Mining methods.—The bed lies 200 to 300 feet below the surface. Where it is undisturbed, the coal is very hard. In the older workings the gangways and airways are driven 24 feet wide. Bottom is taken up in preference to brushing the top, and the rock is gobbed; this procedure reduces the gangways to about 12 feet. In new work the gangways and airways are only 12 feet wide; the breasts are 24 feet wide and on 50-foot centers, leaving 26-foot pillars. In the later work the centers are increased to 60 feet and the pillars thereby increased to 36 feet. When the Top George was opened the work started from a direction different from that when the Bottom George was opened. The gangways, therefore, had to be driven in a different direction, so that the pitch of the coal would make them self-draining, and they could not be columnized. As far as possible the company has attempted to keep the openings in the Top George directly above those in the Bottom George, but has found this to be practically impossible because of inaccuracy in the early surveys of the Bottom George bed, which was mined much earlier, and because of the difficulties mentioned in the preceding paragraph. The accompanying map (fig. 18) illustrates this condition exceedingly well. The great problem in mining this coal bed is to keep the roadways open. As first mining progresses in the upper bed, weight is thrown on the pillars, and where the pillars in the upper bed overlap or come directly over the openings in the lower bed they crush through; this tends to bring down the roof over the roadways. As the coal company desires to keep the roof intact, bottom must be taken up continually. Moreover, the bottom of the Top George bed contains fire clay which swells and heaves; this heaving tends to fill the gangways further and necessitates continual taking up of bottom. As the bed has a heaving bottom and a sinking roof, the first and second mining of the coal in this bed evidently can proceed only with con Operating data.—Four gangs of four or five men each are employed every night in keeping the roads cleared and removing fire clay. In the whole territory 110 men are employed, including these gangs, and they are mining daily only coal enough to fill 70 cars having a capacity of 88 cubic feet, water level. Less than 1 car of coal is therefore produced for each man employed in the district, making the cost rather high. Driving of the wide gangway and airway has helped greatly to reduce mining costs, owing to the saving effected by not having to load out the rock that has to be taken up in the airway and gangway. The coal itself lies largely on a pitch, and in places it can be run over sheet iron from the face to the mine car. Where the pitch is too nearly flat for the coal to run, hand-pushed buggies are being used on roads. Where the coal is flat, bottom is taken up to permit the mine cars to enter the chambers. The map (fig. 18) shows that the Bottom George bed has been robbed, but not the Top George, with the result that matters are complicated further because the floor of the Top George is broken and the pillars somewhat crushed; thus conditions are made particularly unstable and the difficulty of removing coal from the upper bed, only 12 to 20 feet above, is enhanced. LONGWALL AND SEMILONGWALL MINING Four examples of longwall or semilongwall mining have been selected to show the different methods that are being used in the anthracite region. The first example described is really not a true longwall or even semilongwall, but is a modification of the room-and-pillar mining that might be classed as semilongwall. The other three are true longwall methods, and two have been successful; the third is really in the experimental stage, and the company has abandoned other methods tested and is now starting a new one. DOUBLE AND TRIPLE CHAMBER MINING IN THE TW0-P00T BED The production from the thicker beds of coal is decreasing at a number of collieries in the anthracite region, and working of coal therein will eventually become unprofitable unless some method is devised for maintaining production. However, many collieries have a number of thin beds of coal which have not as yet been considered economically workable, but might be considered so if coal could be Operating data.—Four gangs of four or five men each are employed every night in keeping the roads cleared and removing fire clay. In the whole territory 110 men are employed, including these gangs, and they are mining daily only coal enough to fill 70 cars having a capacity of 88 cubic feet, water level. Less than 1 car of coal is therefore produced for each man employed in the district, making the cost rather high. Driving of the wide gangway and airway has helped greatly to reduce mining costs, owing to the saving effected by not having to load out the rock that has to be taken up in the airway and gangway. The coal itself lies largely on a pitch, and in places it can be run over sheet iron from the face to the mine car. Where the pitch is too nearly flat for the coal to run, hand-pushed buggies are being used on roads. Where the coal is flat, bottom is taken up to permit the mine cars to enter the chambers. The map (fig. 18) shows that the Bottom George bed has been robbed, but not the Top George, with the result that matters are complicated further because the floor of the Top George is broken and the pillars somewhat crushed; thus conditions are made particularly unstable and the difficulty of removing coal from the upper bed, only 12 to 20 feet above, is enhanced. LONGWALL AND SEMILONGWALL MINING Four examples of longwall or semilongwall mining have been selected to show the different methods that are being used in the anthracite region. The first example described is really not a true longwall or even semilongwall, but is a modification of the room-and-pillar mining that might be classed as semilongwall. The other three are true longwall methods, and two have been successful; the third is really in the experimental stage, and the company has abandoned other methods tested and is now starting a new one. DOUBLE AND TRIPLE CHAMBER MINING IN THE TWO-FOOT BED The production from the thicker beds of coal is decreasing at a number of collieries in the anthracite region, and working of coal therein will eventually become unprofitable unless some method is devised for maintaining production. However, many collieries have a number of thin beds of coal which have not as yet been considered economically workable, but might be considered so if coal could be |