142 THE ILLINOIS GLACIAL LOBE. 



The peat in one instance is found to have a thickness of 30 feet (in a well 

 on Dr. Ludden's farm, 5 miles south of Clayton), and not infrequently has 

 a thickness of 5 or 10 feet. Few wells have been sunk below this lower 

 soil horizon, but these indicate that the drift may extend in places to a con- 

 siderable depth In several cases, however, the bottom of the drift was 

 reached within 20 or 30 feet below the lower soil. Both sheets of drift 

 beneath the Wisconsin are described to be of a brown or brownish-gray 

 color, and the writer was unable to learn of any distinguishing character- 

 istics. They are each described to be harder to penetrate than the overly- 

 ing Wisconsin drift. In its- surface exposures the Iowan is usually more 

 easily penetrated by a spade or auger than the Illinoian, and this fact may 

 seem to favor the view that the two sheets beneath the Wisconsin in Iro- 

 quois County are Illinoian and pre-Illinoian rather than Iowan and Illinoian. 

 However, the information is so meager and the character of the observa- 

 tions so imperfect that it can scarcely be decided from these records 

 whether the middle sheet is Iowan or Illinoian. The following data con- 

 cerning the three sheets in Iroquois Count}' will serve to set forth their 

 relative thickness : 



Clayton and vicinity. 



Feet. 



Upper or Wisconsin drift sheet 60 or 70 



Middle drift sheet 30 or 35 



Lower drift sheet 45+ 



Ash Grove timber belt. 



Feet. 



Upper or Wisconsin drift 55 or 60 



Middle drift sheet 30 or 40 



Lower drift sheet 50+ 



Crescent City and vicinity. 



Feet. 



Upper or Wisconsin drift sheet 60 



Middle drift sheet 15 or 20 



Lower drift sheet 70+ 



Onarga and vicinity. 



Feet. 



Upper or Wisconsin drift sheet 50 or 60 



Middle drift sheet 30 or more 



Lower drift sheet 175+ 



Oilman and vicinity. 



Test. 



Upper or Wisconsin drift sheet 75 



Middle and lower drift sheets 120+ 



