94 GEOLOGY OF OHIO. 
It will be observed that the two series of sections are quite unequal 
in measurement. Section C of Fig. XIX is located at a well-marked 
boundary in the coal field. From this point westward there is a notice- 
able diminution in intervals. The leading elements, with the excep- 
tion of the Lower Kittanning coal, all retain their relative positions, 
but this last-named seam becomes uncertain. The most decided reduc- 
tion of interval takes place between the Middle Kittanning coal and . 
the Putnam Hill limestone to the westward. 
In section D, a fine local development of the Lower Freeport coal 
occurs. The seam ranges from 2% to 9 feet in thickness. It is called 
No. 6 in the report on Tuscarawas county, in volume III, but the sec- 
tion as given here shows clearly that it is entirely distinct from the 
Middle Kittanning coal, which appears at its normal interval below. 
The present line of sections has carried us through one of the most 
important mineral districts of Ohio, viz., the Tuscarawas Blackband 
field. The same order of facts can be observed with reference to this 
horizon here as at other points. The blackband les on the outer margin 
of the Upper Freeport horizon, while the mineable coal of the same horizon 
is found in the interior. The Upper Freeport coal is nowhere through- 
out this district of value as a source of fuel upon its western outcrops, 
or where it lies high in the hills. It is only where it approaches its 
interior boundaries that it gives rise to important mining centers, as at 
Salineville, at Dell Roy, and in the Connotton Valley, and at Cam- 
bridge. 
The last section of the list, which was taken near Coshocton, fairly 
represents the Tuscarawas Valley for the remainder of its course. The 
valley runs in the direction of the strike or level bearing of the strata, 
and the same elements that appear at Coshocton can be found in almost 
every ravine between that point and Dresden. 
The southward trend of the whole coal field aids in continuing the 
section down the Muskingum Valley as far as Zanesville. The Lower 
Mercer limestone and coal make the floor of the Muskingum at the foot 
of Putnam Hill, while the gray limestone gets its geographical name 
from this very locality. The Kittanning coals are found here in excel- 
lent development, and have long been extensively worked. ‘The Upper 
Freeport coal, clay and limestone, and also the Lower Freeport coal are 
all found at their proper level on every side, and the Cambridge and 
