M. NOBILI ON COLOURS, AND ON A NEW CHROMATIC SCALE. 95 
The 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 sorry figure 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 would 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 would 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 me 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. Asthey might be 
_ generally useful I regret that the difficulty of their construction renders 
a prompt and wide-spread circulation of them impossible. I have tried 
and am still trying to have them copied in oil and water colours, but 
