The separation of light and dark from all appearance of colour is possible and necessary. The artist will solve the mystery of imitation sooner by first considering light and dark independently of colour, and making himself acquainted with it in its whole extent. 852. Chiaro-scuro exhibits the substance as substance, inasmuch as light and shade inform us as to degrees of density. 853. We have here to consider the highest light, the middle tint, and the shadow, and in the last the shadow of the object itself, the shadow it casts on other objects, and the illumined shadow or reflexion. 854. The globe is well adapted for the general exemplification of the nature of chiaro-scuro, but it is not altogether sufficient. The softened unity of such complete rotundity tends to the vapoury, and in order to serve as a principle for effects of art, it should be composed of plane surfaces, so as to define the gradations more. 855. The Italians call this manner "il piazzoso;" in German it might be called "das Flächenhafte."[4] If, therefore, the sphere is a perfect example of natural chiaro-scuro, a polygon would exhibit the artist-like treatment in which all kinds of lights, half-lights, shadows, and reflexions, would be appreciable.--Note E E. 856. The bunch of grapes is recognised as a good example of a picturesque completeness in chiaro-scuro, the more so as it is fitted, from its form, to represent a principal group; but it is only available for the master who can see in it what he has the power of producing. 857. In order to make the first idea intelligible to the beginner, (for it is difficult to consider it abstractedly even in a polygon,) we may take a cube, the three sides of which that are seen represent the light, the middle tint, and the shadow in distinct order. 858. To proceed again to the chiaro-scuro of a more complicated figure, we might select the example of an open book, which presents a greater diversity. 859. We find the antique statues of the best time treated very much with reference to these effects. The parts intended to receive the light are wrought with simplicity, the portion originally in shade is, on the other hand, in more distinct surfaces to make them susceptible of a variety of reflexions; here the example of the polygon will be remembered.--Note F F. 860. The pictures of Herculaneum and the Aldobrandini marriage are examples of antique painting in the same style. 861. Modern examples may be found in single figures by Raphael, in entire works by Correggio, and also by the Flemish masters, especially Rubens. TENDENCY TO COLOUR. 862. A picture in black and white seldom makes its appearance; some works of Polidoro are examples of this kind of art. Such works, inasmuch as they can attain form and keeping, are estimable, but they have little attraction for the eye, since their very existence supposes a violent abstraction. 863.