By adopting the boundary or panel and barrier system, all this difficulty would be overcome, and by the use of inclines the cars could be taken into any breast or chamber, having 40° or less of dip, with ease and economy; and not only would this improve ment be effected, but a greater one would be accomplished by the means it offers for the extraction of all the coal, and the ability to sweep the workings constantly with pure and fresh air-currents. In flat seams there is more choice of the ways and means of working the coal; but we can advise no better mode than the boundary system, and the advantage of dispensing with inclines, since the cars may be taken by horses into any part of the mine where the seams are of sufficient size. When they are not, the roof may be taken down or the bottom dug up to admit them, or "trams" may be used.
The modes of mining bituminous coals are perhaps more numerous than those employed at the anthracite mines. In the extensive English mines, perfect systems are now adopted, which by extensive practice have proved most economical or available in the district or to the seam and its peculiarities. The board and wall system, with its panels and barriers, of the Northumberland and Durham districts, appears to be the most available under all circumstances ; while the " long-wall," as adopted in Lanca shire, Staffordshire, and elsewhere, seems to claim equal merits under certain circum stances. But in our bituminous coal-fields neither of these systems is in general use, and are but rarely adopted, though in all cases one or the other, with their various modifications, would add much to the economy of mining coal even when done on a limited scale.
In most of our Western mines, narrow chambers are carried forward, without sys tem, or in conformity with the natural undulations of the seam, which, even when appa rently horizontal, generally have an inclination in a given direction, or rolls with gentle undulations. The chambers are frequently very narrow ; we have often found them less than twelve feet wide : consequently, the trimming or cutting with the pick not only doubles the cost of mining the coal, but destroys a great portion of it by break ing it into small coal or dust ; while in the long-wall work a much larger amount of coal is obtained in a large merchantable condition, with at least half the work.
We are much surprised at the primitive manner in which those Western mines are worked even in comparatively old districts, though operated by practical English miners, conversant with the improved systems.
We think long-wall advancing may be used in most of our limited Western mines above water-level when timber is plentiful, or the roof-rock available for building road ways. But in all cases substantial pillars should be left along the permanent avenues : by this means nearly all the coal in the seam can be obtained at one-half the present cost.
Where the timber is scarce or the roof-rock not available for building protecting walls along the roads, the board and wall system, or a modification of it, as shown on page 432, may be profitably adopted, or the long-wall withdrawing may be used with much more economy than the present system of chambers. We think, however, the board and wall, or, as we might call it, the breast and pillar method, when laid out in bounda ries, with the pillars left large and withdrawn as soon as the breasts reach the barrier, is the best under all circumstances, either for the moderately pitching anthracite seams or the horizontal and undulating bituminous seams.
We would like to give more definite information on this important and interesting subject, in order to impress upon our miners the utility and benefits of the improve ments and to enable them to make use of them; but, except by the engineer, a subject so abstruse cannot be fully comprehended without the aid of plates and diagrams. We are sorry to add that our practical miners, managers, and mining engineers, have given the subject of economical mining little or no attention. They may have sought to mine coal as cheaply as possible by the old and wasteful systems, as they have been forced at times to do from stern necessity. But little or no improvements have been attempted in adapting better and more economical modes to the peculiarities of our coal-fields and seams.