20 The American Geologist. July - i: " ,:; 
lower portion of the Corniferous group as denned in the same 
work and reach in all a thickness of forty-five. feet. 
Above this well marked horizon is found a series of thin 
and shalv beds known as blue limestones and for the most part 
of little economic value. They are about thirty-two feet thick, 
fossiliferous in the lower part with the fish remains of the 
Bone-bed, but barren and flinty above. "Their upper bound- 
ary is as distinct as their lower, consisting of the blue shales 
that make the base of the great system of Devonian shales. 
These constitute the Delaware limestone of professor \Yin- 
chell, or the Upper section of the Corniferous limestone of the 
Geology of Ohio."* 
Corniferous Geography. — Two lines of outcrop of the Cor- 
niferous exist in the state caused by the elevation of the Cin- 
cinnati anticline. Beginning with the longer of these, which 
crosses the state from lake Erie to Pickaway county, we find 
its northern extremity in the two islands, KeJly and [Middle, 
the former of which is a part of Erie county, Ohio, while the 
latter belongs to Ontario, Canada. On Kelly's island, the Low- 
er Corniferous has long been quarried to supply a flux for the 
furnaces of northern Ohio, for which this stone has proved 
exceedingly well adapted. 
The peninsula in Sandusky county, is the most northerly 
exposure of the Corniferous limestone on the mainland along 
this line. The easternmost point of Ottawa county defends, 
with the northernmost part of Erie county, the entrance to 
Sandusky bay. The upper blue-stone transition beds are large- 
ly quarried at Sandusky, but the lower, or true Corniferous 
lies too deep to be reached. Crossing Erie county and touch- 
ing the northwestern corner of Huron county and the south- 
eastern corner of Sandusky county, the outcrop enters Seneca 
county, where it is but slightly exposed in spite of the large 
area which it underlies. In eastern Crawford county and 
western Wyandot county the same is true. The surface is 
covered with drift, the exposures are few and little quarrying 
is done except along Broken Sword creek. In Marion county, 
however, about twelve feet of the blue transition beds are 
quarried near the countv seat, while in Delaware county, along 
the Olentangy, one of the best sections in the state is displayed 
* Ibid., p. 606. 
