Junk 30, 1899. ] 



iiCIENCE. 



893 



whether the reasons for that abandoument 

 do not bear adversely also on this modified 

 phase of the gaseous hypothesis. The 

 strongest objection recently urged against 

 the Laplacean gaseous ring is the apparent 

 inabilitj' of the feeble gravity of such a ring 

 to overcome the high molecular velocities 

 of its lighter constituents at the high tem- 

 peratures necessary to maintain the refrac- 

 tory material of the earth in a gaseous con- 

 dition.* In addition to this radical objec- 

 tion to the gaseous earth- moon ring, there 

 is the extreme probability that, if formed, it 

 would cool below the temperature of 

 volatilization of rock substance before it 

 would concentrate into a globe. 



The studies to which reference has just 

 been made seemed to show that even in the 

 globular form it is doubtful if the earth 

 could be volatilized without the dissociation 

 of its water and the loss of its hydrogen by 

 molecular projection away from the earth. 

 The inquiry seemed even to raise a doubt 

 whether the vapor of water, as such, or the 

 atmospheric gases could be retained at the 

 temperature of rock volatilization ; indeed, 

 it seemed that the oceanic and atmospheric 

 constituents might even be in jeopardy at 

 the temperature of white-hot lava. With- 

 out insisting that these molecular inquiries 

 are demonstrative — for they only profess 

 to be preliminai'j' — they seem, at least, to 

 justify the radical inquiry whether the 

 hypothesis that the earth was once a 

 gaseous nebula can be entertained with any 

 confidence, in the light of modern molecular 

 physics. As an abstract proposition in 

 physics addressed to physicists would Lord 

 Kelvin feel free to assert that the water 

 now on the surface of the earth would be 

 retained within its gravitative control if the 

 earth were heated so that its rock substance 

 was volatilized ? Maj- I be pardoned for 



* A Group of Hypotheses bearing on Climatic 

 Changes. Jour. GeoL, Vol. V., No. 7, Oct. -Nov., 

 1897, pp. 658-668. 



inquiring whether Lord Kelvin has not 

 joined the company of geologists and ne- 

 glected some of the physical considerations 

 that bear pertinently on the problem in 

 hand ? 



But passing this point, and striking 

 hands with Lord Kelvin in assuming " the 

 almost certain truth that the earth was 

 built up of meteorites falling together," 

 what imperative reason is there for infer- 

 ring a gaseous or even a white-hot liquid 

 condition as a result? It goes without say- 

 ing that the energy of impact of the fall- 

 ing meteorites would be sufficient, under 

 assumable conditions, to give rise to the 

 liquid condition and much more, but the 

 actual condition that would be assumed by 

 the earth would be dependent wholly on 

 the rate at which the meteorites fell in. If they 

 fell in simultaneously from assumable dis- 

 tances an intensely hot condition may be 

 predicated with all the confidence of logical 

 certitude. If they fell at as great intervals 

 as they do to-day a low surface temper- 

 ature may be predicated with equal cer- 

 tainty. If they fell in at some intermedi- 

 ate rate an intermediate thermal state of 

 the surface must be postulated. No phys- 

 ical deduction can be more firm than that 

 the temperature of the surface of the earth 

 would be rigorously dependent on the rate 

 of infall so far as the influence of infall 

 alone is concerned. Before a white-hot 

 condition can be regarded as a safe assump- 

 tion it must be shown that the meteoroids 

 would necessarily fall together at a highly 

 rapid rate; otherwise the heat of individual 

 impacts would be lost concurrently, as is 

 now the case, and would not lead to gen- 

 eral high temperature. 



Now, has Lord Kelvin, or any other of 

 our great teachers in physics or in astron- 

 omy, followed out to a final conclusion, by 

 the rigorous processes of mathematics, the 

 method and rate of aggregation of a multi- 

 tude of meteorites into a planet, so as to be 



