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LVT. An EJJay on the Colours obtained from the metallic 

 Oxides, and fixed by Fufion on different vitreous Bodies. 

 J5y Alexander Brogniart, DireBor f the 'National 

 Manufactory of Porcelain at Sevres, Engineer of Mines, 



HE art of .employing metallic oxides for colouring by 

 fufion different vitreous matters, is of very great antiquity : 

 every body knows that the antients manufactured- coloured 

 glafs and enamel, and that this art was pra&ifed in particular 

 by the Egyptians, the firit people who in this manner imi- 

 tated precious itones. 



The practice of this art in modern times has been carried 

 to a high degree of perfection : but the theory has been neg- 

 lected ;' it is almoft the only one of the chemical arts in 

 which no attempt has yet been made to apply the new prin- 

 ciples of that fcience. 



The very Numerous works which treat on the method of 

 preparing and applying vitrifiable metallic colours, either con- 

 tain no theory, and confequently no general principles, or 

 give only explanations, founded on hypothefes, often ridicu- 

 lous, which formerly compofed the theory of chemiltry. 



One of the beft, becaufe it is the work of an enlightened 

 artift, is the ■Traits de la Veintre en Email de Monlamy. The 

 archives of the national manufacture of Sevres contain alfo 

 iimple and excellent proceffes for the fabrication of colours. 

 The authors of them are Meflrs. Bailly, FonteUiau, and 

 Moutigny ; but they are mere defcriptions, without any ob- 

 servation which can conduct to general principles. 



The other works, fuch as that of Kunckel, and the manu* 

 fcripts of Hellot in the pofleffion of the manufactory of Se- 

 vres, and the two Encyclopaedias, prefent only an undigefted 

 •aflemblage, a compilation without choice and without rea- 

 soning, of a multitude of procetfes collected from all quar- 

 ters. When fome knowledge of the art has been obtained, 

 it is eafier to, invent a procefs than to difcover among that 

 .variety of recipes the one which ought to be preferred. 



[j has been remarked, that one of the moil certain figns of 

 Ithe proofs made by a fcience towards perfection is the pof- 

 fibility it leaves of collecting the facts that compofe it into 

 one lyftem,from which general principles might be deduced: 

 it is at this epoch alone'that it deferves the name of fcience \ 

 and it is to an expofnion of its principles thus generalized 



* From the Journal des Mines t No, 67. 



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