The Rodent or Hippopotamus tooth has still a great advantage over any chisel or adze made by man, whether of stone or metal. As our tools are blunted, we are forced to spend much time in sharpening them, and by degrees grind the tool away until it becomes useless. Now, the teeth are so arranged that their perpetual use, instead of blunting, only sharpens them, and in proportion as they are worn away in front they are supplied with fresh matter from behind, and perpetually pushed forwards, so that they are self-renewing as well as self-sharpening. THE PLANE AND SPOKESHAVE. I have already made mention of the Plane in connection with the Chisel, and shown that, like that tool, it is formed on the same principle as the Rodent tooth. The use of this important instrument in carpentering cannot be overrated, as is shown by the numberless varieties which are used by carpenters, and the different uses to which they are put, sometimes merely smoothing a level surface, and sometimes forming a “moulding” where ornament is required. In principle, a Plane is a cutting edge or chisel, pushed along the object to be worked, and, the edge being guarded, taking off a very thin shaving from the surface. On the right hand of the accompanying illustration is shown the Plane in action, with the thin shavings falling from it in curled masses. Perhaps some of my readers may have visited some of the great iron-works, and been struck with the use of the Plane as applied to metal instead of wood, long iron shavings being taken off as easily as if they were deal, and curling in just the same manner. * * * * * THERE is an instrument very familiar to carpenters, called the Spokeshave, on account of its use in trimming the spokes of wheels. Different as it may be in appearance, it is identical in principle with the plane, having an edge guarded by a piece of wood, so that the blade cannot cut too deeply into the object on which it is employed. The chief distinction, indeed, is, that the workman, instead of pushing the blade from him, draws it to him. [Illustration: HOOP-SHAVER BEE.] [Illustration: PLANE. SPOKESHAVE.] When shaving was more in fashion than it is in these more sensible days, there were many inventions to lessen the trouble, not to say the perils, of shaving. To use the razor in a hurry was anything but an agreeable occupation, especially if the weather were frosty, and the fingers so chilled that they hardly knew whether or not they had the razor between them.