AGATE. 
421 
Patrin mentions the carnelians found among the 
chalcedonies on the banks of the river Amour, as of 
a very fine paste, but faulty in their colour, which 
is not of an equal tint ; otherwise they would be 
very much esteemed. When the stone is formed 
of several layers, some of white chalcedony and 
others of carnelian, it becomes the car neiicin- onyx ; 
and when the colours are clean and distinct it forms 
the cameo, which is so highly prized by the jeweller. 
Sardonyx. 
It is very difficult to draw the line which sepa- 
rates the carnelian from the sardonyx, as they ap- 
pear to pass into each other by insensible shades. 
The stone takes the name of sardonyx when it is of 
a fine deep orange yellow, approaching to a brown 
colour : but it is found to vary in the depth of its 
tint, and sometimes to assume a greenish yellow or 
olive colour. We are taught to believe by some 
naturalists that the sardonyx derives its name from 
the island of Sardinia ; but Patrin thinks it more 
probable that it originated in the city of Sardis, the 
capital of antient Lydia in Asia Minor, the most 
beautiful specimens of this stone coming from that 
part of the world. 
The antients are said to have valued these stones 
very highly, Mithridates having collected four thou- 
sand specimens ; and as a further proof of the estima- 
tion they were held in, Herodotus relates the story of 
Polycrates, a tyrant of Samos, whose continual flow 
of prosperity was so great, that his friend the king 
