■RIVER TERRACES AND GLACIAL SERIES 445 



ing into the steep slope of the mountain above. The bowldery 

 ridge is a glacial moraine. Its steep inner slope is largely due 

 to erosion by the river. It obstructed the old channel and 

 caused the erosion of the canyon. 



The surface of the bowlder deposit rises toward the southeast 

 at the rate of 10 to 20 feet in 100 feet, and soon attains a 

 height of over 500 feet above the river. It has, at first sight, 

 the appearance of a typical lateral moraine, with steep inward 

 (ice-ward) slope, then a flat surface 30 to i 50 feet wide and then 

 the smooth slope of the unglaciated mountain. This moraine 

 leads to the mouth of a deep gulch (Brown's Gulch) which 

 comes down steeply from the mountain on the south and enters 

 the river valley not far above the head of Cooper's flume. A 

 glacier headed in a basin in the granite at the head of the gulch, 

 extended down the steep, narrow gulch and out into the valley 

 of the Salmon River. This may be called the Brown's Gulch 

 glacier. 



The moraine surface at the mouth of the mountain gulch 

 is about 200 feet above the creek. The gulch is so sharply 

 V-shaped as to indicate considerable postglacial erosion. From 

 here up the bowlders on the west are simply scattered over the 

 slope of the mountain, bed-rock appearing frequently, and in 

 many places there is little to indicate a glaciated gulch. 



The corresponding "lateral" moraine on the east side attains 

 prominence farther up the gulch and quite likely extends with- 

 out a break to the glacial basin at the head. The appearance is 

 that this supposed lateral moraine really represents the floor of 

 the glacier and that of the stream has cut a V-shaped gulch 150 

 to 200 feet deep and partly in hard rock, since the disappear- 

 ance of the ice. This is an amount of erosion that I am not 

 accustomed to for the time since the maximum extent of the 

 Wisconsin glaciers. 



Following the east moraine down, I find it finally separating 

 from the general mountain slope as a broad, transversely flat- 

 topped, independent ridge. This gradually diverges from the 

 west moraine, showing that the glacier, upon entering the main 

 valley, spread out like a fan. 



