[L. bis, double ; and lanx, a dish.] A machine used for weighing. The common balance consists of a beam supported at its middle point, having two scale-pans of equal weight hung from its extremities. The object aimed at in its construction is to secure delicacy and rapidity in weighing. Of other forms of lever, the Roman balance, or steelyard, consists of a rod suspended from a fulcrum, so that the two arms are of unequal length. The substance to be weighed is suspended from the shorter arm,and a moveable weight slides along the longer arm, which is graduated to indicate quantities. This form of balance is in use at railway stations for weighing luggage and loaded carts. The spring balance shows the weight of a body by the extent to which it stretches a spiral spring.