214 SECRETS OF ANIMAL LIFE 



inquire how the callous, rough-and-tumble condi- 

 tions of the outer world allowed of the germination 

 and growth of that tender plant which we call life. 

 In this inquiry we shall chiefly follow the con- 

 siderations recently brought forward by Professor 

 Chamberlin in his Origin of the Earth (Chicago 

 University Press, 1916), and by Professor Hender- 

 son in his Order of Nature (Harvard University 

 Press, 1917). 



Around the young earth, more or less cooled 

 down, there was wrapped an atmosphere, laden with 

 " planetesimal " dust which sank gently on to the 

 surface and drifted about in billowy, changeful 

 dunes. By its early "ultra-Krakatoan " atmo- 

 sphere, as Professor Chamberlin calls it, " the 

 young earth was blanketed against intensities of 

 radiance from without " (a younger, more intensely 

 radiant sun) "and inequalities of radiance from 

 within." This " preparation " afforded by the 

 atmosphere was probably of great importance, 

 for the average living creature, as we know it, is 

 adapted to mild temperatures and gentle reactions 

 and ill suited for violent vicissitudes. Time passed, 

 and from the growing atmosphere water condensed 

 on the surface of the earth, and was gradually 

 absorbed by the porous, dusty mantle, till by and 

 by in the hollows among the dunes there appeared 

 pools and lakelets, from which grew lakes and seas. 

 To an atmosphere was added a second "prepara- 

 tion," a hydrosphere, and that brought the possi- 

 bility of life nearer. 



