302 GEOLOGY OF ILLINOIS. 



penetrate all the coals to be found here, and determine positively the 

 amount of coal accessible at any given point where the experiment may 

 be made. 



Coal seam No. 5 affords a coal of good average quality, tolerably hard, 

 bright, compact, and usually free from pyrite ; it has a rather uneven 

 fracture, but inclines to break into cubic forms, the layers rather thick 

 and separated by partings of carbonaceous clod or mineral charcoal, 

 and contains vertical seams of white carbonate of lime. An analysis 

 of this coal from the Hodge's Creek mines, made by the late Mr. HENRY 

 PRATTEN, former chemist of the geological survey, and published in 

 Dr. NORWOOD'S "Abstract of a Eeport on Illinois Coals," gave the 

 following result: 



Specific gravity 1-2797 



Loss in coking 43 48 



Total weight of coke - 11 ' 1 : >'~ 



100 00 



ANALYSIS. 



Moisture 6 50 



Volatile matters - 36 98 



Carbon in coke 48 . 72 



Ashes (white) ~ 



100 00 

 Carbon in coal 53.8 



This coal is about equal in quality to the Belleville seam in St. Clair 

 county; it is a good steam-producing coal, hard enough to bear transpor- 

 tation, and when carefully selected this seam will afford a good smith's 

 coal. In quality it will compare favorably with the average of our 

 western bituminous coals. 



Building /Stone. The Coal Measure strata seldom afford a good build- 

 ing stone, except for foundation walls, culverts and the more ordinary 

 uses to which a coarse and homely material may be used. The Carlin- 

 ville limestone is the most valuable rock of its kind to be found in this 

 county, and it has been freely used through the central and eastern por- 

 tions of the county for the ordinary uses above named. In the vicinity 

 of Carlinville, the bed ranges from five to six feet in thickness, and 

 occurs in quite regular layers from four inches to a foot or more in thick- 

 ness. The rock is compact, fine grained and of a bluish-gray color on 

 a freshly fractured surface, but weathers to a rusty -brown color on ex- 

 posure. When burned, it slacks freely, and makes a tolerable good but 

 dark colored quick lime. It appears to stand exposure well and has 

 proved to be a durable stone where used for foundation walls, bridge 

 abutments, etc., and is the most valuable limestone in the county for 

 economical purposes. 



The coarse brownish-gray limestone above the Carlinville bed, which 

 is found in the bluffs of the Macoupin, east of Carlinville, is also a 



