Corot was approaching his fortieth year, an age at which a man's ideas are generally fixed, when the great revolution of French landscape painting was accomplished under the influence of the English and of Rousseau. Trained in academical traditions, he might have remained steadfast in his own province. To follow the young school he had completely to learn his art again, and alter his method of treatment with the choice of subjects, and this casting of his slough demanded another fifteen years. When he passed from Italian to French landscape, after his return from his third journey to Rome in 1843, his pictures were still hard and heavy. He had already felt the influence of Bonington and Constable, by the side of whose works his first exhibited picture had hung in 1827. But he still lacked the power of rendering light and air, and his painting had neither softness nor light. Even in the choice of subject he was still undecided, returning more than once to the historical landscape and working on it with unequal success. His masterpiece of 1843, "The Baptism of Christ," in the Church of Saint Nicolas du Chardonnet in Paris, is no more than a delicate imitation of the old masters. The "Christ upon the Mount of Olives" of 1844, in the Museum of Langres, is the first picture which seems like a convert's confession of faith. In the centre of the picture, before a low hill, Christ kneels upon the ground praying; His disciples are around Him, and to the right, vanishing in the shadows, the olive trees stretch their gnarled branches over the darkened way. A dark blue sky, in which a star is flickering, broods tremulously over the landscape. One might pass the Christ over unobserved; but for the title He would be hard to recognise. But the star shining far away, the transparent clearness of the night sky, the light clouds, and the mysterious shadows gliding swiftly over the ground,--these have no more to do with the false and already announce the true Corot. From this time he found the way on which he went forward resolute and emancipated. [Illustration: DUPRÉ. THE PUNT.]