The system of opening and working breasts differs somewhat from that in use in the Northern field. Beginning at such a distance from the foot of the slope as will leave a good thick slope pillar for its protection, a narrow shute is driven up from the gangway into the coal to a distance of perhaps thirty feet, at a height of six feet, and with a width of from six to nine feet. It is then opened out to its full width as a breast and continued up the seam toward the outcrop, not often breaking through to daylight unless an airway or manway is to be made. Parallel breasts are then laid off and worked out by the usual pillar and breast system. If the dip is less than twelve or fifteen degrees, the coal may be run down from the working face in a buggy, dumped on to a platform or into the shute, and loaded thence into a mine car standing on the gangway. If the dip is more than fifteen degrees the pieces of coal will slide down the breast to the shute, though if it is under twenty-five or thirty degrees the floor of the breast should be laid with sheet iron to lessen the friction and give greater facility in movement. In a steep-pitching breast a plank partition is built across the shute just above the gangway, to hold back the coal until it is desired to load a car with it. This partition is called a “battery,” or, if there is a similar partition to hold the coal in the breast, a “check battery.” In this partition there is an opening through which the coal may be drawn when desired, and through which the men may also go to their work, though a separate manway is often provided. In these steep-pitching breasts the miner works by standing on the coal which he has already mined, and which is held back by the battery, in order to reach the uncut coal above him. There are various systems of shutes, batteries, man ways, etc., in use, but all are based on the same principles. [Illustration: GROUND PLAN AND LONGITUDINAL SECTION OF CHAMBER.] When the gangway of the first lift has reached its limit in both directions, and the breasts from it have been worked up to their limit, the slope is sunk to another distance of three hundred feet, and the process is repeated. From the gangway of the second lift the breasts are not extended up far enough to break through into the gangway above; a wall of coal is left between that gangway and the faces of the breasts, from fifteen to forty feet in thickness, known as the “chain-pillar.” This is for the protection of the upper gangway against falls and crushes, and is also necessary to hold back water from escaping into the lower level. These lifts will continue, at distances of about three hundred feet apart, until the synclinal valley is reached.