The result of this life _en plein air_ became at once the same as it had been with Constable. Earlier artists worked with the conception and the technique of Waterloo, Ruysdael, and Everdingen, and believed themselves incapable of doing anything without gnarled, heroic oaks. Even Michel was hard-bound in the gallery style of the Dutch, and for Decamps atmosphere was still a thing unknown or non-existent. He placed a harsh light, opaque as plaster, against a background as black as coal. Even the colours of Delacroix were merely tones of the palette; he wanted to create preconceived decorative harmonies, and not simply to interpret reality. Following the English, the masters of Fontainebleau made the discovery of air and light. They did not paint the world, like the other Romanticists, in exuberantly varying hues recalling the old masters: they saw it _entouré d'air_, and tempered by the tones of the atmosphere. And since their time the "harmony of light and air with that of which they are the life and illumination" has become the great problem of painting. Through this art grew young again, and works of art received the breathing life, the fresh bloom, and the delicate harmony which are to be found everywhere in nature itself, and which are only reached with much difficulty by any artificial method of tuning into accord. After Constable they were the first who recognised that the beauty of a landscape does not lie in objects themselves, but in the lights that are cast upon them. Of course, there is also an articulation of forms in nature. When Boecklin paints a grove with tall and solemn trees in the evening, when he forms to himself a vision of the mysterious haunts of his "Fire-worshippers," there is scarcely any need of colour. The outline alone is so majestically stern that it makes man feel his littleness utterly, and summons him to devotional thoughts. But the subtle essence by which nature appeals either joyously or sorrowfully to the spirit depends still more on the light or gloom in which she is bathed; and this mood is not marked by an inquisitive eye: the introspective gaze, the imagination itself, secretes it in nature. And here a second point is touched. [Illustration: _Cassell & Co._ ROUSSEAU. SUNSET.]