202 THE ILLINOIS GLACIAL LOBE. 



river bed. Exposures of the older drift with the capping of white clay were 

 also noted in northern Cumberland County, along Avestern tributaries of 

 the Embarras River. 



Records of several wells in the vicinity of Lerna were obtained in 

 which no rock was entered at a depth of 100 feet, and one boring reached 

 a depth of 132 feet without striking rock. A larg-e part of the drift appears 

 to belong to the Shelby ville sheet. 



At Mattoon a coal shaft has the following section, as reported in the 

 Geologv of Illinois, which suggests that the Shelbyville sheet there may 

 be but a few feet in depth : 



Section of drift in a coal shaft at Mattoon, Illinois. 



Feet. 



Surface soil 5 



Yellow clay 8 



Sand (blue) 3 



Hardpan (Illinoian ?) 35 



Sand and gravel 17 



Blue clay and gravel '. 38 



Total drift 106 



At Windsor the town well has a depth of 127 feet and does not reach 

 rock. It is reported that a soft blue till sets in within 10 feet of the surface, 

 and extends to a depth of 90 feet. Here a hard, stony, brown clay, prob- 

 ably Illinoian, was entered, which changed within a few feet to sandy 

 water-bearing clay, and the amount of water gradually increased until a 

 good supply was obtained at a depth of 127 feet. Several prospect borings 

 for water have been made in Windsor by Jerry Linn ville, in one of which a 

 black muck was found at about 100 feet. This was probably at the base 

 of the Shelbyville drift sheet, and at the same horizon as the brown clay 

 struck at 90 feet in the town well. A slight amount of gas was found near 

 the level of this muck. It appears to have been at a level slightly lower than 

 the muck, and hence is less likely to have been derived from it than if 

 found at a higher level. Possibly its source is from underlying shale. It is 

 thought that one boring readied the shale at 170 feet. 



Along the Kaskaskia Valley in the vicinity of Shelbyville there are 

 exposures of the Illinoian drift, capped by a white clay similar to the 

 surface white clay of the outer-border district, but here overlain by about 

 20 feet of till of the Shelbyville sheet One exposure is found within the 



