176 GEOLOGY OF ILLINOIS. 



other. Over this slate or stone root is a body of indurated clay. The 

 coal seam is underlaid by a bed of indurated fire clay. This under-clay 

 contains some large nodular masses of limestone, some of them kidney 

 shaped, and some of them round, and all flat. Fine impressions of fern 

 leaves have been found in the roof slates, if the statements of the 

 miners are to be relied on. 



The coal seam itself ranges from four and one-half to five feet in 

 thickness. A thin seam of light colored fire clay runs through the coal 

 seam near its middle ; near the bottom some seams of shale also exist 

 in the coal. This fixes the identity of the coal with that mined at 

 Wataga, Galva, Kewanee, and the upper Peru coal. Prof. LESQUE- 

 KEIIX says that the Wataga coal is the same as the middle Peru seam. 

 I have little doubt of the Galva, Kewanee and Sheffield coals being 

 identical with the Wataga seam. The clay and slate partings in the 

 coal are characteristic of this seam. On the old section of the coal 

 seams of the State this seam would belong to coal No. 11 ; but accord- 

 ing to Prof. WORHEN'S reconstructed coal section, as published in the 

 third volume of the Geological Survey of the State, it would belong to 

 coal No. 6. 



The following description and analysis of this coal is taken from the 

 Eeport on Illinois Coal, made by J. G. NORWOOD and his assistants : 



Coal bright, hard, compact ; fracture inclining to conchoidal ; layers thin, and separated with very 

 minute seams of carbonaceous clod ; contains a few thin seams of carbonate of lime ; slacks on ex- 

 posure to the weather. 



Specific gravity 1 . 186 



Loss in coking 47 . 5 



Total weight of coke 52. 5 



100.0 



ANALYSIS : 



Moisture 7.0 



Volatile matters 40.5 



Carbon in coke 47.5 



Ashes (white) 5.0 



100.0 

 Carbon in the coal 53 . 4 



As a matter of general interest I also give the analysis and descrip- 

 tion of this same coal, made some years ago, by Professors PORTER 

 and B. SILLIMAN, Jr., who occupied the chairs of Analytical and Agri- 

 cultural, and General and Applied Chemistry, in Yale College, at the 

 time of making the report, from which I take the following extract: 



Subjected to a moderate red heat, it yielded in a hundred parts, as an average of two trials 



Volatile matter 29 . 32 



Fixed carbon 64 . 90 



Ash 5 78 



100.00 



