GREENE COUNTY. 665 



tion is displayed with the greatest possible distinctness. Reed's Hill 

 may be specially named in this connection. It is a promontory of cliff 

 limestone overlooking the broad and fruitful valleys of Mad River, Bea 

 ver Creek, already described, and the Great Miami valley. From its 

 summit one of the most extensive and beautiful landscapes of south- 

 western Ohio is shown. As is indicated upon the map, the Clinton 

 formation is seldom found, except as a narrow margin to the Niagara 

 group, by which it is overlain. There are, however, a few outliers in the 

 south-western part of the county from which the Niagara rocks have 

 been entirely removed, and where the Clinton has thus been left to form 

 the surface for two or three square miles. 



The Clinton limestone at all these points, as elsewhere, is mainly a 

 semi-crystalline, crinoidal limestone. In its bedding it is uneven and 

 interrupted, occurring in lenticular masses. A course can seldom be fol- 

 lowed for twenty feet. Within this distance it is almost sure to termin- 

 ate in a feather edge. In composition the limestone is quite uniform, 

 consisting of about 85 per cent, of carbonate of lime and 12 per cent, of 

 carbonate of magnesia. Even the lowermost layers, which are distinctly 

 sandy in texture, and which are locally known as sandstone, do not devi- 

 ate from this general formula. A notable percentage of peroxide of iron 

 is of very frequent occurrence in the limestone, giving to it a deep red 

 color. This is the nearest approach to the famous Clinton ore which the 

 formation shows in Greene county. Just south of the county line, on 

 Todd's Fork, near Wilmington, a considerable deposit of this peculiar 

 and valuable limestone ore is found, and occasional outcrops of it are 

 found all the way to the Ohio River, the most important, thus far noted, 

 occurring near the north line of Adams county, in the vicinity of Sink- 

 ing Springs. It will be remembered that this same stratum rises into 

 immense economical importance as the Dye-stone ore of Eastern Tennes- 

 see and northern Alabama. The-more common colors of the formation 

 in Greene county are, however, light gray, yellow, and pinkish, the latter 

 tint being specially characteristic. Its crystalline character is so well 

 developed that much of the formation can be counted a true marble. It 

 is susceptible of a high polish, and when some of the red varieties of 

 the stratum are seleeted, it makes a highly ornamental stone, the se®- 

 tions of the whi^e crinoidal stems giving a beautiful relief to the darker 

 ground. It will, however, be seen from the facts already stated that the 

 limestone can have no great value for any such application or^ account 

 of its lenticular bedding. 



The base of the Clinton limestone, or rather the summit of the Cincin- 

 nati group, is a notable water-bearer, as is shown by the fine line of 



