Balance, one of the six simple powers in mechanics, principally used for determining the equality or difference of weights in such bodies as are liable to this computation.

There are two kinds of weights principally used at present; the ancient, or the Roman steel-yard, and the modern, which consists of a lever or beam suspended exactly in the middle, having scaies or basons attached to each extremity. If the arms of the balance be of equal length, and similar weights placed in the scale, the balance will consequently be in equiliirio. But if one of the arms be in length to the other as ten to nine, the balance may still be so constructed, that both the arms with their scales shall equiponderate. This vile contrivance, however, jusly deserves to be branded with infamy; because a weight of nine pounds put into the longer arm, will counterpoise another of ten pounds placed in the shorter one; but the fraud may be instantly discovered, by shifting the weight from the one scale to the other, in which case the balance will lose its equipoise.