292 GEOLOGY OF ILLINOIS. 



No. 1. No. 2. 



FEET. IN. FEET. IN. 



7. Sandstone 6 1 3 



8. Black slate 8 ? 



9. Coal and black slate 3 



Several of the strata were readily traced from one point to the other, and 

 this section will serve to illustrate how, in shafts only a short distance apart, 

 the strata may vary considerably. 



West of this point, in township 8, range 2, this seam crops out for some dis- 

 tance along Swan and Little Nigger creeks. At these localities mining has 

 been carried on for years, and in places the bluffs are almost honey-combed 

 by the entries, new and old. The mines along Little Nigger creek are mostly 

 in sections 7, 8, 9 and 10. In some of them the fire-clay below the coal is 

 varied in color, the usual tints being a light blue, though in some places it is 

 nearly white, while in others it is yellow or yellow and red. It is said that on 

 being burned the yellow turns to a blood red'. Along Swan creek, the mines 

 are in sections 15, 16 and 21. A little north of Roseville, in section 30, town- 

 ship 9, range 2, this seam has been worked to some extent. 



The coals of this county are mostly worked by drifts, or tunnels driven hori- 

 zontally into the hill-sides along the outcrop of the seams, and owing to the 

 shaly character of the roof of No. 2, considerable expense is incurred in " crib- 

 bing " to sustain the roof. The thickness of the coal is usually from twenty 

 inches to two feet, and in driving the entries it becomes necessary to remove 

 a portion of the roof shales, or the under-clay, in order to obtain the amount 

 of vertical space required to take out the coal. 



The lower seam, No. 1 of the Illinois section, varies from two to four feet in 

 thickness in this county. It is generally overlaid by black slate, or a dark col. 

 ored, and frequently, shaly limestone. This forms a very good roof, and makes 

 the working of this seam less expensive than that of the seam above, as, fre- 

 quently, but little or no cribbing is required. In section 14, township 12, 

 range 2, this coal crops out along the bluffs. In the eastern part of the section, 

 it is from three to three and a-half feet thick, and as it is here overlaid by clay, 

 the upper part of the coal is left for a roof. That part that is left is, however, 

 of but little value, it being impure. 



Flattened nodules of impure pyrite, called "nigger-heads" by the miners, 

 and frequently a foot or so in diameter, are not uncommon at some localities in 

 the upper part of this seam. Many of these contain numbers of fossils, which 

 are frequently well preserved. Some of the nodules from this mine afforded 

 Productus longispinus, var. muricatus, Athyris subtilita, Spirifer cameratus, 

 Chonetes mesoloba, Spiriferina Kentuckensis, Hemipronites crenistria, Pinna 



f Lima retifera, ScMzodus curtus, CardimorpTia Missouriensis, Edmondia 



ovata, Streblopteria tenuilineata, Pleurophorus radiata, Allorisma subcuneata, 



