In speaking of such contrivances we are constantly passing over the narrow line which separates them from what we popularly term machinery. Let us take an example of the readiness with which a small aid to manual labour gradually becomes perfected into a machine, requiring little impulse from human action. The dippers of candles have gradually, in small establishments, made several improvements in their art for the purpose of diminishing labour. They used to hold the rods between their fingers, dipping three at a time; they next connected six or eight rods together by a piece of wood at each end, having holes to receive the rods; and they now suspend the rods so arranged upon a sort of balance, rising and falling with a pulley and a weight, so as to relieve the arms of the workman almost entirely, while the work is done more quickly and with more precision. But in large candle-factories the principle is carried much further. The wicks, having been cut by machinery of the requisite length, instead of being cut one at a time, are arranged upon a rod. For the sort of candle called "twelves," or twelve to a pound, twenty-four wicks are suspended on one of these rods. Thirty rods are connected together in a frame, which thus holds seven hundred and twenty wicks. Attached to the machine are thirty-six of these frames. The whole number of wicks is therefore twenty-five thousand nine hundred and twenty. The machine, as it revolves, dips one frame into a vessel of melted tallow; and so on till the thirty-six frames have each been once dipped,--and the process is continued till the candles are fully formed. One man and a boy complete this number of candles in a working-day of ten hours. [Illustration: 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. [Illustration: Tiring a wheel.]