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216 GEOLOGY OF OHIO. 
Another element of conspicuous value in this field is the Pittsburgh 
coal, which is found in the hills opposite, and also below Steubenville, 
whenever a proper elevation is reached. The seam has a thickness of 
not less than 5 feet, strengthening to 6 feet in much of its territory. 
There are several other thin beds of coal in the Steubenville region, 
as for example,the seam that lies near the Crinoidal limestone, and also 
a seam that hes 20 to 30 feet above the Shaft coal in some places, but 
the Shaft coal and the Pittsburgh seam constitutes at present the sole 
resources of the district, so far as coal is concerned. 
The Shaft coal will be first described. It becomes a shaft seam, 
as will be remembered, south of Will’s Creek. At this last-named 
point it lies at the level of the river, but it soon rises above railroad 
grade as it is followed northward, and is well up in the hills at Toronto, 
and above in the Ohio Valley. | 
It dips slowly to the southward through Steubenville, and the 
varying depths of the shafts depend mainly upon the elevation of the 
points at which they are sunk. The range of depth is from 75 to 
261 feet. 
The seam has been followed as far south as Rush Run, 11 miles 
below Steubenville, where it is mined. To the westward it runs every- 
where under heavy cover, and it is not known to rise to day in any 
thoroughly characteristic showing. It has not been mined on the south 
side of the river until recently, but its presence has been proved there 
in various ways by borings, and also in one instance by being followed 
partly across the river in one of the Steubenville mines. A. shaft has 
recently been sunk to it in Wellsburgh, West Virginia, the coal being 
found in full thickness. Its area is thus seen to be indeterminate, and 
the main fact that can be given in this connection is that it extends as 
a shaft seam for about 14 miles along the river front. The mines have 
been carried westward in unbroken coal for«more than a mile ina 
number of instances. It is thus evident that a large area is to be found 
here. The best available calculations show, that from 1,000 to 1,200 
acres have been already worked out. 
The thickness of the seam throughout the district ranges from 3 to 
5 feet. The ordinary and perhaps the average thickness is 4 feet. The 
coal has never been persistently worked where it falls below 3 feet. 
There are large areas where it holds a thickness of more than 4 feet, 
but it is properly described as a 4-feet seam. At the Boreland Shaft it 
