274 W. UPHAM — GLACIAL LAKES IX CANADA. 



the last glacial epoch. The erosion of the valley therefore must have fallen 

 far short of supplying the material of the Assiniboine delta, not to mention 

 the fine silt and clay which were carried into the lake beyond the gravel and 

 sand delta and may be of equal volume. Probably at least half of these la- 

 custrine deposits were modified drift brought down by streams from the 

 melting ice-sheet on the upper Assiniboine basin north of the mouth of the 

 Qu'Appelle and swept forward by the strong current of the river until they 

 could be deposited in Lake Agassiz. 



