5 8o SCIENCE PROGRESS 



evidence of a fresh-water ocean such as some geologists have 

 imagined. 1 



If a considerably higher temperature prevailed, the atmo- 

 sphere would have contained much more water vapour than at 

 present, and there would have been a much greater cloud forma- 

 tion. 2 A variety of evidence goes to show that the primeval 

 atmosphere was devoid of free oxygen, 3 and it may have 

 contained much more hydrogen than the present. But in the 

 light of recent physical investigations it seems certain that the 

 old idea of an enormously greater quantity of carbon dioxide 

 has no probability in fact. 4 Any additions of carbon dioxide 

 would have been largely absorbed by the ocean, and beyond a 

 certain point this dissolved carbon dioxide would have been 

 precipitated in the form of carbonates. 



If we adhere to the old idea of igneous origins, the vast 

 quantities of carbon contained in the rocks would have been 

 combined as carbides, metallic or silicious, as the researches of 

 Moissan, 5 Gautier, and Brun have pretty clearly demonstrated ; 

 and carbon dioxide would have been evolved gradually through 

 volcanic action, as at the present time. On the other hand, 

 if we conceive of a slowly growing earth, the atmosphere, 

 including carbon dioxide, was slowly evolved through the 

 extrusion of the gases occluded in the falling meteors. Originally 

 the quantity of atmosphere would necessarily have been small, 

 and it would have attained its present proportion only through 

 a slow growth. 6 



Again, in the light of present physical theories, we must 

 conceive that if the earth condensed from a gaseous mass, the 

 time elapsing between the first formation of a hot crust, and 

 the cooling of this to something like the present temperature, 

 would not have been long. 7 A solid crust would have formed at 

 somewhere not very far from iooo C, and, according to Kelvin 

 and Arrhenius, the time required to cool this mass to below 



1 Cf. Joly, Proc. R. S. Dub. 7, 23, 1899. 



2 Cf. Manson, Climat des Temps gcologiques, 1906. 



3 Stevenson, Phil. Mag. 50, 312, 1900 ; Kelvin, ibid. 47, 66, 1899. 



4 Tolman,/0«r«. of Geol. 7, 585, 1899. 



5 Proc. Roy. Soc. 60, 166, 1896; Brun, I.e.; Gautier, Ann. d. Mines, 9, 316, 

 1906. 



6 Cf. Chamberlin, Journ. of Geol., vols. 5, 6, 7 ; McKee, Science, 23, 271, 1906 ; 

 Clarke, Data of Geochemistry, 49, 1908. 



7 Arrhenius, I.e. p. 36 ; Kelvin, I.e. 



