THE LOWER COAL-BEDS.
The existence of workable beds beneath the Mammoth and Skidmore has been denied by some of our promi nent engineers, and but little is known concerning them by the miners of Schuylkill. It is unsafe, however, to conclude on general formations from local causes and evidences. Those simply familiar with the formations east of the Mine Hill might readily come to such a conclusion ; but a general knowledge of the anthracite measures must convince any practical man, despite his prejudices to the contrary. But though the seams do not assume their best condition in the Schuylkill dis trict, they are still uniformly in place, as our section, figure 76, satisfactorily proves; while our sections of each seam prove conclusively their existence in the Schuylkill district, and figure 71 shows a similar formation at Tamaqua. There is a general and constantly varying difference in the thickness of both the coal-seams and the intervening strata ; and, in order to show parallel formations, we have given the thickness respectively in figures, rather than form the sections to a uniform scale.
For instance, the section at Scranton, figure 25, containing all the seams below J, is only 455 feet in vertical height ; while the column at Pottsville below J, or the Diamond, is over 1000 feet ; but we have made them about the same dimensions, in order to justify the beds, or bring the Mammoth as a base-line on the same horizon, and we thus offer to the mind and the eye both the identity and the relative distances and dimensions.
The figures we have given are not generally the results of actual measure ments : whenever available, we have given the exact distances, but more fre quently they are approximate measurements, yet near enough to the truth for all practical purposes.
We give a parallel representation of the columns from each of the princi pal coal-regions, in order to exhibit the general uniformity and order in which the workable or prominent seams are stratified, and to prove more conclusively this identity. It brings before the eye, in a comprehensive
manner, the formation or measures of each district, and the order in which the beds are stratified.
The twelve foregoing sections exhibit more uniformity and order in the anthracite formations of Pennsylvania than we had anticipated in the com mencement of this work: we were not prepared to find so much consistency or so complete an identity in the respective seams, though we have been practically familiar with the anthracite coal measures for thirty years; and we presuthe our practical readers will be surprised to find so much order and conformity, when local formations present so many changes and fre quently so much confusion.
We have not, however, formed the sections at faulty or disturbed localities, but haVe invariably sought our data at points where the measures were regular and consistent.
Sections might be formed from actual developments at the Lehigh terminus of the first coal-field, at Coalcastle in the Mine Hill basin, at Mahanoy City, at Shenandoah City, at Pittston, and many other places, which could not be recognized as belonging to the same coal measures. But these are irregular formations, and cannot be taken as types even of the district in which they exist. Figure 115 is a vertical section of the Sullivan county (Pennsylvania) semi-bituminous basin, which represents a point between the anthracite and bituminous fields. It is the most eastern of the Alleghany formations, and, in a manner, connects the two. The Broad Top coal does not belong to the Alleghany field, and is more in connection with the anthracite than the bituminous fields, as far as geological affinities affect them.