ι56	PRECIOUS STONES.
	Cameo. — The origin of the name has been referred to different sources, — to the Arabic "camaä" (an amulet), to the Greek " kauma " (heat), and with more probability to chama (a sea-shell used for carnei) ; the earliest adoption of the term for figures in relief was in the beginning of the sixteenth century. Antique Roman carnei are nearly all of large size, and not intended to be worn as ornaments, while, on the contrary, the Greek specimens were seldom above the ordinary dimensions. It is claimed by connoisseurs that shell and turquoise antique carnei are extremely doubtful ; the busts of the Cassars in shell, contained in the South Kensington Museum, belong to the early Renaissance. This form of engraving is generally cut on opaque or translucent gems, while intagli are more frequently found on transparent stones. Antique carnei on sardonyx were usually in three colors, if the layers occurred in regular succession, with the base of a translucent dark chocolate, the middle opaque white, and the upper layer a light brown or red. Sometimes the head of a warrior was cut in red, the helmet in green, and the breastplate in yellow, a rare combination of colors. Cameo is much later than intaglio, and since the Renaissance the number produced has been vastly greater than the latter, partly, no doubt, because they can be executed with greater facility. The Republican period of the Romans has been called the age, par excellence, for carnei, while those of Grecian work are extremely rare. Some of the best antique specimens date from the reign of Hadrian, in the second century of our era, after which the art began to decline. The oldest known cameo is said to be the Ptolemy and Berenice, on sardonyx, in the Odescalchi collection. The Romans of the present day, who make use of the Indian conchs, have carried the art of shell carnei to a surprising height of excellence.