166 THE GLACIAL LAKE AGASSIZ. 



10 feet above adjoiuing depressions, remarkably in contrast with the very 

 flat surface of hxcustrine and chiefly alluvial clay and fine silt, containing 

 no gravel or bowlders, which elsewhere is the axial lowest portion of this 

 valley plain, continuous, excepting on this belt, from Breckenridge and 

 McCauleyville to Winnipeg, with widths on each side of the river varying 

 from a few miles to 15 or 20 miles. 



The belt of till here stretching from east to west across the valley has 

 a minimum breadth of about 10 miles, and probably comprises the mar- 

 ginal accumulations of the ice-sheet during its stages recorded by both the 

 Fergus Falls and Leaf Hills moraines. In the massive Leaf Hills and 

 again on the south side of Devils Lake these moraines are merged together; 

 and such a compound moraine appears also to have been amassed by the 

 ice-front in the deepest part of the bordering glacial lake. Upon this 

 broad tract the till deposited in Lake Agassiz rises 50 to 75 feet above the 

 top of the till along the center of the valley on the south and north, where 

 it has been overlain by later stratified silt. The moraine was not covered 

 by lacustrine silt, which is very scanty thi-oughout the lake area, excepting 

 where great rivers brought in gravel and sand deltas and more widely 

 spread fine silt deposits of modified drift derived from the retreating ice- 

 sheet. Neither, on account of its height, has it become covered, subseqiient 

 to the withdrawal of the lake, by the alluvium of the Red River and its 

 tributaries, although this sedimentation has filled the valley both above and 

 below almost to the height of the morainic belt. 



Where the Red River cuts through this area of till its channel is 

 obstructed by many bowlders, which form the Goose Rapids, 12 miles long 

 in the winding course of the stream, next below the mouths of the Goose 

 and Marsh rivers. The descent of the Red River along the rapids and 

 onward to Belmont, a distance of 12 miles in due-north course, but about 

 twice as far by the meanderings of the river, is 24 feet in its stage of 

 lowest Avater, but only 14 feet in its highest floods. The plane of extreme 

 high water rises 40 feet above the extreme low stage at the head of the 

 rapids^ and nearly as much all the way from Fargo and Moorhead to Win- 

 nipeg; but at Belmont, close below the foot of the rapids, the floods attain 

 their greatest range in the entire valley, 50 feet. 



