102 GEOLOGY OF ILLINOIS. 



Coal No. 7 is the highest coal strata seen in this county, and being usually 

 only from sixteen to twenty inches in thickness, no attempt has been made to 

 mine it in competition with the thicker seams that underlie it, and outcrop 

 over a much wider area in this county. Judging only from the appearance of 

 the coal, where it was exposed in natural outcrops, we were disposed to regard 

 it as a coal of a very superior quality, good enough, apparently, to be used in 

 the iron furnace without coking, and hence, if it should be found as much as 

 two feet in thickness, at some favorable locality, it might be mined as success- 

 fully as some of the heavier seams are at the present time. It outcrops on the 

 head of Big creek, about a mile north of Piper's mine, along most of the hill- 

 sides east of Norris, to Copperas creek, and also underlies all the highlands 

 about Farmington. At Powel's mine, two miles east of Norris, the following 

 measured section was made, showing the relative position of the two upper 

 coals, and the character of the strata associated with them, and they constitute 

 the highest beds of the Coal Measures seen in this county : 



FEET. IN. 



Compact, hard gray limestone 4 to 6 



Shale, partially hidden 15 



Coal No. 7 1 4 



Shale, and shaly sandstone 35 



Brown argillaceous limestone 2 6 



Bituminous shale 1 " 2 



Coal No. 6 4 6 



The limestone at the top of this section appears to form the bed rock over the 

 highest ground in the region of Farmington, where it is immediately overlaid by 

 the Drift deposits, and is probably the highest rock exposed south and west of the 

 Kickapoo. Just over the line, in Peoria county, the bed is twenty feet or more 

 in thickness, which was probably its original thickness in the vicinity of Farm- 

 ington, but it has been reduced to its present thickness, perhaps by erosion 

 anterior to, or during the Drift period. 



Conglomerate. At the base of the Coal Measures, in this county, there is 

 from ten to twenty-five feet of coarse grained sandstone, which probably repre- 

 sents the conglomerate usually underlying the lower coals. This sandstone was 

 only seen at two or three points in the bluffs of Spoon river, between Seaville 

 and Bernadotte. Just below Seaville Station, it measures about twenty-five 

 feet in thickness, extending from the under clay of No. 1, which rests imme- 

 diately upon it, down to the low water level of the river, where it rests upon 

 the St. Louis limestone. The sandstone is here a massive, coarse grained rock, 

 quite ferruginous, and forms a mural cliff, from its tendency to harden on ex- 

 posure. At Bernadotte, it is thin bedded, and partly shaly, and crumbles 

 readily on exposure to the atmosphere. It is quite irregular in its developmen* 

 and general aspect, and cannot always be identified unless found in connection 



