DRAISAGE OF Tilt; GLACIAL PERIOD. 



33u 



meridian, and twenty-live or thirty miles south of the As- 

 siniboin. Professor Hind finds evidence that this was the 

 outlet temporarily not only of the Assiniboin but, through 

 the Qu'Appelle and the River that Turns, to the South Sas- 

 katchewan. Mr. Upham writes me that he has followed this 

 old valley for one hundred and twenty-five miles as far as 

 Birtle, in Manitoba. According to Professor Hind, the 

 length of the valley of the Qu'Appelle, from Birtle up to 

 the Saskatchewan, is two hundred and sixty-eight miles in 

 direction northwest by southeast. The valley is uniformly 

 about one mile wide, and from one hundred and ten to three 

 hundred and fifty feet below the general level, and eighty- 

 five feet above the present level of the South Saskatchewan, 

 the descent being four hundred and forty feet from the 

 Saskatchewan to the Assiniboin. The inclosing bluffs con- 

 sist mainly of till, and the whole trough is characterized by 

 numerous long, shallow lakes. These lines of marginal drain- 

 age are readily explained upon the glacial hypothesis here 

 maintained, and are a strong proof of that hypothesis. As the 

 ice receded, more northern outlets were opened, and these 

 temporary channels were naturally abandoned. 



Fig. 100 — Map of South Dakota showing the extent to which the channel of the Missouri 

 River was permanently changed during the early Wisconsin epoch. The broken 1 lnea 

 indicate theformer course of the Grand, Cheyenne, and White Rivers as they joined 

 the original Missouri when flowing through the James River valley. (Map by Torld.) 



