COLOURS OBTAINED FROM METALLIC OXIDES. 101 



concavities and the earthy matter of the Siberian iron, tend to * 

 the formation of a chain between fallen (tones and all kinds of 

 native iron. How far any real affinity exifts between! thefe 

 feveral fubftances, very obliging friends have afforded me an 

 opportunity to form fome judgment. I am indebted to Mr. 

 Greville and Mr. Hatchett for portions of almoft every known 

 native iron : and the Count de Bournon has done me the fa- 

 vour particularly to defcribe them as follows. 



(To be concluded in our next.) 



V. 



On the Colours obtained from Metallic Oxides, and fixed by 

 Means of Fufion on different Vitreous Bodies. By Alex. 

 Brongniart, Director of the National MannfaSlory of 

 Porcelain at Sevres, Engineer of Mines *, fyc. 



JL HE art of employing metallic oxides to colour the different The colouring 

 vitreous matters has been long known. It is well known that ? f glaffes by ox- 

 |:he ancients made coloured glafs and enamels, and that this c j ent# ver y an " 

 art was much practifed by the Egyptians, who were the firft 

 that imitated precious Hones by thefe means. 



In modern times the practice of this art has been brought to The theory neg- 

 a high degree of perfection, but its theory has been neglected, leftcd > 

 It is almoft the only chemical art to which the new principles 

 o£ this fcience have not been applied. 



In the numerous works which treat of the method of ufing pr erroneous, 

 and preparing metallic verifiable colours, the authors either 

 give no theory, and confequently no general principles, or the 

 explanations are founded only on the abfurd hypothefes which 

 formerly com pofed much of the theory of chemiftry. 



One of the beft publications, as it is. the work of an en- Montam *s 

 lightened practician, is The Treatife on Painting in Enamel, of treatife com r 

 Montamy. The archives of the national manufactory at Sevres, mended * 

 likewife contain fimple and good proceffes for the fabrication 

 of colours ; Bailly, Fontelliau, and Montigny are the authors ; 

 but they are fimple defcriptions, without any observations that 

 Jcad to general principles. 



* Journal des Mines, No . 67. 



Kunckel's 



