1 84 The Ottawa Naturalist. 



Prof. Coleman disagrees with Dr. Lawson regarding these 

 anorthosite rocks in not "representing the truncated base of a 

 Keewatin volcano " but as " having solidified under a consider- 

 able thickness of superincumbent rock " and been exposed by 

 denudation so as to be eroded and fragments rolled into 

 bowlders which appear as part of a conglomerate before the 

 eruption of the granite. — H. M. A. 



Tyrrell, J. Burr — " The Genesis of Lake AgassizJ' Journal 

 of Geology, Vol. V., No. 7, pp. 8ii — 815, Chicago, Dec 

 1896. 



In this paper, Mr. Tyrrell first describes the two centres of 

 glaciation or gathering grounds for the snow and ice on each 

 side of Hudson Bay during the " Great Ice Age." He then 

 more closely defines the terms, " Keewatin glacier" and " Laur- 

 entide glacier " which have been applied to these centres by him- 

 self* and Dr. Dawson Regarding the origin of Lake Agassiz 

 itself, Mr. Tyrrell states : — " The Keewatin glacier seems to have 

 retired northward well into Manitoba, and possibly even beyond 

 the northern limit of that province, before it was joined by the 

 eastern glacier. When they united the water was ponded be- 

 tween the fronts of the two glaciers to the north and east, and 

 the highland to the south and west. Thus Lake Agassiz had 

 its beginning." The later history of the lake is to some extent 

 still undetermined, but is given in the light of the evidence 

 obtained during several explorations in those regions. A passing 

 note is also made of the " Cordilleran glacier " \ in the moun- 

 tains of British Columbia and of a fourth great glacier — the 

 Greenland glacier^, that which "covers Gr eenland at the present 

 time."— H. M. A. 



*C3eographical Journal, London, pp. 439, November, 1895. 



% G. M. Dawson in Bull. Geol. Soc. Am., Vol. 7, pp. 31-66, 1895. 



