sive contrast of light blue-green is projected on the red tint and being complementary the resulting effect is a gray. If the red tint could be exactly graded to the complementary effect in the eye the resulting gray circle would be a true neutral gray. Another illustration of the same physical effect by which the complementary is induced may be shown by substituting for the tint of red a light tint of the blue-green paper retaining the full red disk as before. The same blue-green after image is now projected on to the light blue-green paper and hence a circle of more intense blue-green is produced. Thus it is seen that Chevreul's successive and mixed contrasts are both due to the same physiological effect, the only difference being in the ground on to which the after image is projected.
It probably is unnecessary to state that these experiments may be made with any color and its complementary and that red and blue-green are used here merely as an example.
Another phase of the same physical effect is seen under other conditions which may at first seem to be quite different from those described, but which on examination appear somewhat similar.
It is a well established fact that when two surfaces approximating; each other in color, as red and orange for example, are placed side by side, both are rendered less brilliant, an effect which might be reasonably expected because in order to see both the eye is naturally directed first to one and then to the other, and in each case the after image induced is a green-blue or blue-green, which being approximately complementary to both, dulls both. Or in other words, it is as though one examine for a long time a line of goods of similar colors so that the eye becomes fatigued and the color dulled. It is said that a good salesman of colored materials will endeavor to occasionally attract a customer's attention for a few moments to some other colors approximating a complementary, so that when the attention is again directed to the goods under consideration the full effect of the color may be secured.
