AND ITS APPLICATION TO THE DETERMINATION OF COLOUR SENSATIONS. 341 



Deducting 69 per cent, of white from the green (SSN 37 - 5), we get the following 

 R and G sensations in luminosities : 



TABLE I. 



SSN. RS. GS. 

 38 = 8 +92 

 40 = 257 + 74-3 

 42 = 40-1 + 59-9 

 44 = 51-1 + 48-9 

 46 = 59-2 + 40-8 

 48 = 67-1 + 32-0. 



From the plotted curves of the red sensations and green sensations at this part of 

 the spectrum we get the following figures : 



TABLE II. 



SSN. RS. GS. 

 38 = 47-9 + 51-2 

 40 = 51-0 + 48-5 

 42 = 54-9 + 44-7 

 44 = 57-7 + 41-9 

 46 = G2 +37-6 

 48 = 67 +32-9. 



Any slight corrections due to alterations found in the violet were made in the green 

 sensations. The violet was calculated from Tahle I. and Table II. as follows : 

 There is a certain quantity of red sensation and of green sensation which with the 

 violet forms white. From the standard equation we know that the luminosity of the 

 red sensation is 2*265 times larger than the green sensation and 49 times larger 

 than the violet in the white. If x be the factor of red in Table I. (which is only due 

 to the excess of red beyond that required to form white), then the same factor must 

 be used with the green. The red sensation in Table II. (which takes into account 

 the white present in the colour) must have deducted from it the red of Table II. x x, 

 and the resulting amount must equal the green in Table II. less the green in 

 Table I. x a; and multiplied by f|4f or 2 '26 5. 



Let R be the red in Table I., R! the red in Table II., G the gi-een in Table I., and 

 GI the green in Table II. Then 



R-.-eR, = (G-xGJ 2-265. 



From this equation we derive x. When x is found, we have a known amount of 

 red on the left-hand side of the equation, which is the amount which combines 



