THE CUMBERLAND REGION.
The Cumberland coal-region in Maryland belongs properly to the Great Alleghany coal-field, though separated from the great body of that field by the high axis of the Negro Mountain, as shown by the accompanying map and sections. Most of the coal-mines in Maryland are in the Frost burg basin, denoted by the town of that name on the map.
The Cumberland coal-region, or that portion of the Alleghany coal-field known as the Frostburg basin, is about 5 miles wide by 30 miles long, or covers an area of 150 square miles: some accounts make it 180 square miles. That portion of the Maryland coal lying between the Savage Mountains and Negro Mountain, and extending across the State in a narrow trough, as represented by figure 120, contains about 130 square miles; and the trough or basin on the Youghiogheny, between Negro Mountain and Laurel Hill, or Briary Mountain, contains 250 square miles; making the total area of the Alleghany coal-field in Maryland about 550 square miles.
The erosion or denudation of the coal-strata in the Frostburg basin has been excessive. Of the 100,000 acres of coal-area in this basin only 20,000 are now estimated as containing the Big vein, or the upper large workable seam, and only 80,000 acres containing the lower workable bed, as the sections farther on will show.
The accompanying transverse section, figure 120, from Taylor's statistics, illustrates the connection of the Maryland with the Pennsylvania coal, as shown in figure 119. But that section did not embrace the Frostburg basin, as this (figure 120) does.
The Frostburg basin extends on the northeast into Pennsylvania, and on the southwest into Virginia. The distance through Maryland is about 20 miles. It is convex-shaped, or an oblong basin, rising slowly to the north and south, along the strike of the seams, from a common centre near the mouth of George's Creek, or its confluence with the Potomac, and more rapidly east and west, or to the outcrops of the seams, on the face of the Dan and Great Savage Mountains.
The rise of George's Creek from its mouth, near Piedmont, to its source, near Frostburg, is 1100 feet. But the rise of the seams which strike in the same direction is not proportionate to the rise of the streams. It will be noticed in figure 122 that the position of the Big vein is nearly 1000 feet above Piedmont, and yet considerably lower than the town of Frost burg. The longitudinal rise is, therefore, almost imperceptible, yet sufficient to affect the drainage of the mines or seams in the direction of the natural water-courses of the country. This is a fortunate coincidence, but one that is peculiar to all narrow basins in the Alleghany coal-field, with but few exceptions, and is in evidence that such basins have not been disturbed by an elevating or contracting process since their original formation, but that they were formed in basins having much the same form as the coal-basins now filling them. Sedimentary deposits in basins of moderate angles are
uniform, and, consequently, the deeper portions of the basins successively preserve their basin-shape, as strata after strata are deposited therein. The drainage, therefore, naturally tends to the deepest points, and seek their outlets by the lowest or nearest gaps in the bounding mountains ; or the accumulated waters burst their way towards the ocean through the soft mud barriers soon after the waters of the ancient inland sea found vent by the depression of its granite rim.
In figures 121 and 122 will be found a representation of the topography and erosion of the Frostburg basin. There are some who are disposed to grumble at the dispensations of Providence, and who would prefer to have a larger slri.re of the " Big vein" than nature has allotted them ; but such ungrateful creatures would not be satisfied even if this great bed lay un broken from Virginia to Pennsylvania. We may consider every gorge or deep ravine that has been cut through the coal measures of the Alleghany coal-field as adits or levels to drain the coal-basins. Every stream, like George's Creek, which develops a rich basin saves more millions in shafts, machinery, and constant expenses of operation than we could now estimate. Were the Frostburg basin in the condition of the Newcastle coal-field in England,—as it would be were it not for the deep erosion of the streams,— it would be almost inaccessible, under present circumstances. We think the frequent and deep erosions of our great coal-fields a fortunate occurrence, and one which will eventually exert a great economy in the development of the mineral wealth of our country.
These sections represent pretty fairly the entire Cumberland region, and show the seams in their relative position. The position of the seams, how ever, would be more correctly located in a vertical section, which we will endeavor to give if we can obtain reliable data in time. But figures 121 and 122 offer conclusive proof of the geological horizon of the Big vein, and its identity with our Mammoth bed in the anthracite regions. We have not yet been able to get the exact distances from the conglomerate to the great sandrock over the Mammoth, or the distances between the seams ; but the position and order of the seams correspond precisely with the sections we have given in the anthracite regions. A is a small seam, and not con sidered workable ; B is a seam of fair dimensions, averaging from 5 to 6 feet, and corresponds with the Buck Mountain ; C is a small, unworkable seam, and occupies the place and partakes of the character of Gamma ; D is a fair seam, corresponding to the Skidmore in the anthracite regions ; and E is the "Big vein," and identical with the Mammoth.