346 THE NORTH-WEST PASSAGE BY LAND. 



itself. Several hundred miles above, each, of these 

 rivers expands into a broad and deep stream, more 

 than a quarter of a mile in width; yet at the 

 Canons the vast accumulation is confined in a 

 channel of less than fifty yards wide. Huge rocks 

 stand up in the middle of the stream in several 

 places, the waters escaping by a constricted passage 

 on either side. 



The mass of the Cascade Range is grey granite, 

 and the sides of the chasm show beautiful sections 

 of the rock, plaided with protruding seams of white 

 quartz, the harder rock having been worn away by 

 the action of the water, which the soft quartz seems 

 to have resisted. In many cases the opposite walls 

 of the chasm correspond in a most remarkable 

 manner, so that they appear as if they would fit 

 accurately if placed in apposition, suggesting forcibly 

 that they had been portions of the same solid mass 

 violently rent asunder. As we looked on this and 

 wondered, an explanation of the formation of the 

 terraces occurred to our minds. At one time the 

 valleys of the Thompson and Eraser were occupied 

 by a succession of lakes, the Cascade Eange being 

 the barrier which dammed in the enormous volume 

 of water, and the highest tier of terraces marking 

 the level to which it rose. The tops only of the 

 lower mountains appeared at this time as rounded 

 islands above the surface. By some means — perhaps 

 some grand convulsion of Nature — the embankment 

 of this huge reservoir broke down, the waters par- 

 tially escaped, and the lakes were drained down to 

 the level of the middle tier of benches. Twice more 



