A "CORDILLERAN GLACIER'' IN BRITISH COLUMBIA 57 



down from the sides of these mountains, and gold was found in 

 gravel, and in bedrock beneath the gravel, in the bottom of these 

 valleys. Much of the gold occurred in preglacial, or Pliocene, 

 gravels that had been buried under a bed of massive bowlder 

 clay, holding many glaciated pebbles and bowlders. Immedi- 

 ately under the bowlder clay is often a stratified deposit of fine 

 quicksand or slimy silt, locally known as "slum," which is a seri- 

 citic silt that was washed from the decomposed surface of the rock 

 by glacial streams before the advancing glaciers themselves had 

 reached so far down the valleys. 



It was in the latter part of the month of May, and snow still 

 covered the tops of the ridges when I was in the district. Though 

 I saw many rock exposures, but one, a quartz vein, had preserved 

 glacial grooves and striae. This vein was on the north side of 

 the valley of Lightning Creek, one of the principal streams of the 

 district, and 1,000 feet above the bottom of the valley, or 4,800 

 feet above the sea. The markings ran N. 45° W. (true), which was 

 roughly parallel to the course of the valley, and the direction of 

 motion of the ice was quite clearly indicated by some rock cliffs 

 in the vicinity. 



As Lightning Creek Glacier moved down the valley it removed 

 loose material from the lateral slopes and deposited some of it in 

 the tributary gulches, thus covering the bottoms and the upper 

 sides of these gulches. After the glacier had retired and dis- 

 appeared, the drainage of the country was re-estabhshed in the 

 same gulches as before, but on top of the bowlder clay left by the 

 glacier and farther down the stream, so that when the gold miners 

 wanted to find the deeper preglacial channels of the gulches 

 they were obHged to explore for them in an easterly direction or 

 up the main stream. In the valleys of Slough Creek and Willow 

 River similar conditions prevail with regard to the lateral gulches, 

 as doubtless local valley glaciers also moved westward and north- 

 westward down these valleys. 



Well-marked moraines are present in many of the valleys, 

 conspicuous among them being a large hilly moraine in the valley 

 of Slough Creek below Jack-of-Clubs Lake, and a similar lumpy, 

 pitted moraine in Lightning Creek Valley below Stanley. 



