Canadian Rocky Mountains. 291 



The base-level of this part of the Rocky Mountains is 

 much higher on the eastern than on the western side. On 

 the east, as ascertained by taking the average level at which 

 the larger streams leave the mountains, it is about 4360 feet, 

 while on the west, the mean elevation of the corresponding 

 portion of the Columbia-Kootanie Yalley is about 2 ±50 feet. 

 It is in consequence of this difference that the profiles of 

 the various passes show sudden, steep descents to the west, 

 and the streams flowing westward are also, as a rule, more 

 actively engaged in erosion. The abrupt dip from the 

 watershed, on the west side, was the greatest obstacle in 

 the selection of a practicable railway route, and constituted 

 the most formidable engineering difficulty in the pass 

 actually adopted. 



The general trend of this portion of the mountains has 

 already been given as N. !N. W. — S. S. E., but when more 

 closely examined it is found actually to include three subor- 

 dinate directions. That portion of the range which ex- 

 tends on the east side from the forty-ninth parallel, to the 

 South Fork of the Old Man River, has a general bearing 

 of 1ST. 35° "W. Thence northward to the Highwood River, 

 the general trend is about N.12° W., after which, the bear- 

 ing again becomes about N. 35° W., and so continues to 

 beyond the Red Deer River. The portion of the range 

 which runs nearly north and south, is considerably wider 

 than the rest ( being about sixty miles in width ) and 

 includes a remarkable series of infolds of Cretaceous rocks. 

 The constituent ranges and ridges of both the mountains 

 and foot-hills conform throughout very markedly, to the 

 directions above given ; and while the three trends are 

 most clearly shown by the outer, eastern range, they are 

 scarcely less evident on the western border. The least 

 regular, and most tumultuous portion of this mountain 

 region is that in the vicinity of the forty-ninth parallel. 



In common with most mountain ranges (and here 

 specially marked, in consequence of the regular parallel 

 folding of the rocks) the ruling features are parallel ridges 

 and valleys, crossed nearly at right angles by a system of 

 transverse breaks. The cause of these cross valleys is not 



