PRODUCED BY ELECTRO-CHEMICAL ACTION. 119 



no counterpart in the other sense, — no succession of imaginary sounds 

 resulting from those which had previously reached the tympanum. 



In music there is awell-known and long-established distinction between 

 harmony and melody : the former arises from a certain series of sounds 

 produced all at the same time, the latter from the succession of certain 

 sounds produced according to a certain rule. Can the science of colours 

 lay claim to a similar distinction ? I look at a fine painting, and am at once 

 struck with the harmonious disposition of its beautiful colours. This is the 

 first feeling excited, and it is excited in a moment. I afterwards examine 

 and study the composition by looking attentively now at one point and then 

 at another. The merit of the piece was at first confined to the beauty 

 and harmony of the tints ; now the same tints being observed with more 

 attention awaken, or tend to awaken, the idea of the imaginary colours, 

 and thus acquire an expression which was wanting to them when they 

 were passed rapidly over. It has already been observed that the green- 

 yellow arose from the violet, and that the latter colour had a tendency 

 to produce a sensation of sadness on account of its involving a necessary 

 transition from an acute to a grave tone. The lower colours of the 

 spectrum (the red and the golden) have as their imaginary colours 

 azure-green and indigo. In both these cases the passage is from the 

 grave to the acute, and the two colours should, according to the law 

 under consideration, excite a feeling of cheerfulness. The theoretical 

 inference is confirmed by every one's experience. 



This analogy between sounds and colours may, after all, be rather ap- 

 parent than real. I thought myself bound nevertheless to mention it, 

 with a view to its development, and on account of the new ideas which 

 it might suggest. 



Additional Note on tlie Laio of Varying Colotirs. 



In speaking of this law, I have remarked an analogy which presents 

 itself in the central tints of the second ring. After having concluded 

 my labours it occurred to me to examine this interval once more, and I 

 noticed a fact which had escaped me in my first inquiries. Beginning 

 with the perpendicular incidence, in order to pursue the examination 

 through the other incidences, I observed the rings attentively. As my 

 point of view I took the central part of the second ring, and there, at an 

 angle between 70° and 80°, I perceived a new ring formed. This ap- 

 pearance was not accompanied by the disappearance of any of the 

 other rings : it was really a new ring formed under this great inclina- 

 tion at the centre of the second, which was at first almost entirely white. 

 I shall distinguish this ring from the others by the epithet intruded *. 



• It may not be useless, perhaps, to mention that my rings are inverse to 

 those of Newton ; liis begin at the centre, mine at the circumference, where, 

 from the nature of the electro-chemical process, the thinnest layers are depo- 

 sited : the thickest layers are evidently those of the centre. 



