No. 7.] DANA — DISCHARGE OF J.AKE WINNIPEG. 437 



and n review of the writings of previous travellers who had 

 recognised the lake-like features of the region. 



The idea of the southward discharge of Lake V\''innipe<i' was 

 presented again in 1875 by Mr. George M. Dawson, in his ex- 

 cellent Report on the Geology of the region in the vicinity of 

 the 49th Parallel, with a recognition of General Warren's paper, 

 but with the statement that the inference was an independent 

 one. In explanation, he says (pp. 253, 254) th.it '• by the flow 

 of a large volume of water in this direction, the excavation of 

 the basins of the Winnipeg group of lakes and the great valley 

 of the Red River itself can be explained; the river cutting 

 downward and westward on the sloping surface of the Laureu- 

 tian rocks at the expense of the Cretaceous strata and later of 

 the limestones of the Devonian and Silurian ; the blocking up 

 of the southern exit and changed direction of flow" being a pheno- 

 menon only similar to that which is known to have taken place 

 with the great lakes of the St. Lawrence."' 



The ice-barrier hypothesis has been sustained, in place of 

 that of a change of level, by Professor N. H. Winchell, in 

 his Minnesota Report for 1877, who there observes, in his 

 explanation, that the lake, having first appeared at the south 

 or Minnesota end, "grew toward the north as fast as the retreat- 

 ing ice-sheet made way for it." In the Minnesota Report for 

 1879, the same view is urged, with more detail, by Mr. Warren 

 Upham. 



A decision between these two conflicting explanations is of 

 great importance to a right understanding of Quaternary events 

 as well as of fundamental principles in terrestrial dynamics; and 

 I therefore review here the more prominent facts, taking them 

 mostly i'rom General Warren's pipers and the Report of Mr. 

 Dawson. 



1. The Red River of the North, rising in Lake Traverse, 

 flows northward along the west side of Miimesota for 225 miles, 

 crosses then the 49th Parallel, and continues on the same course 

 for 90 miles to Lake Winnipeg; the distance from Lake Trav- 

 erse to Lake Winnipeg being 315 miles. 



2. The 31innesota, rising to the westw\ard of Lake Traverse, 

 enters its valley within two miles of it and flows south, through 

 Big Stone Lake, to the Mississippi at Minneapolis. 



3. The Valley of Red River, after narrowing much, is still 46 

 miles wide on the 49th parallel, and, for a long distance south 



