the diagram of the chromatic circle more or less elaborately constructed. These diagrams, if intended to exhibit the contrasts produced by the action and re-action of the retina, have one common defect. The opposite colours are made equal in intensity; whereas the complemental colour pictured on the retina is always less vivid, and always darker or lighter than the original colour. This variety undoubtedly accords more with harmonious effects in painting.
The opposition of two pure hues of equal intensity, differing only in the abstract quality of colour, would immediately be pronounced crude and inharmonious. It would not, however, be strictly correct to say that such a contrast is too violent; on the contrary, it appears the contrast is not carried far enough, for though differing in colour, the two hues may be exactly similar in purity and intensity. Complete contrast, on the other hand, supposes dissimilarity in all respects.
In addition to the mere difference of hue, the eye, it seems, requires difference in the lightness or darkness of the hue. The spectrum of a colour relieved as a dark on a light ground, is a light colour on a dark ground, and vice versâ. Thus, if we look at a bright red wafer on the whitest surface, the complemental image will be still lighter than the white surface; if the same wafer is placed on a black surface, the complemental image will be still darker. The colour of both these spectra may be called greenish, but it is evident that a colour must be scarcely