64 
BULLETIN OF THE LABORATORIES 
GEOLOGY. 
In southwestern Ohio, immediately, above the Cincinnati Group, 
lie a series of strata, formerly known, both scientifically and popularly, 
as the Cliff Limestone. They are so designated, for instance, in the 
second annual report of the Ohio Geological Survey, undertaken in 
183S, by W. W. Mather. Many of the cliffs and cascades in this 
part of the State owe their origin to the peculiar characteristics of this 
formation. Later, however, a division into two groups was made, 
and after a more extended study by Prof. Edward Orton the upper 
section was identified with the Niagara Group, but the lower was called 
the Clinton. In the reports for 1869 and 1870, these distinctions 
were carefully made. At various times, however, ’authors have seen 
fit to express doubt of the correctness of the name employed for these 
strata, and Prof. James Hall, especially, has had occasion to do so in 
the 12th annual report of the Indiana Survey. For our purpose it 
will be well enough to retain the name, Clinton Group, at least for the 
present, but it is expected that after a presentation of all the facts, 
others, perhaps, will be ready to adopt some other term. 
The Clinton is not a group of any great depth. For its western 
exposures in Ohio, ten to fifteen feet would be a fair estimate. In its 
eastern exposures in Highland and Adams counties ‘‘its average thick- 
ness is somewhat increased, but probably never exceeds 40 feet, and 
this thickness is sometimes attained in the northern district as a maxi- 
mum, as for instance, at Yellow Springs, in Greene county.” (Italics my 
own). A section of the geological series of Highland County gives 
a thickness of 50 feet to the Clinton Limestone. (Geo. Surv. Ohio, 
1870, page 298 and section at page 310.) 
The Clinton Limestone rarely affords any extended surface expo- 
sures, but is found like a narrow line separating the Cincinnati and 
Niagara Groups of the State, and usually is seen in close connection 
with both. A section of rock belonging to the Clinton age, there- 
fore, generally also includes both the upper and lower strata. 
The rocks of the Cincinnati Group, in Ohio, are quite level, show- 
ing no marked local variations in their dip. At their junction with 
the Clinton Group, however, they frequently become unfossiliferous, 
and the rock is replaced by less solid shales and bluish clays. d‘he 
surface of the group also becomes very undulating in character, fre- 
(piently attaining a dip of four feet in forty. As a consequence the 
superposed rocks of the Clinton Group are 4l§Q yer^ undulating. 
