VOL. L.] PHILOSOPHICAL TRANSACTIONS. 233 



used either specula of metal, or balls of glass for the former of these purposes ; 

 as it is well known, that glass was not applied to the latter In optical uses till the 

 beginning of the 13th century. However, we may with greater probability pro- 

 pose another use for which the ancients might employ such plates of glass, as are 

 now under consideration, viz. the adorning the walls of their apartments by way 

 of wainscot. This he takes to be the meaning of the vitreae camerae mentioned 

 by Pliny, who intimates, that this fashion took its rise from glass being used by 

 M. Scaurus for embellishing the scene of that magnificent theatre, which he 

 erected for exhibiting shows to the Roman people in his sedileship. And we 

 may collect from the same author (what is further confirmed by his contempo- 

 rary Seneca), that this kind of ornament had been admitted, in his name, into 

 chambers in houses, baths, &c. Whether the plates used for this purpose were 

 stained with various colours (as mentioned above), or had tints of divers kinds ap- 

 plied to the back part of them, he pretends not to determine : but in either way 

 they would have a very agreeable effect. 



The last destination, which the obvious congruity of the thing itself, coun- 

 tenanced by the practice of many ages past, as well as of the present time, would 

 induce one to ascribe to such plates of glass, is that of windows for houses, 

 baths, porticos, &c. But he was sensible that whoever should be hardy enough 

 to advance such an hypothesis, would be censured as an innovator, in opposing 

 the general opinion of the connoisseurs in antiquity. These gentlemen are al- 

 most unanimous in asserting, that whenever we meet with mention made of 

 specularia in ancient writers (especially those of, or near to, the age to which 

 we must refer this fragment), we are to understand by that term nothing but 

 fences made of laminae, cither of a certain stone called from its transparent 

 quality, lapis specularis, brought first from Hispania Citerior, and afterwards 

 found in Cyprus, Cappadocia, Sicily, and Africa ; or of another stone of the 

 same nature, viz. the phengites. These, though expressly distinguished from each 

 other by Pliny, are yet reckoned by some moderns as one and the same thing ; 

 and thought to have been nothing but a kind of white transparent talc, of which 

 according to Mons. Valois, there is found a great quantity in Moscovy at this 

 day. Now that this lapis specularis, or phengites, was really used for windows 

 by the ancient Romans in their houses, &c. cannot be denied: since, according 

 to the opinion of the learned in antiquity, this usage is mentioned by Seneca, 

 among other improvements in luxury introduced in his time. But whether it 

 was so used exclusive of other materials (particularly glass), may he thinks ad- 

 mit a doubt. Salmasius is of opinion that nothing can be determined on this 

 point from the word specular itself, which seems to be a generical term, equally 

 applicable to windows of all kinds, whether consisting of the lapis specularis, or 

 any other transparent substance. And as (according to this learned writer) there 



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