ing. They are numbered from 1 to 10, 10 being nearest the discharge end of the conveyor. The man that has section 10 one day is moved to section 1 the next day, each man going up one place. This change is made daily because the man farthest from the discharge end of the conveyor finishes loading first; the conveyor is loaded most heavily at the discharge end, and the men there have less room to load into.

Mine cars are run under the end of the conveyor (fig. 22), which discharges the coal directly into them. One runner attends to the operation of the conveyor and one topper-off oversees the loading of the cars. If the run is heavy, an extra topper-off may be necessary.

As soon as the coal is loaded out, one miner, called a "plugger," goes along the wall and straightens it, either with a pick or by shooting if necessary, so that the cutting machine will have a straight face on which to work.

The night timber boss comes on with four laborers; with the assistance of the machine runner and a helper called a "kailer " they move the motor and conveyor over 5y2 feet, making use of the coal cutter and some chain hoists. The ^y2-ioot movement equals the depth of the undercut made by the machine. As soon as the conveyor is moved it is reversed, and timber is sent up the conveyor to the working place. One of the five timbermen sends up timber, and the other four unload at proper points and build cogs. These cogs are 4 by 4 feet and set about 5 feet apart, staggered in close rows, as Figure 21 shows.

While the timbermen are thus employed, the machine runner and kailer proceed with their cutting, which ordinarily takes about six hours. The night miner and laborer drill about 14 holes in the 220-foot face and shoot the coal down for the next day's loaders.

Coal cars with a capacity of 3 tons can be loaded in two minutes, and the conveyor chute will hold three carloads of coal. The conveyor can carry as heavy a lump of coal as two men can lift. The largest size lump that can be carried is determined solely by the clearance between the conveyor and the roof.

In this manner, the face of the longwall is kept advancing until the timbers begin to squeeze. When the work stops, an 18 or 20 foot pillar is left. A new doghole is then driven up, and the work is continued until another squeeze occurs. When all of the heading is worked out, these pillars are pulled; thus no coal is lost and the extraction is almost perfect.

When the coal over a large area is removed, the roof rests on wooden cogs which gradually crush under the pressure, letting the

ing. They are numbered from 1 to 10, 10 being nearest the discharge end of the conveyor. The man that has section 10 one day is moved to section 1 the next day, each man going up one place. This change is made daily because the man farthest from the discharge end of the conveyor finishes loading first; the conveyor is loaded most heavily at the discharge end, and the men there have less room to load into.

Mine cars are run under the end of the conveyor (fig. 22), which discharges the coal directly into them. One runner attends to the operation of the conveyor and one topper-off oversees the loading of the cars. If the run is heavy, an extra topper-off may be necessary.

As soon as the coal is loaded out, one miner, called a "plugger," goes along the wall and straightens it, either with a pick or by shooting if necessary, so that the cutting machine will have a straight face on which to work.

The night timber boss comes on with four laborers; with the assistance of the machine runner and a helper called a "kailer " they move the motor and conveyor over 5y2 feet, making use of the coal cutter and some chain hoists. The 5%-f oot movement equals the depth of the undercut made by the machine. As soon as the conveyor is moved it is reversed, and timber is sent up the conveyor to the working place. One of the five timbermen sends up timber, and the other four unload at proper points and build cogs. These cogs are 4 by 4 feet and set about 5 feet apart, staggered in close rows, as Figure 21 shows.

While the timbermen are thus employed, the machine runner and kailer proceed with their cutting, which ordinarily takes about six hours. The night miner and laborer drill about 14 holes in the 220-foot face and shoot the coal down for the next day's loaders.

Coal cars with a capacity of 3 tons can be loaded in two minutes, and the conveyor chute will hold three carloads of coal. The conveyor can carry as heavy a lump of coal as two men can lift. The largest size lump that can be carried is determined solely by the clearance between the conveyor and the roof.

In this manner, the face of the longwall is kept advancing until the timbers begin to squeeze. When the work stops, an 18 or 20 foot pillar is left. A new doghole is then driven up, and the work is continued until another squeeze occurs. When all of the heading is worked out, these pillars are pulled; thus no coal is lost and the extraction is almost perfect.

When the coal over a large area is removed, the roof rests on wooden cogs which gradually crush under the pressure, letting the old railroad ties, bridge timbers, or anything that can not be used for other purposes. This material, however, can not be recovered.

ADVANCING SEMILONGWALL DP THE PITCH

Every anthracite operator is striving to devise some 'method of mining his thin beds of coal that will enable him to produce this coal at a profit. Devising these methods brings out many interesting features, but it often happens that operators have not utilized methods devised by others who have studied similar problems. As a result virtually every method of mining thin beds presents some new features. These various discussions have included a number of so-called longwall or semilongwall methods; some of these have been similar, but. some show very marked differences. The method of mining described below has features somewhat similar to other methods already described; however, it is practically distinct as a whole.

Beds mined.—At the Northwest colliery of the Temple Coal Co., near Carbondale, Pa., the thick beds have been virtually exhausted, and only the three Dunmore beds, which are comparatively thin, are left. At present the workings in the No. 3 Dunmore are of the ordinary room-and-pillar type because they underlie a flooded area in the old Clark bed, and enough pillars must be left to support the roof and prevent a squeeze that would drown out the Dunmore workings. The No. 2 Dunmore bed is not being worked at present, as it is thinner than either the No. 1 or the No. 3.

A semilongwall system of mining is being used in the No. 1 Dunmore bed. The coal dips approximately 3°. The roof is hard black rock and does not fall readily. A section of the bed is given in Table 25.

Table 25.—Section of Dunmore No. 1 bed at Northwest colUery

The No. 2 Dunmore, which is not being worked, lies 75 feet below this bed, and 25 feet below it lies the No. 3 Dunmore, which is being first mined in part of the area. Above the No. 1 Dunmore lies the Clark bed, which has been completely exhausted except for a few pillars at the foot of one of the old slopes. Table 26 gives analyses