20 THE GLACIAL LAKE AGASSIZ. 



of Lake Traverse. There the country sinks o-radually to a level not much 

 above the small Bois ties Sioux River, which is the outlet of Lake Traverse, 

 flowing- north 35 miles and emptying into the Red River of the North at 

 Breckenridge and Wahpeton. The Red River, here turning abruptly from 

 its western course, iiows thence north to Lake Winnipeg, 285 miles. These 

 streams occupy the axial depression of a vast plain of glacial drift and 

 lacustrine and fluvial deposits, 40 to 50 miles wide and more than 300 

 miles long, stretching from Lake Traverse to Lake Winnipeg. This 

 expanse, widely famed for the large harvests and superior quality of its 

 wheat, is commonly called the Red River Valley. It has a very uniform 

 continuous descent northward, averaging a little less than 1 foot pei- mile. 

 So slight an inclination is imperceptible to the eye, as is also the more 

 consi<lerable ascent, usually 2 or 3 feet per mile, for the first 10 or 15 miles 

 to the east and west from the Red River. This river flows along the lowest 

 portion of the plain, somewhat east of its central line, in a quite direct 

 general course from south to north, but meanders almost everywhere with 

 minor bends, which carry it alternately a half mile to 1 mile or more to 

 each side of its main course. Thus its length from Breckemddge and 

 Wahpeton to St. Vincent and Pembina, forming the boundary between 

 Minnesota and North Dakota, is 397 miles, according to the surveys of the 

 United States Engineer Corps, while the distance in a direct line is only 

 186 miles; vet the river nowhere deviates more than 5 or 6 miles from this 

 straight line. 



The Red River has cut a channel 20 to 50 feet deep. It is bordered 

 bv only few and narrow areas of bottom-land, instead of wliich its banks 

 usually rise steeply on one side and by nn>derate slopes on the other to the 

 lacustrine plain, which thence reaches nearly level 10 to 30 miles from the 

 river. Its tributaries cross the plain in similar channels, which, as also 

 the Red River, have occasional gullies connected with them, dry through 

 the most of the year, varying from a few hundred feet to a mile or more 

 in length. Between the drainage lines areas often 5 to 15 miles wide 

 remain unmarked by any water courses. The highest portions of these 

 tracts are connnonly from 2 to 5 feet above the lowest. The material of 

 the lower ])art of this valley plain, shown in the banks of the Red River 



