LN. S. VOL. IX. No. 229.

tronomer und Physiker gedruckt zu sehen, babe icb,als Nacbfolger Ibres Vaters, jetzt in seiner Dienstwoh-nung befindlich, und als Herausgeber seiner grossenWerke, mir erlaubt lbren Namen mit in die Listeeinsetzen zu lassen. Es war nicht mehr Zeit Sie umIbre Erlaubnis dazu zu fragen, aber es kann bei mirkein Zweifel sein iuber lhre Genebmigung. Gernewerde ich mir erlauben, Ihnen weiteren Bericht fiberdie Denkmalsfrage abzustatten, so bald etwas defini-tives feststeht.

Der Prinz Albrecbt von Preussen, Prinz Regentvom Herzogthum Braunschweig, Rector Magnificentis-simus von der Universitat Gottingen, hat sich bereitfinden lassen, das Protectorat der Commnission fur dasDenkmal zu jibernebmen. Er hat befoblen, dass aus

Landesmitteln des Herzogthums Braunschweig 3000Mk. fur das Denkmal gegeben wverden. Das ist jaemn sebrguter Anfang. In den Zeitungen babe ichdie Notiz gelesen:

Gauns, E. F. L. erster Assistent von Frederik H.Hild dem Librarian of the Chicago Public Library.Gehort dieser Gauss auch zu der beriibmten Familie ?*

Da das Deutsche Reich sich auch amtlich an dergrossen Ausstellung in Chicago betbeiligt, so wirdwahrscheinlich das Post-und Telegraphen-Museumin Berlin unter dem Reichsekretair von Stephan auchdie Hauptstiicke seiner geschichtlichen Sammiungdorthin senden. Darunter findet sich ein Gemiildevon dem grossen Gauss und eine Reproduction sein s

ersten Telegraphen. Jenes Geniiilde ist Gauss sehrahnlich, aber noch schoner finde ich das Gemilde,welches sich hier in seinem Erdmagnetischen Obser-vatoriuni unter meinem Gewahrsam befindet. Es istvon der Preussisbehn Regierung zum 150 jiihrigenJubilaeum derUniversitiit Gottingen 1887 dem Insti-tute gescbenkt worden. Ueberbaupt war dieses Jubi-laeum ein grossartiges Fest zur Verherrlichung von

Gauss. Keine der vielen Tischreden, keine Festrede,keine Predigt wurde gelhalten, ohne dass sein Namegenannt und seine Erfindung des Electrischen Tele-graphen erwiihnt worden waire. Seit jener Zeit befin-det sich auch seine Marmortafel an der Sternwarte,Abtheilung des Erdmiagnetischen Observatorium, mitder Aufschrift

Erster electrischer TelegraphGALTSS-WEBER

Ostern, 1833

* Mr. Robert Gauss, a son of Eugene Gauss andnow managing editor of the Denver Republican, in-forms me that the E. F. L. Gauss in question is nota descendant of Gauss the mathematician. Schering'sletter is in the possesssion of Robert Gauss, throughwhose kindness the writer was permitted to make a

copy of it.

Mit den ergebensten Empfeblungen zeichne iclhmich Ihr ERNST SCHERING,Herausgeber der Gauss'schen Werke. Gemeinrath

u. Professor.FLORIAN CAJORI.

COLORADO COLLEGE, COLORADO SPRINGS.

THE AGE OF THE EARTH AS AN ABODEFITTED FOR LIFE.

II.PROBABLE ORIGIN OF GRANITE.

§ 26. UPON the suppositions we havehitherto made we have, at the stage nowreached, all round the earth at the same

time a red-hot or white-hot surface of solidgranules or crystals with interstices filledby the mother liquor still liquid, but readyto freeze with the slightest cooling. Thethermal conductivity of this heterogeneousmass, even before the freezing of the liquidpart, is probably nearly the same as thatof ordinary solid granite or basalt at a redheat, which is almost certainly* somewhatless than the thermal conductivity ofigneous rocks at ordinary temperatures.If you wish to see for yourselves howquickly it would cool when wholly solidi-fied take a large macadamizing stone, andheat it red hot in an ordinary coal fire.

Take it out with a pair of tongs and leaveit on the hearth, or on a stone slab at a dis-tance from the fire, and you will see that ina minute or two, or perhaps in less than a

minute, it cools to below red heat.§27. Half an hourt after solidification

reached up to the surface in any part of theearth, the mother liquor among the granulesmust have frozen to a depth of severalcentimeters below the surface and musthave cemented together the granules and

crystals, and so formed a crust of primevalgranite, comparatively cool at its upper

surface, and red hot to white hot, but still* Proc. R. S., May 30, 1895.t Witness the rapid cooling of lava running red hot

or white hot from a volcano, and after a few days or

weeks presenting a black, hard crust strong enoughand cool enough to be walked over with impunity.

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all solid, a little distance down; becomingthicker and thicker very rapidly at first;.and after a few weeks certainly coldenough at its outer surface to be touchedby the hand.

PROBABLE ORIGIN EF BASALTIC ROCK.*

§ 28. We have hitherto left, withoutmuch consideration, the mother liquoramong the crystalline granules at alldepths below the bottom of our shoalinglava ocean. It was probably this inter-stitial mother liquor that was destined toform the basaltic rock of future geologicaltime. Whatever be the shapes and sizesof the solid granules when first falling tothe bottom, they must have lain in looseheaps with a somewhat large proportion ofspace occupied by liquiid among them.But, at considerable distances down in theheap, the weight of the superincumbentgranules must tend to crush corners and,edges into fine powder. Ifthe snow showerhad taken place in air we may feel prettysure (even with the slight knowledge whichwe have of the hardnesses of the crystals offeldspar, mica and hornblende, and of the,solid granules of quartz) that, at a depth of10 kilometers, enough of matter from thecorners and edges of the granules of dif-ferent kinds, would have been crushed intopowder of various degrees of fineness, toleave an exceedingly small proportionatevolume of air in the interstices between the,solid fragments. But in reality the effec-tive weight of each solid particle, buoyed.as it was by bydrostatic pressure of a liquidless dense than itself by not more than 20or 15 or 10 per cent., cannot have beenmore than from about one-fifth to one-

tenth of its weight in air, and therefore thesame degree of crushing effect as wouldhave been experienced at 10 kilometerswith air in the interstices, must have been

* See Addendum at end of Lecture.

experienced only at depths of from 50 to100 kilometers below the bottom of the lavaocean.

§ 29. A result of this tremendous crush-ing together of the solid granules must havebeen to press out the liquid from among

them, as water from a sponge, and cause itto pass upwards through the less and lessd'losely packed heaps of solid particles, andout into the lava ocean above the heap.But, on account of the great resistanceagainst the liquid permeating upwards 30or 40 kilometers through interstices amongthe solid granules, this process must havegone on somewhat slowly; and, during all

the time of the shoaling of the lava ocean,

there may have been a considerable pro-

portion of the whole volume occupied bythe mother liquor among the solid granules,down to even as low as 50 or 100 kilo-meters below the top of the heap, or bottomof the ocean, at each instant. When con-

solidation reached the surface, the oozingupwards of the mother liquor must have

been still going on to some degree. Thus,probably for a few years after the first con-

solidation at the surface, not probably foras long as one hundred years, the settle-ment of the solid structure by mere me-

chanical crushing of the corners and edgesof solid granules, may have continued tocause the oozing upwards of mother liquorto the surface through cracks in the firstformed granite crust and through freshcracks in basaltic crust subsequently formedabove it.

LEIBNITZ S CONSISTENTIOR STATUS.

§ 30. When this oozing everywherethrough fine cracks in the surface ceases,

we have reached Leibnitz's consistentiorstatus; beginning with the surface cooland permanently solid and the tempera-ture increasing to I150' C. at 25 or 50 or

100 meters below the surface.

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PROBABLE ORIGIN OF CONTINENTS AND OCEAN

DEPTHS OF THE EARTH.

§ 31. If the shoaling of the lava ocean up

to the surface had taken place everywhereat the same time, the whole surface of theconsistent solid would be the dead level ofthe liquid lava all round, just before itsdepth became zero. On this suppositionthere seems no possibility that our present-day continents could have risen to theirpresent heights, and that the surface of thesolid in its other parts could have sunkdown to their present ocean depths, duringthe twenty or twenty-five million years

which may have passed since the con-

sistenttor status began or during any timehowever long. Rejecting the extremelyimprobable hypothesis that the continentswere built up of meteoric matter tossedfrom without, upon the already solidifiedearth, we have no other possible alternativethan that they are due to heterogeneous-ness in different parts of the liquid whichconstituted the earth before its solidifica-tion, The hydrostatic equilibrium of therotating liquid involved only homogeneous-ness in respect to density over every levelsurface (that is to sav, surface perpen-

dicular to the resultant of gravity and cen-

trifugal force); it required no homogeneous-ness in respect to chemical composition.Considering the almost certain truith thatthe earth was built up of meteorites fallingtogether, we may follow in imalgination thewhole process of shrinking from gaseousnebula to liquid larva and metals, andsolidification of liquid from central regionsoutwards, without finding any thoroughmixing up of different ingredients, comingtogether from different directions of space-any mixing up so thorough as to produceeven approximately chemical homogene-ousness throughout every layer of equaldensity. Thus we have no difficulty inunderstanding how even the gaseous

nebula, which at one time constituted the

matter of our present earth, had in itself a

heterogeneousness from which followed bydynamical necessity Europe, Asia, Africa,America, Australia, Greenland and theAntarctic Continent, and the Pacific, At-lantic, Indian and Arctic Ocean depths, as

we know them at present.§ 32. We may reasonably believe that a

very slight degree of chemical heterogene-ousness could cause great differences in theheaviness of the snow shower of granulesand crystals on different regions of the bot-tom of the lava ocean when still 50 or 100kilometers deep. Thus we can quite see

how it may have shoaled much more

rapidly in some places than in others. Itis also interesting to cornsider that the solidgranules, falling on the bottom, may havebeen largely disturbed, blown as it were

into ridges (like rippled sand in the bed ofa flowing stream, or like dry sand blowninto sand-hills by wind) by the eastwardhorizontal motion which liquid descendingin the equatorial regions must acquire,relatively to the bottom, in virtue of theearth's rotation. It is, indeed, not im-probable that this influence may have beenlargely effective in producing the generalconfiguration of the great ridges of theAndes and Rocky Mountains and of theWest Coasts of Europe and Africa. Itseems, however, certain that the main de-termining cause of the continents andocean-depths was chemical differences, per-

haps very slight differences, of the materialin different parts of the great lava ocean

before consolidation.§ 33. To fix our ideas let us now suppose

that over some great areas such as thosewhich have since become Asia, Europe,Africa, Australia and America, the lavaocean had silted up to its surface, while inother parts there still were depths rangingdown to 40 kilometers at the deepest. Ina very short time, say about twelve years

according to our former estimate (§ 24), the

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whole lava ocean becomes silted up to itssurface.

§ 34. We have not time enough at pres-ent to think out all the complicated ac-tions, hydrostatic and thermodynamic,which must accompany, and follow after,the cooling of the lava ocean surroundingour ideal primitive continent. By a hur-ried view, however, of the affair we seethat in virtue of, let us say, 15 per cent.shrinkage by freezing, the level of theliquid must, at its greatest supposed depth,sink six kilometers relatively to the con-tinents, and thus the liquid must recedefrom them, and their bounding coast-linesmust become enlarged. And just as waterruns out of a sandbank, drving when thesea recedes from it on a falling tide, sorivulets of the mother liquor must run outfrom the edges of the continents into thereceding lava ocean. But, unlike sand-banks of incoherent sand permeated bywater remaining liquid, our uncoveredbanks of white-hot solid crystals, with in-terstices full of the mother liquor, will,within a few hours of being uncovered, be-come crusted into hard rock by cooling atthe surface, and freezing of the liquor, ata temperature somewhat lower than themelting temperatures of any of the crystalspreviously formed. The thickness of thewholly solidified crust grows at first withextreine rapidity, so that in the course ofthree or four days it may come to be asmuch as a meter. At the end of a year itmay be as much as ten meters; with a sur-face, almost, or quite, cool enough for somekinds of vegetation. In the course of thefirst few weeks the regime of conduction ofheat outwards becomes such that the thick-ness of the wholly solid crust, as long asit remains undisturbed, increases as thesquare root of the time; so that in 100years it becomes 10 times, in 25 millionyears 5,000 times, as thick as it was at theend of one year; thus, from one year to 25

million years after the time of surface freez-ing, the thickness of the wholly solid criustmight- grow from 10 meters to 50 kilo-meters. These definite numbers are givenmerely as an illustration, but it is probablethat they are not enormously far from thetruth in respect to what has happened undersome of the least disturbed parts of theearth's surface.

§ 35. We have now reached the conditiondescribed above in § 30, with only this dif-ference, that instead of the upper surface ofthe whole solidified crust being level wehave in virtue of the assumptions of §§ 33,34, inequalities of 6 kilometers froni highestto lowest levels, or as much more than 6kilometers as we please to assume it.

§ 36. There must still be a small, but im-portant, proportion of mother liquor in theinterstices between the closely packed un-cooled crystals below the wholly solidifiedcrust. This liquor, differing in chemicalconstitution from the crystals, has its freez-ing-point somewhat lower, perhaps verylargely lower, than the lowest of theirmelting-points. But, when we consider themode of formation (§25) of the cryetals,from the mother liquor, we must regard itas still always a solvent ready to dissolve,and to redeposit, portions of the crystallinematter, when slight variations of tempera-ture or pressure tend to cause such actions.Now as the specifie, gravity of the liquor isless, by something like 15 per cent., thanthe specific gravity of the solid crystals, itmust tend to find its way upwards, and willactually do so, however slowly, until stoppedby the already solidified impermeable crust,or until itself becomes solid on account ofloss of heat by conduction outwards. Ifthe upper crust were everywhere continuousand perfectly rigid the mother liquor must,inevitably, if sufficient time be given, findits way to the highest places of the lowerboundary of the crust, and there formgigantic pockets of liquid lava tending to

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break the crust above it and burst up

through it.§ 37. But in reality the upper crust can-

not have been infinitely strong; and, judg-ing alone from what we know of propertiesof matter, we should expect gigantic cracksto occur from time to time in the upper

crust tending to shrink as it cools and pre-

vented from lateral shrinkage by the non-

shrinking uncooled solid below it. Whenany such crack extends downwards as faras a pocket of mother liquor underlying thewholly solidified crust, we should have an

outburst of trap rock or of volcanic lavajust such as have been discovered by geolo-gists in great abundance in many parts ofthe world. We might even have compara-

tively small portions of high plateaus of theprimitive solid earth raised still higher byoutbursts of the mother liquor squeezed outfrom below them in virtue of the pressure

of large surrounding portions of the super-

incumbent crust. In any such action, dueto purely gravitational energy, the center ofgravity of all the material concerned mustsink, although portions of the matter maybe rai$sed to greater heights; but we mustleave these large questions of geological dy-namics, having been only brought to thinkof them at all just now by our considerationof the earth antecedent to life upon it.

§ 38. The temperature to which theearth's surface cooled within a few years

after the solidification reached it must havebeen, as it is now, such that the temperature,at which heat radiated into space during thenight exceeds that received from the sun

during the day by the small difference duieto heat conducted outwards from within.One year after the freezing of the granitic

* Suppose, for example, the cooling and thickeningof the upper crust has preceeded so far that at thesurface, and, therefore, approximately for a few deci-nietres below the surface, the rate of augmentation oftemperature downwards is one degree per centimeter.Taking as a rough average 005 c. g. s. as the thermalconductivity of the surface rock, we should have for

interstitial mother liquor at the earth's sur-

face in any locality the average tempera-ture at the surface might be warmer, by 60°or 800 Cent., than if the whole interior hadthe same average temperature as the sur-

face. To fix our ideas, let us suppose atthe end of one year the surface to be 80°warmer than it would be with nd under-ground heat; then at the end of 100 years

it would be 8° warmer, and at the end of10,000 years it would be -8 of a degreewarmer, and at the end of 25 million years

it would be 016 of a degree warmer, thanif there were no underground heat.

§ 39. When the surface of the earth was

still white-hot liquid all round, at a tem-perature fallen to about 1200° Cent., theremust have been hot gases and vapor ofwater above it in all parts, and possiblyvapors of some of the more volatile of thepresent known terrestrial solids and liquids,such as zinc, mercury, sulphur, phosphorus.The very rapid cooling which followed in-stantly on the solidification at the surface

the heat conducted outwards .005 of a gramme waterthermal unit Centigrade per sq. cm. per see. (KelvinMath. and Phys. Papers, Vol. III., p. 226). Hence,if (ibid. p. 223) we take 8000 as the radiational em-

issivity of rock and atmosphere of gases and wateryvapor above it radiating heat into the surroundingvacuous space (oether), we find 8000 X .005 or 40 de-grees Cent. as the excess of the mean surface tempera-ture above what it would be if no heat were conduc-ted from within,outwards. The present augmentationof temperature downwards miay be taken as 1 degreeCent. per 27 meters as a rough average derived fromobservations in all parts of the earth where under-ground temperature has been observed. (See BritishAssociation Reports from 1868 to 1895. The very

valuable work of this Commnittee has been carried on

for these twenty-seven years, with great skill, perse-

verance and success, by Professor Everett, and hepromises a continuation of his reports from time totime.) This, with the same data for conductivity andradiational emissivity as in the preceding calculation,makes 400/2700 or 0.01480 Cent. per centimeter as theamount by which the average temperature of theearth's surface is at present kept up by undergroundheat.

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must have caused a rapid downpour of allthe vapors other than water, if any therewere; and, a little later, rain of water outof the air, as the temperature of the surfacecooled from red heat to such moderate tem-peratures as 40° and 20° and 10' Cent.above the average due to sun heat and radi-ation into the ether around the earth.W,rhat that primitive atmosphere was, andhow much rain of water fell on the earth inthe course of the first century after consoli-dation, we cannot tell for certain; but Natu-ral History and Natural Philosophy give ussome foundation for endeavors to discovermuch towards answering the great ques-tions: Whence came our present atmos-phere of nitrogen, oxygen and carbonicacid? Whence came our present oceansand lakes of salt and fresh water? Hownear an approximation to present conditionswas realized in the first hundred centuriesafter consolidation of the surface.

§ 40. We may consider it as quite certainthat nitrogen gas, carbonic acid gas andsteam, escaped abundantly in bubbles fromthe mother liquor of granite, before theprimitive consolidation of the surface, andfrom the mother liquor squeezed up frombelow in subsequent eruptions of basalticrock, cause all, or inearly all, specimensof granite and basaltic rock which havebeen l,ested by chemists in respect tothis question,* have been found to con-tain, condensed in minute cavities withinthem, large quantities of nitrogen, car-bonic acid and water. It seems that inno specimen of granite or basalt tested haschemically free oxygen been discovered,while in many, chemically free bydrogenhias been found, and either native iron ormagnetic oxide of iron in those which docontain hydrogen. From this it mightseem probable that there was no free oxy-

*See, for example, Tilden, Proc. R. S. February4, 1897: 'On the Gases Enclosed in CrystallineElocks and Minerals.'

gen in the primitive atmosphere, and thatif there was free hydrogen it was due tothe decomposition of steam by iron or mag-netic oxide of iron. Going back to stillearlier conditions we might judge that,probably, among the dissolved gases of thehot nebula which became the earth, theoxygen all fell into combination with hy-drogen and other metallic vapors in the cool-ing of the neubla, and that, although it isknown to be the most abundant materialof all the chemical elements constituting theearth, none of it was left out of combinationwith other elements to give free oxygen inour primitive atmosphere.

§ 41. It is, however, possible, althoughit might seem not probable, that there wasfree oxygen in the primitive atmosphere.With or without free oxygen, however, butwith sunlight, we may regard the earth asfitted for vegetable life as now known insome species, wherever water moistenedthe newly solidified rocky crust cooled downbelow the temperature of 80° or 70° of ourpresent Centigrade thermometric scale ayear or two after solidification of the primi-tive lava had come up to the sturface. Thethick, tough, velvety coating of living vege-table matter, covering the rocky slopesunder hot water flowing direct out of theearth at Banif (Canada) ,* lives withouthelp from any ingredients of the atmosphereabove it, ind takes from the water andfrom carbonic acid or carbonates, dissolvedin it, the hydrogen and carbon needed forits own growth by the dynamical power ofsunlight; thus leaving free oxygen in thewater to pass ultimately into the air. Simi-lar vegetation is found abundantly on theterraces of the Mammoth hot springs and onthe beds of the hot-water streams flowingfrom the Geysers in the Yellowstone Na-tional Park of the United States. This vege-tation, consisting of confervaT, all grows

* Rocky Mountains Park of Canada, on the Cana-dian Pacific Railway.

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under flowing water at various tempera-tures, some said to be as high as 740 Cent.We cannot doubt but that some such con-fervae, if sown or planted in a, rivulet orpool of warm water in the early years oftlhe first century of the solid earth's history,and, if favored with sunlight, would havelived, and grown, and multiplied, and wouldhave made a beginning of oxygen in the air,if there had been none of it before theircontributions. Before the end of the cen-tury, if sun-heat, and sunlight, and rain-fall were suitable, the whole earth not underwater must have been fitted for all kinds ofland plants which do not require much orany oxygen in the air, and which can find,or make, place and soil for their roots onthe rocks on which they grow; and thelakes or oceans formed by that time muisthave been quite fitted for the life of manyor all of the species of water plants livingon the earth at the present time. Themioderate warming, both of land and water,by underground heat, towards the end ofcentury, would probably be favorable ratherthan adverse to vegetation, and therecan be no doubt but that if abundance ofseeds of all species of the present day hadbeen scattered over the earth at that timean important proportion of them would havelived and multiplied by natural selectionof the places where they could best thrive.

§ 42. But if there was no free oxygen inin the primitive atmosphere or primitivewater several thousands, possibly hundredsof thousands, of years must pass beforeoxygen enough for supporting animal life,as we now know it, was produced. Evenif the average activity of vegetable growthon land and in water over the whole earthwas, in those early times, as great in re-spect to evolution of oxygen as that of aHessian forest, as estimated by Liebig* 50

* Liebig, 'Chemistry in its application to Agricul-ture and Physiology.' English, 2d ed., edited byPlayfair, 1842.

years ago, or of a cultivated English hay-field of the present day, a very improbablesupposition, and if there were no decay(eremacausis, or gradual recombination withoxygen) of the plants or of portions, suchas leaves falling from plants, the rate ofevolution of oxygen, reckoned as threetimes the weight of the wood or the dryhay produced, would be only about 6 tonsper English acre per annum or 1 1 tons persquare meter per thousand years. At thisrate it would take only 1533 years, and,therefore, in reality a much longer timewould almost certainly be required, to pro-duce the 2.3 tons of oxygen which we haveat present resting on every square meter ofthe earth's surface, land and sea.* Butprobably quite a moderate number of hun-dred thousand years may have sufficed. Itis interesting, at all events, to remark that,at any time, the total amount of combus-tible material on the earth, in the form ofliving plants or their remains left dead,must have been just so much that to burnit all would take either the whole oxygenof the atmosphere or the excess of oxygenin the atmosphere at the time above that,if any, which there was in the beginning.This we can safely say, because we almostcertainly neglect nothing considerable incomparison with what we assert when wesay that the free oxygen of the earth's at-mosphere is augmented only by vegetationliberating it from carbonic acid anid water,in virtue of the power of sunlight, and isdiminished only by virtual burningt of the

* In our present atmosphere, in average conditionsof barometer and thermometer, we have, resting oneach squiare meter of the earth's surface, ten tonstotal weight, of whiclh 7.7 is nitrogen and 2.3 isoxygen.

t This 'virtual burning ' includes eremacausis ofdecay of vegetable matter, if there is any eremacausisof decay without the intervention of microbes orother animals. It also includes the combination of aportion of the food with inhaled oxygen in the regu-lar animal economy of provision for heat and power.

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vegetable matter thus produced. But itseems improbable that the average of thewhole earth-dry land and sea bottom-contains at present coal, or wood, or oil, orfuel of any kind, originating in vegetation,to so great an amount as .767 of a, ton persquare meter of suirface; which is theamount, at the rate of one ton of fuel tothree tons of oxygen, that would be re-quired to produce the 2.3 tons of oxygenper square meter of surface which ourpresent atmosphere contains. Hence itseems probable that the earth's primitiveatmosphere must have contained free oxy-gen.

§ 43. Whatever may have been the truehistory of our atmosphere it seems certainthat if sunlight was ready the earth wasready, both for vegetable and animal life,if not withini a century, at all events withina few hundred centuries, after the rockyconsolidation of its surface. But was thesun ready? The well-founded dynamicaltheory of the sun's heat carefully workedout and discussed by Helmholtz, Newcomband myself,* says NO if the consolidationof the earth took place as long as 50 millionyears; the solid earth must in that casehave waited 20 or 50 million years for thesun to be anything nearly as warm as he isat present. If the consolidation of theearth was finished 20 or 25 million yearsago the sun was probably ready, thoughprobably not then quite so warm as atpresent, yet warm enough to support somekind of vegetable and animal life on theearth.

§44. My task has been rigorously con-fined to what, humanly speaking, we maycall the fortuitous concourse of atoms, inthe preparation of the earth as an abodefitted for life, except in so far as I have re-ferred to vegetation, as possibly havingbeen concer:ned in the preparation of an

*See ' Popular Lectures and Addresses,' Vol. I.,pp. 376-429, particularly page 397.

atmosphere suitable for animal life as wenow have it. Mathematics and dynamicsfail us when we contemplate the earth,fitted for life but lifeless, and try to imaginethe commencement of life upon it. Thiscertainly did not take place by any actionof chemistry, or electricity, or crystallinegrouping of molecules under the influenceof force, or by any possible kind of fortui-tous concourse of atoms. We must pause,face to face with the mystery and miracle ofthe creation of living creatures.

ADDENDUM.-MAY, Is8s.

Since this lecture was delivered I havereceived from Professor Roberts-Austenthe following results of experiments on themelting-points of rocks which he has kindlymade at my request:

Melting-point. Error.

Felspar ....... 15200 C. .4-300Hornblende...... about 14000Mica ....... 14400 -V..300Quartz ....... 17750 ±.4.150Basalt....... about 8800

These results are in conformity with whatI have said in §§ 26-28 on the probableorigin of granite and basalt, as they showthat basalt melts at a much lower tempera-ture than felspar, hornblende, mica orquartz, the crystalline ingredients ofgranite.In the electrolytic process for producingaluminium, now practiced by the BritishAluminium Company at their Foyers works,altumina, of which,the melting-point is cer-tainly above 17000 C. or 18000 C., is dis-solved in a bath of melted cryolite at a tem-perature of about 8000 C. So we mayimagine melted basalt to be a solvent forfelspar, hornblende, mica and quartz attemperatures much below their own sepa-rate melting-points; and we can understandhow the basaltic rocks of the earth may haveresulted from the solidification of the motherliquor from which the crystalline ingre-dients of granite have been deposited.

KELVIN.

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