654 



HISTORICAL GEOLOGY 



Fig. 570. — In this {fourth) stage the Great Lakes had their greatest area, forming 

 Lake Algonquin. The outlets were the Mohawk and Illinois rivers. (Modified after 

 Taylor and Leverett.) 



FlG. 1571. — A (fifth) stage with the drainage through the Ottawa River. A low- 

 ering of the region resulted in the extension of the sea into the St. Lawrence valley 

 and Lake Champlain. (After Taylor and Leverett.) 



