1835.] Accidental and Complementary Colours. 293 



although I do not think the difference is such as to autho- 

 rize me to employ the term accidental to the second image, 

 and besides, white is produced where the two images overlap. 

 But granting, for a moment, that such is the case, and 

 the apparatus being arranged as just mentioned, let the face 

 be regarded, its prominent parts, and the red and green are 

 so distributed as to give the visage, or rather, visages, for 

 there are two reflections, a most hideous appearance. But 

 this experiment, as also that with the finger, is not a fair 

 one, on account of the flesh colour ; let us then hold a nar- 

 row strip of white paper before the glasses, and, of the two 

 reflections, the green is certainly the more intense. It must > 

 not, however, be asserted that the eye is insensible to the 

 two colours at the same moment, for, indeed, I find, that 

 from the moment the strip is properly raised, until the end 

 of the observation, the two colours are seen under the same 

 precise circumstances. If to this it should again be objected, 

 that the preparation of the eye is the act of " less than a 

 second,*' I answer that the objection embraces a point of 

 time so minute, that it amounts to nothing ; that I have so 

 arranged the glasses and strip of paper as to make the 

 observation at any time, and when my eye has been long 

 disengaged from the contemplation of objects of a green 

 hue, as would in any way render the accuracy of the expe- 

 riment questionable, and the results never vary. I have 

 very much to say on this subject, but having already carried 

 this paper to no small length, and being anxious to make a 

 few observations on the other propositions, I must dismiss 

 the one now under discussion, by stating that, if the red 

 reflection of the narrow strip of paper, as mentioned above, 

 be admitted by M. Plateau, to be an accidental colour, and 

 and that the two reflections can be seen at the same moment, 

 (and, admitting one, he must admit the other), then his 

 third proposition is disproved. 



10. The consideration of the -opposition spoken of by 

 M. Plateau, [4.] of black resulting from the contemplation 

 of white, will, at present, lead me too far, but I shall here- 

 after consider this point particularly, and need only state 



beginning of July. I also beg to take this opportunity of thanking P. C. for his 

 kind mention of me ; and, though I may object to many of his conclusions, still I 

 hope that nothing will interfere to prevent the prosecution of his interesting in- 

 quiry, or to disturb that harmony of feeling so necessary to scientific inquirers, 

 even though they differ. 



