BOCK ISLAND COUNTY. 



The Coal Measures all over the county are covered with a deep deposit 

 of drift-clays. At Camden, Carbon Cliff, and east of Bock Island city, 

 this drift-clay is from forty to seventy-five feet thick. 



A section made at the Coal Valley coal mines, south of Bock river, 

 and seven or eight miles in the interior of the county, gives the follow- 

 ing section : 



Xo. 1. Reddish and yellowish drift-days 30 feet. 



No. -. Silicious shale --10 



Xo. 3- Band of chert 2 



Xo. 4. Dark bluish-gray, silicions limestone, shaly at the top and massive at the hottom 10 to 18 



Xo. 5. Bituminous shale 1 " 3 



Xo. C. Coal No. 1 . avera ge thickness . , 4J 



Xo. 7. Fire clay, passing downward into shale 12 



Up a ravine in the bluffs, midway between Cainden and Andalusia, a 

 dark colored massive sandstone is quarried to some extent. The out- 

 crop is about ten feet thick, and the stone is clouded and stained with 

 iron. Below Andalusia, near the mouth of Coal creek, a little stream 

 which conies down from the bluffs, is an outcrop about twenty feet 

 thick, of a massive, close-grained, umber-colored inagnesian limestone, 

 which has been quarried to a considerable extent. From thence down 

 the bluff line to Drury's lauding, both sandstones and limestones show 

 themselves low in the hills, but none of these outcrops have been 

 worked to any extent- Opposite Mnscatiue, a somewhat massive sand- 

 stone outcrops, which has been worked, and in which has been found 

 several fine specimens of Lepidodendron. Near Copperas creek, in the 

 eastern part of the township of Drury, there is also a sandstone quarry 

 worked to some extent. 



South of rock river, the Coal Measures are more regular and more 

 extensively developed than in the northern part of the county, and at 

 least three of the lower seams were recognized. At Coal Valley, and 

 near the base of the hills in the vicinity of Andalusia, coal Xo. 1 may 

 be seen with its black shale and limestone roof, and its characteristic 

 band of chert ; and further back in the hills of Coal creek, Walnut 

 creek and on Big run, coals Xo. 2 and 3 were identified, and have both 

 been opened, and are now worked for the supply of the local market. 

 Nevertheless, more than nine-tenths of all the coal mined at the present 

 time in this county comes from the lower seam. The Coal Valley mines 

 are among the oldest worked in this portion of the State, and to the 

 present time they have furnished the largest portion of the coal used at 

 Bock Island and Moliue, and the country further north. Where fully 

 developed as a single seam, its thickness is about five feet, but it is 

 sometimes divided by a shaly parting, and the two divisions become too 

 widely separated to be worked together. It has an excellent roof of 

 black shale and hard blue arenaceous limestone, overlaid by a baud of 



