THE LOWER COAL MEASURES. 217 
is left 3 ft. 4 in. and 3 ft. 6 in. in some entries, and at the Mingo Shaft, 
which adjoins the Boreland property, the coal fell to 23 feet in thick- 
ness, or to even smaller measure than this, and the mine was therefore 
abandoned, but to the southward the seam increases again, being found 
5 feet thick in the Brilliant Shaft, 3 miles below, and the same in Rush 
Run Shaft, which is 11 miles below Steubenville. 
The structure of the seam is quite constant. There is a slate part- 
ing from 6 to 14 inches above the bottom. This is the only regular 
division in the seam. The lower bench of the coal is more variable 
than the upper. The ordinary contractions and expansions of the seam 
are mainly confined to it, the upper bench or “breast coal” running 
very steady and uniform. The structure is represented in the following 
figure : 
FLGURE XXXI 
STEUBENVILLE SHAFT CQAL, 
Blue Shuts Lath SAS AUER ho cS 
1. Ee 
Five-clas GS REST ee eae DW GC 
lnwwvesborie -....-____.- ——— 
LSe - © OY -------—----- . 
The roof of the coal consists normally of a hard blue slate or soap- 
stone. It is sometimes replaced by sandrock, in: which case the coal 
always suffers in quality, and generally in thickness. The regular roof 
is sound and excellent in all respects. It constitutes one of the main 
features, in fact, in the working of the coal. 
A thin coal seam has been spoken of above the Shaft coal. In the 
lower mines of Steubenville this seam is 22 fect above the Shaft seam, 
and about 6 inches thick. .It gradually falls toward the coal below it, 
until on the northern boundary of the Market Street Shaft mine, it 
