78 



GEOLOGY OF ILLINOIS. 



and when fully developed, attains a thickness of eight hundred or a thousand 

 feet in this State. Only about two hundred and fifty feet of the lower portion 

 of the Coal Measures are found in this county, which may be illustrated by the 

 following section, showing the general arrangement and comparative thickness 

 of the strata : 



10 to 15 feet. 



3 to 6 feet 



2 to 4 feet. 



8 to 10 feet. 



60 to 80 feet. 



2 to 6 feet. 



4 to 8 feet. 



12 to 15 feet. 



4 to 6 feet. 



15 to 30 feet. 



30 to 40 feet. 



1 to 3 feet. 



15 to 25 feet. 



Brown sandy shale. 



Compact gray limestone. 



Bituminous shale, with concretions of limestone. 



Coal seam No. 4. 

 Fire clay and septaria. 



Sandstone and shale. 



Bluish gray arenaceous limestone. 

 Bituminous and argillaceous shales. 

 Coal seam No. 3. 



Sandy and argillaceous shales. 

 Gray limestone. 



Sandy and argillaceous shales. 

 Coal seam No. 2. 



Sandstone and shale. 



Coal seam No. 1. 

 Fire clay. 



Sandy shale and conglomerate sandstone. 



