I 



J02 COLOURS OBTAINED FROM METALLIC OXIDES. 



Kunckel's work Kunckel's work, the manufcripts of Hellot, in the polTef- 

 eiopidlas^reof fl0n oi the manu ^^ or y a t Sevres, and the two Encyclopae- 

 littlc value. dias, prefent only an undigefted collection, and a multitude 

 of proceflfes collected together from all quarters, without 

 choice or reafon. . With a flight knowledge of the art it is ea- 

 fier to invent a new procefs of fabrication, than to difcover 

 which among this multitude of receipts we ought to prefer. 

 Science is con- It has been remarked, that one of the moil certain criterions 

 vanced when the °^ ^ e P ro grefs made to the perfection of a fcience, is the pof- 

 fa&s compote a fibility it leaves of a re-union of the facts that compofe it, in 

 bodyofdoftnnc. a fo 0i \y f doctrine from which general principles may be de- 

 duced. At the prefent period only does it deferve the name 

 of a fcience, and it is to the exposition of thefe principles, that 

 the itriking, though inaccurate name of the philofophy of fci- 

 ence has been given. 

 The arts would The arts, which oftener compofe a branch of fcience, than 

 tufeadfar fimi- ^ e ilTn V^ e application of one of its parts, prefent facts equally 

 lar treatment, capable of being united in a body of doctrine ; they will attain 

 this valuable degree of perfection if practifed by men accuf* 

 tomed to trace the connections, and deduce the confequence* 

 of the events that pat's under their obfervation. 

 Philofophers Philofophers, whofe more elevated fpeculations feclude 



them ! aC ^ UirC them fr0m ^ e P ra ^ ice of thefe arts ' woulci tn en perceive their 

 principles with greater eafe ; they could more directly apply 

 their refearches to the progrefs of the art, which being then 

 directed by reafon, would become more certain, direct and 

 rapid in its advancement. 

 The prefent me- Being convinced that the art of preparing and ufing vitrifi- 

 make this difpo- aD ^ e colours is fufceptible of receiving the application of the 

 jition as to the means of perfection ; and that the facts of which it is com- 

 colourjr" 3 C P ^ are uifficiently numerous and accurate to be prefented 

 in a general outline, I have concluded that the precife know- 

 ledge of thefe facts, and of the principles which unite them, 

 which naturally lead to an explanation of a number of the re- 

 fults, might be interesting to chemifts, who, being occupied 

 by more general and important refearches, cannot attend to all 

 the details of a complicated art. 



I wimed like wife to give an accurate account of the princi- 

 ples of this art to chemifts, that they might determine with 

 certainty on the new operations to which the procefles fub- 

 mitted to their judgment might lead. 



Laftly, 



