“The air is part of the mountain, which does not come to an end with its rock and its soil. It has its own air; and it is to the quality of its air that is due the endless diversity of its colourings. Brown for the most part in themselves, as soon as we see them clothed in air the hills become blue. Every shade of blue, from opalescent milky-white to indigo, is there. They are most opulently blue when rain is in the air. Then the gullies are violet. Gentian and delphinium hues, with fire in them, lurk in the folds.”