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ed, and form the red, and the feeblest and most rapid are most refracted and form the violet. But the whole of the broken rays are not represented by the colours which meet the eye in the spectrum; for at either extremity, where the red and violet fade out of sight, a succession of rays spread out, invisible to our eyes, but which might be to some extent discernible had we the night-eyes of some of the lower animals. The invisible rays at the red end are the strongest and rarest in the spectrum,-only showing themselves by giving out heat, and an electricity which is positive; those at the violet end are the feeblest and densest, only showing themselves by their chemical or actinic properties, and by an electricity which is negative. Thus the spectrum exhibits a - complex phenomenon. Firstly, we have a series of rays steadily increasing in rapidity and weakening in force of vibration, from one end to the other (similar in this respect to the atmospheric vibrations which produce Sound, which, emerging from silence as the spectral colours emerge from darkness, run through the scale of the musician, getting quicker and feebler in their vibrations, until they again become inaudible, the ear hearing sounds, as the eye sees colours, only so long as the vibrations continue within a certain range of velocity and force, which varies somewhat in different individuals and animals,-the savage Indian, for instance, hearing sounds and seeing objects where we can see or hear nothing; and dogs and the lower creation exhibiting the same powers to a still greater extent.*) But superimposed upon this steadily ascending gamut of vibrations, we have another phenomenon, -namely, that one-half of the rays of the spectrum are electrically positive and give out heat, and that the other half are negative and produce chemical
action; † and that in the centre those opposite influences neutralise each other. The varying phenomena of Colour, then, are not owing to a mere difference in the vibratory speed of the rays of the spectrum, but also to the electric difference of these rays, which, positive at the red end, and negative at the blue, flash up into yellow or white light in the centre where they meet.
In considering, then, the impression made on our eye by the colours of the spectrum, there are two points to be considered. In regard to illuminating power, the strongest point of the spectrum is the yellow,-in point of vibratory power, it is the red; and the colour which makes the strongest impression on our visual sense is the red-orange or scarlet, which, lying between the red and yellow, combines in fullest force the illuminating and vibrating powers. Hence it would appear that Colour is a vibratory phenomenon of the ethereal rays,-intermediate between Heat on the one hand and Actinism on the other, and attended by an overlapping of the electro-positive and electro-negative rays, of which Heat and Actinism are the representatives. But whether heat and actinism are not themselves the necessary products of a certain rate of vibration in the ether, and so the whole phenomenon of Colour be practically reducible to one of ratio of vibration, we do not profess to say. Men will get at the root of all those things by and by. Meanwhile, it is instructive to observe, from the paper upon Radiant Heat lately read before the British Association by Professor Powell, that heatrays, or rays emanating from a hot body, when refracted, present identically the same phenomenon as those of light:-namely, that the rays of the heat-spectrum which vibrate most slowly have a heating but not an
* There is a Bosjesman tribe in South Africa, who exhibit in a remarkable manner the phenomenon called Nyctalophia,-sleeping and resting during the day, when their eyes, either from natural or acquired organisation, cannot bear the light of the sun, and carrying on their main pursuits during the night.
It is this difference in the chemical action of the various rays which produce colour that constitutes the greatest stumblingblock in the way of photography, the colours at the blue end of the spectrum making an undue impression on the chemical surface compared with the others. This difficulty is being obviated, but, much as photography has achieved, we believe the art is still in its infancy.
illuminating power; those of greater velocity, a luminiferous property also; and those of the greatest velocity, little heating or luminiferous, but higher chemical power. The reflected rays from the moon form a curious illustration of these and our preceding statements, the strong electro-positive heat-rays of the solar beam being absorbed by the lunar orb, while the feebler and more rapidlyvibrating rays are reflected to our planet, and bring us a certain amount of illumination combined with a strong chemical influence; which latter shows itself, inter alia, (especially in tropical countries), by the well-established fact of the rapid decomposition of butcher-meat, &c., when exposed to the lunar beams.
sounds, and ever produces a disagreeable effect upon the senses. A coloured grey or dull dingy brown is the most general result of the mixture of discordant colours; and this is precisely the colour of mud-which by universal consent is pronounced disagreeable, although Lord Jeffrey was of opinion that people should like that colour as much as any other! Human nature, however, prefers the pure bright colours of the spectrum; and artists should remember-in these days of loaded palettes and infinitesimal tints
that brilliant and beautiful, or what Ruskin calls "holy" colouring, can only be produced by the use of the primaries, either side by side or in mixture. It must be remembered, also, that earthy pigments, however pure, are but poor representatives of the ethereal dyes, and that many things can be done with the latter which, owing to their imperfection, cannot be accomplished with the other. For instance, by means of a lens, we can reassemble the scattered rays of the solar spectrum and once more produce white light; but all the care in the world will not make a mixture of red, blue, and yellow paint, in the proper proportions, produce anything better than a neutral grey. The artist's palette contains only the dry bones of colour, which he can never vivify with the light of heaven.
There are some very curious phenomena connected with Colour, to which we desire to direct attention. For example, if yellow be presented to one eye, and blue to another, in such a way that each eye sees only its own colour, the result on the sensorium will be as if these two colours were seen mixed; in other words, we shall fancy we see green. In this case the yellow and blue, thus simultaneously presented, act on the visual sense in the same way as the sense of hearing is affected by two harmonious notes of music, the vibrations of which blend in producing a chord which is something between the two. In like manner, the vibratory rays of the blue on the one optic nerve, and of the yellow on the other, harmoniously blend with and modify one another when confluent on the sensorium, and produce a tertium quid. We may add that it is this Law of Harmonious Vibration which (in optics as in music) causes some colours to blend better than others. The primary colours of the spectrum, like the notes of the fundamental chord in music, blend beautifully, and are pleasing alike when seen mixed, side by side, or in succession. But when we come to mixtures of the secondary and tertiary colours, it cannot fail to be perceived that brilliance of hue is vanishing more and more; and there are some colours whose union produces nothing but a muddiness. This is the result of discord, which tends to extinguish light and colours, as it tends to destroy
Another phenomenon, curious in itself, and important as illustrating the action of colour upon our senses, is that displayed in what have been called the accidental colours. These show themselves in various ways. If the eyes are fixed upon a red wafer upon a white ground, the wafer will appear bordered with a faint greenif the wafer be yellow, the border will be blue-if green, purplish white-if blue, reddish white-if black, by a vivid white. And if the eye be wholly removed from one of these wafers, and fixed on the white ground, it will there perceive a phantom wafer of the colour of the border which surrounded the real one. In these cases, as may be seen, the phantom colours are always the complementaries (or opposites) of the actual ones. A more complex form of this phenomenon is, that if, after looking for some time fixedly at red, so as to excite in your eye
an aptitude to see in succession green, you turn your gaze upon a yellow, you will receive an impression resulting from a mixture of green and yellow, the latter colour being modified by the phantom-supplementary of the red. These curious phenomena explain many facts remarked by dealers in coloured stuffs, and often greatly inconvenience artists who, wishing to imitate exactly the colours of their models, work at them so long at a time as to become partially insensible to the true tones. The experience of dealers in coloured stuffs shows, that when a purchaser has for some time looked at a yellow fabric, and is then shown orange or scarlet stuffs, he takes them to be amaranth-red or crimson; for his eye, excited by the yellow, has acquired an aptitude to see violet, and in consequence all the yellow of the scarlet or orange stuff disappears, and he sees red, or a red tinged with violet. A second fact connected with the phenomenon of "accidental colour" is, that if there be presented to a buyer, one after another, a dozen pieces of red stuff, he will consider the last five or six less beautiful than those first seen, although the pieces be identically the same. "What is the cause of this error of judgment? It is that the eyes having seen six or seven red pieces in succession, are in the same condition as if they had been looking fixedly for the same period at a single piece of red stuff; so that they have a tendency to see the complementary of Red-that is to say, Green. This tendency necessarily enfeebles the brilliancy of the red of the later-seen pieces [by dashing it with green]. And in order that the merchant may not suffer by the fatigue of his customer's eyes, he must take care, after having shown the latter six or seven pieces of red, to present to him some green pieces, in order to restore the eyes to their normal state. If the sight of the green be sufficiently prolonged to exceed the normal state, the eyes will acquire a tendency to see red-in which case the last six pieces will appear more beautiful than the others."*
The leading fact involved in those
singular phenomena is, that whenever the visual sense has been long acted upon by a certain colour, nature at once relieves and gratifies itself by calling up a spectral colour which is the harmonious opposite of the one beheld. And this either simultaneously (as a fringe round the object, if it be small, or by blending with and modifying its hue, if large)—or in succession, after the coloured object is removed. These spectral hues, to use the common phrase, have no existence in the outer world, they exist only upon the retina of the eye; and are the result of the physical constitution acting in accordance with the wants of the animating Spirit within. We have no doubt, however as the laws of Matter and of Mind are identical, and as the former always tends to produce what the latter naturally desires-that a similar phenomenon does exist in the outer world, although too feebly to be discernible; and that the efflux of a certain kind of rays (say red) always tends to produce complementary vibrations (say green) in the surrounding ether. We know that this is the case with regard to sound; for whenever any note is produced, the surrounding particles of metal or air always produce a series of complementary notes called the harmonics. Maupertuis long ago maintained that, after having listened to any note, the mind expects to hear one of the harmonics of that note. He was unquestionably right; and if he had said that the mind actually does, in certain cases, hear in imagination the expected note, and is all the more shocked when a wrong note comes, he would have been still more correct. In optics, as we have seen, this mental process is most apparent, -any given colour never failing to excite on the retina, and suggest to the mind, a colour which is the harmonious complementary of the one beheld. Thus, in Colour, we have the Law of Sympathy or Harmony made visible in its operation on the mind, while in Sound we have it made most perceptible in the outer world; but we entertain no doubt that its operation in both cases is at once physical and
* CHEVREUL On Colours.
metaphysical, influencing alike the nature without and the nature within.
That pressure upon the eye produces spectral colours, and that a sharp blow upon it makes us fancy we see a flash of light, is a fact known to everybody-but, like many another everyday phenomenon, its explanation has a good deal puzzled philosophers. Goethe attempted to explain it by the hypothesis that light resided in the eye, and came forth when thus strikingly appealed to; and Mr Field, taking fundamentally the same view, alleged that the eye secreted light, and thus gave it off. The real solution, as generally happens, is much simpler than the conjectured ones. All sense of light and colour, as we have said, is produced by ethereal vibrations upon the nerve of the eye; and the explanation of the above phenomenon is, that by pressure or concussion, the optic nerve is set a-vibrating, occasioning a sense of sight in the sensorium and mind. The brain is carefully protected by the hard covering of the skull, but if its particles happen to be set a-vibrating by a sharp dingling blow, the same sense of sight follows -as was recorded, for instance, in the case of the present Emperor of Austria, when violently struck with a poniard in the back part of the head by the Hungarian assassin at Vienna. In truth, all our sensations are produced by a vibratory motion in their respective nerves. The nerves peculiar to each organ, indeed, are susceptible of only one class of impressions-those of the eye, light and colours; those of the ear, sounds; those of the palate and nose, taste and smell. But this is simply owing to the fact that each requires a peculiar kind of matter to set it a-vibrat
ing; and if any one substance sufficed to set all of these various sets of nerves a-vibrating, it would at once produce all their varied phenomena. There is one substance, but one only, which has this power-namely, electricity; and its action, as is well known, actually does produce in all the organs of sense sensations peculiar to each in the eye, a flash of light; in the ear, sounds; in the nose, an odour; in the palate, a taste; in the skin, a pricking feeling-all in the same person and at the same moment of time.
Several attempts have of late years been made to construct a true science of colour—an important task, which has been long impeded by the unfortunate prevalence of the false theory of Beauty of which Lord Jeffrey was the cleverest expounder. The most successful of those inquirers into the nature of colour are Mr D. R. Hay, the appearance of whose Laws of Harmonious Colouring more than a quarter of a century ago, first gained public attention to this subject, and who has continued to develop his views in later and more costly works—and M. Chevreul, Member of the Institute of France, who has recently directed his able and pains-taking mind to this subject. This latter gentleman, who is favourably known for his discoveries in chemical science, was induced to devote his attention to Colour in consequence of his being appointed by his Government to superintend the dyeing department of the royal manufactories at the Gobelins. His work, accordingly, is purely scientific in its character, and by no means inviting to the general reader; but it contains a great deal of most valuable matter for those who are employed in work which requires taste in colouring.*
While praising very heartily M. Chevreul's book, we feel called upon to pass a word of animadversion upon the translator's preface, which appears to us to be written throughout in a very objectionable spirit. M. Chevreul, a foreigner, is doubtless ignorant of our English works upon Colour; but for his translator to affect to scoff at the writings of such men as D. R. Hay, Field, and others, is as unjust as it is in bad taste; and we can only account for his having done so by supposing that he considers running down the works of others is the best way of commending his own translated volume. Mr Martel would do well to recollect -if indeed he knows anything about the matter-that Mr Hay published an able and most useful book on Colour and Decoration a quarter of a century before Chevreul ever wrote a line upon the subject; and that in one of his later works, The expressly points out this Law of Simultaneous Contrast which the French author
o ably and usefully spun into a volume.
M. Chevreul's book, in fact, is an account of his researches on what he calls the Simultaneous Contrast of Colours. In his preface he says:"In endeavouring to discover the cause of the complaints made of the quality of certain pigments prepared in the dyeing laboratory of the Gobelins, I soon satisfied myself that if the complaints of the want of permanence in the light blues, violets, greys, and browns, were well founded, there were others-particularly those of the want of vigour in the blacks employed in making shades in blue and violet draperies-which had no foundation; for, after procuring blackdyed wools from the most celebrated French and other workshops, and perceiving that they had no superiority over those dyed at the Gobelins, I saw that the want of vigour complained of in the blacks was owing to the colour next to them, and was due to the phenomena of the contrast of colours." What, then, is this law of simultaneous contrast of colours? It is, that when we regard attentively two coloured objects at the same time, neither of them appears of the colour proper to it (that is to say, such as it would appear if viewed separately), but of a tint resulting from the proper colour and the complementary of the colour of the other object; and that, if the colours of the juxtaposed objects are not of the same tone, the lightest tone will be lowered, and the darkest tone will be heightened.
To explain. We know, from the phenomena of the spectral or "accidental" colours described above, that a red spot tends to diffuse over the surrounding space its complementary colour, green
incline to orange, and the blue to green. If we take Yellow and Blue, the former will incline to orange, and the latter to violet. The fundamental reason of this phenomenon is, that each colour tends to diffuse its complementary hue over the colour or colours placed next to it. But this tendency is intensified by the physiological fact, that if any of our senses receives a double impression, one of which is vivid and strong but the other feeble, we do not perceive the latter; and that this is particularly the case when they are both of the same kind. For instance, if two knocks are given simultaneously at the opposite ends of a room, one very loud and the other weak, we only hear the strong one. Now, when red and blue are presented to the eye, the strength of the blue renders us insensible to any tinge of that colour which may be in the red, making the red yellower; and so with other colours. Nevertheless, the influence of this law in modifying juxtaposed colours must, we think, be little more than theoretical when compared with the far stronger influence exercised in this matter by the law of complementary colouring.
Let us give a few more examples of the changes produced by the contrast of colours :