MINING COAL.
As there are `numerous modes practised among miners in " getting coal," or mining it, as it is technically termed in the anthracite regions, we will describe several of the modes in general use.
In the red-ash seams of the anthracite regions, a stratum or band of soft clay, slate, or imperfect coal is often found, which is known among our miners as "under-mining." This is dug out from under the coal or from between the benches, as the case may be, with small, sharp, and long-handled picks. If the band is of sufficient size, the "holing" is carried in from three to four feet, entirely across the breast ; or if the coal immediately over the "mining" is of a nature to be removed without much labor and waste, the same thing is accomplished. But if the stratum of mining is thin and the accompanying coal hard and solid, the holing is not made so deep. In either case the coal is said to be " under-mined" when in this condition, and is then thrown down by powder or iron wedges. Sometimes, when "slippy" or weak, it will fall without further exertion on the part of the miner; and in such cases he is careful to leave small "posts" of mining until the last. These are then pried out with a long pike, or dexterously knocked out with the pick.
This process is known as " in some parts of England ; but there in the bituminous seams the kirving or under-mining is generally made in the coal at the bottom of the seam, which, however, could not be done in anthracite seams, on account of its hardness. Therefore, where " mining" does not exist in a seam, the coal is got by blasting it out with powder ; and in small seams the intelligent and experienced miner shows much skill in keeping his breast in working trim, in order to give advantage to the force of the blast by getting his powder in the back of the coal.
Most of our large white-ash seams are mined entirely by the " blasting" process. In the Mammoth bed, which is generally from 20 to 30 feet in thickness, the lower bench is blasted out, much the same as the whole coal is worked in the small, solid seams where under-mining does not exist ; or, in other words, the large seam is under-mined by blasting out the bottom bench by a number of small holes. When this is done, the great mass of the top is either ready to fall, or may be easily thrown down •by a few well-directed "shots,"—that is, holes drilled into the coal to a greater depth than ordi dary, and in the proper places,—and by the use of larger bodies of powder.
Sometimes masses of a hundred tons are thrown down at once in those large seams. The modes of excavating coal in breasts or chambers is much the same in all the anthracite regions. The breasts are generally carried directly up the dip of the seam, and are from 16 to 30 yards wide, with a pillar on either side, and a shute in the middle or on each side, parallel with the pillars. But when the seam is not steep enough for the coal to gravitate or slide down the incline of the shutes, cars are taken into the breasts or chambers, the road occupying the same position as the chutes, except that the roads run obliquely across the dip instead of directly with it. When chutes are used, the miner throws his coal into them, and it is loaded into the cars at the bottom of the shute, which starts from the main gangway ; but when the cars are taken into the breasts, the miner throws the coal direct into them, and they go to the surface without further rehandling. There are modifications of these modes ; but those speci fied are generally in use.
Most of the seams in the anthracite regions of Pennsylvania are pitching seams, and dip at varying angles to the centre of their basins. Those which dip at 40° and above can he mined with ease by breast and chute or runs, and no other mode can be more available ; while those which dip at 10° or less can be mined by breast and ears without much difficulty by the modes generally in use. But the intervening dips are difficult to mine by the ordinary processes, and are generally the most expensive, under equal circum stances, since they are not steep enough for the shute method without planking or the use of sheet iron on which the coal may slide from the miner to the car, and are too steep for the convenient use of the car, which cannot be successfully used on steep grades. In this lies one of the defects of the present system, which cannot be remedied on the principles of mining adopted ; and many of our miners are convinced that the English plans cannot be modified to our peculiar dips. But this is a mistake, as we have clearly shown in a preceding chapter.