NOETHWAED ASCENT OF THE BEACHES. 479 



more than 300 miles from Lake Traverse to the south ends of Lakes Mani- 

 toba and Winnipeg. The whole descent, on the latitude of Gladstone, 

 between the lowest McCauleyville beach, where Lake Agassiz ceased to 

 outflow southward, and the original level of Lake Winnipeg, about 20 feet 

 above the present surface of that lake, is about 280 feet, of which probably 

 25 or 30 feet may be due to the northward rise of the land and diminution 

 of gravitation toward the ice-sheet, while about 250 feet are due to the 

 gradual lowering of Lake Agassiz by its successive northeastern outlets. 



The depth of Lake Agassiz above the present surface of the south end 

 of Lake Winnipeg was about 600 feet during its higher Herman stages, 500 

 feet at the upper Norcross stage, 440 feet at the iipper Tintah stage, 370 feet 

 at the upper Campbell stage, and 325 and 300 feet in the upper and lower 

 McCauley^^lle stages, being thus reduced to half of its earlier depth before 

 it ceased to flow to the south. During the lower stages of outflow to the 

 northeast the depth of Lake Agassiz above Lake Winnipeg decreased to 

 285 feet at the upper Blanchard stage, about 240 feet at the time of the 

 Hillsboro beach, 210 feet in the Emerado stage, and successively about 185, 

 165, 145, 130, 110, and 65 feet in the Ojata, Gladstone, Burnside, Ossowa, 

 Stonewall, and Niverville stages. 



The greatest expansion of Lake Agassiz was perhaps reached Ijefore 

 the Herman series of beaches was completed, and it apparently was main- 

 tained during the greater part of the time of outflow by the River WaiTcn; 

 but through the successive stages of outflow northeastward the lake was 

 diminished in area liy nearlv proportionate gradations as its depth decreased. 

 When it began to flow in this direction it probably still occupied about 

 half of its area that was attained during the formation of the Herman and 

 Norcross beaches; but, in compensation for loss on its Avestern and southern 

 borders, it may have received meanwhile as great addition by growth 

 toward the north and northeast, thus retaining, until it ceased to outflow at 

 Lake Traverse, nearly its niaximum extent. 



Beyond the limits of my leveling, portions of nearly all the shore-lines 

 of Lake Agassiz below those of the Herman series have been oliserved by 

 Mr. J. B. Tp-rell, of the Canadian Geological Survey, at localities in north- 

 western Manitoba and eastern Saskatchewan. From a careful comparison 



