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Lapis Lydius, Touchstone, Assaying

Lapis Lydius, Touchstone, Assaying Page of 384 Lapis Lydius, Touchstone, Assaying Text size:minus plus Restore normal size   Mail page  Print this page
154                 NATURAL HISTORY OF GEMS.
difference perceptible, they try another needle, until an exact coincidence is obtained. It is very singular that Tavernier should have known nothing of this method before he saw it generally employed by the Banyan money­changers : for as the Italian craftsmen are as immutable in their processes as the Hindoos themselves, they must bave possessed this simple method of assaying in that traveller's days.* To exhibit the economy of the Banyans he adds that they carefully wipe the stone, after using it, with a Jump of wax, which thus in course of time becomes charged with an appreciable quantity of fine gold.
Exactly a hundred years before, Abul-Fazel writes: "In this country the serafs (money-changers) know the degree of fineness from the colour and brightness of the metal, but for the satisfaction of others this grand rule has been introduced : the bunwary is composed of a number of bars of copper, or such-like metal, on the point of every one of which is fixed a small piece of gold and the degree of purity written thereon. When they want to assay the newly-imported gold they draw on the Touchstone a line of this and a line of the bunwaiy : and by comparing them together they discover the degree it is of." (Ayeen Akbary, p. 8.)
The assay of gold by fire has been described under Obryza (Aurum). The Roman assay of silver was equally simple. Filings of the article to be tested were thrown upon an iron chafing-dish made white-hot : if the silver kept its colour it was proved fine; if it turned red
* A truth curiously exemplified by Castellani's own experience : " But it was only in a remote corner of the Umbrian Marches at S. Angelo in Vado, a little district hidden in the recesses of the Apennines, far from eveiy centre of civilization, that we found still in use some of the processes employed by the Etruscans. There yet exists, in fact, in this district of Italy, a special school of jewelry traditional, somewhat similar, not indeed in taste or elegance of design, but at least in me­thod and workmanship to the ancient art."
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