88 GEOLOGY OF ILLINOIS. 



three feet, and the rock is even textured, and is easily cut and dressed, and is 

 used for caps and sills, as well as for foundation walls, and all the ordinary pur- 

 poses for which a building stone is required. It outcrops on McKee's creek, 

 north of Rushville, and also on the small branch running east from Pleasant 

 View into Sugar creek. 



The brown magnesian limestone of the St. Louis group, furnishes the best 

 material for culverts, bridge abutments and similar purposes, where the rock is 

 required to withstand the combined influence of frost and moisture. It out- 

 crops along the bluffs of Crooked creek, through its whole extent in this county, 

 and also in the bluffs of the Illinois river, as far north as Frederick. 



The Keokuk limestone, underlying the geodiferous shales of that group, 

 afford some good building stone, but its outcrop is limited to the bed of Crooked 

 creek, in the northwest part of the county. At the best exposures, which 

 were found in the vicinity of Birmingham, the rock was rather thin bedded 

 and cherty, but this was on the exposed outcrop of the bed, where the strata 

 had been split into thin layers by the combined influence of frost and moisture. 

 If quarries were opened in this rock, extending back beyond the influence of 

 atmospheric agencies, it would be found to improve in quality. For caps and 

 sills, where a handsome cut stone is desired, this bed will afford the best mate- 

 rial for that purpose, that can be found in this county. 



Limestone for Lime. The concretionary gray limestone, which forms the 

 upper division of the St. Louis group, furnishes the best limestone for the 

 manufacture of quick lime to be found in this portion of the State, and it may 

 be found in the bluffs of Crooked creek, through nearly its whole course, and 

 at intervals, along the bluffs of the Illinois river, as far north as Browning. 



At Birmingham, this limestone is eighteen feet in thickness, which is, how- 

 ever, considerable more than it will average, but it is usually from eight to ten 

 feet, and it will furnish an abundance of limestone to supply the demand for 

 lime in this county, for all time to come. A fair article of lime may also be 

 made from the Keokuk limestone, but where the other is accessible, it is always 

 to be preferred. 



The limestone over the upper coal seam, in the vicinity of Rushville, has 

 also been used for this purpose, but it does not appear to slack readily after 

 burning, and would, probably, make a dark colored lime. The abundant sup- 

 ply of both wood and coal in this county, will justify the manufacture of lime 

 on as large a scale as the wants of the adjacent region shall demand. 



Sand and Clay, for brick making, are abundant in all parts of the county, 

 and may be readily obtained at nearly every locality where the manufacture of 

 common brick is desirable. The brown clay, forming the sub-soil over a large 

 portion of the surface, answers a good purpose for brick making, and sand is 



