Figure 68 represents a perpendicular view of the stratification of the Mammoth, in the celebrated Open Quarry at the old Lehigh Summit mines. It ranged from 50 to 70 feet in thickness, and was covered with from 6 to 20 feet of earth and slates. But the thick ness of the covering increased rapidly from the crest of the anticlinals or saddle to the synclinals or basin; and it was found more economical, eventually, to ex cavate the coal by the ordinary processes of mining, than by the old or original mode of quarrying.
The Summit basin is now worked by slopes. Slope No. 2, in " Spur Basin," on the Summit, dips south at an angle of 16°, and is 1290 feet long. Slope No. 4, east of Summit Hill, dips north at an angle of 69°, and is 406 feet long. These are the only mines now worked in the Summit basin. Slope No. 1 is abandoned, the coal being on fire.
Slope No. 3 is in the Panther Creek Valley, and starts within tunnel No. 6, on the Big vein. It is on the south dip, at an angle of 44°, and is 306 feet long.
Slope No. 5 is in tunnel No. 8. Its length is 300 feet on the south dip, at an angle of 44°. In addition to those four slopes, there are two tunnels in operation, and a fifth slope, in the vicinity of Tamaqua, independent of the Nesquehoning mines, and the "old tunnel" mines near Mauch Chunk, The following notes will convey some idea of the irregularity of the veins. They are taken from parallel tunnels less than a mile apart. Some
ten or twelve extensive tunnels have been driven by the Lehigh Company to develop their property. The veins traverse the valley parallel to its course from east to west, outcropping high up the mountain-sides, and covered by a considerable thickness of overlying strata in their dips to the centre of the basin or valley ; while the conformation or slopes of the mountain-sides are much less than the angle of the coal : consequently, the coal can only be reached, practically, by long tunnels.
These four tunnels are in the vicinity of Summit Hill, and are nearly opposite each other. That is, Nos. 5 and 2 are on the south side of Panther Creek, running south to cut the main north dips of the coal; and Nos. 6 and 7 are on the north side of Panther Creek Valley, running north to cut the main south dips of the coal. It will be noticed, by any one conversant with such matters, that no uniformity exists : in fact, there is a confusion which prevents the formation of any systematized sections that would identify the seams.
Figure 67 represents the general type of the coal formation in the vicinity of the old Lehigh mines. There are some points where the angle of the strata is more abrupt and on greater elevations than our section displays; but generally it conveys a just impression of the formations.