Off from the main or side headings of a hard-coal mine °breasts° or °chambers° are opened. In bituminous fields these are known as "rooms.° A tunnel or nec.k 40 to 60 feet long may connect the room proper with the main passageway. Beyond the neck the cham ber may broaden out to a width of 30 or more feet, continuing indefinitely. The coal be tween the rooms forms what is known as a °rib° or °pillar? As the rooms begin to broaden to their maximum widths, timber props are placed between the floors and ceilings to support the loose rock and earth. Apart f rom supporting the great mass of solid rock, they are of little service.
When all the coal that it is practical to mine in the chambers has been extracted, the work of drawing the ribs between the rooms is be gun, eventually allowing the rock above to cave in. In addition to securing the coal in the ribs, this process is necessary, that the weight of the mountain bearing upon the entrance to the mine may be lightened. As mining progresses, the weight is thrown upon the main heading, until, were it not for the drawing of the ribs, this main passageway would close.
When drawing a rib, the sof t-coal miner keeps but one car beside him. He cannot tell how much of the rib he will able to remove before the rock above his head will fall. The first warning of approaching danger is a drum ming noise from the layer of stone overhead. Sometimes this noise may be heard hours be fore the final crash; in anthracite mines it may be perhaps weeks before. Again, it may come with marked suddenness.
The coal, when brought to the surface, is screened, and at many bituminous mines is then shipped as lump and slack. Sometimes it is broken and washed, and in the anthracite re gion of Pennsylvania, where coal is shipped in seven or more sizes, the coal, as it comes from the mine, is passed through the breaker.
A modern coal breaker built on the side of a hill at Mocanaqua, Pa., will serve to illustrate the construction and operations connected with this important branch of coal-production. This breaker is 300 feet in length and 180 feet in height. It is capable of turning out 1,000 tons of clean coal per day. Some breakers have a much larger capacity. The Mocanaqua breaker was originally built at a cost of $50,000, but with recent improvements and the installation of the latest machinery its total cost reaches $100,000. It is heated by steam.
The anthracite is brought to the head of the breaker over a little railway leading from the mine in the side of the mountain. The coal, when
dumped from the cars, passes over a screen 30 feet in length, through which the fine coal sifts. The big chunks next pass to the breaker proper, where rolls with sharp teeth crush it. It next runs into a screen which is lindrical in shape, and not unlike a locomotive in appearance. As the coal is handled in this device, it falls through perforations of different sizes, each size dropping into a sepanoe chute. On benches at intervals on these ,, sit the breaker boys, presided over by a Juryman. As the coal passes slowly down the chute at their feet, these lads pick the slate from it and throw the refuse into a parallel chute. The inex perienced boys are always at the upper end of the chutes. They succeed in picking a part of the slate from the coal, and then it passes to the next workmen in line, who continue the operation until, by the time the product has reached the' boys at the bottom of the chutes, it is pretty well cleaned. The coal is also washed to free it from sulphur. From the chutes the various-sized coal finds its way into bins, from which it is discharged into cars.
Mechanical contrivances for sorting have recently been installed at great cost in modern breakers. These inventions are spiral in shape, and provide for ridding the coal of much of its slate by centrifugal force. But even with these machines the final operation must be per formed by boys or men.
A large amount of the soft coal of Ohio and Pennsylvania is brought to the lower harbors of the Great Lakes, bound for the Northwest and Canada. The cars which carry this coal have a capacity of 100,000 pounds, whereas, in the early days of the coal industry in this coun try, coal cars scarcely carried 1,800 pounds. On reaching the lake ports, coal for Canada may be taken 60 miles across Lake Erie in car fer ries. But the bulk of the coal that comes to the lake ports is unloaded directly into the holds of lakt ‘us,e1,, In. ui ins of most wonder ful and massive machines, which pick up a 50 ton car and dump its ,oments as quickly as a pail of coal could be emptied into the magazine of a stove. Some of these machines can be operated by three men, and yet have a capacity of 500 tons per hour. A large and modern coal vessel will carry a coal cargo of 6,000 tons. More than '2,500,000 tons of coal have gone to the head of the Great Lakes in a single season.