534 THE ICE AGE m NORTE AMERICA. 



the radiation of the sun's heat was so intense that life must 

 have been impossible upon our globe. 



But he who pauses to reflect upon how long a period one 

 million years is, and takes the pains to multiply the annual 

 changes of the present time by that number, will not feel 

 cramped by the limits which astronomers are now setting to 

 geological time. In this general shortening of our concep- 

 tion of geological periods, the evolutionists also find no small 

 relief in the more moderate estimates made concerning the 

 date of the close of the Glacial period ; for it is very clear 

 that the changes in species since the great Ice age are tritling. 

 The flora and fauna of the world during the Glacial period 

 were essentially the same as those of the present time. Even 

 man is believed to have been an inhabitant of America, as 

 well as of Europe, before the ice had withdrawn from the 

 head- waters of the Delaware River, and from the mountains 

 of Scotland and the north of England. If these changes in 

 the organic world have been so slight since the Glacial epoch, 

 it follows that, the further back that period is placed in time, 

 the greater are the difficulties of the evolutionists. The 

 more the evolutionists are limited in time by the astrono- 

 mers, the more do they need a rapid rate of change as the 

 basis of their calculations. If, therefore, the Glacial period 

 should prove to have ended only ten thousand years ago in- 

 stead of seventy thousand, the Darwinian would be relieved 

 from no small embarrassment. Thus, so far as there is likely 

 to be any odium theologicum in the case, the desire to sup- 

 port a short biblical chronology and the counter-desire to dis- 

 credit Darwinism, and vice versa, may be left to counteract 

 each other. 



In view of the doubt expressed in the preceding chapter 

 concerning Mr. Croll's theory, it does not seem proper for 

 geologists to rest satisfied with mere astronomical calcula- 

 tions respecting glacial chronology. We may, therefore, be 

 permitted to turn to the more congenial task of considering 

 the direct geological evidence bearing on the question. In 

 this field there are three classes of facts to which we can 



