so THE ROYAL SOCIETY OF CANADA 



descending quickly in a series of rapids or short falls to join the main 

 stream. 



Both Anderson and Nahatlatch rivers join the Fraser virtually 

 at grade, but they emerge through narrow rock walled canons several 

 hundred feet in depth which are impassable either on foot or by boat. 

 Higher up the streams their valleys widen and become more flaring 

 and at the same time the grade lessens. 



When viewed from points of vantage on the opposite slope of 

 the Fraser river, these streams are seen to course through hanging 

 valleys that have been so notched by stream action that they now 

 make entry into the main stream virtually at grade. From certain 

 points of observation the notch is not noticeable and the only valley 

 visible is the broad upper valley, the floor of which is 400 or 500 feet 

 above the bed of Fraser river. 



The above feature is typical of a great many of the valleys 

 joining Fraser valley in the mountain portion of its course, and while 

 some of the larger streams have already notched the broader upper 

 valley floors, many of the smaller streams have not the power to do 

 so and plunge over falls before joining the main stream. This feature 

 will be referred to again in describing other section of the valley. 



Anderson River to Yale 



The middle section of the mountain portion of Fraser valley 

 extends from the mouth of Anderson river to Yale, a distance of 

 about 24 miles. This section is the gorge and is often popularly 

 referred to as the canon though the whole mountain portion from 

 Lytton to Hope more correctly deserves that name. In this section 

 the valley contracts to less than half the width it had above and its 

 slopes become steep and rocky. In contrast to the densely forested 

 even slopes of the valley above Anderson river the slopes of the 

 gorge are sparsely forested and irregular. Steep cliffs and bare rocky 

 knobs are common and even on the lower parts gravel benches are of 

 rare occurrence. 



The gorge is in reality made up of a succession of short narrow 

 box shaped constrictions within a larger canon, and at each of these 

 constrictions the width of the stream is greatly reduced and rushes 

 with tremendous violence between walls of rock that are vertical for 

 100 feet or more in height. In the intervening stretches of river 

 between these constrictions the width of the stream is greater, the 

 slopes are not so abrupt and there is room for the accumulation of 

 some gravel deposits. 



