GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 9 



of the Bow.^ The topographic map of the region, issued in 1902, shows that 

 the river opposite the Gap is fully 100 feet higher than the level of Lake Minne- 

 wanka and about 400 feet higher than the present level of the Bow in the 

 vicinity of Banff. According to this view of McConnell the ice-filled Minne- 

 wanlca Valley compelled the Ghost River to find for itself a new course across 

 the foot-hiUs to the eastward, which it deepened sufficiently, assisted probably 

 by the ice, to prevent the return of the river into its former course upon the 

 withdrawal of the glacier from the valley. In 1904 Dr. I. H. Ogilvie examined 

 the region and reached the conclusion that the upper Bow and Minnewanka 

 valleys were formerly continuous and that the Bow Valley below Banff was 

 occupied by a stream which cut back into the soft shales until it tapped the 

 upper Bow and effected its capture. She concluded^ that this had been ac- 

 complished in prepleistocene time and that the Lake Minnewanka Valley was 

 occupied by a glacier, fed by hanging glaciers, which moved westward, rather 

 than to the east, deepening the western end of the valley and forming certain 

 morainic deposits about the western end of the lake. The lake itself and its 

 southwesterly drainage would then date from the withdrawal of the ice from 

 the Cascade and Minnewanka valleys. Dr. Ogilvie holds that the drainage in 

 the Lake Minnewanka Valley before the advent of the glaciers was eastward. 



The bed of the Bow River at Banff is approximately 4,500 feet above tide, 

 while that of the Ghost River, opposite the Devil's Gap, is not far from 4,900 

 feet. The present Bow, in the same distance as that from Banff to this portion 

 of the Ghost River, drops 300 feet, so that the bed of the Bow at Banff is some 

 700 feet lower than it should be in oi'der to have the upper Bow leave the 

 mountains by the Devil's Gap and thence by the lower Ghost River. All 

 will grant that this is too much cutting to expect of the Bow in postpleistocene 

 time and that Dr. Dawson's theory of the diversion of the Bow by the Pleistocene 

 glaciers is untenable. Noting that the Ghost River has also been deepening 

 its bed, with a much steeper gradient and presumably for as long a time as the 

 Bow, the above 700 feet must represent the excess of cutting by the upper Bow, 

 when compared with the Ghost, since its capture by the lower Bow, upon Dr. 

 Ogilvie's hypothesis. We have no knowledge of the depth of the drift deposits 

 opposite the Devil's Gap, but there is no reason to think that they would be 

 any deeper there than in the valley of the Bow. The explanation that lies 

 nearest at hand is that of McConnell, viz., that the Ghost River upon reaching 

 the foot-hills made a sharp turn and reentered the mountains by the Devil's 

 Gap, but was diverted eastward when the Minnewanka Valley became ice- 

 filled. According to this hypothesis the valley of the Ghost from the Gap 

 down should show less maturity than that above the Gap, except so far as it 

 may have been modified by ice action. During the period of maximum glacia- 

 tion the ice movement in the Minnewanka Valley must have been eastward, 



> Annual Report of Canadian Geological Survey ior 1886. Report on the Geological Features of a 

 Portion of the Rocky Mountains, 1887, R. G. McConnell, p-. 9D. 



^"Geological Notes on the Vicinity of Banff, Alberta," Jour, of Geol., vol. xii, No. 5, 1904, pp. 408 

 to 414. 



