cal colour is an error; a leaf is not green, a tree
trunk is not brown... 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... The composition of the atmosphere... is the
real subject of the picture... Shadow is not absence of light, but
light of a different quality and of a different value. Shadow is not
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 a 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... In a picture representing an interior
the source of light [windows] may not be indicated; the light
circulating, circling around 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 exchange 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 painter will have to paint with only the seven colours of the
solar spectrum and discard all the others;... he will, furthermore,
instead of composing mixtures on his palette, place upon his canvas
touches of none but the seven colours juxtaposed [Claude Monet has
added black and white] and leave the individual rays of each of these
colours to blend at a certain distance, so as to act like sunlight
upon the eye of the beholder." This is called _dissociation_ of tones;
and here is a new convention; why banish all save the spectrum? We
paint nature, not the solar spectrum.

Claude Monet has been thus far the most successful practitioner of
impressionism; this by reason of his extraordinary analytical power of
vision and native genius rather than the researches of Helmholtz,
Chevreul, and Rood. They gave him his scientific formulas after he had
worked out the problems