III. Melody of Colours.
A third source of pleasure arising from the inspection of visible objects, besides that of simple perception, arises from what may be termed melody of colours, as certain colours are more agreeable, when they succeed each other; or when they are disposed in each other's vicinity, so as successively to affect the organ of vision.
In a paper on the colours seen in the eye after looking for some time on luminous objects, published by Dr. Darwin of Shrewsbury in the Philos. Trans. Vol. 76, it is evidently shown, that we see certain colours not only with greater ease and distinctness, but with relief and pleasure, after having for some time inspected other certain colours; as green after red, or red after green; orange after blue, or blue after orange; yellow after violet, or violet after yellow; this, he shows, arises from the ocular spectrum of the colour last viewed coinciding with the irritation of the colour now under contemplation.
Thus if you make a dot with ink in the centre of a circle of red silk the size of a letter-wafer, and place it on a sheet of white paper, and look on it for a minute without moving your eyes; and then gently turn them on the white paper in its vicinity, or gently close them, and hold one hand an inch or two before them, to prevent too much light from passing through the eyelids, a circular spot of pale green will be seen on the white paper, or in the closed eye; which is called the ocular spectrum of the red silk, and is formed as Dr. Darwin shows by the pandiculation or stretching of the fine fibrils, which constitute the extremities of the optic nerve, in a direction contrary to that, in which they have been excited by previously looking at a luminous object, till they become fatigued; like the yawning or stretching of the larger muscles after acting long in one direction.
If at this time the eye, fatigued by looking long at the centre of the red silk, be turned on paper previously coloured with pale green; the circular spot or ocular spectrum will appear of a much darker green; as now the irritation from the pale green paper coincides with the pale green spectrum remaining in the eye, and thus excites those fibres of the retina into stronger action; on this account some colours are seen more distinctly, and consequently more agreeably after others; or when placed in the vicinity of others; thus if orange-coloured letters are painted on a blue ground, they may be read at as great distance as black on white, perhaps at a greater.
The colours, which are thus more distinct when seen in succession are called opposite colours by Sir Isaac Newton in his optics, Book I. Part 2, and may be easily discovered by any one, by the method above described; that is by laying a coloured circle of paper or silk on a sheet of white paper, and inspecting it some time with steady eyes, and then either gently closing them, or removing them on another part of the white paper, and the ocular spectrum or opposite colour becomes visible in the eye.
Sir Isaac Newton has observed, that the breadths of the seven primary colours in the sun's image refracted by a prism, are proportioned to the seven musical notes of the gamut; or to the intervals of the eight sounds contained in an octave.
From this curious coincidence, it has been proposed to produce a luminous music, consisting of successions or combinations of colours, analogous to a tune in respect to the proportions above mentioned. This might be performed by a strong light, made by means of Mr. Argand's lamps, passing through coloured glasses, and falling on a defined part of the wall, with moveable blinds before them, which might communicate with the keys of a harpsichord, and thus produce at the same time visible and audible music in unison with each other.
Now as the pleasure we receive from the sensation of melodious notes, independent of musical time, and of the previous associations of agreeable ideas with them, must arise from our hearing some proportions of sounds after others more easily, distinctly, or agreeably; and as there is a coincidence between the proportions of the primary colours, and the primary sounds, if they may be so called; the same laws must probably govern the sensations of both. In this circumstance therefore consists the sisterhood of Music and Painting; and hence they claim a right to borrow metaphors from each other: musicians to speak of the brilliancy of sounds, and the light and shade of a concerto; and painters of the harmony of colours, and the tone of a picture.
This source of pleasure received from the melodious succession of colours or of sounds must not be confounded with the pleasure received from the repetition of them explained above, though the repetition, or division of musical notes into bars, so as to produce common or triple time, contributes much to the pleasure of music; but in viewing a fixed landscape nothing like musical time exists; and the pleasure received therefore from certain successions of colours must depend only on the more easy or distinct action of the retina in perceiving some colours after others, or in their vicinity, like the facility or even pleasure with which we act with contrary muscles in yawning or stretching after having been fatigued with a long previous exertion in the contrary direction.