CALHOUN COUNTY. 15 



ton limestone, on section 35, township 12 south, range 2 west, and the St. 

 Louis limestone, which appears a short distance below, but no exposure of it 

 was found in this part of the county. 



St. Louis Group. The Keokuk limestones, at the outcrop below the Cap 

 au Ores bluff, are succeeded by beds of brown magnesian limestone, some sixty 

 or seventy feet in thickness, which form the lower division of this group. 

 They dip at a moderate angle in the same direction as the lower beds, and 

 are overlaid by compact gray limestones which are nearly horizontal in their 

 position, and form a perpendicular bluff from forty to fifty feet high. From 

 this point to Johnson's Landing, these gray limestones, which, in the aggre- 

 gate, are probably a hundred feet or more in thickness, form a continuous line 

 of bluffs from fifty to seventy-five feet in hight, and a short distance back 

 from the river are overlaid by the Coal Measures. The gray limestones which 

 form the upper portion of this group are even bedded, and partly concretion- 

 ary, or brecciated in their structure. At Johnson's Landing, now better 

 known as Bell's Landing, the upper portion of this limestone forms the bluff 

 for thirty or forty feet above the river level, consisting of compact gray and 

 brown limestones, separated by partings of clay shale, in which the fossil corals 

 of this group, Lithostrotwn canadense, L. prolifera, and an undetermined Syr- 

 ingopora, are quite abundant. 



Below this landing, the bluffs of the river trend to the eastward, and some 

 of the lower beds come again to the surface, and continue gradually rising to 

 the old town site of Milan, where the limestone bluffs end on the western side 

 of the Illinois river valley. On the eastern side of the county, below the Cap 

 au Ores axis, there are but few exposures of this limestone, although it un- 

 doubtedly continues along the bluffs on this side of the valley, for three or four 

 miles above their southern extremity. North of this axis, the St. Louis lime- 

 stone has not been found in this county, but south of that point, it forms almost 

 the entire limestone exposure. 



Coal Measures. This formation, like the St. Louis limestone, is restricted 

 in its developments to the southern part of the county, and is found under- 

 lying a considerable portion of the high lands below the Cap au Gres axis. 

 Commencing about two miles below this axis, it underlies the highest portion 

 of the county, in township 13, in ranges 1 and 2 west, though exposures of the 

 strata are rarely met with, and consequently its boundaries cannot be very defi- 

 nitely determined. The only coal mine that has been worked to any extent in 

 this county, is Williams's mine, located on a fraction of section 1, township 14, 

 range 2 west, about one mile above Frjiitland, and two miles above Bell's, for- 

 merly Johnson's Landing. These mines were opened nearly twenty years ago, 

 and have been worked, at intervals, down to the present time. The following 

 section, made at these mines, will show the character and succession of the 



