268 'W. UPHAM — GLACIAL LAKES IN CANADA. 



eastern base of the Rocky Mountain range in Canada,^ and of Dr. G. M. 

 Dawson, Avho doubts that an ice-sheet has ever existed on a much wider area 

 stretching from the Rocky mountains far eastward across the Peace and 

 Saskatchewan plain country nearly to Lake Athabasca and the lakes of 

 Manitoba.f Without entering into a discussion of the methods of formation 

 of the various drift deposits, it may make my views more readily understood 

 to add that I agree perfectly with Mr. Tyrrell in referring all deposits of 

 bowlder-clay or till directly to the agency of land-ice, without modification 

 or aid by w^ater ; while Dr. Dawson, on the other hand, refers all these de- 

 posits of till to a glacio-natant origin, that is, to deposition from floating ice 

 supplied from glaciers and borne over the till-covered areas during their 

 submergence by lakes or the sea. 



In a paper published last year, J I presented somewhat in detail the evi- 

 dence that the ice-sheet of the second Glacial epoch covered the highest 

 summits of the White mountains, the Green mountains, and the Adirondacks, 

 flowing over them from the north and northwest. The thickness of this ice- 

 sheet at the culmination of the latest glaciation of the northeastern part of our 

 continent was about one mile over northern New England and northern New 

 York ; and Dana has shown, from the directions of striation and transpor- 

 tation of the drift, that over the Laurentide highlands between Montreal and 

 Hudson's bay it had probably a thickness of fully two miles. On the east 

 we are indebted to Professor C. H. Hitchcock for the proof that the ice-sheet 

 overtopped Mt. Washington, 6,293 feel above the sea ; and in British Colum- 

 bia Dr. Dawson finds that it covered mountains 5,000 to 7,640 feet high, 

 and he estimates that its highest central part upon that province " had an 

 elevation of at least 7,000 feet above the mean elevation of the interior plateau, 

 which would be equivalent to an elevation of about 10,000 feet above the 

 present sea-level, or probably 11,000 feet above the sea-level of the time." § 

 Between these eastern and western areas of great known thickness of the ice, 

 as determined by the height of glacial drift and striae on mountains, prob- 

 ably this ice-sheet across the the interior of Canada at one time attained a 

 thickness of a mile or more on a central belt several hundreds of miles wide, 

 reaching from the Rocky Mountains and the upper Mackenzie to Reindeer 

 lake and Lake AVinnipeg, the southwestern part of Hudson's bay, James's 

 bay, the Laurentide highlands, southern Labrador, and the Gulf of St Law- 

 rence. This proposition differs so widely from the views of the authors be- 

 fore cited, for the country adjoining the eastern base of the Rocky Mountains, 

 that the evidences of its truth for that district must be definitely and partic- 

 ularly stated. 



* Bull. Geol. Soc. Am., vol. 1, pp. 396, 400, 401. 



t Trans. Roy. Soc. Canada, vol. VIII, sec. IV, pp. 54-74. 



I Appalachia, vol. V, pp. 291-312; also in American Geologist, vol IV, 1889, pp^. 165-174 and 205-216. 



g Trans. Roy. Soc. Canada, vol. VIII, sec. IV, p. 28. 



