The striking of coin between two dies, which were required to accurately oppose each other, was an operation requiring great dexterity, and the results were not at all certain. The artisans at this stage of the work, hit upon the expedient of using both the obverse and reverse die in a ring of such a size and depth, as to be a guide to each of them. The balls or disks of metal being struck inside the ring, between the dies, were forced to assume an even thickness, and a circular form corresponding with the inside of the ring. After the ring had been used in this way for some time, it was engraved upon the inside, and the coins produced were not only circular in shape, but stamped upon their edges. Thus was produced the perfect coin, and through the introduction of machinery has secured uniformity in the result and saved an immense amount of labor in striking vast sums of money; the artistic beauty of some of the antique specimens has not been surpassed in modern times. PORTRAITURE UPON COINS. It is said that no human head was ever stamped upon coins until after the death of Alexander the Great; he being regarded as somewhat of a divinity, his effigy was impressed upon money, like that of other gods. The knowledge of coins and medals, through the inscriptions and devices thereon, is, to an extent, a history of the world from that date in which metals were applied to such uses. Events engraven upon these, remain hidden in tombs or buried in the bosom of the earth, deposited there in ages long past, by careful and miserly hands, only awaiting the research of the patient investigator to tell the story of their origin. Numismatic treasures are scanned as evidence of facts to substantiate statements upon papyrus or stone, and dates are often supplied to define the border line between asserted tradition and positive history. Gibbon remarks: “If there were no other record of Hadrian, his career would be found written upon the coins of his reign.” The rudeness or perfection of coins and medals furnish testimony of the character and culture of the periods of their production. This is equally true of that rarest specimen of antiquity, the Syracusan silver medal—the oldest known to collectors—and the latest triumph of the graver’s art in gold, the Metis medal. It is not generally known that the rarest portraits of famous heroes are found upon coins and medals. The historian, especially the historic artist, is indebted to this source alone for the portraits of Alexander, Ptolemy, Cleopatra, Mark Antony, Cæsar, and many other celebrities. Perhaps the valuation of a rare coin or medal may be estimated by reference to one piece in the Philadelphia Mint. It is an Egyptian coin as large as a half-eagle, and has on the obverse the head of the wife of Ptolemy—Arsinoe—the only portrait of her yet discovered. INCIDENTS OF HISTORY