190 GEOLOGY OF ILLINOIS. 



rotten carboniferous sandstone lias been quarried by the farmers, and 

 used for farm purposes. One well was walled with this material. The 

 wall decayed or rotted down, and the well caved in after it had been in 

 use for a series of years. On section 20, on Spring creek, in the town- 

 ship of Atkinson, there is a small stone quarry, but my notes on its 

 characteristics have been misplaced or lost. 



These are the best tracings I have been able to make of this bed of 

 sandstone. Its place in the geological section of the county seems to 

 be above the heavy, lower, workable seam of coal, sometimes separated 

 therefrom by shales and limestone, and sometimes appearing to rest 

 almost directly on the coal. Its position is by no means constant, how- 

 ever. It is also almost unfossiliferous. A few tracings of Calamitcx 

 and Lepidodendron were the only organic remains I could find in this 

 deposit. 



Limestone of the Lower Goal. The " cap rock " over some of the coal 

 mines is a dark-colored, almost black, and sometimes shaly limestone, 

 in which is frequently found a small and beautiful Productus. The coal 

 seam at Aldrich's mine is overlaid by a thin stratum of shale, which is 

 capped by a hard, blue, shelly limestone. This limestone is quarried in 

 small quantities here, and sold at a high price to neighboring fanners. 

 At Cleveland, the coal seam is stripped of its superficial covering over 

 several acres in extent. The limestone is more massive here, not quite 

 so dark in color, and rests almost directly upon the coal. Hundreds of 

 cords of it are stripped from the coal. The deposit is from one to two 

 feet thick, and great quantities are sold at remunerative prices. Large 

 numbers of the heavier stones thus quarried are to be used in the rail- 

 road bridge to be built across Kock river at this place. Immense slabs, 

 more than a foot in thickness, obtained at the lower opening, are piled 

 over an open space, ready to be transferred to the piers in the river. 

 Some of these show signs of crumbling round the edges, as if the tooth 

 of time had gnawed into their surface. We doubt whether they will 

 prove entirely satisfactory for railroad masonry. Above this massive 

 strata, and separated from it by from four to seven feet of shales and 

 black, hardened carbonaceous mud, is another strata of lighter-colored, 

 thin-bedded, shaly limestone, which is also corded up and sold for 

 lighter masonry. The supply of stone thus obtained at these coal mines 

 is very considerable. About Minersville the same limestone is found 

 iii connection with the coal seam, and a section here would be very similar 

 to the Coal Valley section, except the sandstone above spoken of. 



Along the banks of Geneseo creek, a little south-west of the city of 

 Geneseo, there is a very curious outcrop of stone, which has been worked 

 to some extent in former years. The top of the stratum is a sandstone 

 for about two feet in depth. It then gradually changes into a blue, com- 



