THE GLACIAL LAKE MISSOULA 379 



but less extensive deposits are developed at about the same elevation 

 in small canyons opening into the Clark Fork Valley between Ver- 

 milion Creek and Thompson Falls. 



East of the town of Stevensville a chain of rounded hills projects 

 westward some 5 or 6 miles into the Bitter Root Valley as a spur from 

 its eastern wall. This spur as a whole descends gradually from an 

 elevation of 6,500 feet to about 3,600 feet where its steeply tilted 

 quartzites disappear beneath the horizontally bedded clays, sands, and 

 gravels that form the valley terraces or "bench lands," which bear a 



Fig. 3. — Cowell buttes, looking southeast from sec. 6, tp. 9, N. — 19 W. Montana 

 Mer., showing the horizontal "trails" marked by rows of trees and shrubs. 



thin, clayey, fertile soil that as a rule is sharply defined from the 

 underlying gravel. The two symmetrically rounded outer knobs of 

 this spur are locally designated the Cowell buttes (Fig. 3). The 

 westernmost or first butte attains an elevation of 4,450 feet; the 

 second butte 4,750 feet, while the saddle between is 4,250 feet above 

 sea. The "trails" are well developed on the north and northwest 

 slopes of these buttes; the one at 4,200 feet elevation, above which they 

 apparently fail, is comparatively prominent and its cross-section 

 resembles that of a neglected road grade. The upper bank is broken 

 down but still definable, and the "road bed" eight or ten feet wide 

 merges gradually with the steeper slope below. The sandy soil 

 of this "road bed" is much deeper than that of the slope above and 

 contains numerous subangular to smooth rounded pebbles of quartzite 



