NOTES ON THE VICINITY OF BANFF, ALBERTA 413 



one valley. Stream robbery then took place, owing to the advantage 

 possessed by the present lower course of the Bow, a stream on the 

 Cretaceous beds, over the upper part, the upper Bow-Minnewauka 

 River. This adjustment was preglacial. The Bow was thus drawn 

 away into its southeastward course in preglacial time, and a divide 

 was established at the western end of Minnewauka Valley. A river 



Fig. 4. — Bow Valley, from the Banff Springs Hotel; the preglacial course of the 

 Spray River. At the left the Bow is emerging from its postglacial canyon. 



continued to occupy this valley, emptying into Ghost River, until 

 obliterated by the ice-invasion. The basin may have been deepened 

 by ice-gouging; at all events, as the ice retreated northward, a lake 

 was formed at its western margin, and an outlet was formed to the 

 west, the eastern end of the gorge being still ice-filled. By the time 

 the ice had retreated altogether, the westward outlet was too well 

 ■established for a return to the eastward drainage. The present 

 level of the lake is lower than that of Ghost River. 



