BUBEAU COUNTY. 175 



here to a bold hight, the outliers of a rocky formation first begin to ap- 

 pear. On the farm of a Mr. Dustin, not far from where Nigger creek 

 comes down through the bluff's, stone is quarried to some extent for 

 building purposes in Trenton and on adjoining farms. The stone is a 

 hard, sub-cry staline rock, similar to that outcroppiug on Rocky Run. 

 In some places it resembles a quartzose sandstone. 



In the Bureau county bluffs, from Nigger creek to the county line be- 

 low Peru, good quarries could be opened in many places j but the diffi- 

 culty of access to them, the sparse settlements in this portion of the 

 county, and the great abundance of stone about Peru and La Salle, 

 have conspired to prevent the opening and working of the outcrops. 

 In some instances the distinction between argillaceous and quartzose 

 sandstone and argillaceous limestone, is hard to determine, and I may 

 be mistaken in the true character of these outcrops at Rocky Run, and 

 about the mouth of Nigger creek. To me they look like a sub-crystaline, 

 clayey sandstone, if such a rock can be supposed to exist. 



These are the most important and almost the only outcrops in the 

 county, except the rock strata found in close proximity to the coal 

 seams. 



The coal mines at Sheffield, in the township of Mineral, are the old- 

 est and best known mines in the county. There seems to exist here one 

 of those local coal deposits of limited extent, so common all over the 

 northern part of the State. It is irregularly shaped, but would be 

 found about four miles in diameter. Sections 22, 23, 24, 25, 26, 27, 28, 

 34, 35 and 36, in the township of Mineral, and several sections adjacent 

 thereto, in the township of Concord, are estimated to contain more or 

 less coal beneath the surface.* The Sheffield Mining and Transporta- 

 tion Company are operating several mines about a mile west of the vil- 

 lage, and near the railroad track. A low range of hills, facing north 

 and east, rises from Coal creek to the high prairie lying south. Into 

 this low hill several drifts are extended to the south and west. Some 

 of the drifts are inclined planes extending down to the coal. The drifts 

 are driven into the hill about one-half mile. Twenty-five or thirty feet 

 overhead productive prairie farms are tilled. Black shale, soapstone and 

 irregularly bedded, yellow crystaliue sandstone (!) compose the roof; not 

 all found associated together, but some in one place and some in an- 



* Ni )JK. These apparently local deposits of coal, occurring along the borders of the Illinois coal 

 field, are not detached outliers, but are localities where the coal seams attain their full thickness, and 

 may be successfully worked ; while in adjacent territory they become too thin to work, although they 

 may attain their full thickness again within a distance of a few miles. An area of coal land is often 

 pronounced unproductive, on the evidence obtained, perhaps, by a single boring, where the drill 

 may have struck a "horseback." or .some other irregularity in the coal seam, while another boring, 

 bvit a few feet from the first, would have shown the usual thickness of coal. It is by no means safe 

 to pronounce any consideracle area within the confines of the coal field unproductive, on the strength 

 of such evidences as may be obtained by one or two experiments with the drill. A. H. W. 



