70 THE ICE AGE OF CANADA. 



cene, as illustrated by Dr. G. M. Dawson in his Memoirs 

 on British Columbia, by Mr. Chalmers on the lower St. 

 Lawrence, by Upham, Gilbert and Spencer in the lake 

 regions, and by De Geer in Sweden. To Spencer we 

 are indebted for a great mass of valuable observations on 

 the lake margins of the Canadian lakes and the questions 

 of the origin of the lakes and the primitive course of the 

 St. Lawrence river anterior to the Pleistocene age, as well 

 as to the former greater extension of the lakes and the 

 differential elevation by which they have been affected.* 



* Canadian Naturalist, 1882. Trans. R.S. Canada, 1889. See also 

 Warren Upham's Appendix to Wright's Ice Age and McGee's Seventh 

 Report Am. Geol. Survey, p. 639. 



