It must not be inferred from the fact of the anti clinals and synclinals—or, in mining-phrase, saddles and basins—increasing in number as we proceed west, that those anticlinals, &c. are continuous. We do not think any of those axes proceed half-way in the length of the main basin. As we before observed, all the anticlinals of the anthracite regions advance in echelon by the right flank, from south to north. They start from the Sharp Mountain, in the Southern coal-field, generally, and traverse the basin diagonally towards its northern margin. But few of those anticlinals, however, preserve their axis from margin to margin. They die out, or sink down, and another starts from their side to continue a parallel course. It is impos sible to locate the course of the axis of formation throughout the coal-fields with any practical exactness at present. It can only be done by a great number of cross-sections, taken at short distances, from end to end of the coalfield; and these cannot be obtained without more time and labor than can now be profit ably spent for the purpose.
It is always important that the mining engineer should establish the exact location of each axis of formation within the boundaries of every mining establishment or estate. Should we attempt to lay down the general course of the anticlinals in this work, as Prof. Rogers attempted to do, it would only be approximate, and would not be definite enough for any practical purpose. We will, however, endeavor to give such information as will materially assist the practical miner, and the engineer too, who may not be generally familiar with the region, in unravelling many of the heretofore mysterious formations of the anthracite fields. Our object is to clear away many of the doubts in regard to irregular formations, and to present a clear exposition, by illustration and text, of the intricate and singular contortions of the anthracite strata.
At Tamaqua we find more veins than properly belong to the white-ash series below the Mammoth; but we have before explained and represented in figure 70 the reason of this increase,—arising out of their repetition by sudden foldings.
We find, however, a consistency and order in the veins at Tamaqua which cannot be evoked out of the formations of the Lehigh. Here the veins fall into their places in order and uniformity with the other portions of the anthracite regions, where the conditions are normal or according to law. It is singular that the veins in the Lehigh district are so much at
variance with all other portions of the anthracite formations. But, as we said in another place, it is possible the miners are more in error than the coal-beds.
Figure 71 is a vertical section of the Tamaqua coal measures, and may be taken as a general type of the district. We think, however, that we have been led into error by the repetitions of the beds here, and have, therefore, misapplied the names or letters. We find, since our engravings were executed, it is more than probable that C is really B, and that B, as applied, should be represented by it. This may be considered as the proper condition. Such an alteration would place D up to the 3-feet vein under the Mammoth, which we have included with the Mammoth, or E, in order to compensate for the error of placing B in the position properly belonging to A, thus making two errors to rectify one. With this ex planation we hope figure 71 will be understood. We may have made other errors, but if discovered in time we will try to rectify them, as in the present case.
The Mammoth at Tamaqua is not as large as it is generally found, but we have not given its maximum dimensions. It is found in the vicinity over 50 feet thick; but we think the size given in figure 71—that is, 20 feet—about its best workable size in this district. Our data are chiefly derived from the officers of the Little Schuylkill Coal Company, and from Mr. George Brown, whose long and practical experience makes him g( )d authority on such matters.
The Holmes (F) and the Primrose (G) are in their proper sizes and places; while the red-ash veins, H, I, and J, are also in their uniform places and sizes.
The Skidmore (D) does not, however, appear in its proper place or con dition; but it is a variable vein, and we do not think it an important discrepancy, since it frequently depreciates in size.
The two following sections are on the Greenwood Coal Company's pro perty, east of Tamaqua. The data were obtained from Mr. Robert Carter, General Superintendent.
It will be observed that the above vertical section through the measures at Greenwood, between the Lehigh and Tamaqua, is perfect. The veins are in full size and in their proper places. We cannot conceive how the variation can be so great, only a few miles farther to the east, at the Summit mines.