OF MILLS. 71 



quantity of water, so much slower must the feed- 

 ing be. But when the stone is considerably worn, 

 and become light, the mill must be fed slowly at 

 any rate ; otherwise the stone will be too much 

 borne up by the corn under it, which will make 

 the meal coarse. 



The quantity of power sufficient to turn a heavy 

 mill-stone is but very little more than what is ne- 

 cessary to turn a Hght one ; for, as it is supported 

 upon the spindle by the bridge-tree, and the end 

 of the spindle that turns in the brass foot therein 

 being but small, the difference arising from the 

 weight is but very inconsiderable in its action 

 against the power or force of the water. And, 

 besides, a heavy stone has the same advantage as a 

 heavy fly : namely, that it regulates the motion 

 much better than a light one. 



The centrifugal force carrying the corn towards 

 the circumference, it is natural that it should be 

 crushed when it comes to a place where the in- 

 terval between the two mill-stones is less than its 

 thickness ; yet the upper mill-stone being sup- 

 ported on a point which it can never quit, it does 

 not so clearly appear why it should produce a 

 greater effect when it is heavy than when it is 

 light ; since, if it were equally distant from the 

 nether mill-stone, it couid only be capable of a 

 limited impression. But as experience proves that 

 this is really the case, it is necessary to discover 

 the cause. The spindle of the mill-stone being 

 supported by a horizontal piece of timber, about 

 nine or ten feet long, resting only on both its ends, 

 by the elasticity of this piece, the upper mill-stone 

 is allowed a vertical motion, playing up and down ; 

 by which movement, the heavier the stones are 



F 4 



