442 THE GLACIAL LAKE AGASSIZ. 



total depths of 30 to 40 feet, obtaining water in gravelly seams, from which 

 it usually rises 10 to '20 feet within a few hours, to its permianent level. 



East and north of Duck Mountain l)eaches of the McCauleyville stages 

 are shown as follows bv !Mr. Tvrrell's map, according to my con-elation with 

 these shores southward in Manitolia and North Dakota: 



On the Vermilion River, which flows from the northeastern flank of 

 Riding- Mountain to Lake Dauphin, the beach ridges of two of these stages 

 are mapped, the elevation of the lower one being noted as 1,068 feet above 

 the sea. Twelve miles to the northwest their elevations ai-e 1,084 and 

 1,075 feet, at the north side of the Valley River, which flows from the gap 

 between the Riding and Duck mountains. Both these beaches are probably 

 represented b^' the upjjer shore-line farther south. 



The higher l)each was followed by Mr. Tp-rell 20 miles thence north 

 to the Shanty Creek, but without further notation of its height. About 20 

 miles farther nortli, near the south side of Pine River, it is found at 1,17.') 

 feet. Fifteen miles onward, at latitude 52°, close south of Duck River, 

 the upper McCauley\411e beach is 1,201 feet above the sea, having thus an 

 ascent of 117 feet in its com-se of 55 miles from the Valley River. Three 

 miles beyond the Duck River Avhere it turns sharply westward, adjacent to 

 the base of the northeastern angle of Duck Mountain, its height is 1,198 

 feet. After a course of a few miles to the west the beach ridge of this 

 shore, or the foot of its eroded escai-pment, was followed along the next 15 

 miles west-southwesterly, at the base of the steep mountain slope, by the 

 original location survey for the Canadian Pacific Railway. 



Cur^-ing thence again to the north, this upper McCauleyville shore- 

 line, where it crosses the Swan River, about 30 miles west of its crossing 

 of the Duck River, is marked bv a prominent gravel ridge or embaidvment 

 known as the "Square Plain," 1,1 GO feet above the sea. It is thus shown 

 that the former lake level has now an ascent here of a little more than a 

 foot per mile fi'oin west to east, or about half of its rate of ascent from 

 south to north in this district. The direction of the differential uplift, as in 

 the southern part of the lake area, was from south-southwest to north- 

 northeast, toward the I'egion on which the ice-sheet had been thickest and 

 where it lingered latest as the barrier of Lake Agassiz. 



