DELAWARE COUNTY. 287 
of the Olentangy, in the banks of a ravine the distance of a mile from 
the river. For a considerable distance from this point, in descending 
the Olentangy, the banks show frequent exposures of the limestone. 
Near Mr. Wm. Case’s quarry, five and a half miles below Stratford, the 
black slate may be seen by ascending a little ravine that comes in from 
the east. The section here is given in describing the Upper Corniferous. 
Just at the county line the slate appears in full force again in the left 
bank of the river, little streams bringing fragments from the west side 
as well as from the east. A perpendicular exposure on land owned by 
Granby Buell of about forty feet consists of about five feet of shale at the 
bottom. It is also seen on the west of the Olentangy, by ascending a 
ravine near the county line, on Archibald Wood’s land, and again, by 
ascending another ravine about three-quarters of a mile north of the 
county line, on the land of F. Bartholomew, and it seems to extend about 
two miles west of the Olentangy at its point of exit from Delaware 
county. 
Olentangy Shale.—This name is given to that bluish and sometimes 
greenish shale which is so extensively exposed in the banks of the 
Olentangy River, in Delaware county, and which underlies the black, 
tough, but thin beds of the Huron shale. It has a thickness of about 
thirty feet. No fossils have been found in it. It is interstratified with 
a little black slate, and in some of its exposures it bears a striking 
resemblance, at least in its bedding, to the Huron shale. The section 
which has already been given of its exposure at Delaware is the most 
complete that has been taken, and very accurately represents its bedding 
and characters wherever seen in the county. It lies immediately upon 
a hard, blackish, sometimes bluish, crystalline, pyritiferous limestone, 
or on the beds that have been denominated Upper Corniferous in reports 
on the counties of Sandusky, Seneca, and Marion. In the county of 
Franklin, and further south, it is said to be wanting, and the black slate 
lies immediately upon the 'same limestone beds. It is also wanting in 
Defiance county, the black slate there also lying immediately on the 
beds that contain the only Hamilton fossils there yet discovered. This 
shale embraces occasionally a course of impure limestone that has a blue 
color and a rude concretionary appearance. On account of easy quarry- 
ing, it is a constant temptation to the people to employ it in foundations. 
It is found, however, to crumble with exposure after a few months or 
years, and change into a soft shale or clay. Large blocks of it are washed 
out from this shale just below Waldo, in Marion county, by the force of 
the water coming over the dam at the mill, and have been somewhat 
used by Mr. John Brundage, near Norton, in Marlborough township. 
