86 THE ROYAL SOCIETY OF CANADA 



enlarged, and the stream soon splits up into several tributaries which 

 wind through the wide marsh-filled valleys separating the hills and 

 ridges of the district, 



"The eastern range, here, as elsewhere along the valley, consists 

 of the limestones, gneisses, and schists of the Shuswap series. A band 

 of hard compact limestone outcrops at the water's edge, while farther 

 back, bands of mica-gneisses, lustrous mica-schists, hornblende 

 schists, and occasionally quartzose schists, alternate across the range. 

 These rocks all dip to the southwest at angles from 50° to 60°, and 

 strike N.73°W. 



"The Shuswap series has a width at Paul's Branch of two miles. 

 It is succeeded towards the east by argillites, calc-schists, and lime- 

 stones of Cambrian age, dipping in a southwest direction under the 

 older rocks. The contact between the two formations is apparently 

 a faulted one, the Shuswap series being thrust eastward over the 

 younger formation. 



"The ridges forming the central part of the Rocky Mountain 

 range were not examined closely, but, judging from their appearance 

 and from the wash of the streams flowing from them, they are evidently 

 composed of massive limestones, similar to those found in a corres- 

 ponding position in other parts of the range. 



"From Paul's Branch to the Quadacha, a distance of ten miles, 

 the Finlay follows the eastern bank of the valley, and occasional 

 exposures of the schists of the Shuswap series occur. A short distance 

 below the mouth of the Quadacha, Laramie conglomerates outcrop on 

 the left bank. 



"At the Quadacha, the Finlay bends to the west and soon after 

 leaves the great valley which it has occupied from its mouth to this 

 point. The valley continues northward, and is occupied, after the 

 Finlay abandons it, by the Tochieca, a tributary. 



PART II 



Physiographic Development 



The study of the physiographic development of the Rocky 

 Mountain trench may be prefaced by a statement of certain physical 

 facts concerning the present trench (Figure 2). 



1. The size of the valley in most cases bears no relation to the size 

 of the present streams which occupy it. 



2. The divides in the trench have a uniform low elevation, 

 Fraser-Peace-Fraser-Columbia (approx.) and the Columbia-Kootenay 

 2,650 feet. 



