DISCUSSION. 



Mr. J. E. Mills: I should like to mention, in connection with this paper, 

 General Warren's account of the canon of the Mississippi. He traced the 

 Mississippi canon up to that of the Red river, and thence on to Lake Winni- 

 peg. He inferred from what he saw that the canon when first formed was 

 higher than now, and that the waters of the Winnipeg flowed at that eleva- 

 tion southward. He inferred, also, that the canon was formed by a river 

 much larger than the present Mississippi. General Warren announced this 

 about 1869. I had the pleasure of doing a part of the geological work of 

 his survey. If I understand Professor Chamberlin rightly, the canon was 

 excavated between the two glaciations. In that intermediate period the 

 drainage of Lake Winnipeg was southward through the Mississippi valley, 

 and if General Warren's account is correct, the country north of Lake 

 Winnipeg must have been drained southward. Professor Chamberlin shows 

 that at this very time the country of the lower Mississippi was at base level — 

 was very low. There certainly was an elevation, therefore, that caused the 

 erosion of the Mississippi canon about that time. This seems to confirm and 

 strengthen General Warren's deduction that there was an elevation, and 

 an elevation increasing northward. I should like to have Mr. Tyrrell state 

 what bearing his observations have upon this deduction of General Warren's. 



Mr. Tyrrell : The problem of the direction of the preglacial drainage of 

 the Lake Winnipeg basin is a long and complex one. I can merely say here 

 that much of the evidence at present in hand goes to show that it was drained by 

 a river flowing with a more or les3 northerly course. I know of no evidence 

 found in Canadian territory that will serve to indicate the direction of drain- 

 age in the interval between the first and second glacial periods. In the 

 Winnipeg basin the tracks of the older glacier have been obliterated or 

 greatly obscured by the severe erosion of the later glacier. Generally speak- 

 ing, one must look farther south or nearer the ancient ice-front for the clearest 

 evidence of the earlier glaciation, though it is quite probable that inter- 

 glacial beds exist in Manitoba. In the postglacial period the Winnipeg 

 basin was first drained southward through the valley of Lake Traverse and 

 down the Minnesota river, and afterwards in a northerly or northeasterly 

 direction, as at present. 



On this latter subject, however, I beg to refer to President Chamberlin, 

 who has given the matter a large amount of attention. 



President T. C. Chamberlin : The cutting of the trench from the outlet 

 of Lake Agassiz down to the Mississippi was a work which followed the 

 main glaciation of the second period, and was not a part of the great trench- 

 ing of the Mississippi to which I referred in my paper. 



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