in its infancy, when the full value of this inexhaustible supply of cheap fuel can be appreciated; but the resources which it will one day afford to a region capable, by its agricultural produce alone, of supporting a large population, are truly magnificent. In order to estimate the natural advantages of such a region, we must reflect how three great navigable rivers, such as the Monongahela, Alleghany, and Ohio, intersect it, and lay open on their banks the level seams of coal. I found at Brownsville a bed ten feet thick of good bituminous coal, commonly called the Pittsburg seam, breaking out in the river cliffs near the water's edge. I made a hasty sketch of its appearance from the bridge, looking down the river, in which the reader will see (a, Pl. VI.) the coal, ten feet thick, covered by carbonaceous shale (b), and this again by micaceous sandstone (c). Horizontal galleries may be driven everywhere at very slight expense, and so worked as to drain themselves, while the cars, laden with coal and attached to each other, glide down, as shown in the plate, on a railway, so as to deliver their burden into barges moored to the river's bank. The same seam is seen at a distance, on the right bank (at a), and may be followed the whole way to Pittsburg, fifty miles distant. As it is nearly horizontal, while the river descends it C 2 crops out at a continually increasing, but never at an inconvenient, height above the Monongahela. Below the great bed of coal at Brownsville is a fireclay eighteen inches thick, and, below this, several beds of limestone, below which again are other coal seams. I have also shown in my sketch another layer of workable coal (at d, d), which breaks out on the slope of the hills at a greater height. Almost every proprietor can open a coal-pit on his own land, and, the stratification being very regular, they may calculate with precision the depth at which the coal may be won. So great are the facilities of procuring this excellent fuel, that already it is found profitable to convey it in flat-bottomed boats for the use of steamships at New Orleans, 1100 miles distant, in spite of the dense forests bordering the intermediate riverplains, where timber may be obtained at the cost of felling it. But no idea can be formed of the importance of these American coal-seams, until we reflect on the prodigious area over which they are continuous. The boundaries of the Pittsburg seam have been determined with considerable accuracy by the Professors Rogers in Pennsylvania, Virginia, and Ohio, and they have found the elliptical area which it occupies to be 225 miles in its longest diameter, while its maximum breadth is about one hundred miles, its superficial extent being about fourteen thousand square miles.* In the acompanying map (Pl. II.), the reader will see a sketch of the outline of what has been called the Appalachian coal-field, the vast area of which was before alluded to at p. 88. Vol. I., as extending for a distance of 720 miles from N. E. to S. W., its greatest width being about 180 miles. This outline must be regarded as giving a mere approximation to its true limits, but when the State Surveys of Pennsylvania and Virginia are published, the extent of this great coal-field will be most accurately delineated. While alluding to the vast area of these carboniferous formations in the United States, so rich in productive coal, I may call attention to the Illinois coal-field, the area of which has been also laid down on the map (Pl. II.), reduced from a large map of the Western States executed by Mr. Dale Owen of Indiana, and of which he has liberally given me the free use for the present publication. That coal-field, comprehending parts of Illinois, Indiana, and Kentucky, is not much inferior in dimensions to the whole of England, and consists of horizontal strata, with numerous rich seams of bituminous coal. Its position relatively to * Trans. of Amer. Geol. 1840, p. 446. |