IVA VE-LIKE PROGRESS OF AN EPEIROGENIC UPLIFT. 393 



the whole uplift of the northern part of the basin was accom- 

 plished, however, while the ice-sheet was still a barrier of the 

 lake, for the Niverville beach at the Grand Rapids of the Sas- 

 katchewan is only slightly higher than on the Red river, 250 

 miles to the south. 



The southern and central part of the lake basin, reaching 

 north to Gladstone, had been raised nearly to its present height 

 during the first third or half of the period of the entire duration 

 of Lake Agassiz. Then followed a time, during the second 

 third of the lake's existence, in which the district that includes 

 Riding and Duck mountains and extends north to the mouth of 

 the Saskatchewan was being rapidly uplifted. But this later 

 northward and northeastward advance of the wave of upheaval 

 had passed beyond the Saskatchewan before Lake Agassiz was 

 lowered to Lake Winnipeg, as is shown by the nearly level Niv- 

 erville beaches. The rise of the land approximately to its pres- 

 ent height is thus known to have followed close upon the glacial 

 recession by which the land was relieved of the ice weight. 



Latest of all, when Lake Winnipeg and the Nelson river had 

 come into existence, the shores of Hudson and James bays were 

 raised 300 to 500 feet from their late glacial marine submer- 

 gence. ' The remnants of the ice-sheet in that region were not 

 melted away until much later than the glacial retreat from the 

 northern United States and Manitoba. Moving onward with the 

 departure of the ice, the uplifting wave of the earth's crust has 

 raised the basin of Hudson bay 300 to 500 feet since the sea 

 was admitted to it, and the upheaval there is not yet completed. 

 Though doubtless slower than at first, it is still in progress, 

 according to Dr. Bell's observations, at a probable rate of five to 

 seven feet per century. During this last portion of the epeiro- 

 genic uplift of our continent from its Champlain depression, the 

 whole area of Lake Agassiz, as shown by the still horizontal 



"■ Dr. Robert Bell, Geol. and Nat. Hist. Survey of Canada, Reports of Pro- 

 gress, for 1871-72, p. 112; for 1875-76, pp. 340; for 1877-78, pp. 7 and 32 C and 25 

 CC ; for 1878-79, p. 21 C; for 1882-84, pp. 26-32 DD; Annual Reports, new series, 

 Vol I. for 1885, p. II DD; Vol. 2, for 1886, pp. 27, 34, and 38 G. 



