150 /. BURR TYRRELL 



unearthed is undoubtedly but a very small portion of what will 

 be known when our country is more fully explored, for com- 

 pared to the vastness of the field and the probable extent of the 

 harvest of knowledge, the harvesters are indeed very few. The 

 observations here discussed have been made by the writer dur- 

 ing the past thirteen years, but as individual records are difficult 

 to grasp and remember, I have attempted to connect them in 

 such a way, and to bring them graphically before you, so that 

 you may form a clear idea of the results that have been attained, 

 and at the same time I shall endeavor to state very briefly some 

 of the evidence on which those results have been based, so that 

 you may distinguish between the records and the connecting 

 theories. 



Up to the present time three great continental glaciers have 

 been recognized in Canada, viz., the Cordilleran, which covered 

 the western mountains and their intervening plains, from lati- 

 tude 49 to latitude 66° ; the Keewatin, which covered the great 

 plains east of the mountains ; and the Labradorean, which spread 

 over northeastern America from a center in Labrador. 



The earliest till as yet recognized in Western Canada, east 

 of the Rockies, has been called by Dr. Dawson the Albertan 

 Deposit, 1 and has been shown by him to have been formed by 

 tongues of the Cordilleran glacier, which extended outwards 

 towards the plains through the transverse valleys of the Rocky 

 Mountains. 



The illustration shows the greatest extent of this Cordilleran 

 glacier as defined by Dr. Dawson. 



From the fronts of these glacial tongues streams rushed 

 eastward, carrying with them large quantities of coarse detritus 

 which were soon deposited in the bottoms of the valleys as beds 

 of coarse, well-rounded gravel, called by Mr. McConnell the 

 Saskatchewan gravel, this gravel and the Albertan till being 

 directly traceable into each other. 



The Cordilleran glacier then withdrew; but whether it entirely 



1 Glacial Deposits of Southwestern Alberta, by George M. Dawson and R. G. 

 McConnell, Bull. Geol. Soc. Am., Vol. VII, p. 66, Rochester, 1895. 



