IN a previous chapter we have studied the changes which colored surfaces experience when viewed under various kinds of illumination, or when modified in appearance by the admixture of more or less white or colored light. The appearance which a colored surface presents to us can, however, be altered very materially, by a method which is quite different from any of those that have thus far been mentioned: we can actually change color to a considerable extent without at all meddling with it directly, it being for this purpose only necessary to alter the color which lies adjacent to it. The truth of this can be seen by a very simple experiment: If we cut out of a sheet of red paper two square pieces, about an inch in size, and then place one of them on
a sheet of red, the other on a sheet of green paper, as indicated in Fig. 1, it will be found that the red square on the red paper will not appear nearly so brilliant and saturated in color as that placed on the green ground; hence the observer will be disposed to doubt whether the two
- From the advance-sheets of a work on "Chromatics, with Applications to Art and Industry."