886 GEOLOGY OF OHIO. 
preéminence here that it may be taken as the proper representative of 
the whole field. This seam is known asthe Limestone Ore. It gets its 
name from the fact that it is, for the most part, immediately underlain 
by a stratum of fossiliferous limestone, which is commonly called the 
Gray Limestone through the country that it occupies. The stratum wags 
named by Prof. Andrews the Ferriferous Limestone, but, for reasons to be 
hereafter given, it is termed in thisreport the Hanging Rock Limestone. 
Assuming this ore seam, then, to be the characteristic and determin: 
ning feature of the Hanging Rock district, and counting in, as belonging 
to it, all the furnaces that are established on it, it will be found neces- 
sary to extend the limits already named, by a few miles, so as to embrace 
the new furnaces of the Hocking Valley that depend on the Baird Ore 
for their chief supply, the Baird ore being the name by which the lime- 
stone ore is known in its northern developments. The south line of 
Perry county thus becomes the northern boundary of the Hanging Rock 
district. The western margin of the Coal Measures constitutes its limit 
in that direction, while, upon the east, an equally irregular boundary is 
formed in the sinuous line that marks the descent of the limestone ore 
below drainage. Its southern limit is the Ohio River, for, though all the 
elements of our geological scale can be followed unchanged into Kentucky, 
we have no immediate interest in them there. 
The present report will be confined to the discussion of one general 
topic, viz., the strattgraphical order of the rocks that occupy this belt. Nor will 
the whole series be considered here. Only that portion of it that begins 
with the Zoar Limestone and ends with the Cambridge Limestone, will 
be particularly treated, but two additional limestones, viz., the Maxville 
and the Ames, will be employed in the classification. Incidentally, 
the order of other parts of the series will be briefly discussed, and also’ 
the economical values of many of the more important deposits, but the 
limits of available space make this restriction necessary. 
1. This district embraces the Lower Coal Measures and part of the 
Barren Measures of the generally received classification, in ali amounting 
to about seven hundred feet, the Ames Limestone of Prof. Andrews being 
taken a3 the upper limit. 
No two sections along this extended belt of country will prove exactly 
identical. Strata change from mile to mile, and even from farm to farm, 
somteimes in composition and sometimesin quality. Some are quite local 
in character, disappearing abruptly ; others are more persistent, and can 
be traced over wide areas. A few hold their relative positions throughout 
the field, but even these are subject to very important modifications. 
The lime or ore of any one section may be replaced by flint in another. 
