;50 a S. Peirce—Note on the Sensation of Colors. 



Feb. 6. White -0041 +-0001 



Red, just before C -0046 +'0006 



Chrome-yellow, A 2 -0032 - -0008 



Feb. 1. Red, just before C -0040 ±'0000 



Staat's emerald green -0046 +-0006 



Carmine, B -0044 +-0004 



Chrome-yellow, A 1 -0037 — "0003 



Purple, Hoffmann's violet RRR.. -0033 - -0007 



Feb. 13. Red, just before C -0048 +-0008 



Green, complementary to carmine "0034 — -0006 



Blue violet, No. 2. . -0048 -+--0008 



Yellow, A 1, mixed with black .. -0032 - -0008 



Mean "0040 



, the method of observing was chang 



and I obtain 



Feb. 14. White window-shade, ill. by sun . -0030 — 



Brown -oo30 - 



Greenish sky-blue -omi -p 



"""h purple -0028 — ' 



•0032 db 



fery reddish purple 



iTellow orange 



Feb. 15. "Fundamental green of M tiller". 

 Vermilion, half between C and D 



Violet 



Yellow ."" 



0030 --0002 



±•0000 

 + •0002 



= •00032, r'=-00019, —=0'6 

 and from the weighted mean, - = -96, so that it appears from 

 these experiments that the photometric susceptibility of the eye 

 is the same for all colors. The result is, however, uncertain, 

 because it may be that R is chiefly due to other sources of error 

 than the limitation of sensibility ; still, the experiments show as 

 small a value of R as is usually obtained. I shall endeavor, 

 by further observations, to obtain a conclusive result. 



A further consequence of our hypotheses will be reached by 

 aiflerentiatmg the expression for a light-sensation. We have 



d(Iloga ; .t + Jlo g2/ . iH -Klo g2 .A ; )=id a; .K-f.idy.Ji+^.K^. 



Now, as x, y and z all exceed unity, the differential is greater the 



