HISTORICAL NOTICES. 17 



points with these theorists, we can dispense altogether 

 with the portentous changes in physical geography involved 

 in their views, and which are not necessary to explain 

 any of the other phenomena." 



The address then proceeds to deal with these points in 

 the manner to be stated in a subsequent chapter. 



Two years later, in 1866, I prepared an account of all 

 that was known up to that date of the fossil plants of the 

 mid-pleistocene beds, the Leda clay of the Ottawa and St. 

 Lawrence valleys, equivalent in age to the so-called inter- 

 glacial beds of western Canada. In this paper the 

 following summary is given of the climatal conditions 

 indicated : 



"None of the plants from these mid-glacial beds is 

 properly arctic in its distribution, and the assemblage 

 may be characterized as a selection from the present 

 Canadian flora of some of the more hardy species having 

 the most northern range. Green's Creek is in the central 

 part of Canada, near to the parallel of 46, and an acci- 

 dental selection from its present flora, though it might 

 contain the same species found in the nodules, would 

 certainly include with these, or instead of some of them, 

 more southern forms. More especially the balsam poplar, 

 though that tree occurs plentifully on the Ottawa, would 

 not be so predominant. But such an assemblage of drift 

 plants might be furnished by any American stream 

 flowing in the latitude of 50 to 55 north. If a stream 

 flowing to the north, it might deposit these plants in still 

 more northern latitudes, as the McKenzie river does 

 now. If flowing to the south, it might deposit them to 

 the south of 50. In the case of the Ottawa, the plants 

 could not have been derived from a more southern 

 locality, nor probably from one very far to the north. 



