as known to the Egyptians,/ 117 



the use of metallic oxides, is evident from the nature of the 

 colours applied to their glass and porcelain; and they were 

 even acquainted with the influence of acids upon colour, being 

 able, in the process of dyeing or staining cloth, to bring about 

 certain changes in the hues,* by the same means adopted in 

 our own cotton works, as I shall shew in describing the manu- 

 factures of the Egyptians. 



It is evident that the art of cutting glass was known to the 

 Egyptians at the most remote periods, hieroglyphics and vari- 

 ous devices being engraved upon vases and beads, made in the 

 time of the eighteenth dynasty; and some glass, particularly that 

 which bears figures or ornaments in relief, was cast in a mould. 

 Some have supposed that the method of cutting glass was un- 

 known to the ancients, and liave limited the period of its in- 

 vention to the commencement of the seventeenth century of our 

 era ; when Gaspar I^ehniann, at Prague, first succeeded in it, 

 and obtained a patent from the Emperor Rodolph II. ; but we 

 may infer from the authority of Pliny, that glass-cutting was 

 known to the ancients, and that the diamond was used for the 

 purpose as at the present day, even if they were ignorant of 

 the art of cutting this stone with its own dust. " Diamonds,"" 

 says that author,-f- " are eagerly sought by lapidaries, who set 

 them in iron handles, for they have the power of penetrating 

 anything, however hard it may be.^' He also states that eme- 

 ralds and other hard stones were engraved, though in early times 

 it was " considered wrong to violate gems with any figures or de- 

 vices ;"J and the diamond was found capable of cutting those 

 of the hardest quality, " for all gems," he observes, " may be 

 engraved by the diamond."§ 



It is difficult to decide upon the precise method adopted by 

 the Egyptians for cutting glass and hard stones ; but if nothing 

 remains to shew the process they employed, there is sufficient 



• Plin. XXXV. 11. { 



t Plin. xxxvii. 4. " Expetuntur (adamantis crustae) a sculptoribus, ferro- 

 que includuntur, nullam non duritiam ex facili cavantes." 



t Plin. xxxvii. Proem, and xxxiii. 1. He thinks the stone of Polycrates's 

 ring was a sardonyx, xxxvii. c. 1. 



§ Plin. xxxvii. 13, " Verum omnes (gemmae) adamante (scalpi possunt)." 



