270 W. UPHAM — GLACIAL LAKES IN CANADA. 



direction * >i^ ^ about thirteen miles east of the mountains, in a region 

 of wide valleys and low foot-hills." * 



On the Peace river in its course close east of the Rocky Mountains, and 

 on its tributary, Pine river, Dawson reports drift containing a large pro- 

 portion of " hard quartzite pebbles like the more resistant materials of the 

 axial range of the Rocky Mountains. These are mingled with a preponder- 

 ating number of fragments of the softer sandstones of the country, and im- 

 bedded in a whitish or cream- colored silty clay, not unlike the material 

 representing the bowlder-clay over wide districts west of the Rocky Mount- 

 ains. No Laurentian or other fragments of eastern origin were observed 

 in this region." Continuing eastward, these drift deposits become more 

 conspicuous, attaining in places a thickness of 150 feet. On reaching the 

 D'Echafaud river, about 100 miles from the mountains, though "no change 

 in the character of the drift deposits w^as noted, * >i^ ^=^ Laurentian 

 pebbles and bowlders were for the first time seen in considerable abun- 

 dance * * *. East of this point ^ ^ * the surface is thickly covered 

 with drift deposits, so nmch so that exposures of the underlying rocks are, 

 as a rule, only found in the larger river valleys." f No better evidence 

 could be desired by a glacialist, accounting for the formation of the bowlder- 

 clay by the agency of land-ice, to demonstrate the confluence here of two 

 currents of the ice, one flowing eastward from the Cordilleran area, and the 

 other flowing westward from the Archean area, whose nearest portion is on 

 Lake Athabasca, about 400 miles distant. 



Near the divide between the Liard and Yukon river systems, Dawson 

 found drift on the summit of an isolated mountain 4,300 feet above the sea 

 and about 1,000 feet above this part of the Pacific-Arctic water-shed. J 

 This, however, is on the west side of the Rocky Mountains proper, which, as 

 defined by Dawson, constitute the northeastern marginal range of the broad 

 mountainous Cordilleran belt. With this definition, the Rocky Mountains 

 are intersected by the Mackenzie river south and west of Great Bear lake. 



Farther northward, the Laurentide or eastern portion of the ice-sheet 

 pushed northwestward to the extreme limit of the drift. " The till near the 

 lower ramparts of the Mackenzie," according to Mr. R. G. McConnell, " is in 

 approximately the same latitude as the northern boundary of the Archean 

 area on the east, and the gneissic bowlders which it contains must have 

 travelled either directly west or northwest in order to reach their present 

 situation." He therefore infers that " the ice from the Archean gathering 

 grounds to the east poured westward through the gaps and .passes in the 

 eastern flanking ranges of the Rocky Mountains until it reached the barrier 



*Geol. and Nat. Hist. Survey of Canada, Report of Progress, 1882-84, pp. 146 C, 151 C ; Annual 

 Report, new series, vol. I, for 1885, p. 167 B. 

 t Geol. and Nat. Hist. Survey of Canada, Report of Progress, 1879-80, pp. 139, 140 B, 

 f Geol. and Nat. Hist. Survey of Canada, Annual Report, vol. Ill, 1887-88, p. 119 B. 



