PIKE COUNTY. 615 
its larger tributaries, a few feet of limestone rock are uncovered. The 
thickness of this formation as it is exposed here nowhere exceeds twenty- 
five feet. There is no ambiguity as to the place of this limestone in the 
geological series. Its stratigraphical position, its lithological character, 
and its fossils identify it unmistakably as the latest recognized but 
most extensive of the limestones of the State. It has been described in 
the Geology of Ohio as the Waterlume Group of the Lower Helderberg series. 
It brings the name above given with it from its outcrops in eastern New 
York, where it constitutes a very valuable deposit of cement rock; but 
the name is a misleading one in nine hundred and ninety-nine out of 
one thousand exposures in the West. While cement is found in it in a 
few places in Ohio, the great mass of it is a dolomitic or magnesian lime- 
stone, scarcely to be distinguished in chemical composition from the 
heavy beds of Niagara limestone that underlie it. In all of south-west- 
ern Ohio it can be perfectly distinguished by a local name, derived from 
its most extensive and valuable exposures, which occur at Greenfield, 
Highland county. It will be treated under this designation—the Green- 
field stone—in this report. 
The Greenfield stone is the highest Silurian formation in this portion 
of Ohio. It has peculiarities of bedding and color that serve to distin- 
guish it from all other limestones with which it is associated. It lies 
generally in very thin courses, of the kind commonly called “shelly.” 
Its light-brown color is not easily to be confounded with any variety of 
the Niagara, which is the limestone with which it is most closely asso- 
ciated. Its evenness of bedding is another of its distinguishing charac- 
ters. But few fossils occur in it, but these few are thoroughly character- 
istic, being strictly confined to this one formation. They consist of casts 
of a bivalve crustacean, Leperditia alta, and of several species of brachio- 
pod shells, among which the genera Nucleospira, Pentamerus, and Meristella 
have been identified. 
But an indifferent quality of building stone is furnished by this for- 
mation in Pike county. The deficiency in this respect, however, is less 
noticed from the fact that all parts of the county are bountifully supplied 
with the sandstones of the Sub-Carboniferous and Carboniferous forma- 
tions, among which the finest building stones of the State are included. 
The Greenfield stone of Pike county is burned into lime of the finest 
quality. It has the general composition and character of the Springfield 
lime, but even surpasses this standard product in whiteness and economy 
of working. There is no point in Ohio in which the best quality of lime 
can be manufactured as cheaply as in the Sunfish valley. The hills that 
bound the valley are covered with wood, from which a cheap supply of 
