CHALCEDONIUS.                                  159
	proves it to have been the royal signet that graced the wrist of some Artaxerxes or Darius of the later times of the Achsemenian dynasty. Scarabaei of Etruscan work, as well as good Greek and Roman intagli, frequently occur in this material, but engraved on the Sapphirine in preference to any other sort; and justly so, for it is an extremely pretty substance, often approaching to the pale Sapphire in colour, though devoid of its brilliancy. The Girasol is sometimes improperly called the Opaline, hence antique works in it are often described as executed in real Opal, a stone in which, (with perhaps a single exception) they never occur. Busts and heads, in full and in bas-relief, and of considerable volume, were executed by the Romans in Calcedony. The most important of these are the Marlborough Medusa in pure Cal­cedony, in the grandest style, and the bust of Matidia, supported upon a peacock (typifying her deification), and three inches high; a work of the highest merit in point of art, though the material is brownish and turbid. Such monuments afford another proof that this substance was included amongst Pliny's inferior Jaspers : perhaps his Capnias, " stained as it were with smoke," for he goes on to mention a statuette of Nero in armour, 15 inches high, formed out of one stone; and in no other substance do antique works in full relief occur of such magnitude as in Calcedony. Another very grand work, in three-quarters relief and of considerable dimensions, was a head of Augustus, in a style of the utmost perfection, executed in an opaque species much like ivory; perhaps a real Cacholong or impure Opal1 (Fould Gems). That our two commonest species of the stone were the Leucachates and the Cerachates, White and Wax Agates of the ancients, can hardly admit of a doubt. Dionysius describes the Choaspes as carrying down in his torrents the beautiful