On the Colours ohtainedfrom the metallic Oxides. 343 



that the appellation, more impofing than correct, ofphilo- 

 fophy of fcience has been given. 



The arts, which are often rather a branch of a fcience than 

 the mere application of one of its parts, prefent fadts equally 

 fufceptible of being united in a fyftematic form : to carry 

 them foon to perfection, it is fufficient that they are practifed 

 by men habituated to diitinguifh relations, and to deduce con- 

 fluences from them. 



The learned, who by more elevated fpeculations are re- 

 moved from the practice of the arts, perceive the principles 

 of them more readily : they can apply their refearches in a 

 more direct manner to the advancement of them ; and their 

 progrefs, guided by reafoning, will be more certain, more 

 direct, and more rapid. 



I obferved that the art of preparing and ufing vitrifiable 

 colours was fufceptible of the improvement I have pointed 

 out, and that the facts of which it is compofed begin to be 

 fufficiently numerous and correct to be exhibited in a general 

 manner. I have thought that an accurate knowledge of thefe 

 facts, and an expofition of the principles by which they are 

 connected, and which mud naturally lead to an explanation 

 of a great many of them, might be interefting to chemifts, 

 who, employed in more general and more important re- 

 fearches, cannot be acquainted with all the details of an art 

 which is exceedingly complex. 



I was defirous alfo to give chemifts an exact knowledge of 

 the principles of this art, in order that they may be enabled 

 to determine with more certainty what novelty there may 

 really be in the procefles fubmitted to their opinion. 



In a word, I have thought it might be of utility to the 

 arts, and that it was the duty of the national manufactory 

 of Sevres to make known the pretended fecret of the compo- 

 sition of thofe porcelain colours which are unalterable in the 

 fire. It is well known that thefe colours were prefented to 

 he Inftitute, in the year 6, by a porcelain manufacturer 

 juftly citeemed for the beauty of the works which come from 

 his manufactory. I mould not have ventured to publifh this 

 fecret had it been intruded to me; but when it is known, [ 

 hope I (hall not be fufpected of having in the lead abufed the 

 confidence repofed in me. 



From what has been faitl it may be readily feen that my 

 object is not to give a detailed account of the exact compofi- 

 tjon of all the vitrifiable colours; fuch a labour cannot be the 

 fubject of a fmgle memoir. 



It is well known that all vitrifiable colours have for their 

 Y4 bafis 



