412 I. H. OGILVIE 



preglacial course of the Bow River. If this were the case, a drift- 

 dam, or indications of an ice-dam, should be found, and the valley 

 beneath the drift should present older features in the preglacial than 

 in the present Bow Valley. 



An investigation of the western end of the Lake Minnewauka 

 disclosed hills of morainic aspect, evidently deposited at the junction 

 of an ice-lobe descending the Cascade Valley with one coming from 

 the Minnewauka Valley. Westward from these morainic hills is an 

 overwash plain which descends westward and southeastward to form 

 the upper terrace of the Cascade River. Lake Minnewauka is held 

 up by this moraine, and its existence as a lake undoubtedly dates 

 from the time of retreat of the ice. But that this dam could have 

 diverted the Bow River is not possible. The outlet of Lake Minne- 

 wauka flows through drift for about a mile; it then joins the Cascade 

 River, and together they flow through a postglacial gorge cut in Car- 

 bonic limestone. This gorge is known as the Devil's Canyon. The 

 surface of this limestone is drift-covered, and the top of the gorge 

 undoubtedly represents the height of the valley floor before the ice- 

 invasion, also the amount eroded by the ice. This level is 5,000 feet. 

 The limestone cut by the Devil's Canyon extends in a low ridge for 

 more than a mile and blocks any considerable outlet or inlet of the 

 Minnewauka Valley. Any river flowing in or out of this valley in 

 preglacial times must have had its floor above 5,000 feet. 



Five miles southwest of the lake the Bow River flows mainly over 

 gravel. The Cretaceous beds are occasionally exposed, but the 

 valley bottom is mainly in drift. The valley floor at this point is 

 4,350 feet, and the preglacial river in this valley could not have been 

 higher. It therefore follows that no preglacial river could have 

 flowed from the Bow to Lake Minnewauka Valley. 



Moreover the lower Bow Valley (below the junction with Cascade 

 River) is older physiographically than the Lake Minnewauka Valley, 

 The sides are less precipitous, the cross-section, though steep sided, 

 more nearly U-shaped. 



In the opinion of the writer, the present drainage at this point is 

 due, not to glacial agencies alone, but to preglacial adjustment to 

 the soft Cretaceous beds. The Minnewauka Valley and the Bow 

 Valley above the junction with Cascade River were probably once 



