CAMEOS. 715 



Heat alone will often darken and improve the color of an onyx. 



Sulphuric acid will often improve the color of an onyx when 

 metallic oxides already exist within it. 



Nitric acid will often pale an onyx. 



The white or crystalline layers are seldom meddled with. They 

 can only be slightly reddened superficially by painting- with a solu- 

 tion of iron or a little thickened by heat or strong acid. 



Early carvings and engravings on hard stone were probably at 

 first cut with a sharp diamond splinter alone; in time tlie diamond 

 point was only used to sketch out the design on the polished snrfa(^(r 

 of the stone, the actual cutting being afterwards done more easily 

 and expeditiously by means of a hand drill, or some more powerful 

 tool analogous to the modern jeweler's lathe. The harder stones 

 require the help of oil and diamond dust to cut them, the soft iron 

 points which are used becoming thickly coated with microscopic 

 pieces of diamond and when rapidly revolved forming a very power- 

 ful cutting surface. 



Emery is mentioned by both Theophrastus and Pliny as being the 

 best material for rubbing down stones for engraving, the softer of 

 which were probably sometimes engraved with flint points. Emery 

 will polish a diamond; it is crystallized alumina and a variety of 

 corundum. 



For polishing ordinary stones rotten stone (powdered nluniina) 

 or tripoli powder (powdered silica) are most generally used. For 

 polishing, of course, the material used must be softer than the sub- 

 stance to be polished, and the points used for carrying the polishing 

 powders are also soft, copper, ivory, or wood. 



My examples are arranged in three divisions: Antique subject or 

 portrait cameos on small or flat stones; nnticpie vases and cups on 

 nodules of onyx or cut as cameos on blue or white glass; and the 

 later or Renaissance cameos. 



The Greeks were the most successful workers in cameo that have 

 existed, the few remaining specimens of their work done du.ring the 

 earl}^ Ptolemaic period (third and fourth centuries B. C.) are 

 unsurpassed, and the finest pieces made at Rome from the first cen- 

 tury B. C. to the third century A. D. were actually, the work of 

 (jreek artists. The universal acknowledgment of the surpassing 

 excellence of the Greek workmen is marked in an interesting way by 

 the fact that the extremel_y skillful Renaissance cameo cutters nearly 

 all signed their names, if at all, in Greek characters. 



Augustus Octavianus Caesar, second Emperor of Rome, who reigned 

 during the latter part of the first century, B. C, and the fii-st few 

 years of the Christian era, was evidently not only a splendid model 

 for the cameo cutter, but also a man of nuich leaiiiiiig and culture 



