TOPOGRAPHY OF THE FIELD.
The Southern coal-field is bounded and set by the same frame or cha racter of mountain-ranges as those which distinguish the other anthracite fields. The range on the south is continuous from one end of the coal-field to the other, and is known as the Sharp Mountain. It is a steep, sharp, monoclinal mountain, with a crest of coarse massive conglomerate, and a base on the south of soft red shale. The outcrops of this range are all south, and the dips to the north, underlying the first basins of the coal field. At the eastern extremity of the field the Sharp Mountain unites with the Locust Mountain, and is known as the Mauch Chunk Mountain. It terminates in an abrupt point, almost overhanging the Lehigh River, and towering over one thousand feet above it. This terminal knob or point is known as Mount Pisgah, and is crowned by the engines of the Lehigh Coal & Navigation Company, for the elevation of their coal-ears up the Mount Pisgah planes to the head of the back track, which is a gravity-line, to the mines, and which we will describe under the proper head, appro priate to our mining establishments, in the Appendix.
From the Lehigh to a point about 20 miles west, the north range is known as the Locust Mountain ; but whether this is intended as a con tinuation of the Locust Mountain of the Middle coal-field is not clear. There is no geological or topographical connection between the two; but such a nomenclature would be no more arbitrary 'than the misnomers which distinguish the topography of Mahanoy and Shamokin.
At the point named, the Locust Mountain—which, like the Sharp Moun tain, has a monoclinal axis, but with a northern outcrop and a southern dip—unites with the Broad Mountain. This mountain, as the map indi cates, is a broad, undulating plateau of conglomerate, lying between the central portions of the Southern field and the Mahanoy division of the Middle field : its maximum breadth is about six miles, and its greatest length twenty miles.
It contains several small, independent basins of coal along its which we shall describe separately, as they have no connection with the other coal-fields.
Along the southern foot of the Broad Mountain lies the Mine Hill basin, which is simply separated from the main coal-field by the sharp and narrow anticlinal ridge of the Mine Hill, which at each extremity enters the Broad Mountain, and of which it seems a part, separated only by the Mine Hill basin. This small basin lies deep in its central portions, but its extremities are elevated to the surface. Like an Indian pirogue, it is long and narrow, deep in the middle, but pointed, sharp, and elevated at the ends. There is, however, a second subordinate basin within the main one, lying on the north, which, like a second canoe, smaller, sharper, and more narrow than the first, lies alongside. This is called the Jugular synclinal, and is divided from the first by the Jugular anticlinal: at each extremity of the smaller basin this anticlinal distinctly separates the two basins, but in its centre the coal-veins overlap the saddle and connect the strata on the axis.
This northern basin is peculiarly sharp, deep, and narrow,—its strata having a uniform dip in its centre to the south. The should-be north dips are inverted, and really underlie the south dips of the main basin. This peculiarity was at first a source of much speculation and misconception by our mining engineers, since the coals of the entire basin were mistaken for underlying veins; and much time and money has been spent in vain efforts to discover them elsewhere.
The Mammoth is so doubled and brought in connection in this basin that it has been taken for one vein of enormous thickness, and called the " Jugular ;" while the four underlying veins are also repeated : so that, in appearance, there would seem to be twelve or thirteen veins underlying the Mammoth in the Mine Hill basin. Figure 64 represents the two basins at the eastern extremity of the formation, or where the Mammoth is unearthed, in the vicinity of Mill Creek Gap, above St. Clair.