Coal and the coal mines

by Homer Greene

There is also a loading place for the rock and slate which have been separated from the coal on its way through the breaker; and there are two or three points where the coal dirt is gathered from its pockets to be taken away. All this refuse is run out by separate tracks to a convenient distance from the breaker and there dumped.

It is estimated that sixteen per cent. of the material which goes into the breaker to be prepared comes out as waste, and is sent to the refuse dump. It can readily be supposed, therefore, that in the course of a few years these waste heaps will grow to an enormous size; and as a matter of fact they do. The dirt or culm, which includes all material finer than buckwheat coal, is usually dumped on a separate pile from the rock, slate, and bony coal, since it is not wholly without at least prospective value. It has been used frequently in the coal regions to fill in beneath railroad tracks supported by trestle-work, and it is valuable as a foundation on which to lay stone flagging for footwalks, since it does not yield readily to the action of frost. Culm has also been utilized by adding to it a certain percentage of mucilaginous or pitchy material and compressing it into bricks for fuel. In some European countries a large amount of waste is burned in this way, but in America the cost of preparation is still too great to permit of competition with prepared anthracite. The most characteristic feature of scenery in the anthracite coal regions, aside from the breakers themselves, is the presence of these great, bare, black hills of culm, shining in the sunlight, smoothly white under the snows of winter. Sometimes these culm banks take fire, either spontaneously or as the result of carelessness or accident. If the pile is near enough to the breaker to menace it, or near enough to an outcrop to carry combustion into the coal of the mine, the fire must be extinguished, and this is sometimes done with much labor and at great expense. If no danger is apprehended, the fire is allowed to smoulder until it burns out, a process which may take months or even years, during which time little blue flames flicker on the surface of the bank, the sky above it is tinged with red at night, and the whole black hillside is finally covered with great blotches of white ash. To the poor people who live in the vicinity of the breakers these heaps of refuse coal are an unmixed blessing. Pieces of good coal are always being thrown out inadvertently with the waste, and the bony coal that is discarded is not by any means without value as a fuel; indeed it makes a very respectable fire. So, too, one can obtain, with a screen, from the culm heap quite a little percentage of material that will burn. Thus it comes about that every day women and children and old men go to these black hills with hammer and screen and gather fuel for their fires, and carry it home in bags, or wheelbarrows, or little handcarts. It is the old story over again of the gleaners in the field.

CHAPTER XIV.
IN THE BITUMINOUS COAL MINES.

A brief history of the discovery and introduction into use of the bituminous coals of Pennsylvania has already been given; but only casual reference has been made to the methods of mining in the bituminous regions. It is true that of the one hundred and twenty thousand square miles of workable coal beds in the United States less than five hundred square miles are of anthracite coal. It is true, also, that more than two thirds of the coal produced in the United States during the year 1887 was of the bituminous variety, and that the income from bituminous coal during that year was nearly twice as much as the income from anthracite. Yet it is obvious that in any description of coal mining methods the anthracite mines should be used as the chief examples. This is not only because of the greater commercial importance of anthracite, and of its greater familiarity as a domestic fuel, but it is principally because of the far greater skill, judgment, and ingenuity required in mining it and preparing it for market. In the bituminous regions the coal is soft, lies flat and near the surface, and is mined by the simplest methods. The reader is already familiar with some of the complications, obstacles, and problems that meet and beset the operator in the anthracite regions, and with the great labor, vast expenditures, and high degree of skill necessary to reach, take out, and prepare the anthracite coal. In view of these facts no excuse is necessary for attaching the greater importance to the description of methods in the anthracite region. But a brief outline of the systems in vogue at the bituminous mines will not be uninteresting, so far at least as they differ from those in use at the anthracite mines.

In the year 1887 a little more than one third of the bituminous coal output of the United States came from the Pennsylvania mines. Pittsburgh is the centre of the soft coal trade of that state, and the principal coal seam of the region is known as the “Pittsburgh bed.” It is included in an area about fifty miles square, and varies in thickness from two or three feet in the northwestern part, and six feet at Pittsburgh, to ten feet up the Monongahela River, and twelve feet up the Youghiogeny. The exhaustion of so vast a coal bed is a practical impossibility, and the questions that engage the attention of the mining engineer in these regions are not so much questions of the economy of coal as they are questions of the economy of labor. The coal lies near the surface, and the outcrops on the flanks of the hills and banks of the rivers are so numerous that most of the mining can be, and is, done by drift above water level. The outlay of capital required in opening a mine is therefore very small, marketable coal being obtained at almost the first blow of the pick.

Before mining operations are begun a complete survey is made of all outcroppings, and their differences in level are obtained. From this data a comparatively accurate knowledge may be had of the position of the coal bed under ground, as the dip of the seams is very moderate and uniform, and but few faults and other irregularities are encountered. It is then decided where to locate the mouth of the drift so that the entry can be driven in on the rise of the coal and the mine become self-draining. It is important, however, to have the opening at a convenient point near the river or railroad, and it is usually so made if possible, even though the dip should be away from the opening. The inclination is always so slight as not to interfere greatly with the hauling of cars, and it is not much of a task to make a separate opening for drainage. The coal seam is divided by vertical cleavage planes, running at right angles to each other, one of which is known as the butt cleavage and the other as the face cleavage. The main entries are driven in, if possible, on the face cleavage, as are also the chambers, or “rooms” as they are called here; while the entries from which the rooms are turned are always driven on the butt cleavage. The drift, or main entry, has an airway running parallel with it; sometimes it has one on each side of it. It is driven eight or nine feet in width, except where two tracks are necessary, in which case it is made from twelve to fifteen feet wide. These double or treble entries are parallel to each other, and are separated by a wall of coal from twenty-five to forty feet in width. Through this wall, at about every thirty yards, entrances, or, as they are called here, “break-throughs,” are made, having the same width as the entry. The height of roof in the entries of the Pittsburgh seam is usually five and one half or six feet in the clear. At right angles to the main entry butt entries are driven in pairs, parallel to each other and about thirty or forty feet apart, with break-throughs or cross-cuts for the passage of air, as on the main entries. From each of these butt entries, at right angles to them, and in opposite directions, the rooms are driven. They are made about twenty-one feet wide, with pillars between them twelve feet thick, and are not often more than eighty yards in length. They are usually driven to meet the faces of the rooms which are being worked from the next parallel butt entry, or are extended to that butt entry itself. At the point where the room turns off from the butt entry it is made only seven feet wide for a distance of from fifteen to twenty-one feet, then the room is widened out to its full width of twenty-one feet. The track on which the mine wagon runs is laid straight up the side of the room from the opening at the entry, occupying a clear space about seven feet wide. The rest of the room is well filled with the refuse which has been separated from the coal as mining has progressed, and the roof is supported by an abundance of props, or “posts” as they are here called. In one room, with an ordinary roof, about six hundred and fifteen posts would be necessary. The pillars are long, the distances between break-throughs averaging thirty yards. This is known as the “double entry” system, to distinguish it from the single entry system which was formerly in general use. The method by single entry consisted in driving the butt entries singly, about one hundred and sixty yards apart, and the face entries the same distance apart, at right angles to the butt entries, thus laying off the mine in large square blocks which were then mined out. The difficulty with this system was that from twenty-five to fifty per cent. of the pillars were necessarily lost, while by the double entry system, which now prevails, all or nearly all the pillars can be taken out.

Of course the features in the plan of each mine vary according to the special necessities of that mine, but in general they do not differ greatly from those that have been described.

PLAN OF A BITUMINOUS COAL MINE.