FRANKLIN COUNTY. _ 615 
quite marked by the occurrence of high-colored clays, red and white, 
that hold the interval between the two formations. 
One peculiar phase of the lower Corniferous imestone, in this region, 
deserves to be noted here. About twelve or fifs :n feet above the base of 
the formation, deposits of a very fine-grained 4d sharp, silicious sand 
occur locally. None of these deposits have ba . noticed in Franklin 
county ; but just beyond the line, in Jefferson tov, ship, Madison county, 
on the bank of Little Darby Creek, this Corniferous sandstone is found, 
‘and there is every reason to believe that other pockets of it will be 
found in the vicinity. Facts of the same sort are given in the report on 
Champaign county; and in northern Ohio, like deposits are known. 
The sandstone exactly agrees in character with the Hillsboro sandstone, 
of the Niagara group. That occurs, also, in local deposits, interrupting 
the continuity of a great limestone formation. 
This Corniferous sandstone has long been known to the plasterers ot 
the neighborhood. Whenever the finest quality of work was required, 
recourse was had to the thin layers of sandstone found in the section 
here referred to. More particular description of the deposit will be found 
in the report on Madison county. Its composition is ninety-two per 
cent. of silica, and seven per cent. of lime. 
The Delaware beds appear in this section, also, in the very thin layers — 
that cover the limestone at many points in the quarry. All that was 
said in regard to this stratum, under the previous section, applies to it 
as shown here. 
Hnough has now been said upon the stratigraphical relations of the 
Corniferous limestone, to give the reader a fair idea of the formation. 
Incidental reference has been made, in several instances} to its chemical 
composition, and, also, to its paleontology. These topics will now be 
treated a little more at length. 
2. Chemical Composition—Under the head of chemical composition, 
such analyses as are available, will be given. They will be arranged in 
ascending order, beginning with the lowest beds of the formation. 
Analysis No. 1, is of the heavy course that lies just above low water 
at Dublin. As has been shown, it belongs very near the lower boundary 
of the formation. It shows itself to be a magnesian limestone, and this 
is true, to the same extent, of but few courses in the Corniferous lime- 
stone of Ohio. It will be remembered that the Waterlime and Niagara 
groups, which underlie the Corniferous for at least 200 feet of vertical 
descent, are both magnesian limestones—for the most part, containing 
more than forty per cent. of carbonate of magnesia. 
All the beds of the Corniferous limestone, have more or less magnesia 
