190 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



shown him that it is impossible to adopt the principle that 

 the accidental or subjective color observed when Ave cease 

 contemplating a bright object has always a tint comple- 

 mentary to that of the object itself. This subjective tint 

 depends upon the eyes of the observer; and the cases where 

 the principle is satisfactory constitute rather the exception 

 than the rule, at least so far as concerns bine and yellow. 

 Therefore, in a recent communication to the Belgium Acad- 

 emy, he says that he must continue to maintain the general 

 theory, with reference to accidental colors, that he published 

 forty years ago, and which he thinks has not been sufficient- 

 ly considered by recent authors. His theory consists essen- 

 tially in the following propositions: First, during the con- 

 templation of a colored object, the retina exerts an increas- 

 ing reaction against the action of the light which foils upon 

 it, and tends to throw itself into an opposite state. Conse- 

 quently, after the disappearance of the object, it takes spon- 

 taneously, or, as it were, by inertia, its opposite state, whence 

 results the sensation of the accidental or subjective color. 

 Then it comes to repose by a sort of oscillation, in virtue of 

 which it passes alternately from the accidental to the com- 

 plementary tint, and vice versa. The physiological condi- 

 tion of the retina after the prolonged action of light is very 

 nearly like the state of a body which, drawn from a position 

 of stable equilibrium, then abandoned to itself, returns to 

 repose by a series of decreasing oscillations. Second, anal- 

 ogous phenomena take place in reference to space ; while 

 one portion of the retina is submitted to the action of a col- 

 ored light, the surrounding portions throw themselves into 

 the opposite state ; whence results, all around the colored 

 image, an aureole of the accidental colors, and, finally, be- 

 yond this aureole there is a tendency toward a manifesta- 

 tion of a cloudiness of the same tint as that of the primitive 

 image. Such a state of the retina can but be compared to 

 that of *a vibrating surface, in which the nodal lines are sep- 

 arated by vibrations in opposite directions. This theory 

 has, he says, been adopted in France, but is quite rejected 

 by the German and English physicists. He has been so oc- 

 cupied by his extensive researches into the phenomena of 

 thin liquid films that he has not until lately found time to 

 defend his theory. In the memoir in question he adduces 



