110 GEORGE MERCER DAWSON ON THE 



between Eraser and Stuart Lakes, already mentioned, show a succes- 

 sion of water-marks in some places to an elevation of at least 3800 

 feet. They stand in a low country as spurs or outliers in the basin 

 of the White Silts. Mr. Smith, of the Canadian Pacific-Railway 

 Survey, gives the general height of the highest well-marked beaches 

 of the Eraser and its tributaries, which he has observed in different 

 localities more than 150 miles apart, at from 2400 to 2500 feet. 

 To this stage the Eraser and Erancois Lake-terraces no doubt belong. 



Some beaches, remarkable from the nature of the material com- 

 posing them, occur on the direct trail to Fort George, between Tsa- 

 whuz Mountain and that place. The aspect of the country from 

 Tsa-whuz, and its general northern slope, have already been described. 

 In gradually descending the slope, towards the basin of the White 

 Silts, Boulder-clay, previously forming the surface, nearly disappears, 

 and is replaced or covered by shingly deposits composed of well- 

 rounded stones, which are for the most part very compact quartzites 

 of various pale tints, almost precisely resembling the quartzite 

 drift formerly described as occurring on the higher levels of the 

 plains east of the Rocky Mountains*, and would appear probably 

 to have been derived from the same series of rocks. The shingle 

 beaches or mounds have no very uniform general direction, but form 

 low gently-swelling undulations which bear forests of scrub-pine, 

 separated by swampy hollows densely filled with black spruce. The 

 shingle-beds may, T think, be pretty safely correlated with the thick 

 gravelly deposits seen at a lower level near Eort George, and, if so, 

 probably represent the margin of the White-Silt sea at one stage. 

 Their approximate average elevation may be stated as 2100 feet. 

 An interesting question occurs with regard to the origin of their 

 materials. No rocks similar in character to their quartzites have 

 been found in this part of British Columbia. It is probable that 

 they have been far transported across the northern low country, 

 or derived from exposures on the northern spurs of the Cariboo 

 range. 



The materials of the lower terraces of the river-valleys, though 

 sometimes interesting, are more local in their character, and not 

 significant in tracing the origin of the drift-deposits as a whole. The 

 terraces in the bottoms of the valleys, and nearest the bed of the 

 stream, usually show the coarsest gravels. The rivers being in 

 almost all cases rapid streams, subject to great floods in the early 

 summer, constant transport of material is still going on in their 

 channels ; and in consequence the river-gravels do not bear nearly 

 so close a relation to the local formations as those higher up the slopes 

 of the valleys and on the plateau. In passing in a canoe down those 

 parts of the Fraser which are considered navigable, one is constantly 

 struck by the peculiar sharp hissing noise caused by the grinding 

 and onward movement of the gravel in the river-bottom. This may 

 be heard in all the " riffles," or little rapids, even at low water, and 

 evidences the extensive transport and consequent corrosion in pro- 



* Quart. Journ. Geol. Soc. Nov. 1875, vol. xxxi. p. 616, and 'Geology and 

 Resources of the 49th Parallel,' p. 231. 



