250. Some remarks appear to me also necessary to prevent false deductions from the above propositions. In the preceding examples, the colours, including white, black, and grey, are supposed to occupy an equal extent of surface, and to be placed at equal distances apart, for without these conditions the results will be different; for example, I have preferred the assortment white, red, white, yellow, white, to the assortment white, red, yellow, white. There are some cases in which the latter is preferable to the former, as in the arrangement of flowers in gardens, especially yellow and rose flowers, which present less coloured surface than the white flowers with which they are associated. 251. I have spoken of the good effects of black and green separated, and I may add that green designs upon a black ground are also agreeable; but it does not follow that black lace upon a green stuff will have a good effect, at least on the optical quality of black, for this acquires a rusty tint, which resembles a faded colour. 252. The more colours are opposed, the easier it is to assort them; because they do not experience by their mutual juxtaposition, any modification which renders them disagreeable, as generally happens to colours which are very nearly alike. Must we then conclude that with two colours which have in this case been indicated to an artist to be employed, with some liberty to modify them, he should endeavour to increase the effect of contrast rather than that of analogy? Certainly not; for frequently the latter is preferable to the former. For example:—Take orange-red and a pure red, instead of increasing the yellow in the orange-red, or of giving a violet hue to the red, it sometimes will be preferable to incline towards the harmony of scale or of hue, by endeavouring to make the orange one of the light tones of a scale whose red will be brown. 253. In conformity with this manner of observing, when we would avoid the bad effect of two adjacent colours by white, black, or grey, we must see whether, instead of a harmony of contrast, it may not be better to obtain the harmony of analogy. 254. Finally, when we bring into combination not normal grey, but a coloured grey, we are always sure of obtaining an effective harmony of contrast by taking a grey coloured with a complementary of that opposed to it. Thus an orange-grey or carmelite-brown or maroon has a good effect with light blue. FIRST DIVISION.—IMITATION OF COLOURED OBJECTS WITH COLOURED MATERIALS IN A STATE OF INFINITE DIVISION. INTRODUCTION. 255. Coloured materials, such as Prussian blue, chrome-yellow, vermilion, &c., are infinitely divided, so to speak, either when ground pure, or mixed with a white material, in a gummy or oily liquid. The reproduction of the images of coloured objects with these pigments is called the _Art of Painting_.