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.