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 Clenton 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 Hastern 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 selected, it makes a highly ornamental stone, the see- 
tions of the white 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 on 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. 
