ADAMS COUNTY. 51 



seventy-five to one hundred and fifty feet, according to the thickness of the 

 Quaternary beds at the different points. At Camp Point, No. 2 was found at 

 the depth of ninety feet, and at Coatsburg, at 129 feet. Its general thickness 

 is from two to two and. a half feet, being about the same here as in McDonough 

 county. The quality of the coal is good, but the seam seldom has a good roof, 

 and, consequently, requires considerable expenditure for cribbing, where the 

 mines are to be worked permanently. South of Columbus, there is no devel- 

 opment of coal in this county, that would justify the expectation of its ever 

 becoming a valuable mining region, though considerable coal may be found in 

 the vicinity of Liberty and Kingston, extending south to the Pike county line, 

 perhaps sufficient for the local supply of that part of the county for some years 

 to come. Mill creek, on the western borders of this region, and McGee's 

 creek, on the east, show continuous exposures throughout their whole course 

 of the Lower Carboniferous limestones, that lie entirely below the Coal Meas- 

 ures, and clearly define a horizon, below which no workable coal seam has ever 

 been found. These limestones may be reached any where over the coal field 

 in this county, at a depth of from one to two hundred feet, and when reached, a 

 further search for coal, by going deeper, will only result in failure. In the 

 northern portion of the county, the Coal Measures rest upon the St. Louis 

 limestone, and hence the outcrop of this rock is a valuable guide, in determining 

 the boundary of the coal area ; but in the southwestern part of the county, 

 this limestone is not found, and the Coal Measures rest upon a lower division 

 of the Lower Carboniferous series, as they also do in Pike county. This has 

 resulted from the erosion of the limestone strata before the coal epoch, by 

 which the upper beds have been wholly, or partially removed, allowing the 

 Coal Measures to rest unconformably upon the lower divisions of the series. 

 But whenever any division of this limestone series is reached in searching for 

 coal, it is entirely useless to extend the search below that horizon. 



St. Louis Limestone. This division of the Lower Carboniferous series, as 

 has already been remarked, usually forms the substratum on which the Coal 

 Measures rest, and will be found outcropping immediately below the sandstone 

 which forms the base of the Coal Measures, in the northwestern, as well as the 

 southeastern portions of the county. The upper division of this formation is 

 usually a light gray concretionary, or brecciated limestone, from five to twenty 

 feet in thickness, below which, there is usually a regularly bedded brown, or 

 brownish gray magnesian limestone, from ten to twenty feet thick, which 

 locally becomes shaly, and passes into a calcareous or argillaceous shale. The 

 concretionary limestone sometimes contains irregular seams of green shale, or 

 marly clay, disseminated through it, and at some points, as at Butt's Mill, on 

 McGee's creek, is entirely replaced by green shales. At this point, there is 

 about thirty feet in thickness of this group exposed, consisting of regularly 



