762 GEOLOGY OF OHIO. 
The Pittsburgh seam comes within easy reach of the river at La Grange, 
and thence southward is worked in a great number of localities, bat 
generally only for local use. It is regarded as inferior to the Shaft coal. 
being more cementing in character and containing more sulphur. It 
varies, however, considerably in quality, and in the valleys of Short 
Creek and other tributaries of the Ohio shows extended lines of outcrop, 
which, when the railroads traverse these valleys, will supply an unlim- 
ited quantity of excellent coal at very low rates. 
TILTONVILLE. 
At Tiltonville, two and a half miles south of Portland, the Pittsburgh 
coal is first mined commercially on the river. It is here five and a half 
feet thick, with a “rider” or roof of coal some two feet in thickness, sep- 
arated from the lower bench by from six inches to one foot of clay shale. 
The roof coal is not mined. The quality of the Tiltonville coal is ex- 
cellent. It has been coked at the Martinsville Blast Furnace, and the 
coke produced from it was very compact and silvery. No coke has, how- 
ever, yet been manufactured from the Tiltonville coal except by way of 
experiment. The Pittsburgh seam at Tiltonville lies 185 feet above the 
railroad, and a well has been sunk to reach the Steubenville coal. This 
is said to have been found at the depth of 400 feet, and to have been only 
- one foot in thickness. 
The general geological structure of the western portion of the county 
has already been briefly sketched, but there are some facts of local in- 
terest in this section that remain to be noticed. In the highlands of the 
county the Pittsburgh coal is the only element in the geology that has any 
considerable economic value. This, as has been mentioned, is found in 
the hills about Knoxville, its extreme northern outcrop. It also occurs 
in detached areas in the southern part of Ross and the western sections 
of Island Creek townships. It is more generally present in Salem town- 
ship, and is worked at Springfield, Richmond, etc. The coal is here very 
near the surface, having for cover only a little shale and earth. Half a 
mile east of Richmond, on the road to Steubenville, the outcrop of the 
Pittsburgh seam is visible, covered by the full thickness of its limestone. 
over this is shale, and forty-five feet above is seen the outcrop of a thin 
coal corresponding to that over the Pittsburgh seam, at Wintersville. In 
the vicinity of Salem the valleys are cut deeper, and the hills are com- 
posed of the Barren Measures. These contain two, and sometimes three 
seams of coal, which are always thin, but the lower one is locally and 
sparingly worked. This lies under the Crinoidal limestone, and is the 
