32 ANricjUE I'ASTE CAMEO, FOrND AT

is declared by the polislicd surface the small ring-stones of the sort retain in sj)ite of all tlie injuries of time and Nvear. The composition appears to be the same with that of the Egyptian blue enamel, the "artificial cyanos" of Theophras- tus,* so largely appUed to the decorative productions of the national art. That such enamelling had for its object the making terra cotta and steascliist |>ass for true lapis lazuli is made evident bv ^Elian's notice that the '" Iliiih Priest of the Egyptians used, when administering justice, to wear round his neck an image of the goddess Trutii, carved in snp- p/iiius."^ Tiie nature of tliis badge of olHce is abundantly attested by the existence of the numerous tablets in artificial cyanos, bearing figures of deities, and similarly intended for pendant jewels. !Sir II. Davy found by experiment tliat the cyanos used in Koman fresco-painting could be exactly reproduced by fusing together, for the space of two hours, 1.3 parts pure carbonate of soda, 120 pulverised flint, and 3 copper filings. A similar mixture, tlie proportion of flint somewhat increased for the sake of hardening it, would pro- duce a paste with all the qualities and appearance of the antique specimens. As Alexandria, upon the decay of Sidon, became the chief seat of the glass manufacture (one of its fabricants, Firmus, being actually weaUhy enough to dispute the empire with Aurelian), it is more than probable that paste gems " vitreie gemma? e vulgi annulis,"^ formed a large jiai-t of her exports ; and that, for the species retpiiring it, the arlificial cyanos (the invention of the country) was esjjecially put into refpiisition. The actual pr(jcess of making j)M.ste gems can be briefly described, if minute technical details be omitted. The im- pression of the work to be imitatt'il is taken in a mixture of fine tripoli and pi[)e-clay, rammed down in a little iron ca.sc of the dimensions retpiin-d. This htrms the ma(ni which, after drying, is placed within the fuinace, with a bit of glass of the projicr colour laid uj)on it. This is watched until observed to become plastic, and then earelully s(jueczed down with an iron spatula coated with Krciich chalk to j)revent adhesion. After antiealiiiL, the glass, on removal irom the matrix, presents an exact counterpart of the ♦ " On HUmoii," chap. .13, liirrnglyplii'-.

• " V'arift Hwtorift," xiv. 34. "Truth" * I'jiny'n U>rin fur thi* niftnnfniihiro.

in known by lh« tnll fcnthnr rininu from H. N. xxxv. 30. >i«T iifoil, »n<l which, plncinl nlonn, in hi»r