M. NOBILl OX COLOURS, AND ON A NEW CHROMATIC SCALE. 9.5 



Tlie invention being now so far advanced as to be entitled to a place 

 among the arts, it was thought that it should have its distinctive ap- 

 pellation, and by the advice of the same illustrious body, that of Metallo- 

 chromy was adopted. Since that period I have made such improvements 

 in my method that the first results, though they appeared satisfactory at 

 the time, make but a sorryfigure when compared with those now obtained. 

 One of the great difficulties consisted in the necessity of producing a uni- 

 formity of tint on plates of certain dimensions ; for, my colours being ob- 

 tained by the effect of very thin plates applied to the surface of metals, 

 it is easy to conceive how hard it was to preserve such plates of a uni- 

 form thickness over the whole of an extensive surface. Great however 

 as the difficulties were, I thought I owed it both to art and to science to 

 do my utmost to surmount them. I thought it due to art, because this 

 would be extended by means of the uniformity of the tints, and to science, 

 because in the tints produced by plates of a particular thickness the 

 experimental philosopher ^^'ould find the means of investigating with 

 peculiar advantage the nature and properties of colours. 



At present I abstain from all detail relative to the method of obtain- 

 ing the homogeneous tints. The principle of the electro-chemical ap- 

 pearances seems now so fertile in results that its full development re- 

 quires a particular treatise. It will be a work of considerable labour, 

 and I have already commenced it by collecting and classifying all the 

 materials of this new department of physics in which, besides the other 

 methods of coloration, I intend to explain in detail those connected 

 with the production of uniform tints. In this place it is sufficient to 

 state that these tints are produced by substituting plates for the platina 

 point which forms the coloured rings. 



The object of this Memoir is more limited. It is to arrange these 

 homogeneous tints in their natural order, so that they may form a 

 scale or gamut which I shall henceforth designate by the epithet chro- 

 matic. 



Science never consults its interests so truly as when it aims at some 

 useful object connected with the arts. Such, I M^ould fain hope, will 

 be the direction of these researches. Artists, it is true, being generally 

 unacquainted with physical theories, will find it difficult to follow rae in 

 my inquiries. My labour, however will not be altogether useless to them, 

 if, as I intended, I have succeeded in treating certain parts of the sub- 

 ject in a manner likely to bring them within the reach of every under- 

 standing. 



The formation of the chromatic scales requires considerable time 

 and a hand well practised in work of this description. As they might be 

 generally useful I regret that the difficulty of their construction renders 

 a prompt and wide-spread circulation of tliem impo.ssible. I have tried 

 and am still trying to have them copied in oil and water colours, but 



