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110 NATURAL HISTORY OF GEMS.
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introduces the valos in
its capacity of a burning glass as the brilliant invention of
Strepsiades (under the inspiration of Socrates) for the quashing of a
writ :—
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Orpheus
(170) recommends such an instrument as the most proper for kindling the
sacrificial lire, and ensuring the favour of the gods, the flame thus
kindled being called the fire of Vesta.
The
largest mass of Crystal ever seen by the Romans was that dedicated in
the Capitol by Livia, which weighed fifty pounds. Juba mentions a piece
found in the Topaz island of the Red Sea, a cubit in length ; * and
Bocchus describes specimens of wonderful magnitude found in Lusitania
in the Ammeae mountains, in shafts sunk down to the level of the water.
But the Indian sort was preferred to every other, although that found
in the Alps was also esteemed. The latter was extracted from rocks so
difficult of access that the miners had to be lowered down to them by
ropes, being guided by certain indications known to the experienced as
to the veins that would contain the Crystal. Pliny confirms the
assertion of
* According to the same authority, the " Island of the Dead,'' off the Arabian coast, also produced it.
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