GEOLOGY OF ILLINOIS. 



2 to 6 feet. 



3 to 4 feet. 



30 to 40 feet. 



40 to 60 feet. 



3 to 6 feet. 



1 to 6 feet. 



2 to 3 feet. 



20 to 30 feet. 



Dark blue silicious limestone, 

 filack eh ale. 



Coal seam No. 3. 



Argillaceous and sandy shales and sandstone. 

 Coal seam No. 2. 



Sandstone and shale. 



Bituminous limestone and band of ir^n ore. 

 Bituminous shale. 



Coal seam No. 1. 

 Clay shale or fire clay. 



Conglomerate sandstone and shale. 



These coals we have numbered from the bottom upward, and they will be 

 described in the same order. The only point in the county where we found 

 No. 1 sufficiently developed to be worked profitably, is in the vicinity of Sea- 

 ville, on the west side of Spoon river, at the crossing of the T. P. & W. rail- 

 road. The seam is worked here at two localities, one above the railroad bridge 

 and the other below. At these mines, the coal averages about three feet in 

 thickness, and is mined by tunneling into the bluff on the outcrop of the seam. 

 About a hundred yards to the westward of Mr. Harris's mine, below Seaville 

 Station, the seam is divided by a parting of shale, which soon thickens to the 

 westward, to three or four feet, and thus destroys the value of the seam for 

 mining. The roof consists of a bituminous shale, that ranges in thickness from 

 one to six feet, above which there is a bed of blue argillaceous limestone, from 

 three to six feet thick, forming, altogether, an excellent roof to the coal. 



The limestone at this locality, has afforded an interesting group of fossils, 

 several of which have hitherto been considered as especially characteristic of 

 tne upper coals. We obtained the following species at this locality: Athyris 

 subtilita, Retzia punctilifera, Spirifer cameratus, S. Kentuckensis, S- opimus, 

 Productus Prattenanus, P. nana, P. punctatus, Ortliis carbonaria, Terebratula 



