The continuity of the ocean was suggested only by the gulls which, wheeling over what, when one looked at the picture, seemed to be solid rock, were as a matter of fact inhaling the moist vapour of the shifting tide. Other laws were discernible in the same canvas, as, at the foot of immense cliffs, the lilliputian grace of white sails on the blue mirror on whose surface they looked like butterflies asleep, and certain contrasts between the depth of the shadows and the pallidity of the light. This play of light and shade, which also photography has rendered commonplace, had interested Elstir so much that at one time he had painted what were almost mirages, in which a castle crowned with a tower appeared as a perfect circle of castle prolonged by a tower at its summit, and at its foot by an inverted tower, whether because the exceptional purity of the atmosphere on a fine day gave the shadow reflected in the water the hardness and brightness of the stone, or because the morning mists rendered the stone as vaporous as the shadow. And similarly, beyond the sea, behind a line of woods, began another sea roseate with the light of the setting sun, which was, in fact, the sky.