"When there are good grounds for supposing that coal is likely to be found in any particular locality, before a pit is sunk the preliminary process of "boring" (q.v.) Is resorted to, in order to detertnine whether it actually does exist there, and if in quantity sufficient to make the mining of it profitable. The usual mode of " winning " or reach ing the coal is to sink a perpendicular shaft; but somethnes a level of) cross-cut mine, .and at other times an inclined plane or " dook," is adopted. Before the introduction of pumping-engines, all coal-workings were drained by means of a level mine called a day level, driven from the lowest available point on the surface, and no coal could be wrought at a lower depth than this, because there were no means of removing the water.
When the shaft has been sunk to the necessary depth, a level passage, called the dip head, or main-level, is first driven on each side, which acts as a roadway or passage. and, at the same time, as a drain to conduct the water, which aceumulates in the workings, by means of gutter on one side, to the lodgment at the bottom of the shaft. This
level is the lowest limit of the workings in the direction of the dip, and from it the coal is worked out as far as is practicable along the rise of the strata. There are two principal methods of mining the coal. One is termed the "post-and-stall" or " stoop and-room" system, and is used for thick seams; the other is called the " long-wall" system, and is adopted for seams under 4 ft. in thickness. In a mine wrought on the post-and stall plan, the coal is taken out in parallel spaces of say 15 ft. wide, intersected by a similar series of pa-ssages right angles. Between these "rooms," as they are called, "stoops" of coal, about SO ft. each way, are left for the support of the "roof" of the seam. Larger stoops are left at the bottom of the shaft, in order to secure greater stability there. There is a modification of this plan adopted at Newcastle, called the " board-and-pillar" method, by which a certain number of the stoops or pillars are removed alto +1..„ #.11c.