96 GEOLOGY OF ILLINOIS. 



exposure of the strata associated with it, its exact position could not be accu- 

 rately determined. The seam is here only about 14 to 20 inches in thickness, 

 and was extensively worked at the time of our first visit to the county, in 1859, 

 for the distillation of coal oil. Ten retorts were then in operation at this lo- 

 cality, and the product was said to be thirty gallons of oil from a ton of coal. 

 However, the development of the oil wells of Pennsylvania, shortly afterwards, 

 put a stop to the manufacture of oil from cannel coals in this State, and the 

 mines were abandoned. This seam is underlaid here by about five feet of 

 excellent fire clay, which was worked at that time in connection with the coal, 

 and used in the manufacture of fire brick. About a quarter of a mile from 

 this exposure, on the other side of the hill, a two foot seam of bituminous coal 

 is seen, overlaid by two feet of dark blue bituminous limestone, exactly like 

 that above coal No. 1, at Seaville. The seam of cannel coal is probably the 

 lower division of No. 1, or a local development of another seam, occupying 

 nearly the same horizon. 



On Swan creek, one mile north of Avon, the following beds are exposed : 



FEET. IN. 



Sandy shales 16 



Coal 10 



Fire clay and shale 20 



Band of iron ore 10 



Bituminous shale 5 



Sandstone 10 



The band of iron ore in the above section resembles very closely that at 

 Chadsey's place, in Schuyler county, and at Seaville, in this county, above coal 

 No. 1, and probably occupies the same horizon. If so, it shows a very irregu- 

 lar development of the lower coal in this vicinity, and it is probable that this 

 seam is the least reliable of all the coals in this county, except No. 5, hereafter 

 to be mentioned. 



Coal No. 2 is one of the most regular seams in the whole series, and usually 

 ranges from two to three feet in thickness. It will be found everywhere in the 

 bluffs of Spoon river, where the strata are well exposed, and its stratigraphical 

 position is generally about forty or fifty feet above the horizon of No. 1, 

 although, in the vicinity of Seaville, the distance intervening between them 

 is about seventy feet. The roof is almost invariably a blue clay shale, and in 

 tunneling it requires to be thoroughly cribbed to prevent the falling of the 

 roof. In the south part of the county, this seam outcrops on Otter creek, 

 about a mile and a half west of Vermont, where it has been worked since the 

 earliest settlement of the county. It ranges in thickness from two and a-half 

 to three feet, in this vicinity, and outcrops along the bluffs of the creek for a 

 distance of three or four miles. A boring for oil was made in the valley of 

 this creek, commencing just below the horizon of No. 2, and extending to the 



