POST-GLACIAL LAKES IN CANADA 



339 



From a perusal of -Tyrrell's report it is possible to outline at 

 least one main drainage channel of the great post-glacial lakes that 

 is of particular importance to our problem. 



Fig. I. — Map of portion of Mackenzie River basin, showing lower portions of 

 Peace and Athabaska river valleys and basins of Athabaska Lake and Great Slave 

 Lake. Scale, i inch = 117 miles. 



This channel appears to connect with the Clearwater River 

 valley at Methy portage, following it southeast through Buffalo 

 Lake, Isle la Crosse Lake, Beaver River, Green Lake, Big River, and 

 Shell Creek to the valley of the Saskatchewan. It is reported as a 

 broad, trenchlike valley with the watershed between the Saskatche- 



