DRAINAGE SYSTEMS AND THE GLACIAL PERIOD. 225 



able gorge joining the Minnesota with the Red River of 

 the North, we are brought to the largest of the glacial 

 lakes of this class, and to the typical place in America in 

 which to study the temporary changes of drainage pro- 



Fig. 58.— Map showing the stages of recession of the ice in Minnesota as 

 described In the text (Uphamj. 



duced by the ice itself daring the periods both of its ad- 

 vance and of its retreat. 



By turning to our general map of the glaciated region 

 16 . 



