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. [Illustration: PLAN OF A BITUMINOUS COAL MINE.] The method of cutting coal here is also peculiar to the soft coal mines. The miner has a pick with sharp, pointed ends, and with this he cuts a horizontal groove or channel, from two and a half to three and a half feet deep across the entire width of the entry or room. This groove is cut in that horizontal section of the face known as the bearing-in section. It may be in the bottom layer of coal, or it may be one or two feet above the bottom. The process itself is known as “bearing in,” “under cutting,” “holing,” or “undermining.” While he is at this work the miner must lie on the floor of the room, partly on his side, but with hands and arms free. When the horizontal groove has been completed a vertical groove similar to it in size and shape is made at one side of the face. These channels are sometimes cut with mining machines having compressed air for a motive power. This machine is small but powerful. It is placed on a low inclined platform at the face of coal, and is operated by a man called a “runner.” The inclination of the platform causes the machine, which is on wheels, to gravitate constantly toward, and to press against, the face of coal. The compressed air cylinder drives a piston-rod to which is attached a steel bit two inches in diameter projecting from the front of the machine. This bit strikes the coal with sharp, swift blows, chipping it out in small fragments, and eats its way rapidly into the seam. The compressed air is carried to the machine in an iron pipe from the compressing engine, which is located at the mouth of the mine. When a machine is used, seven men usually work three rooms. Three of these men are contractors or partners, three of them are laborers employed by the contractors, and one of them, called the “scraper,” is a laborer employed by the coal company.