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mine, we may say—renders these clay-bands and black-bands of peculiar importance. About 5,000,000 tons of pig or cast iron are annually manufactured in Britain, and of this the greater proportion is obtained from our coal-fields. Looking at the peculiar phases of modern civilisation, it is impossible to over-estimate the importance of an abundant supply of iron. Indeed, without this abundance, our varied machinery, our steam-engines, our railroads, gas and water pipes, suspension-bridges, iron ships, and other similar inventions, would have been impossible, or if possible, would have been on a limited and insignificant scale in comparison. This work and application of iron is one of the leading features of our times—its malleability, strength, durability, and cheapness fitting it for almost every purpose, from the homeliest utensil of domestic use to the most elegant and complicated machinery, and from the tiniest implement of art to the most gigantic instrument of war. Ours is in truth the Age of Iron, there being no industrial operation in which that metal does not play an important part, no enduring subjugation of the forces of nature unless through its instrumentality and power.

Besides coal and iron, Limestone also takes rank as one of the abundant and valuable products of our coal-fields. Associated with coal and ironstone, it becomes of especial value as a flux for the reduction of the latter in the blastfurnace, and all the more valuable that it is obtained from the same formation, and generally in convenient proximity. It is also extensively used for mortar and cements, in agriculture, in tanning, bleaching, and other industrial processes, and not unfrequently some varieties are hard enough and beautiful enough in texture to be raised and polished as marbles. Taken together, there are no mineral substances so valuable as coal, ironstone, and limestone; and it seems something more than a mere coincidence that in the Coalformation they should have been associated in such close proximity and accessible abundance. Had there been no other rocks in the carboniferous series save these three, the gifts of our coal-fields would have been incalculable; how much more their value when other products, all useful and abundant, can be raised from the same system, from the same shaft, and in course of the same mining operations!

Sandstones of great beauty and durability, like those of Edinburgh, St Andrews, Stirling, Glasgow, Newcastle, Leeds, and other localities, are obtained in inexhaustible supplies from the Coal-formation; and when the importance of substantial and elegant edifices is duly considered, these building-stones must be ranked among the more valuable of its products. Taking Edinburgh, Glasgow, and Newcastle as examples, the fitness, beauty, and durability of the coal-measure sandstones for architectural purposes must stand unquestioned; and, considering the readiness with which they can now be carried by railway to all parts of the island, the rapid extension of their employment may be safely predicted.* Nor is it merely for building purposes that these sandstones are used, but many of their varieties, as their names imply (millstone grit, grindstone grit, &c), are extensively raised for millstones, grindstones, whetstones, and other kindred purposes. In a rigorous and irregular climate like that of Britain, the possession of a durable building-stone is of prime importance, alike on the ground of comfort and economy; and luckily the Coalformation in one or other of its series affords a cheap and inexhaustible supply. It was the boast of Nero that he found Eome built of bricks, but had left her of marble: had her seven hills contained such sandstones as

* Since this was written in 1866, the beautiful cream-coloured sandstones of Stirlingshire have been carried to London for frontage and ornamental purposes.

those in the neighbourhood of Edinburgh, Glasgow, and Stirling, the boast might have taken a different direction. Our own Houses of Parliament, whose decay so soon after their erection has excited so much comment, are built of magnesian limestone; had the sandstones of Stirling, Fife, or Mid-Lothian been adopted, as was at one time proposed, the chisel-marks of the builder would have remained unobliterated for centuries.

Next to the sandstones or freestones of the Coal-measures we may place the Fire-clays, or those argillaceous beds which, from the peculiarity of their composition, may be baked into fabrics of any shape, and of unsurpassed resistance to the effects of either fire or water. These clays, at one time little sought after, have now become of vast importance, and are largely used as substitutes for stone and iron. Plastic, capable of being fashioned into any form, and not liable to warp in the baking-kiln, they are extensively used for fire-grates, furnace-linings, retorts, sewage-pipes, floorings, architectural mouldings, garden ornaments, and a thousand other purposes—affording objects of beauty as well as of utility, and, when properly manufactured, of unconquerable durability. Few manufactures have come of late years so largely into use as fire-clay fabrics; and, considering their recent introduction, we may confidently look forward, not only to their rapid extension, but to a skill in manipulation which will rival the finest productions of the potter and sculptor. But, altogether apart from works of art, the use of fire-clay fabrics in furnaces, and above all in the cheap and efficient drainage of our towns, has been a boon of no common value, as tending at once to the health, the comfort, and amenity of our denselycongregated populations. There is no sewer so cheaply laid, so compact, so thoroughly vermin-tight, or so easily flushed, as one composed of well-glazed and carefully-luted fire-clay pipes. Of course, as the manufacture of fireclays is intimately dependent on a cheap supply of fuel, the relation of coal and fire-clay in the same field, and often in the same mine, is a thing that must strike the attention of the least reflecting.

Even the most worthless-looking beds in the formation — the Shales, or consolidated muds — are now rapidly rising in economic importance. Those yielding alum and copperas (the alum and pyritous shales of the miner) have long been worked, though on a small scale; but now the bituminous shales, or those yielding paraffin and paraffin oil, are eagerly sought after and worked on a gigantic and rapidly-extending scale. Fields in the lower Coal-measures of Scotland, which a dozen years ago did not bring a farthing to their proprietors, are now yielding thousands; and the distillation of these shales may already be regarded as an established branch of our national industry. Nor is it merely as sources of a new and brilliant light that these shales acquire their importance. Eecent experiments have proved the adaptability of their crude oils as a fuel for steam-raising, and the hope is now held out that even the inferior varieties may be turned to good account in lessening the pressure upon our more precious coal-seams. Indeed, when we consider the worthless aspect of these shales, and the beauty and utility of the substances—solid paraffin, paraffin oil, naphtha, rosine and magenta dyes—derived from them, few instances of human ingenuity to utilise the products of nature could be adduced at once so marvellous and so thoroughly successful. What so unlike as a block of black bituminous mudstone and a paraffin candle, white and translucent as the finest wax] What so seemingly impossible as the extraction of a brilliant rose-purple dye from a mass of pitch-coloured coal-tar?

Besides these rocks—the coals, ironstones, limestones, sandstones, fire-clays, and shales—of which the Carboniferous system is entirely composed, there occur in some localities independent veins of lead-ores and zinc-ores traversing the beds of the mountain limestone. These veins (like those of Derbyshire, Yorkshire, and Northumberland) are often of great commercial value, not only for the lead and zinc they directly supply, but for the percentage of silver which many of them yield—the lead-ores being generally less or more argentiferous.

Such are the products we derive from the Coal-formation, and such the benefits they have conferred and are still conferring on our country. Statisticians may set down their amounts in weights and measures, and their values in money, but no method of computation can fully convey an idea of the advantages, physical, intellectual, and moral, we enjoy in possessing such productive and accessible coalfields. Had the coals been in one field, the ironstones in a second, and the limestones and fire-clays in a third, they would still have been prized and sought after; but when the whole are found in the same field, and often in the same mine, their value is a hundred-fold enhanced, and their importance becomes more distinctly appreciable. Nor can it be overlooked that, situated as most of these coal-fields are, in the lower districts of our island, they are peculiarly accessible by water and readily reticulated by railways— the Bristol Channel, the Mersey, the Tees, Wear, Tyne, Forth, and Clyde all opening their ports for convenient transport to other and less favoured localities. Nor is it to Britain alone that the advantages of her coal-fields extend — the whole world, through her machinery and manufactures, participates in the boon, and the impetus thereby given to human progress will descend to future ages. Her steam-engines, manufacturing machinery, railroads, water

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