178 GEOLOGY OF OHIO. 
Where it occurs, the whole seam is “shot out of the solid,” and thus the 
upper coal, which is weak at best, is much broken. 
The price of mining is graduated to the thickness of the coal in the 
room, sometimes by an accepted scale, and sometimes by special agree- 
ment that reaches substantially the same result. Counting 65 cents as 
the price of mining 4’ coal, an addition of 5 cents per ton is made for 
every 3 inches below 4’, the maximum of $1.00 being rarely reached. 
The special adaptation of the Block coal to iron manufacture was 
an important factor in the earlier development of the field. For a long 
time it has been the fashion to deplore the rapidly hastening exhaustion 
of the supply, and to deprecate the use of this excellent fuel for more 
common purposes, but events are proving that the coal went at the right 
time, and in a way most serviceable to all the interests concerned. 
What is left of it is suffering severely from competition with the various 
newer fields of Ohio and Pennsylvania, and with all the advantages 
that its high quality affords, it is barely able to maintain itself in market. 
The element of royalty alone counts heavily against it, the excess in 
this particular above the coals that it meets being often 50 cents per 
ton, and sometimes more. 
As to the southward extension of this valuable seam, little is to be 
said. Not a single clear occurrence of it has been reported in Eastern 
Ohio south of the points named, except that a recent drilling shows 4% feet 
of coal at a depth of 307 feet near the boundary of Austintown and Can- 
field townships. 
The coals struck at Leetonia and New Lisbon, in the valley of 
Bull Creek, and in the Ohio Valley, near Smith’s Ferry, belong, with- 
out exception, to the Mercer horizon, and have been referred to the 
Sharon level only through the dislocation of the series that has already 
been pointed out. When the Lower Kittanning coal was counted the 
Lower Mercer, the true Lower Mercer would not be far out of place 
for the Sharon seam; or, to use the numeral designations, when No. 5 
was counted No. 3, then the true No. 3 would answer fairly well for 
No. 1. 
Aside from the very valuable deposits already described, Mahoning 
county has no large supplies of coal for the general market, but its 
whole surface is occupied by the Lower Coal Measures, and there are 
