From among the facts I could quote to support this opinion, I shall select the following. There was a deep rose-red curtain, the centre representing a large bouquet of flowers of various colours, framed, as it were, in a garland of white roses. The artist had painted the model under the idea of executing this garland with silver thread; but this metal being objectionable, on account of its tarnishing by various exhalations, preference was given to white and grey silk, imitating the tones yielded by a silver object in relief. An experiment showed that it could not be attained by these means, because the contrast of the ground made all the half-tints appear _green-grey_, and these in their turn made the lights appear rusty-pink, in consequence of the greenish colour of their contrast. This annoyance being communicated to me, I advised M. Deyrolle, in reproducing the model, to make use of only three light tones of the rose scale in silk, and a white linen thread. By this means I expected that the complementary of the ground, neutralizing the rose, would produce a greyish half-tint, well adapted to set off the white. The result was such as I had foreseen. A second copy, made with a mixture of the light tones of the pure rose scale, slightly broken, gave an image less white, less _silvery_ than the preceding; or, in other terms, appearing a little greenish when compared with the first, and more harmonious. It resembled the effect obtained with rose-red under lace or tulle, which permits little of the ground to be seen. This example indicates the means of executing white designs upon any kind of ground. _Savonnerie Carpets._ 628. Carpets are larger than the tapestries for hangings; on the other hand, being liable from their position to be soiled by the feet, and to receive furniture on some part, they are in a less favourable condition than tapestries for being distinctly seen. This, then, is one reason why we should choose models, of design and colour adapted to the circumstances necessitated by custom, and in harmony with what is around. _Mosaics._ 629. Mosaics being composed of minute prisms, and of materials susceptible of polish, we can rigorously copy very small objects, and, consequently, approach much nearer to painting in chiaro-’scuro than by employing threads. But to arrive at this result, without being unfaithful to the peculiarity of the art, the materials must be sufficiently solid, and joined together so intimately as to resist the agencies which would destroy a painting; for if this end be not attained, we cannot see the use of copying a picture in mosaic. So that to justify the production of such works, we must make sure that, in the situations in which they are placed, they will resist the agents which would destroy the works of the painter. _Windows of Coloured Glass._