Dipping-machine.
Walking by a wheelwright's shop in some quiet village, did our readers ever see the operation of "tiring" a wheel? The wood-work of the wheel is entirely formed; but the joints of the felloes are imperfectly fitted together. They used to be drawn close by separate straps of iron applied with great labour. The wheel rests upon some raised bricks. Out from the forge rush three or four men bearing a red-hot iron hoop. It is laid upon the outer rim of the wood-work, burning its way as it is hammered down with the united force of the wheelwrights. When it is nearly fitted, floods of water are thrown upon it, till it no longer burns. The knowledge of the simple fact that the iron shrinks as it cools, and thus knits the whole wheel into a firm body, taught the wheelwright how to accomplish the difficult task of giving the last strength to his wheel with the least possible labour.
Tiring a wheel.
The manufacture of a globe offers an example of the production of a most beautiful piece of work by the often repeated application of a series of processes, each requiring very little labour. A globe is not a ball of wood; but a hollow sphere of papers and plaster. The mould, if we may so express it, of a globe is turned out of a piece of wood. This sphere need not be mathematically accurate. It is for rough work, and flaws and cracks are of little consequence. This wooden ball has an axis, a piece of iron wire at each pole. And here we may remark, that, at every stage of the process, the revolution of a sphere upon its axis, under the hands of the workman, is the one great principle which renders every operation one of comparative ease and simplicity. The labour would be enormously multiplied if the same class of operations had to be performed upon a cube. The solid mould, then, of the embryo globe is placed on its axis in a wooden frame. In a very short time a boy will form a pasteboard globe upon its surface. He first covers it entirely with strips of strong paper, thoroughly wet, which are in a tub of water at his side. The slight inequalities produced by the over-lapping of the strips are immaterial. The saturated paper is not suffered to dry; but is immediately covered over with a layer of pasted paper, also cut in long narrow slips. A third layer of similarly pasted paper—brown paper and white being used alternately—is applied; and then, a fourth, a fifth, and a sixth. Here the pasting process ends for globes of moderate size. For the large ones it is carried further. This wet pasteboard ball has now to be dried—placed upon its axis in a rack. If we were determined to follow the progress of this individual ball through all its stages, we should have to wait a fortnight before it advanced another step. But in a large factory there are many scores of globes all rolling onward to perfection; and thus we may witness the next operation performed upon a pasteboard sphere that began to exist some weeks earlier, and is now hard to the core.
The wooden ball, with its solid paper covering, is placed on its axis. A sharp cutting instrument, fixed on a bench, is brought into contact with the surface of the sphere, which is made to revolve. In less time than we write the pasteboard ball is cut in half. There is no adhesion to the wooden mould, for the first coating of paper was simply wetted. Two bowls of thick card now lie before us, with a small hole in each, made by the axis of the wooden ball. But a junction is very soon effected. Within every globe there is a piece of wood—we may liken it to a round ruler—of the exact length of the inner surface of the sphere from pole to pole. A thick wire runs through this wood, and originally projected some two or three inches at each end. This stick is placed upright in a vice. The semi-globe is nailed to one end of the stick, upon which it rests, when the wire is passed through its centre. It is now reversed, and the edges of the card rapidly covered with glue. The edges of the other semi-globe are instantly brought into contact, the other end of the wire passing through its centre in the same way, and a similar nailing to the stick taking place. We have now a paper globe, with its own axis, which will be its companion for the whole term of its existence.
The paper globe is next placed on its axis in a frame, of which one side is a semicircular piece of metal;—the horizon of a globe cut in half would show its form. A tub of white composition, a compound of whiting, glue, and oil, is on the bench. The workman dips his hand into this "gruel thick and slab," and rapidly applies it to the paper sphere with tolerable evenness; but as it revolves, the semicircle of metal clears off the superfluous portions. The ball of paper is now a ball of plaster externally. Time again enters largely into the manufacture. The first coating must thoroughly dry before the next is applied, and so again till the process has been repeated four or five times. Thus, when we visit a globe-workshop, we are at first surprised at the number of white balls, from three inches in diameter to three feet, which occupy a large space. They are all steadily advancing towards completion; and as they advance to the dignity of perfect spheres, increased pains are taken in the application of the plaster. At last they are polished. Their surface is as fine and hard as ivory. But beautiful as they are, they may, like many other beautiful things, want a due equipoise. They must be perfectly balanced. They must move upon their poles with the utmost exactness. A few shot, let in here and there, correct all irregularities. And now the paper and plaster sphere is to be endued with intelligence. The sphere is marked with lines of direction for the purpose of covering it with engraved slips. We have now a globe with a plain map. An artist colours it by hand.
We have given these examples of several modes of production, in which knowledge and skill have diminished labour, for the purpose of showing that not only machinery and scientific applications are constantly tending to the same end, but that the mere practice of the mechanical arts necessarily leads to labour-saving inventions. Every one of us who thinks at all is constantly endeavouring to diminish his individual labour by the use of some little contrivance which experience has suggested. Men who carry water in buckets, in places where water is scarce, put a circular piece of wood to float on the water, which prevents its spilling, and consequently lessens the labour. A boy who makes paper bags in a grocer's shop so arranges them that he pastes the edges of twenty at a time, to diminish the labour. The porters of Amsterdam, who draw heavy goods upon a sort of sledge, every now and then throw a greased rope under the sledge, to diminish its friction, and therefore to lessen the labour of dragging it. Other porters, in the same city, have a little barrel containing water, attached to each side of the sledge, out of which the water slowly drips like the water upon a stone-cutter's saw, to diminish the friction.