72 GEOLOGY OF ILLINOIS. 



tion of a tough, plastic clay, well adapted to the potter's use. The same effect 

 may be produced on the freshly dug shales, by throwing the material into heaps, 

 and allowing it to remain fully exposed, for a year or two, to the action of the 

 atmosphere. About a dozen potteries have been established in the vicinity of 

 Ripley, and this number may be increased indefinitely as the wants of the com- 

 munity shall require, as the supply of the raw material is abundant. 



Fire Clay. The under-clay of coal No. 2 is often pure enough for the 

 manufacture of fire brick, though no attempt has been made, so far as I could 

 learn, to test its quality in this county. 



Building Stone. This county is not so well supplied with good building 

 stone as the counties lying south and west of it, where the older rocks outcrop 

 more extensively. 'The quartzose sandstone, which forms the base of the Coal 

 Measures, may sometimes be safely used for this purpose, and the massive beds 

 of this rock, which outcrop at the base of the bluff, for three or four miles 

 below LaGrange, seem to be sufficiently coherent in their structure to make a 

 durable building stone. The brown magnesian limestone, and the calcareous 

 sandstone, of the St. Louis group, may usually be safely used for this purpose, 

 and the former is especially adapted to the construction of culverts and bridge 

 abutments, where a material is required that will withstand the combined 

 influence of frost and moisture. The sandstone below the upper coal seam, 

 near Mount Sterling, appears to be a very good freestone, and the jail at that 

 place has been built of this rock. 



Limestone for Lime. The best material for the manufacture of common 

 lime, is the concretionary limestone, which forms the upper division of the St. 

 Louis group. It is usually a very pure carbonate of lime, and is more exten- 

 sively used for this purpose, than any other limestone in this portion of the 

 State. Along the river bluffs, below LaGrange, this rock has been used at sev- 

 eral points for this purpose, though at some localities it contains too much sili- 

 cious or argillaceous material to make a pure lime. In the vicinity of Mt. 

 Sterling, lime has been made from the nodular gray limestone, which lies be- 

 tween the two upper coals, and it is said to make a strong lime, suitable for 

 mortar and cement, but darker colored than that made from the concretionary 

 limestone of the St. Louis group. 



Sand and Clay for Brick. These materials are so common and abundant 

 in this portion of the State, that it seems scarcely necessary to mention their 

 occurrence at any particular locality, but as it is a primary object in all reports 

 of this kind, to make known abroad the natural resources of the State, it seems 

 hardly proper to entirely omit the mention of materials so nearly universal as 

 these in their distribution. There is, perhaps, no mineral product of the State, 

 if we except coal, more important to our vast prairie region, than the materials 

 for the manufacture of common bricks, and there are but few branches of 



