294 GEOLOGY OF ILLINOIS. 



limestone and coal No. 8. Usually the intervening beds are about 

 thirty to thirty-five feet in thickness, but here we have nearly sixty 

 feet in thickness below the limestone without any indication of coal, and 

 this probably results from a local thickening of the sandstone, a repeti- 

 tion of what may be seen in the section of the Virden shaft, where the 

 sandstone, No. 15 of that section, is sixty-three feet in thickness, and 

 the whole distance from the limestone to coal No. 8 is seventy-six feet 

 and two inches. In the bed of Macoupin creek, about half a mile below 

 Holliday's ford, on section 30, township 9, range 8, we found an outcrop 

 of bituminous shale and thin coal which may probably be considered as 

 representing coal No. 8. The beds exposed here show the following 

 succession : 



No. 1. Clay shale... 10 to 12 feet. 



No. 2. Chocolate-colored limestone 1 " 



No. 3. Bituminous shale .. '' 4 in 



No. 4. Coal n g in 



No. 5. Fire-clay _2 n 



We obtained a few fossils from the limestone No. 2 of the above sec- 

 tion, and among them Naticopsisventrica, a small Hacrocheihix, and Lop- 

 liopliyllum proliferum, all of which are found in the roof of No. 8 coal, in 

 the vicinity of Springfield. If we add to the top of this section the 

 shales and micaceous sandstones of the preceding section, we shall 

 have about the same thickness of strata intervening between coal No. 

 8 and the Carlinville limestone that occurs in the .Virden shaft. More- 

 over the local thickening of beds of sandstone is by no means uncom- 

 mon in the Coal Measures, but on the contrary is of frequent occur- 

 rence. 



There are some excellent exposures of this micaceous sandstone along 

 the creek bluffs just below the railroad bridge. The rock is partly mas 

 sive, especially the lower portion of the bed, and affords layers two feet 

 or more in thickness, some of which are quite hard and will afford a du- 

 rable building stone. Silver ore was reported to have been discovered 

 in this sandstone, in a quarry on the south-west quarter of section L'O, 

 town 10, range 8 west, a few years since, and an attempt was made to 

 organize a joint stock company for its development. The silvery scales 

 of mica which the rock contained were mistaken by some ignorant per- 

 sons for silver, and hence the reported discovery of a rich mine of me- 

 tallic ore at this locality. The only material of economic value this rock 

 contains is building stone of a fair quality, which may be obtained here 

 in abundance. 



The best exposures of the beds overlaying the Carlinville limestone, 

 that we met with in this county, are on the upper course of Macoupin 

 creek, commencing eight miles north-east of Carlinville in the vicinity 



