Instruments' of the Antients. 24 \ 



7iam, major es, clarioresque cernunlur : Letters, although 

 minute and obscure, are seen larger and clearer through a 

 glass globe filled with water *." 



80. ff I prove also, by a passage in Pliny, that the antients 

 were acquainted with the property of concave transparent 

 bodies, in rendering vision more clear, and also that they 

 possessed the art or" producing this figure. What Pliny 

 (lib. 37. cap. 5.) says of the emerald, appears to me decisive 

 on this point. " Iidem," (Smaragdi) " plerumque et con- 

 cavi, ut visum colligant. Quapropter decreto hominum, iis 

 parcitur, scalpi vetitis. Quorum vero corpus externum est, 

 eadem qua specula ratione, supini, imagines rerum reddunt. 

 Emeralds are mostly concave, that tiiey may collect the 

 sight. Hence, by the common consent of men, they are 

 spared, and the engraving of them is forbidden. But those 

 which have a plane surface, being held up, reflect the images 

 of things like mirrors." 



81. " On this passage I observe, 1st, That concave eme- 

 ralds were common in the time of Pliny ; as the adverb pie- 

 rumque (mostlv) proves. — 2dly,That this concavity must have 

 been artificial; for emeralds are not naturally concave; or, if 

 by accident one should be so, this could only happen very 

 rarely. For the same reason, then* that concave emeralds 

 were common, their concave figure must have been artifi- 

 cial ; so that the cotemporaries of Pliny must have possessed 

 theart of rendering emeralds concave, and of polishing them. 

 — 3dly, The phrase, ut visum colligant, can have no other 

 sense in this plaee, than that concave emeralds were proper 

 for rendering vision more distinct. What Pliny says a few 

 lines lower (when speaking of plane emeralds, he only at- 

 tributes to them the representation of images in the way of 

 mirrors) proves that he knew that coneave emeralds could 

 assist the sight in virtue of their concavity only; and in a 

 manner which those of other figures did not do. — 4'hly, If 

 the antients knew the propertv of concave emeralds in as- 

 sisting the sight, it was very just and reasonable to prohibit 

 the engraving of those to which they hid once given this 

 figure. But if they were ignorant of this property, and if 

 Pliny's words, ut visum colligant, had meant something 



* In the same chapter of this first book, Seneca has these words: 

 " Quidi/uidv/detur per humor em, longi ampliusvero est; Whatever is seen 

 through a liquid is far larger than the truth." And, cap. 3 tsid. the 

 same sntient philosopher says: '* Poma per <vitruni aspicienttbn, mullo 

 majora sunt, App'ts are much larger to those who view them, through 

 3 glass." See' Regmiul/, Oig. Ancien, de la Pbjs. Nov. t. 1. p. 174.— 

 'Translator. 



common. 



