34 GEOLOGY OF ILLINOIS. 



Four miles west of Griggsville, on the northeast quarter of section 13, town 

 4 south, range 4 west, coal has been found on Mr. Dunham's place. The coal 

 is from fourteen to twenty inches thick, and is overlaid by about two feet of 

 fossiliferous black shale. Also, on the southeast quarter of section 11, in the 

 same township,' the same seam is exposed, and averages about eighteen inches 

 in thickness, and is overlaid by black shale, enclosing nodules of bisulphuret-of 

 iron with fossil shells. This coal outcrops at several localities, in the ravines 

 along the road between Griggsville and Salem, and also between Salem and New 

 Philadelphia. 



A half mile south of Griggsville, coal has been worked on Mr. Parker's land. 

 The seam varies in thickness, from eighteen to twenty-four inches, and is over- 

 laid by blue shale. Three-quarters of a mile east of this point, the shales and 

 geodes of the upper part of the Keokuk group outcrop along the same creek 

 on which the coal is found, and half a mile south of Houseworth's coal, the 

 Keokuk limestone was seen, and this seems to be the formation on which the 

 Coal Measures rest, in the central and northern portions of the county, except 

 at the outcrops east and southeast of Barry, where they appear to overlie the 

 Burlington limestone. 



On Mr. Lazarus Ross's place, a mile and a half northwest of Perry Springs, 

 some indications of coal may be seen in the bluffs of the middle fork of 

 McGee's creek. Partial outcroppings of black and dark blue shales appear 

 here, but so intermingled with drift clays, by the slipping of the beds ; that it 

 is difficult to say whether the shales were in situ, or had been moved by drift 

 agencies. Some attempts have been made here to find coal, but without 

 success. 



In the southeast part of the county we found an outcrop of the Conglom- 

 erate, which usually forms the base of the Coal Measures, overlying the Bur- 

 lington Limestone on Mr. Ch's Meisenbach's place, on the northwest quarter 

 of section 30, township 7 south, range 2 west. About ten feet in thickness of 

 the sandstone was exposed, where there had been an old quarry, and the whole 

 thickness of the bed at this point, is probably not less than fifteen or twenty 

 feet. This sandstone also outcrops on the adjoining farm, owned by Mr. 

 Jordan. This is probably an outlier of sandstone that was originally deposited 

 in a depression of the limestone, where it has been protected from erosion, 

 while the surrounding strata have been removed by denuding forces. 



From the outcrops of coal already mentioned in this county, it will be seen 

 that the coal is generally too thin to be profitably mined, except where it can 

 be done in open trenches by throwing off the overlying material. Coal cannot 

 be profitably mined in a regular way, either by tunnel or shaft, where the seam 

 averages less than two feet in thickness, and as the seams in this county are 

 usually less than that, they are of little value unless so situated as to be easily 



