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♦ KNOW^LEDGE ♦ 



367 



facts, and its correctness or incorrectness will not atl'ect the 

 Talidity of the general theory set forth in this paper. 



It is supposed that every part of the retina is furnished 

 ■with three kinds of nerve-fibres. The first set is chiefly 

 stimulated by the longest ether-waves, producing the sen- 

 sation of red, the second by those of medium length, giving 

 green, the third by the shortest, giving vioht. The sen- 

 sations of yellow, blue, and orange are each produced by 

 the simultaneous stimulation of two of these sets of tiltres. 

 For instance, these ether waves which are shorter than the 

 red waves, and longer than the green waves, stimulate 

 moderately both those fibres which perceive red, and those 

 which perceive green, and give the sensation of yellow. 

 Stimulation of all these sets gives white. A perfectly pure 

 colour is never perceived, because while light-waves of any 

 given length are stronyly exciting their own special nerve- 

 fibres, they are also very weakly exciting fibres of the two 

 other kinds. The longest waves, for example, which 

 strongly stimulate the red fibres, at the same time faintly 

 stimulate the green and the violet fibres, so that the red 

 always appears mixed with a little white. 



But this faint excitement is not sufScient to cause 

 fatigue. After an object of any definite colour bus been 

 presented to the eye for an appreciable time, the fibres 

 which have been comparatively idle while their com- 

 panions have been exhausted will be fresh and eager for 

 action. 



If we look at a bright red object, and then turn our 

 eyes to a white surface, a bluish-green image will appear 

 of the same size and shape as the original object. The 

 red nerves have been tired, and only the green and violet 

 nerves are acting : so that practically only the green and 

 violet constituents of white light will be seen by that part 

 of the retina which has been exposed to the red light. 

 The colour of the image is said to be complemeiUary to that 

 of the object, because their mixture would form white 

 Ught 



We now have data on which to explain both the pleasure 

 in isolated colours and the pleasure in contrasted colours. 

 A single pure, bri;»ht colour pleases for a time, because it 

 stimulates powerfully, and yet permits a partial rest ; but 

 a contrast of colours gives a greater and more lasting iilea- 

 sure, since it occasions easy and varied action. When 

 the red waves, for instance, have fatigued the delicate 

 structures which receive them, the complementary bluish- 

 green waves are welcomed as a relief and diversion. The 

 red-perceiving fibres rest and undergo repair while the 

 others are exercised. It may be oVjected that a red and a 

 bluish-green object, placed in juxtaposition, do not aiTect 

 the same part of the retina. The eye, however, is never 

 kept perfectly steady, but ceasele.'fcly wanders from point to 

 point, so that the pleasure derived from chromatic com- 

 bination is generally due to what is known as Successive 

 Contrast. 



Simultaneous contrast, or the efifect of one colour in 

 heightening or modifying another, when both are seen at 

 the same instant, pioduces much the same results, but 

 seems to be attributable to a different cause. Here we are 

 concerned with dec-ption of the judgment rather than with 

 retinal fatigue, since pale hues, differing little, produce a 

 greater effect upon each other than intense hues, differing 

 much. It seems likely that we unconsciously accept the 

 colour of the larger mass as our standard, and accept it the 

 more readily as it approaches nearer to white. A strip of 

 grey paper on a sheet of pale green paper will look reddish, 

 because it reflects more red light than is reflected by the 

 green sheet. It should be remembered that white is merely 

 a relative term, and that as each set of light-waves stimu- 

 lates to some extent all three sets of nerves, every colour 



which is seen diti'ers from white not in kind, but in degree. 

 All ordinary colours, that is, arc gr.ides of white. Any 

 pleasure given by simultaneous contrast must obviously be 

 mental rather than purely sensuous. 



The explauiition of colour discord seems a little diflicult. 

 Mr. Grant Allen suggests* that while tho red-perceiving 

 fibres are rested by green, they are fatigued by orange or 

 yellow, which continue the stimulation, though in a some- 

 what slighter degree,and thus makefresh dcuiandsupontheir 

 wearied energies. Continued contemplation of the same 

 colour overworks the nerves which perceive it, and lessens 

 its apparent brilliancj-. The same is true, in a less degree, 

 of continued contemplation of colours standing near each 

 other in the chromatic scale — as, for instance, red and 

 orange, "i'et the sufficiency of this explanation seems at 

 least doubtful. The discomfort created by discord cer- 

 tainly is not very similar to our feeling of fatigue, when 

 we gaze long at an uninterrupted mass of one colour. 

 Mr. Sully, in a criticism of " Physiological iEsthetics,"t 

 points this out, and urgt s that the weariness and consequent 

 distaste should on this theory be tjrealcsl when the colour 

 is monotonous. Mr. Allen replies that our eyes seek the 

 boundary of each colour, and that thus they keep travelling 

 to and fro between the two, instead of escaping into 

 black, white, or neutral tint, as they might were there but 

 one hue, with an uncoloured boundary. It may still be 

 asked, — When the eyes have reached the limit of the red, 

 why should they not go straight on to the opposite 

 limit of the orange 1 They would be less fatigued by 

 thus travelling across a small patch of red and a small 

 patch of orange than by journeying from end to end 

 of a uniform patch of red large enough to cover both 

 the small patch of red and the small patch of orange. If, 

 on the other hand, they travel back again, they will not be 

 more tired by a double journey across the small red patch, 

 than by a single journey across the large red patch. 

 Besides, if the feeling of discord arises from this species of 

 fatigue, a strong eye, able to bear much stimulation, ought 

 to sufTer less from discord than a delicate eye ; but we find 

 that the eye is affected in proportion to its cultivation, not 

 in proportion to its weakness. A gradation from red to 

 orange is absolutely pleasant ; and yet, on Mr. Allen's 

 hypothesis it should be only one degree less painful than 

 monotony. 



Discord of colour probably gives a negative rather than a 

 positive discomfort ; a disappointment rather than a pain. 

 We have a certain variety of colour, but we do not get the 

 treat which we expected, and which we should have received 

 from those combinations known as harmonious. Instead 

 of appearing Iriyhter by contrast, the tints actually appear 

 duller. Cousequeiitly, we are dissatisfied. The effect is 

 much like that of a false rhyme. 



However, there may be some physical disturbance as 

 well, and I venture to suggest a theory. The fibres which 

 have been excited by red are still excited by the neigh- 

 bouring patch of orange ; but they are now called upon to 

 respond to light waves of a slightly different length. 

 There may be some discomfort attendant on the sudden 

 necessity of accommodation to this new stimulus, while 

 the vibrations due to the old stimulus still persist. This 

 discomfort will last till the red vibrations have ceased, and 

 the fibres are tuned for orange, and will recur when they 

 have again to be tuned for red. It will be remembered 

 that smooih'iiess or continuity is one of the essential con- 

 ditions of easy action. 



In yradation this condition is fulfilled. The transition 

 from red to orange is made almost imperceptibly, giving 



* " Physiological .(Esthetics," p. 167. t Hind. July, 1879. 



