In landscape as in all other branches of painting, whatever is ephemeral in nature, or of uncommon experience, should be avoided. Rare sun effects and exceptional phases of atmosphere should not find their way into pictures, while strokes of lightning and rainbows should only be present when they are necessitated by the design, and then must be subordinated as far as possible. Of all these things the most strongly to be deprecated are strange sunlight effects, for they have the double drawback for the painter, of rarity and evanescence in nature. A stroke of lightning is not out of place where the conditions may be presumed to be more or less permanent, as in the celebrated picture of Apelles, where Alexander was represented in the character of Jupiter casting a thunderbolt, and forks of lightning proceed from his hand; or where the occurrence is essential in the composition, as in Gilbert's Slaying of Job's Sheep.[a] So in Danby's The Sixth Seal Opened, the lightning is quite appropriate, for all nature is disturbed. In Martin's Plague of Hail, and The Destruction of Pharaoh, the first a night scene, and the second a view darkened by dense black clouds, lightning is well used for lighting purposes; and in Cot's The Storm,[b] where the background is dark and no sky is visible, lightning is the only means possessed by the artist of explaining that the fear expressed by the lovers in the foreground, arises from the approaching storm. Great masters like Giorgione,[c] Rubens,[d] Poussin,[e] used a stroke of lightning on rare occasions, but took every care that it should not be conspicuous, or interfere in any way with the first view of the picture. The lightning is invariably placed in the far background, and no light is apparently reflected from it. [a] The fire of God is fallen from Heaven, and hath burned up the sheep and the servants. Job 1, 16. [b] Metropolitan Museum, N. Y. [c] Adrastus and Hypsipyle, Venice. [d] Landscape with Baucis and Philemon, Munich. [e] Jonah cast into the sea. [Illustration: PLATE 18 (See page 202) Landscape, by Hobbema (_Metropolitan Museum, N. Y._)]