The best Claude in the Gallery, for it is a perfect example of his chief merit--the painting of quiet skies. Constable, in one of his lectures, refers to it as "probably the finest picture of _middle-tint_ in the world. The sun is rising through a thin mist, which, like the effect of a gauze blind in a room, diffuses the light equally. There are no large dark masses, there is no evasion in any part of this admirable work, every object is fairly painted in a firm style of execution, yet in no other picture have I seen the evanescent character of light so well expressed" (Leslie's _Life of Constable_, p. 338). "The effect of the breeze upon the water and upon the trees," says Ottley, "and the freshness of the morning atmosphere, in this picture, are expressed with a closeness of imitation bordering on illusion" (_Descriptive Catalogue of the National Gallery_, 1826, p. 42). As for the subject: St. Ursula, a beautiful and gifted Sicilian princess, was sought in marriage by a prince of Britain; but having already dedicated herself to Christ, she made a condition that before her marriage, she, with eleven thousand attendant virgins, should be permitted for the space of three years to visit the shrines of the Saints. This being permitted, the maidens started on a miraculous voyage. Guided by angels they proceeded as far as Rome, where pagans having plotted their death, on their further journey to Cologne they were martyred by the barbarians besieging that city. Here in the picture they are represented as embarking. 31. THE SACRIFICE OF ISAAC. _Gaspard Poussin_ (French: 1613-1675).