606 GEOLOGY OF OHIO. 
The bone bed is the boundary between two very distinct divisions of 
this series of limestone—viz, the Delhi and Delaware beds of Professor 
Winchell. The latter division is locally known as the “blue limestone,” 
to distinguish 1t from the underlying courses. It differs from these 
courses in color, in style of bedding, in chemical constitution and in fossil - 
contents. Tne color of the stone is uniformly blue. In bedding it is 
very even and regular. It contains a notable proportion of silica and 
alumina in its composition, which militates against its durability asa 
building stone. It would otherwise answer an admirable purpose for this 
use, the thickness of the layers, which average six inches, the regularity 
and the color all recommending it above any other limestone of the vi- 
cinity. Some beds are found that can resist the weather, and these come 
to be valued highly. 
The fossils of the Delaware beds are at this point chiefly fish remains. 
Teeth, plates, jaws, and other bones are not infrequently met with through- 
out twenty-five feet of this series. The uppermost seven or eight feet 
consist of very thin and shaly beds, which contain flint in large quantity. 
They are, as a rule, without fossils of any sort. The Delaware beds of 
this immediate section are thirty-two feet in thickness. Their upper 
boundary is as distinct as their lower, consisting of the blue shales that 
make the base of the great system of Devonian shales that succeed this, 
the last of the Paleozoic limestones of Ohio. 
All but one, the lowermost, of the elements of the Corniferous limestone 
of the county are shown in this interesting section. Before treating of 
other sections in detail, it will be well to establish the divisions of the 
formation which it is proposed to recognize here. Two well marked divi- 
sions have already come to view in the section just described, viz., the blue 
limestone, thirty-two feet in thickness, which is, from its occurrence at 
Delaware, and the extensive use made of it at that point, well named the 
Delaware limestone ; and secondly, the white and buff limestones which 
occupy forty-five feet of the scale below the Delaware beds. Though the 
several portions of this last named section differ from each other consid- 
erably in color, bedding and composition, the differences found are not 
marked and constant enough to demand recognition, and the whole of 
this section will be designated the Columbus limestone. This name was 
first given toit by Dr. Newberry, in Vol. I, Geological Survey of Ohio, | 
page 143. Itisin all respects a suitable name, marking a central and | 
well known locality where the formation is most largely displayed and 
worked. The Columbus limestone will be held to include all of the beds 
intervening between the waterlime group of Upper Silurian age, and 
the bone bed to which reference has already been made. The Delaware 
