NE-SAW-JE-WON 



FIGURE 2.— GLACIAL MAP OF NORTH AMERICA 



SHOWING THE MAXIMUM EXTENT OF THE ICE SHEETS AND THE SEVERAL 

 CENTERS OF ICE ACCUMULATION. 



From U. S. Geological Survey. 



The Glacial Period and Its Records 

 During early Pleistocene time, in the highlands about Hud- 

 son Bay snow accumulated throughout hundreds of years 

 and became packed to ice so thick that it pushed outward by 



20 



