produced by working the coal will not affect the slope, stalls or "breasts" are opened off at or about right angles-i.e., up the rise. These are the working places, which are separated from each other by a solid rib of coal. They are usually driven for a distance of from 80 to 100 yards, and are never holed through into the gangway above, but are driven up to within 10, 15, or 20 yards of it, leaving a rib of coal, called "the chain pillar," for support. Breasts. are opened off the gangway as fast as room is provided, and when the first breasts are exhausted the men are moved forward. The width of the breasts is governed by the strength of the roof, the firmer this is the greater the width. Breasts vary from never less than 6 yards to never more than 12 yards wide. When the coal is quite flat the breasts are opened at right angles to the gangway, but where the dip is too steep to allow a waggon to be used in the breast, if so driven, it is opened at an angle to the gangway, thus decreasing the inclination. The inclination of the bed usually limits the length of the breasts from 300 to 500 feet, and coal lying at a greater distance from the gangway is mined from a second series of breasts opened from a second gangway driven above the first one.

By the driving of manways and "chutes" (shoots), the rib of coal between the gangway and heading is divided into pillars, called "stumps," which are always made larger than usual where the roof is strong. They form the supports which keep open the gangway, the main entrance to each district which must be preserved. Where the roof is soft, the breasts break down in short lengths without throwing much weight on to the adjacent coal, but with a hard tenacious roof a considerable extent of workings may remain open, to collapse suddenly, producing a crush which may extend to the gangways, unless the stumps are made large, say 15 yards; more often they vary from 7 to 10 yards.

The distance to which the gangway is driven on each side of the slope, or, in other words, the lineal distance worked from a single opening, is dependent on the cost of haulage and on the cost of keeping the gangway open. Endless rope and chain haulage are not used, but if the coal is hard and the roof good, it is often cheaper to mine coal lying 2 miles from the slope than to open a new one, while if the coal is soft and the roof bad, it may be cheaper to open a new slope than to attempt to keep I mile or less of gangway open.

The methods of opening the breasts vary with the nature of the roof, the quantity of ventilation required, and the steepness of the seam. Between the angles of 25° and 30° the mined coal will slide on the floor of the breasts, but not at any violent rate. From 25° down to 15° the coal will not move unless sheet-iron plates are laid on the floor. For this reason up to 30° the breasts are worked empty, that is to say, the coal is loaded as it is got; over that angle the coal when mined rushes down the breasts with considerable force, and would dash into the gangways unless prevented by some obstruction, which takes the form of a strong "battery or regulator, built of round timber props partially covered with planks, leaving an opening through which the coal can be run out as required. Roads are kept up the sides of the breast by the use of inclined props called "jugglers," which are notched into the floor and side and are covered with 2-inch planking. These form the intake and return airways, the

whole width between being kept full of loose coal. When the breasts are worked out, the pillars are robbed by taking off from each as thick a slice as possible.

In very steep breasts it is impossible for a miner to keep up to the working face, as he has nothing to stand upon, and it is therefore necessary either to leave the loose coal in the breast or to erect some artificial support. A common method of opening out work in such cases is illustrated in Fig. 240. The breasts are opened by driving in two shoots for a distance of 8 to 10 yards, connecting them by a cross drivage, and then carrying the working forward its full width. Four strong props, a, are set just above the pillar so cut off, and against these, two log batteries are built, in each of which is left an opening, say 4 feet square, that will permit large lumps to pass through freely. Roads are kept

up each side of the breast by the use of inclined props ("jugglers"), shown in position in Fig. 241, which is a section across a breast. The surplus coal may be drawn out at the bottom through the opening in the battery, but is more frequently sent down the man-ways; the loose coal is allowed to remain undisturbe until the breast is driven to the limit.

Gang way.
Fig. 240.

The advantage in this system is in having two chutes, as the coal may be rapidly drawn from the breast if there is any danger apprehended of its being covered by falls; it also frequently happens in two-chute breasts that when one passage becomes blocked by coal the other will continue open, and that in time the movement there will free the coal in the other. The disadvantages are numerous. Stoppage of both chutes are common, and as a consequence, ventilation is not only suspended in the breast directly affected, but often in all others past it. Unless an additional manway is driven through the stump pillar between the breasts, the men have to travel through the battery chutes. With two chutes the coal is drawn from the side of the breasts, and the movement often unseats the jugglers and breaks in the man-ways.

Fig. 241.

For these reasons breasts are often started with one chute in the centre. Where this crosses the heading three strong props are placed along the centre line, and the breast is afterwards widened out to its full size and carried forward. The props at the heading form the battery, and also a stopping to direct the air current into the breast man-ways. Should anything break down in the latter, the stopping can be removed and the air current sent direct to the inside breasts.

Man-ways are driven through the pillars between each pair of breasts. An elaboration of the above, introducing a return airway (Figs. 242 and 243), is highly recommended and largely adopted where the seam is steeply inclined, the coal free, and apt to give off quantities of gas. For greater security the gangway is driven along the roof of the seam, this position also allowing the coal chutes to be driven at a smaller angle, giving the loaders greater control over the movement of the coal. The main chute is driven 9 to 10 feet wide for a distance of 8 or 9 yards where the battery is placed. From this point up, the breast is widened out to its full dimensions in a distance of 5 to 7 yards. A space of about 3 feet wide is partitioned off from the coal chute, serving as a man-way for the starter to reach the battery from the gangway. A man-way chute, 6 feet by 6 feet, is driven up in the centre of the pillar for about 8 yards and then branched off right

and left ("slant chutes"), joining each breast where it is of full width. The main feature of the plan is an air course, c, driven against the top above the gangway, and connected with the manways ee between each breast, by the passages ff. This air course is not generally in use, but only when the breasts are exhausted, or repairs are necessary to the man ways dd. Where the coal is not very strong and liable to run, that is to say, break away from the solid without mining, this plan possesses many advantages; the breast can be worked in the bottom bench only, and the excess coal run down the slant chutes. When the breast is finished the loose coal it contains can be drawn out at the three chutes.

Where the seams are not very thick and the coal is soft, especially when the impurities are large, breasts are worked "on batteries,"

that is to say, rows of props are set across the stall every 15 to 20 feet as it progresses, and planks nailed to them, forming platforms, on which the men can stand up to their work. The clean coal is passing away through the breast man-ways, and the refuse thrown back into the space occupied by loose coal in the systems previously illustrated. This method was used in hard, clean coal, but in the absence of refuse, which is partly packed against the batteries or plank dams, shots throw down the coal with such force that the props, &c., are often swept away; the danger of this, especially in a clean seam, where the breast would be empty below the battery, and the damage to the coal by smashing has led to its abandonment in such cases.

In seams pitching 12° to 13°, breasts are worked as "on batteries," only batteries are not required, as the men can stand up to their work without support; the chutes will be laid with sheet iron. Where the inclination is still smaller, the waggons will be taken direct to the breast, a good tramroad being kept up on one side. In the latter case the resemblance between anthracite mining and the double stall method of South Wales becomes very apparent.

When the gangways and breasts have been opened out to the furthest distance that economical working will allow, the pillars between the breasts and the stumps are robbed or reduced, beginning at the farthest distance and bringing the work back to the outlet or slope. This procedure, by removing the pillars which support the roof, often brings on large subsidences or caves in."

France. Both the methods already described differ in one important feature from the mining of thick seams as practised in France, as the only stowing material, if any, used in the chambers is the small quantity produced from the bands of inferior coal or dirt intermingled with the seam, and there is rarely any attempt to use even this small quantity in a systematic manner. On the Continent, complete stowing of the workings is the rule rather than the exception, and huge quarries at the surface are worked for the sole object of supplying material, which is sent down into the mine and used for gobbing up the workings. Care is taken that the circulation of the tubs is as nearly automatic as possible; they gravitate from the screens, where they are emptied of coal, to the quarry, where they are filled with rock, and, after being raised to a suitable height by mechanical means, gravitate to the pit top where they are lowered into the mine. The workings underground are generally to the deep of the pit bottom, and the tubs of rock are delivered to the highest point of the working place before being emptied, in order that the gobbing material can fall into the required situation. Shovelling it into position is out of the question owing to cost.

Then, again, the thick seams are divided up into slices, each of which is taken out by a separate working. Two plans are adoptedin one the slices are horizontal and are taken across the bed of coal (from roof to floor) from inclined planes driven from one level to the next above it, the development and opening out of the levels and inclines being similar to that adopted in the rearer coals of North Staffordshire. In the second method roads are driven along the strike of the seam at regular intervals apart, and the successive slices are removed by a series of inclined stalls driven to the deep and parallel with the roof and floor of the seam.

In hard coal, the inclined method of working is preferable for a seam dipping less than 15°, unless it be irregular or contain old workings, or unless it be of too great a thickness, when the method of horizontal slices should be resorted to. In seams dipping 15° to 30° the inclined method is also advisable, especially where the coal contains bands of refuse, but the horizontal method is the only one applicable to deposits of irregular form, or to seams dipping more than 30°, when the inclined slice becomes too dangerous, while owing to the fact that the working places are level it also possesses the advantage of rendering haulage easy.

The method of working by inclined slices at Blanzy Colliery in a seam 15 feet thick, dipping 1 in 5, as described by Mr. L. Mathet, consists in dividing the bed into two equal parts, taking the lower one out first, and then following on with the upper layer before the first is finished. The method of opening out, and the details of the working places, are shown in Figs. 244 to 249. A commencement is made by opening out in the bottom slice on one side only of an incline driven along the dip of the seam, two narrow roads (xx', Fig. 245), 10 yards apart, and continuing them until the boundary or the extremity of the district is reached, when they are connected by a cross-road, 1,

2, driven parallel with the floor. The stall so formed is then worked backwards towards the incline, and the space behind the workmen packed with refuse. The gobbing material is brought in along the higher level, and is lowered into the working places by small winches worked by compressed air, which also serve to pull up the tubs loaded with coal to the levels from whence they can be conveyed to the incline by horses. At the end of twenty days a piece of the lower slice of coal, represented by shading in Fig. 245, has been removed, and a third level road, x", has reached the boundary and has been connected with a' by the cross-stall 3, 4. The coal here is also worked back towards the incline, until at the end of forty days the lower slice has been removed to the extent shown by the shaded portion in Fig. 246, while a fourth winning headway, x", has been driven to the boundary and connected with a" by the stall 5, 6.

The development and winning of the lower slice still continues, but at this period workings are also opened in the upper lift. All the stalls have hitherto been driven parallel with the inclination of the bed, but it is obvious that if the road (c, Fig. 246) be started from the level a' and be driven horizontally it will soon reach the roof of the seam. It is then continued to the deep, over the gob of the first lift, and a face opened, and also brought back towards the incline, as will