So far, however, in this mine which we are supposed to be working, not a tap of a drill nor a blow of a pick has been made into the coal on the lower side of the gangway save where the sump was excavated at the foot of the shaft. If this shaft has been sunk nearly to the bottom of the basin or synclinal axis, a short tunnel may be driven from the main gangway through the rock or upper bench of coal across the valley to the rise of the seam on the other side. A new gangway may here be driven right and left, and this area of coal be made tributary to the shaft already sunk. It often happens that a large body of coal lies between the main gangway and the synclinal axis, for these two lines may diverge greatly as they recede from the shaft. But chambers cannot be driven down from the main gangway owing to the difficulties of transportation and drainage. It therefore becomes necessary, in order to work this area, to sink a slope from the main gangway down to or toward the synclinal axis, and from the foot of this slope to drive a new gangway. From this new gangway chambers will be opened extending up the seam to the line of the main gangway, but not generally breaking through into it. The coal is run down to the lower level gangway, hauled to the foot of the slope, and hoisted up it to the main gangway. It is apparent, however, that the inclined plane system cannot work here; the conditions are reversed; the loaded cars are drawn up and the light ones are let down. To do this work it is necessary to bring into use a small steam stationary engine, or one working by compressed air. A common method is to locate the steam engine on the surface vertically above the head of the underground slope, and to carry power to the sheaves below by wire ropes running down through bore holes drilled for that purpose. The system of slope mining by lifts, which is in common use in the Middle and Southern anthracite districts, has been explained in a preceding chapter. In this system the sump is always made by extending the slope a short distance below the level of the gangway. This gangway is driven from the foot of the slope to the right and left in the same manner as in the Wyoming region, except that, the seam being so greatly inclined, the gangway roof, or a part of it at least, will usually be of coal instead of slate or rock, and in very steep pitching seams the airway will be almost vertically above the gangway. The gangway is not usually so crooked as where the workings are flat, and having been started only three hundred feet down the slope from the surface, it often follows the coal to some low point on the line of outcrop, and is then known as a water level gangway, which is practically the same as a drift.