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THE NATIONAL GEOGRAPHIC MAGAZINE 



MAP OF NORTH AMERICA AT THE TIME OF MAXIMUM EXTENT OF THE ICE 



Showing also the approximate outh'ne of the continent. There were minor ice-centers, 

 not indicated, over most of the high mountain ranges of the west from which glaciers 

 descended the valleys and in some places deoloyed on the plains 



places by great ledges and loose blocks 

 readily dislodged by the least force. 



The climate over the whole continent 

 was semi-tropical, or at least temperate, 

 and such plants as the fig and great red- 

 woods of California grew as far north 

 as Greenland and Iceland. And through 

 the almost endless woods of the north 



roamed herds of mastodon and other 

 herbivore of great size, together with 

 such beasts of prey as the now extinct 

 saber-toothed tiger. But we would find 

 no trace of man. 



Over this strange and magnificent 

 world the Ice Age swept down so sud- 

 denly, as geologic time is reckoned, that 



