14 THE POPULAR SCIENCE MONTHLY. 



in Fig. 16 ; it will be found that the tint of the gray paper scarcely 

 changes, unless the experimenter sits and stares at the combination for 

 some time. A sheet of thin white tissue-paper is now to be placed 



over the whole, when it will instantly be 

 perceived that the color of the small slip 

 has been converted by contrast into a pale 

 red. Persons seeing this illusion for the 

 first time are always much astonished. 

 Here we have an experiment showing that 

 the contrast produced by strong saturated 

 tints is much feebler than with tints which 

 are pale or mixed with white light, for, 

 by placing tissue - paper over the green 

 sheet, the color of the latter is extraor- 

 FiG. 16.— Green and Grat Papers dinarily weakened and mixed with a large 



FOK Experiment on Contrast ,• , e \ -i. ^• \.i. txi- 



(One-quarter Size). quantity oi white lig;ht. In this experiment 



it often hapi^ens that the red, which is due 

 to contrast alone, seems actually stronger than the green ground itself. 

 If, instead of using a slip of gray paper, we employ one of black, the 

 contrast is less marked, and still less with one of white. It is scarcely 

 necessary to add that, if red paper is employed instead of green, the 

 small gray slips become tinted by contrast with the complementary 

 color — i. e., greenish-blue ; the same is true with the other colors. By 

 preparing with India-ink a series of slips of gray paper, ranging from 

 pure white to black, an interesting series of observations can be made 

 on the conditions most favorable for the production of strong contrast- 

 colors. The strongest contrast vnll be produced in the case of red, 

 orange, and yellow, when the gray slip is a little darker than the color 

 on which it is placed, the reverse being true of green, blue, violet, and 

 purple ; in every case the contrast is weaker if the gray slip is much 

 lighter or much darker than the ground. We must expect, then, in 

 painting, to find that neutral gray will be more altered by pale tints of 

 red, orange, or yellow, which are slightly lighter than itself, and that 

 the gray will be less altered by these colors when differing considerably 

 from it in luminosity ; analogous conclusions with regard to green, 

 blue, violet, and purple, can also be drawn. Saturated or intense colors 

 in a painting have less effect on white or gray than colors that are 

 pale ; this was shown in the preliminary experiment when gray was 

 placed on a ground of strong color. In repeating these experiments it 

 will be noticed that the effect of contrast is stronger with green, blue, 

 and violet, than with red, orange, or yellow — that is to say, it is stronger 

 with the cold than with the warm colors. 



We must next examine the effects that are produced by contrasting 

 colors that differ in luminosity or in saturation. If the two colors are 

 identical except in the matter of saturation, it will be found that the 

 one which is more saturated will gain in intensity, while its pale rival 



