10 GEOLOGY OF ILLINOIS. 



The Quaternary system is represented in this county by the alluvial 

 deposits of the river and creek valleys, the loess of the Wabash bluffs, 

 the gravelly clays and hard pan of the true drift, and the underlaying 

 stratified sands that are sometimes found immediately above the bed 

 rock. 



The drift deposits proper vary in thickness from twenty to seventy- 

 five feet_or more, the upper portion being usually a yellow gravelly 

 clay, with local beds or pockets of sand. The lower division is mainly 

 composed of a bluish-gray hard pan, exceedingly tough and hard to 

 penetrate, usually impervious to water, and from thirty to fifty feet in 

 thickness. This is underlaid by a few feet of sand, from which an 

 abundant supply of water can be had where it cannot be found at a 

 higher level. A common method of obtaining water on the highlands 

 in this county, where a sufficient supply is not found in the upper por- 

 tion of the drift, is to sink a well into the hard pan, and then bore 

 through that deposit to the quicksand below, when an unfailing sup- 

 ply is usually obtained. Bowlders of granite, sienite, trap, porphyry, 

 quartzite, etc., many of them of large size, are abundant in the drift 

 deposits of this county, and nuggets of native copper and galena are 

 occasionally met with, having been transported along with the more 

 massive bowlders, by the floating ice, which seems to nave been the 

 transporting agency of our drift deposits. 



Coal Measures . 



All the rocks found in this county belong to the Coal Measures, and 

 include all the beds from the limestone that lies about 75 feet above 

 coal No. 7, to the sandstone above the Quarry creek limestone, and 

 possibly coal Kb. 14 of the general section. These beds are all above 

 the main workable coals, and although they include a total thickness 

 of about 400 feet, and the horizon of five or six coal seams, yet none of 

 them have been found iu this county more than from 12 to 18 inches in 

 thickness. The following general section will serve to show the relative 

 position and comparative thickness of Coal Measures in this county : 



Ft. In. 



Ho. 1. Sandstone, nowhere found well exposed 30 to 40? 



No. 2. Quarry creek and Martinsville limestone 20 to 30 



No. 3. Shales, lower part bituminous 10 to 15 



No. 4. Coal (No. 14 ?) 1 



No. 5. Shaly Are clay 2 to 3 



No. 6. Sandstone and shale, some bands of iron carbonate 18 to 20 



No. 7. Bituminous shale 1 to 2 



No. 8. Coal (No. 14?) 1 to 1J 



No. 9. Clay shale and fire clay 4 to 6 



No. 10. Cinnamon-brown limestone 3 



No. 11. Coal (local?) 1 9 



No. 12. Sandy shales passing into massive sandstone below 40 to 50 



