THE BLOOMINGTOK MORAINIC SYSTEM. 287 



"Wells in the delta penetrate 10 to 15 feet of sand before entering till. The 

 esker is opened at numerous points, and there is usually 3 or four feet of 

 coarse gravel at the surface, beneath which is a finer gravel. In places the 

 bedding is found to have a dip toward the northwest, nearly in line with 

 the general trend of the ridge. The coarse gravel curves over the ridge, 

 covering slopes as well as crest. The pebbles are principally limestone 

 and are usually well rounded. 



There are a few short gravel ridges and knolls east from the end of 

 this esker in sees. 4, 11, and 12, but they do not seem to be definitely 

 connected with one another or with the esker. Their trend, like that of the 

 esker, is ESE.-WNW. The same system of glacial drainage which formed 

 the esker may have been influential in forming these knolls and ridges. 



Mention should also be made of a chain of gravelly knolls which 

 follows a tributary of Somonauk Creek in southeastern Clinton Township 

 (T. 38, R. 4 E.), Dekalb County. Though following the creek border 

 closely, they are evidently not the result of erosion by the creek, for they 

 stand above the general level of the bordering plain. They range in height 

 from 10 to 25 feet. Their width is usually 15 to 30 rods and the length 

 varies from one-fourth mile or less to fully one-half mile. They are chiefly 

 on the south border of the stream, but two were observed on its north 

 border. They are not strictly in line with each other, though a belt a half 

 mile wide would include the entire system. The length of the system is 

 about 4 miles, the western end being 2£ miles south of Waterman and the 

 eastern end at Somonauk Creek Valley in the southwest part of Squaw 

 Grove Township. One of these knolls has an extensive gravel pit in which 

 the following beds are exposed : 



Section in gravel pit on knoll in Clinton Township, Delcalb County, Illinois. 



Feet 



Brown clay with a few eherty pebbles 4 



Coarse gravel, mainly limestone pebbles 6 



Fine gravel and sand in alternate layers, each 6 inches or more in thickness 4 



Several other small excavations have, been made in these gravel knolls 

 which show a section similar to the above. The stratification in every case 

 is nearly horizontal. 



There are also knolls of a different type found on this plain which 

 include much till as well as assorted material. One of these knolls, situated 

 about 2 miles northwest of Leland, contains an extensive gravel pit which 



