward and partially choked them4 ,the depths of these enormous chasms must be very great1 as they probably owe their existence to some mighty upheaving action1 which there is every reason to suppose originated at a profound depth1 since the general surface on each side of the crater does not appear to be disturbed as to altitude1 which would have been the case had the upheaving action been at a moderate depth beneath4 ,we would venture to ascribe a depth of not less than ten miles as the most moderate estimate of the profundity of these terrible chasms4 ,if the reader would realize the scale of them1 let him for a moment imagine himself a traveller on the surface of the moon coming upon one of them1 and finding his onward progress arrested by the sudden appearance of its vast black yawning depths2 for by reason of the angle of his vision being almost parallel to the surface1 no appearance of so profound a chasm would break upon his sight until he came comparatively close to its fearful edge4 ,our imaginary lunar traveller would have to make a very long dtour1 ere he circumvented this terrible interruption to his progress4 ,if the reader will only endeavour to realize in his mind's eye the terrific grandeur of a chasm a mile wide and of such dark profundity as to be1 to all appearance1 fathomless--portions of its rugged sides fallen in wild confusion into the jaws of the tortuous abyss1 and catching here and there a ray of the sun sufficient only to render the darkness of the chasm more impressive as to its profundity--he will1 by so doing1 learn to appreciate the romantic grandeur of this1 one of the many features which the study of the lunar surface presents to the careful observer1 and which exceed in sublimity the wildest efforts of poetic and romantic imagination4 ,the contemplation of these views of the lunar world are1 moreover1 vastly enhanced by special circumstances which add greatly to the impressiveness of lunar scenery1 such as the unchanging pitchy-black aspect of the heavens and the death-like silence which reigns unbroken there4 ,these digressions are1 in some respects1 a forestallment of what we have to say by-and-by1 and so far they are out of place2 but with the illustration to which the above remarks refer placed before the reader1 they may1 in some respects1 enhance the interest of its examination4 ,the upper portion of our illustration is occupied by the magnificent range of volcanic mountains named after our ,apennines1 extending to a length of upwards of #dej miles4 ,this mountain group rises gradually from a comparatively level surface towards the south-west1 in the form of innumerable comparatively small mountains of exudation1 which increase in number and altitude towards the north-east1 where they culminate and suddenly terminate in a sublime range of peaks1 whose altitude and rugged aspect must form one of the most terribly grand and romantic scenes which imagination can conceive4 ,the north-east face of the range terminates abruptly in an almost vertical precipitous face1 and over the plain beneath intense black steeple or spire-like shadows are cast1 some of which at sunrise extend fully #ij miles1 till they lose themselves in the general shading due to the curvature of the lunar surface4 ,nothing can exceed the sublimity of such a range of mountains1 many of which rise to heights of #ah1jjj to #bj1jjj feet at one bound from the plane at their north-east base4 ,the most favourable time to examine the details of this magnificent range is from about a day before first quarter to a day after1 as it is then that the general structure of the range as well as the character of the contour of each member of the group can1 from the circumstances of illumination then obtaining1 be most distinctly inferred4 ,several comparatively small perfectly-formed craters are seen interspersed among the mountains1 giving evidence of the truly volcanic character of the surrounding region1 which1 as before said1 comprises in a comparatively limited space the most perfect and striking examples of nearly every class of lunar volcanic phenomena4 ,we have endeavoured on ,plate ,,xxiii4 to give some idea of a landscape view of a small portion of this mountain range4 ,illustration3 ,,plate ,,vi4 ,,terrestrial ,,and ,,lunar ,,volcanic ,,areas ,,compared4 ,,portion ,,of ,,the ,,moon',s ,,surface4 ,illustration3 ,,vesuvius ,,and ,,neighbourhood ,,of ,,naples4 ,,chapter ,,viii4 ,,on ,,lunar ,,craters4 ,as we stated in our brief general description of the visible hemisphere of the moon1 and as a cursory glance at our map and plates will have shown1 the predominant features of the lunar surface are the circular or amphitheatrical formations that1 by their number1 and from their almost unnatural uniformity of design1 induced the belief among early observers that they must have been of artificial origin4 ,in proceeding now to examine the details of our subject with more minuteness than before1 these annular formations claim the first share of our attention4 ,by general acceptation the term 8crater0 has been used to represent nearly all the circular hollows that we observe upon the moon2 and without doubt the word in its literal sense1 as indicating a cup or circular cavity1 is so far aptly applied4 ,but among geologists it has been employed in a more special sense to define the hollowing out that is found at the summit of some extinct1 and the majority of active1 volcanoes4 ,in this special sense it may be used by the student of the lunar surface1 though in some1 and indeed in the majority of cases1 the lunar crater differs materially in its form with respect to its surroundings from those on the earth2 for while1 as we have said1 the terrestrial crater is generally a hollow on a mountain top with its flat bottom high above the level of the surrounding country1 those upon the moon have their lowest points depressed more or less deeply below the general surface of the moon1 the external height being frequently only a half or one-third of the internal depth4 ,yet are the lunar craters truly volcanic2 as ,sir ,john ,herschel has said1 they offer the true volcanic character in its highest perfection4 ,we have upon the earth some few instances in which the geological conditions which have determined the surface-formation have been identical with those that have obtained upon the moon2 and as a result we have some terrestrial volcanic districts that1 could we view them under the same circumstances1 would be identical in character with what we see by telescopic aid upon our satellite4 ,the most remarkable case of this similarity is offered by a certain tract of the volcanic area about ,naples1 known from classic times as the ,campi ,phlegri1 or burning fields1 a name given to them in early days1 either because they showed traces of ancient earth-fire1 or because there were attached to the localities traditions concerning hot-springs and sulphurous exhalations1 if not of actual fiery eruptions4 ,the resemblance of which we are speaking is here so close that ,professor ,phillips1 in his work on ,vesuvius1 which by the way contains a historical description of the district in question1 calls the moon a grand ,phlegreian field4 ,how closely the ancient craters of this famous spot resemble the generality of those upon the moon may be judged from ,plate ,,vi41 in which representations of two areas1 terrestrial and lunar1 of the same extent1 are exhibited side by side1 the terrestrial region being the volcanic neighbourhood of ,naples1 and the lunar a portion of the surface about the crater ,theophilus4 ,in comparing these volcanic circles together1 we are however brought face to face with a striking difference that exists between the lunar and terrestrial craters4 ,this is the difference of magnitude4 ,none of those ,plutonian amphitheatres included in the terrestrial area depicted exceed a mile in diameter1 and few larger volcanic vents than these are known upon the earth4 ,yet when we turn to the moon1 and measure some of the larger craters there1 we are astonished to find them ranging from an almost invisible minuteness to #gd miles in diameter4 ,the same disproportion exists between the depths of the two classes of craters4 ,to give an idea of relative dimensions1 we would refer to our illustration of ,copernicus#h and its hundreds of comparatively minute surrounding craters4 ,our terrestrial ,vesuvius would be represented by one of these last1 which upon the plate measures about the twentieth of an inch in diameter6 ,and this disproportion strikes us the more forcibly when we consider that the lunar globe has an area only one-thirteenth of that of the earth4 ,in view of this great apparent discrepancy it is not surprising that many should have been incredulous as to the true volcanic character of the lunar mountains1 and have preferred to designate them by some 8non-committal0 term1 as an ,american geologist 7,professor ,dana7 has expressed it4 ,but there is a feature in the majority of the ring-mountains that1 as we conceive1 demonstrates completely the fact of volcanic force having been in full action1 and that seems to stamp the volcanic character upon the crater-forms4 ,this special feature is the central cone1 so well known as a characteristic of terrestrial volcanoes1 accepted as the result of the last expiring effort of the eruptive force1 and formed by the deposit1 immediately around the volcanic orifice1 of matter which there was not force enough to project to a greater distance4 ,upon the moon we have the central cone in small craters comparable to those on the earth1 and we have it in progressively larger examples1 upon all scales1 up to craters of #gd miles in diameter1 as we have shown in ,plate ,,vii4 ,where1 then1 can we draw the line8 ,where can we say the parallel action to that which placed ,vesuvius in or near the centre of the arc of ,somma1 or the cone figured in our sectional drawing of ,vesuvius 7,fig4 #c7 in the middle of its present crater--where can we say that the action in question ceased to manifest itself on the moon1 seeing that there is no break in the continuity of the crater-and-cone system upon the moon anywhere between craters of #a miles and #gd miles in diameter8 ,we have1 it is true1 many examples of coneless craters1 but these are of all sizes1 down to the smallest1 and up to a largeness that would almost seem to render untenable the ejective explanation3 of these we shall specially speak in turn1 but for the present we will confine ourselves to the normal class of lunar craters1 those that have central cones1 and that are in all reasonable probability truly volcanic4 ,illustration3 ,fig4 #af4 ,and in the first place let us take a passing glance at the probable formative process of a terrestrial volcano4 ,rejecting the hypothesis of ,von ,buch1 which geologists have on the whole found to be untenable1 and which ascribes the formation of all mountains to the elevation of the earth's crust by some thrusting power beneath1 we are led to regard a volcano as a pyramid of ejected matter1 thrown out of and around an orifice in the external solid shell of the earth by commotions engendered in its molten nucleus4 ,what is the precise nature and source of the ejective force geologists have not perfectly agreed upon1 but we may conceive that highly expanded vapour1 in all probability steam1 is its primary cause4 ,the escaping aperture may have been a weak place since the foundations of the earth were laid1 or it may have been formed by a local expansion of the nucleus in the act of cooling1 upon the principle enunciated in our ,third ,chapter2 or1 again1 the expansile vapour may have forced its own way through that point of the confining shell that offered it the least resistance4 ,the vent once formed1 the building of the volcanic mountain commenced by the out-belching of the lava1 ashes1 and scoria1 and the dispersion of these around the vent at distances depending upon the energy with which they were projected4 ,as the action continued1 the ejected matter would accumulate in the form of a mound1 through the centre of which communication would be maintained with the source of the ejected materials and the seat of the explosive agency4 ,the height to which the pile would rise must depend upon several conditions3 upon the steady sustenance of the matter1 and upon the form and weight of the component masses1 which will determine the slope of the mountain's sides4 ,supposing the action to subside gradually1 the tapering form will be continued upwards by the comparatively gentle deposition of material around the orifice1 and a perfect cone will result of some such form as that represented below1 which is the outline ascribed by ,professor ,phillips to ,vesuvius in pre-historic1 or even pre-traditional times1 and which may be seen in its full integrity in the cases of ,etna1 ,teneriffe1 ,fussi-,yamma1 the great volcanic mountain of ,japan1 and many others4 ,the earliest recorded form of ,vesuvius is that of a truncated cone represented in ,fig4 #ag1 which shows its condition1 according to ,strabo1 in the century preceding the ,christian ,era4 ,illustration3 ,,plate ,,vii ,,diagram ,,of ,,lunar ,,craters ,,forming ,a ,,series ,,ranging ,,from #a ,,miles ,,to #gh ,,miles ,,diameter4 ,,all ,,containing ,,central ,,cones4 ,illustration3 ,fig4 #ag4 ,illustration3 ,fig4 #ah4 ,now this form may have been assumed under two conditions4 ,if1 as ,phillips has surmised1 the mountain originally had a peaked summit with but a small crater-orifice at the point1 then we must ascribe its decapitation to a subsequent eruption which in its violence carried away the upper portion1 either suddenly1 or through a comparatively slow process of grinding away or widening out of the sides of the orifice by the chafing or fluxing action of the out-going materials4 ,but it is probable that the mountain never had the perfect summit indicated in our first outline4 ,the violent outburst that caused the great crater-opening of our second figure may have been but one paroxysmal phase of the eruption that built the mountain3 a sudden cessation of the eruptive force when at its greatest intensity1 and when the orifice was at its widest1 would leave matters in an opposite condition to that suggested as the result of a slow dying out of the action3 instead of the peak we should have a wide crater-mouth4 ,it is of small consequence for our present purpose whether the crater was contemporaneous with the primitive formation of the mountain1 or whether it was formed centuries afterwards by the blowing away of the mountain's head2 for upon the vast scale of geological time1 intervals such as those between successive paroxysms of the same eruption1 and those between successive eruptions1 are scarcely to be discriminated1 even though the first be days and the second centuries4 ,we may remark that the widening of a crater by a subsequent and probably more powerful eruption than that which originally produced it is well established4 ,we have only to glance at the sketch1 ,fig4 #ah1 of the outline of ,vesuvius as it appeared between the years ,a4,d4 #gi and #afca to see how the old crater was enlarged by the terrible ,pompeian eruption of the first-mentioned year4 ,here we have a crater ground and blown away till its original diameter of a mile and three-quarters has been increased to nearly three miles4 ,scrope had no hesitation in expressing his conviction that the external rings1 such as those of ,santorin1 ,st4 ,jago1 ,st ,helena1 the ,cirque of ,teneriffe1 the ,curral of ,madeira1 the cliff range that surrounds the island of ,bourbon1 and others of similar form and structure1 however wide the area they enclose1 are truly the 8basal wrecks0 of volcanic mountains that have been blown into the air each by some eruption of peculiar paroxysmal violence and persistence2 and that the circular or elliptical basins which they wholly or in part surround are in all cases true craters of eruption4 ,when the violent outburst that produces a great crater in a volcanic mountain-top more or less completely subsides1 the funnel or escaping orifice becomes choked with dbris4 ,still the vent strives to keep itself open1 and now and then gives out a small delivery of cindery matter1 which1 being piled around the vent1 after the manner of its great prototype1 forms the inner cone4 ,this last may in its turn bear an open crater upon its summit1 and a still smaller cone may form within it4 ,as the action further dies away1 the molten lava1 no longer seething and boiling1 and spirting forth with the rest of the ejected matter1 wells upwards slowly1 and cooling rapidly as it comes in contact with the atmosphere1 solidifies and forms a flat bottom or floor to the crater4 ,illustration3 ,fig4 #ai4 ,it may happen that a subsequent eruption from the original vent will be comparable in violence to the original one1 and then the inner cone assumes a magnitude that renders it the principal feature of the mountain1 and reduces the old crater to a secondary object4 ,this has been the case with ,vesuvius4 ,during the eruption of #afca the great cone which we now call ,vesuvius was thrown up1 and the ancient crater now distinguished as ,monte ,somma became a subsidiary portion of the whole mountain4 ,then the appearance was that shown in ,fig4 #ai1 and which does not differ greatly from that presented in the present day4 ,the summit of the ,vesuvian cone1 however1 has been variously altered2 it has been blown away1 leaving a large crateral hollow1 and it has rebuilt itself nearly upon its former model4 ,when we transfer our attention to the volcanoes of the moon1 we find ourselves not quite so well favoured with means for studying the process of their formation2 for the sight of the building up of a volcanic mountain such as man has been permitted to behold upon the earth has not been allowed to an observer of the moon4 ,the volcanic activity1 enfeebled though it now be1 of which we are witnesses from time to time on the earth1 has altogether ceased upon our satellite1 and left us only its effects as a clue to the means by which they were produced4 ,if we in our time could have seen the actual throwing up of a lunar crater1 our task of description would have been simple2 as it is we are compelled to infer the constructive action from scrutiny of the finished structure4 ,we can scarcely doubt that where a lunar crater bears general resemblance to a terrestrial crater1 the process of formation has been nearly the same in the one case as in the other4 ,where variations present themselves they may reasonably be ascribed to the difference of conditions pertaining to the two spheres4 ,the greatest dissimilarity is in the point of dimensions2 the projection of materials to #bj or more miles distance from a volcanic vent appears almost incredible1 until we realize the full effect of the conditions which upon the moon are so favourable to the dispersive action of an eruptive force4 ,in the first place1 the force of gravity upon our satellite is only one-sixth of that to which bodies are subject upon the earth4 ,secondly1 by reason of the small magnitude of the moon and its proportionally much larger surface in ratio to its magnitude1 the rate at which it parted with its cosmical heat must have been much more rapid than in the case of the earth1 especially when enhanced by the absence of the heat-conserving power of an atmosphere of air or water vapour2 and the disruptive and eruptive action and energy may be assumed to be greater in proportion to the more rapid rate of cooling2 operating1 too1 as eruptive action would on matter so much reduced in weight as it is on the surface of the moon1 we thus find in combination conditions most favourable to the display of volcanic action in the highest degree of violence4 ,moreover1 as the ejected material in its passage from the centre of discharge had not to encounter any atmospheric resistance1 it was left free to continue the primary impulse of its ejection without other than gravitative diminution1 and thus to deposit itself at distances from its source vastly greater than those of which we have examples on the earth4 ,we can of course only conjecture the source or nature of the moon's volcanic force4 ,if geologists have had difficulty in assigning an origin to the power that threw up our earthly volcanoes1 into whose craters they can penetrate1 whose processes they can watch1 and whose material they can analyze1 how vastly more difficult must be the inquiry into the primary source of the power that has been at work upon the moon1 which cannot be virtually approached by the eye within a distance of six or eight hundred miles1 and the material of which we cannot handle to see if it be compacted by heat1 or distended by vapours4 ,steam is the agent to which geologists have been accustomed to look for explanation of terrestrial volcanoes2 the contact of water with the molten nucleus of our globe is accepted as a probable means whereby volcanic commotions are set up and ejective action is generated4 ,but we are debarred from referring to steam as an element of lunar geology1 by reason of the absence of water from the lunar globe4 ,we might suppose that a small proportion of water once existed2 but a small proportion would not account for the immense display of volcanic action which the whole surface exhibits4 ,if we admitted a ,neptunian origin to the disturbances of the moon's crust1 we should be compelled to suppose that water had existed nearly in as great quantity1 area for area1 there as upon our globe2 but this we cannot reasonably do4 ,illustration3 ,,plate ,,viii4 ,,copernicus4 ,aqueous vapour being denied us1 we must look in other directions for an ejective force4 ,of the nature of the lunar materials we can know nothing1 and we might therefore assume anything2 some have had recourse to the supposition of expansive vapours given off by some volatile component of the said material while in a state of fusion1 or generated by chemical combinations4 ,professor ,dana refers to sulphur as probably an important element in the moon's geology1 suggesting this substance because of the part which it appears to play in the volcanic or igneous operations of our globe1 and on account of its presence in cosmical meteors that have come within range of our analysis4 ,any matter sublimated by heat in the substrata of the moon would be condensed upon reaching the cold surrounding space1 and would be deposited in a state of fine powder1 or otherwise in a solid form4 ,maedler has attributed the highly reflective portions of some parts of the surface1 such as the bright streams that radiate from some of the craters1 ,copernicus and ,tycho for instance1 to the vitrification of the surface matter by gaseous currents4 ,but in suppositions like these we must remember that the probability of truth diminishes as the free ground for speculation widens4 ,it does not appear clear how expansive vapours could have lain dormant till the moon assumed a solid crust1 as all such would doubtless make their escape before any shell was formed1 and at an epoch when there was ample facility for their expansion4 ,while we are not insensible of the value of an expansive vapour explanation1 if it could be based on anything beyond mere conjecture1 we are disposed to attach greater weight to that afforded by the principle sketched in our third chapter1 viz41 of expansion upon solidification4 ,we gave1 as we think1 ample proof that molten matter of volcanic nature1 when about passing to the solid state1 increases its bulk to a considerable degree1 and we suggested that the lunar globe at one period of its history must have been1 what our earth is now1 a solid shell encompassing a molten nucleus2 and further1 that this last1 in approaching its solid condition1 expanded and burst open or rent its confining crust4 ,at first sight it may seem that we are ascribing too great a degree of energy to the expansive force which molten substances exhibit in passing to the solid condition1 seeing that in general such forces are slow and gradual in their action2 but this anomaly disappears when we consider the vast bulk of the so expanding matter1 and the comparatively small amount that in its expansion it had to displace4 ,it is true that there are individual mountains on the moon covering many square miles of surface1 that as much as a thousand cubic miles of material may have been thrown up at a single eruption2 but what is this compared to the entire bulk of the moon itself8 ,a grain of mustard-seed upon a globe three feet in diameter represents the scale of the loftiest of terrestrial mountains2 a similar grain upon a globe one foot in diameter1 would indicate the proportion of the largest upon the moon4 ,a model of our satellite with the elevations to scale would show nothing more than a little roughness1 or superficial blistering4 ,turn for a moment to our map 7,plate ,,iv471 upon which the shadows give information as to the heights of the various irregularities1 and suppose it to represent the actual size of some sphere whose surface has been broken up by reactions of some kind of the interior upon the exterior--suppose it to have been a globe of fragile material filled with some viscous substance1 and that this has expanded1 cracked its shell1 oozed out in the process of solidification1 and solidified3 the irregularity of surface which the small sphere1 roughened by the out-leaking matter1 would present1 would not be less than that exhibited in the map under notice4 ,when we say that a lunar crater has a diameter of #cj miles1 we raise astonishment that such a structure could result from an eruption by the expansive force of solidifying matter2 but when we reflect that this diameter is less than the two-hundredth part of the circumference of the moon1 we need have no difficulty in regarding the upheaval as the result of a force slight in comparison to the bulk of the material giving rise to it4 ,we have upon the moon evidence of volcanic eruptions being the final result of most extensive dislocations of surface1 such as could only be produced by some widely diffused uplifting force4 ,we allude to the frequent occurrence of chains of craters lying in a nearly straight line1 and of craters situated at the converging point of visible lines of surface disturbance4 ,our map will exhibit many examples of both cases4 ,an examination of the upper portion 7the southern hemisphere of the moon7 will reveal abundant instances of the linear arrangement1 three1 four1 five or even more crateral circles will be found to lie with their centres upon the same great-circle track1 proving almost undoubtedly a connexion between them so far as the original disturbing force which produced them is concerned4 ,again1 in the craters ,tycho 7#cj71 ,copernicus 7#adg71 ,kepler 7#adf71 and ,proclus 7#afb71 we see instances of the situation of a volcanic outburst at an obvious focus of disturbance4 ,these manifest an up-thrusting force covering a large sub-surface area1 and escaping at the point of least resistance4 ,such an extent of action almost precludes the gaseous explanation1 but it is compatible with the expansion on consolidation theory1 since it is reasonable to suppose that in the process of consolidation the viscous nucleus would manifest its increase of bulk over considerable areas1 disturbing the superimposed crust either in one long crack1 out of the wider opening parts of which the expanded material would find its escape1 or 8starring0 it with numerous cracks1 from the converging point of which the confined matter would be ejected in greatest abundance and1 if ejected there with great energy and violence1 would result in the formation of a volcanic crater4 ,the actual process by which a lunar crater would be formed would differ from that pertaining to a terrestrial crater only to the extent of the different conditions of the two globes4 ,we can scarcely accept ,scrope's term 8basal wrecks0 7of volcanic mountains that have had the summits blown away7 as applicable to the craters of the moon1 for the reason that the lunar globe does not offer us any instance of a mountain comparable in extent to the great craters and whose summit has not been blown away4 ,scrope's definition implies a double1 or divided process of formation3 first the building up of a vast conical hill and then the decapitation and 8evisceration0 of it at some later period4 ,there are grounds for this inferred double action among the terrestrial volcanoes1 since both the perfect cone and its summitless counterpart are numerously exemplified4 ,but upon the moon we have no perfect cone of great size1 we have no exception whereby the rule can be proved4 ,it is against probability1 supposing every lunar crater to have once been a mountain1 that in every case the mountain's summit should have been blown away2 and we are therefore compelled to consider that the moon's volcanic craters were formed by one continuous outburst1 and that their 8evisceration0 was a part of the original formative process4 ,we do not1 however1 include the central cone in this consideration3 that may be reasonably ascribed to a secondary action or perhaps1 better1 to a weaker or modified phase of the original and only eruption4 ,illustration3 ,fig4 #bj4 ,illustration3 ,fig4 #ba4 ,illustration3 ,,plate ,,ix4 ,,the ,,lunar ,,apennines1 ,,archimedes c41 c4 ,under these circumstances we conceive the upcasting and excavating of a normal lunar crater to have been primarily caused by a local manifestation of the force of expansion upon solidification of the subsurface matter of the moon1 resulting in the creation of a mere 8star0 or crack in and through the outermost and solid crust4 ,as we shall have to rely upon diagrams to explain the more complicated features1 we give one of this elementary stage also as a commencement of the series2 and ,fig4 #bj therefore represents a probable section of the lunar surface at a point which was subsequently the location of a crater4 ,from the vent thus formed we conceive the pent-up matter to have found its escape1 not necessarily at a single outburst1 but in all probability in a paroxysmal manner1 as volcanic action manifests itself on our globe4 ,the first outflow of molten material would probably produce no more than a mere hill or tumescence as shewn sectionally in ,fig4 #ba2 and if the ejective force were small this might increase to the magnitude of a mountain by an exudative process to be alluded to hereafter4 ,but if the ejective force were violent1 either at the moment of the first outburst or at any subsequent paroxysm1 an action represented in ,fig4 #bb would result3 the unsupported edges or lips of the vent-hole would be blown and ground or fluxed away1 and a funnel-formed cavity would be produced1 the ejected matter 7so much of it as in falling was not caught by the funnel7 being deposited around the hollow and forming an embryo circular mountain4 ,the continuance of this action would be accompanied by an enlargement of the conical cavity or crater1 not only by the outward rush of the violently discharged material1 but also by the 8sweating0 or grinding action of such of it as in descending fell within the hollow4 ,and at the same time that the crater enlarged the rampart would extend its circumference1 for it would be formed of such material as did not fall back again into the crater4 ,upon this view of the crater-forming process we base the sketch1 ,fig4 #bc1 of the probable section of a lunar crater at one period of its development4 ,illustration3 ,fig4 #bb4 ,so long as each succeeding paroxysm was greater than its predecessor1 this excavating of the hollow and widening of its mouth and mound would be extended4 ,but when a weaker outburst came1 or when the energy of the last eruption died away1 a process of slow piling up of matter close around the vent would ensue4 ,it is obvious that when the ejective force could no longer exert itself to a great distance it must merely have lifted its burden to the relieving vent and dropped it in the immediate neighbourhood4 ,even if the force were considerable1 the effect1 so long as it was insufficient to throw the ejecta beyond the rim of the crater1 would be to pile material in the lowermost part of the cavity2 for what was not cast over the edge would roll or flow down the inner slope and accumulate at the bottom4 ,and as the eruption died away1 it would add little by little to the heap1 each expiring effort leaving the out-given matter nearer the orifice1 and thus building up the central cone that is so conspicuous a feature in terrestrial volcanoes1 and which is also a marked one in a very large proportion of the craters of the moon4 ,this formation of the cone is pictorially described by ,fig4 #bd4 ,illustration3 ,fig4 #bc4 ,illustration3 ,fig4 #bd4 ,in the volcanoes of the earth we observe another action either concurrent with or immediately subsequent to the erection or formation of the cone3 this is the outflow or the welling forth of fluid lava1 which in cooling forms the well-known plateau4 ,we have this feature copiously represented upon the moon and it is presumable that it has in general been produced in a manner analogous to its counterparts upon the earth4 ,we may conceive that the fluid matter was either spirted forth with the solid or semisolid constituents of the cone1 in which case it would drain down and fill the bottom of the crater2 or we may suppose that it issued from the summit of the cone and ran down its sides1 or that1 as we see upon the earth1 it found its escape before reaching the apex1 by forcing its way through the basal parts4 ,these actions are indicated hypothetically for the moon in ,fig4 #be2 and the parallel phenomena for the earth are shewn by the actual case 7represented in ,fig4 #bf and on ,plate ,i47 of ,vesuvius as it was seen by one of the authors in #ahfe1 when the principal cone was vomiting forth ashes1 stones1 and red-hot lava1 while a vent at the side emitted very fluid lava which was settling down and forming the plateau4 ,illustration3 ,fig4 #be4 ,although we cannot1 obviously1 see upon the moon evidence of a cone actually overtopped by the rising lake of lava1 yet it is not unreasonable to suppose that such a condition of things actually occurred in many of those instances in which we observe craters without central cones1 but with plateaux so smooth as to indicate previous fluidity or viscosity4 ,from the state of things exhibited in ,fig4 #be the transition to that shewn in ,fig4 #bg is easily1 and to our view reasonably1 conceivable4 ,we are in a manner led up to this idea by a review of the various heights of central cones above their surrounding plateaux4 ,for instance1 in such examples as ,tycho or ,theophilus1 we have cones high above the lava floor2 in ,copernicus1 ,arzachael and ,alphonsus they are comparatively lower2 the lava in these and some other craters does not appear to have risen so high2 while in ,aristotle and ,eudoxus among others1 we have only traces of cones1 and it is supposable that in these cases the lava rose so high as nearly to overtop the central cones4 ,why should it not have risen so far as to overtop and therefore conceal some cones entirely8 ,we offer this as at least a feasible explanation of some coneless craters3 it is not necessary to suppose that it applies to all such1 however3 there may have been many craters1 the formation of which ceased so abruptly that no cone was produced1 though the welling forth of lava occurred from the vent1 which may have been left fully open1 as in ,fig4 #bh1 or so far choked as to stay the egress of solid ejecta and yet allow the fluid material to ooze upwards through it1 and so form a lake of molten lava which on consolidation became the plateau4 ,as most of the examples of coneless craters exhibit on careful examination minute craters on the surface of the otherwise smooth plateaux1 we may suppose that such minute craters are evidences of the upflow of lava which resulted in the plateaux4 ,illustration3 ,,plate ,x4 ,,aristotle ,,eudoxus4 ,illustration3 ,fig4 #bf4 ,illustration3 ,fig4 #bg4 ,illustration3 ,fig4 #bh4 ,we have strong evidence in support of this up-flow of lava offered by the case of the crater ,wargentin1 7,no4 #bf1 #ege--adjb7 situated near the south-east border of the disc1 and of which we give a special plate4 7,plate ,,xvii47 ,it appears to be really a crater in which the lava has risen almost to the point of overflowing1 for the plateau is nearly level with the edge of the rampart4 ,this edge appears to have been higher on one side than the other1 for on the portion nearest the centre of the visible disc we may1 under favourable circumstances1 detect a segment of the basin's brim rising above the smooth plateau as indicated in our illustration4 ,upon the opposite side there is no such feature visible1 the plateau forms a sharp table-like edge4 ,it is just possible that an actual overflow of lava took place at this part of the crater1 but from the unfavourable situation of this remarkable object it is impossible to decide the point by observation4 ,there is no other crater upon the visible hemisphere of the moon that exhibits this filled-up condition2 but1 unique as it is1 it is sufficient to justify our conclusion that the plateau-forming action upon the moon has been a flowing-up of fluid matter from below subsequent to the formation of the crater-rampart1 and not1 as a casual glance at the great smooth-bottom craters might lead us to suspect1 a result of some sort of diluvial deposit which has filled hollows and cavities and so brought up an even surface4 ,the elevated basin of ,wargentin could not have been filled thus while the surrounding craters with ramparts equally or less high remained empty3 its contained matter must have been supplied from within1 we must conjecture by the upflow of lava from the orifice which gave forth the material to form the crateral rampart in the first instance4 ,we are free to conjecture that at some period of this table-mountain's formation it was a crater with a central cone1 and that the rising lava over-topped this last feature in the manner shewn by the above figure 7,fig4 #bi74 ,illustration3 ,fig4 #bi4 ,the question occurs whether other craters may not have been similarly filled and have emptied themselves by the bursting of the wall under the pressure of the accumulated lake of lava within4 ,we know that this breaching is a common phenomenon in the volcanoes of our globe2 the district of ,auvergne furnishing us with many examples2 and there are some suspicious instances upon the moon4 ,copernicus exhibits signs of such disruption1 as also does the smaller crater intruding upon the great circle of ,gassendi4 7,see ,frontispiece47 ,but the existence of such discharging breaches implies the outpouring of a body of fluid or semi-fluid material1 comparable in cubical content to the capacity of the crater1 and of this we ought to see traces or evidence in the form of a bulky or extensive lava stream issuing from the breach4 ,but although there are faint indications of once viscous material lying in the direction that escaping fluid would take1 we do not find anything of the extent that we should expect from the mass of matter that would constitute a craterfull4 ,it is true that if the escaping fluid had been very limpid it might have spread over a large area and have formed a stratum too thin to be detected4 ,such a degree of limpidity as would be required to fulfil this condition we are hardly1 however1 justified in assuming4 ,to return to the subject of central cones4 ,although there are cases in which the simple condition of a single cone exists1 yet in the majority we see that the cone-forming process has been divided or interrupted1 the consequence being the production of a group of conical hills instead of a single one4 ,copernicus offers an example of this character1 six1 some observers say seven1 separate points of light1 indicating as many peaks tipped with sunshine1 having been seen when the greater part of the crater has been buried in shadow4 ,erastothenes1 ,bulialdus1 ,maurolicus1 ,petavius1 ,langreen1 and ,gassendi1 are a few among many instances of craters possessing more than a central single cone4 ,this multiplication of peaks upon the moon doubtless arose from similar causes to those which produce the same feature in terrestrial volcanoes4 ,our sketch of ,vesuvius in #ahfe 7,fig4 #bf7 shows the double cone and the probable source of the secondary one in the diverted channel of the out-coming material4 ,a very slight interruption in the first instance would suffice to divert the stream and form another centre of action1 or a choking of the original vent would compel the issuing matter to find a less resisting thoroughfare into open space1 and the process of cone-building would be continued from the new orifice1 perhaps to be again interrupted after a time and again driven in another direction4 ,in this manner1 by repeated arrests and diversions of the ejecta1 cone has grown upon the side of cone1 till1 ere the force has entirely spent itself1 a cluster of peaks has been produced4 ,it may have been that this action has taken place after the formation of the plateau1 in the manner indicated by ,fig4 #cj2 a spasmodic outburst of comparatively slight violence having sought relief from the original vent1 and the flowing matter1 finding the one orifice not sufficiently open to let it pass1 having forced other exit through the plateau4 ,illustration3 ,,plate ,,xi4 ,,triesnecker4 ,illustration3 ,fig4 #cj4 ,in frequent instances we observe the state of things represented in ,fig4 #ca1 in which the plateau is studded with few or many small craters4 ,this is the case with ,plato1 with ,arzachael1 ,hipparchus1 ,clavius 7which contains about #ae small internal craters71 and many others4 ,it is probable that these subsidiary craters were produced by an after-action like that which has produced duplicated cones1 but in which the secondary eruption has been of somewhat violent character1 for it may almost be regarded as an axiom that violent eruptions excavate craters and weak ones pile up cones4 ,in the cases referred to it seems reasonable to suppose that the main vent has been the channel for an up-cast of material1 but that at some depth below the surface this material met with some obstruction or cause of diversion1 and that it took a course which brought it out far away from the cone upon the floor of the plateau4 ,it might even be carried so far as to be upon the rampart1 and it is no uncommon thing to see small craters in such a situation1 though when they appear at such a distance from the primary vent1 it seems more reasonable to suppose that they do not belong to it but have arisen from a subsequent and an independent action4 ,illustration3 ,fig4 #ca4 ,we find scarcely an instance of a small crater occurring just in the centre of a large one1 or taking the place of the cone4 ,this is a curious circumstance4 ,whenever we have any central feature in a great crater1 that feature is a cone4 ,the tendency of this fact is to prove that cones were produced by very weak efforts of this expiring force1 for had there been any strength in the last paroxysm it is presumable that it would have blown out and left a crater4 ,no very violent eruptions have therefore taken place from the vents that were connected with the great craters of the moon1 nothing more powerful than could produce a cone of exudation or a cinder-heap4 ,and with regard to cones1 it is noteworthy that whether they be single or multiple1 they never rise so high as the circular ramparts of their respective craters4 ,this supports the inferred connexion between the crater origin and the cone origin1 for supposing the two to have been independent1 a supposition untenable in view of the universality of the central position of the cone1 it is scarcely conceivable that the mountains should have always been located within ramparts higher than themselves4 ,the less height argues less power in the upcasting agency1 and the diminished force may well be considered as that which would almost of necessity precede the expiration of the eruption4 ,occasionally a crater is met with that has a double rampart1 and the concentricity suggests that there have been two eruptions from the same vent3 one powerful1 which formed the exterior circle1 and a second rather less powerful which has formed the interior circle4 ,it is not1 however evident that this duplication of the ring has always been due to a double eruption4 ,in many cases there is duplication of only a portion3 a terrace exhibits itself around a part of the circular range1 sometimes upon the outside and sometimes upon the inside4 ,these terraces are not likely to have been formed by any freak of the eruption1 and we are led to ascribe them in general to landslip phenomena4 ,when1 in the course of a volcano's formation1 the piling-up of material about the vent has continued till the lower portions have been unable to support the upper1 or when from any cause1 the material composing the pile has lost its cohesiveness1 the natural consequence has been a breaking away of a portion of the structure and its precipitation down the inclined sides of the crater4 ,vast segments of many of the lunar mountain-rings appear to have been thus dislodged from their original sites and cast down the flanks to form crescent ranges of volcanic rocks either within or without the circle4 ,nearly every one of our plates contains craters exhibiting this feature in more or less extensive degree4 ,sometimes the separated portion has been very small in proportion to the circumference of the crater3 ,plato is an instance in which a comparatively small mass has been detached4 ,in other cases very large segments have slid down and lie in segmental masses on the plateaux or form terraces around the rampart4 ,aristarchus1 ,treisnecker and ,copernicus exhibit this larger extent of dislocation4 ,it is possible that these landslips occurred long after the formation of the craters that have been subject to them4 ,they are probably attributable to recent disintegration of the lunar rocks1 and we have a powerful cause for this in the alternations of temperature to which the lunar crust is exposed4 ,we shall have occasion to revert to this subject by-and-bye2 at present it must suffice to point out that the extremes of cold and heat1 between which the lunar soil varies1 are1 with reasonable probability1 assumed to be on the one hand the temperature of space 7which is supposed to be about #bjj below zero71 and1 on the other hand1 a degree of heat equal to about twice that of boiling water4 ,a range of at least #ejj must work great changes in such heterogeneous materials as we may conjecture those of the lunar crust to be1 by the alternate contractions and expansions which it must engender1 and which must tend to enlarge existing fissures and create new ones1 to grind contiguous surfaces and to dislodge unstable masses4 ,this cause of change1 it is to be remarked1 is one which is still exerting itself4 ,in a few cases we have an entirely opposite interruption of the uniformity of a crater's contour4 ,instead of the breaking away of the ring in segments we see the entire circuit marked with deep ruts that run down the flanks in a radial direction1 giving us evidence of a downward streaming of semi-fluid matter1 instead of a disruption of solid masses4 ,we cannot doubt that these ruts have been formed by lava currents1 and they indicate a condition of ejected material different from that which existed in the cases where the landslip character is found4 ,in these last the ejecta appears to have been in the form of masses of solidified or rapidly solidifying matter1 which remained where deposited for a time and then gave way from overloading or loss of cohesiveness1 whereas the substances thrown out in the case of the rutted banks were probably mixed solid and fluid1 the former remaining upon the flanks while the latter trickled away4 ,nothing so well represents1 upon a small scale1 this radial channelling as a heap of wetted sand left for a while for the water to drain off from it4 ,the solid grains in such a heap sustain its general mass-form1 but the liquid in passing away cuts the surface into fissures running from the summit to the base1 and forms it into a model of a volcanic mountain with every feature of peak1 crag1 and chasm reproduced1 ,this similarity of effect leads us to suspect a parallelism of cause1 and thus to the inference that the material which originally formed such a crater-mountain as ,aristillus 7which is a most prominent example of this rutted character1 and appears in ,plate ,,ix41 side by side with a crater that has its banks segmentally broken71 must have been of the compound nature indicated2 and that an action analogous to that which ruts a damp sand-heap1 rutted also the banks of the lunar crater4 ,illustration3 ,,plate ,,xii4 ,,theophilus ,,cyrillus ,,catharina4 ,,sunset ,,aspect4 ,before passing from the subject of craters it behoves us to say a few words upon the curious manner in which these formations are complicated by intermingling and superposition4 ,yet1 upon this point1 we may be brief1 for in the way of description our plates speak more forcibly than is possible by words4 ,in particular we would refer to ,plate ,,xii41 which represents the conspicuous group of craters of which the three largest members have been respectively named ,theophilus1 ,cyrillus1 and ,catherina4 ,but the area included in this plate is by no means an extraordinary one2 there are regions about ,tycho wherein the craters so crowd and elbow each other that1 in their intricate combinations1 they almost defy accurate depiction4 ,our map and ,plate ,,xvi4 will serve to give some idea of them4 ,this intermingling of craters obviously shows that all the lunar volcanoes were not simultaneously produced1 but that after one had been formed1 an eruption occurred in its immediate neighbourhood and blew a portion of it away2 or it may have been that the same deep-seated vent at different times gave forth discharges of material the courses of which were more or less diverted on their way to the surface4 ,we have before alluded to the frequent occurrence of lines of craters upon the moon4 ,in these lines the overlapping is frequently visible2 it is seen in ,plate ,,xii4 before referred to1 where the ring mountains are linked into a chain slightly curved1 and upon the map1 ,plate ,,iv41 the nearly central craters ,ptolemy and ,alphonsus1 the latter of which overlaps the former1 are seen to form part of a line of craters marking a connection of primary disturbance4 ,an extensive crack suggests itself as a favourable cause for the production of this overlaying of craters1 for it would serve as a sort of 8line of fire0 from various points at which eruptions would burst forth1 sometimes weak or far apart1 when the result would be lines of isolated craters1 and sometimes near together1 or powerful1 when the consequence would be the intrusion of one upon the other1 and the perfect production of the latest formed at the expense or to the detriment of those that had been formed previously4 ,the linear grouping of volcanoes upon the earth long ago struck observant minds4 ,the fable of the ,typhon lying under ,sicily and the ,phlegreian fields and disturbing the earth by its writhings1 is a mythological attempt to explain the particular case in that region4 ,the capricious manner in which these intrusions occur is very curious4 ,very commonly a small crater appears upon the very rampart of a greater one1 and a more diminutive one still will appear upon the rampart of the parasite4 ,stoeffler presents us with one example of this character1 ,hipparchus with another1 ,maurolycus with a third1 and these are but a few cases of many4 ,here and there we observe several craters ranged in a line with their rims in one direction all perfect1 and the whole appearing like a row of coins that have fallen from a heap4 ,there is an example near to ,tycho which we reproduce in ,plate ,,xx4 ,in this case one is led to conjecture that the ejective agency1 after exerting itself in one spot1 travelled onward and renewed itself for a time2 that it ceased after forming crater number two1 and again journeyed forward in the same line1 recommencing action some miles further1 and again subsiding2 yet again pushing forward and repeating its outburst1 till it produced the fourth crater1 when its power became expended4 ,in each of these successive eruptions the centre of discharge has been just outside the crater last formed2 and the close connexion of the members of the group1 together with the fact of their nearly similar size1 appears to indicate a community of origin4 ,for it seems feasible that as a general rule the size of a crater may be taken as a measure of the depth of force that gave rise to the eruption producing it4 ,this may not be true for particular cases1 but it will hold where a great number are collectively considered2 for if we assume the existence of an average disturbing force1 it is apparently clear that it will manifest itself in disturbing greater or less surface-areas in proportion as it acts from greater or less depths4 ,or1 mutatis mutandis1 if we assume an uniform depth for the source of action1 the greater or less surface disturbance will be a measure of greater or less eruptive intensity4 ,perhaps the most remarkable case of a vast number of craters1 which1 from their uniform dimensions1 suggest the idea of community of source-power or source-depth1 is that offered by the region surrounding ,copernicus1 which1 as will be seen by our plate of that object1 is a vast ,phlegreian field of diminutive craters4 ,so countless are the minute craters that a high magnifying power brings into view when atmospheric circumstances are favourable1 and so closely are they crowded together1 that the resulting appearance suggests the idea of froth1 and we should be disposed to christen this the 8frothy region0 of the moon1 did not a danger exist in the tendency to connect a name with a cause4 ,the craters that are here so abundant are doubtless the remains of true volcanoes analogous to the parasitical cones that are to be found on several terrestrial mountains1 and not such accidental formations as the ,hornitos described by ,humboldt as abounding in the neighbourhood of the ,mexican volcano1 ,jurillo1 but which the traveller did not consider to be true cones of eruption4#i ,although upon our plate1 and in comparison with the great crater that is its chief feature1 these countless hollows appear so small as at first sight to appear insignificant1 we must remember that the minutest of them must be grand objects1 each probably equal in dimensions to ,vesuvius4 ,for since1 as we have shown in an early chapter1 the smallest discernible telescopic object must subtend an angle to our eye of about a second1 and since this angle extended to the moon represents a mile of its surface1 it follows that these tiny specks of shadow that besprinkle our picture1 are in the reality craters of a mile diameter4 ,this comparison may help the conception of the stupendous magnitude of the moon's volcanic features2 for it is a conception most difficult to realize4 ,it is hard to bring the mind to grasp the fact that that hollow of ,copernicus is fifty miles in diameter4 ,we read of an army having encamped in the once peaceful crater of ,vesuvius1 and of one of the extinct volcanoes of the ,campi ,phlegri being used as a hunting preserve by an ,italian king4 ,these facts give an idea of vastness to those who have not the good fortune to see the actual dimensions of a volcanic orifice themselves4 ,but it is almost impossible to conjure up a vision of what that fifty-mile crater would look like upon the moon itself2 and for want of a terrestrial object as a standard of comparison1 our picture1 and even the telescopic view of the moon itself1 fails to render the imagination any help4 ,we may try to realize the vastness by considering that one of our average ,english counties could be contained within its ramparts1 or by conceiving a mountainous amphitheatre whose opposite sides are as far apart as the cathedrals of ,london and ,canterbury1 but even these comparisons leave us unimpressed with the true majesty which the object would present to a spectator upon the surface of our satellite4 ,illustration3 ,,the ,,formation ,,of ,,the ,,central ,,cone4 ,,final ,,action ,,of ,a ,,lunar ,,volcano4 ,illustration3 ,,plate ,,xiii ,,arzachael1 ,,ptolemy1 and the ,,railway4 ,,chapter ,,ix4 ,,on ,,the ,,great ,,ring-,,formations ,,not ,,manifestly ,,volcanic4 ,in our previous chapter we have given a reason for regarding as true volcanic craters all those circular formations1 of whatever size1 that exhibit that distinctive feature the central cone4 ,between the smallest crater with a cone that we can detect under the best telescopic conditions1 namely1 the companion to ,hell1 #a mile diameter1 and the great one called ,petavius1 #gh miles in diameter1 we find no break in the continuity of the crater-cum-cone system that would justify us in saying that on the one side the volcanic or eruptive cause ceased1 and on the other side some other causative action began4 ,but there are numerous circular formations that surpass the magnitude of ,petavius and its peers1 but that have no central cone1 and are1 therefore1 not so manifestly volcanic as those which possess this feature4 ,our map will show many striking examples of this class at a glance4 ,we may in particular refer inter alia to ,ptolemy near the centre of the moon1 to ,grimaldi 7,no4 #abe71 ,shickard 7,no4 #bh71 ,schiller 7,no4 #bd71 and ,clavius 7,no4 #ac71 all of which exceed #ajj miles in diameter4 ,even the great ,mare ,crisium1 nearly #cjj miles in diameter1 appears to be a formation not distinct from those which we have just named4 ,these present little of the generic crater character in their appearance2 and they have been distinguished therefrom by the name of ,walled or ,ramparted ,plains4 ,their actual origin is beyond our explanation1 and in attempting to account for them we must perforce allow considerable freedom to conjecture4 ,they certainly1 as ,hooke suggested1 present a 8broken bubble0-like aspect2 but one cannot reasonably imagine the existence of any form of mineral matter that would sustain itself in bubble form over areas of many hundreds of square miles4 ,and if it were reasonable to suppose the great rings to be the foundations of such vast volcanic domes1 we must conclude these to have broken when they could no longer sustain themselves1 and in that case the surface beneath should be strewed with dbris1 of which1 however1 we can find no trace4 ,moreover1 we might fairly expect that some of the smaller domes would have remained standing3 we need hardly say that nothing of the kind exists4 ,illustration3 ,fig4 #cb4 ,the true circularity of these objects appears at first view a remarkable feature4 ,but it ceases to be so if we suppose them to have been produced by some very concentrated sublunar force of an upheaving nature1 and if only we admit the homogeneity of the moon's crust4 ,for if the crust be homogeneous1 then any upheaving force1 deeply seated beneath it1 will exert itself with equal effects at equal distances from the source3 the lines of equal effect will obviously be radii of a sphere with the source of the disturbance for its centre1 and they will meet a surface over the source in a circle4 ,this will be evident from ,fig4 #cb1 in which a force is supposed to act at ,f below the surface s s s s4 ,the matter composing s s being homogeneous1 the action of ,f will be equal at equal distances in all directions4 ,the lines of equal force1 ,f f1 ,f f1 will be of equal length1 and they will form1 so to speak1 radii of a sphere of force4 ,this sphere is cut by the plane at s s s s1 and as the intersection necessarily takes place everywhere at the extremity of these radii1 the figure of intersection is demonstrably a circle 7shown in perspective as an ellipse in the figure74 ,thus we see that an intense but extremely confined explosion1 for instance1 beneath the moon's crust must disturb a circular area of its surface1 if the intervening material be homogeneous4 ,if this be not homogeneous there would be1 where it offered less than the average resistance to the disturbance1 an outward distortion of the circle2 and an opposite interruption to circularity if it offers more than the average resistance4 ,this assumed homogeneity may possibly be the explanation of the general circularity of the lunar surface features1 small and great4 ,illustration3 ,fig4 #cc4 ,illustration3 ,fig4 #cd4 ,we confess to a difficulty in accounting for such a very local generation of a deep-seated force2 and1 granting its occurrence1 we are unprepared with a satisfactory theory to explain the resultant effect of such a force in producing a raised ring at the limit of the circular disturbance4 ,we may indeed1 suppose that a vast circular cake or conical frustra would be temporarily upraised as in ,fig4 #cc1 and that upon its subsidence a certain extrusion of subsurface matter would occur around the line or zone of rupture as in ,fig4 #cd4 ,this supposition1 however1 implies such a peculiarly cohesive condition of the matter of the uplifted cake1 that it is doubtful whether it can be considered tenable4 ,we should expect any ordinary form of rocky matter subjected to such an upheaval to be fractured and distorted1 especially when the original disturbing force is greater in the centre than at the edge1 as1 according to the above hypothesis1 it would be2 and in subsiding1 the rocky plateau would thus retain some traces of its disturbance2 but in the circular areas upon the moon there is nothing to indicate that they have been subjected to such dislocations4 ,illustration3 ,fig4 #ce4 ,a ,a4 ,fissures gaping downwards and injected by intumescent lava beneath4 ,b ,b ,b4 ,fissures gaping upwards and allowing wedges of rock to drop below the level of the intervening masses1 ,c ,c4 ,wedges forced upwards by horizontal compression4 ,e ,f4 ,neutral plane or pivot axis1 above and below which the directions of the tearing strain and horizontal compression are severally indicated by the smaller arrows2 the larger arrows beneath represent the direction of the primary expansive force4 ,mr4 ,scrope in his work on volcanoes has given a hypothetical section of a portion of the earth's crust1 which presents a bulging or tumescent surface in some measure resembling the effect which such a cause as we have been considering would produce4 ,we give a slightly modified version of his sketch in ,fig4 #ce1 showing what would be the probable phenomena attending such an upheaval as regards the behaviour of the disturbed portion of the crust1 and also that of the lava or semifluid matter beneath3 and1 as will be seen by the sketch1 a possible phase of the phenomena is the production of an elevated ridge or rampart at the points of disruption c c2 and where there is a ring of disruption1 as by our hypothesis there would be1 the ridge or rampart c c would be a circle4 ,in this drawing we see the cracking and distortion to which the elevated area would be subjected1 but of which1 as previously remarked1 the circular areas of the moon present no trace of residual appearance4 ,illustration3 ,,plate ,,xiv4 ,,plato4 ,those who have offered other explanations of these vast ring-formed mountain ranges1 have been no more happy in their conjectures4 ,m4 ,rozet1 who communicated a paper on selenology to the ,french ,academy in #ahdf1 put forth the following theory4 ,he argued that during the formation of the solid scoriaceous pelicules of the moon1 circular or tourbillonic movements were set up2 and these1 by throwing the scoria from the centre to the circumference1 caused an accumulation thereof at the limit of the circulation4 ,he considered that this phenomenon continued during the whole process of solidification1 but that the amplitude of the whirlpool diminished with the decreasing fluidity of the surface material4 ,further1 he suggested that when many vortices were formed1 and the distances of their centres1 taken two and two1 were less than the sums of their radii1 there resulted closed spaces terminated by arcs of circles2 and when for any two centres the distance was greater than the sum of the radii of action1 two separate and complete rings were formed4 ,we have only to remark on this1 that we are at a loss to account for the origination of such vorticose movements1 and ,m4 ,rozet is silent on the point4 ,if the great circles are to be referred to an original sea of molten matter1 it appears to us more feasible to consider that wherever we see one of them there has been1 at the centre of the ring1 a great outflow of lava that has flooded the surrounding surface4 ,then1 if from any cause1 and it is not difficult to assign one1 the outflow became intermittent1 or spasmodic1 or subject to sudden impulses1 concentric waves would be propagated over the pool and would throw up the scoria or the solidifying lava in a circular bank at the limit of the fluid area4 ,this hypothesis does not differ greatly from the ebullition theory proposed by ,professor ,dana1 the ,american geologist1 to explain these formations4 ,he considered that the lunar ring-mountains were formed by an action analogous to that which is exemplified on the earth in the crater of ,kilauea1 in the ,hawaiian islands4 ,this crater is a large open pit exceeding three miles in its longer diameter1 and nearly a thousand feet deep4 ,it has clear bluff walls round a greater part of its circuit1 with an inner ledge or plain at their base1 raised #cdj feet above the bottom4 ,this bottom is a plain of solid lavas1 entirely open to day1 which may be traversed with safety 7we are quoting ,professor ,dana's own statement written in #ahdf1 and therefore not correctly applying to the present time73 over it there are pools of boiling lava in active ebullition1 and one is more than a thousand feet in diameter4 ,there are also cones at times1 from a few yards to two or three thousand feet in diameter1 and varying greatly in angle of inclination4 ,the largest of these cones have a circular pit or crater at the summit4 ,the great pit itself is oblong1 owing to its situation on a fissure1 but the lakes upon its bottom are round1 and in them1 says ,professor ,dana1 8the circular or slightly elliptical form of the moon's craters is exemplified to perfection40 ,now ,dana refers this great pit crater and its contained lava-lakes to 8the fact that the action at ,kilauea is simply boiling1 owing to the extreme fluidity of the lavas4 ,the gases or vapours which produce the state of active ebullition escape freely in small bubbles1 with little commotion1 like jets over boiling water2 while at ,vesuvius and other like cones they collect in immense bubbles before they accumulate force enough to make their way through2 and consequently the lavas in the latter case are ejected with so much violence that they rise to a height often of many thousand feet and fall around in cinders4 ,this action builds up the pointed mountain1 while the simple boiling of ,kilauea makes no cinders and no cinder cones40 ,professor ,dana continues1 8,if the fluidity of lavas1 then1 is sufficient for this active ebullition1 we may have boiling going on over an area of an indefinite extent2 for the size of a boiling lake can have no limits except such as may arise from a deficiency of heat4 ,the size of the lunar craters is therefore no mystery4 ,neither is their circular form difficult of explanation2 for a boiling pool necessarily1 by its own action1 extends itself circularly around its centre4 ,the combination of many circles1 and the large sea-like areas are as readily understood40#aj ,in justice to ,professor ,dana it should be stated that he included in this theory of formation all lunar craters1 even those of small size and possessing central cones2 and he put forth his views in opposition to the eruptive theory which we have set forth1 and which was briefly given to the world more than twenty-five years ago4 ,as regards the smallest craters with cones1 we believe few geologists will refuse their compliance with the supposition that they were formed as our crater-bearing volcanoes were formed3 and we have pointed out the logical impossibility of assigning any limit of size beyond which the eruptive action could not be said to hold good1 so long as the central cone is present4 ,but when we come to ring-mountains having no cones1 and of such enormous size that we are compelled to hesitate in ascribing them to ejective action1 we are obliged to face the possibility of some other causation4 ,and1 failing an explanation of our own that satisfied us1 we have alluded to the few hypotheses proffered by others1 and of these ,professor ,dana's appears the most rational1 since it is based upon a parallel found on the earth4 ,in citing it1 however1 we do necessarily not endorse it4 ,,chapter ,x4 ,,peaks ,,and ,,mountain ,,ranges4 ,the lunar features next in order of conspicuity are the mountain ranges1 peaks1 and hill-chains1 a class of eminences more in common with terrestrial formations than the craters and circular structures that have engaged our notice in the preceding chapters4 ,in turning our attention to these features1 we are at the outset struck with the paucity on the lunar surface of extensive mountain systems as compared with its richness in respect of crateral formations2 and a field of speculation is opened by the recognition of the remarkable contrast which the moon thus presents to the earth1 where mountain ranges are the rule1 and craters like the lunar ones are decidedly exceptional4 ,another conspicuous but inexplicable fact is that the most important ranges upon the moon occur in the northern half of the visible hemisphere1 where the craters are fewest and the comparatively featureless districts termed 8seas0 are found4 ,the finest range is that named after our ,apennines and which is included in our illustrative ,plate1 ,no4 ,,ix4 ,it extends for about #dej miles and has been estimated to contain upwards of #cjjj peaks1 one of which--,mount ,huyghens--attains the altitude of #ah1jjj feet4 ,the ,caucasus is another lunar range which appears like a diverted northward extension of the ,apennines1 and1 although a far less imposing group than the last named1 contains many lofty peaks1 one of which approaches the altitude assigned to ,mount ,huyghens while several others range between #aa1jjj and #ad1jjj feet high4 ,another considerable range is the ,alps1 situated between the ,caucasus and the crater ,plato1 and reproduced on ,plate ,,xiv4 ,it contains some #gjj peaked mountains and is remarkable for the immense valley1 #hj miles long and about five broad1 that cuts it with seemingly artificial straightness2 and that1 were it not for the flatness of its bottom1 might set one speculating upon the probability of some extraneous body having rushed by the moon at an enormous velocity1 gouging the surface tangentially at this point and cutting a channel through the impeding mass of mountains4 ,there are other mountain ranges of less magnitude than the foregoing2 but those we have specified will suffice to illustrate our suggestions concerning this class of features4 ,illustration3 ,,plate ,,xv4 ,,mercator ,,campanus4 ,we remark1 too1 that there is a prevailing tendency of the ranges just mentioned to present their loftiest constituents in abrupt terminal lines1 facing nearly the same direction1 the reverse of that towards which they are carried by the moon's rotation2 and as they recede from the high terminal line1 the mountains gradually fall off in height1 so that in bulk the ranges present the 8crag and tail0 contour which individual hills upon the earth so frequently exhibit4 ,isolated peaks are found in small numbers upon the moon2 there are a few striking examples of them nevertheless1 and these are chiefly situated in the mountainous region just alluded to4 ,several are seen to the east 7right hand7 of the ,alpine range depicted on ,plate ,,xiv4 ,the best known of these is ,pico1 which rises abruptly from a generally smooth plain to a height of #gjjj feet4 ,it may be recognized as the lower of the two long shadowing spots located almost centrally above the crater ,plato in the illustration just mentioned4 ,above it1 at an actual distance of #dj miles1 there is another peak 7unnamed7 about #djjj feet high2 and away to the west1 beyond the small crater joined by a hill-ridge to ,plato1 is a third pyramidal mountain nearly as high as ,pico4 ,it seems natural to regard the great mountain chains as agglomerations of those peaks of which we have isolated examples in ,pico and its compeers1 and thus to consider that the formation of a mountain chain has been a multiplication of the process that formed the single pyramid-shaped eminences4 ,at first thought it might appear that the great mountain ranges were produced by bodily upthrustings of the crust of the moon by some subsurface convulsions4 ,but such an explanation could hardly hold in relation to the isolated peaks1 for it is difficult1 if not impossible1 to conceive that these abrupt mountains1 almost resembling a sugarloaf in steepness1 could have been protruded en masse through a smooth region of the crust4 ,on the contrary it is quite consistent with probability to suppose that they were built up by a slow process somewhat analogous to that to which we have ascribed the piling of the central cones of the great craters4 ,we believe they may be regarded as true mountains of exudation1 produced by the comparatively gentle oozing of lava from a small orifice and its solidification around it2 the vent however remaining open and the summit or discharging orifice continually rising with the growth of the mountain1 as indicated in the annexed cut1 ,fig4 #cf4 ,this process is well exemplified in the case of a water fountain playing during a severe frost2 the water as it falls around the lips of the orifice freezes into a hillock of ice1 through the centre of which1 however1 a vent for the fluid is preserved4 ,as the water trickles over the mound it is piled higher and higher by accumulating layers of ice1 till at length a massive cone is formed whose height will be determined by the force or 8head0 of the water4 ,substitute lava for water and we have at once a formative process which may very fairly be considered as that which has given rise to the isolated mountains of the moon4 ,illustration3 ,fig4 #cf4 ,illustration3 ,fig4 #cg4 ,illustration3 ,fig4 #ch4 ,illustration3 ,fig4 #ci4 ,there are upon the earth mountainous forms resembling the isolated peaks of the moon1 and which have been explained by a similar theory to the above4 ,we reproduce a figure of one observed by ,dana at ,hawaii 7,fig4 #cg71 and a sketch of another observed on the summit of the ,volcano of ,bourbon1 7,fig4 #ch72 we also reproduce 7,fig4 #ci7 an ideal section of the latter1 given by ,mr4 ,scrope1 and showing the successive layers of lava which would be disposed by just such an action as that manifested in the case of the freezing fountain2 and we quote that author's words in reference to this explanation of the formation of ,etna and other volcanic mountains4 8,on examining10 says ,mr4 ,scrope1#aa 8the structure of the mountain 7,etna7 we find its entire mass1 so far as it is exposed to view by denudation or other causes 7and one enormous cavity1 the ,val de ,bove penetrates deeply into its very heart71 to be composed of beds of lava-rock alternating more or less irregularly with layers of scori1 lapillo and ashes1 almost precisely identical in mineral character1 as well as in general disposition1 with those erupted by the volcano at known dates within the historical period4 ,hence we are fully justified in believing the whole mountain to have been built up in the course of ages in a similar manner by repeated intermittent eruptions4 ,and the argument applies by the rules of analogy to all other volcanic mountains1 though the history of their recent eruptions may not be so well recorded1 provided that their structure corresponds with1 and can be fairly explained by this mode of production4 ,it is also further applicable1 under the same reservation1 to all mountains composed entirely1 or for the most part1 of volcanic rocks1 even though they may not have been in eruption within our time40 ,to these illustrations furnished from ,scrope's work we add another1 copied from a photograph by ,professor ,piazzi ,smyth1 of a 8blowing cone0 at the base of ,teneriffe 7,fig4 #dj71 which is but one of many that are to be found on that mountain and which has been formed by a process similar to that we have been considering1 but acting upon a comparatively small scale4 ,professor ,smyth describes this cone as about #gj feet high and of parabolic figure1 composed of hard lava and with an upper aperture still yawning1 8whence the burning breath of fires beneath once issued in fury and with destruction40 ,illustration3 ,,plate ,,xvi ,,tycho1 ,,and ,,its ,,surroundings4 ,reverting now to the moon1 we remark that1 if the foregoing explanation of the isolated lunar peaks be tenable1 it should hold equally for the groups of them which we see in the lunar ,apennines1 ,alps1 ,caucasus and other ranges of like character4 ,there occur in some places intermediate groups which link the one to the other4 ,just above the crater ,archimedes1 on ,plate ,,ix41 for instance1 we see several single peaks and small clumps of them leading by successive multiple-peak examples to what may be called chains of mountains like many that are included in the contiguous ,apennine system4 ,and1 in view of this connexion between the single peaks and the mountain ranges formed of aggregations of such peaks1 it seems to us reasonable to conclude that the latter were formed by the comparatively slow escape of lava through multitudinous openings in a weak part of the moon's crust1 rather than to suppose that the crust itself has been bodily upheaved and retained in its disturbed position4 ,the high peaks that many mountains in such a chain exhibit accord better with the former than the latter explanation2 for it is difficult to imagine how such lofty eminences could be erected by an upheaval1 and we must remember that the moon has none of the denuding elements which are at work upon the earth1 weather-wearing its mountain forms into sharpness and steepness4#ab ,illustration3 ,fig4 #dj4 ,,small ,,volcanic ,,mountain ,,at ,,the ,,end ,,of ,a ,,street ,,at ,,teneriffe4 ,illustration3 ,fig4 #da4 ,and we have ground for believing the mountain-forming process on the moon to have been a comparatively gentle one1 in the fact that the mountain systems appear in regions otherwise little disturbed1 and where craters1 which have all the appearances of violent origin1 are few and far between4 ,evidently the mountain and crater-forming processes1 although both due to extrusive action1 were in some measure different1 and it is reasonable to suppose that the difference was in degree of intensity2 so that while a violent ejection of volcanic material would give rise to a crater1 a more gradual discharge would pile up a mountain4 ,in this view craters are evidences of eruptive1 and mountains of comparatively gentle exudative action4 ,we can hardly speculate with any degree of safety upon the cause of this varying intensity of volcanic discharge4 ,we may ascribe it to variation of depth of the initial disturbing force1 or to suddenness of its action2 or it may be that different degrees of fluidity of the lava have had modifying effects2 or on the other hand different qualities of the crust-material2 or yet again differences of period--the quieter extrusions having occurred at a time when the volcanic forces were dying down4 ,there is an alliance between lunar craters and mountains that goes far to show that there has been no radical difference in their origins4 ,for instance1 as we have previously pointed out1 craters in some cases run in linear groups1 as if in those cases they had been formed along a line of disruption or of least resistance of the crust2 and the mountain chains have a corresponding linear arrangement4 ,then we see craters and mountain chains disposed in what seem obviously the same arcs of disturbance4 ,thus ,copernicus 7,no4 #adg71 ,erastothenes 7,no4 #afh71 and the ,apennines appear to belong to one continuous line of eruption2 and it requires no great stretch of imagination to suppose that the ,caucasus1 ,eudoxus 7,no4 #bjh7 and ,aristotle 7,no4 #bji7 form a continuation of the same line4 ,then around the ,mare ,serenetatis we see mountainous ridges and craters alternating one with the other as though the exuding action there1 normally sufficient to produce the ridges1 had at some points become forcible enough to produce a crater4 ,again1 upon the very mountain ranges themselves1 as for instance among the ,apennines1 we find small craters occurring4 ,we see1 too1 that the great craters are in many cases surrounded by radiating systems of ridges which almost assume mountainous proportions1 and which are doubtless exuded matter from 8starred0 cracks1 the centres of which are occupied by the craters4 ,the same kind of ridges here and there occur apart from craters 7see for instance ,plate ,,xviii41 below ,aristarchus and ,herodotus7 and sometimes they occur in the neighbourhood of extensive cracks1 to which they also seem allied4 ,we must indeed regard a linear crack as the origin either of a ridge 7if the exudation is slight7 or of a mountain chain 7if the exudation is more copious7 or a string of craters 7if the extrusion rises to eruptive violence74 ,but the subject of cracks is important enough to be treated in a separate chapter4 ,we alluded in ,chap4 ,,iii4 to the phenomena of wrinkling or puckering as productive of certain mountainous formations2 and we pointed out the striking similarity in character of configuration between a shrivelled skin and a terrestrial mountain region4 ,we do not perceive upon the moon such a decided coincidence of appearances extending over any considerable portion of her surface2 but there are numerous limited areas where we behold mountainous ridges which partake strongly of the wrinkle character2 and in some cases it is difficult to decide whether the puckering agency or the exudative agency just discussed has produced the ridges4 ,the district bordering upon ,aristarchus and ,herodotus1 above referred to1 is of this doubtful character2 and a similar district is that contiguous to ,triesnecker 7,plate ,,xi47 ,there are1 however1 abundant examples of less prominent lines of elevation1 which may1 with more probability1 be ascribed to a veritable wrinkling or puckering action2 they are found over nearly the whole lunar surface1 some of them standing out in considerable relief1 and some merely showing gentle lines of elevation1 or giving the surface an undulating appearance4 ,a close examination of our picture-map 7,plate ,,iv47 will reveal very numerous examples1 especially in the south-east 7right-hand-upper7 quadrant4 ,some of these lines of tumescence are so slightly prominent that we may suppose them to have been caused by the action indicated by ,fig4 #f 7p4 #bh71 while others1 from their greater boldness1 appear to indicate a formative action analogous to that represented by ,fig4 #i 7p4 #bi74 ,illustration3 ,,ideal ,,sketch ,,of ,,pico ,,as ,,it ,,would ,,probably ,,appear ,,if ,,seen ,,by ,a ,,spectator ,,located ,,on ,,the ,,moon4 ,illustration3 ,,plate ,,xvii4 ,,wargentin4 ,,chapter ,,xi4 ,,cracks ,,and ,,radiating ,,streaks4 ,we have hitherto confined our attention to those reactions of the moon's molten interior upon its exterior which have been accompanied by considerable extrusions of sub-surface material in its molten or semi-solid condition4 ,we now pass to the consideration of some phenomena resulting in part from that reaction and in part from other effects of cooling1 which have been accompanied by comparatively little ejection or upflow of molten matter1 and in some cases by none at all4 ,of such the most conspicuous examples are those bright streaks that are seen1 under certain conditions of illumination1 to radiate in various directions from single craters1 and some of the individual radial branches of which extend from four to seven hundred miles in a great arc on the moon's surface4 ,there are several prominent examples of these bright streak systems upon the visible hemisphere of the moon2 the focal craters of the most conspicuous are ,tycho1 ,copernicus1 ,kepler1 ,aristarchus1 ,menelaus1 and ,proclus4 ,generally these focal craters have ramparts and interiors distinguished by the same peculiar bright or highly reflective material which shows itself with such remarkable brilliance1 especially at full moon3 under other conditions of illumination they are not so strikingly visible4 ,at or nearly full moon the streaks are seen to traverse over plains1 mountains1 craters1 and all asperities2 holding their way totally disregardful of every object that happens to lay in their course4 ,the most remarkable bright streak system is that diverging from the great crater ,tycho4 ,the streaks that can be easily individualized in this group number more than one hundred1 while the courses of some of them may be traced through upwards of six hundred miles from their centre of divergence4 ,those around ,copernicus1 although less remarkable in regard to their extent than those diverging from ,tycho1 are nevertheless in many respects well deserving of careful examination3 they are so numerous as utterly to defy attempts to count them1 while their intricate reticulation renders any endeavour to delineate their arrangement equally hopeless4 ,the fact that these bright streaks are invariably found diverging from a crater1 impressively indicates a close relationship or community of origin between the two phenomena3 they are obviously the result of one and the same causative action4 ,it is no less clear that the actuating cause or prime agency must have been very deep-seated and of enormous disruptive power to have operated over such vast areas as those through which many of the streaks extend4 ,with a view to illustrate experimentally what we conceive to have been the nature of this actuating cause1 we have taken a glass globe and1 having filled it with water and hermetically sealed it1 have plunged it into a warm bath3 the enclosed water1 expanding at a greater rate than the glass1 exerts a disruptive force on the interior surface of the latter1 the consequence being that at the point of least resistance1 the globe is rent by a vast number of cracks diverging in every direction from the focus of disruption4 ,the result is such a strikingly similar counterpart of the diverging bright streak systems which we see proceeding from ,tycho and the other lunar craters before referred to1 that it is impossible to resist the conclusion that the disruptive action which originated them operated in the same manner as in the case of our experimental illustration2 the disruptive force in the case of the moon being that to which we have frequently referred as due to the expansion which precedes the solidification of molten substances of volcanic character4 ,our illustration1 ,plate ,,xix41 is a photograph from one of many glass globes which we have cracked in the manner described3 a careful comparison between the arrangement of the divergent cracks represented in the photograph and those seen spreading from ,tycho and other lunar craters will1 we trust1 justify us in what we have stated as to the similarity of the causes which have produced such identical results4 ,the accompanying figures will further illustrate our views upon the causative origin of the bright streaks4 ,the primary action rent the solid crust of the moon and produced a system of radiating fissures 7,fig4 #db73 these immediately afforded egress for the molten matter beneath to make its appearance on the surface simultaneously along the entire course of every crack1 and irrespective of all surface inequalities or irregularities whatever 7,fig4 #dc74 ,we conceive that the upflowing matter spread in both directions sideways and in this manner produced streaks of very much greater width than the cracks or fissures up through which it made its way to the surface4 ,illustration3 ,fig4 #db4 ,,illustrative ,,of ,,the ,,radiating ,,cracks ,,which ,,precede ,,the ,,formation ,,of ,,the ,,bright ,,streaks4 ,in further elucidation of this part of our subject we may refer to a familiar but as we conceive cogent illustration of an analogous action in the behaviour of water beneath the ice of a frozen pond1 which1 on being fractured by some concentrated pressure1 or by a blow1 is well known to 8star0 into radiating or diverging cracks1 up through which the water immediately issues1 making its appearance on the surface of the ice simultaneously along the entire course of every crack1 and on reaching the surface1 spreading on both sides to a width much exceeding that of the crack itself4 ,illustration3 ,fig4 #dc4 ,,illustrative ,,of ,,the ,,radiating ,,bright ,,streaks4 ,if this familiar illustration be duly considered1 we doubt not it will be found to throw considerable light on the nature of those actions which have resulted in the bright streaks on the moon's surface4 ,some have attempted to explain the cause of these bright streaks by assigning them to streams of lava1 issuing from the crater at the centre of their divergence and flowing over the surface1 but we consider such an explanation totally untenable1 as any idea of lava1 be it ever so fluid at its first issue from its source1 flowing in streams of nearly equal width1 through courses several hundred miles long1 up hills1 over mountains1 and across plains1 appears to us beyond all rational probability4 ,illustration3 ,,plate ,,xviii4 ,,aristarchus ,,herodotus4 ,it may be objected to our explanation of the formation of these bright streaks1 that so far as our means of observation avail us1 we fail to detect any shadows from them or from such marginal edges as might be expected to result from a sideway-spreading outflow of lava from the cracks which afforded it exit in the manner described4 ,were the edges of these streaks terminated by cliff-like or craggy margins of such height as #cj or #dj feet1 we might just be able at low angles of illumination and under the most favourable circumstances of vision1 to detect some slight appearance of shadows2 but so far as we are aware1 no such shadows have been observed4 ,we are led to suppose that the impossibility of detecting them is due not to their absence but to the height of the margins being so moderate as not to cast any cognizable shadow1 inasmuch as an abrupt craggy margin of #aj or #ae feet high would1 under even the most favourable circumstances1 fail to render such visible to us4 ,reference to our ideal section of one of these bright streaks 7,fig4 #de71 will show how thin their edges may be in relation to their spreading width4 ,the absence of cognizable shadows from the bright streaks has led some observers to conclude that they have no elevation above the surface over which they traverse1 and it has therefore been suggested that their existence is due to possible vapours which may have issued through the cracks1 and condensed in some sublimated or pulverulent form along their courses1 the condensed vapours in question forming a surface of high reflective properties4 ,that metallic or mineral substances of some kinds do deposit on condensation very white powders1 or sublimates1 we are quite ready to admit1 and such explanation of the high luminosity of the bright streaks1 and of the craters situated at the foci or centres of their divergence is by no means improbable1 so far as concerns their mere brightness4 ,but as we invariably find a crater occupying the centre of divergence1 and such craters are possessed of all the characteristic features and details which establish their true volcanic nature as the results of energetic extrusions of lava and scoria1 we cannot resist the conclusion that the material of the crater1 and that of the bright streaks diverging from it1 are not only of a common origin1 but are so far identical that the only difference in the structure of the one as compared with the other is due to the more copious egress of the extruded or erupted matter in the case of the crater1 while the restricted outflow or ejection of the matter up through the cracks would cause its dispersion to be so comparatively gentle as to flood the sides of the cracks and spread in a thin sheet more or less sideways simultaneously along their courses4 ,there are indeed evidences in the wider of the bright streaks of their being the result of the outflow of lava through systems of cracks running parallel to each other1 the confluence of the lava issuing from which would naturally yield the appearance of one streak of great width4 ,some of those diverging from ,tycho are of this class2 many other examples might be cited1 among which we may name the wide streaks proceeding from the crater ,menelaus and also those from ,proclus4 ,some of these occupy widths upwards of #be miles--amply sufficient to admit of many concurrent cracks with confluent lava outflows4 ,we are disposed to consider as related to the fore-mentioned radiating streaks1 the numerous1 we may say the multitudinous1 long and narrow chasms that have been sometimes called 8canals0 or 8rills10 but which are so obviously cracks or chasms1 that it is desirable that this name should be applied to them rather than one which may mislead by implying an aqueous theory of formation4 ,these cracks1 singly and in groups1 are found in great numbers in many parts of the moon's surface4 ,as a few of the more conspicuous examples which our plates exhibit we may refer to the remarkable group west of ,treisnecker 7,plate ,,xi471 the principal members of which converge to or cross at a small crater1 and thus point to a continuity of causation therewith analogous to the evident relation between the bright streaks and their focal craters4 ,less remarkable1 but no less interesting1 are those individual examples that appear in the region north of 7below7 the ,apennines 7,plate ,,ix471 and some of which by their parallelism of direction with the mountain-chain appear to point to a causative relation also4 ,there is one long specimen1 and several shorter in the immediate neighbourhood of ,mercator and ,campanus 7,plate ,,xv472 and another curious system of them1 presenting suggestive contortions1 occurs in connection with the mountains ,aristarchus and ,herodotus 7,plate ,,xviii474 ,others1 again1 appear to be identified with the radial excrescences about ,copernicus 7,plate ,,viii474 ,capuanus1 ,agrippa1 and ,gassendi1 among other craters1 have more or less notable cracks in their vicinities4 ,some of these chasms are conspicuous enough to be seen with moderate telescopic means1 and from this maximum degree of visibility there are all grades downwards to those that require the highest optical powers and the best circumstances for their detection4 ,the earlier selenographers detected but a few of them4 ,schroeter noted only #aa2 ,lohrman recorded #ge more2 ,beer and ,maedler added #ee to the list1 while ,schmidt of ,athens raised the known number to #dbe1 of which he has published a descriptive catalogue4 ,we take it that this increase of successive discoveries has been due to the progressive perfection of telescopes1 or1 perhaps1 to increased education1 so to speak1 of the eye1 since ,schmidt's telescope is a much smaller instrument than that used by ,beer and ,maedler1 and is regarded by its owner as an inferior one for its size4 ,we doubt not that there are hundreds more of these cracks which more perfect instruments and still sharper eyes will bring to knowledge in the future4 ,while these chasms have all lengths from #aej miles 7which is about the extent of those near ,treisnecker7 down to a few miles1 they appear to have a less variable breadth1 since we do not find many that at their maximum openings exceed two miles across2 about a mile or less is their usual width throughout the greater part of their length1 and generally they taper off to invisibility at their extremities1 where they do not encounter and terminate at a crater or other asperity1 which is1 however1 sometimes the case4 ,of their depth we can form no precise estimate1 though from the sharpness of their edges we may conclude that their sides approach perpendicularity1 and1 therefore1 that their depth is very great2 we have elsewhere suggested ten miles as a possible profundity4 ,in a few cases1 and under very favourable circumstances1 we have observed their generally black interiors to be interrupted here and there with bright spots suggestive of fragments from the sides of the cracks having fallen into the opening4 ,in seeking an explanation of these cracks1 two possible causes suggest themselves4 ,one is the expansion of subsurface matter1 already suggested as explanatory of the bright streaks2 the other1 a contraction of the crust by cooling4 ,we doubt not that both causes have been at work1 one perhaps enhancing the other4 ,where1 as in the cases we have pointed out1 there are cracks which are so connected with craters as to imply relationship1 we may conclude that an upheaving or expansive force in the sublunar molten matter has given rise to the cracks1 and that the central craters have been formed simultaneously1 by the release1 with ejective violence1 of the matter from its confining crust4 ,the nature of the expansive force being assumed that of solidifying matter1 the wide extent of some chasms indicates a deep location of that force4 ,and depth in this matter implies lateness 7in the scale of selenological time7 of operation1 since the central portions of the globe would be the last to cool4 ,now1 we have evidence of comparative lateness afforded by the fact that in many cases the cracks have passed through craters and other asperities which thus obviously existed before the cracking commenced2 and thus1 so far1 the hypothesis of the expansion-cracking is supported by absolute fact4 ,it may be objected that such an upheaving force as we are invoking1 being transitory1 would allow the distended surface to collapse again when it ceased to operate1 and so close the cracks or chasms it produced4 ,but we consider it not improbable that in some cases1 as a consequence of the expansion of subsurface matter1 an upflow thereof may have partially filled the crack1 and by solidifying have held it open2 and it is rational to suppose that there have been various degrees of filling and even of overflow--that in some cases the rising matter has not nearly reached the edge of the crack1 as in ,fig4 #dd1 while in others it has risen almost to the surface1 and in some instances has actually overrun it and produced some sort of elevation along the line of the crack1 like that represented sectionally in ,fig4 #de4 ,it is probable that some of the slightly tumescent lines on the moon's surface have been thus produced4 ,illustration3 ,,plate ,,xix4 ,,glass ,,globe ,,cracked ,,by ,,internal ,,pressure4 ,illustration3 ,fig4 #dd4 ,illustration3 ,fig4 #de4 ,we have suggested shrinkage as a possible explanation of some cracks4 ,it could hardly have been the direct cause of those compound ones which are distinguished by focal craters1 though it may have been a co-operative cause1 since the contracting tendency of any area of the crust1 by so to speak weakening it1 may have virtually increased the strength of an upheaving force and thus have aided and localized its action4 ,we see1 however1 no reason why the inevitable ultimate contraction which must have attended the cooling of the moon's crust1 even when all internal reactions upon it had ceased1 should not have created a class of cracks without accompanying craters1 while it would doubtless have a tendency to increase the length and width of those already existing from any other cause4 ,some of the more minute clefts1 which presumably exist in greater numbers than we yet know of1 may doubtless be ascribed to this effect of cooling contraction4 ,in this view we should have to regard such cracks as the latest of all lunar features4 ,whether the agency that produced them is still at work--whether the cracks are on the increase--is a question impossible of solution3 for reasons to be presently adduced1 we incline to believe that all cosmical heat passed from the moon1 and therefore that it arrived at its present1 and apparently final1 condition ages upon ages ago4 ,besides the ridges spoken of on p4 #adj1 and regarded as cracks up through which matter has been extruded1 there are numerous ridges of greater or less extent1 which we conceive are of the nature of wrinkles1 and have been produced by tangential compression due to the collapse of the moon's crust upon the shrunken interior1 as explained and illustrated in ,chap4 ,,iii4 ,the distinguishing feature of the two classes of phenomena we consider to be the presence of a serrated summit in those of the extruded class1 while those produced by 8wrinkling0 action have their summits comparatively free from serration or marked irregularity4 ,,chapter ,,xii4 ,,colour ,,and ,,brightness ,,of ,,lunar ,,details3 ,,chronology ,,of ,,formations1 ,,and ,,finality ,,of ,,existing ,,features4 ,speaking generally1 the details of the lunar surface seem to us to be devoid of colour4 ,to the naked eye of ordinary sensitiveness the moon appears to possess a silvery whiteness3 more critical judges of colour would describe it as presenting a yellowish tinge4 ,sir ,john ,herschel1 during his sojourn at the ,cape of ,good ,hope1 had frequent opportunities of comparing the moon's lustre with that of the weathered sandstone surface of ,table ,mountain1 when the moon was setting behind it1 and both were illuminated under the same direction of sunlight2 and he remarked that the moon was at such times 8scarcely distinguishable from the rock in apparent contact with it40 ,although his observations had reference chiefly to brightness1 it can hardly be doubted that similarity of colour is also implied2 for any difference in the tint of the two objects would have precluded the use of the words 8scarcely distinguishable20 a difference of colour interfering with a comparison of lustre in such an observation1 though it must be remembered that he observed through a dense stratum of atmosphere4 ,viewed in the telescope1 the same general yellowish-white colour prevails over all the moon1 with a few exceptions offered by the so-called seas4 ,the ,mare ,crisium1 ,mare ,serenetatis1 and ,mare ,humorum have somewhat of a greenish tint2 the ,palus ,somnii and the circular area of ,lichtenberg incline to ruddiness4 ,these tints are1 however1 extremely faint1 and it has been suggested by ,arago that they may be mere effects of contrast rather than actual colouration of the surface material4 ,this1 however1 can hardly be the case1 since all the 8seas0 are not alike affected2 those that are slightly coloured are1 as we have said1 some green and some red1 and contrast could scarcely produce such variations4 ,the supposition of vegetation covering these great flats and giving them a local colour is in our view still more untenable1 in the face of the arguments that we shall presently adduce against the possibility of vegetable life existing upon the moon4 ,it appears to us more rational to consider the tints due to actual colour of the material 7presumably lava or some once fluid mineral substance7 that has covered these areas2 and it may well be conceived that the variety of tint is due to different characters of material1 or even various conditions of the same material coming from different depths below the lunar surface2 and we may reasonably suppose that the same variously-coloured substances occur in the rougher regions of the lunar surface1 but that they exist there in patches too small to be recognized by us1 or are 8put out0 by the brightness to which polyhedral reflexion gives rise4 ,seeing that volcanic action has had so large a share in giving to the moon's surface its structural character1 analogy of the most legitimate order justifies us in concluding not only that the materials of that surface are of kindred nature to those of the unquestionably volcanic portions of the earth1 but also that the tints and colours that characterize terrestrial volcanic and ,plutonian products have their counterparts on the moon4 ,those who have seen the interior and surroundings of a terrestrial volcano after a recent eruption1 and before atmospheric agents have exercised their dimming influences1 must have been struck with the colours of the erupted materials themselves and the varied brilliant tints conferred on these materials by the sublimated vapours of metals and mineral substances which have been deposited upon them4 ,if1 then1 analogy is any guide in enabling us to infer the appearance of the invisible from that which we know to be of kindred nature and which we have seen1 we may justly conclude that were the moon brought sufficiently near to us to exhibit the minute characteristics of its surface1 we should behold the same bright and varied colours in and around its craters that we behold in and about those of the earth2 and in all probability the coloured materials of lunar volcanoes would be more fresh and vivid than those of the earth by reason of the absence of those atmospheric elements which tend so rapidly to impair the brightness of coloured surfaces exposed to their influence4 ,situated as we are1 however1 as regards distance from the moon1 we have no chance of perceiving these local colours in their smaller masses2 but it is by no means improbable1 as we have suggested1 that the faint tints exhibited by the great plains are due to broad expanses of coloured volcanic material4 ,but if we fail to perceive diversity of colour upon the lunar surface1 we are in a very different position in regard to diversity of brightness or variable light-reflective power of different districts and details4 ,this will be tolerably obvious to those casual observers who have remarked nothing more of the moon's physiography than the resemblance to a somewhat lugubrious human countenance which the full moon exhibits1 and which is due to the accidental disposition of certain large and small areas of surface material which have less of the light-reflecting property than other portions2 for since all parts seen by a terrestrial observer may be said to be equally shone upon by the sun1 it is clear that apparently bright and shaded parts must be produced by differences in the nature of the surface as regards power of reflecting the light received4 ,when we turn to the telescope and survey the full disc of the moon with even a very moderate amount of optical aid1 the meagre impression as to variety of degree of brightness which the unassisted eye conveys is vastly extended and enhanced1 for the surface is seen to be diversified by shades of brilliancy and dullness from almost glittering white to sombre grey3 and this variety of shading is rendered much more striking by shielding the eye with a dusky glass from the excessive glare1 which drowns the details in a flood of light4 ,under these circumstances the varieties of light and shade become almost bewildering1 and defy the power of brush or pencil to reproduce them4 ,we may1 however1 realize an imperfect idea of this characteristic of the lunar surface by reference to the self-drawn portrait of the full moon upon ,plate ,,iii4 ,this is1 in fact1 a photograph taken from the full moon itself1 and enlarged sufficiently to render conspicuous the spots and large and small regions that are strikingly bright in comparison with what may in this place be described as the 8ground0 of the disc4 ,as an example of a wide and irregularly extensive district of highly reflective material1 the region of which ,tycho is the central object1 is very remarkable4 ,we may refer also to the bright 8splashes0 of which ,copernicus and ,kepler are the centres4 ,so brilliant are these spots that they can easily be detected by the unassisted eye about the time of full moon4 ,still brighter but less conspicuous by its size is the crater ,aristarchus1 which shines with specular brightness1 and almost induces the belief that its interior is composed of some vitreous-surfaced matter3 the highly reflective nature of this object has often caused it to become conspicuous when in the dark hemisphere of the moon1 unilluminated by the sun1 and lighted only by the light reflected from the earth4 ,at these times it appears so bright that it has been taken for a volcano in actual eruption1 and no small amount of popular misconception at one time arose therefrom concerning the conditions of the moon as respects existing volcanic activity--a misconception that still clings to the minds of many4 ,the parts of the surface distinguished by deficiency of reflecting power are conspicuous enough4 ,we may cite1 however1 as an example of a detail portion especially remarkable for its dingy aspect1 the interior of the crater ,plato1 which is one of the darkest spots 7the darkest well defined one7 upon the hemisphere of the moon visible to us4 ,for facilitating reference to shades of luminosity1 ,schroeter and ,lohrman assorted the variously reflective parts into #aj grades1 commencing with the darkest4 ,grades #a to #c comprised the various deep greys2 #d and #e the light greys2 #f and #g white2 and #h to #aj brilliant white4 ,the spots ,grimaldi and ,riccioli came under class #a of this notation2 ,plato between #a and #b4 ,the 8seas0 generally ranged from #b to #c2 the brightest mountainous portions mostly between degrees #d and #f2 the crater walls and the bright streaks came between these and the bright peaks1 which fell under the #ith grade4 ,the maximum brightness1 the #ajth grade1 is instanced only in the ease of ,aristarchus and a point in ,werner1 though ,proclus nearly approaches it1 as do many bright spots1 chiefly the sites of minute craters1 which make their appearance at the time of full moon4 ,in photographic pictures produced by the moon of itself1 there is always an apparent exaggeration in the relation of light to dark portions of the disc4 ,the dusky parts look1 upon the photograph1 much darker than to the eye directed to the moon itself1 whether assisted or not by optical appliances4 ,it may be that the real cause of this discrepancy is that the eye fails to discover the actual difference upon the moon itself1 being insensible to the higher degrees of brightness or not estimating them at their proper brilliance with respect to parts less bright4 ,on the other hand1 it is probable that the enhanced contrast in the photograph is due to some peculiar condition of the darker surface matter affecting its power of reflecting the actinic constituent of the rays that fall upon it4 ,the study of the varying brightness or reflective power of different regions and spots of the lunar disc leads us to the consideration of the relative antiquity of the surface features2 for it is hardly possible to regard these variations attentively without being impressed with the conviction that they have relation to some chronological order of formation4 ,we cannot1 in the first place1 resist the conviction that the brightest features were the latest formed2 this strikes us as evident on prim facie grounds2 but it becomes more clearly so when we remark that the bright formations1 as a rule1 overlie the duller features4 ,the elevated parts of the crust are brighter than the 8seas0 and other areas2 and it is pretty clear that the former are newer than the latter1 upon which they appear to be super-imposed1 or through which they seem to have extruded4#ac ,the vast dusky plains are in every instance more or less sprinkled with spots and minute craters1 and these last were obviously formed after the area that contains them4 ,one is almost disposed to place the order of formations in the order of relative brightness1 and so consider the dingiest parts the oldest and the brightest spots and craters the newest features1 though1 in the absence of an atmosphere competent to impair the reflective power of the surface materials1 we are unable to justify this classification by suggesting a cause for such a deterioration by time as the hypothesis pre-supposes4 ,as we have entered upon the question of relative age of the lunar features1 we may remark that there are evidences of various epochs of formation of particular classes of details1 irrespective of their condition in respect of brightness1 or1 as we may say1 freshness of material4 ,as a rule1 the large craters are older than the small ones4 ,this is proved by the fact that a large object of this class is never seen to interfere with or overlap a small one4 ,those of nearly equal size are1 however1 seen to overlap one another as though several eruptions of equal intensity had occurred from the same source at different points4 ,this is strikingly instanced in the group of craters situated in the position #ce-ada on our map1 the order of formation of each of which is clearly apparent4 ,the region about ,tycho offers an inexhaustible field for study of these phenomena of overlapping or interpolating craters1 and it will be found1 with very few exceptions1 that the smaller crater is the impinging or parasitical one1 and must therefore have been formed after the larger1 upon which it intrudes or impinges4 ,there are frequent cases in which a large crater has had its rampart interrupted by a lesser one1 and this again has been broken into by one still smaller2 and instances may be found where a fourth crater smaller than all has intruded itself upon the previous intruder4 ,the general tendency of these examples is to show that the craters diminished in size as the moon's volcanic energy subsided3 that the largest were produced in the throes of its early violence1 and that the smallest are the results of expiring efforts possibly impeded through the deep-seatedness of the ejective source4 ,another general fact of this chronological order is that the mountain chains are never seen to intrude upon formations of the crater order4 ,we do not anywhere find that a mountain chain runs absolutely into or through a crater2 but1 on the other hand1 we do find that craters have formed on mountain chains4 ,this leads unmistakably to the inference that the craters were not formed before their allied mountain chains2 and we might assume therefore that the mountains generally are the older formations1 but that there is nothing to prove that the two classes of features1 where they intermingle1 as in the ,apennines and ,caucasus1 were not erupted cotemporaneously4 ,illustration3 ,,plate ,,xx4 ,,overlapping ,,craters4 ,upon the assumption that the latest ejected or extruded matter is that which is brightest1 we should place the bright streaks among the more recent features4 ,be this as it may1 it is tolerably certain that the cracks1 whose apparently close relation to the radiating streaks we have endeavoured to point out1 are relatively of a very late formative period4 ,we are indeed disposed to consider them as the most recent features of all3 the evidence in support of this consideration being the fact that they are sometimes found intersecting small craters that1 from the way in which they are cut through by the cracks1 must have been in situ before the cracking agency came into operation4 ,it is in accordance with our hypothesis of the moon's transition from a fluid to a solid body to consider that a cracking of the surface would be the latest of all the phenomena produced by contraction in final cooling4 ,the foregoing remarks naturally lead us to the question whether changes are still going on upon the surface of our satellite3 whether there is still left in it a spark of its volcanic activity1 or whether that activity has become totally extinct4 ,we shall consider this question from the observational and theoretical point of view4 ,first as regards observations4 ,this much may be affirmed indisputably--that no object or detail visible to the earliest selenographers 7whose period may be dated #bjj years back7 has altered from the date of their maps to the present4 ,when we pass from the bolder features to the more minute details we find ourselves at a loss for materials for forming an inference2 the only map pretending to accuracy even of the larger among small objects being that of ,beer and ,maedler1 which1 truly admirable as it is1 is not very safely to be relied upon for settling any question of alleged change1 on account of the conventional system adopted for exhibiting the forms of objects1 every object being mapped rather than drawn1 and shown as it never is or can be presented to view on the moon itself4 ,this difficulty would present itself if a question of change were ever raised upon the evidence of ,beer and ,maedler's map3 it may indeed have prevented such a question being raised1 for certainly no one has hitherto been bold enough to assert that any portion or detail of the map fails to represent the actual state of the moon at the present time4 ,in default of published maps1 we are thrown for evidence on this question upon observations and recollections of individual observers whose familiarity with the lunar details extends over lengthy periods4 ,speaking for ourselves1 and upon the strength of close scrutinies continued with assiduity through the past thirty years1 we may say that we have never had the suspicion suggested to our eye of any actual change whatever having taken place in any feature or minute detail of the lunar surface2 and our scrutinies have throughout been made with ample optical means1 mostly with a #bj-;inch reflector4 ,this experience has made us not unnaturally in some slight degree sceptical concerning the changes alleged to have been detected by others4 ,those asserted by ,schroeter and ,gruithuisen were long ago rejected by ,beer and ,maedler1 who explained them1 where the accuracy of the observer was not questioned1 by variations of illumination1 a cause of illusory change which is not always sufficiently taken into account4 ,a notable instance of this deception occurred a few years ago in the case of the minute bright crater ,linn1 which was for a considerable period declared1 upon the strength of observations of very promiscuous character1 to be varying in form and dimensions almost daily1 but the alleged constant changes of which have since been tacitly regarded as due to varying circumstances of illumination induced by combinations of libratory effects with the ordinary changes depending upon the direction of the sun's rays as due to the age of the moon4 ,this explanation does not1 however1 dispose of the question whether the crater under notice suffered any actual change before the hue and cry was raised concerning it4 ,attention was first directed to it by ,schmidt1 of ,athens1 whose powers of observation are known to be remarkable1 and whose labours upon the moon are of such extent and minuteness as to claim for his assertions the most respectful consideration4#ad ,he affirmed in #ahff that the crater at that date presented an appearance decidedly different from that which it had had since #ahda3 that whereas it had been from the earlier epoch always easily seen as a very deep crater1 in ,october #ahff and thenceforward it presented only a white spot1 with at most but a very shallow aperture1 very difficult to be detected4 ,schmidt is one of the very few observers whose long familiarity with the moon entitles him to speak with confidence upon such a question as that before us upon the sole strength of his own experience2 and this case is but an isolated one1 at least it is the only one he has brought forward4 ,he is1 however1 still firmly convinced that it is an instance of actual change1 and not an illusion resulting from some peculiar condition of illumination of the object4 ,it should be added also on this side of the discussion that an ,english observer1 the ,rev4 ,t4 ,w4 ,webb1 while apparently indisposed to concede the supposition of any notable changes in the lunar features1 has yet found from his own observations that1 after all due allowance for differences of light and shade upon objects at different times1 there is still a 8residuum of minute variations not thus disposed of0 which seem to indicate that eruptive action in the moon has not yet entirely died out1 though its manifestation at present is very limited in extent4 ,it appears to us that1 if evidence of continuing volcanic action is to be sought on the moon1 the place to look for it is around the circumference of the disc1 where eruption from any marginal orifice would manifest itself in the form of a protruding haziness1 somewhat as illustrated to an exaggerated extent in the annexed cut4 ,illustration3 ,fig4 #df4 ,the theoretical view of the question1 which we have now to consider1 has led us1 however1 to the strong belief that no vestige of its former volcanic activity lingers in the moon--that it assumed its final condition an inconceivable number of ages ago1 and that the high interest which would attach to the close scrutiny of our satellite if it were still the theatre of volcanic reactions cannot be hoped for4 ,if it be just and allowable to assume that the earth and the moon were condensed into planetary form at nearly the same epoch 7and the only rational scheme of cosmogony justifies the assumption7 then we may institute a comparison between the condition of the two bodies as respects their volcanic age1 using the one as a basis for inference concerning the state of the other4 ,we have reason to believe that the earth's crust has nearly assumed its final state so far as volcanic reactions of its interior upon its exterior are concerned3 we may affirm that within the historical period no igneous convulsions of any considerable magnitude have occurred2 and we may consider that the volcanoes now active over the surface of the globe represent the last expiring efforts of its eruptive force4 ,now in the earth we perceive several conditions wherefrom we may infer that it parted with its cosmical heat 7and therefore with its prime source of volcanic agency7 at a rate which will appear relatively very slow when we come to compare the like conditions in the moon4 ,we may1 we think1 take for granted that the surface of a planetary body generally determines its heat dispersing power1 while its volume determines its heat retaining power4 ,given two spherical bodies of similar material but of unequal magnitude and originally possessing the same degree of heat1 the smaller body will cool more rapidly than the larger1 by reason of the greater proportion which the surface of the smaller sphere bears to its volume than that of the larger sphere to its volume--this proportion depending upon the geometrical ratio which the surfaces of spheres bear to their volumes1 the contents of spheres being as the cubes and the surfaces as the squares of their diameters4 ,the volume of the earth is #di times as great as that of the moon1 but its surface is only #ac times as great2 there is consequently in the earth a power of retaining its cosmical heat nearly four times as great as in the case of the moon2 in other words1 the moon and earth being supposed at one time to have had an equally high temperature1 the moon would cool down to a given low temperature in about one fourth the time that the earth would require to cool to the same temperature4 ,but the earth's cosmical heat has without doubt been considerably conserved by its vaporous atmosphere1 and still more by the ocean in its antecedent vaporous form4 ,yet notwithstanding all this1 the earth's surface has nearly assumed its final condition so far as volcanic agencies are concerned3 it has so far cooled as to be subject to no considerable distortions or disruptions of its surface4 ,what then must be the state of the moon1 which1 from its small volume and large proportionate area1 parted with its heat at the above comparatively rapid rate8 ,the matter of the moon is1 too1 less dense than the earth1 and hence doubtless from this cause disposed to more rapid cooling2 and it has no atmosphere or vaporous envelope to retard its radiating heat4 ,we are driven thus to the conclusion that the moon's loss of cosmical heat must have been so rapid as to have allowed its surface to assume its final conformation ages on ages ago1 and hence that it is unreasonable and hopeless to look for evidence of change of any volcanic character still going on4 ,we conceive it possible1 however1 that minute changes of a non-volcanic character may be proceeding in the moon1 arising from the violent alternations of temperature to which the surface is exposed during a lunar day and night4 ,the sun1 as we know1 pours down its heat unintermittingly for a period of fully #cjj hours upon the lunar surface1 and the experimental investigations of ,lord ,rosse1 essentially confirmed by those of the ,french observer1 ,marie ,davy1 show that under this powerful insolation the surface becomes heated to a degree which is estimated at about #ejj of ,fahrenheit's scale1 the fusing point of tin or bismuth4 ,this heat1 however1 is entirely radiated away during the equally long lunar night1 and1 as ,sir ,john ,herschel surmised1 the surface probably cools down again to a temperature as low as that of interstellar space3 this has been assumed as representing the absolute zero of temperature1 which has been calculated from experiments to be #bej below the zero of ,fahrenheit's scale4 ,now such a severe range of heat and cold can hardly be without effect upon some of the component materials of the lunar surface4#ae ,if there be any such materials as the vitreous lavas that are found about our volcanoes1 such as obsidian for instance1 they are doubtless cracked and shivered by these extreme transitions of temperature2 and this comparatively rapid succession of changes continued through long ages would1 we may suppose1 result in a disintegration of some parts of the surface and at length somewhat modify the selenographic contour4 ,it is1 however1 possible that the surface matter is mainly composed of more crystalline and porous lavas1 and these might withstand the fierce extremes like the 8fire-brick0 of mundane manufacture1 to which in molecular structure they may be considered comparable4 ,lavas as a rule are 7upon the earth7 of this unvitreous nature1 and if they are of like constitution on the moon1 there will be little reason to suspect changes from the cause we are considering4 ,where1 however1 the material1 whatever its nature1 is piled in more or less detached masses1 there will doubtless be a grating and fracturing at the points of contact of one mass with another1 produced by alternate expansions and contractions of the entire masses1 which in the long run of ages must bring about dislocations or dislodgments of matter that might considerably affect the surface features from a close point of view1 but which can hardly be of sufficient magnitude to be detected by a terrestrial observer whose best aids to vision give him no perception of minute configurations4 ,and it must always be borne in mind that changes can only be proved by reference to previous observations and delineations of unquestionable accuracy4 ,speaking by our own lights1 from our own experience and reasoning1 we are disposed to conclude that in all visible aspects the lunar surface is unchangeable1 that in fact it arrived at its terminal condition eons of ages ago1 and that in the survey of its wonderful features1 even in the smallest details1 we are presented with the sight of objects of such transcendent antiquity as to render the oldest geological features of the earth modern by comparison4 ,,chapter ,,xiii4 ,,the ,,moon ,,as ,a ,,world3 ,,day ,,and ,,night ,,upon ,,its ,,surface4 ,a wide interest1 if not a deep one1 attaches to the general question as to the existence of living beings1 or at least the possibility of organic existence1 on planetary bodies other than our own4 ,the question has been examined in all ages1 by the lights of the science peculiar to each4 ,with every important accession to our astronomical knowledge it has been re-raised3 every considerable discovery has given rise to some new step or phase in the discussion1 and in this way there has grown up a somewhat extensive literature exclusively relating to mundane plurality4 ,it will readily be understood that the moon1 from its proximity to the earth1 has from the first received a large1 perhaps the largest1 share of attention from wanderers into this field of speculation3 and we might add greatly to the bulk of this volume by merely reviewing some of the more curious and1 in their way1 instructive conjectures specially relating to the moon as a world--to imaginary journeys towards her1 and to the beings conjectured to dwell upon and within her4 ,this1 however1 we feel there is no occasion to do1 for it is our purpose merely to point out the two or three almost conclusive arguments against the possibility of any life1 animal or vegetable1 having existence on our satellite4 ,we well know what are the requisite conditions of life on the earth2 and we can go no further for grounds of inference2 for if we were to start by assuming forms of life capable of existence under conditions widely and essentially different from those pertaining to our planet1 there would be no need for discussing our subject further3 we could revel in conjectures1 without a thought as to their extravagance4 ,the only legitimate phase of the question we can entertain is this3--can there be on the moon any kind of living things analogous to any kind of living things upon the earth8 ,and this question1 we think1 admits only of a negative answer4 ,the lowest forms of vitality cannot exist without air1 moisture1 and a moderate range of temperature4 ,it may be true1 as recent experiments seem to show1 that organic germs will retain their vitality without either of the first1 and with exposure to intense cold and to a considerable degree of heat2 and it is conceivable that the mere germs of life may be present on the moon4#af ,but this is not the case with living organisms themselves4 ,we have1 in ,chapter ,v41 specially devoted to the subject1 cited the evidence from which we know that there can be at the most1 no more air on the moon than is left in the receiver of an air-pump after the ordinary process of exhaustion4 ,and with regard to moisture1 it could not exist in any but the vaporous state1 and we know that no appreciable amount of vapour can be discovered by any observation 7and some of them are crucial enough7 that we are capable of making4 ,we may suppose it just within the verge of possibility that some low forms of vegetation might exist upon the moon with a paucity of air and moisture such as would be beyond even our most severe powers of detection3 but granting even this1 we are met by the temperature difficulty2 for it is inconceivable that any plant-life could survive exposure first to a degree of cold vastly surpassing that of our arctic regions1 and then in a short time 7#ad days7 to a degree of heat capable of melting the more fusible metals--the total range being equal1 as we have elsewhere shown1 to perhaps #fjj or #gjj degrees of our thermometric scale4 ,the higher forms of vegetation could not reasonably be expected to exist under conditions which the lower forms could not survive4 ,and as regards the possibility of the existence of animal life in any form or condition on the lunar surface1 the reasons we have adduced in reference to the non-existence of vegetable life bear still more strongly against the possibility of the existence of the former4 ,we know of no animal that could live in what may be considered a vacuum and under such thermal conditions as we have indicated4 ,illustration3 ,,plate ,,xxi4 ,,normal ,,lunar ,,crater4 ,as to man1 aronautic experience teaches us that human life is endangered when the atmosphere is still sufficiently dense to support #ab inches of mercury in the barometer tube2 what then would be his condition in a medium only sufficiently dense to sustain one-tenth of an inch of the barometric column8 ,we have evidence from the most delicate tests that no atmosphere or vapour approaching even this degree of attenuation exists around the moon's surface4 ,taking all these adverse conditions into consideration we are in every respect justified in concluding that there is no possibility of animal or vegetable life existing on the moon1 and that our satellite must therefore be regarded as a barren world4 99 99 99 99 99 99 99 99 ,after this disquisition upon lunar uninhabitability it may appear somewhat inconsistent for us to attempt a description of the scenery of the moon and some other effects that would be visible to a spectator1 and of which he would be otherwise sensible1 during a day and a night upon her surface4 ,but we can offer the sufficient apology that an imaginary sojourn of one complete lunar day and night upon the moon affords an opportunity of marshalling before our readers some phenomena that are proper to be noticed in a work of this character1 and that have necessarily been passed over in the series of chapters on consecutive and special points that have gone before4 ,it may be urged that1 in depicting the moon from such a standpoint as that now to be taken1 we are describing scenes that never have been such in the literal sense of the word1 since no eye has ever beheld them4 ,still we have this justification--that we are invoking the conception of things that actually exist2 and that we are not1 like some imaginary voyagers to the moon1 indulging in mere flights of fancy4 ,although it is impossible for a habitant of this earth fully to realise existence upon the moon1 it is yet possible1 indeed almost inevitable1 for a thoughtful telescopist--watching the moon night after night1 observing the sun rise upon a lunar scene1 and noting the course of effects that follow till it sets--it is almost inevitable1 we say1 for such an observer to identify himself so far with the object of his scrutiny1 as sometimes to become in thought a lunar being4 ,seated in silence and in solitude at a powerful telescope1 abstracted from terrestrial influences1 and gazing upon the revealed details of some strikingly characteristic region of the moon1 it requires but a small effort of the imagination to suppose one's self actually upon the lunar globe1 viewing some distant landscape thereupon2 and under these circumstances there is an irresistible tendency in the mind to pass beyond the actually visible1 and to fill in with what it knows must exist those accessory features and phenomena that are only hidden from us by distance and by our peculiar point of view4 ,where the material eye is baffled1 the clairvoyance of reason and analogy comes to its aid4 ,let us then endeavour to realize the strange consequences which the position and conditions of the moon produce upon the aspect of a lunar landscape in the course of a lunar day and night4 ,the moon's day is a long one4 ,from the time that the sun rises upon a scene#ag till it sets1 a period of #cjd hours elapses1 and of course double this interval passes between one sunrise and the next4 ,the consequences of this slow march of the sun begin to show themselves from the instant that he rises above the lunar horizon4 ,dawn1 as we have it on earth1 can have no counterpart upon the moon4 ,no atmosphere is there to reflect the solar beams while the luminary is yet out of actual sight1 and only the glimmer of the zodiacal light heralds the approach of day4 ,from the black horizon the sun suddenly darts his bright untempered beams upon the mountain tops1 crowning them with dazzling brilliance while their flanks and valleys are yet in utter darkness4 ,there is no blending of the night into day4 ,and yet there is a growth of illumination that in its early stages may be called a twilight1 and which is caused by the slow rise of the sun4 ,upon the earth1 in central latitudes1 the average time occupied by the sun in rising1 from the first glint of his upper edge till the whole disc is in sight1 is but two minutes and a quarter4 ,upon the moon1 however1 this time is extended to a few minutes short of an hour1 and1 therefore1 during the first few minutes a dim light will be shed by the small visible chord of the solar disc1 and this will give a proportionately modified degree of illumination upon the prominent portion of the landscape1 and impart to it something of the weird aspect which so strikes an observer of a total solar eclipse on earth when the scene is lit by the thin crescent of the re-appearing sun4 ,this impaired illumination constitutes the only dawn that a lunar spectator could behold4 ,and it must be of short duration2 for when1 in the course of half an hour1 the solar disc has risen half into view the lighting would no doubt appear nearly as bright to the eye as when the entire disc of the sun is above the horizon4 ,in this lunar sunrise1 however1 there is none of that gilding and glowing which makes the phenomenon on earth so gorgeous4 ,those crimson sky-tints with which we are familiar are due to the absorption of certain of the polychromous rays of light by our atmosphere4 ,the blue and violet components of the solar beams are intercepted by our envelope of vapour1 and only the red portions are free to pass2 while on the moon1 as there is no atmosphere1 this selective absorption does not occur4 ,if it did1 an observer gazing from the earth upon the regions of the moon upon which the sun is just rising would see the surface tinted with rosy light4 ,this1 however1 is not the case2 the faintest lunar features just catching the sun are seen simply under white light diluted to a low degree of brightness4 ,only upon rare occasions is the lunar scenery suffused with coloured illumination1 and these are when1 as we shall presently have to describe1 the solar rays reach the moon after traversing the earth's atmosphere during an eclipse of the sun4 ,this atmosphere of ours is the most influential element in beautifying our terrestrial scenery1 and the absence of such an appendage from the moon is the great modifying cause that affects lunar scenery as compared with that of the earth4 ,we are accustomed to the sun with its dazzling brightness--overpowering though it be--subdued and softened by our vaporous screen4 ,upon the moon there is no such modification4 ,the sun's intrinsic brilliancy is undiminished1 its apparent distance is shortened1 and it gleams out in fierce splendour only to be realised1 and then imperfectly1 by the conception of a gigantic electric light a few feet from the eye4 ,and the brightness is rendered the more striking by the blackness of the surrounding sky4 ,since there is no atmosphere there can be no sky-light1 for there is nothing above the lunar world to diffuse the solar beams2 not a trace of that moisture which even in our tropical skies scatters some of the sun's light and gives a certain degree of opacity or blueness1 deep though it be1 to the heavens by day4 ,upon the moon1 with no light-diffusing vapour1 the sky must be as dark or even darker than that with which we are familiar upon the finest of moonless nights4 ,and this blackness prevails in the full blaze of the lunar noon-day sun4 ,if the eye 7upon the moon7 could bear to gaze upon the solar orb 7which would be less possible than upon earth7 or could it be screened from the direct beams1 as doubtless it could by intervening objects1 it would perceive the nebulous and other appendages which we know as the corona1 the zodiacal light1 and the red solar protuberances3 or if these appendages could not be viewed with the sun above the horizon they would certainly be seen in glorious perfection when the luminary was about to rise or immediately after it had set4 ,and1 notwithstanding the sun's presence1 the planets and stars would be seen to shine more brilliantly than we see them on the clearest of nights2 the constellations would have the same configurations1 though they would be differently situated with respect to the celestial pole about which they would appear to turn1 for the axis of rotation of the moon is directed towards a point in the constellation ,draco4 ,the stars would never twinkle or change colour as they appear to us to do1 for scintillation or twinkling is a phenomenon of atmospheric origin1 and they would retain their full brightness1 down even to the horizon1 since there would be no haze to diminish their light4 ,the planets1 and the brighter stars at least1 would be seen even when they were situated very near to the sun4 ,the planet ,mercury1 so seldom detected by terrestrial gazers1 would be almost constantly in view during the lunar day1 manifesting his close attendance on the central luminary by making only short excursions of about two 7lunar7 days' length1 first on one side and then on the other4 ,venus would be nearly as continuously visible1 though her wanderings would be more extensive on either side4 ,the zodiacal light also1 which in our ,english latitude and climate is but rarely seen and in more favourable climes appears only when the sun itself is hidden beneath the horizon1 would upon the moon be seen as a constant accompaniment to the luminary throughout his daily course across the lunar sky4 ,the other planets would appear generally as they do to us on earth1 but1 never being lost in daylight1 their courses among the stars could be traced with scarcely any interruption4 ,one planet1 however1 that adorns the sky of the lunar hemisphere which is turned towards us deserves special mention from the conspicuous and highly interesting appearance it must present4 ,we allude to the earth4 ,to nearly one-half of the moon 7that which we never see7 this imposing object can never be visible2 but to the half that faces us the terrestrial planet must appear almost fixed in the sky4 ,a lunar spectator in 7what is to us7 the centre of the disc1 or about the region north of the lunar mountains ,ptolemy and ,hipparchus1 would have the earth in his zenith4 ,from regions upon the moon a little out of what is to us the centre1 a spectator would see the earth a little declining from the zenith1 and this declination would increase as the regions corresponding to the 7to us7 apparent edge of the moon were approached1 till at the actual edge it would be seen only upon the horizon4 ,from the phenomena of libration 7explained in ,chap4 ,,vi47 the earth would appear from nearly all parts of the lunar hemisphere to which it is visible at all to describe a small circle in the sky4 ,to an observer1 however1 upon the 7to us7 marginal regions of the lunar globe1 it would appear only during a portion of the lunar day--being visible in fact only in that part of its small circular path which happened to lie above the observer's horizon3 in some regions only a portion of the terrestrial disc would make its brief appearance4 ,from the lunar hemisphere beyond this marginal line the earth can never be seen at all4 ,the lunar spectator whose situation enabled him to view the earth would see it as a moon2 and a glorious moon indeed it must be4 ,its diameter would be four times as great as that of the moon itself as seen by us1 and the area of its full disc #ac times as great4 ,it would be seen to pass through its phases1 just as does our satellite1 once in a lunar day or a terrestrial month1 and during that cycle of phases1 since #bi of our days would be occupied by it1 the axial rotation would bring all the features of its surface configuration into view so many times in succession4 ,but the greatest beauty of this noble moon would be seen during the lunar night1 in considering which we shall again allude to it2 for when it is full-moon to the earth it is new-earth to the moon4 ,at lunar midnight this globe of ours is fully illuminated2 as morning nears1 the earth-moon wanes1 its disc slowly passing through the gibbous phases until at sunrise it would be just half-illuminated4 ,during the long forenoon it assumes a crescent which narrows and narrows till at midday the sun is in line with the earth and the latter is invisible1 save perhaps by a thin line of light marking its upper or lower edge1 accordingly as the sun is apparently above or below it4 ,in the lunar afternoon an illuminated crescent appears upon the opposite side of the terrestrial globe1 and this widens and widens till it becomes a half disc by lunar sunset and a full disc by lunar midnight4 ,the sun in his daily course passes at various distances1 sometimes above and sometimes below1 the nearly stationary earth4 ,obviously it will at times pass actually behind it1 and then the lunar spectator would behold the sublime spectacle of a total solar eclipse1 and that under circumstances which render the phenomenon far more imposing than its counterpart can appear from the earth2 for whereas1 when we see the moon eclipse the sun1 the nearly similar 7apparent7 diameters of the two bodies renders the duration of totality extremely short--at most #g minutes--a lunar spectator1 the earth appearing to him four times the diameter of the sun1 and he and the earth being relatively stationary1 would enjoy a view of the totality extending over several hours4 ,during the passage of the solar disc behind that of the earth1 a beautiful succession of luminous phenomena would be observed to follow from the refractions and dispersions which the sunbeams would suffer in passing tangentially through those parts of our atmospheric envelope which lie in their course2 those1 for instance1 on the margin of the earth1 as seen from the moon4 ,as the sun passed behind the earth1 the latter would be encircled upon the in-going side with a beautiful line of golden light1 deepening in places to glowing crimson1 due to the absorption1 already spoken of1 of all but the red and orange rays of the sun's light by the vapours of our atmosphere4 ,as the eclipse proceeded and totality came on1 this ruddy glow would extend itself nearly1 if not all1 around the black earth1 and so bright would it be1 that the whole lunar landscape covered by the earth's shadow would be illuminated with faint crimson light1#ah save1 perhaps1 in some parts of the far distance1 upon which the earth had not yet cast its shadow1 or off which the shadow had passed4 ,although the crimson light would preponderate1 it would not appear bright and red alike all around the earth's periphery4 ,the circle of light would be1 in fact1 the ring of twilight round our globe1 and it would only appear red in those places where the atmosphere chanced to be in that condition favourable for producing what on earth we know as red sunset and sunrise4 ,we know that the sun1 even in clear sky1 does not always set and rise with the beautiful red glow1 which may be determined by merely local causes1 and will therefore vary in different parts of the earth4 ,now a lunar spectator watching the sun eclipsed by the earth1 would see1 during totality and at a coup d'il1 every point around our world upon which the sun is setting on one side and rising upon the other4 ,to every part of the earth around what is then the margin1 as seen from the moon1 the sun is upon the horizon1 shining through a great thickness of atmosphere1 reddening it1 and being reddened by it wherever the vaporous conditions conduce to that colouration4 ,and at all parts where these conditions obtain1 the lunar eclipse-observer would see the ring of light around the black earth-globe brilliantly crimsoned2 at other parts it would have other shades of red and yellow1 and the whole effect would be to make the grand earth-ball1 hanging in the lunar sky1 like a dark sphere in a circle of glittering gold and rubies4 ,during the early stages of the eclipse1 this chaplet of brilliant-coloured lights would be brightest upon the side of the disappearing sun2 at the time of central eclipse the radiance 7supposing the sun to pass centrally behind the earth7 would be equally distributed1 and during the later stages it would preponderate upon the side of the reappearing sun4 ,we have endeavoured to give a pictorial realization of this phenomenon and of the effect of the eclipse upon the lunar landscape1 but such a picture cannot but fall very1 very far short of the reality4 7,see ,plate ,,xxii47 ,and now for a time let us turn attention from the lunar sky to the scenery of the lunar landscape4 ,let us1 in imagination1 take our stand high upon the eastern side of the rampart of one of the great craters4 ,height1 it must be remarked1 is more essential on the moon to command extent of view than upon the earth1 for on account of the comparative smallness of the lunar sphere the dip of the horizon is very rapid4 ,such height1 however1 would be attained without great exercise of muscular power1 since equal amounts of climbing energy would1 from the smallness of lunar gravity1 take a man six times as high on the moon as on the earth4 ,let us choose1 for instance1 the hill-side of ,copernicus4 ,the day begins by a sudden transition4 ,the faint looming of objects under the united illumination of the half-full earth and the zodiacal light is the lunar precursor of day-break4 ,suddenly the highest mountain peaks receive the direct rays of a portion of the sun's disc as it emerges from below the horizon4 ,the brilliant lighting of these summits serves but to increase1 by contrast1 the prevailing darkness1 for they seem to float like islands of light in a sea of gloom4 ,at a rate of motion twenty-eight times slower than we are accustomed to1 the light tardily creeps down the mountain-sides1 and in the course of about twelve hours the whole of the circular rampart of the great crater below us1 and towards the east1 shines out in brilliant light1 unsoftened by a trace of mountain-mist4 ,but on the opposite side1 looking into the crater1 nothing but blackness is to be seen4 ,as hour succeeds hour1 the sunbeams reach peak after peak of the circular rampart in slow succession1 till at length the circle is complete and the vast crater-rim1 #ej miles in diameter1 glistens like a silver-margined abyss of darkness4 ,by-and-by1 in the centre1 appears a group of bright peaks or bosses4 ,these are the now illuminated summits of the central cones1 and the development of the great mountain cluster they form henceforth becomes an imposing feature of the scene4 ,from our high standpoint1 and looking backwards to the sunny side of our cosmorama1 we glance over a vast region of the wildest volcanic desolation4 ,craters from five miles diameter downwards crowd together in countless numbers1 so that the surface1 as far as the eye can reach1 looks veritably frothed over with them4 ,nearer the base of the rampart on which we stand1 extensive mountain chains run to north and to south1 casting long shadows towards us2 and away to southward run several great chasms a mile wide and of appalling blackness and depth4 ,nearer still1 almost beneath us1 crag rises on crag and precipice upon precipice1 mingled with craters and yawning pits1 towering pinnacles of rock and piles of scoria and volcanic dbris4 ,but we behold no sign of existing or vestige of past organic life4 ,no heaths or mosses soften the sharp edges and hard surfaces3 no tints of cryptogamous or lichenous vegetation give a complexion of life to the hard fire-worn countenance of the scene4 ,the whole landscape1 as far as the eye can reach1 is a realization of a fearful dream of desolation and lifelessness--not a dream of death1 for that implies evidence of preexisting life1 but a vision of a world upon which the light of life has never dawned4 ,illustration3 ,,plate ,,xxii4 ,,aspect ,,of ,,an ,,eclipse ,,of ,,the ,,sun ,,by ,,the ,,earth1 ,,as ,,it ,,would ,,appear ,,as ,,seen ,,from ,,the ,,moon4 ,looking again1 after some hours' interval1 into the great crateral amphitheatre1 we see that the rays of the morning sun have crept down the distant side of the rampart1 opposite to that on which we stand1 and lighted up its vast landslipped terraces into a series of seeming hill-circles with all the rude and rugged features of a terrestrial mountain view1 and none of the beauties save those of desolate grandeur4 ,the plateau of the crater is half in shadow #aj1jjj feet below1 with its grand group of cones1 now fully in sight1 rising from its centre4 ,although these last are twenty miles away and the base of the opposite rampart fully double that distance1 we have no means of judging their remoteness1 for in the absence of an atmosphere there can be no arial perspective1 and distant objects appear as brilliant and distinct as those which are close to the observer4 ,not the brightness only1 but the various colours also of the distant objects are preserved in their full intensity2 for colour we may fairly assume there must be4 ,mineral chlorates and sublimates will give vivid tints to certain parts of the landscape surface1 and there must be all the more sombre colours which are common to mineral matters that have been subjected to fiery influence4 ,all these tints will shine and glow with their greater or less intrinsic lustres1 since they have not been deteriorated by atmospheric agencies1 and far and near they will appear clear alike1 since there is no arial medium to veil them or tarnish their pristine brightness4 ,in the lunar landscape1 in the line of sight1 there are no means of estimating distances2 only from an eminence1 where the intervening ground can be seen1 is it possible to realize magnitude in a lunar cosmorama and comprehend the dimensions of the objects it includes4 ,and with no air there can be no diffusion of light4 ,as a consequence1 no illumination reaches those parts of the scene which do not receive the direct solar rays1 save the feeble amount reflected from contiguous illuminated objects1 and a small quantity shed by the crescent earth4 ,the shadows have an awful blackness4 ,as we stand upon our chosen point of observation1 we see on the lighted side of the rampart almost dazzling brightness1 while beneath us1 on the side away from the sun1 there is a region many miles in area impenetrable to the sight1 for there is no object within it receiving sufficient light to render it discernible2 and all around us1 far and near1 there is the violent contrast between intense brightness of insolated parts and deep gloom of those in equally intense shadow4 ,the black though starlit sky helps the violence of this contrast1 for the bright mountains in the distance around us stand forth upon a background formed by the darkness of interplanetary space4 ,the visible effects of these conditions must be in every sense unearthly and truly terrible4 ,the hard1 harsh glowing light and pitchy shadows2 the absence of all the conditions that give tenderness to an earthly landscape2 the black noonday sky1 with the glaring sun ghastly in its brightness2 the entire absence of vestiges of any life save that of the long since expired volcanoes--all these conspire to make up a scene of dreary1 desolate grandeur that is scarcely conceivable by an earthly habitant1 and that the description we have attempted but insufficiently pourtrays4 ,a legitimate extension of the imagination leads us to impressions of lunar conditions upon other senses than that of sight1 to which we have hitherto confined our fancy4 ,we are met at the outset with a difficulty in this extension2 for it is impossible to conceive the sensations which the absence of an atmosphere would produce upon the most important of our bodily functions4 ,if we would attempt the task we must conjure up feelings of suffocation1 of which the thoughts are1 however1 too horrible to be dwelt upon2 we must therefore maintain the delusion that we can exist without air1 and attempt to realize some of the less discomforting effects of the absence of this medium4 ,most notable among these are the untempered heat of the direct solar rays1 and the influence thereof upon the surface material upon which we suppose ourselves to stand4 ,during a period of over three hundred hours the sun pours down his beams with unmitigated ferocity upon a soil never sheltered by a cloud or cooled by a shower1 till that soil is heated1 as we have shown1 to a temperature equal nearly to that of melting lead2 and this scorching influence is felt by everything upon which the sun shines on the lunar globe4 ,but while regions directly insolated are thus heated1 those parts turned from the sun would remain intensely cold1 and that scorching in sunshine and freezing in shade with which mountaineers on the earth are familiar would be experienced in a terribly exaggerated degree4 ,among the consequences1 already alluded to1 of the alternations of temperature to which the moon's crust is thus exposed1 are doubtless more or less considerable expansions and contractions of the surface material1 and we may conceive that a cracking and crumbling of the more brittle constituents would ensue1 together with a grating of contiguous but disconnected masses1 and an occasional dislocation of them4 ,we refer again to these phenomena to remark that if an atmospheric medium existed they would be attended with noisy manifestations4 ,there are abundant causes for grating and crackling sounds1 and such are the only sources of noise upon the moon1 where there is no life to raise a hum1 no wind to murmur1 no ocean to boom and foam1 and no brook to plash4 ,yet even these crust-cracking commotions1 though they might be felt by the vibrations of the ground1 would not manifest themselves audibly1 for without air there can be no communication between the grating or cracking body and the nerves of hearing4 ,dead silence reigns on the moon3 a thousand cannons might be fired and a thousand drums beaten upon that airless world1 but no sound could come from them3 lips might quiver and tongues essay to speak1 but no action of theirs could break the utter silence of the lunar scene4 ,at a rate twenty-eight times slower than upon earth1 the shadows shorten till the sun attains his meridian height1 and then1 from the tropical region upon which we have in imagination stood1 nothing is to be seen on any side1 save towards the black sky1 but dazzling light4 ,the relief of afternoon shadow comes but tardily1 and the darkness drags its slow length along the valleys and creeps sluggishly up the mountain-sides till1 in a hundred hours or more1 the time of sunset approaches4 ,this phenomenon is but daybreak reversed1 and is unaccompanied by any of the gorgeous sky tints that make the kindred event so enrapturing on earth4 ,the sun declines towards the dark horizon without losing one jot of its brilliancy1 and darts the full intensity of its heat upon all it shines on to the last4 ,its disc touches the horizon1 and in half an hour dips half-way beneath it1 its intrinsic brightness and colour remaining unchanged4 ,the brief interval of twilight occurs1 as in the morning1 when only a small chord of the disc is visible1 and the long shadows now sharpen as the area of light that casts them decreases4 ,for a while the zodiacal light vies with the earth-moon high in the heavens in illuminating the scene2 but in a few hours this solar appendage passes out of view1 and our world becomes the queen of the lunar night4 ,at this sunset time the earth1 nearly in the zenith of us1 will be at its half-illuminated phase1 and even then it will shed more light than we receive upon the brightest of moonlight nights4 ,as the night proceeds1 the earth-phase will increase through the gibbous stages until at midnight it will be 8full10 and our orb will be seen in its entire beauty4 ,it will perform at least one of its twenty-four-hourly rotations during the time that it appears quite full1 and the whole of its surface features will in that time pass before the lunar spectator's eye4 ,at times the northern pole will be turned towards our view1 at times the southern2 and its polar ice-caps will appear as bright white spots1 marking its axis of rotation4 ,if our lunar sojourn were prolonged we should observe the northern ice-cap creep downwards to lower latitudes 7during our winter7 and retreat again 7during our summer72 and this variation would be perceptible in a less degree at the southern pole1 on account of the watery area surrounding it4 ,the seas would appear 7so far as can be inferred7 of pale blue-green tint2 the continents parti-coloured3 and the tinted spots would vary with the changing terrestrial seasons1 as these are indicated by the positions and magnitudes of the polar ice-caps4 ,the permanent markings would be ever undergoing apparent modification by the variations of the white cloud-belts that encircle the terrestrial sphere4 ,of the nature of these variations meteorological science is not as yet in a position to speak3 it would indeed be vastly to the benefit of that science if a view of the distribution of clouds and vapours over the earth's surface1 as comprehensive as that we are imagining1 could really be obtained4 ,it might happen at 8full-earth10 that a black spot with a fainter penumbral fringe would appear on one side of the illuminated disc and pass somewhat rapidly across it4 ,this would occur when the moon passed exactly between the sun and the earth1 and the shadow of the moon was cast upon the terrestrial disc4 ,we need hardly say that these shadow-transits would occur upon those astronomically important occasions when an eclipse of the sun is beheld from the earth4 ,the other features of the sky during the long lunar night would not differ greatly from those to which we alluded in speaking of its day aspects4 ,the stars would be the more brightly visible1 from the greater power of the eye-pupil to open in the absence of the glaring sun1 and on this account the milky-way would be very conspicuous and the brighter nebul would come into view4 ,the constellations would mark the night by their positions1 or the hours might be told off 7in periods of twenty-four each7 by the successive reappearances of surface features on certain parts of the terrestrial disc4 ,the planets in opposition to the sun would now be seen1 and a comet might appear to vary the monotony of the long lunar night4 ,but a meteor would never flash across the sky1 though dark meteoric particles and masses would continually bombard the lunar surface1 sometimes singly1 sometimes in showers4 ,and these would fall with a compound force due to their initial velocity added to that of the moon's attraction4 ,as there is no atmosphere to consume the meteors by frictional heat or break by its resistance the velocity of their descent1 they must strike the moon with a force to which that of a cannon-ball striking a target is feeble indeed4 ,a position on the moon would be an unenviable stand-point from this cause alone4 ,the lunar landscape by night needs little description3 it would be lit by the earth-moon sufficiently to allow salient features1 even at a distance1 to be easily made out1 for its moon 7i4e4 the earth7 has thirteen times the light-reflecting area that our's has4 ,but the night illumination will change in intensity1 since the earth-moon varies from half-full to full1 and again to half-full1 between sunset and the next sunrise4 ,the direction of the light1 and hence the positions of the shadows1 will scarcely alter on account of the apparent fixity of the earth in the lunar sky4 ,a slight degree of warmth might possibly be felt with the reflected earth-light2 but it would be insufficient to mollify the intensity of the prevailing cold4 ,the heat accumulated by the ground during the three hundred hours' sunshine radiates rapidly into space1 there being no atmospheric coat to retain it1 and a cooling process ensues that goes on till1 all warmth having rapidly departed1 the previously parched soil assumes a temperature approaching that of celestial space itself1 and which has been1 as we have stated1 estimated at about #bjj below the ,fahrenheit zero4 ,if moisture existed upon the moon1 its night-side would be bound in a grip of frost to which our ,arctic regions would be comparatively tropical4 ,but since there is no water1 the aspect of the lunar scenery remains unmodified by effects of changing temperature4 ,such1 then1 are the most prominent effects that would manifest themselves to the visual and other senses of a being transported to the moon4 ,the picture is not on the whole a pleasant one1 but it is instructive2 and our rendering of it1 imperfect though it be1 may serve to suggest other inferences that cannot but add to the interest which always attaches to the contemplation of natural scenes and phenomena from points of view different from those which we ordinarily occupy4 ,illustration3 ,,plate ,,xxiii4 ,,group of ,,lunar ,,mountains4 ideal lunar landscape4 ,,chapter ,,xiv4 ,,the ,,moon ,,as ,a ,,satellite3 ,,its ,,relation ,,to ,,the ,,earth ,,and ,,man4 ,apart from the recondite functions of the moon considered as one of the interdependent members of the solar family1 into which it would be beyond our purpose to inquire1 there are certain means by which it subserves human interests and ministers to the wants of civilized man to which we deem it desirable to call attention1 especially as some of them are not so self-apparent as to have attracted popular attention4 ,the most generally appreciated because the most evident of the uses of the moon is that of a luminary4 ,popular regard for it is usually confined to its service in that character1 and in that character poets and painters have never tired in their efforts to glorify it4 ,and obviously this service as a 8lesser light0 is sufficiently prominent to excite our warmest admiration4 ,but moonlight is1 from the very conditions of its production1 of such a changeable and fugitive nature1 and it affords after all so partial and imperfect an alleviation of night's darkness1 that we are fain to regard the light-giving office of the moon as one of secondary importance4 ,far more valuable to mankind in general1 so estimable as to lead us to place it foremost in our category of lunar offices1 is the duty which the moon performs in the character of a sanitary agent4 ,we can conceive no direful consequences that would follow from a withdrawal of the moon's mere light2 but it is easy to imagine what highly dangerous results would ensue if the moon ceased to produce the tides of the ocean4 ,motion and activity in the elements of the terraqueous globe appear to be among the prime conditions in creation4 ,rest and stagnation are fraught with mischief4 ,while the sun keeps the atmosphere in constant and healthy circulation through the agency of the winds1 the moon performs an analogous service to the waters of the sea and the rivers that flow into them4 ,it is as the chief producer of the tides--for we must not forget that the sun exercises its tidal influences1 though in much lesser degree--that we ought to place the highest value on the services of the moon3 but for its aid as a mighty scavenger1 our shores1 where rivers terminate1 would become stagnant deltas of fatal corruption4 ,twice 7to speak generally7 a day1 however1 the organic matter which rivers deposit in a decomposing state at their embouchures is swept away by the tidal wave2 and thus1 thanks to the moon1 a source of direful pestilence is prevented from arising4 ,rivers themselves are providentially cleansed by the same means1 where they are polluted by bordering towns and cities which1 from the nature of things1 are sure to arise on river banks2 and it seems to be also in the nature of things that the river traversing a city must become its main sewer4 ,the foul additions may be carried down by the stream in its natural course towards the ocean1 but where the river is large there will be a decrease in velocity of the current near the mouth or where it joins the sea1 thus causing partial stagnation and consequent deposition of the deleterient matters4 ,all this1 however1 is removed1 and its inconceivable evils are averted by our mighty and ever active 8sanitary commissioner10 the moon4 ,we can scarcely doubt that a healthy influence of less obvious degree is exerted in the wide ocean itself2 but1 considering merely human interests1 we cannot suppress the conviction that man is more widely and immediately benefited by this purifying office of the moon than by any other4 ,but the sanitary service is not the only one that the moon performs through the agency of the tides4 ,there is the work of tidal transport to be considered4 ,upon tidal rivers and on certain coasts1 notwithstanding wind and the use of steam1 a very large proportion of the heavy merchandize is transported by that slow but powerful 8tug0 the flood-tide2 and a similar service1 for which1 however1 the moon is not to be entirely credited1 is done by the down-flow of the ebb-tide4 ,large ships and heavily-laden rafts and barges are quietly taken in tow by this unobtrusive prime mover1 and moved from the river's mouth to the far-up city1 and from wharf to wharf along its banks2 and a vast amount of mechanical work is thus gratuitously performed which1 if it had to be provided by artificial means1 would represent an amount of money value which for such a city as ,london would have to be counted by thousands1 possibly millions1 of pounds yearly4 ,for this service we owe the moon the gratitude that we ought to feel for a direct pecuniary benefactor4 ,in the existing state of civilization and prosperity1 we do not1 however1 utilize the power of the tides nearly to the extent of their capabilities4 ,our coal mines1 rich with 8the light of other days0--for coal was long ago declared by ,stevenson to be 8bottled sunshine0--at present furnish us with so abundant a supply of power-generating material that in our eagerness to use it upon all possible occasions we are losing sight1 or putting out of mind1 many other valuable prime movers1 and amongst them that of the rise and fall of the waters1 which can be immediately converted into any form of mechanical power by the aid of tide-mills4 ,such mills may be found in existence here and there1 but for the present they are generally out-rivalled by the steam-engine with all its conveniences and adaptabilities2 and hence they have not shared the benefits of that inventive ingenuity which has achieved such wonders of mechanical appliance while steam has been in the ascendant4 ,but it must be remembered that in our extravagant use of coal we are drawing from a bank into which nothing is being paid4 ,we are consuming an exhaustive store1 and the time must come when it will be needful to look around in quest of 8powers that may be40 ,then an impetus may be given to the application of the tides to mechanical purposes as a prime mover4#ai ,for the people of the ,british ,islands the problem would have an especial importance1 viewing the extent of our seaboard and the number of our tidal rivers4 ,the source of motion that offers itself is of almost incalculable extent4 ,there is not merely the onward flowing motion of streams to be utilized1 but also the lift of water1 which1 if small in extent1 is stupendous in amount2 and within certain limits it matters little to the mechanician whether the 8foot-pounds0 of work placed at his disposal are in the form of a great mass lifted to a small height or a small mass lifted to a great height4 ,there is no reason either why the utilization of the tides should be confined to rivers4 ,the sea-side might well become the circle of manufacturing industry1 and the millions of tons of water lifted several feet twice daily on our shores might be converted1 even by schemes already proposed1 to furnish the prime movement of thousands of factories4 ,and we must not forget how completely modern science has demonstrated the inter-convertibility of all kinds of force1 and thus opened the way for the introduction of systems of transporting power that1 in such a state of things as we are for the moment considering1 might be of immense benefit4 ,gravity1 for instance1 can be converted into electricity2 and electricity gives us that wonderful power of transmitting force without transmitting 7or even moving7 matter1 which power we use in the telegraph1 where we generate a force at one end of a wire and use it to ring bells or deflect needles at the other end1 which may be thousands of miles away4 ,what we do with the slight amount of force needful for telegraphy is capable of being done with any greater amount4 ,a tide-mill might convert its mechanical energy by an electro-magnetic engine1 and in the form of electricity its force could be conveyed inland by proper wires and there reconverted back to mechanical or moving power4 ,true1 there would be a considerable loss of power1 but that power would cost nothing for its first production4 ,another means ready to hand for transporting power is by compressed air1 which has already done good service2 another is the system so admirably worked out by ,sir ,w4 ,armstrong1 of transmitting water-power through the agency of an 8accumulator10 now so generally used at our ,docks and elsewhere1 for working cranes and such other uses4 ,and as the whole duty of the engineer is to convert the forces of nature1 there is a rich field open for his invention1 and upon which he may one day have to enter1 in adapting the pulling force of the moon to his fellow man's mechanical wants through the intermediation of the tides4 ,another of the high functions of the moon is that by which she subserves the wants of the navigator1 and enables him to track his course over the pathless ocean4 ,of the two co-ordinates1 ,latitude and ,longitude1 that are needful to determine the position of a ship at sea 7or of any standpoint upon the earth's surface7 the first is easily found1 inasmuch as it is always equal to the altitude of the celestial pole at the place of observation4 ,but the determination of the longitude has always been a difficult problem1 and one upon which a vast amount of ingenuity has been expended4 ,when it was first attacked it was soon discovered that the moon was the object of all others by which it could be most accurately and1 all things considered1 most readily determined4 ,we must premise that the longitude of one place from another is in effect the difference between the local times at the two places1 so that when we say that a place or a ship is1 for instance1 seven hours1 twenty-four minutes1 ten seconds1 west of ,greenwich1 we mean that the time-o'-day at the place or ship is seven hours twenty-four minutes ten seconds earlier than that at ,greenwich4 ,hence1 finding the longitude at sea or at any place and moment means finding what time it is at ,greenwich at that moment4 ,of course this could be most easily done if we could set a timekeeper at ,greenwich and rely upon its keeping time during a long sea voyage2 and this plan appeared so feasible that our ,government long ago offered a prize of #bj1jjj for a timekeeper which would perform to a stated degree of accuracy after a certain sea voyage4 ,one ,john ,harrison did make such a timekeeper1 that actually satisfied the conditions1 and obtained the prize3 and chronometers are now largely used for longitude1 their construction having been brought to great perfection1 especially in ,england1 owing to a continuance 7in a less liberal degree1 however17 of ,government inducement4 ,but chronometers are not entirely to be relied on1 even where several are carried1 which in other than ,government ships is rarely the case3 recourse must be had to the heavenly bodies for check upon the timekeeper4 ,and the moon is1 as we have said1 the body that best serves the requirements of the problem4 ,the lunar method for longitude amounts practically to this4 ,the stars are fixed2 the sun1 moon1 and planets move amongst them2 the sun and planets with very slow rates of apparent motion1 the moon with a very rapid one4 ,if1 then1 it be predicted that at a certain instant of ,greenwich time the moon will be a certain distance from a fixed star1 and if the mariner at sea observes when the moon has that exact distance1 he will know the ,greenwich time at the instant of his observation4#bj ,the moon thus becomes to him as the hand of a timepiece1 whereof the stars are the hour and minute marks1 the whole being1 as it were1 set to ,greenwich time4 ,then if he knows 7which he does by other observations easily obtained7 the local time at his ship1 he can take the difference between the ,greenwich time and his time1 which difference is in fact his longitude from ,greenwich4 ,the requisite predictions of the distance of the moon from several fixed stars near her are given to the utmost exactness for every three hours of every day and night 7when the moon can possibly be seen7 in the navigator's vade mecum1 the 8,nautical ,almanac10 and from these given distances the navigator can1 by a simple process of differencing1 obtain the distance1 and hence the ,greenwich time1 for any intermediate instant at which he may chance to make his observation4 ,whenever he can see the moon he can obtain ,greenwich time4 ,of course the whole value of this method depends upon the exactitude of the predicted distances corresponding to the given ,greenwich times4 ,these distances are obtained by tables of the moon's motions1 which must be found from observations4 ,the motions in question are of an intricacy almost past comprehension1 on account of the disturbing forces to which the moon is subjected by the sun and planets4 ,the powers of the profoundest mathematicians1 from ,newton downwards1 have been severely exercised in efforts to group them into a theory1 and represent them by tables capable of furnishing the requisite exact predictions of lunar positions for nautical purposes4 ,accurate observations of the moon's place night after night have1 from the dawn of this lunar method for longitude1 been in urgent request by mathematicians for the purposes specified1 and it was solely to procure these observations that the ,observatory at ,greenwich was established1 and mainly for their continued prosecution 7and for the stellar observations necessary for their utilization7 that it is sustained4 ,for two centuries the moon has been unremittingly observed at ,greenwich1 and the tables at present used for making the 8,nautical ,almanac0 7those formed by ,prof4 ,hansen7 depend upon the observations there obtained4 ,the work still goes on1 for even now the degree of exactitude is not what is desired1 and astronomers are looking forward with some interest to new lunar tables which were left complete by the late ,m4 ,delaunay1 formerly the head of astronomy in ,france1 based upon a theory which he evolved4 ,this use of the moon is the grandest of all in respect of the results to which it has led4 ,then1 too1 regarding the moon as a timekeeper1 we must not forget the service that it renders in furnishing a division of time intermediate between the day--which is measured by the earth's rotation--and the year1 which is defined by the earth's orbital revolution4 ,notwithstanding the survival of lunar reckoning in our religious services1 we1 in our time and country1 scarcely need a moon to mark our months2 but we must not forget that with many ancient people the moon was1 and with some is still1 the chief timekeeper1 the calendars of such people being lunar ones1 and all their events being reckoned and dated by 8moons40 ,to us1 however1 the moon is of great service in this department by enabling us to fix dates to many historical events1 the times of occurrence of which are uncertain1 by reason of defective records or by dependence upon such uncertain data as 8lives of emperors10 years of this or that king's reign1 or generations of one or another family4 ,the moon now and then clears up a mystery1 or decides a disputed point in chronology1 by furnishing the accurate date of an ancient eclipse1 which was a phenomenon that always inspired awe and secured for itself careful record4 ,the chronologer is continually applying to the astronomer for the date and place of visibility of some total eclipse1 of which he has found an imperfect record1 veritable as to the fact1 but dated only by reference to some year of a so-and-so's reign1 or by some battle or other historical occurrence4 ,the eclipses that occurred near the time are then examined1 and when one is found that tallies with recorded conditions in other respects 7such as the time of day and the place of observation71 its indisputable date becomes a starting-point from which the chronologer works backwards and forwards in safety4 ,there is one famous eclipse--that predicted by ,thales six centuries before ,christ1 which put an end to the battle between the ,medes and ,lydians by the terror its darkness created in both armies--which is most intimately associated with ancient chronology1 and has been used to rectify a proximate date 7the first year of ,cyrus of ,babylon7 which forms the foundation of all ,scripture chronology4 ,sacred and profane history alike are continually receiving assistance from the accurate dates which the moon1 by having caused eclipses of the sun1 enables the astronomer to fix beyond cavil or doubt4 ,the mention of eclipses reminds us1 too1 of the use which the moon has been in increasing1 through them1 our knowledge of the physical condition of the sun4 ,if the moon had never intervened to cut off the blinding glare of the solar disc1 we should have been to this day left to assume that the sun is all-contained by the dazzling globe that we ordinarily see4 ,but1 thanks to the moon's intervention1 we now know that the sun is by no means the mere naked sphere we should have suspected4 ,eclipses have taught us that it is surrounded by an envelope of glowing gases1 and that it has a vast vaporous surrounding1 beyond its glowing atmosphere1 which appears to be composed of matter streaming away from the sun into surrounding space4 ,with these discoveries still in their infancy1 it is impossible to foresee the knowledge to which they will eventually lead1 but they can hardly be barren of fruit1 and whatever they ultimately teach will be so much insight gained into the sublimest problem that human science has before it--the determination of the source and maintaining power of the light and heat and vivifying agency of the sun4 ,in according our thankful reflections to the moon for these revelations1 we must not forget that1 should there be inhabitants upon our neighbouring worlds1 ,mercury1 ,venus1 and ,mars1 which have no satellites1 they1 the supposed inhabitants1 can gain no such knowledge upon the surroundings of the ruler of the solar system4 ,on the other hand1 any rational being who may be supposed to dwell upon ,saturn or ,jupiter1 would1 through the intervention of their numerous moons1 have1 in the latter case especially1 far more abundant opportunities of acquiring the knowledge in question than we have4 ,finally1 there is a use of the moon which touches us1 author and reader1 very closely4 ,it has taught us of a world in a condition totally different from our own2 of a planet without water1 without air1 without the essentials to life development1 but rather with the conditions for life destruction2 a planet left by the ,creator--for wise purposes that we cannot fully know--as it were but half-formed1 with all the igneous foundations fresh from the cosmical fire1 and with its rough-cast surface in its original state1 its fire and mould-marks exposed to our view4 ,from these we have essayed to resolve some of the processes of formation1 and thus to learn something of the cosmical agencies that are called forth in the purely igneous era of a planet's history4 ,we trust that we1 on our part1 have shown that the study of the moon may be a benefit not merely to the astronomer1 but to the geologist2 for we behold in it a mighty 8medal of creation0 doubtless formed of the same material and struck with the same die that moulded our earth2 but while the dust of countless ages and the action of powerful disintegrating and denuding elements have eroded and obliterated the earthly impression1 the superscriptions on the lunar surface have remained with their pristine clearness unsullied1 every vestige sharp and bright as when it left the ,almighty ,maker's hands4 ,the moon serves no second-rate or insignificant service when it teaches us of the variety of creative design in the worlds of our system1 and exalts our estimation of this peopled globe of ours by showing us that all the planetary worlds have not been deemed worthy to become the habitations of intelligent beings4 ,reflections upon the uses of the moon not unnaturally lead our thoughts to some matters that may be regarded as abuses4 ,these mainly take the form of superstitions1 erroneous beliefs in the moon's influence over terrestrial conditions1 and occasionally of erroneous ideas upon the moon's functions as a luminary4 ,the first-mentioned are almost beneath notice1 for they include such mythical suspicions as that the moon influences human sanity and other affections of mind and body2 that the moon's rays have a decomposing effect upon organic matter2 that they produce blindness by shining upon a sleeper's eyes2 that the moon determines the hours of human death1 which is supposed to occur with the change of the tide1 etc4 ,all such1 having no foundation on fact1 are put beyond our consideration4 ,the third matter we have mentioned may also be dismissed in a very few words4 ,the erroneous ideas upon the moon's functions as a luminary1 to which we allude1 are those which are manifested by poets and painters1 and even historians1 who do not hesitate to bring the moon upon a scene in any form and at any time they please without reference to actual lunar circumstances4 ,it is no uncommon thing to see1 in a picture representing an evening scene1 a moon introduced which can only be seen in the morning--a waning moon instead of a waxing one2 and astronomical critics have1 indeed1 caught artists so far tripping as to put a moon in a picture representing some event that occurred upon a date when the moon was new1 and therefore invisible4 ,writers take the same liberties very frequently4 ,a newspaper correspondent1 during the ,franco-,prussian war1 described the full moon as shining upon a scene of desolation on a particular night1 when really there was no moon to be seen4 ,one of the most flagrant cases of this kind1 however1 occurs in ,wolfe's ballad on 8,the death of ,sir ,john ,moore10 where it is written that the hero was buried 8,by the struggling moonbeam's misty light40 ,but the interment actually took place at a time when the moon was out of sight4 ,we mention these abuses of the moon in the hope of promoting a better observance of the moon's luminary office4 ,they who wish to bring the moon upon a scene1 not knowing ipso facto that it was there1 should first take the advice of ,nick ,bottom in the 8,midsummer ,night's ,dream10 and make sure of their object by consulting an almanac4 ,the second of the specified abuses to which the moon is subject refers to its supposed influence on the weather2 and in the extent to which it goes this is one of the most deeply rooted of popular errors4 ,that there is an infinitesimal influence exerted by the moon on our atmosphere will be seen from the evidence we have to offer1 but it is of a character and extent vastly different from what is commonly believed4 ,the popular error is shown in its most absurd form when the mere aspect of the moon1 the mere transition from one phase of illumination to another1 is asserted to be productive of a change of weather2 as if the gradual passage from first quarter to second quarter1 or from that to third1 could of itself upset an existing condition of the atmosphere2 or as if the conjunction of the moon with the sun could invert the order of the winds1 generate clouds1 and pour down rains4 ,a moment's reasoning ought to show that the supposed cause and the observed effect have no necessary connection4 ,in our climate the weather may be said to change at least every three days1 and the moon changes--to retain the popular term--every seven days2 so that the probability of a coincidence of these changes is very great indeed3 when it occurs1 the moon is sure to be credited with causing it4 ,but a theory of this kind is of no use unless it can be shown to apply in every case2 and1 moreover1 the change must always be in the same direction3 to suppose that the moon can turn a fine day to a wet one1 and a wet day to a fine morrow indiscriminately1 is to make our satellite blow hot and cold with the same mouth1 and so to reduce the supposition to an absurdity4 ,if any marked connection existed between the state of the air and the aspect of the moon1 it must inevitably have forced itself unsought upon the attention of meteorologists4 ,in the weekly return of ,births1 ,deaths1 and ,marriages1 issued by the ,registrar-,general1 a table is given1 showing all the meteorological elements at ,greenwich for every day of the year1 and a column is set apart for noting the changes and positions of the moon4 ,these reports extend backwards nearly a quarter of a century4 ,here1 then1 is a repertory of data that ought to reveal at a glance any such connection1 and would certainly have done so had it existed4 ,but no constant relation between the moon columns and those containing the instrument readings has ever been traced4 ,our meteorological observatories furnish continuous and unbroken records of atmospheric variations1 extending over long series of years3 these afford still more abundant means for testing the validity of the lunar hypothesis4 ,the collation has frequently been made for special points in the inquiry1 and certainly some connection has been found to obtain between certain positions of the moon in her orbit and certain instrumental averages2 but so small are the effects traceable to lunar influence1 that they are almost inappreciable among the grosser irregularities that arise from other and as yet unexplained causes4 ,the lunar influences upon our atmosphere most likely to be detected are those of a tidal character1 and those due to the radiation of the heat which the moon receives from the sun4 ,the first would be shown by the barometer1 which may be called an 8atmospheric tide gauge40 ,some years ago ,sir ,edward ,sabine instituted a series of observations at ,st4 ,helena1 to determine the variations of barometric indications from hour to hour of the lunar day4 ,the greatest differences were found to occur between the times when the moon was on the meridian1 and when it was six hours away from the meridian2 in other words1 between atmospheric high tide and low tide4 ,but the average of these differences amounted only to the four-hundredth part of an inch on the instrument's scale2 a quantity that no weather observer would heed1 that none but the best barometers would show1 and that can have no perceptible effect on weather changes4 ,the distance of the moon from the earth varies1 as is well known1 in consequence of the elliptical form of her orbit3 this variation ought also to produce an effect upon the instrument's indications2 but ,colonel ,sabine's analysis showed that it was next to insensible2 the mean reading at apogee differing from that at perigee by only the two-thousandth part of an inch4 ,schubler1 a ,german meteorologist1 had arrived at similarly negative results some years previously4 ,hence it appears that the great index of the weather is not sensibly affected by the state of the moon3 the conclusion to be drawn with regard to the weather itself is obvious enough4 ,as regards the heat received from the moon1 we know1 from the recent experiments of ,lord ,rosse in ,england1 and ,marie ,davy in ,france1 elsewhere alluded to1 that a degree of warmth appreciable to the highly sensitive thermopile is exerted by the moon upon the earth near to the time of full moon1 when the sun's rays have been pouring their unmitigated heat upon the lunar surface continuously for fourteen days4 ,and as it is improbable that the whole of the heat sent earthwards from the moon reaches the earth's surface1 we must infer that a considerable amount is absorbed in the higher atmosphere1 and does work in evaporating the lighter clouds and thinning the denser ones4 ,the effect of this upon the earth is to facilitate the radiation of its heat into space1 and so to cool the lower atmospheric strata4 ,and this effect has been shown to be a veritable one by an exhaustive tabulation of temperature records from various observatories1 which was undertaken by ,mr4 ,park ,harrison4 ,the general conclusion from these was1 that the temperature at the earth's surface is lower by about #b degrees at moon's last quarter than at first quarter2 the paradoxical result being what would naturally follow from the foregoing consideration4 ,the tendency of the full moon to clear the sky has been remarked by several distinguished authorities1 to wit1 ,sir ,john ,herschel1 ,humboldt1 and ,arago2 and in general the clearing may be accepted as a meteorological fact1 though in one case of close examination it has been negatived4 ,it cannot be doubted that a full moon sometimes shows a night to be clear that would in the absence of the moon be called cloudy4 ,when close comparisons are made between the moon's positions and records of rain-fall and wind-direction1 dim indications of relation exhibit themselves1 which may be the feeble consequences of the change of temperature just spoken of2 but in every case where an effect has been traced it has been of the most insignificant kind1 and no apparent connexion has been recognized between one effect and another4 ,certainly there is nothing that can support the extensive popular belief in lunar influence on weather1 and nothing that can modify the conviction that this belief as at present maintained is an absurd delusion4 ,yet its acceptance is so general1 and runs through such varied grades of society1 that we have felt it our duty to dwell upon it to the extent that we have done4 ,,chapter ,,xv4 ,,concluding ,,summary4 ,having arrived at the conclusion of our subject1 it appears to us desirable that we should recall to the reader1 by a rapid review1 its salient features4 ,our main object being to attempt what we conceived to be a rational explanation of the surface details of the moon which should be in accordance with the generally received theory of planetary formation1 and with the peculiar physical conditions of the lunar globe--the opening of our work was a summary of the nebular hypothesis as it was started by the first ,herschel and systemised by ,laplace4 ,following these philosophers we endeavoured to show how a chaotic mass of primordial matter existing in space would1 under the action of gravitation1 become transformed into a system of planetary bodies circulating about a common centre of gravity2 and further1 how1 in some cases1 the circulating planetary masses would themselves become sub-centres of satellitic systems2 our earth being one of these sub-centres with only one satellitic attendant--to wit1 the moon1 the subject of our study4 ,the moon being thus considered as evolved from the parent nebulous mass1 and existing as an isolated and compact body1 we had next to consider what was the effect of the continued action of the gravitating force4 ,by the light of the beautiful 8mechanical theory of heat0 we argued that this force1 not being destructible1 but being convertible1 was turned into heat2 and that whatever may have been the original condition of the parent nebulous mass1 as regards temperature1 its planetary offspring became elevated to an intense degree of heat as they assumed the form of spheres under the influence of gravitation4 ,the incandescent sphere having attained its maximum degree of heat by the total conversion thereinto of the gravitating force it embodied1 we explained how there must have ensued a dispersion of that heat by radiation into surrounding space1 resulting in the cooling and consequent solidification of the outermost stratum of the lunar sphere1 and subsequently in the continuation of the cooling process downwards or inwards to the centre4 ,and here we essayed to prove that in this second stage of the cooling process1 when the crust was solid and the subjacent portion of the molten sphere was about to solidify1 there would come into operation a principle which appears to govern the behaviour of certain fusible substances1 and which may be concisely termed the principle of pre-solidifying expansion4 ,we adduced several examples of the manifestation of this principle1 soliciting for it the careful consideration of physicists and geologists1 and looking to it as furnishing the key to the mystery of volcanic action upon the moon1 since1 without needing recourse to aqueous or gaseous sources of eruptive power1 it afforded a rationale of the ejection of the fluid and semifluid matter of the moon through the solidified crust thereof1 and also of the dislocations of that crust1 unattended by actual ejection of subsurface matter1 of which our satellite presents a variety of examples1 and which the earth also appears to have experienced at some period of its formative history4 ,arrived at this stage of our subject we thought it needful to introduce some pages of data and descriptive detail4 ,accordingly in one chapter we discussed the form1 magnitude1 weight1 and density of the moon1 and the force of gravity at its surface3 and the more soundly to fix these data in the mind1 we devoted a few lines to explanation of the methods whereby each has been ascertained4 ,we then examined the question 7so important to our subject7 of the existence or non-existence of a lunar atmosphere1 giving the evidence1 which may be regarded as conclusive1 in proof of the absence of both air and water from the moon1 and1 therefore1 refuting the claim of these elements to be considered as sources or influants of the moon's volcanic manifestations4 ,a general coup-d'il of the lunar hemisphere facing the earth next engaged our attention1 and we considered the aspect of the disc as it is viewed by the naked eye and with telescopes of various powers4 ,from this general survey we passed to the topography of the moon1 tracing briefly the admirable labours of those who have advanced this subject1 and1 by aid of picture and skeleton maps and a table of position co-ordinates1 placing it within the reader's power to become more than sufficiently acquainted for the purposes of this work with the names and positions of detail objects and features of interest4 ,special descriptions of interesting and typical spots and regions were given in some few cases where such appeared to be called for4 ,these descriptive matters disposed of1 we proceeded to discuss the various classes of surface features with a view to explaining the precise actions which appear to us to have led to their formation4 ,naturally the craters first demanded our attention4 ,we pointed out the reasons for regarding the great majority of the circular formations of the moon as craters1 as truly volcanic as those of which we have examples1 modified by obvious causes1 upon the earth2 and1 tracing the causative phenomena of terrestrial volcanoes1 we showed how the explanations which have been offered to account for them scarcely apply to those of the moon3 and thus1 driven to other hypotheses1 we endeavoured to demonstrate the probability of the lunar craters having been produced by eruptive force1 generated by that pre-solidifying expansion of successive portions of the moon's molten interior1 which we enunciated in our third chapter4 ,the precise course of phenomena which resulted in the production of a crater of the normal lunar type1 with or without the significant central cone1 were then illustrated by a series of step-by-step diagrams with accompanying descriptive paragraphs4 ,and after treating of craters of the normal type we pointed out and explained some variations thereupon that are here and there to be met with1 and likewise those curious complications of arrangement which exhibit craters superimposed one upon another and intermingled in strange confusion4 ,from craters manifestly volcanic we passed to the consideration of those circular formations which1 from their vastness of size1 scarcely admit of satisfactory explanation by a volcanic hypothesis4 ,we summarized several proffered theories of their origin1 and pointed out what we considered might be a possible key to the solution of the selenological enigma which they constitute1 without1 however1 expressing ourselves entirely satisfied with the validity of our suggestion4 ,the less mysterious features presented by peaks and mountain ranges were then discussed to the extent that we considered requisite1 viewing their comparatively simple character and the secondary position they occupy in point of numerical importance upon the moon4 ,at greater length we dealt with the cracks and chasms and the allied phenomena of radiating streaks1 pointing out with regard to these latter the strikingly beautiful correspondence in effect 7and therefore presumably in cause7 between them and crack-systems of a glass globe 8starred0 by an expanding internal medium4 ,the more notable objects and features of the lunar surface being disposed of1 we had next to say a few words upon some residual phenomena1 chiefly upon the colour of lunar surface details1 and upon their various degrees of brightness or reflective power4 ,and1 inasmuch as varying brightness seemed to us to be related to varying antiquity1 we were thence led to the question of the chronology of selenological formations1 and to the disputation upon the continuance of volcanic action upon the moon in recent years4 ,we regarded this question from the observational and the inferential points of view1 and were led to the conclusion that the moon's surface arrived at its terminal condition ages ago1 and that it is next to hopeless to look for evidence of existing change4 ,thus far our work dealt with the moon as a planetary body merely4 ,it occurred to us1 however1 that we might add to the interest attaching to our satellite were we to regard it for a time as a world1 and consider its conditions as respects fitness for habitation by beings like ourselves4 ,the arguments against the possibility of the moon being thus fitted for human creatures1 or1 indeed1 for any high organism1 were decisive enough to require little enforcing4 ,it appeared to us1 nevertheless1 that much might be learnt by imagining one's self located upon the moon during a period embracing one lunar day 7a month of our reckoning71 with power to comprehend the peculiar circumstances and conditions of such a situation4 ,we therefore attempted a description of an imaginary sojourn upon the moon1 and pointed out some of the more striking aspects and phenomena which we know by legitimate inference would be there manifested4 ,we trust1 that while our modest efforts in the chapter referring to this branch of our subject may prove in some degree entertaining1 they may be in a greater degree instructive1 inasmuch as certain facts are brought into prominence which would not unnaturally be overlooked in contemplating the moon from the earth1 the only real stand-point that is available to us4 ,in our final chapter we considered the moon as a satellite1 and sought to enhance popular regard for it on account of certain high functions which it performs for man's benefit on this earth2 but which are in great risk of being overlooked4 ,we showed that1 notwithstanding the moon's occasionally useful service as a nocturnal luminary1 it fills a far higher office as a sanitary agent by cleansing the shores of our seas and rivers through the agency of the tides4 ,we pointed out the vast amount of absolutely mechanical work and commercial labour which the same tidal agency executes in transporting merchandize up and down our rivers--an amount that1 to take the port of ,london alone1 represents a money value per annum that may be reckoned in millions sterling1 seeing that if our river was tideless all transport would have to be done by manual or steam power4 ,we then hinted at the stupendous reservoir of power that the tidal waters constitute1 a form of power which has not as yet been sufficiently called into operation1 but which may be invoked by-and-by1 when we have begun to feel more acutely the consequences of our present prodigal use of the fuel that was stored up for us by bountiful nature ages upon ages ago4 ,the moon's services to the navigator1 in affording him a ready means of finding his longitude at sea2 to the chronologist and historian1 as a timekeeper1 counting periods too vast for accurate reckoning by other means2 to the astronomer and student of nature1 in revealing certain wonderful surroundings of the solar globe1 which1 but for the phenomena of eclipses caused by the moon's interposition1 would never have been suspected to exist--these were other functions that we dwelt upon1 all too briefly for their deserts2 and1 lastly1 we spoke of the moon as a medal of creation fraught with instructive suggestions1 which it has been our endeavour to bring to notice in the course of this work4 ,and from uses we passed to abuses1 directing attention to a few popular errors and widespread illusions relating to lunar influence upon and in connection with things terrestrial4 ,this part of our work might have been considerably expanded1 for1 in truth1 the moon has been a misunderstood and misjudged body4 ,some justice we trust we have done to her3 we have brought her face to the fireside2 we have analysed her features1 and told of virtues that few of her admiring beholders conceived her to possess4 ,we have traced out her history1 fraught with wonderful interest1 and doubtless typical of the history of other spheres that in countless numbers pervade the universe3 and now1 having done our best to make all these points familiar1 we commend the moon to still further study and still more intimate acquaintance1 confident that she will repay all attentions1 be they addressed to her as ,a ,,planet1 ,a ,,world1 ,,or ,a ,,satellite4 ,,the ,,end4 ,,footnotes #a,the melting temperature of iron is #aejj ,centigrade4 #b,mr4 ,t4 ,heunter1 ,manager of the ,iron-works of ,james ,murray1 ,esq41 of ,dalmellington1 ,ayrshire4 ,another authority 7,mr4 ,snelus1 of the ,west ,cumberland ,iron ,company71 writes as follows3 8,i had a hole dug on the #8cinder-fall1' and allowed the running slag to flow through it so as to form a tolerably large pool and yet keep fluid4 ,any crust that formed was skimmed off4 ,a portion of the same slag was cooled1 and the solid lump thrown into the pool4 ,it floated just at the surface40 ,mr4 ,snelus adds1 by the way1 that he tried 8,bessemer-,pig0 in the same way1 and that the solid pig sunk in the molten for a minute and then rose and floated just at the surface1 with about one-twentieth of its bulk above the level of the fluid4 #c;,irradiation is an ocular phenomenon in virtue of which all strongly illuminated objects appear to the eye to be larger than they really are4 ,the impression produced by light upon the retina appears to extend itself around the focal image formed by the lenses of the eye4 ,it is from the effect of irradiation that a white disc on a black ground looks larger than a black disc of the same size on a white ground4 #d;,for the original photograph from which this plate was produced1 and for permission to reproduce it1 we owe our acknowledgments to ,warren ,de la ,rue and ,joseph ,beck1 ,esquires4 #e,the proper distance for realising the conditions under which the moon itself is seen will be that at which our disc is just covered by a wafer about a quarter of an inch in diameter1 held at arm's length4 ,this will subtend an angle of about half a degree1 which is nearly the angular diameter of the moon4 #f,the libratory movement has been taken advantage of1 at the suggestion of ,sir ,chas4 ,wheatstone1 for producing stereoscopic photographs of the moon4 ,in the early days of stereoscopic photography the object to be photographed was placed upon a kind of turn-table1 and1 after a picture had been taken of it in one position1 the table was turned through a small angle for the taking of the second picture2 the two placed side by side then represented the object as it would have been seen by two eyes widely separated1 or whose visual rays inclined at an angle equal to that through which the table was turned2 and when the pictures were viewed through a stereoscope1 they combined to produce the wonderful effect of solidity now familiar to every one4 ,the moon1 by its librations1 imitates the turn-table movement2 and1 from a large number of photographs of her1 taken at different points of her orbit and at different seasons of the year1 it is possible to select two which1 while they exhibit the same phase of illumination1 at the same time present the requisite difference in the points of view from which they are taken to give the effect of stereoscopicity when viewed binocularly4 ,mr4 ,de la ,rue1 the father of celestial photography1 has been enabled to produce several such pairs of pictures from the vast collection of lunar photographs that he has accumulated4 ,any one of these pairs of portraits1 when stereoscopically combined1 reproduces1 to quote the words of ,sir ,john ,herschel1 8the spherical form just as a giant might see it whose stature were such that the interval between his eyes should equal the distance between the place where the earth stood when one view was taken1 and that to which it would have to be removed 7our moon being fixed7 to get the other4 ,nothing can surpass the impression of real corporeal form thus conveyed by some of these pictures as taken by ,mr4 ,de la ,rue with his powerful reflector1 the production of which 7as a step in some sort taken by man outside of the planet he inhabits7 is one of the most remarkable and unexpected triumphs of scientific art40 #g,this is a point of some uncertainty4 ,dr4 ,young stated 7,lectures ,vol4 ,,ii4 p4 #ege7 that 8a minute is perhaps nearly the smallest interval at which two objects can be distinguished1 although a line subtending only a tenth of a minute in breadth may sometimes be perceived as a single object40 #h,plate ,,viii4 #i8;,cosmos10 ,bohn's ,edition1 ,vol4 ,v4 p4 #cbb4 #aj;,american ,journal of ,science1 ,second ,series1 ,vol4 ,,ii4 #aa8,volcanoes10 page #aee4 #ab;,in reference to such prominences on the lunar surface as cast steeple-like shadows1 it is well to remark that we must not in all cases infer1 from the acute spire-like form of the shadow1 that the object which casts the shadow is of a similar sharp or spire-like form1 which the first impression would naturally lead us to suppose4 ,a comparatively blunt or rounded eminence will project a long and pointed shadow when the rays of light fall on the object at a low angle1 and especially so when the shadow is projected on a convex surface4 ,we illustrate this with a copy of an actual photograph of the shadow cast by half a pea1 ,fig4 #da4 #ac,we meet a difficulty in reconciling this idea with the partial craters of which we have a conspicuous example in ,fracastorius1 ,no4 #gh1 of our ,map1 which seem to be partially sunk below the contiguous surface4 ,this looks as though the crater-rim belonged to an older epoch than the plain from which it rises4 #ad,we are informed by a friend1 who has lately visited ,athens1 that ,schmidt's detail drawings of the ,moon1 comprising the work of forty years1 form a small library in themselves4 ,the map embodying them is so large 7#f ft4 #f in4 in diameter7 and so full of detail that there is small hope of its complete publication1 unless there should be such a wide extension of interest in the minute study of our satellite as to justify the cost of reproducing it4 #ae;,it is conceivable that the alleged changes in the crater ,linn may have been caused by a filling of the crater by some such crumbling action as we are here contemplating4 #af;,is it not conceivable that the protogerms of life pervade the whole universe1 and have been located upon every planetary body therein8 ,sir ,william ,thomson's suggestion that life came to the earth upon a seed-bearing meteor was weak1 in so far that it shifted the locus of life-generation from one planetary body to another4 ,is it not more philosophical1 more consistent with our conception of ,creative omnipotence and impartiality1 to suppose that the protogerms of life have been sown broadcast over all space1 and that they have fallen here upon a planet under conditions favourable to their development1 and have sprung into vitality when the fit circumstances have arrived1 and there upon a planet that is1 and that may be for ever1 unfitted for their vivification8 #ag,our remarks have general reference to a region of the moon near her equator2 near the poles some of the conditions we shall describe would be somewhat modified4 #ah,we see this reddening during an eclipse of the moon 7when the event we are describing--an eclipse of the sun visible from the moon--really takes place74 ,the blood-red colour has often struck observers very forcibly1 and it has indeed been suggested that the appearance may be the innocent and oft-repeated fulfilment of the prophetic allusion to the moon being 8turned into blood40 #ai;,about #ajj years ago ,london was supplied with water chiefly by pumps worked by tidal mills at ,london ,bridge4 #bj,the sun and planets are comparatively useless for this object1 because of their slow movement among the stars2 the change of their positions from hour to hour is so small as to render uncertain the ,greenwich times deducible therefrom4 ,their use would be comparable to taking the time from the hour-hand of a clock4 ,,bradbury1 ,,agnew1 ,,co41 ,,printers1 ,,whitefriars4 ,albemarle ,street1 ,december1 #ahgc4 ,,works ,,on ,,science1 c4 ,a ,,naturalist',s ,,voyage ,,round ,,the ,,world4 ,by ,charles ,darwin1 ,f4,r4,s4 ,with ,illustrations4 ,post #hvo4 #is4 ,,the ,,origin ,,of ,,species1 ,,by ,,means ,,of ,,natural ,,selection2 or1 the ,preservation of ,favoured ,races in the ,struggle for ,life4 ,by ,charles ,darwin1 ,f4,r4,s4 ,with ,illustrations4 ,post #hvo4 #gs4 #f;d4 ,,the ,,fertilization ,,of ,,orchids ,,through ,,insect ,,agency4 ,by ,charles ,darwin1 ,f4,r4,s4 ,with ,woodcuts4 ,post #hvo4 #is4 ,,the ,,variation ,,of ,,animals ,,and ,,plants ,,under ,,domestication4 ,by ,charles ,darwin1 ,f4,r4,s4 ,with ,illustrations4 #b vols4 #hvo4 #bhs4 ,,the ,,descent ,,of ,,man1 ,,and ,,on ,,selection ,,in ,,relation ,,to ,,sex4 ,by ,charles ,darwin1 ,f4,r4,s4 ,with ,illustrations4 #b vols4 ,crown #hvo4 #bds4 ,,the ,,expression ,,of ,,the ,,emotions ,,in ,,man ,,and ,,animals4 ,by ,charles ,darwin1 ,f4,r4,s4 ,with ,illustrations4 ,crown #hvo4 #abs4 ,,facts ,,and ,,arguments ,,for ,,darwin4 ,by ,fritz ,muller4 ,translated by ,w4 ,s4 ,dallas1 ,f4,l4,s4 ,with ,illustrations4 ,post #hvo4 #fs4 ,,the ,,student',s ,,elements ,,of ,,geology4 ,by ,sir ,charles ,lyell1 ,f4,r4,s4 ,with #fjj ,woodcuts4 ,post #hvo4 #is4 ,,principles ,,of ,,geology2 or1 the ,modern ,changes of the ,earth and its ,inhabitants1 considered as illustrative of ,geology4 ,by ,sir ,charles ,lyell1 ,f4,r4,s4 ,with ,illustrations4 #b vols4 #hvo4 #afs4 each4 ,,the ,,antiquity ,,of ,,man1 ,,from ,,geological ,,evidences2 with ,remarks on ,theories of the ,origin of ,species by ,variation4 ,by ,sir ,charles ,lyell1 ,f4,r4,s4 ,with ,illustrations4 #hvo4 #ads4 ,a ,,geographical ,,handbook ,,of ,,all ,,the ,,known ,,ferns1 with ,tables to show their distribution4 ,by ,k4 ,m4 ,lyell4 ,post #hvo4 #gs4 #f;d4 ,a ,,manual ,,of ,,scientific ,,inquiry4 ,for the ,use of ,travellers4 ,edited by ,sir ,j4 ,f4 ,herschel and ,rev4 ,robert ,main4 ,post #hvo4 #cs4 #f;d4 ,,the ,,connection ,,of ,,the ,,physical ,,sciences4 ,by ,mary ,somerville4 ,post #hvo4 #is4 ,,physical ,,geography4 ,by ,mary ,somerville4 ,post #hvo4 #is4 ,,molecular ,,and ,,microscopic ,,science4 ,by ,mary ,somerville4 ,illustrations4 #b vols4 ,post #hvo4 #bas4 ,,personal ,,recollections ,,from ,,early ,,life ,,to ,,old ,,age ,,of ,,mary ,,somerville4 ,with ,selections from her ,correspondence4 ,by ,her ,daughter4 ,with ,portrait4 ,crown #hvo4 #abs4 ,,the ,,rivers1 ,,mountains1 ,,and ,,sea-,,coast ,,of ,,yorkshire4 ,with ,essays on the ,climate1 ,scenery1 and ,ancient ,inhabitants of the ,country4 ,by ,john ,phillips1 ,f4,r4,s4 ,plates1 #hvo4 #aes4 ,,records ,,of ,,the ,,rocks2 or1 ,notes on the ,geology1 ,natural ,history1 and ,antiquities of ,north and ,south ,wales1 ,devon1 and ,cornwall4 ,by ,rev4 ,w4 ,s4 ,symonds1 ,f4,g4,s4 ,with ,illustrations4 ,crown #hvo4 #abs4 ,,researches ,,into ,,the ,,early ,,history ,,of ,,mankind1 ,,and ,,the ,,development ,,of ,,civilization4 ,by ,e4 ,b4 ,tylor1 ,f4,r4,s4 #hvo4 #abs4 ,,primitive ,,culture2 ,researches into the ,development of ,mythology1 ,philosophy1 ,religion1 ,art1 and ,custom4 ,by ,e4 ,b4 ,tylor1 ,f4,r4,s4 #b vols4 #hvo4 #bds4 ,,siluria2 a ,history of the ,oldest ,rocks in the ,british ,isles and other ,countries1 with a ,sketch of the ,distribution of ,native ,gold4 ,by ,sir ,roderick ,murchison1 ,f4,r4,s4 ,with ,illustrations4 #b vols4 #hvo4 #ahs4 ,,the ,,strength ,,of ,,iron ,,and ,,steel4 ,by ,k4 ,styffe4 ,translated from the ,swedish4 ,by ,christer ,p4 ,sandberg1 ,c4,e4 ,with ,lithographs4 #hvo4 #abs4 ,a ,,practical ,,treatise ,,on ,,ship-,,building ,,in ,,iron ,,and ,,steel4 ,by ,e4 ,j4 ,reed1 ,c4,b4 ,with ,illustrations4 #hvo4 ,,our ,,iron-,,clad ,,ships2 their ,qualities1 ,performances1 and ,cost1 with ,chapters on ,turret ,ships1 ,iron-clad ,rams1 c4 ,by ,e4 ,j4 ,reed1 ,c4,b4 ,with ,illustrations4 #hvo4 #abs4 ,,the ,,naturalist ,,in ,,nicaragua2 a ,narrative of a ,residence at the ,gold ,mines of ,chontales2 ,journeys in the ,savannahs and ,forests2 with ,observations on ,animals and ,plants in reference to the ,theory of ,evolution of ,living ,forms4 ,by ,thomas ,belt4 ,with ,illustrations4 ,post #hvo4 #abs4 ,,the ,,naturalist ,,on ,,the ,,river ,,amazons2 ,during ,eleven ,years of ,travels and ,adventures4 ,by ,h4 ,w4 ,bates4 ,with ,illustrations4 ,post #hvo4 #gs4 #f;d4 ,,lives ,,of ,,british ,,engineers2 from the ,earliest ,times to the ,death of ,robert ,stephenson4 ,comprising a ,history of the ,invention and ,introduction of the ,steam ,engine and ,railway ,locomotive4 ,with ,portraits and #cej ,illustrations4 #d vols4 ,medium #hvo4 #hds4 ,,history ,,of ,,the ,,modern ,,styles ,,of ,,architecture4 ,by ,james ,fergusson1 ,f4,r4,s41 ,d4,c4,l41 ,fellow of the ,royal ,institute of ,british ,architects4 ,with #ccj ,illustrations4 ,medium #hvo4 #cas4 #f;d4 ,,rude ,,stone ,,monuments ,,in ,,all ,,countries2 their ,age and ,uses4 ,by ,james ,fergusson1 ,f4,r4,s4 ,with #bcj ,illustrations4 ,medium #hvo4 #bds4 ,a ,,history ,,of ,,pottery3 ,egyptian1 ,assyrian1 ,greek1 ,etruscan1 and ,roman4 ,by ,samuel ,birch1 ,f4,s4,a4 ,with ,coloured ,plates1 and #bjj ,woodcuts4 ,medium #hvo4 #dbs4 ,a ,,history ,,of ,,pottery3 ,medival and ,modern4 ,by ,joseph ,marryat4 ,with ,coloured ,plates1 and #cjj ,woodcuts4 ,medium #hvo4 #dbs4 ,,the ,,national ,,memorial ,,to ,h4,r4,h4 ,,the ,,prince ,,consort1 ,,at ,,kensington4 ,consisting of ,coloured ,views and other ,engravings of the ,monument and its ,decorations1 its ,sculptured ,groups1 ,statues1 ,mosaics1 ,architecture1 and ,details of ,metalwork1 c41 designed and executed by the most eminent ,british ,artists4 ,with ,descriptive ,text4 ,with #bd ,plates1 and ,woodcuts4 ,folio1 #abl4 #abs4 ,large ,paper 7only #ej printed71 #ael4 #aes41 half-bound2 or ,special ,copies1 in full morocco1 #ahl4 #ahs4 ,,brick ,,and ,,marble ,,architecture ,,of ,,the ,,middle ,,ages4 ,with ,notes of ,tours north of the ,apennines1 including ,aquilei1 ,udine1 ,vicenza1 ,ferrara1 ,bologna1 ,piacenza1 ,modena1 and ,vercelli4 ,by ,g4 ,e4 ,street1 ,r4,a4 ,with ,illustrations4 ,royal #hvo4 ,,the ,,gothic ,,architecture ,,of ,,spain3 from ,personal ,observations made during ,several ,journeys4 ,by ,g4 ,e4 ,street4 #bnd ,edition4 ,with #ajj ,illustrations4 ,royal #hvo4 #cjs4 ,,horse-,,shoeing2 ,,as ,,it ,,is1 ,,and ,,as ,,it ,,should ,,be4 ,by ,william ,douglas1 late of #ajth ,hussars4 ,with ,illustrations4 ,post #hvo4 #gs4 #f;d4 ,,the ,,harvest ,,of ,,the ,,sea4 ,including ,sketches of ,fisheries and ,fisher ,folk4 ,by ,james ,g4 ,bertram4 ,with #ej ,illustrations4 ,post #hvo4 #is4 ,,the ,,longevity ,,of ,,man3 ,,its ,,facts ,,and ,,its ,,fictions4 ,including an ,inquiry into some of the more ,remarkable ,instances and ,suggestions for ,testing ,reputed ,cases4 ,illustrated by ,examples4 ,by ,william ,j4 ,thoms1 ,f4,s4,a4 ,post #hvo4 #ajs4 #f;d4 ,,metallurgy3 the ,art of ,extracting ,metals from their ,ores1 and adapting them to various purposes of ,manufacture4 ,by ,john ,percy1 ,f4,r4,s4 ,with ,illustrations4 #hvo4 ,vol4 ,i4--,fuel1 ,wood1 ,peat4 ,coal1 ,charcoal1 ,coke4 ,fire-,clays4 ,copper1 ,zinc1 and ,brass4 ,with #aej ,illustrations4 #hvo4 ,vol4 ,,ii4--,iron and ,steel4 ,with #bbj ,illustrations4 #hvo4 ,vol4 ,,iii4--,lead1 including ,desilverization and ,cupellation4 ,with ,illustrations4 #hvo4 #cjs4 ,vols4 ,,iv4 and ,v4--,gold1 ,silver1 and ,mercury4 ,platinum1 ,tin1 ,nickel1 ,cobalt1 ,antimony1 ,bismuth1 ,arsenic and other ,metals4 ,with ,illustrations4 #hvo4 ,in preparation4 ,,manufacture ,,of ,,russian ,,sheet-,,iron1 with every detail of the process illustrated4 ,by ,john ,percy1 ,f4,r4,s4 ,with ,illustrations4 #hvo4 #bs4 #f;d4 ,,john ,,murray1 ,,albemarle ,,street4 ,transcriber's ,notes --,retained copyright information from the printed edition3 this e,book is public-domain in the country of publication4 --,silently corrected a few palpable typos4 --,in the text versions only1 text in italics is delimited by underscores4