892 OP SENSATION, AND THE ORGANS OP THE SENSES. 



spot on a white ground, and be then suddenly turned so as to rest upon the white 

 surface, we see a spectrum of a green color. The same explanation applies to the 

 curious phenomenon of colored shadows. It may not unfrequently be observed 

 at sunset, that when the light of the sun acquires a bright orange color from the 

 clouds through which it passes, the shadows cast by it have a blue tint. Again, 

 in a room with red curtains, the light which passes through these produces green 

 shadows. In both instances, a strong impression of one color is made on the 

 general surface of the retina; and at any particular spots, therefore, at which 

 the light is colorless but very faint, that color is not perceived, its complement 

 only being visible. The correctness of this explanation is proved by the fact 

 that, if the shadow be viewed through a tube, in such a manner that the 

 colored ground is excluded, it seems like an ordinary shadow. It is not unlikely 

 that, as Mliller suggests, the predominant action of one color on the retina 

 disturbs (as it were) the equilibrium of its condition, and excites in it a tend- 

 ency to the development of a state corresponding to that which is produced by 

 the impression of the complementary color; for the latter is perceived, according 

 to him, even where it does not exist, as when the eye, after receiving a strong 

 impression from a colored spot, and directed upon a completely dark surface 

 or into a dark cavity, still perceives the spectrum. This change, indeed, extends 

 beyond the spot on which the impression is made; for, as is well known to 

 Artists, the sensory impression produced by any color is greatly affected by 

 neighboring hues. Thus, if four strips of colored paper, or any other fabric, 

 A, B, c, D two of them, A, B, of one color (e. g. red), and the other two, c, D, 

 of some different color (e. g. blue) be laid side by side at intervals of about 

 half an inch, the hues of the two central strips B, c, will be decidedly modified 

 by each other's proximity, each approximating to the hue of the complement- 

 ary color of the other; so that, instead of 



A B CD 



red red . blue blue, 



we shall see 



A B CD 



red orange red greenish blue blue. 



Upon these properties of the eye are founded the laws of harmonious color- 

 ing, which have an obvious analogy with those of musical harmony. All com- 

 plementary colors have an agreeable effect, when judiciously disposed in 

 combination ; and all bright colors, which are not complementary, have a dis- 

 agreeable effect, if they are predominant : this is especially the case in regard to 

 the simple colors, strong combinations of any two of which, without any color 

 that is complementary to either of them, are extremely offensive. Painters 

 who are ignorant of these laws, introduce a large quantity of dull gray into 

 their pictures, in order to diminish the glaring effects which they would other- 

 wise produce; but this benefit is obtained by a sacrifice of the vividness and force, 

 which may be secured in combination with the richest harmony, by a proper 

 attention to physiological principles. 



894. Some persons, who can perfectly distinguish forms, are deficient, through 

 some original peculiarity in the constitution of the retina, in the power of dis- 

 criminating colors. This is most commonly seen in regard to the complementary 

 colors, especially red and green; such persons not being able to perceive cherries 



or colorless light, when mixed with the original. As red, blue, and yellow are the primary 

 or elementary colors, red is the complement of green (which is composed of yellow and 

 blue] ; blue is the complement of orange (red and yellow) ; and yellow of purple (red and 

 blue) ; and vice versa in all instances. 



