Somogyi Múzeumok Közleményei 9. (1992)

Visy Zsolt: Római bronzmérleg Gyékényesről

66 VISY ZSOLT ZSOLT VISY: BRONZE STEELYARD FROM GYÉKÉNYES Resume The Somogy County Museum has long kept an incomplete bronze steelyard, which had been discovered at Gyékényes and given to the museum in unknown circumstances, where it had been registered under No. 4784. The existent part of the steelyard (statera) is made of bronze (see drawing No. 1 and picture No. 1). The weight arm with two suspensions as well as a part of the first, Omega-shaped member of the weight chain have remained, the rest of the balance arm was a rod that could be pushed into the remained tubular part, and by joining the two parts the above described way it could be used as a means of weighing. Although it cannot be excluded that the missing part was also made of bronze, it more likely could have been turned of wood, since A. Mutz has foung apple or pear tree fibres inside of the tubular bronze part of a similar steelyard. The steelyard found at Gyékényes was a two-position steelyard, its two suspensions enabled weighing in two different but complementary ranges. The calculation method illustrated in relation with the steelyard of Szentes renders the identification of the metrological features of incomplete scales possible, including the value of the traversable weight, too. The values used for the calculation are the lengths of the weight arms, as well as the distances per unit weight on the lever related to them, i.e. the lengths of the indexes. In the case of the scale of Gyékényes the length of the two weight arms are known: 36 mm and 53 mm respectively, and luckily the unit spacing related to suspension II. too: 11mm per pound (1pound=326,16 g). It is a lucky case because only one spacing falls on the existent part of the steelyard arm, namely the initial value of XV pound, and the value of XVI pound indicated by one dash only. This enables the application of the formula: t/s=p/G, where t is the length of the weight arm, s is the length of the related spacing, which equals to 1 pound, P is the value of the sliding weight in pounds, G is the 1 pound weight difference on the weight chain. The above formula comes from the reduction of two equations which include the dead weight of the steelyard, too, however, when reducing the equations, the data concerning the dead weight have been eliminated. Roplacing the values related to suspension II. the following result is received: Í2/S2=P/1, consequently P=53/11=approximately 5 pounds (1630,8 g). Out of the assumed 5 pound value of the sliding weight the spacing belonging to scale No. I. can be calculated: si=t-i/P=136 mm/5=27,2 mm=nearly exactly 1 digitus (1 digitus=18,48 mm). In position I weighing was possible minimally at a weight of 15 pounds to enable continuous werghing, since the smallest weight to be weighed on scale II. was 15 pounds. Although in some of the cases a weighing overlap of 1-3 pounds can be observed, now it is not taken into consideration. The original length is probably very close to the original value because in many cases the useful length of the steelyard arm is an integral multiple of the weight arm (ti) belonging to weighing position I. In the present case this ratio is 1:3. The weighing limit of scale II. was 48 pounds because the 11 mm (=1 pound) spacing can be measured 33 times on the 370mm section from the 15 pound mark. The place of the O-point depends on the inner weight conditions of the scales. The above introduced steelyard proves that the place of the O-point was defined in some procalculated way, with the moulding of the end of the T-member cast in one with the weight arm, obviously not knowing the weight relations of the ready steelyard. The above fact is an important detail concerning the production of ancient scales and leads us to the conclusion that the master brought the position (O-point) appearing in unloaded condition to the given place by subtle changes of the inner weight relations of the ready scales, in the present case changing the thickness of the beam, the size of the bronze rod on the outside part, as well as changing the length and/or the number of the chains, in the case of other scales by adding extra weights. The above introduced steelyard belongs to a rare type of scales. Steelyard of nearly identical shape and size have been discovered at Augst, the similarity is of such grade that it can hardly be doubted that they come from the same workshop. It can be observed that the basic length measurement and units of steelyard correspond to Roman length measurements or to their integral multiples or to their fractional values. This is not accidental since this type of scales were produced by a precise application of length measurements, the master only had to weigh the sliding weight and that too according to the ratio of the weight arm and to the related spacing. The applied unit of measurement was digitus in most cases. The steelyard of Gyékényes was made in the same workshop as the similar steelyard discovered at Augusta Raurica, it was used in the 2nd and 3rd centuries AD. There are no traces of the workshop, but it was most probably not in Pannónia but in Italy or somewhere in the Alps.