GLACIATION OF THE CANADIAN INTEKIOK. 269 



The prevailing courses of glaciation and dispersal of the drift lead me to 

 recognize, with Dr. Dawson^ the existence of two central areas upon which 

 the ice was accumulated in greater depth than elsewhere and from which 

 consequently it flowed outward on all sides. One of these areas embraced 

 the Laurentide highlands, James's bay, a portion of Hudson's bay, and the 

 western part of the Archean region from lakes Superior and Winnipeg to Great 

 Slave and Great Bear lakes. From this large northeastern or Laurentide 

 center of outflow, the ice-sheet crept southward, eastward, and northward, to 

 the limits of glaciation before noted. Westward the ice from this area out- 

 flowed, as I believe, to the limit of Archean boulders on or near the base of 

 the Rocky Mountains, where I find, from Dr. Dawson's observations of the 

 drift in Alberta and on the Peace river, that it abutted against and was con- 

 fluent with ice outflowing eastward and southeastward from the Rocky Mount- 

 ains. The other area whence currents of the ice-sheet flowed radially in 

 every direction was the northern-central part of British Columbia ; and the 

 portions of the ice-sheet pouring outward respectively from these two centers 

 have been named by Dawson the Laurentide and Cordilleran glaciers. To- 

 ward the south, west, and northwest, the Cordilleran outflow extended to the 

 boundaries of our glaciated area ; but eastward, pouring through passes of 

 the Rocky Mountains, and in the Peace river region probably overtopping 

 the highest summits, which there are only about 6,000 feet above the sea, 

 the Cordilleran ice pushed across a narrow belt adjoining the mountains, to a 

 maximum distance of nearly 100 miles, and there (on laud about 2,500 feet 

 above the sea) became confluent with the Laurentide ice, the two united 

 currents thence passing in part to the southward and in part to the northward 

 from the interior tract where the confluent ice was thickest. 



Taking up the particular description of localites where the junction of the 

 Laurentide and Cordilleran drift has been observed, we may begin at the in- 

 ternational boundary and proceed northward. Laurentian erratics and 

 drift are stated by Daw^son to extend quite to the foot of the Rocky Mount- 

 ains near the 49th parallel and to occur between the 49th and 50th parallels 

 " stranded on the surface of moraines produced by the large local glaciers of 

 the Rocky Mountains." * 



In the neighborhood of Calgary, which is the western limit of Laurentian 

 bowlders and till, Dawson reports somewhat farther westward a deposit resem- 

 bling bowlder-clay, in which the stones " are entirely those of the mountains 

 or sandstone blocks from the underlying beds." Accordingly he declares 

 that the absence of Laurentian erratics west of Calgary is probably to be 

 accounted for "by the existence of Rocky Mountain glaciers of sufficient size 

 in this region to fend ofi'the eastern glaciating agent." Again, he mentions, 

 west of Calgary, " heavy glacial striation in a southward or southeastward 



* Trans. Roy. Soc. Canada, vol. VIII, sec. tV, p. 57. American Geologist, vol. VI, Sept., 1890, p. 162. 



