284 THE ILLINOIS GLACIAL LOBE. 



The older deposits of drift appear to be more variable than the Wis- 

 consin sheet within the area under discussion. The till differs from, that of 

 the Wisconsin sheet in being much harder to penetrate and in being of a 

 gray or brown color rather than blue. It appears to contain numerous 

 pockets or intercalated beds of gravel or sand, for strong wells may usually 

 be obtained in it in localities where the Wisconsin drift does not supply a 

 sufficient amount of water. The outcrops of these older deposits along the 

 ravines or valleys tributary to the Illinois often expose a cemented gravel, 

 in beds a few feet in thickness and a few rods in extent. These beds 

 appear to lead through the till in horizontal bands of limited width; pos- 

 sibly they are buried stream beds or valley gravels formed between the 

 retreats and advances of an oscillating ice margin. The exposures are 

 insufficient to afford a clear idea of their extent and connection. It seems 

 not improbable that these beds which are cemented at outcrops along the 

 valleys become open textured and water bearing where unexposed. There 

 are places along the Illinois Valley and its tributaries where the older drift 

 appears to be composed very largely of sand and gravel, but as a rule the 

 till predominates. The structure of the drift in each of the counties com- 

 prised in this intermorainic area is shown in some detail in the discussion of 

 wells which accompanies this report, 



KANEVILLE ESKER AND DELTA. 



One of the most interesting eskers noted in Illinois is found in the 

 southern part of Kane County. Its eastern terminus is about 3 miles west 

 of the city of Aurora, and its western terminus is near the village of Kane- 

 ville, from which the esker has received its name. The esker occupies a 

 trough-like valley cut in glacial deposits. It is probable that the valley 

 was formed by the same stream which deposited the esker, since they coin- 

 cide so nearly in trend and position. At the western end of this valley there 

 is an extensive delta, apparently built up by the same stream. The trough- 

 like valley is now traversed by Blackberry Creek in the reverse direction 

 from the supposed flow of the glacial stream which produced the excava- 

 tion and formed the esker and delta. The valley occupied by the esker is 

 much larger than that of the lower course of Blackberry Creek, its dimen- 

 sions being about 1 mile in width and 30 feet in depth, while the valley of 

 the creek below the point where it leaves this trough is scarcely 20 rods in 



