108 The American Geologist. Feb. isoi 
To state that the Cincinnati anticlinal may have existed at the 
close of the Trenton period without the assistance of the Findlax 
and Bucyrus folds, but in a less marked degree, seems like beg- 
ging the question, since these folds practically constitute the Cin- 
cinnati anticlinal. Since these folds arc of later age than the 
Huron shales, and even perhaps were formed in later than Waverly 
times, what reason is there to suppose that the small amount of 
folding displayed in its Cincinnati anticlinal, which remains when 
the Findlay and Bucyrus folds are not considered, took place in 
times soon after the Trenton period ; that is, in times later than 
the age of Cincinnati group rocks, rather than in times later than 
the Huron shale or even later than the Waverly period ? 
As a result of the considerations here presented, the conclusion 
has been reached that the structure known as the Cincinnati anti- 
clinal is a fold of considerable length, formed in later than Hurcn 
shale, and probably later than Waverly times ; and, that for this 
reason, all formations from the Trenton to the Huron shale, are 
found to be involved in this fold. This conclusion is chiefly valid 
for Ohio, since almost all arguments are drawn from observations 
made in that state. The correlation of this anticlinal with the 
post-Carboniferous folds of Pennsylvania seems natural, and is 
suggested by the facts cited in regard to the Flint Ridge fossils 
above. 
The thickening of strata, going eastward from the anticlinal, has 
among other things suggested the origin of these strata from the 
Cincinnati anticlinal. Taken in connection with wider observa- 
tions they prove the contrary. As a general rule all palaeozoic 
for niations decrease in thickness in going from the Alleghany 
mountains westward to the Cincinnati anticlinal. The coarser 
strata, as a rule, also are found in the Alleghany licit, and are 
represented by finer sediments westward. This indicates a great 
region east of the Alleghanies. as the source for the sediments 
which diminish in thickness westward towards the Cincinnati an- 
ticlinal. 
In the same way. a thickening of formations takes place in cer- 
tain horizons in going northward from Cincinnati to the northern 
part of Ohio. 1 will refer here only to the presence of the Me- 
dina there, and the increased thickness of the Clinton, as shown 
by well-borings in the northern pan of the state: also, to the 
