INFLUENCE OF A SURROUNDING COLOUR UPON ONE COLOUR WHEN COMPARED WITH ANOTHER. 603. Since the contrast of colours which are not analogous, tends to improve and purify them, it is evident that whenever we would exercise a correct judgment upon the beauty of colours, after comparing them with the colours of objects analogous to the first, we must take into account the kind of work, and the manner in which they are juxtaposed, if the objects compared are not the exact representation of the same subject. For, other things being equal, the same colours not blended, and which are not sufficiently analogous to injure each other, will certainly appear more beautiful disposed in contiguous bands than if each were seen on a ground which consisted of it exclusively, and which consequently produced only a single impression of colour upon the eye. Colours forming palms like those of Oriental shawls or patterns, as of Turkey carpets, produce a much greater effect than if they were shaded or blended, as they generally are in paintings. Consequently, for example, in comparing a stripe of crimson in a Cashmere shawl of various stripes with the crimson of a French shawl, we must destroy the contrast of colours by placing around it a piece of grey or white paper, cut out so as to allow this stripe only to be seen, when the parts compared will be submitted to the same influence from the surrounding objects. 604. So, when we compare the colours of old tapestries, pictures, &c., with colours recently dyed or painted. Time acts very unequally, not only on the different kinds of colours of dyed stuffs, but also upon the tones of the same scale. Thus, the deep tones of certain scales,—those of violet, for example,—fade, while the deep blues of the indigo-blue scale, the deep tones of madder, kermes, cochineal, are permanent. Also, the light tones of the same scale fade during a time which has no sensible effect in altering its deep tones. Whence the colours which have most resisted the destructive action of time, being more isolated from each other, as well as deeper and less blended, appear to have more brilliancy. There are many pigments, as most of the lakes, which are in the same condition as compared with ultramarine, the oxides of iron, the blacks, &c. _On the Effect of Contrast upon the Browns and the Lights of most of the Scales of Wool and Silk employed in Tapestry and Carpets._