COAL MINING. 337 
required to maintain the-roof in place, but all rooms need propping. 
Sometimes 4 or 5 rows of props, planted 3 to 4 feet apart, are required 
to make the roof safe. The props are sunk in the floor a few inches, 
and are surmounted with a flat-cap, about 2 inches thick, and 10 inches 
wide, and 18 inches to 2 feet in length. Some mines require only one 
or two rows of props. The roof is not uniform throughout the mine ; 
in one part it may be hard and strong, in other parts, tender and 
treacherous. 
The railroad track of mines is about 3 feet in width; along the 
main entries the rails are made of T-iron, 12 to 16 pounds to the yard ; 
in the rooms scantling is generally used, the size of the rail being 
governed by the weight of the loaded mine cars. Providing a good 
T-iron track all over a mine, entry and room alike, is true economy on 
the part of mine owners, although the first cost may be greater. 
A good track and abundant ventilation are found wherever good 
mining engineering practice prevails. Mules cannot haul coal over bad 
roads ; miners cannot work in bad air. Nature will rebel; the mule may 
be lashed by the driver, but he will retaliate with his heels; the miner 
may be cursed by the boss, but he will retaliate with a strike. 
Mines in which the coal is 6 feet high use horses for hauling ; below 
this height, mules are used. 
Beds lower than 4 feet require to have the roof ripped, to admit 
the hauling with mules. In low veins, a frequent practice is to employ 
pushers to push the mine cars from the working faces to the hauling 
roads or entries. ‘This is the practice in the Steubenville district of 
Jefferson county, and the Coalton district of Jackson county. It costs 
less to employ men as pushers than to rip the roof to admit mules. 
Along the main galleries the roof is ripped from end to end, and 
mules do the hauling to the emain shaft or mouth of the drift, as the 
case may be. | | 
In the thicker beds of coal the mine cars hold 1 to 14 tons; in the 
thinner veins, $ to 1 ton. Thick beds cost less than thin one for haul- 
ing coal, and other dead work. The cost of the dead work of mines 
ranges from 15 to 40 cents per ton; this includes entry-driving, cutting 
air-ways, cutting ditches, blasting roof and bottom, laying track, pro- 
viding props and rail timber, and hauling, dumping, and loading coal. 
Three grades of marketable coal are made at mines, “lump,” “nut,” 
22 Ge 
