HISTORICAL NOTICES. 19 



111 other words, if Canada was submerged until the 

 Ottawa valley was converted into an estuary inhabited by 

 species of Leda, and frequented by capelin, the diminution 

 of the summer heat consequent on such depression, would be 

 precisely suitable to the plants occurring in these deposits, 

 without assuming any other cause of change of climate." 



This extract, referring as it does to the evidence of 

 plants, reminds us of the contrast between the Pleistocene 

 and the warm climate of the early Eocene and later 

 Cretaceous, when warm temperate plants could flourish 

 as far north as Greenland. The reason is seen in our 

 comparative maps of the Cretaceous and Pleistocene of 

 Canada. The conditions presented in the latter show the 

 greatest possible facilities for the transference of arctic 

 ice to temperate latitudes, and its accumulation therein, 

 while leaving the extreme arctic comparatively free of 

 ice. Such conditions are the reverse of those in the early 

 Eocene, when the interior of the continent was occupied 

 with a warm mediterranean sea, shielded from the arctic 

 ice. Thus the known geographical condition of the Pleis- 

 tocene harmonize with rational views as to the causes and 

 extent of the refrigeration. 



Lastly, in my address to the Natural History Society 

 of Montreal, in 1873, immediately after the publication of 

 the " Notes," above referred to, the following reference to 

 the position of the question occurs : — 



" In the memoir in the Journal of the Natural History 

 Society already referred to, I have re-asserted and sup- 

 ported by many additional proofs the theory of the 

 combined action of floating ice and glaciers in the produc- 

 tion of our Canadian boulder clay and other superficial 

 deposits, which I have for many years maintained, in 

 opposition to the views of the extreme glacialists. It is 



