THE PLANE. 235 



teeth, have induced many persons to place it among that group. 

 These teeth, however, like those of the Hippopotamus, are 

 bevelled off at their tips, and, as they perform a similar office, 

 they take a similar curve. 



It is worthy of notice that in the Stone Adze the bevelled 

 edge much more resembles the rodent tooth than does the 

 Steel Adze, the reason being evidently that stone is more 

 fragile than steel, and requires greater thickness. Still, the 

 principle is the same in both, only the metal is more attenuated 

 than the stone. 



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 per- 

 petually 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 can- 

 not 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 



