LAKE SOURIS. 



269 



300 to 450 feet deep, probably averaging 350 feet, along its last 25 miles. 

 It is cut tlu-ough the platean of Fort Pierre shale that reaches westward 

 from the Pembina Mountain escarpment. Outside of this valley the shale 

 is overlain by only a thin sheet of till, which varies generally from 10 to 

 30 or 40 feet in thickness; but the valley itself contains a considerably 

 greater depth of till. From Lakes Lome and Louise to its delta the Pem- 

 bina probably flows in its preglacial course, where its old valley became 

 partly filled with till during the Glacial period. The topographic features 

 of this valley will be more fully shown by the following notes of approxi- 

 mate elevations referred to the sea-level, those of the first column being 

 in the bottom of the valley, and those of the second along the top of its 

 bluff's at the general level of the adjoining country. 



Elevations along the Pembina Valley {outlet of Lake Souris). 



Distance 

 in miles 

 from the 

 elbow 

 of the 

 Souria. 



Feet .tbove 

 the sea for 

 bottom of 

 the valley 

 and surface 

 of water in 

 rivers and 

 lakes. 



Feet above 

 the sea for 

 t"p of the 

 bluffs in- 

 closing the 



Elbow of the Sonris, in a valley that has been eroded about 100 feet by the present 

 river flowing to the Assiniboine since the glacial Lake Souris ceased to outflow to 

 the Pembina by Langs Valley 



Divide in Langs Valley, near the line between sections 31 and 32, township 5, range 17, 

 Manitoba, separating Langs Creek, flowing west to the Souris. and Dunlops Creek, 

 flowing east to the Pembina, determined by railway survey 



Bone Lake, 3 miles long and a half mile wide 



Grass Lake 



Pelican Lake, 10 miles long and about a mile wide, mostly 10 to 15 feet deep, but in its 

 deepest portions about 20 feet, rising 3 feet between its lowest and highest stages . . 



Junction of outlet of Pelican Lake with the Pembina 



Lake Lome; area, about 1 mile square: maximum depth, about 8 feet 



Lake Louise, of nearly the same area and maximum depth 



Month of Badger Creek 



Kock Lake, 8 miles long and one-half to 1 mile wide; maximum depth, 10 feet' 



Mouth of Clearwater Kiver 



At the Marringhurst bridge, on the north line of section 16, township 3, range 12, 

 Manitoba 



Swan Lake. 5 miles long and 1 mile wide ; maximum depth, probably about 10 feet 



At La Kivi^re, determined by railway survey 



At crossing of the boundary commission road* 



At crossing of the old Missouri trail 



At the Mowbray bridge, on the line between sections 21 and 22, township 1, range 8, 

 Manitoba 



On the international boundary 



At the tish trap, sectiim 30, township 163, range 57, North Dakota, 2 miles west of the 

 Pembina Mountain escarpment and 7 miles west of "Walhalla 



5- 8 

 10-11 



11-21 



22i 



23-24 



25-26 



27 



1,364 

 1,357 

 1,355 



1,355 

 1,348 

 1,346 

 1,345 

 1.343 

 1,335 

 1,332 



1,330 

 1,310 

 1,287 

 1,265 

 1,250 



1,235 

 1,125 



1,050 



1,475 

 1,480 

 1,485 



1, 485-1, 510 

 1.510 

 1,510 

 1,510 

 1,510 



1, 510-1, 550 

 1,525 



1,480 

 1.500 

 1,550 

 1,550 

 1,545 



1,540 

 1,540 



1, 400-1, 500 



'Glenora prairie, north of Rock Lake, a slightly undulating expanse of modified drift, stratified gravel, and sand, 

 extending 6 miles from west to east and 2 to 3 miles wide, has an elevation of 1,510 to 1.500 feet, descending eastward with 

 the valley. 



'Dr. George M. Dawson notes a wide terrace here, in some places thickly strewn with bowlders, on the southwestern 

 Bide of the river and about 200 feet above it: and he refers its origin to preglacial erosion of the valley. 



