TAZEWELL, Me LEAN, LOGAN AND MASON COUNTIES. 187 



about two miles from Chenoa, in a northeast direction, a ledge of bluish-gray, 

 irregularly bedded limestone outcrops in the side of a ravine. In general ap- 

 pearance this rock is very similar to that noticed in the preceding pages as 

 occurring on Salt creek, in Logan county, and like it, is probably in the upper 

 part of the Coal Measures. 



Economical Geology. 



Coal. From the preceding remarks it will be seen that, although at least 

 four or five different seams of coal underlie different portions of this district, 

 but two of them have been worked to any extent. The upper of these two, 

 No. 6 of the general section, is worked to a slight extent along the Illinois 

 river, in the neighborhood of Pekin and Peoria, and is also the upper seam in 

 the Bloomington shafts. Its thickness in these localities ranges from three to 

 four feet. The coal in this bed is generally softer, and often more impure 

 than that of the next seam below, and its workings have frequently been for- 

 saken for those of the lower bed. The sixteen-inch vein of coal, which has 

 been mentioned on a preceding page, as occurring on a ravine a short distance 

 back of Wesley City, and which I have there considered as a still higher vein 

 of coal, may possibly be this seam, in spite of its lesser thickness, as it is a 

 characteristic of this bed, in other parts of the State where it has been identified, 

 to vary considerably in its thickness, in some cases, indeed, thinning out very 

 rapidly within the distance of a few feet. The more reliable indications of 

 the accompanying limestone beds, with their characteristic fossils, cannot, 

 under all circumstances, be well observed, nor, indeed, do they appear to be 

 invariably present. 



The lower coal, No. 4, is the seam which is now mined in nearly all the 

 principal workings within the limits of this district, and will generally average 

 here at least four feet in thickness. The coal is generally a harder and better 

 heating material than that in the upper bed, besides being more reliable in its 

 thickness. It, however, contains, in some parts, its share of impurities, but 

 often so disposed in the vein as to be more easily separable. In some of the 

 shafts near the city of Pekin, the seam of coal, which I have referred in the 

 preceding pages to this horizon, contains in its lower portion, about sixteen 

 or eighteen inches above the base, a thin seam of fire clay, separating it into 

 two unequal portions, and sometimes a vein of slate, or slaty coal, is reported 

 to occur only five or six inches above the bottom. In the upper portion, also, 

 there is frequently some thickness of what is called "hickory," or mixed coal 

 and shale, or sand rock. The thickness of good coal, however, is sufficient to 

 render its working profitable. 



