146 THE CANADIAN NATURALIST. [Vol. viii. 



River, where the waters are pure and limpid. There may, 

 however, be deeper latent causes ; but I suggest these which 

 appear to me the more obvious. Yet even under this view there 

 is a difficulty ; for on Fraser River, where a similar condition 

 of the water might be argued to produce a similar effect, no case 

 of the kind has ever appeared. The Saskatchewan, like the 

 Mackenzie, the Churchill, and I believe all the rivers falling 

 into Hudson's Bay, is destitute of Salmon. 



The West Side of the Rocky Mountains. — This region must 

 be noticed very briefly. The lengths of the Fraser flowing 

 entirely, and of the Columbia partially, within the limits of 

 British Columbia, are respectively, including windings, the 

 former about 800, the latter 1,200 miles ; the approximate 

 areas of drainage being, by the Fraser 66,400, by the Columbia 

 215,900 square English miles. Immediately on crossing the 

 Rocky Mountains by the heads of the latter river, after the 

 autumn frosts have already invaded the eastern side, a great 

 improvement in the temperature is perceptible, while all the 

 external evidences of a warmer climate appear. Descending the 

 Grande Cote, within twenty miles of the summit, huge trees of 

 the " Red Cedar" {Thuja gigantea of Nuttall) are for the first 

 time seen ; and lower down the timber and other vegetation are 

 also different. About Colville the Columbian Red Pine (Pimm 

 ponderosa) and the Larch (Larix occidentalis) of large dimen- 

 sions are seen — the latter confined apparently to the vicinity of the 

 49th parallel, the former extending north-westward nearly to the 

 great divide beyond the Thompson, and westward to the head 

 of Anderson Lake near the Coast Range. About one hundred 

 miles below Colville the borders of the great Columbia Desert 

 are reached ; extending thence, with occasional oases, as far as 

 the Dalles of the Wascopum ; and by the Snake River finally 

 meeting with the deserts of the Youtah. Artemisia, the Cactus, 

 and other congenial plants, characterise the whole of this arid 

 tract ; while the more favoured spots, near the water-courses, 

 yield abundant pasture of rich Bunch-grass, and are extremely 

 fertile. At one point upon the Okinagan River, this arid waste 

 extends for a short distance into British Columbia ; and I do 

 not question that, acting as a great reservoir of heat, the vast 

 expanse exercises a marked influence on the temperature of the 

 whole vicinity ; and to the extension of this influence, partly, in 

 conjunction with the warm winds from the Pacific, I ascribe 



