We are somewhat surprised by, as it would appear from the general observations of De Burtin, an accidental truth which he has not elsewhere followed to its consequences. "If pictures offend against nature, and become cold by the employment of cold colours upon them, such as black, white, blue, and green, either pure or bluish, and by the omission of the glazings which the tone of the light requires, or if they become so from the natural coldness of night and of snow, _not remedied by art_, the painter ought to correct the fault in the manner I have previously hinted at." In the following remark, we can see the great defect in the colouring of Murillo's pictures, especially in his backgrounds, who appears always to have painted on a wet and dingy day. "But nothing can correct the cold of a sky concealed by the kind of clouds last mentioned, or _rendered totally invisible by mist_." He rescues the clear-obscure from the meaning commonly attached to it as light and shade. "In the literal sense, this word means nothing but the obscure which is at the same time clear." It should rather be defined to be light in shadow; but it will be difficult to establish any other sense for it than the disposition of the light and shade in a picture. The inventor of it, for practical use, was Leonardo da Vinci. Of this _chiaroscuro_ he says: "It is this, in fine, against which so many renowned Italian masters have sinned, but in which the immortal Correggio is so eminently distinguished, and which proves how they err who have named Titian the prince of colourists. For how much soever he may possess in a supreme degree very many other parts of colouring, he has so misunderstood this one in his general harmony, that his grounds are rarely in agreement with the rest of his picture, and are often all black. His _Venus_, in the Dresden gallery, and his _Ecce Homo_, in that of Vienna, two of his most renowned pictures but especially the latter, present striking proofs, among very many others, of the correctness of my opinion on this great colourist."