2 54 IV. D. WILCOX 



4. Lakes found just within the mouths of tributary valleys. 

 These lakes are the most constant of all in their outline and posi- 

 tion. They are invariably found where a lesser valley joins a 

 larger one and occupy the mouth of the lesser valley. They 

 are usually leaf-shaped and from three to ten times longer than 

 wide. 



Of this type Lake Louise is a good example and was made 

 the subject of special study. Lake Louise is in one of the tribu- 

 tary valleys of the Bow River about twenty-five miles below its 

 source, in latitude 51° 30' N. and longitude 116 15' W. The 

 shore line was carefully surveyed and mapped, after which the 

 basin was studied by means of soundings. The accompanying 

 map of this lake on which the contours represent the depression 

 of the bottom below the surface, shows that the basin is very 

 deep in proportion to it's size. The basin is U-shaped with a 

 nearly flat bottom, and with exceedingly steep sides approach- 

 ing in many places a slope of forty-five degrees. 



The lake occupies the end of a valley just above its junction 

 with the much wider valley of the Bow. The catchment basin 

 draining into this lake is an exceedingly rough part of the 

 Rockies, with peaks over 11,000 feet high, forming part of the 

 continental water-shed, at the valley end. The surrounding 

 mountains are covered with considerable fields of ice, which 

 unite to form a glacier about three miles long, measured up 

 either one of its two branches. 



A stream from the glacier has carried in clay and gravel so 

 that a delta has formed, and filled in the upper part of the lake 

 basin to the extent of one third of a mile or more. The fine 

 mud carried by the glacial stream which is not heavy enough to 

 sink at once upon reaching the quiet waters of the lake, remains 

 suspended in the lake throughout the summer, and turns its 

 blue-green water to a milky color by the end of August. In 

 November the lake freezes, the inlet stream is much reduced in 

 volume, and becomes clear, and the exceedingly fine mud set- 

 tles to the bottom. This settling process continues under a thick 

 protection of ice and snow for six months, and with few or no 



