Steel-Yard, or Stilyard, is one of the most ancient machines for ascertaining the weight of bodies, by its counterpoise. It is alluded to in the Pentateuch, and to this day used by the Arabs, and all the Asiatic nations. The Greek and Roman goldsmiths preferred it to the balance, which was the instrument used by the people.
The steel-yard consists of a lever of unequal arms ; and, in its most perfect form, is constructed on the principles of the usual balance; to which however it is greatly inferior, in point of minute accuracy. On the other hand, the steel-yard is more compendious and convenient ; nor does it admit of those subtle frauds which may be, and often are, practised with a pair of scales. - See Balance.
There is another species of patent steel-yard, consisting of an elastic spring, which is confined in a tube; thus serving by its expansion, as a substitute for the long arm, and pointing out the weight of substances, by marks made on the moveable perpendicular bar in its centre. It would be superfluous to enter into a detailed description of these, portable machines : let it therefore suffice to observe, that such contrivance is not sufficiently accurate to determine the difference of ounces or drams; though it may answer the purpose of weighing larger quantities ; provided it be properly handled, and preserved from moisture, or rust.