4 ECONOMICAL GEOLOGY. 



Coal No. 2, however, is very uniform in its development, though 

 it seldom attains a thickness of more than three or three and a 

 half feet. The superior quality of the coal which it affords has led 

 to its heing mined wherever it can be reached at a moderate depth. 

 Along the western and northern borders of the coal field it has gen- 

 erally a very uniform thickness of about two feet, but in the vicinity 

 of Murphysboro, in Jackson county, it is a double seam, the upper 

 division being three feet and the lower two feet in thickness. In 

 the vicinity of LaSalle it is the lowest coal found, and there has 

 an average thickness of about 2^ to 3J feet. 



Coal No. 3 is a very uncertain seam, and is more frequently 

 represented by a bed of bituminous shale than by a true coal. It 

 has been mined at Atkinson, in Henry county, where it ranges in 

 thickness from three to three and a half feet of good coal. It also 

 outcrops in Fulton county, three miles northwest of Fairview, show- 

 ing about eighteen inches of good coal. The lower seam in the 

 Bloomington shaft I am also inclined to refer to this coal, and it 

 is there three feet eight inches in thickness. In Gallatin and Saline 

 counties there is a three-foot coal which occupies about the same 

 position in those counties that No. 3 occupies in the valley of the 

 Illinois river, but as the thicker seams lying above it are easily ac- 

 cessible, but little attention has been given to the lower seams. 



No. 4 is also an uncertain seam and has only been identified at 

 two or three points in the State. In Gallatin county it was found 

 two and a half feet in thickness, and it has been identified at one 

 or two points in Fulton county. Away from the borders of the coal 

 field, nothing is at present known as to the development of these 

 lower seams, all experiments being usually ended when the first 

 workable coal is reached. A boring at Biverton, seven miles east of 

 Springfield, is the only one near the center of the State that has 

 been carried entirely through the Coal Measures. 



The following is the report of that boring, furnished by Mr. C. B. 

 Swan, the contractor, commencing below coal No. 5 and extending 

 to the base of the Coal Measures: 



Ft. 



Bottom of coal 237 



Fire clay 4 



Limestone 4 



Black shale 25 



Clay shale 35 



Coal No. 4(?) ".",.".]..'. '. 4 



Fireclay 2 



Clay shale (soapstone) 20 



Limestone ..... T 25 



