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Onyx, Nicolo

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ONYX.
265
brought down to Barygaza." Under the Ptolemies, the Indians themselves brought their own commodities to the city Eudœmon on the lied Sea, where they met the Egyptian traders as at a common entrepôt, like Alexandria in later times. But this place, notes our author, had been recently destroyed by Cresar. Two centuries and a half later, we find from Vopiscus (Aurelian III.), Firmus, a merchant of Alexandria, who usurped the purple in Aurelian's reign, had ships of his own trading direct with India. Scythicus also, to whom Epiphanius ascribes the true authorship of the heresy of Manes, was an Arabian trading regularly be­tween Alexandria and the Indian coast.
Both the Onyx and the Sardonyx are now largely imitated by artificially preparing the German species, a stratified quartz, in quality little superior to common flint, by which treatment stones are produced of much beauty, exhibiting well-defined and even layers of black and white, or red and white, equally clear and vivid. This is effected by boiling the stones, for the space of three weeks, in a solution of honey, in water constantly re­plenished as it evaporates, and afterwards steeping them in sul­phuric acid to bring out the black and white; in nitric for the red and white colours. The more porous strata imbibe the honey first-, and then the acid that carbonizes it—the more com­pact remaining unaffected by either. Such imitative gems are of no value, being imported in vast quantities from Germany, where the secret was either discovered some years ago, or else, as others assert, introduced from Italy, where it had been prac­tised from time immemorial. Pliny himself notes that all gems are brightened up by boiling in honey (mellis decoctu nitescunt), especially in Corsican, noted for its acridity, although all other acids are detrimental to them (xxxvii. 74) ; and Barbot states (but without giving his authority) that the Indians still improve the colour of their Camelians by roasting them in earthen pots after an exposure of several weeks to the heat of the sun. There is a very curious passage in Pliny, in the same chapter, bearing directly upon the use of honey in the treatment of gems :—" The Cochlides, now a very common gem, is rather an artificial than a natural production. It is said to be found in Arabia in large masses; and after a boiling of seven days and nights continuously
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