KOCK ISLAND COUXTY. 221 



>eemed to be the most common, and Prodnctus lonyispinus. P. Prattenl- 

 (inus Chonctes mesoloba^aml a minute Trematopora were also observed, 

 but more rarely. 

 An analysis of this coal, by Mr. HENRY PKATTEN, former chemist of 



tlu- survey, uave the following results : 



Moisture. 70 



Volatile matter 36.7 



Carbon in coke 52-8 



Ash (white) 35 



100 

 Carbon in coke 55.3 



In the vicinity of Camden, on the western shore of Bock river, the 

 lower beds between the Devonian limestone and the Carbon Cliff' coal 

 are well exposed, showing an outcrop of a thin seam of coal just above 

 the river level. Above this thin seam there is a bed of coarse sand- 

 stone that sometimes passes into a sandy shale, above which is another 

 coal .seam two feet in thickness. The exposure here gives the following 

 section : 



Feet. 



Xo. 1 Sandy shale 30 to 35 



Xo. 2 Bituminous shale 4 



Xo. 3 Coal 2 



X.-. 4 Fire clay ."... 1 to 2 



Xo. 5 Sandstone and sandy shale 20 to 25 



Xo. 6 Thin coal 1 to 2 



Xo. 7 Shale 1 to 3 



Xo. 6 Devonian limestone. 



It is possible the upper seam in the foregoing section may be the 

 equivalent of the Carbon Cliff" coal, but I am inclined to regard both 

 these thin seams as intercalated beds underlaying the main coal of this 

 county. The seam at Carbon Cliff' and Coal Valley I consider as iden- 

 tical with the Seaville coal in Fulton county, and as Xo. 1 of the Illi- 

 nois river section, published on pages 5 and C of the third volume of 

 these I'eports. If this conclusion is correct, then the two thin coals in 

 the above section are the representatives of the sub-conglomerate coal 

 of Southern Illinois. The fact that they have nowhere heen found in 

 this portion of the State thick enough to be of any economical value, 

 except for local use, seems to favor this conclusion. The seam of so- 

 called cannel coal opened at the foot of the bluff near Colona, in Henry 

 county, and similar beds of highly bitumiuized shales that occur at 

 some other points in Hock Island county, may probably be referred to 

 the same horizon. In the bituminous shale overlaying the two-foot coal 

 seam in the above section, we obtained a few plants, among which the 

 Lepidodendron clypeatum was the most abundant. 



