Hardly twenty years have gone by since "open-air painting" was introduced into Germany. At present, things are no longer painted as they are in themselves but as they appear in their atmospheric environment. Artists care no longer for landscapes which float in a neutral brown sauce; they represent objects flooded with light and air. People no longer wish for brown trees and meadows, for the eye has perceived that trees and meadows are green. The world is no longer satisfied with the indeterminate light of the studio and the conventional tone of the picture gallery; it requires some indication of the hour of the day, since it is felt that the light of morning is different from the light of noon. And it is the English who made these discoveries, which have lent to modern landscape painting its most delicate and fragrant charm. The very mist of England, the damp and the heaviness of the atmosphere, necessarily forced English landscape painters, earlier than those of other nations, to the observation of the play of light and air. In a country where the sky is without cloud, in a pure, dry, and sparkling air, nothing is seen except lines. Shadow is wanting, and without shadow light has no value. For that reason the old classical masters of Italy were merely draughtsmen; they knew how to prize the value of sunshine no more than a millionaire the value of a penny. But the English understood the charm even of the most scanty ray of light which forces its way like a wedge through a wall of clouds. The entire appearance of nature, in their country, where a damp mist spreads its pearly grey veil over the horizon even upon calm and beautiful summer days, guided them to see the vehicle of some mood of landscape in the subtlest elements of light and air. The technique of water-colour painting which, at that very time, received such a powerful impetus, encouraged them to give expression to what they saw freshly and simply even in their oil-paintings, and to do so without regard for the scale of colour employed by the old masters.