complementary hue. As black is really a dark gray, we should expect to find it also assuming, to some extent, a color complementary to that of the ground, and this is indeed the case, though the effect is not quite so marked as with a gray of medium depth. Chevreul, in his great work on the simultaneous contrast of colors, relates an anecdote which illustrates the matter now under consideration: Plain red, violet-blue, and blue woven stuffs were given by certain dealers to manufacturers, with the request that they should ornament them with black patterns. When the goods were returned the dealers complained that the patterns were not black, maintaining that those traced on the red stuffs were green; on the violet, dark greenish-yellow; and on the blue, copper-colored. Chevreul covered the grounds with white papers in such a manner as to expose only the patterns, when it was found that their color was truly black, the effects which had been observed being entirely due to contrast. The remedy in such cases is not to employ pure black, but to give it a tint like that of the colored ground, taking care to make it just strong enough to balance the hue generated by contrast. If we substitute a white pattern for the black, something of this same effect can often be observed, but it is less marked than with gray or black. In cases like those now under consideration, the contrast is stronger when the colored surface is bright and intense or saturated in hue. The effect is also increased by entirely surrounding the second color with the first; the circumscribing color ought also to be considerably larger than its companion. When these conditions are observed, the effect of contrast is generally noticeable only on the smaller surface,
Fig. 9.—Arrangement to show the Effects of Simultaneous Contrast (One-Half Size).
the larger one being scarcely affected. When, on the other hand, the two colored surfaces are about equal in extent, then both suffer change. If it is desired to produce a strong effect of contrast, the colored surfaces must be placed as near each other as possible. This is beautifully illustrated in one of the methods employed by Chevreul in studying the laws of contrast. Two colored strips were placed side by
