304 1 COLOURS FOUND AT POMPEII. 



tion, but of a commencement of vitrification, ov rather to 

 be a true frit. 

 Of very an- The process by means of which the ancients obtained 



eient use. ^-g co ] our appears to be lost to us. Ail we can learn, on 



consulting the annals ot the aits, is, tlsat the use of this 

 colour dates from ages long prior to the destruction of Pom- 

 peii. Mr. Descotils observed a lively, bright, and vitreous 

 blue colour, in some hieroglyphic paintings in Egypt ; 

 and he satisfied himself, that this colour was prepared from 

 copper. 

 Somewhat Considering the nature of the constituent principles of 



analogous to t j • co ] our we CHU compare it only with the verditer of the 

 blue verditer. ' . . 



moderns ; but with regard to its use in the arts we may set 



against it to advantage our ultramarine and smalt, particu- 

 larly since Mr. Thenard has made known a preparation of 

 the latter, which admits of being used with oil. But ver- 

 diter has neither the brightness nor permanence of the 

 ancient colour; and both ultramarine and smalt are more 

 costly than a composition, the three ingredients of which 

 are so cheap. It would therefore be worth while, to endea- 

 vour to discover the process for manufacturing this blue 

 colour. 

 A Tight blue, No. 6 is a light blue sand, mixed with a few whitish par- 

 similar to the t ; c ] es> Analysis shows in it the same principles as in the 

 preceding. * -, * i 



preceding colour ; and it may be considered, as a composi- 

 tion of the same nature, in which the lime and alumine are 

 in larger proportion. 

 Rose colour. I have only to examine No. 7. This is a fine rose colour, 

 soft to the touch, reducible between the fingers to an im- 

 palpable powder, and giving the skin the colour of a pleas- 

 ing bloom. 

 Action nfthe This colour, exposed to the blowpipe, first blackens, and 

 blowpipe on it, a ft erV/U ,<} becomes white. It emits no perceptible smell of 



ammonia, 

 and of acids. Muriatic acid dissolves it with slight effervescence. From 



this solution ammonia throws down a fiocculent precipitate, 

 which is completely redissolved by potash. 

 Contains no Neither infusion of galls nor hidrosulphuret of ammonia 



indicates the presence of any metal in it. 



This 



