The glide of the muddy streams of the melancholy Tiber and Anio through the Campagna is impressive in itself, but altogether ceases to be so when we disturb their stillness of motion by a weir, adorn their neglected flow with a handsome bridge, and cover their solitary surface with punts, nets, and fishermen" (_Modern Painters_, vol i., preface to second edition, pp. xxxvi.-xxxix.) Take next the "ideas of truth" in the picture--the perception, that is to say, of faithfulness in a statement of facts by the thing produced. And first (1) for truth of _colour_. "Can it be seriously supposed that those murky browns and melancholy greens are representative of the tints of leaves under full noonday sun? I know that you cannot help looking upon all these pictures as pieces of dark relief against a light wholly proceeding from the distances; but they are nothing of the kind, they are noon and morning effects with full lateral light. Be so kind as to match the colour of a leaf in the sun (the darkest you like) as nearly as you can, and bring your matched colour and set it beside one of these groups of trees, and take a blade of common grass, and set it beside any part of the fullest light of their foregrounds, and then talk about the truth of colour of the old masters!" (_Modern Painters_, vol. i. pt. ii. sec. ii. ch. ii. § 5). (2) Next for truth of _chiaroscuro_. Claude neglects that distinctness of shadow which is the chief means of expressing vividness of light. Thus "the trunks of the trees between the water-wheel and the white figure of the middle distance, are dark and visible; but their shadows are scarcely discernible on the ground, and are quite vague and lost in the building. In nature, every bit of the shadow, both on the ground and building, would have been defined and conspicuous; while the trunks themselves would have been faint, confused, and indistinguishable, in their illumined parts,[48] from the grass or distance" (_ibid._, ch. iii. § 4). (3) Thirdly, for truth of _space_. In nature everything is indistinct, but nothing vacant. But look at the city on the right bank of the river:--