STAGES OF GROWTH SHOWK BY MOKAINES. 215 



700 miles. Delta sand deposits, brought into Lake Ag-assiz by the Sas- 

 katchewan and referal)le to the Herman, Norcross, and later stages, reach 

 from near Prince Albert, on the North Saskatchewan, about 40 miles west 

 of the fork of the North and South branches, through a distance of more 

 than 100 miles eastward to the head of the Seepanock Channel and the 

 one hundred and third meridian/ The descent of the river in this distance 

 is approximately from 1,275 or 1,300 feet to 950 feet, and the elevation of 

 the west part of the delta is about 1,350 to 1,400 feet above the sea. As 

 early as the time of the lower beaches of the Herman series, therefore, the 

 recession of the ice-sheet had permitted the lake to extend along the whole 

 front of the Manitoba escarpment to the latitude of the north end of Lake 

 Winnipeg. The length of Lake Agassiz at that time was 550 miles or 

 more, and I believe that its average width was not less than 150 miles, 

 reaching- east to the moraine which Mr. J. B. Tyrrell describes as forming 

 the eastern shores and islands of Lake Winnipeg, with a height of 100 feet 

 on Black Island.^ This moraine would then have been deposited in water 

 600 to 700 feet deep, bordering the ice margin; its knoUy and irregular 

 accumulations of drift would not have been subjected to the leveling action 

 of the lake waves until the further melting of the ice opened avenues of 

 outflow to Hudson Bay and reduced the glacial lake nearly to the level of 

 Lake Winnipeg; and the latest change of the northward outlets may have 

 lowered the water surface so rapidly and to such vertical amount that it 

 left no distinct marks of erosion or shore-lines on the upper portion of the 

 moraine. 



Before the successive northeastward outlets began to drain Lake Agas- 

 siz below its channel of southward discharge at Lakes Traverse and Big 

 Stone, the border of the ice-sheet had been gradually melted back from 

 Lake Winnipeg doubtless far toward Hudson Bay, and perhaps even its 

 thick central part, which occupied the basin of Hudson and James bays, 

 had so far disappeared as to admit the sea there. At a time of halt or read- 

 vance, interrupting this recession, another terminal moraine appears to have 

 been accumulated, crossing the Churchill and Nelson rivers, as observed 



» Canadian Pacific Railway Report, 1880, pp. 14, 19. 



2 " Pleistocene of the Winnipeg Basin," Am. Geologist, Vol. VIII, pp. 19-28, July, 1891. 



