230 ON ACCIDENTAL OR SUBJECTIVE COLORS 



been illuminated with a colored light, with orange for instance, and white light 

 he made to fall on a shadow projected in that colored light, the orange ray of 

 the white light will not be sensible to the eye, because it is common to the ray 

 and to the ground ; we shall perceive, therefore, only the united sensation of the 

 other rays contained in the pencil ; these will produce a greenish white tint com- 

 plementary to the orange, and with this the shadow will appear to be invested. 



We are thus led to- distinguish three orders of subjective colors : the first 

 would have its cause in the successive vibrations of the retina ; the second would 

 be explained by irradiation, or by the participation of several portions of the 

 retina vibrating simultaneously under the impression of a first excitation ; the 

 third would find its reason in contrast, or the elimination of the colors common 

 to the two rays which act at the same time on the organ of vision. 



We make no pretensions, however, to giving a definitive solution of this diffi- 

 cult problem, and pronouncing in the last resort between two physicists so dis- 

 tinguished as MM. Plateau and Fechner. Divided in a theoretical point of 

 view, they have been, alas, too closely associated in a common misfortune. 

 Victims of the experiments which they have pursued with excessive ardor, in 

 the highly laudable but hazardous attempt to elucidate the natui-e of subjective 

 or accidental colors, both have been smitten with blindness; Belgium and Ger- 

 many have both been called upon to mourn the incapacity inflicted by that cruel 

 infirmity on these noble martyrs of science. M. Fechner, after several years of 

 suffering, has happily recovered his sight as if by miracle. It was our fortune 

 to witness the restoration of the indefatigable physicist of Leipsig; with how- 

 much joy should we learn the recovery of the gifted and laborious author of the 

 admirable memoir on irradiation — a memoir which we propose presently to an- 

 alyze, in order more clearly to illustrate what we have said respecting subjective 

 colors. 



Researches of M. Chevreul on the laws of simultaneous contrast. — The pre- 

 ceding dissertation comprises all that is essential in the learned researches of 

 ]M. Chevreul ; but we might reasonably be accused of injustice did we not give 

 a summary account of the labors of our eminent compatriot, remarkable as they 

 are in a practical point of view. M. Chevreul was the first who clearly stated 

 this general law : in a case in which the eye sees at the same tinae two colors 

 which are in contact with each other, it sees them as unlike as is possible; these 

 mutual modifications of colors are not limited to the case in which the colored 

 zones thus influenced are contiguous to one another, for we still perceive tbem 

 Avhen these zones are separated. He has clearly established that whenever the 

 eye sees simultaneously two colored objects, all that is analogous in the sensa- 

 tion of the two colors undergoes such an abatement that all that is diff'erent 

 becomes more sensible in the simultaneous impression of those two colors on the 

 retina. The experimental demonstration of these two propositions essentially 

 distinguishes his observations from those which had been made before. The law 

 of these modifications being once known enables us to foresee the changes which 

 two given colors, when we know the complementary colors of each of them and 

 their relative tone, will undergo by juxtaposition ; for these changes must be the 

 result of the complementary of the one being added to the other ; and if the two 

 colors have not the same height of tone, that which is deeper will apj)ear more 

 so, and the other will appear lighter than it is ; provided, however, that this last 

 effect be not destroyed by the former. After so accurate and complete a study 

 of the influence of colors, M. Chevreul might proceed with confidence to the de- 

 tails of application. He teaches by turns the difficult art of assorting colored 

 threads in such a way as to faithfully reproduce the tints of a painting ; of giving 

 to paintings, to tapestry, to carpets the highest perfection of coloring ; of stamping 

 designs on cloth and paper ; of adapting the accessories of furniture ; of giving 

 greater brilliancy to the colored windows of cathedrals ; of distributing flowers 

 in gardens ; of choosing and distributing the colors of raiment ; of judging more 



