WATER WHEELS AND WATER MILLS
1. Wheels on the principles that have been described above are also
constructed in rivers. Round their faces floatboards are fixed, which,
on being struck by the current of the river, make the wheel turn as they
move, and thus, by raising the water in the boxes and bringing it to the
top, they accomplish the necessary work through being turned by the mere
impulse of the river, without any treading on the part of workmen.
2. Water mills are turned on the same principle. Everything is the same
in them, except that a drum with teeth is fixed into one end of the
axle. It is set vertically on its edge, and turns in the same plane with
the wheel. Next to this larger drum there is a smaller one, also with
teeth, but set horizontally, and this is attached (to the millstone).
Thus the teeth of the drum which is fixed to the axle make the teeth of
the horizontal drum move, and cause the mill to turn. A hopper, hanging
over this contrivance, supplies the mill with corn, and meal is produced
by the same revolution.