SWATARA DISTRICT.
In proceeding westward, we shall briefly notice a few of the chief or dis tinguishing formations, and shall not reiterate that which we have already stated concerning the seams and their peculiarities, since there is a general sameness of the measures from Pottsville to Tremont, and the mj.mber of basins there is, perhaps, not less than between the Mine Hill and the Sharp Mountain, as figure 91 partially illustrates. Three basins are represented, looking west. The right of the view is along the line of the Mine Hill range, and the two northern basins may be considered as in it. To the south of these there are three basins, part of one only being represented which divides this portion of the field into five basins.
The first basin, counting from the south, or the Sharp Mountain, is a continuation of the Pottsville axis; and it is probable that the remaining basins are parallel axes, starting out from the same point, though subject to many changes and modifications between the points, such as the " shift ing" of the anticlinals from right to left, and vice verse, and the elevation and depression of the synclinals, as explained in the case of the first tasin, south of the Mine Hill. Beyond this point the axes divide, the north anticlinals turning northwest, the south axes pursuing their course with out much change. This deflection soon accomplishes a division of the field, and forms the north and south forks, formerly described.
The first basin south of the Mine Hill, which we partially represent in figure 91, continues into and throughout the Lykens Valley, or North Fork; and the same may be said of the second or middle basin. But at or near this point a new basin commences, which widens and undulates in minor rolls westward, until it terminates in a short point between the forks.
The south basin, as already observed, forms the South or Dauphin Fork, which is a single basin; while the north is a double basin, as intimated by a continuation of the two basins before mentioned. A third basin is, how ever, developed at Bear Gap; but where this commences we have been unable to ascertain.
The two small north basins, containing the "seven-foot" as the upper seam, terminate a short distance west of Swatara Falls. The veins are here found in their places uniformly, as shown by the letters; but we are not informed whether all the lower beds have been developed. Col.
D. Percy Brown, who furnished the data for this section, had not made any developments below the Skidmore. We are informed, however, that B exists a short distance to the east, at the Forestville mines, and there fore assume that it must exist here. A clear statement is given of the seams from D to J.
The Skidmore is here 6 feet thick, and lies about 50 feet below the Mammoth. The Mammoth itself is divided by 45 feet of slate and sand stone,—the lower bed being 6 feet thick, and the upper bed 16 feet; while its satellite, the "seven-foot," is 40 feet above the upper bed, and is about seven feet in thickness. The Holmes and Primrose, or F and G, arc in their proper positions; the Primrose being 145 yards in horizontal distance across the measures—which dip at 45°—from the lower bed of E, or the Mammoth.
The Orchards H and L, and the Diamond J, are found "in place" above G; but these appear to be the highest seams in this basin. The two
southern basins probably contain the Tracys, or K and L, at this point, as the highest beds of workable coal.
A gradual thinning process appears to take place in the seams south of Pottsville, while the Mammoth permanently divides, and forms three distinct seams. At Tamaqua, and east of that point, the seven-feet seam does not make its appearance; but a short distance west a thin seam starts off from the Mammoth and forms an independent bed, which never again unites with the Mammoth. At Mount Laffee another split of the Mammoth takes place, which widens in its westward course until, at Swatara, as we have just mentioned, they are 45 feet apart. Thus this great bed forms three separate and distinct seams as it goes west; and these undoubtedly continue through the Western bituminous coal-fields. We have reason to believe that both C and D depreciate westward, as all our sections indicate, and that they are small and insignificant seams at Broad Top, and perhaps obsolete in some of the Western fields; and we have, likewise, evidence that B divides in the same manner as E, and forms two distinct seams in its westward course,—which, we think, can be distinctly recognized in many parts of the bituminous regions. It is a very significant fact that all the lower seams in the Alleghany coal-fields exist in pairs, or double beds,— which sustains our theory that the Mammoth and all the white-ash coals, strictly speaking, of the anthracite regions lie below the Mahanoy sand stone, and the barren measures of the Western coal-fields. The Twin seams of Kentucky are on the same horizon with B here, which is always, or with rare exceptions, a twin seam.
The same comparison or analogy holds good in the Middle anthracite region, taking the Lehigh basins as the eastern starting-point, where the Mammoth is a single bed of from 25 to 35 feet in thickness; but in the Mahanoy region it throws off the "seven-feet,"—at first small, but increasing westward to a maximum of 10 feet. Westward of the Locust dividing ridge the Mammoth again divides and forms the "Twin veins," at first with only a few feet of dividing slate; but before it reaches the western termination of the Shamokin region, at Trevorton, those seams are divided by a hundred feet or more of measures, and are considered as distinct seams.
In the Wyoming region we do not recognize the Mammoth at the western extremity of the region. It does not exist. But there, as here, the seams divide, in the vicinity of Nanticoke, and form separate beds from that point westward.
In the Broad Top region, which lies almost in a direct west course from the Wyoming field,'we cannot recognize the. Mammoth, or reconcile the seams to our central formations in the anthracite regions; but there is no difficulty if we take our western divisions as a guide, and seek only for the larger seams, since the smaller ones depreciate to mere leaders or streaks, and eventually disappear entirely. But in the Broad Top field we find the representation of every seam which we find here, with the exception of the " seven-feet," which, however, entirely disappears before reaching the western end of the anthracite fields in the Middle coal-field, and does not appear in the Northern, or Wyoming, field.