290 GEOLOGY OF ILLINOIS. 



Feet. In. 



No. 17. Fire-clay 2 6 



No. 18. Hard rock (probably limestone or calc. sandstone) 12 



No. 19. Shale. 5 



No. 20. Limestone --5 



No. 21. Black shale to 4 



No. 22. Coal (No. 5.)... ; 6 



266 2 



The coal here is similar in quality to that obtained from the shafts at 

 Yirden and Girard, and the mine is entirely free from water, and its 

 gangways as dry as though they possessed a water-proof covering. 



Bartel's shaft in the creek valley south of town was commenced at a 

 much lower level, and the coal was reached at a depth of about 210 

 feet. The coal in this shaft ranges from six to eight feet in thickness, 

 and has a good roof, composed of five feet of bituminous shale and five 

 feet of limestone. 



In the section given above of the Carlinville shaft it will be seen that 

 coal No. 6 is divided by a parting of shale six feet and a half in thick- 

 ness, while at the Virden shaft the parting consists of sandstone and 

 shale, and is six feet in thickness. In the last named shaft this seam 

 would be thick enough to be profitably worked, the two divisions being 

 in the aggregate four feet three inches in thickness, if united, but owing 

 to the great thickness of the parting the seam is valueless, as too great 

 an amount of labor would be required to remove the material separating 

 the two divisions of the coal. This seam has not yet been found in any 

 of the shafts in this county under such conditions as will permit of its 

 being worked successfully. The next seam, No. 7, although of sufficient 

 thickness, was found to be too soft and inferior in quality, and conse- 

 quently valueless. Coal No. 8 appears to be the equivalent of the 

 eighteen-iuch coal outcropping on the breaks of Spring creek near 

 Springfield, and on the Sangamon, at Hewlett. It seems to be thinner 

 in all the shafts sunk through it in this county than in Sangamon, usu- 

 ally ranging from six to ten inches only. The sandstone intervening 

 between this and No. 7 is partially exposed on the lower courses of 

 Macoupin and Hodge's creeks, and also on some branches of Apple 

 creek in the north-western portion of the county. The limestone No. 11 

 of the Virden shaft section is a very hard gray limestone, and outcrops 

 at several points in the vicinity of Carlinville, and is therefore locally 

 called the Carlinville limestone. It ranges in thickness from six to 

 twelve feet or more, and is a compact, brownish-gray rock, weathering 

 to a rusty-brown color on exposure, the lower portion of the bed being 

 usually in regular layers, while the upper portion becomes locally concre- 

 tionary, or pebbly, in its structure. This limestone forms the bed-rock 

 over a considerable portion of the county, especially the region be- 



