Scholars’ Corner: Correlation Established Between Silver Content of Coins and Economic Prosperity

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Modern archaeology tries to reconstruct from every clue available all aspects of ancient society—its economy and sociology, as well as its political history and building techniques. The possibilities, as BAR readers know, are infinite.

In this world of specialization, one scholar may dig up the evidence, another may analyze it and still a third may discover its significance.

Yaakov Meshorer of the Israel Museum, one of the world’s leading numismatists, was recently studying and analyzing Nabataean coins that had been dug up at numerous sites in Israel, Jordan and the Sinai. These enigmatic people inhabited and often dominated the desert and trade routes between the fourth century B.C. and the first century A.D. They also built magnificent desert cities, like Petra, Mamshit and Avdat. They left thousands of inscriptions in their own alphabet and language carved in the rocks of the desert trade routes.

Meshorer tried to squeeze from Nabataean coins every bit of knowledge concerning these elusive people. One of the things he did was to measure the silver content of their coins to see what the variation was. This was done by the specific gravity method.

The specific gravity method depends on the fact that objects of different volumes displace different amounts of water when immersed. First, a coin is weighed and placed in a graduated cylinder of water. The volume of water displaced by the coin is measured. Then, pure silver of the same weight as the coin is placed in a cylinder of water. The volume of water displaced is measured again. Silver is denser than any metals that would have been alloyed with it. Thus, silver takes up less space (volume) than an equal weight of these metals. (Two ounces of silver would displace less water than two ounces of a lighter alloy metal, for instance.) If a coin is impure, it will displace more water than the same weight of pure silver.

Calculating the percentage of silver in coins by the specific gravity method is relatively simple if a single metal alloy is present in the coin. If more than one alloy is present, the calculations become more complex.

During the period Meshorer studied—from 60 B.C. to 100 A.D.—he found that the silver content of the coins varied widely, from 20% to 96%. Meshorer published the results in his book, Nabataean Coins (Jerusalem, 1975).

At this point, one of the world’s leading Nabataean scholars, Abraham Negev of Hebrew University, enters the story. Negev began pondering the variations in silver content. Finally, he had the data put on a graph so he could study the ups and downs of silver content along a time line.

Then Negev correlated this data with other evidence to confirm or refute working hypotheses concerning economic conditions in the Nabataean kingdom. He also used the information to create new proposals and correlated his results with similar evidence from Roman coins. Negev recently reported his results in an article entitled “Numismatics and Nabataean Chronology” in the Palestine 008Exploration Quarterly (July–December 1982, pp. 119–128).

For example, Negev detected a sharp reduction in the silver content of Nabataean coins in 7 A.D. On the basis of this and other evidence, Negev suggested that it was then that the Nabataeans finally lost all control over the northern link of the Indo-Arabian trade route. Previously, the Nabataeans had attempted to keep the silver content of their coinage at about the same level as the Roman Empire coinage, indicating that until then the Nabataean economy was closely knit with the Roman international economy. Thereafter, however, the Nabataeans had a closed economy, isolated from the currency of international trade.

The Nabataeans nevertheless retained the wealth they had accumulated over the centuries. Thereafter, they built some of their most outstanding monuments, such as those at Petra,^a but silver no longer flowed into the Nabataean treasury as it had before.

Sometimes the evidence of the coinage correlates quite precisely with externally established events. For example, in the first three years of King Rabal II’s reign (70–72 AD.), the silver content of Nabataean coins was only 20%. These years must have been poor ones economically and were probably the years during which this minor king shared authority with his mother, who was the regent. In Rabal’s fourth regnal year (73 A.D.), however, the silver content of Nabataean coins more than doubled, jumping to 42.5%. At this point, Rabal came of age, the gloom that had characterized the first three years of his reign ended and the Nabataean economy suddenly improved. The silver content remained at the higher level for almost a decade. Then, in Rabal’s eleventh regnal year, a new and severe inflation set in from which the Nabataean economy never recovered. The silver content of Nabataean coins dropped back to 20% and remained at that level through 100 A.D.

It is fascinating to watch great scholars bring together tiny bits of disparate information, scientifically gathered, to reveal new insights about ancient societies.

Modern archaeology tries to reconstruct from every clue available all aspects of ancient society—its economy and sociology, as well as its political history and building techniques. The possibilities, as BAR readers know, are infinite.