46 



P'rom the station and railway, it is visible and easily distinguished from 

 the bordering prairie lands by its forested surface. 



This ridge exceeds two miles in length and varies in height from a 

 few feet at the ends to fifty or sixtj^ feet along the main body. Its sides 

 slope at angles of 20'' to 35° away from the arching crest. Its height 

 is quite uniform, but few irregularities occurring in the whole length. 

 The base of the ridge is from twenty to thirty rods wide. 



An interesting observation is that the outside or convex sides of 

 bends have the steeper slopes, a fact bearing on the theory of stream 

 origin. 



The material is stream gravel assorted from the glacial drift arranged 

 in layers which slope to the southwest. This arrangement of the mate- 

 rial indicates stream action and shows the course of the stream that de- 

 posited the eslier. Excavations to obtain gravel for road making occur 

 at points x x x shown on the map and the characteristic structure is 

 shown in each. Mounds of gravel occur in line with the general trend of 

 the esker at each end. A chain of these elevations extends a mile from 

 the southwest end. 



The vallej', a half mile wide, comprising the esker trough, extends 

 from the vicinity of South Raub station to the Independence-Darlington 

 moraine near Sugar Grove, where it crosses the divide and connects with 

 the valley of Shawnee Creek, which flows west. The trough is how trav- 

 ersed by the Little Wea Creek, which flows northeast, just the reverse 

 of direction followed bj^ the stream which built the esker. This creek 

 rises at the gap through the moraine at Sugar Grove and it leaves the 

 trough by a deep narrow valley through another moraine at a little dis- 

 tance north of South Raub. Mounds of gravel near the station and fur- 

 ther to the northeast may lie in the course of the sti'eam that deposited 

 the esker. 



The problem of the slope of the esker trough opposite to the direc- 

 tion of the sub-glacial stream that originally corraded it suggests the 

 explanation of hydrostatic pressure in the tunnel. 



Ihe cause of the deposit of gravel and sand as an esker may be re- 

 lated to the reverse slope of the esker trough causing the stream to grade 

 up to a slope line in the opposite direction, which would carry it over 

 the divide at Sugar Grove. 



