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In this bounty nature was more liberal to the tight little island than to any other spot in Western Europe, and England took early advantage of it. To be sure, her coal-field is small compared with that of the United States an area of only 11,900 square miles to our 192,000.
Much is expected in future from the large coal-field of the Wardha and Chanda districts, in the Central Provinces, the coal of which may eventually prove to be of Permian age. The coal-deposits of China are undoubtedly of tremendous extent, although from want of exploration it is difficult to form any satisfactory estimate of them.
All doubt was, however, finally dispelled by the discovery by Mr Binney, of a sigillaria and a stigmaria in actual connection with each other, in the Lancashire coal-field. Stigmariae have since been found in the Cape Breton coal-field, attached to Lepidodendra, about which we have already spoken, and a similar discovery has since been made in the British coal-fields.
BRITISH. Coal-measures of South Wales, with underclays inclosing Stigmaria. FOREIGN. Coal-field of Saarbruck, with Archegosaurus. BRITISH. Mountain limestone of Wales and South of England. FOREIGN. Mountain limestone of Belgium. BRITISH. Yellow sandstone of Dura Den, with Holoptychius, etc. FOREIGN. Clymenien-kalk and Cypridinen-schiefer of Germany.
Now if we admit that the five million tons of coal from the Northumberland and Durham mines is equal to nearly one-third of the total consumption of coals in England, each square mile of the Welsh coal-field would yield coal for two years' consumption; and as there are from one thousand to twelve hundred square miles in this coal-field, it would supply England with fuel for two thousand years, after all our English coal-mines are worked out.
The same species of plants are to be met with throughout the whole thickness of a coal-field, and the youngest are not sensibly different from the oldest. But more than this. Notwithstanding that the carboniferous period is separated from us by more than the whole time represented by the secondary and tertiary formations, the great types of vegetation were as distinct then as now.
Round them, as they gradually went down with the subsiding soil, calamites grew, at one level after another. In the Sydney coal-field fifty-nine fossil forests occur in superposition. Marine shells, found on mountain-tops far in the interior of continents, were regarded by theological writers as an indisputable illustration of the Deluge.
The thirty-feet bed of coal in the Dudley coal-field is of limited extent; and in the present mode of working it, more than two-thirds of the coal is wasted and left in the mine.
Wherever a coal-field now exists, there must formerly have been free access for a great river, or for a shallow sea, bearing sediment in the shape of sand and mud. When the coal-forest area became slowly depressed, the waters must have spread over it, and have deposited their burden upon the surface of the bed of coal, in the form of layers, which are now converted into shale, or sandstone.
This great disproportion between the total thickness and the thickness of coal itself shows itself in every coal-field that has been worked, and when a single seam of coal is discovered attaining a thickness of 9 or 10 feet, it is so unusual a thing in Great Britain as to cause it to be known as the "nine" or "ten-foot seam," as the case may be.
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