C 5° 6 ] 
The Onyx , Sardonyx , Agate-Qnyx> Alabafler of 
two Colours or Strata , as alfo certain Shells of dif- 
ferent Coats, were frequently engraved by the An- 
cients in Relief ; and thefe Sorts of Engravings are 
commonly called Cameo's. They alfo fometimes 
ingrafted a Head, or fome other Figure in Relief of 
Gold, upon a Blood Stone . 
Befides which there are fome Antiques, moftly 
Cornelians , that are cover'd with a Stratum of 
White. This Stratum has by fome been look'd 
upon as natural ;$ but it was really a fort of Coat of 
Enamel that was laid on. This was ufed only in 
the Times of the lower Empire. 
The Stones efteemed the belt for engraving upon 
were the Onyx and Sardonyx 5 and next to them the 
Beryl and the Jacinth. 
The Ancients engraved moft of their Stones, except 
the Onyx and the Sardonyx y juft as they were founds 
their natural Polifh excelling all that can be done by 
Art j but the Beauty of the feveral Species of Onyx's 
could only be difeover'd by cutting. 
The Merit both of Intaglio's and Cameo's depends 
on their Erudition, on the Goodnefs of the Work* 
manfhip, and on the Beauty of their Polifh. 
The antique Gems of Greek Work are the moft 
efteemed 5 and next to them the Roman ones, in the 
Times of the higher Empire. 
f 
XVIII. 
