Page:The Journal of geology (IA journalofgeology21894univers).pdf/409

the whole uplift of the northern part of the basin was accomplished, however, while the ice-sheet was still a barrier of the lake, for the Niverville beach at the Grand Rapids of the Saskatchewan 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 Niverville beaches. The rise of the land approximately to its present 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 submergence.^[1] 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 epeirogenic uplift of our continent from its Champlain depression, the whole area of Lake Agassiz, as shown by the still horizontal