18 THE GLACIAL LAKE AGASSIZ. 



above the sea, its ordinary stage being about 8 feet below that of Lake 

 Traverse; and the mouth of the Minnesota River at extreme low water is 

 688 feet above the sea, the descent from Big Stone Lake to the mouth of 

 the river being 274 feet. 



Lakes Traverse and Big Stone are from 1 to IJ miles wide, mainly 

 occupying the entire area between the bases of the bluffs, which rise about 

 125 feet above them. Lake Traverse (PI. V) is 15 miles long; it is mostly 

 less than 10 feet deep, and its greatest depth probably does not reach 20 

 feet. Big Stone Lake is 26 miles long, and its greatest depth is reported to 

 be from 15 to 30 feet. The portion of the channel between these lakes 

 is widely known as Browns Valley. As we stand upon the bluffs here, 

 looking down on these long and narrow lakes in their trough-like valley, 

 which extends across the 5 miles between them, where the basins of 

 Hudson Bay and the Gulf of Mexico are now di^^ded, we have nearly the 

 scene which was presented when the melting ice-sheet of British America 

 was pouring its floods along this hollow. Then the entire extent of the 

 valley was doubtless filled every sununer l)y a river Avhich covered all the 

 present arejis of flood plain, in many places occupying as great width as 

 these lakes. 



General WaiTen observed that Lake Traverse is due to partial silting 

 up of the channel since the outflow from the Red River basin ceased, the 

 Minnesota River at the south ha^dng' brought in sufficient alluvium to form 

 a dam; wliile Big Stone Lake is similarly referred to the sediment brought 

 into the valley just below it by the Whetstone River. Fifteen miles below 

 Big Stone Lake the Minnesota River flows through a marshy lake 4 miles 

 long and about a mile wide. This may be due to the accumulation of 

 alluvium brought into the valley by the Pomme de TeiTe River, which 

 has its mouth about 2 miles lielow. Twenty -five miles from Big Stoue 

 Lake the river enters Lac qui Parle, ^ wliich extends 8 miles, with a width 

 varying from one-fourth to three-fourths of a mile and a maximum depth 

 of 12 feet. This lake, as General Warren suggested, has been formed ))y 

 a bamer of stratified sand and silt which the Lac qui Parle River has 



' The French tianslation of the Dakota name, which is of uncertain origin (Williamson, 1. c, 

 p. 106). 



