Colour is therefore the procreatrix of design. Or, colour being simply the irradiation of light, it follows that all colour is composed of the same elements as sunlight, namely the seven tones of the spectrum. It is known, that these seven tones appear different owing to the unequal speed of the waves of light. The tones of nature appear to us therefore different, like those of the spectrum, and for the same reason. The colours vary with the intensity of light. There is no colour peculiar to any object, but only more or less rapid vibration of light upon its surface. The speed depends, as is demonstrated by optics, on the degree of the inclination of the rays which, according to their vertical or oblique direction, give different light and colour.
The colours of the spectrum are thus recomposed in everything we see. It is their relative proportion which makes new tones out of the seven spectral tones. This leads immediately to some practical conclusions, the first of which is, that what has formerly been called local colour is an error: a leaf is not green, a tree-trunk is not brown, and, according to the time of day, i.e. according to the greater or smaller inclination of the rays (scientifically called the angle of incidence), the green of the leaf and the brown of the tree are modified. What has to be studied therefore in these objects, if one wishes to recall their colour to the beholder of a picture, is the composition of the atmosphere which separates them from the eye. This atmosphere is the real subject of the picture, and whatever is represented upon it only exists through its medium.
DEGAS
THE GREEK DANCE—PASTEL
A second consequence of this analysis of light is, that shadow is not absence of light, but light of a different quality and of different value. Shadow is not a part of the landscape, where light ceases, but where it is subordinated to a light which appears to us more intense. In the shadow the rays of the spectrum vibrate with different speed. Painting should therefore try to discover here, as in the light parts, the play of the atoms of solar light, instead of representing shadows with ready-made tones composed of bitumen and black.
The third conclusion resulting from this: the colours in the shadow are modified by refraction. That means, f.i. in a picture representing an interior, the source of light (window) may not be indicated: the light circling round the picture will then be composed of the reflections of rays whose source is invisible, and all the objects, acting as mirrors for these reflections, will consequently influence each other. Their colours will affect each other, even if the surfaces be dull. A red vase placed upon a blue carpet will lead to a very subtle, but mathematically exact, interchange between this blue and this red, and this exchange of luminous waves will create between the two colours a tone of reflections composed of both. These composite reflections will form a scale of tones complementary of the two principal colours. The science of optics can work out these complementary colours with mathematical exactness. If f.i. a head receives the orange rays of daylight from one side and the bluish light of an interior from the other, green reflections will necessarily appear on the nose and in the middle region of the face. The painter Besnard, who has specially devoted himself to this minute study of complementary colours, has given us some famous examples of it.
The last consequence of these propositions is that the blending of the spectral tones is accomplished by a parallel and distinct projection of the colours. They are artificially reunited on the crystalline: a lens interposed between the light and the eye, and opposing the crystalline, which is a living lens, dissociates again these united rays, and shows us again the seven distinct colours of the atmosphere. It is no less artificial if a painter mixes upon his palette different colours to compose a tone; it is again artificial that paints have been invented which represent some of the combinations of the spectrum, just to save the artist the trouble of constantly mixing the seven solar tones. Such mixtures are false, and they have the disadvantage of creating heavy tonalities, since the coarse mixture of powders and oils cannot accomplish the action of light which reunites the luminous waves into an intense white of unimpaired transparency. The colours mixed on the palette compose a dirty grey. What, then, is the painter to do, who is anxious to approach, as near as our poor human means will allow, that divine fairyland of nature? Here we touch upon the very foundations of Impressionism. The painter will have to paint with only the seven colours of the spectrum, and discard all the others: that is what Claude Monet has done boldly, adding to them only white and black. He will, furthermore, instead of composing mixtures on his palette, place upon his canvas touches of none but the seven colours juxtaposed, and leave the individual rays of each of these colours to blend at a certain distance, so as to act like sunlight itself upon the eye of the beholder.
