218 GEOLOGY OF OHIO. 
comes directly down upon the latter, adding itself to the normal thick- 
ness of the seam. It is said to hold this relation in all the northerly 
mines of the town. ‘The quality of this rider is not good, and its coal 
is rejected. Whenever it comes within 2 or 3 feet of the main coal, it 
makes a bad roof, the shale below it replacing the normal cover, and 
proving treacherous. There are but few cases in which the Upper 
Freeport sandstone attacks the coal, but occasionally the protecting 
shales are entirely removed. 
The coal rests on about 4 to 10 feet of fire-clay, in which the 
bowlders of the Lower Freeport limestone are bedded, the uppermost 
of them being within one foot of the coal. The limestone is hard and 
stubborn, some of it being charged with iron, and much of it being 
silicious. Some blocks are found of a fair degree of purity as limestone, 
The floor of some of the mines is subject to “creeps,” and in the 
worked-out rooms it often rises to meet the roof without any break in 
the latter. 
The coal is bright and cubical, but it is of rather a tender nature. 
Its joints are even and regular, but they are numerous, and divide the 
coal into small blocks, to which fact its weakness is mainly due. 
Although a tender coal, it cannot be profitably mined without the use 
of powder. The result is that it mines small. In the Steubenville 
mines, under the system of mining now in force, by which the miner is 
paid for his coal before it is screened, never less than one-third, and 
generally one-half of the coal that is sent from the shaft comes out as 
slack and nut coal. 
The coal is of the cementing variety, and it makes a coke of fair - 
strength and character. All of the small coal and slack has been 
utilized in this way, hitherto. The amount of visible “sulphur” or 
pyrite varies in different parts of the seam, and also in different por- 
tions of the mines. ‘The bottom bench is more impure than the breast 
coal, bui the larger balls of pyrite lie near the roof. Like the Freeport 
seams generally, this coal ranges rather high in sulphur, as will be seen 
in the appended analyses. ° 
In the following table the analysis of the coal from a representa- 
tive mine is given: 
