Assuming that the driving of the chutes includes the opening of the breast to connect the air currents, and the measurement is up to the line of the heading and also across the breast, which is the actual ground to be driven, then the relative cost would be about as follows: yards, at $2.50 per yard. Heading through pillar, 6 x 5, One battery at $4. Four sets chute timber at $2.50 per set Five sets heading timber at $2.50 per set Planking 6 x 24, 144 feet at 3 cents per foot. Platform, 9 x 6, planking, 54 feet at 3 cents per foot $30 00 20 00 20 00 4.00 10 00 12.50 4 32 1 62 9.00 Total cost. $111 44 On moderate dips where the breasts can be worked empty, the miner is then paid by the car, and the opening of the breast is also paid by the car and yard both. Plan No. 9 (Fig. 115) is seldom adopted, and for general purposes has little to recommend it. Where the seam is thin, the top weak, the pillars 5 or 6 yards, and the breasts 9; where the top falls and the bottom is apt to slide off and mix with the coal by drawing the breast, this plan may be satisfactory, but only where the ventilation does not depend on the tightness of chutes and especially where the shortness of the lift renders cheapness an important consideration. Under such conditions the plan is to run all the extra coal from the face of the breast down the manways, so that the coal in the breast is not moved until it is finished; then it is loaded as fast as possible at both chutes before the top falls and mixes with the coal. As shown on the diagram (Fig. 115), the chute is opposite the pillar, is driven up 6' x 9' for about 8 yards, with a manway 3 feet wide divided off by a plank partition; it is then widened out on both sides into each breast, so that coal from both can be run down the one chute. The top of the chute manway is covered by a man-door to keep out the coal and hold in the air-current; the batteries are only strong "juggler" props which separate the breast from the manway, with a drawhole left at the bottom; when the coal rushes down to fill the chute. it does not fill the slant, it not being steep enough; therefore; the miner can climb from the top of the chute manway to the bottom of the breast manway on the loose coal, or on a plank laid on "juggler" props placed across the chute. The loose coal rests on the pillar, and the starter can fill the chute or draw from both when necessary. This plan is perhaps best suited for small operations above water-level on thin, steep seams where an airway to the surface costs little and the breasts are so short that it will not pay to spend much in opening them, this being a kind of temporary arrangement to suit such conditions. The cost of opening breasts on this plan is as follows: the batteries being only three heavy "juggler props" close together, may be both considered equal to one battery, then 1 chute 6' x 9', 8 yards at $3 2 slants, each 6 x 6, and 3 yards at $2.50 $24 00 15.00 20 00 4.00 4 sets chute timber and 3 sets heading timber in each slant at $2.50. 10 sets 25 00 Battery timber, $9 9 00 Planking 6 x 246 x 9 198 square feet at 3 cents 594 Total cost $102 94 Plan No. 10 (Fig. 116) dispenses with breast manways by driving a traveling way up through the center of every alternate pillar, thus making one manway serve 2 breasts. This plan of working breasts is sometimes adopted in thick seams where the dip is under 50° and pillars and top strong; it saves the expense of timber for breast manways, but requires more pillar headings, so that the expense of working the breasts is about equal; but the air is not kept so close to the face, and the miner has only the pillar heading as a refuge from danger; therefore, it is not suited for coal which gives off much gas. It will not be satisfactory on steep dips, because the coal in the breast does not tail far back, but fills square up and closes the pillar headings, although they are driven next the roof. We have seen this plan tried where the bottom, to the depth of 18 inches, became, loose and slid off among the coal; the sinking of holes on both sides for juggler props helped to cut the bottom loose, and the manway was driven in the pillar to obviate that difficulty, but it effected little improvement, cost more and injured the ventilation, and was therefore finally abandoned. It was found that with 7 to 9 breasts working in one tier, there was always some miner who had his pillar heading blocked, so that it was neither efficient nor convenient for dealing with gas, and on angles above 50° with seams less than 10 feet thick, it is impracticable, and in the opening of the chutes a heading had to be driven from every alternate chute, nearly the width of both breasts, and the "blind" pillar between them, before the air connection could be got through and the ventilation established. This was a great inconvenience where much gas was given off, as it required a hand fan to keep it ventilated until the connection was made. Except for special conditions, this plan of working breasts is now obsolete. The relative cost of opening on this plan will be about as follows: Chute 9' x 6' with traveling way divided off by plank, 10 yards at $3 per yard $30 00 Heading across of 10-yard pillar, 5 x 6, 5 yards at $2.50 .. Heading across breast from side of 9-foot chute about 7 yards, no timber, at $2 12.50 14 00 Heading through of 6-yard blind pillar, 6 x 6, timbered, at $2.50. 5 sets chute and 5 sets heading timber to secure the half of each pil- = 7 50 4.00 25 00 234 square feet at 3 cents 7 02 Where an airway can be driven over the chutes the breasts can be ventilated in pairs or groups by connecting the fan to alternate pillar manways so that the air would be exhausted from the upper end of the breasts into the one set of manways. and the air find its way up the others. Plan No. 11 (Fig. 117) is nearly the same as plan No. 10 (Fig. 116), only the manway is driven straight up from the gangway, which involves an additional expense of 10 yards at $2 = $20. The chutes being opposite the middle of the breast, there is a shorter distance to be driven before the connection for the air current can be made. The manway chute is more convenient for the coal mined in it, but being in the top part of the seam while the chute is on the bottom, there is always a step or offset to be made in the manway, while in plan No. 10 (Fig. 116) this is overcome by slanting both halves of the heading up through the seam, which also carries the coal into the chute and prevents it from running out and obstructing the track by the miners traveling in it. This plan is about equal in all respects to plan No. 10 (Fig. 116), but costs $20 more. Plan No. 12 (Fig. 118) is adapted to steep dips, 60° up to perpendicular, with conditions which do not admit of wide breasts or pillars, and the coal free in running through the battery. As shown on the diagram, the chute is driven across the strike of the seam to reduce the grade to about 25°, so that the coal will just move down by its own weight. From the front of the battery the heading is slanted through the pillar to form the manway chute of the next breast. A plank battery with a mandoor next the roof and a drawhole in the bottom serves as a check and air battery to load the coal from, and at the same time hold the air current in the breasts; |