82 FERGUSON'S LECTURES. 



LECT. down the shoe; and so regulates the feeding as the 

 ^J^^, miller sees convenient. 



The heavier the running millstone is, and the greater 

 the quantity of water that falls upon the wheel, so much 

 the faster will the mill bear to be fed; and consequently 

 so much the more it will grind. And on the contrary, 

 the lighter the stone, and the less the quantity of water, 

 so much slower must the feeding 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 required to turn a heavy mill- 

 stone, is but very little more than what is sufficient to 

 turn a light one : for as it is supported upon the spindle 

 by the bridge-tree S T, and the end of the spindle that 

 turns in the brass foot therein being but small, the odds 

 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. 



In order to cut and grind the corn, both the upper 

 and under millstones have channels or furrows cut into 

 them, proceeding obliquely from the center towards the 

 circumference. And these furrows are cut perpendicu- 

 larly on one side and obliquely on the other into the 

 stone, which gives each furrow a sharp edge, and in 

 the two stones they come, as it were, against one ano- 

 ther like the edges of a pair of scissars : and so cut the 

 corn, to make it grind the easier when it falls upon the 

 places between the furrows. These are cut the same 

 way in both stones when they lie upon their backs, 

 which makes them run cross ways to each other, when 

 the upper stone is inverted by turning its furrowed sur 



