Fragonard, whose picture of Coresus and Callirrhoe made a great sensation in its day, and still attracts some small share of attention in the French school, was not a favourite with Diderot. The Callirrhoe inspired an elaborate but not very felicitous criticism. Then the painter changed his style in the direction of Boucher, and as far away as possible from _l'honnete_ and _le beau moral_, and Diderot turned away from him; at last describing an oval picture representing groups of children in heaven as "_une belle et grande omelette d'enfants_," heads, legs, thighs, arms, bodies, all interlaced together among yellowish clouds--"_bien omelette, bein douillette, bein jaune, et bien brulee_."[41] [41] xi. 296. For the Callirrhoe, see x. 397. On the whole, we cannot wonder either that painters hold literary talk about their difficult and complex art so cheap, or that the lay public prizes it so much above its intrinsic worth. It helps the sluggish imagination and dull sight of the one, while it is apt to pass ignorantly over both the true difficulties and the true successes of the other. Diderot, unlike most of those who have come after him, had carefully studied the conditions prescribed to the painter by the material in which he works. Although he was a master of the literary criticism of art, he had artists among his intimate companions, and was too eager for knowledge not to wring from them the secrets of technique, just as he extorted from weavers and dyers the secrets of their processes and instruments. He makes no ostentatious display of this special knowledge, yet it is present, giving a firmness and accuracy to what would otherwise be too like mere arbitrary lyrics suggested by a painting, and not really dealing with it. His special gift was the transformation of scientific criticism into something with the charm of literature. Take, for instance, a picture by Vien: