422 
AGATE. 
of Egypt advised him to chequer his enjoyments 
by relinquishing some of his most favourite objects, 
that he might not be too much elated by his good 
fortune. Polycrates complied, and threw into the 
sea a beautiful seal of sardonyx, the most valuable 
of his jewels ; but a few days after some fishermen 
brought a fish for the tyrant’s table, which having 
swallowed the seal, it was thus returned to him 
again. The historian proceeds to say, that when his 
friend heard this he rejected all alliance with him, 
from his persuasion that such extreme good fortune 
would vanish in the end ; and that his prediction 
was verified by the death of Polycrates, who was 
murdered by Oretes, governor of Sardis, merely, it 
is said, because the governor wished to put an end 
to such continued prosperity. 
Onyx. 
This stone is the hardest of the flinty tribe, and 
is susceptible of a very fine polish. It consists of 
different coloured veins, which run parallel to one 
another, sometimes in straight, sometimes in curved 
lines. When the stone consists of two veins that 
run clear throughout, and of distinct colours, it is 
used for cameos, that is to say, those engraved bas- 
reliefs, of which the figures should be of one colour 
and the bottom of the stone of another. The Gre- 
cian artists carried this mode of engraving to the 
highest degree of perfection, and have left some pro- 
ductions to posterity which cannot be too much ad- 
mired. One of the most celebrated artists in this 
