Rocky Mountains^ 81 



degree, to his descriptions, and as we had been careful to 

 follow the general direction of the course pointed out to us, 

 it was probably his intention to deceive. 



Our course, which was a little east of south, led us across 

 several extensive vallies, having a thin dark-coloured soil, 

 closely covered with grasses and strewed with fragments of 

 greenstone. Descending, towards evening, into a broad and 

 deep valley, we found ourselves again immured between 

 walls of gray sandstone, similar in elevation and all other 

 particulars to those which limit the valley of Purgatory 

 creek. It was not until considerable search had been made, 

 that we discovered a place where it was possible to effect 

 the descent, which was at length accomplished, not without 

 danger to the life and limbs of ourselves and horses. The 

 area of the valley was covered with a sandy soil, in which 

 we again saw the great cylindric Cactus, the Cucumis, and 

 other plants common to the sandy districts, but rarely found 

 in the scanty soils of the Trap formation. Pursuing our 

 way, along this valley, we arrived, towards evening, at an 

 inconsiderable stream of transparent and nearly pure water 

 descending along a narrow channel, paved with black and 

 shapeless masses of amygdaloidal and imperfectly porphyri- 

 tic greenstone.* This was the first stream we had, for a 

 long time, seen traversing rocks of secondary formation, 

 whose waters were free from an impregnation of muriate of 

 soda and other salts. From the very considerable magni- 

 tude of the valley, and the quantity of water in the creek, it 

 is reasonable to infer that its sources were distant at least 

 twenty miles to the west, and the purity and transparency 

 of its waters afford sufficient evidence that it flows princi- 

 pally from a surface of Trap rocks. 



* From a subsequent comparison of the direction of several water courses 

 which descend from this elevated district, we have been induced to con- 

 sider the creek mentioned in the text as one of the most remote sources 

 of the great northern tributary of the Canadian river. 



VOL. 11. 11 



