The ancient Asiatic hand-mill consists of two flat round stones, about twenty inches or two feet in diameter, kept rolling one on the other by means of a stick, which does the office of a handle. The corn falls down on the undermost stone, through a hole in the middle of the uppermost, which by its circular motion spreads it on the undermost, where it is bruised and reduced to flour; this flour, working out at the rim of the millstones, lights on a board set on purpose to receive it. The bread made of it is said to be better tasted than that made by either wind or water mills: these hand-mills cost only a few shillings of English money. This description of mill is frequently alluded to in the Scriptures, and it was the practice for the women to grind corn every morning by means of hand-mills; and in the East, or at least in many parts of it, it continues to be the practice to this day. Water wheels, as far as the figure and construction are concerned, may be reduced to three kinds, and they are usually known by the names—overshot wheel, balance wheel, breast wheel, and undershot wheel. [Illustration: Mill.] In an overshot wheel, the water is conducted over the top of the wheel, and acts first by its momentum or mere movement, or motion, and then by its weight—the weight being its principal power in impelling the wheel round, the mere movement or motion of the water producing in this case little effect. The water is received into buckets placed all around the circle of the wheel. It first strikes the wheel at the top, and filling the first bucket, by its momentum or moving power, and more particularly by its weight, it sets the wheel in motion, and consequently makes that side heavier; and as fresh buckets rise to receive the water, while those below have emptied themselves, a constant tendency to motion is created, and rotation is produced. In a balance wheel, the water strikes the wheel not at the top, but always more or less above its centre, or axle. This wheel differs in no respect from the overshot wheel in its construction. It is employed where there is not a sufficient fall for an overshot wheel, which requires less water in consequence of its commanding a much greater leverage. In an undershot wheel the water acts only by its momentum, or moving power. The circumference of the wheel, instead of being supplied with buckets, as in the overshot, and breast or balance wheels, is furnished with floats, or float boards, as they are called, and, being exposed to the action of a running stream, generally, if not always, increased in rapidity by making an artificial fall, is thus driven round, and in flour-mills its force is communicated by cog-wheels to the stones employed in reducing corn to meal.