wick, Nova Scotia and Newfoundland, which, as before stated, are but continuations of our own great region, and which contain a net area of some eighteen thousand square miles-that of Pennsylvania being not quite sixteen thousand square miles, or one-third of its entire physical area. The coal strata in the British provinces are not as productive as our own— -the seams are "faulty," and the coal full of earthly impurities. Large as this body of coal appears, some other States, (with a larger territory, however,) have a still greater amount; or, rather, a greater amount of coal area—for in regard to quality, Pennsylvania, from the inclined dip of her anthracite coal veins, still has more coal than those States where the veins lie in a horizontal position, no matter what their area of coal land. The following table exhibits the quality of coal land of each State where it is found: Reduced to acres, we have, in the twelve States above mentioned alone, something like three hundred and sixty-one millions, eight hundred and eighty-one thousand one hundred and fifty-one acres of coal land! Of this Pennsylvania has over twenty-eight millions two hundred thousand acres, embracing (which the other States do not,) anthracite, bituminous, and semi-bituminous coal. The greatest length of the Alleghany coal-field is seven hundred and fifty-six miles; its greatest breadth one hundred and seventy-three, and its average breadth about eighty-five miles. There are some thirty or forty points where coal is regularly mined, the average thickness of the veins worked being about ten feet-some of them being twentytwo, while those along the Conemaugh and the Portage Railroad, near us, are from ten to fifteen feet thick At Frostburg there is a vein twentysix feet in thickness. The annual amount of coal shipped to the eastward, by way of the Juniata and the north branch of the Susquehanna, will not exceed sixty thousand tons. Of course the greatest amount raised is consumed in and around Pittsburg, and sent down the Ohio River, the actual amount of which in tons we can make no estimate, there being no record or statistics by which it can be ascertained satisfactorily. The annual consumption, at a single estimate, (taking in view all the outlets, including that to Lake Erie,) we should compute at one million tons -most probably more; certainly not less. The anthracite coal region we have discussed at sufficient length in Off-hand Sketches, Part II., another part of this work, to which we beg leave to refer our readers. Our remarks upon that region are illustrated with cuts, nearly all of which would be applicable to this region, there being little difference between the two districts except in the process of mining, and a material dissimilarity in the structure and position of the strata. . STRUCTURE AND ORIGIN OF THE ALLEGHANIES.-The within geological section (extending from near the Atlantic some four hundred Old Red Sandstone. 7 Old Red Sandstone. 6 Old Red or Devonian, Olive Slate, &c. or Silurian strata. C Silurian. 5 Anthracite and Bituminous Coal. B to C.-Atlantic Slope. A to B.-Atlantic Plain. 16 Gneiss. B. 3 Cretaceous. 2 miles westward) exhibits the general order of structure, and relative elevation of the wonderful region we are traversing. Starting in the east, we first cross a low plain, extending to the letter A, which was called the alluvial plain by the first geographers. A portion of this plain has been omitted in the engraving, for the want of room. It is occupied by tertiary and cretaceous strata nearly horizontal, and in general contains no hard and solid rocks, and is usually not more than from fifty to one hundred feet high, at any point along the coast, from New Jersey to Virginia. In these States this zone is not many leagues in breadth, but it acquires a breadth of one hundred and one hundred and fifty miles in the southern States, and a height of several hundred feet towards its western limits. This is called the Atlantic plain. The next belt, running from B to C, consists of granite rocks, chiefly gneiss and mica-schist, covered occasionally with unconformable red sandstone (marked figure 4). It is from twenty-five to thirty miles in width, and traversed by the Conewago Hills, or South Mountain range. This is called the Atlantic slope, because it brings us to the first mountain range belonging to the Alleghany series, the Kittatinny; and contains itself numerous elevations, cut up by streams and otherwise much worn away, ranging in height from one to three hundred feet. On either side of this sandstone district are extensive layers of limestone, which we have elsewhere spoken of at length. From C to D we have all the mountain elevation constituting the great Alleghanies. Leaving the new red sandstone formation, (which is distinguished from the older formation by its occupying a horizontal position, or rather by its not laying in regular order with the older strata) we cross a narrow projecting belt of the primary fossiliferous group, constituting what is called the Silurian system of rocks. This group of strata, it will be seen, occupies the most elevated position of the mountain region. The next formation above it is that of the old red sandstone, which, it will be seen, forms the bed of the coal throughout the whole extent of country, whenever it appears, extending westward from D some five hundred miles, with the exception of the district previously referred to, separating the Alleghany from the Illinois coal-field, and where the Silurian Rocks again rise to the surface. But from D westward the coal invariably lies in a horizontal or flat position, with a few local exceptions, where it has been raised to a slight elevation, not exceeding one hundred feet in any case. A few days' observation of the identity of the fossil plants, and the relative position of the anthracite, satisfied me that it was of the same age as the bituminous coal which I had seen at Blossberg. This opinion was, I believe, first promulgated by Mr. Featherstonehaugh, in 1831, at a time when many geologists were disposed to assign a higher antiquity to the anthracite than to the bituminous coal measures of the United States. The recent surveys have now established this fact beyond all question, and hence it becomes a subject of great interest to inquire how these two kinds of coal, originating, as they did, from precisely the same species of plants, and formed at the same period, should have become so very different in their chemical composition. In the first place, I may mention that the anthracite coal measures, occurring in the eastern or most disturbed part of the Alleghany chain, are fragments or outlayers of the great continuous coalfield of Pennsylvania, Virginia, and Ohio, which occurs about forty miles to the westward. This coal-field is remarkable for its area, for it is described as extending continuously from north-east to southwest for a distance of seven hundred and fifty miles, its greatest width being about one hundred and eighty miles-extending from the northern border of Pennsylvania as far south as near Huntsville, in Alabama. It must have measured originally, before reduced by denudation, at least nine hundred miles in length, and in some places more than two hundred miles in breadth. By reference to the section it will be seen that the strata of coal are horizontal to the westward of the mountain region, and become more and more inclined and folded as we proceed eastward, from D to C. Now it is invariably found that the coal is most bituminous towards its western limit, where it remains level and unbroken, and that it becomes progressively debituminized as we travel south-eastward towards the more bent and distorted rocks. Thus, on the Ohio, the proportion of hydrogen, oxygen, and other volatile matters, ranges from forty to fifty per cent. Eastward of this line, on the Monongahela, it still approaches forty per cent., where the strata begin to experience some gentle flexures. On entering the Alleghany Mountains, where the distinct anticlinal axes begin to show themselves, but before the dislocations are considerable, the volatile matter is generally in the proportion of eighteen or twenty per cent. At length, when we arrive beyond i, associated with the boldest flexures of the Appalachian chain, where the strata have been actually turned over, as near Pottsville, we find the coal te contain only from six to twelve per cent. of bitumen, thus becoming a genuine anthracite.-Trans. of Ass. of Amer. Geol., p. 470. It appears from the researches of Liebig and other eminent chemists, that when wood and vegetable matter are buried in the earth, exposed to moisture, and partially or entirely excluded from the air, they decompose slowly and evolve carbonic acid gas, thus parting with a portion of their original oxygen. By this means they become gradually converted into lignite or wood-coal, which contains a larger proportion of hydrogen than wood does. A continuance of decomposition changes this lignite into common or bituminous coal, chiefly by the discharge of carburetted hydrogen, or the gas by which we illumine our streets and houses. According to Bischoff, the inflammable gases which are always escaping from mineral coal, and are so often the cause of fatal accidents in mines, always contain carbonic acid, carburetted hydrogen, nitrogen, and olifiant gas. The disengagement of all these gradually transforms ordinary or bituminous coal into anthracite, to which the various names of splint coal, glance coal, calm, and many others have been given. We have thus seen that, in the Alleghany coal-field, there is an intimate connection between the extent to which the coal has parted with its gaseous contents, and the amount of disturbance which the strata have undergone. The coincidence of these phenomena may be attributed partly to the greater facility afforded for the escape of volatile matter, where the fracturing of the rocks had produced an infinite number of cracks and crevices, and also to the heat of the gases and water penetrating these cracks, when the great movements took place, which have rent and folded the mountain strata. It is well known that, at the present period, thermal waters and hot vapors burst out from the earth during earthquakes, and these would not fail to promote the disengagement of volatile matter from the carboniferous rocks. To the elaborate and faithful surveys of Prof. Rogers, and the late R. C. Taylor, we owe the discovery of the clue to the general law of structure prevailing throughout this important range of mountains; which, however simple it may appear when once made out and clearly explained, might long have been overlooked, amidst so great a mass of complicated details. It appears that the bending and fracture of the beds is greatest on the south-eastern or Atlantic side of the chain, and the strata become less and less disturbed as we go westward, |