204 NATURAL HISTORY OF PRECIOUS METALS, &c.
"
The plates then remain upon the ashes that are underneath them, and
twice again are covered with cow-dung in the manner before directed,
and these ashes also are preserved. When, after this manner, tlrree
fires have been applied, they call it seetihy. After that, the
plates are again washed in clean water and stratified with the
aforesaid mixture ; which operation must be repeated till six
stratifications and eighteen fires have been applied.
"
Then the assay-master breaks one of the plates, and if there comes out
a flat, dead sound, it is a sign of its being sufficiently pure ;
otherwise it must again be stratified with the mixture, and undergo
three more fires. Then from each of the plates is taken one mashah, of
which aggregate a plate is made and tried on the tonch-stone. If it is
not sufficiently pure, it is stratified once or twice more ; but the
desired effect is generally obtained by four stratifications."
The
chemist will perceive that this simple though tedious operation
produced exactly the same result as the modern process of quartation ;
it reduced all the silver alloy into a nitrate of silver, which was
easily recovered by the process termed " kookerat ;" whilst all the
baser metals were expelled and converted into their oxides.
The assaying of gold was called obrussa or obryza, the
etymology of which has been much disputed : although, in all
likelihood, it is a Spanish or Punic word, like all the rest connected
with gold-mining, and already quoted. In our own language an analogy
presents itself in the same department ; our mining terms come from the
Germans brought over to instruct our people in such operations ; hence
such technical words as " sumf," " brattice," " shaft," " blende,"
"nickel," " cobalt," &c.
Obryza, from the " test," came to imply the standard itself ; thus in the Byzantine Code (see Leo's ' Basilioje,'
