FRANKLIN COUNTY. 633 
rated from it by as distinct a boundary as they are from the limestones 
which they: cover, but they agree with it in the style of bedding, in the 
general absence of fossils, and in chemical composition, except that they 
lack the bituminous matter that colors the Huron shale proper. There 
are, however, thin seams of true black shale that are scattered through 
these beds. The same horizon at other sections contains a much larger 
proportion of black slate, and this fact helps to justify their reference to 
the same system. 
In his report on Delaware county, Professor N. H. Winchell proposes 
for this blue belt the name of Olentangy shale, a convenient and unam- 
biguous designation, which will be adopted here. 
The Olentangy shale appears to be the stratigraphical equivalent of 
the beds termed Hamilton shale, by Dr. Newberry, which are found near 
Prout’s Station, Erie county, and which are there highly fossiliferous, 
and contain only Hamilton fossils. All of these fossils, however, are also 
found in the limestone below, the difference in the two sections being 
this: In the lower beds true Corniferous fossils are associated with the 
rest, while in the upper, no Corniferous forms have been found. The 
Olentangy shale of Delaware and Franklin counties is very poor in fos- 
- gils of any description ; nothing characteristic is known to occur in them, 
unless certain fish remains, reported by Rev. H. Herzer, from concretions 
in these shales at Delaware, prove to be so. 
The correlation of these Devonian limestones and shales of Ohio with 
the New York divisions of the same age, involves questions entirely 
similar to those that were met in the geology of our Lower Silurian de- 
posits in South. western Ohio. Hight hundred feet of Lower Silurian 
limestones and shales are found there, which undoubtedly represent the 
Trenton limestone, in part, the Utica shale, and the Hudson River group 
of the New York scale; but no one can draw the line where one epoch 
ends and another begins. The growth of these beds was continuous. 
The interruptions that marked the epochs on the continental border did 
not make themselves felt in the central sea, but the life of the lower 
beds held on through the vast cycles of time required for such a growth. 
It was re-enforced from time to time with the forms belonging to higher 
horizons, and the result is, that there is here an extricable blending of 
the forms of life that characterize distinct formations at the east. In 
regard to the designation of these beds, all ambiguity is removed by 
giving them a name derived from the locality that shows them best. We 
refer them all to the Cincinnati group, making such divisions of them as 
the facts here warrant, and as convenience requires. 
In like manner, the Devonian limestones, already described, grew ina 
