446 OSCAR H. HERSHEY 



The ridge ends abruptly on the edge of the main valley at a 

 height perhaps 300 feet above the river. A small ditch passes 

 around the point not far below the brow of the hill and its bank 

 exposes the glacial debris. Proceeding east along the ditch, 

 one comes to a fresh ravine leading down the steep slope from 

 the ditch. It exposes 100 feet in thickness of horizontally- 

 stratified, fine, subangular, brown gravel and reddish-brown silt, 

 like in the high bank above Conzetti's mine, discussed in the 

 paper before cited ; but here containing a number of granite 

 bowlders, all rotten even when 3 feet in diameter. It is evident 

 that this glacier dammed the valley and formed a pond 300 feet 

 deep, in which the fine gravel and silt accumulated, but right 

 here along the edge of the moraine, granite erratics slid from 

 the glacier into the pond. 



Two hundred feet farther east along the ditch we seem to be 

 completely beyond the limit of the glaciation as the bank thence 

 for a long distance shows only residuary debris. 



Remnants of the terminal moraine occur on the north side of 

 the valley, opposite the ends of the lateral moraines and con- 

 necting these two points, a distance of about 500 feet. Scat- 

 tered bowlders reach a height of several hundred feet, but hardly 

 high enough to explain the damming of the valley above and 

 formation of the stratified gravel and silt by the moraines alone. 

 Apparently the silt and gravel reached their upper levels by 

 actual ice-damming. 



Returning now, to the head of Cooper's flume, we will take up 

 Cooper's channel, here marked by a rock bench 70 feet above 

 the river, and trace it up stream. By reason of the high grade 

 of the present river, the old channel reaches the stream level 

 about 400 feet up stream, and the present rock canyon ends at 

 that point. From here up the valley is comparatively broad, is 

 encumbered by huge bowlders (the residua of the eroded glacial 

 deposits) and no bed-rock shows in the south bank for some dis- 

 tance. From here up the old channel is buried under the present 

 river-bed and passes out of the discussion. 



The connection of Channel C with the maximum extension of 

 the Brown's Gulch glacier seems sufficiently definite. This gla- 



