21st.—Well, mamma, we have been to those famous quarries, and they are indeed wonderful. But to me the most striking thing about them is, that such prodigious excavations should have been made in so short a period; for we were attended by an old man who actually remembers the first opening of the large quarry. It also seemed astonishing that they should have been the work of men who appeared so diminutive, when compared with the huge blocks of slate round which I saw them clustering and bustling like a colony of little ants round a straw.
Every thing is done here by a kind of task work. A piece of the rock is bought by a party of men, who agree to work together; they convert it into as great a number of slates as they can, and the overseer purchases them at stated prices. Their first operation is to blast off a large block: this is done by making a round hole about two or three feet deep, with a pointed iron crow; a pound of gunpowder is then poured in, and the hole is rammed full of clay or broken slate. A thick wire, which was kept in the hole while the ramming was going on, is now withdrawn, and a straw filled with fine powder is introduced into its place with a bit of match-paper fixed to the upper end. All is now ready—a man calls out with a loud voice that he is going to fire—the workmen scamper away and hide themselves in the hollows of the rock—and he then lights the slow-match, and escapes as fast as he can. I saw several of these explosions, or “shots,” as they call them, each of them cracking the rock to a great distance, and carrying up in the air a frightful shower of fragments, which, my uncle says, reminded him of the stones he saw thrown out of Mount Vesuvius, in one of the great eruptions. The masses that were cracked by the explosion are now detached with levers and wedges, and broken into pieces of a proper size, which are then split into slates, while the blasters are preparing fresh materials; so that no one is idle for a moment.
The names given to the different sizes of slates will amuse you; they are taken from all ranks of our sex; queens, duchesses, countesses and ladies; and each size has its peculiar thickness. I was very much interested by the quickness and expertness with which the splitters did their part of the business: the workman gently drives a chisel, or thin wedge, with his mallet into the edge of the block—you see the crack running slowly along—and then by a certain motion of the chisel he separates the whole surface as neatly as a carpenter splits a piece of straight deal into laths. I was surprised at seeing some of these thin leaves of slate bending considerably while the splitter was forcing them off; but my uncle says, that all stones have more or less elasticity, and that a small marble ball will rebound to a considerable height, if dropped on a hard substance. Some kinds of stone have a disposition to warp or bend permanently, as he made me recollect was the case in one of the slabs of marble in the dining-room fire-place at Fernhurst; and, he says, that the flags in many of the streets of London, are hollow on the upper surface from their having been originally too thin, and from being supported only at the edges, they have yielded in the middle.
After the slates are split, they are squared and cut to the various shapes and sizes used in roofing; this is generally done in a rough but expeditious manner with a sort of a chopper, but some of the larger and finer kinds are cut with frame-saws, so as to be precisely of the same dimensions, and to have nice smooth edges. These are called milled slates, because the saws are worked by a water-mill. Of course, we went to see this operation: a fine mountain stream turns the wheel which gives motion to more than a dozen pair of long frame-saws; each pair is set to the distance required for the length or the breadth of the slate, so that the parallel sides are cut by the same stroke; and, as the saws move forward and backward, water is kept constantly dripping into the cut, and sand is thrown in by boys. The saws, we were told, would make but slow progress without the assistance of sand—the sharp grains of which are carried forward by the jagged teeth of the saw, and are thus made to tear away the slate.
“It is on this principle,” said my uncle, “that precious stones are cut by a thin circular plate of iron, with emery, or diamond powder. And a seal engraver’s apparatus is only a sort of lathe, to which he can attach small copper-wheels that are made to revolve with great rapidity. To the plain edge of one of these wheels, he applies oil, with a little diamond powder, which soon cuts into the hardest stone; and thus by the form and size of the wheel, and the direction in which the stone is pressed against it, he can accomplish any device either in relief or intaglio. In all these cases, the particles of sand, emery, or diamond, bed themselves in the soft metal, and grind away the harder surface opposed to them; and, what will appear rather singular at first sight, when two hard substances rub against each other, it is the hardest which wears away the most. For instance, the highly tempered steel knife-edges, by which some pendulums are suspended, for experimental purposes, are less liable to wear than the still harder agate planes, on which they work: for the minute atoms of dust, conveyed by the air, adhere to the steel, and in the course of time act upon the agate.”
But to return to our mill. Solid blocks, thick enough to make about twenty slates, are thus sawed first, and afterwards split in the usual manner. Here also, we saw an immense number of little writing-slates; they are made from the finest grained part of the quarry; and their smooth surface is produced by an operation very like that of planing a board.
The great blocks are carried from the quarry to the mill, and the slates, when dressed and finished, are also conveyed to the sea-side, by little waggons on iron railways. It is wonderful what a load a horse will draw in this manner when compared with the utmost work he can do on the best common road; and yet a railway appears to be a very simple contrivance. Two parallel lines of flat iron bars are laid along the road; the horse walks between them, and thus the wheels of the waggon in rolling along the bars, neither meet with the stones and obstacles which would impede their motion on a road, nor do they sink into its hollows, and soft places. The bars are scarcely broader than the rim of the wheels, which would, therefore, slip off, but for a little raised ledge, or, as it is called a flange, along one edge of each bar. When railways are intended to carry heavy weights, both going and coming, they must be laid perfectly level: but at these quarries, as all the weight goes down to the Port for embarkation, the same horse that draws several loaded waggons hooked together down hill, can return up hill with an equal number of empty ones.
From the mill we drove to the Port of Penrhyn, which is just behind this house, and where all the slates are shipped. A prettier spot cannot be seen—the sea to the northward—the Strait of Menai—the blue hills of Wales—the town of Beaumaris, on the opposite coast of Anglesea—and the quay or pier embosomed by the surrounding high banks, with a few patches of trees on their summits. The whole harbour was full of vessels waiting their turn for loading, and the busy appearance of waggons, horses, and drivers, ships, boats, and sailors, all in motion, presented a most interesting scene.
Before I go to bed, I must add a curious coincidence that occurred this evening. My uncle had brought with him, as his travelling book, the Life of the Lord Keeper Guilford; and, after he had been explaining to me the history and the importance of rail roads, he opened his book, and I sat down to my journal. But he had scarcely begun to read, when he came to a passage describing a road, nicely levelled, and laid with long boards—to all intents a railway: and this was used for conveying coals from one of the pits at Newcastle, so long ago as the year 1670. Yet it was not, my uncle remarked, till 1767, that iron railways were invented. Mr. W. Reynolds of Coalbrook-dale first adopted them; and his example was quickly followed in all parts of Great Britain, and indeed all over the world.
One word more, dear mamma, and then I will go to bed; but my uncle has just read to us such an interesting passage from that same Lord Keeper’s life, that I really must tell it to you. The children of the family at Badminton were bred with philosophical care; no inferior servants were permitted to talk to them for fear of their imbibing some mean sentiments; and he mentions the following anecdote as a proof of their high principles. Lord Arthur, who was then little more than five years old, reproached the Chief Justice Hales with his cruelty in condemning men to be hanged. The judge told him, that if they were not hanged, they would continue to kill and steal. “No,” replied the boy, “you should make them promise upon their honour that they would not.”