270 GEOLOGY OF ILLINOIS. 



stones of the Lower Carboniferous series, the Devonian and Upper Silu- 

 rian systems being both unrepresented at this point. 



The following section will show the relative position and comparative 

 thickness of the stratified rocks in this county : 



No. 1. Coal Measures 40 to 50 feet . 



No. 2. Chester group 100 to 350 



No. 3. Upper St. Louis limestone 140 to 150 



No. 4. Lower St. Louis or Warsaw beds 120 to 130 



No. 5. Keokuk limestone 150 



No. 6. Burlington limestone 75 to 100 



No. 7. Kinderhook group 80 to 100 



No. 8. Trenton limestone (in part) 120 



The aggregate thickness of these rocks may be estimated at about one 

 thousand feet, and they represent a very large portion of the whole 

 paleozoic series below the Coal Measures, as that series is developed in 

 Southern Illinois. 



Coal Measures. 



An outlier from the main coal field, in St. Clair county, impinges 

 on the county line immediately north of Columbia, and at some, points- 

 probably extends a little over the line into this county, following- 

 very nearly the trend of the county line. The mines worked at this 

 locality are known as Henckler's mines, being owned and worked by 

 Mr. H. F. Henckler, of Columbia, and are located on sections 13 and 

 14, township 1 south, range 10 west, and are mostly in St. Clair 

 county. The coal obtained here is a good block coal, and if on further 

 examination it proves to be sufficiently uniform in its development to 

 admit of successful mining, it will prove, from its proximity to the iron 

 furnaces at south St. Louis, a valuable acquisition to the mineral re- 

 sources of this portion of the State. The coal rests directly upon the 

 St. Louis limestone, with only a few inches of dark colored clay shale 

 between, and the coal seems to follow the inequalities of the limestone 

 surface on which it rests, and at one point in the mine it was seen to 

 rise abruptly to the liight of about six feet with the elevation of the 

 limestone floor on which it rested, and as suddenly sink again to its 

 former level. The main point to be determined is, whether these in- 

 equalities may not be so frequent, and sometimes so great, as to cut off 

 the coal entirely, and thereby greatly increase the cost of mining. The 

 seam is about three feet thick, when fully developed, and ranges usually 

 from two to three feet in thickness. It is quite free from pyrite, and 

 presents all the essential characters of a true block coal. It is overlaid 

 by a few feet of argillaceous limestone, passing locally into calcareous 

 shales, above which we found a stratum of soft porous limestone about 

 two feet thick, that appeared as though it had been subjected to a pro- 

 cess of leaching, by which a large portion of the calcareous matter had 



