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 produeed according to a certain rule. Can the science of colours 
lay claim to a similar distinction ? I look at a fine painting, and amvat once 
struck with the harmonious disposition of its beautiful colours. This isthe 
first feeling excited, and it is excited ina moment. I afterwards examine 
and study the composition by looking attentively now at onepoint 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 the Law of Varying Colours. 
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 cntruded *. 
* It may not be useless, perhaps, to mention that my rings are inverse to 
those of Newton ; his begin at the centre, mine at the circumference, where, 
_ from the nature of the electro-chemical process, the thinnest layers are depo- 
7 sited: the thickest layers are evidently those of the centre. “ 
