234 THE GLACIAL LAKE AGASSIZ. 



of observations of the bearings of g-lacial strine on all portions of Canada 

 to the far north, and examination of the lowest points of watersheds as to 

 their glacial river courses, will be the means of displacing these specula- 

 tions by definite knowledge and proofs of what were the fortunes of the 

 departing ice-sheet and of the late outlets of this lake.^ 



Amount of differential elevation between Lake Traverse and Gladstone. — 

 How the Red River Valley and the lake country of Manitoba were uplifted 

 from the late glacial or Chainplain dein-ession is told l)v the inclination of 

 the Lake Agassiz shore-lines. So far as exploration and determination 

 of the heights of the beaches have extended, including both my own and 

 Mr. Tyrrell's work, there is found to be a northward ascent of the old lake 

 levels, greatest in amount along the earlier and higher beaches, and dimin- 

 ishing almost to horizontality in the latest and lowest. Comparing the 

 lieights of the beaches at or near the mouth of the lake with their heights 

 about 300 miles to the north, on the latitude of Gladstone, which is near 

 the northern limit of my observations, it is seen that the epeirogenic uplift- 

 ing of this part of the lake liasin, increasing gTaduallv from south to north, 

 and the fall of the lake surface, also greatest at the north on account of the 

 decreasing effect of gravitation toward the diminishing and receding ice- 

 sheet, were together ajjproximately 265 feet in this distance, averaging 

 nearly 1 foot per mile, after the formation of the second Herman beach, 

 which is the highest found on that latitude. Of this combined uplift of the 

 land and fall of the lake, about 80 feet had taken place before the forma- 

 tion of the Norcross beach; 50 feet more before the upper Tintah beach; 

 about 45 feet more before the Campbell beach; and again some 25 feet 

 more before the McCauleyville beach; leaving only 65 feet of the whole 

 265 feet of changed level to take place after the lake began to outflow 

 northeastward, and it appears that all but about 20 feet of this remaining 

 change had been accomplished before the formation of the lowest or Niver- 

 ville beach. While the ice was departing from the country and still was 

 the barrier of the lake, this part of its basin was uplifted nearly to its 



' Since this paragraph was written the explorations of Mr. ,J. B. Tyrrell in the region from Lake 

 Athabasca northeast to the Chesterfield Inlet of Hudson Bay (Geol. Magazine. IV, Vol. I, pp. 394-399, 

 Sept., 1894) have given much support to this opiniim. See also Professor Chamberlin's map of the 

 North American ice-sheet, with indications of its centers and currents of outflow, in J. Geikie's Great 

 Ice Age, third ed., 1894, PI. XIV. 



