337. When, in this point of view, we examine the masterpieces of Vandyke, and trace the beauty of their effect to the simplicity of the means which produce it,—when we consider the elegance of their attitudes, which always appear natural, the taste which presided over the selection of all the accessories, we are struck with admiration of the genius of the artist, who has not had recourse to those means, so much abused at the present day, of attracting attention, either by giving to the most vulgar person an heroic attitude, to the most commonplace physiognomy pretension to profound thought, or by seeking extraordinary effects of light, such as filling the figure with a strong light, while the rest of the composition is in shade. 338. These reflections indicate the course which an historical painter must take, when he would particularly fix the attention upon the physiognomy of the persons in a remarkable scene. The more he employs allied scales, the more care he must take to select such as do not lose too much by their mutual juxtaposition. 339. There is another important direction to give, which is to avoid as much as possible the same kind of images on different objects; thus figures clothed in draperies with large flower patterns, in a room where the carpet and porcelain vases repeat the same images, are never free from objection, for it is troublesome to the eye to distinguish those parts of the picture which the similarity of ornaments tends to confound. Upon the same principle, the painter must generally avoid placing beside the faithful copy of a model the copy of an imitation which repeats this model. For example, when, he paints a vase of flowers, the artist produces most effect, other things being equal, in painting a vase of grey or white porcelain, instead of a vase upon which a profusion of similar objects are its ornaments. 340. When it is required that a certain colour shall predominate in a composition, or to speak more correctly, when the scene is illuminated by a coloured light, shed over every object, we must not only take simultaneous contrast into consideration, but also the modification which results from the mixture of colours (172), comprising the recomposition of white light by means of a proper proportion of the differently coloured elementary rays. 341. We must here attentively study the article which treats of the principal cases of the modifications of light resulting from coloured rays falling upon bodies of various colours (261, _et seq._), when, although the coloured light chosen imparts value to certain colours of the objects upon which it falls, it also impoverishes and even neutralizes others. Consequently, in employing any predominant colour, we must renounce the advantages of others, or the effect produced will be false. For example: if orange colour predominates, for the colouring to be true it must necessarily follow—