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THE POPULAR SCIENCE MONTHLY.
leads to: The two colors are to be moved farther apart; they are already situated on the opposite extremities of a diameter of the circle, and, if they are to recede still farther from each other, they can accomplish this in no other way than by moving outside of the circumference of the circle; but this corresponds, as explained in the previous chapter, to an increase of saturation. If the experiments indicated in the previous table are carefully repeated, it will be found that all the pairs of colors there enumerated are not equally affected by contrast. The changes of tint are greatest with the colors which are situated nearest to each other in the chromatic circle, and much less with those at a distance. Thus both red and yellow are much changed by contrast, the red becoming purplish, the yellow greenish, while red with cyan-blue, or blue, is much less affected in the matter of displacement or change of hue. On the other hand, the colors which are distant from each other in the chromatic circle, while suffering but slight changes. in hue, are made to appear more brilliant and saturated—that is, they are virtually moved somewhat outside of the circle, the maximum effect taking place with colors which are complementary. Colors which are identical are affected by contrast in exactly the opposite way from those which are complementary—that is, they are made to appear duller and less saturated. The author finds that these and other effects of contrast can be studied with great advantage by the aid of two identical chromatic circles laid down on paper. One set of these lines should be traced on a sheet of transparent paper, which is afterward to be placed over the companion-circle. The use of these circles will best be made evident with the aid of an example: Let us suppose that we wish to ascertain with their aid the effect produced by red, as far as contrast goes, on all the other colors, and also on red itself. We place the transparent circle on its companion so that the two drawings may coincide in position, and we then move the upper circle along the diameter joining the red and green-blue some little distance, so that the two circles no longer have the same common centre. We then transfer the points marked red, orange, yellow, etc., on the upper circle, by pricking with a pin through to the lower circle; these pin-marks on the lower circle will indicate the changes produced on all the colors by competition with red. Fig. 11 gives the result. The dotted circle with the crosses represents the new positions of the different colors when contrasted with red. If we examine it we find that red, when contrasted with greenish-blue, causes this last color to move away from the centre of the circle in a straight line; hence, as the new point is on the same diameter, but farther from the centre, we know that the greenish-blue is not made more or less blue or green, but is simply caused to appear more saturated or brilliant. The new point for the red lies also on the same diameter, but is nearer to the centre of the circle; that is, the color remains red, but appears duller or less saturated. Experience confirms this: if a considerable number of pieces of red cloth are ex-