=Weighing Instruments.=--Of these there are two chief varieties, the simple balance (_libra_), and the steelyard (_statera_). In the former weight is set against, weight, at equal distances from the point of suspension. In the latter the object to be weighed, suspended from the short arm of the lever, is set against a small weight in an appropriate position on the long arm. The Greeks seem to have used the former only; the Romans used both. The use of the balance is illustrated by the Greek vase with the design of Hermes weighing the souls of Achilles and Memnon, and by the Roman lamp showing a stork weighing an elephant and a mouse (No. =474=). The steelyard was widely used in the Roman world. Owing to its portability, it was doubtless much employed by hawkers and street-sellers, as at the present day. We have also seen it above (p. 158) in the pork-butcher's shop (No. =459=). Out of the several steelyards exhibited here, one example, from Catania in Sicily (No. =475=; fig. 196), may be described in detail. It consists of a bronze rod of square section, divided into two unequal portions. The shorter portion has (_a_) two hooks suspended from chains attached to the end of the rod by a movable collar working in a groove (the object to be weighed was of course attached to these hooks); (_b_) three hooks, placed at intervals of about 3/4, 1-1/2, and 3 in. respectively from the collar, and suspended from small movable rings. These hooks are in different planes, corresponding to three of the four edges in the longer portion of the bar. The bar is graduated on three of its four faces, viz., on the first with nine divisions, each subdivided into twelfths. This scale was used when the steelyard was suspended by the hook nearest the graduated bar (as in the fig.). Objects weighing up to nine Roman pounds could thus be weighed by moving a sliding weight along the bar. The figure V will be seen at the fifth pound, the half pounds are marked by three dots, and the twelfths correspond to the _unciae_. The second face begins with VI and goes up to twenty-three pounds. It was used when the steelyard was suspended by the middle hook. The third face starts with XXII pounds, and goes up to fifty-nine pounds. In the second and third scales, multiples of five and ten pounds are marked by the figures V and X. Fifty pounds is indicated by the letter [Greek: N] +N+, which has that numerical value in the Greek notation. This third scale was used in conjunction with the hook nearest the collar. The sliding weight (now lost) must have weighed about 17,000 grs. (2-3/7 lb. avoirdupois). All the other steelyards here shown work on this principle, though many have only two graduated scales and two suspending hooks. [Illustration: FIG. 197.--STEELYARD FROM SMYRNA (NO. 476).]