ASSOCIATED GLACIAL LAKES. 255 



has explored and named Lake Dakota. Farther to the northwest the 

 glacial Lakes Souris and Saskatchewan were tributarj' to Lake Agassiz, and 

 had a most interestino- histoi-y in their changes of outlets and relationship 

 to the Sheyenne, Pembina, and Assiniboine deltas of this lake. PI. Ill, in 

 Chapter I, shows on a small scale the position and extent of the glacial 

 Lakes Minnesota, Dakota, Souris, and Saskatchewan, with their relationship 

 to Lake Agassiz. 



Even beyond the present continental watershed which divides the trib- 

 utaries of Hudson Bay from those of the Arctic Ocean, glacial lakes cover- 

 ing large areas now drained to the Mackenzie flowed into Lake Agassiz, 

 and portions of the courses of their outlets have been discovered. The 

 recession of the ice-sheet iipon all the country from Quebec to the Peace 

 River pent up vast lakes in front of its steep and high barrier, until the 

 present lines of drainage along the slopes of the land were opened and the 

 Glacial and Champlain epochs were ended. 



THE LAURENTIAN LAKES. 



This term, which is a synonym for the five great lakes, Superior, 

 Huron, with Georgian Bay, Michigan, Erie, and Ontario, outflowing- by 

 the River St. Lawrence, may also include the smaller Lake Champlain, 

 tributary to the St. Lawrence by the River Sorel or Richelieu. Dui'ing 

 the earlier stages of the glacial recession many small lakes were formed 

 along the northern side of the great watershed that separates the Missis- 

 sippi, Ohio, Susquehanna, Delaware, Hudson, and Connecticut rivers from 

 the St. Lawrence, with outflows to the south across each principal depres- 

 sion in the southern rim of the St. Lawrence basin. But at length, as the 

 ice further retreated, these became merged into a few large glacial lakes, 

 the precursors of the present great lakes of om- northern frontier. Finally 

 there existed in succession two of these bodies of water, eacli much larger 

 than Lake Superior, but smaller than Lake Agassiz, which more especially 

 claim attention. They have been named by Prof. J. W. Spencer Lake 

 WaiTen and Lake Iroquois.^ 



' Proc. A. A. A. S., Vol. XXXVII, for 1888, pp. 197-199. " The Iroquois beach : .a chapter in the geo- 

 logical history of Lake Ontario,'' Traus. Royal Society of Canada, Vol. VII, sec. 4, 1889, pp. 121-134, 

 with map; and "The deformation of Iroquois beach and birth of Lake Ontario," Am. Jour. Sci. (3), 

 Vol. XL, pp. 443-151, Dec, 1890. 



