FRANKLIN COUNTY. 603 
All cf the samples were taken from the Roberts farm, on the banks 
of Little Darby and just above the county line. 
The only economical use to which the very limited exposures of the 
Helderberg series in the county can be turned is to the production 
of a good quality of lime. The preceding table shows that we find 
in them the typical magnesian limestone which is so much esteemed as 
a source of lime in all the districts to the south and west in the State. 
Several cf these analyses are almost identical in character with those of 
the limestones of Greenfield and Leesburg, in Highland county, which 
belong to the same formation, and they do not differ essentially from 
those phases of the Niagara formation that are turned to most account 
for the same purpose, viz., the Springfield, Cedarvilleand Yellow Springs 
limestcne. It will presently be seen that the county possesses an un- 
limited supply of lime of a very different character, viz., the hot and 
quick setting lime derived from true carbcnate uf lime, from which the 
existing demand is principally met, but it is clearly an advantage to 
have the magnesian carbonates at hand as well as the true carbonates of 
lime. Good natural facilities can be found for prcducing large quan- 
tities of lime, both above and below Georgesville. 
The courses of the Helderberg limestone are too thin and uneven to 
be valued for building purposes, especially in the presence of the heavy 
bed of the Corniferous formation that overlies them. 
III, CORNIFEROUS LIMESTONE. 
1. Stratigraphical relations—The Corniferous limestone holds a very 
different place in the geology of the county fiom the foregoing. It covers 
a much wider area, is a much thicker formation, has very numerous ex- 
posures, yields building stone and lime of great value. and is worked 
very extensively for both purposes. When to this it is added that it is 
one of the most remarkable store-houses of ancient life in our whole 
series of rock formations, it will be seen that it possesses every element 
of geological interest. . 
As has been already implied, the whole thickness of the formation ap- 
pears in Franklin county, but there is no one section that contains every 
element. The nearest approach toa complete section is found in the east 
bank of the Scioto, from Dublin northwa:ds to the county line. A few 
feet are here wanting both at the top and at the bottom of the series. 
The Waterlime, or Lower Helderberg, is found in the bed of the river, a 
little to the northward, and it is probably safe to say that a descent of 
ten feet at several points within the district named, would carry us to 
the lower boundary of the Corniferous; while its upper limit, viz., the 
