44 



THE ORIGIN AND EVOLUTION OF LIFE 



The following are among the reasons why the primordial 

 solar influences upon the earth may have differed from the 

 present solar influences. It appears probable that the lifeless 

 surface of the primordial earth was like that of the moon — 

 covered not only with igneous rocks but with piles of heat-stor- 



HEAT LIGJ 



Billion vibratijlds per secondnn/^^ 



CHEMrC4L 



WIRA VIOLET 



Fig. 3. Light, Heat, and Chemical Influence of the Sun. 



Diagram showing how the increase, maximum, and decrease of heat, Hght, and chemical 

 energy derived from the sun correspond to the velocity of the vibrations. After Ulric 

 Dahlgren. 



ing debris, as recently described by Russell ^ — and if, like the 

 moon, the earth had had no atmosphere, then the reflecting 

 power of its surface would have represented a loss of only 40 

 per cent of the sun's heat. But a large amount of aqueous 

 vapor and of carbon dioxide in the primordial atmosphere prob- 

 ably served to form an atmospheric blanket which inhibited 

 the radiation from the earth's surface of such solar heat as pen- 

 etrated to it, and also prevented excessive changes of temper- 

 ature. Thus there was on the primal earth a greater reg- 

 ularity of the sun's heat-supply, with more moisture. 



J Russell, H. N., 1916, p. 75. 



