316 THE ICE AGE IN NORTH AMERICA. 



side to side as a very insignificant thing, entirely out of pro- 

 portion to the valley which it occupies. Nor does the Min- 

 nesota River have its sources in the highlands, like the Mis- 

 sissippi. Its head is in Big Stone Lake, in the midst of this 

 eroded trough, and but a few miles south of Lake Traverse — 

 the head of the Red River of the North — also in the same 

 trough and on the same absolute level. The water from Lake 

 Traverse sometimes flows into the other lake. In short, the 

 troughs of the Minnesota and the Red River of the North 

 are one and continuous, and the depression joining them, 

 known as Brown's Valley, is to the glacial ist one of the most 

 interesting spots on the continent. The following is Mr. 

 Upham's description : 



Lakes Traverse and Big Stone are from one to one and a 

 half mile wide, mainly occupying the entire area between the 

 bases of the bluffs, which rise about one hundred and twenty- 

 five feet above them. Lake Traverse is fifteen miles long ; it 

 is mostly less than ten feet deep, and its greatest depth proba- 

 bly does not reach twenty feet. Big Stone Lake is twenty-six 

 miles long, and its greatest depth is reported to be from fifteen 

 to thirty feet. The portion of the channel between these lakes 

 is widely known as Brown's Valley. As we stand upon the 

 bluffs here, looking down upon these long and narrow lakes in 

 their trough-like valley, which extends across the five miles 

 between them, where the basins of Hudson Bay and the Gulf 

 of Mexico are now divided, we have nearly the picture that 

 was presented when the melting ice-sheet of British America 

 was pouring its floods along this hollow. Then the entire ex- 

 tent of the valley was doubtless filled every summer by a river 

 which covered all the present areas of flood-plain, in many 

 places occupying as great width as these lakes.* 



Among the most interesting facts concerning the drainage 

 lines of the glacial period are those connected with the 



* "Proceedings of the American Association for the Advancement of Sci- 

 ence," vol. xxxii, 1883, pp. 216, 217. This glacial outlet through Brown's Val- 

 ley and the Minnesota has been fittingly named, by Mr. Upham, River Warren, 

 after General G. K. Warren, who first described it. See map in Chapter XXI. 



