338 GEOLOGY OF OHIO 
and “pea,” the latter, which is the finest or smallest variety, is not 
made at all mines. The space between the bars of the sereen is 1 to 
14 inches; occasionally wider or narrower bars are used, but they are 
exceptional cases. All coal which does not fall through the bars of the 
screen is called “lump.” A second screen, with bars } an inch apart, 
separates the “slack” from the “nut.” Pea coal is made by screening 
the nut coal. The slack is raised from the ground by a self-loading 
elevator, and thrown into a revolving circular screen, which thoroughly 
sifts out the fine coal which falls back to the ground, and is hauled 
away as refuse matter. At some mines the nut coal is washed and 
purified before being loaded for shipment. 
The proportion of lump to nut and slack varies considerably in 
mines, partly owing to the nature of the coal, and partly to the skill 
with which the coal is mined. ‘Tender seams naturally make more nut 
and slack than hard coal. In the Coalton or Wellston district, where 
the seam is unusually tender, two-fifths of the whole pass through a 14-inch 
screen, while in the Mahoning Valley, in the Brier Hill district, 
where the coal is hard and firm, only one-sixth of it falls through the 
screen. In mines in which powder is injudiciously used the coal is 
wantonly broken up into nut and slack. Unskilled miners make more 
fine coal than experienced workmen. 
Work commences in the mines at 7 o’clock A.M., an hour is given 
to dinner at noon, and work ceases at 5 P.M.—nine working hours 
being a day’s work. The diggers work by the ton, and are in a measure 
their own bosses. All the workmen are expected to be down the shaft 
or slope before the mules commence hauling. In mines in which heavy 
charges of powder are used in blasting out the coal, the workmen are 
forbidden from firing until 4 P.M.; in 5 minutes after the signal is 
given 40 or 50 discharges are heard, and such is the force of these blasts 
that the earth shakes above. Vast volumes of smoke load the air of 
mines after these subterranean discharges. 
In some mines firing is allowed twice a-day, at noon and quitting 
times, and in the Steubenville district, where small discharges of powder 
suffice, and the ventilating currents are unusually strong, the workmen 
blast at all hours of the day, and suffer no inconvenience in conse- 
quence. 
All shaft mines are provided with cages or elevators, upon which 
the loaded and empty cars are raised and lowered through the shaft. 
