922 GEOLOGY OF OHIO. 
Middle Kittanning seam of one or both of the Freeport coals (Nos. 6a 
and 7). There are numerous localities in which both of the latter seams 
appear in the same vertical section with the great seam; also, the character 
of the Freeport coals is quite different from that of the top coal of the 
Hocking Valley seam. 
The lower bench of the normal seam ranges from 6 to 30 inches in 
thickness. In the western part of the field it is thinnest ; it attains its 
greatest thickness in the Sunday Creek Valley. The lower slate or 
parting, which makes the upper boundary, is seldom more than 1 inch 
in thickness, and 4-inch is the common measure. 
The middle bench of the normal seam ranges from 4 to 28 inches 
in thickness. It is thinnest in the Sunday Creek Valley, and thickest 
in the Straitsville and Monday Creek regions. The second slate, which 
covers the second bench of coal, is very steady and regular. In fact, 
it is very nigh coextensive with the Middle Kittanning seam. In thick- 
ness it ranges between 2 and 4 inches. 
The third or upper bench of the normal seam, which is from 12 to 
24 inches in thickness, is generally poor in quality, at least for part of 
its volume. It holds this character almost everywhere, through Mus- 
kingum and northern Perry, where the seam is single, being known as 
“bone coal,” and very seldom being taken down as fuel. Directly 
above the second slate there is always throughout the Hocking Valley 
field a band of inferior coal. It is known as bone coal, hard bone, soft 
bone and soft coal, and the miner is almost everywhere instructed to 
reject it. Occasionally it becomes marketable, both in and out of the 
Hocking Valley. Very often, after rejecting 4 to 8 inches of soft coal 
at the bottom of this bench, a good piece of coal is found above. This 
bench is of the best character in the Straitsville and Monday Creek 
districts. 
The supplementary seam of the Hocking Valley is, in the general 
view, counted with the upper bench of the normal seam, the whole being 
known as top coal. It has a maximum thickness of 10 feet. All the 
thickness of the Hocking Valley seam in excess of 6 feet, and in many 
parts of the field all in excess of 43 feet, is to be credited to the sup- 
plementary seam. Its value is small in proportion to its volume. In 
the Sunday Creek Valley, where it reaches its maximum, it has been 
found impossible to market more than 33 feet of the 10 that belong to 
it. Its coal could scarcely sustain itself in market if separated from 
