268 



KUbmetres not uniformly canyon-like throughout, but 

 is rather a succession of narrow gate-like con- 

 strictions connecting somewhat broader expan- 

 sions of the river. Through these narrow 

 passages the water rushes with greatly increased 

 velocity and tremendous force, swirling and 

 eddying from wall to wall and forming such a 

 confusion of currents as to make the navigation 

 of these gaps exceedingly hazardous in low 

 water and absolutely impossible in a high 

 stage. Hell's Gate, Black Canyon, and Cha- 

 quama Canyon are among the most remarkable 

 of these constrictions, the first and last men- 

 tioned each having a width of about 200 feet 

 (61 m.). 



For almost its entire length the gorge is cut 

 into granitic rocks of medium acid composition, 

 the predominating type of which is a gneissic 

 granodiorite. Though the larger proportion 

 of these rocks is of Jurassic age, some are con- 

 siderably younger and from their structure 

 and lack of metamorphism are probably 

 of early Tertiary age. These younger rocks 

 are easily identified even from a distance by 

 their well developed and regular places of 

 jointing; because of this characteristic they 

 have been used to a large extent by the rail- 

 way companies in the lining of tunnels and in 

 other types of masonry. 



Skuzzy creek, a roaring torrent, plunges out 

 of a hanging valley into the Fraser river at 

 China Bar near the upper end of the gorge. 

 On the opposite side of the river in a steep 

 bluff can be seen a network of light-coloured 

 aplite dykes traversing the granodiorite. The 

 stream here runs in an almost direct line 

 southward, gradually becoming narrower until 

 two miles (3-2 km.) below, it rushes through 

 Hell's Gate between vertical walls of massive 

 jointed granodiorite. 

 43 m. Spuzzum — Alt. 395 ft. (118 -8 m.). Beyond 



69'2jcm Hell's Gate the railway enters a succession 

 of tunnels cut through projecting bluffs of rocks 

 in a moderately wide part of the valley, on 



