MAXIMUM ASCENT NOETH-NOETHEASTWAED. 485 



as much per mile as the ascent toward the north. The rate of ascent east- 

 ward also increases, like that northward, in proceeding from south to north. 

 At the latitude of Wahpeton and Breckenridge, 35 miles north from the 

 mouth of Lake Agassiz, the ascent of its highest stage is 10 feet from west 

 to east in 45 miles; at the latitude of Fargo and Moorhead, 75 miles north 

 from the outlet, it is 15 feet in 50 miles; and at the latitude of Grand 

 Forks, 150 miles north from the outlet, it is 33 feet in 70 miles. 



RATE OF ASCENT GREATEST TOWARD THE NORTH-NORTHEAST. 



These observations that the corresponding beaches are higher on the 

 east than on the west side of the lake, taken in connection with the doubly 

 more rapid northward ascent of the west and east shores, indicate that the 

 changes in the relations of the land and surfaces of level during the exist- 

 ence of Lake Agassiz and tlu-ough subsequent time have given to the 

 former levels of this glacial lake a niaximum ascent from south-southwest 

 to north-northeast, its rate in tliis direction being somewhat greater than 

 that noted in following the shores in their nearly due-north course. The 

 maxinmm rates of nttrthward ascent of about 1 foot per mile observed in 

 North Dakota and southern Manitoba, and of 1 foot to 16 inches per mile 

 in Minnesota, therefore l)elong to a lake level which in its northern por- 

 tion, within the limits of my exploration, differs from the present level by 

 an ascent of approximately IJ feet per mile toward the north-northeast. 

 Similar north-northeastward ascent continues through the successive lower 

 stages of the lake, in which its amount in southern Manitoba, between the 

 international boundary and Gladstone, is reduced to about 4 inches per 

 mile at the lowest stage of southward outflow; and it is scarcely 1 inch 

 per mile in the Niverville beaches along their whole ob.served extent of 

 about 260 miles from Morris, Manitoba, north to the mouth of the Sas- 

 katchewan. No more than 20 feet of differential northward uplift has 

 taken place within this distance since the course of the Nelson River was 

 uncovered by the receding ice-sheet. 



Preliminary descriptions and discussions of the uplifting of this basin 

 which have been given in the chapter on the history of Lake Agassiz 



