6o GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



Crags. The slide from the latter slope is still in process of formation and consists 

 of freshly broken angular fragments. That from Mt. Whyte is older and covered 

 with spruce, fir, and willow. This material overlies, and almost conceals, a 

 triple moraine, composed of boulders, gravel, and clay. The inner and higher 

 ridge of the three curves regularly across the valley and in one place about 60 

 feet of it have been cut away by the drainage brook. It here has a breadth of 

 100 feet, a height of about 20 feet, and consists largely of a yellowish, stony 

 till. Between it and the outer bear-den moraine the drainage stream has filled 

 in with sand and gravel, forming a nearly level flat. Lower down the slope 

 and 400 feet distant, there is another morainic ridge, approximately parallel 

 with the first, but made up more largely of boulders while 350 feet farther 

 on there is a third ridge containing a higher percentage of yellowish clay. 



b. Lake Louise basin. This lake is roughly elliptical, with a major axis of i;^ 

 miles and a width of :L to f of a mile, placed with its longer axis parallel with the 

 valley (see plate i and plate xiv, figure 2). The chief irregularity in the outline 

 is due to the presence of a rock slide from Mt. Fairview and to the delta deposits 

 at the head. The level of the lake is given by the Topographic Survey as 5,670 

 feet above sea level. This level, however, fluctuates in the course of the 

 season and from year to year, being some 15 inches higher in the spring, as a 

 result of the rapid melting of the snow. Fotu- determinations upon the inflow 

 at the head gave an average of 80 cubic feet per second. Two measurements 

 upon the outflow, through a rectangular orifice at the dam, gave an average 

 of 88 cubic feet per second, the lake receiving a small additional flow from 

 Mirror Lake and Lake Agnes. In midsummer, owing to the presence of the 

 glacial sediment, the lake has a superb green color, but during the winter this 

 has a chance to settle to the bottom and in the spring the color is more of a 

 blue, the natural color of pure water. 



From the studies of Mr. W. D. Wilcox, reported in the paper previously cited 

 (page 7), the basin of the lake is seen to be a U-shaped trough, with a maxi- 

 mum depth of 230 feet just beyond the centre. This shows that the valley 

 was excavated by ice and that, in all probability, the bottom of the lake is a 

 glacially excavated rock -basin, similar to that of Lake Agnes, just west but 

 at a higher level. Bedrock is found upon all sides of the lake, except about the 

 foot, where there is the ground-morainic dam previously described (page 8) 

 filling the valley to an unknown depth. At the head of the lake the valley walls 

 are much contracted, being but 570 feet apart. They consist of a very firm 

 quartzite, in the main, with a little slaty schist, dipping up the valley at an angle 

 of 10° to 15°. This feature of the valley must have greatly contracted the ancient 

 glacier passing through the gateway, caused it to thicken correspondingly 

 and to vigorously gouge out its bed until it had a chance to again expand laterally. 

 In this way we may account for the presence of the rock-basin, but should 

 expect the deepest part of it to be somewhat nearer the head of the lake than is 

 shown in Wilcox's contour map. It is not at all improbable, however, that the 

 deepest part of the rock -basin is really so located and that there has been a 



