RIVER TERRACES AND GLACIAL SERIES 443 



floor shown to be a stream channel. But this rock floor is lOO 

 feet above the river. The old channel may have descended very 

 rapidly at this point, although it is more likely that it is one of 

 the higher channel surfaces in Cooper's mine that is represented, 

 and that the deep channel passed up through the gorge. 



The channel on the south of the gorge is preserved for about 

 500 feet, and is covered by a mass of angular local debris whose 

 surface forms a sloping terrace with outer edge several hundred 

 feet above the river. From where this channel issues from the 

 bank, for fully half a mile up the river, the old and new courses 

 are coincident. But the level of the old channel floor is marked 

 by a change from the precipitous canyon wall to a gentler and 

 less rockier slope above, with an occasional granite bowlder at 

 this level. 



On the north side of the river, about one-fourth mile from 

 the lower end of Cooper's flume, there is a cutting through a 

 narrow point, on which occurs a remnant of gravel about 

 30 X 100 feet in extent and 5 to 20 feet deep. It rests on a 

 rock slope of about 45° and ranges from the level of the flume, 

 about 300 feet above the river, to 75 feet higher. The bed-rock 

 surface under the gravel is broken and decayed and somewhat 

 irregular. It does not seem to be in the form of a distinct chan- 

 nel. The material abounds in large granite bowlders which are 

 thoroughly rotten to the core, even one 6x8 feet. The 

 remainder of the rock fragments are mainly angular and sub- 

 angular hornblende schist up to bowlder size. Aside from the 

 granite bowlders, very little of the material is rounded. It is 

 embedded in a sandy clay, inclined to a reddish color. There 

 are no apparent lines of stratification. It looks more like .a 

 glacial than a stream deposit. It is very old and rotten and a 

 mere remnant of a once more extensive formation. The lowest 

 portion is over 150 feet above the floor of Cooper's channel, the 

 surface of which, as already described, forms a terrace on the 

 opposite side of the river. This gravel contains an 8-inch and a 

 2-foot serpentine bowlder, and represents the serpentine-bearing 

 horizon, down the river. 



Higher on the same slope, by the " Cape Horn " trail, about 



