STRATIGRAPHICAL ORDER. 119 
found above the coal a hard or non-plastic clay, as at Portland, Jack- 
son county, which is of excellent quality. 
The Lower Kittanning coal is separated from the limestone by an 
interval varying between 9 and 30 feet. In the northern portion of the 
field, the smaller measure prevails. In Lawrence county, the usual 
measure is 25 to 30 feet, a heavy sandstone sometimes setting in. The 
coal is workable at many points, but it attains the greatest value in the 
southern part of Lawrence county, about New Castle. It is best known 
as the New Castle coal, on this account. 
The second coal above the limestone or the Middle Kittanning coal 
has the same relative prominence and value in this field that it has in 
so many other districts through which we have passed in our review. 
We have just left it in the Hocking Valley as the Nelsonville coal, the 
thickest and most profitable seam in the State. We found it thinning 
down into the Carbondale coal, which was still further reduced in the 
Mineral City seam. It is in this thinner and weaker phase that it ex- 
tends over the northern half of the Hanging Rock field. There are 
considerable tracts in Vinton and Northern Jackson counties where it 
does not admit of being mined with profit, though its place is always 
marked, but from Jackson county southward it gains somewhat in 
volume, and gives rise to many country mines. At Washington Fur- 
nace, it is extensively worked for iron manufacture, being used raw in 
the furnace with great success. The coal seam is less than 3 feet in 
thickness here. It is 4 feet 2 inches thick, and of excellent quality at 
Evans’s Mills in Greenfield township, Gallia county. On the Ohio River 
at Sheridan, it has been worked on the large scale, and it attains still 
greater value south of the Ohio River in the Coalton District of 
Kentucky. ‘ 
A heavy sandstone underlies it at some little distance, the Kittan- 
ning sandstone of our general scale, and a heavy sandstone overlies it 
everywhere, the Lower Freeport sandstone. 
The Lower Freeport coal has a good deal of value throughout the 
field. It is the Hamden Furnace coal of my report in volume III, and 
also the Hatcher coal of the same report. It is frequently a thicker, 
and therefore more valuable seam than the Middle Kittanning below it. 
The interval between these seams ranges from 30 to 55 feet. In the 
northern portion it holds the former measure, but in volume III it was 
shown that this interval slowly expanded until it became about 50 feet 
for the general measurement. 
