462 plot's natubal histoet. [Book XXXVII. 



of so large a size, that they were employed in the East as 

 frontals for the horses of kings, and as pendants for their trap- 

 pings.'^ 



All precious stones in general are improved in brilliancy by 

 being boiled in honey, Corsican honey more particularly ; but 

 acrid substances are in every respect injurious to them. As 

 to the stones which are variegated, and to which new colours 

 are imparted by the inventive ingenuity of man, as they have 

 no name in common use, they are usually known by that of 

 *' physis j'"^ a name which claims for them, as it were, that ad- 

 miration which we are more ready to bestow upon the works 

 of Nature. But really, these artificial stones have names 

 without end, and I could never think of recounting the infinite 

 series of them, coined as they have been by the frivolous ten- 

 dencies of the Greeks. 



Having already described the more noble gems, and indeed 

 those of inferior quality which are found among the stones that 

 are held in high esteem, I must content myself with knowing 

 that I have pointed out those kinds which are the most deserv- 

 ing of mention. It will be as well, however, for the reader to 

 bear in mind, that, according to the varying number of the 

 spots and inequalities on their surface, according to the nume- 

 rous intersections of lines and their multiplied tints and shades, 

 the names of precious stones are subject to repeated changes ; 

 the material itself, for the most part, remaining just the same. 



CHAP. 75. THE VAEIOTJS FORMS OF PRECIOUS STONES. 



We will now make some observations in reference to pre- 

 cious stones in general, following therein the opinions that 

 have been expressed by various authors. Stones with a level 

 surface are preferred to those which are concave or protuberant 

 on the face. An oblong shape is the one that is most approved 

 of, and, next to that, the lenticular®" form, as it is called. After 

 this, the stone with a plane surface and circular is admired, 

 those which are angular being held in the least esteem. There 

 is considerable difficulty in distinguishing genuine stones from 

 false ; the more so, as there has been discovered a method of 

 transforming genuine stones of one kind into false stones of 



■8 "■ Phalerffi." See B. vii. c. 2, and B. xxxiii. c. 6. 

 "'^ "Nature;" i. e. "works of Nature." 

 *° " Lenticula." Like a lentil in shape. 



