106 



GEORGE MEBCER DAWSON ON THE 



are occasionally seen on the Nechacco below Eraser Lake to rest on 

 false-bedded sands and clayey gravels (which may here probably re- 

 present a part of the Boulder-clay), and were observed to overlie in 

 one section a hard yellowish sandy clay with few stones. The White 

 Silts are also found to rest directly on denuded Tertiary beds and 

 other older rocks. In one section on the Lower Nechacco, their 

 relation to well-marked Boulder-clay is very distinctly seen (fig. 4). 



Fig. 4. — Section on Lower Nechacco River, 



x 9 S * ■;",'!!?•■, *fc 



' o,<r w* 



a. Soil. b. White Silt. 



c. Hard, grey, sandy clay, with rounded and subangular stones, some 



glaciated. 



d. Bluish sandy clay, with boulders and pebbles generally somewhat water- 



rounded, but nearly all glaciated more or less distinctly. 



The lowest bed exposed here is a hard bluish arenaceous clay, with 

 small boulders, and pebbles of all sizes, mostly more or less water- 

 worn, but nearly all showing traces of glaciation. There is little or 

 no appearance of stratification. This is separated by a distinct 

 horizontal line from the next layer, which is paler in colour, harder, 

 and somewhat more arenaceous, and charged with smaller pebbles 

 less evidently glaciated. The stratification is obscure. A second 

 sharp horizontal line separates this bed from the overlying White 

 Silts — hard pale arenaceous clays of the usual character, which be- 

 come disintegrated above to form the soil. 



The thickness of the White Silts must be over 100 feet in some 

 sections, and might very probably, if fully exposed, be found in 

 many parts to exceed 200 feet. The deposit shows a close general 

 resemblance to the thick argillo-arenaceous or loess-like material of 

 the plains of the Red River in Manitoba ; and very similar conditions 

 may probably have led to the formation of these beds in the two 

 localities. In both Manitoba and the Nechacco basin the material 

 is generally calcareous, and in both places it forms a most fertile 

 soil. In the Nechacco country it seems probable that the silts were 

 laid down in the bottom of a great lake, at a time when all the pre- 



