Intelligence and Miscellaneous Articles. 22 3 



well chosen. The blue sector extinguishes the yellow of the orange 

 and forms white ; the red alone remains. The measure of the two 

 resulting sensations is given by the angles of the red and white 

 sectors. I found 



140° orange +220° blue =28]° red +56° white. 



All the colours of the circle have been thus studied with respect to 

 two pairs of complementary colours — yellow and blue, red and the 

 fourth green (the first three because they are the primary colours 

 of artists ; the last serves as the auxiliary colour). 



The chromatic circle was thus found to be divided into four sec- 

 tions : — 



from the blue to the red, extinguishing 



The blue was measured -j _ 



the blue bv the yellow. 

 1 he red was measured < - ,-, ■/. ,, J ■., ,. . ,. 



from the red to the yellow, extinguishing 



[ the yellow by some blue. 



{from the red to the yellow, extinguishing 

 the red by the fourth green. 

 from the yellow to the fourth green, ex- 

 tinguishing the green by red. 

 {from the yellow to the fourth green, ex- 

 tinguishing the yellow by blue. 

 from the fourth green to the blue, extin- 

 guishing the blue by the yellow. 

 f from the fourth green to the blue, ex- 

 tinguishing the green by the red. 

 from the blue to the red, extinguishing 

 [ the red by the fourth green. 

 The following are the results obtained* : — 



1. The line which represents the proportion of the extreme sen- 

 sations in the intermediate colours is a straight line: therefore the 

 intermediate colours are, to the eye, rigorously equidistant. 



2. The line representing the sensation of yellow reaches its cul- 

 minating point upon the ordinate which corresponds to yellow. 



3. This case, which I thought must be general for the four lines, 

 forms, on the contrary, the exception : for the other colours things 

 take place in a different manner. The sensation of red goes on 

 increasing in a straight line, from the blue to the red; and beyond 

 this it continues to rise without deviation till it comes to the orange, 

 where it attains its culminating point, to sink afterwards till it 

 reaches the yellow, where it is zero. 



In like manner the sensation of green attains its maximum in the 

 third green-yellow, and that of the blue in the third blue. 



The signification of these remarkable facts does not come out well 

 unless we look at the experiment itself which has revealed the exist- 

 tence of the three maxima. The fact is as follows : — 



One and the same blue, the sensation of which is mingled with 

 that of the orange on one side and that of the second and third 

 green-yellow on the other, produces with the first a superior sensa- 

 tion of red to that produced by the sight of the red of the circle, 

 * Journal de Physique, t. vii. p. 16. 



