Jere's Ars Magica Saga: Weights

Weights and Measures

In Byzantium, as in Islam and the West, weights and measures are of fundamental importance for the orderly exchange of goods (as well as coins). The place of these ubiquitous objects in the daily round of commercial transactions is illustrated in the Book of the Eparch, a tenth-century compilation of trade ordinaces. It mentions two types of weighing implements: the steelyard scale, for gross weighing (e.g., salted fish, pork, vegetables or nails) and the balance scale, for fine weighing (e.g. Incnense, myrrh and cinnamon). A steelyard is an unequal arm balance - a rod consisting of a longer and shorter portions. Pans or hooks attached by chairs to a shorter section hold the load to be weighed; a counterpoise is suspended from the longer portion, which is provided with engraved scale marks. The counterpoise is mived along the rod until the rod is horizontal; the load's weight is indicated by the scale mark where the counterpoise comes to rest.

In the Roman weight system, the libra (pound) occupied a central position; this position was occupied in the Byzantine weight system by the logarike litra (recokening pound). The logarike litra is a continuation of the libra and is identical with it, as is the oungia (ounce), the twelfth part of the logarike litra, with the Roman uncia (ounce). Subdivisions within the Byzantine weight systems are as follows: 1 logarike litra = 12 oungiai = 72 exagia = 1,728 keratia = 6,912 sitokokka. The Byzantine litra may also refer to a pound of gold which is subdivided: 1 litra = 72 nomismata.

Wheat was purchased by the modios; that is, by the bushel. As a rile this was the sea bushel or thalassios modios (in weight, 40 logarike litrai); as a measure of capacity the sea bushel equals 17 liters. Two smaller measures of capacity are termed modios: the monasterikos modios (monastery bushel, which is 4/5 of a thalassios modios (approx. 13.6 liters) and the annonikos modios, which is two thirds of a thalassios modios (approx. 12.8 liters).

Wine was exchanged in Byzantium by the metron (measure). The largest measure is the thalassion metron (sea measure) (which is 10.2 liters); with smaller measures of capacity again being the monasterikos (at 8.2 L) and annonikos (at 8.2L). Oil was also purchased by the metron, in this case it seems only the thalassion (8.5L) and the annonikos (5.6L), as well as the tetartion (quarter).

All the units that have been discussed are official weights and measures; other systems are often employed at the local level.

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Last modified: Thurs Dec 10, 1998