The Coin of the Realm

Explaining the fall of the Roman Empire has traditionally been left to philosophers and historians, who have variously placed the blame on wars, epidemics, social inequalities, indolence and overambition. More recently, specialists from other disciplines have taken their turn at scrutinizing Rome's downfall. A few years ago, a sociologist suggested that the empire had withered away after its upper classes died off from lead poisoning caused by lead-lined drinking and cooking vessels. Now a geochemist has concluded that Rome's troubles derived largely from the loss of its supply of silver, which fatally disrupted the Roman monetary system.

During a study of air pollution, Caltech's Claire Patterson decided to investigate the historical worldwide distribution of lead. Knowing that lead was obtained in ancient times as a byproduct of silver mining, he made a study of silver mining and stockpile records and discovered a significant fact: accidental loss diminishes a country's stock of silver at a rapid rate unless the metal is continually replenished from mines. Rome's silver, much of it used for coins, was abraded by handling, lost by corrosion and reworking, covered by soil or ashes, sunk in shipwrecks or buried in graves at the rate of about 2% a year. Such ''extreme volatility," says Patterson, means that if silver production stops, a nation's entire supply can disappear in about a century. Production in the silver mines of Rome began to decline about A.D. 200. By then, they were so deep that Roman engineers had no way of clearing them of water. After that, says the geochemist, "it was like being bled to death without knowing that one was bleeding." The result was the gradual disappearance of Roman coins and the return to an unwieldy barter system too crude to sustain the empire.

Bleak Future. Although man began to mine silver on a small scale in about 2500 B.C., Patterson says that it was not until Rome took control of the silver mines in Iberia that it was able to attain the economic strength necessary for the rapid expansion of the empire. Silver production, mainly in Iberia, peaked between 50 B.C. and A.D. 100, when some 30,000 tons were extracted; Roman legions were furnishing 30,000 fresh slaves a year then to maintain the ranks of miners at 150,000. By the 3rd century A.D., as production steadily decreased, Roman coins had deteriorated to silver-coated bronze, and by the 4th century, Rome was back to a barter economy and a bleak future.

Patterson notes that the glory of Greece also coincided with the productivity of her vast Laurion silver mines: when the silver gave out, so did Athenian power. After the decline of Rome, Patterson says, the next great silver discovery, in Central and Northern Europe, coincided with the end of the Dark Ages. Although silver losses have continued at a high rate--Patterson estimates that in the U.S. alone about half a billion dollars worth of silver coins were returned to the earth accidentally from 1900 to 1950--a sharp drop in silver mining will no longer have the disastrous effects of old. The paper money and bank credit used today, Patterson explains, offer a prospect of greater economic stability than the silver coins of Rome.

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