304 GEOLOGY OF ILLINOIS. 



hardens by exposure. The conglomerate, though of little value to the builder, 

 is interesting to the geologist on account of its containing a considerable amount 

 of the cherts of the Burlington limestone. These are almost entirely composed 

 of crinoid stems and heads, and a few other fossils. As is commonly the case 

 in these cherts, the fossils are not often well preserved, and of those obtained, 

 but few could be recognized, among which were Batocrinus oblatus, Actinocri- 

 nus, Platt/crinus , and Spirifer imbrex. 



In section 32, township 14, range 2, the coal seam No. 2 was formerly 

 worked, but the thicker seam above having been discovered, this one was 

 abandoned. In section 33, township 14, range 3, a mine was opened a few 

 years since, but the amount of pyrite contained in the coal was so great, that 

 it could not be profitably worked in competition with the better coals. Near 

 Aledo, in section 20, several banks have been opened, at one of which the fol- 

 owing section was obtained : 



FEET. IN. 



1. Clay shale. Not measured. 



2. Limestone 1 to 1 6 



3. Clay, passing into clay shale 3 to 4 



4. Coal No. 2 1 foot 6 in. to 2 



5. Clay. Not measured. 



No. 2 of this section, and the lower portion of the shale above it, contains a 

 number of fossils, among which are Spirifer lineatus, Athens subtilita, P/euro- 

 pJiorus soleniformis, Producftis, etc. In section 8, a little north of Aledo, a 

 mine was opened, though worked but little, in which the strata presented a pe- 

 culiar feature, as will be seen from the following section : 



FEET. IN. 



1. Shale. Not measured. 



2. Sandstone 8 to 9 



3. Clay shale 1 "3 



4. Coal 8 



5. Limestone f 6 



6. Coal . . , 1 6 



7. Clay, Not measured. 



This is the only instance in which I have noticed a stratum of limestone 

 separating the coal. 



In section 9, there are extensive quarries in the sandstone, No. 2 of the last 

 section. They have been worked for years, and have furnished immense 

 amounts of good building material. 



Near Millersburg, section 2, township 14, range 4, there is a mine that is 

 worked where the coal is from two to two and a half feet thick. 



Section 1 affords a sandstone which is much harder than that obtained from 

 most of the other quarries. There is but a single layer found here, and this is 

 only from a foot and a half to two feet thick. I was unable to learn its posi- 



