252 W. D. WILCOX 



ever, to assume such a change in elevation, as a slightly greater 

 precipitation in the north would have made this valley discharge 

 its glacier to the south. 



We have then, the following, as a summary of the indications 

 of the nature of former glacial activity in this part of the 

 Canadian Rockies : 



i. Evidence in the drift formations that glaciers formerly 

 occupied all the mountain valleys. 



2. Evidence in certain till exposures that there were at least 

 two distinct ice invasions. 



3. Evidence from glacial contours, striations, grooves, and 

 erratics no less than from the absence of them on isolated 

 peaks over 9000 feet high that the former glaciers were between 

 1500 and 3000 feet in thickness, that their maximum height in 

 the valleys was between 7000 and 9000 feet above sea level, and 

 that the maximum glaciation of this region was always confined 

 to the valleys, above which the very elevated regions and 

 mountains, which were centers of dispersion, rose like islands. 



4. Evidence, from the above, that the present drainage system 

 represents approximately the direction of the former ice cur- 

 rents. 



Having thus very briefly reviewed the extent of the ice inva- 

 sion in the Canadian Rockies within the latitude specified, it is 

 now possible to get a clearer idea of the special type of lake 

 basin which is the subject of this article. 



Lakes, though very numerous, are limited in size as would 

 naturally be expected in a region of narrow valleys and steep 

 gradients. The two Bow lakes at the sources of the river of that 

 name, are each about four miles long by cne mile wide. Out- 

 side of these lakes the great majority are smaller and are of all 

 dimensions down to mere pools two or three hundred yards 

 across. About one hundred of these lakes were more or less 

 thoroughly examined and, in regard to their formation, may be 

 divided into four classes. 



1 . Lakes formed in kettle holes of the valley drift, often in 

 chains of three or four together. In this class should be included 



