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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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