436 THE CANADIAN NATURALIST. [Vol. X. 



ON THE FORMER SOUTHWARD DISCHARGE OF 



LAKE WINNIPEG. 



By J. D. Dana. 



The most remarkable of the chanaes that are known to have 

 occurred in the water-courses of North America is that in the 

 discharge of Lake Winnipeg from a former southward course by 

 the Minnesota Channel and Mississippi to its modern discharge 

 into Hudson's Bay, first announced and sustained by General G. 

 K. Warren, in a report of 18G7, published in a Report of the 

 U. S. Engineers for the year 1868 (pp. 807-31i), after levellings 

 along these rivers, by order of the Government, in 1866 and 

 1867. The question was more fully illustrated by General 

 Warren in ''an Essay concerning important physical features 

 exhibited in the Valle}" of the Minnesota River and upon their 

 signification," submitted to the Chief of Engineers in 1874, and 

 published in the Report for 1875 (pp. 385-402) ; and afterward, 

 further discussed by him in his paper on the Bridging of the 

 Upper Mississippi, in the Report for 1878 (pp. 909 to 926) with 

 a reproduction of some of the maps of the essay of 1874. 



In the first of his papers, that of January, 1867, General 

 Warren, after mentioning the evidences that " Lake Winnipeg 

 was once continuous southward over the central [lortion of the 

 Red River of the North, and had its outlet down the Minnesota, 

 and not down the Nelson to Hudson's Bay " (pp. 307), considers 

 the origin of the former hydrographical conditions. He speaks 

 of the possibility of an ice-barrier in the north in the Glacial 

 era ; but he sets this idea aside, and argues for an actual change 

 of land-level, and makes the southward discharge to have ended 

 in consequence of a depression of land to the south, accompany- 

 ing (as added in his paper of 1875) a rise to the north ; and 

 instancing, as examples of a corresponding change of level, the 

 former southward discharge of Michigan Lake through the Illi- 

 nois River, and of Winnebago Lake through the Wisconsin 

 River. A map of the large Winnipeg Lake — larger he observes 

 than Lake Superior and Michigan together, and having the 

 Saskatchewan River as the head stream — accompanied the written 

 report sent to the Department, but it was not published. The 

 same view is presented at more length in the paper of 1874 

 (Report for 1875), along with a wider discussion of the facts, 



