MODES OF MINING AND VENTILATION IN USE IN THE ANTHRACITE REGIONS.
It has been often said, and frequently most obstinately argued, that the modes of mining adopted in the anthracite regions of Pennsylvania were the necessary results of the peculiarities of the region, and that the improved systems of the English miners cannot be profitably introduced. We have invented a style peculiarly our own, and no attempts have been made to improve it: and that the general system is correct we have little room to doubt; but that it cannot be improved, we think a serious mistake, and one that is causing a loss of millions of tons of coal per annum to the landed proprie tors, and perhaps as many millions of dollars to the operators or miners. The English system, which is generally used in horizontal seams, will not do for direct importation here ; but a modification (?) of the two systems can be made available, and effect a decided improvement in our styles of mining and in the economy of coal and its production.
We will first give a page-illustration of the various plans now in use in our mines; and, instead of giving them in separate engravings, we have given seven plans in one illustration, for two reasons. First, our deep basins do not carry one invariable dip : we have seen them vary from 5° to 30° in the same seam: consequently, nearly all the plans represented are frequently required in one mine; and we give them also to show their absurdity. Second, the mode adopted brings the several plans before the eye, and enables us to present them comprehensively.
We will first explain the mode or general style here adopted, and the necessity for the changes in the modes of mining,—commencing at the shaft a. The design is for a large, double upcast and downcast shaft, with double hoisting-ways in each compart ment, and ventilated by furnaces, as shown at b,, or by fan, if desirable.
We assume this shaft to be sunk in the centre or deepest part of a basin, but that this basin is much narrower at one end than the other, and, consequently, that the angles of dip are proportionally steeper: this would necessitate modifications in the mode of mining the coal. At dips ranging from 5° to 30° the coal would not " run" in ‘‘ shutes," but the cars must be taken in the "breast" to the miner, and the coal taken direct from his hand. But when the dip is over 10°, the cars cannot be taken off at right angles with the gangways or main avenues: they must have an oblique course, in order to over come the grade. When the dip of the seam is over 30°, it becomes too steep to take the cars into the breasts, and "chutes" are resorted to. These are passages, or "ways,"
driven at right angles with the gangways, and kept open in the middle or at each side of the breast or chamber; into these the miner throws his coal, which, by its own gravity, slides down to the bottom, where it is loaded into the cars. The difficulties with this mode are twofold : first, when under 30° of dip, the coal will not run freely down the shutes ; and second, when steeper, the miner has much difficulty in taking up his timber and material.
Figure 140 illustrates clearly the form of the chambers, or breasts and pillars, made use of in all our pitching seams ; but the representation conveys simply the idea of the form of breast and pillar alternately. The air-courses, chutes, are not displayed.
In the plan or plans illustrated on page 416 we have introduced what may be called a double set of workings,—one on each side of the basin: consequently, two gangways are shown, and two regular return air-courses, with one inlet air-course. We do not advocate this plan, nor think that all these mainways are required. A single gangway in the centre of the basin would answer for a large business, and for the purpose of an inlet air-course, while the two parallel air-courses would be all that is desirable for the return air, provided such a consummation could be made to work under all the circum stances; but there the difficulty lies. A single gangway might answer where the basin is flat and wide, and where the cars can be taken into the breasts; but in plans 4 and 5 two gangways are absolutely necessary. While the pitch may be steep enough for the coal to "run" on each side, it is not so in the centre: consequently, the gangways must be along the foot of each dip, instead of the centre of the synclinal. The only change that could be made to work this centre basin from one shaft would be to dispense with the middle inlet air-course, and with one gangway to the left of the shaft: otherwise the whole complicated system is required to ventilate the works and mine the coal on a large scale. In regard to the plans displayed, it is not necessary that all the modes presented should be used, since Nos. 1 and 2, and 6 and 7, are much the same, and simply ventilated differently and mined in various forms to illustrate the modes in use. Like wise Nos. 3 and 5 are so near alike in practical effect that either could be used in the same place or on the same dip. With this explanation, we may go on to describe the modes or plans as given in the preceding engraving.