AND ITS APPLICATION TO THE DETERMINATION OF COLOUR SENSATIONS. 348 



Another example may be given of SSN 25'5. The equation is 



(49-05.) (25-5.) 



96 + 4-0 = 100. 

 RS. GS. 



In 49'05 there is 70'1 +29'9, and the equation becomes, after equating with the 

 standard equation, 



(25 -5.) RS. GS. V. 

 100 = 27-5 + 37-5 + 35. 



Similarly it was found that 



(27-1.) RS. GS V. (18-6.) RS. GS. V. 



100 = 30-8 + 45-9 + 23-3, 100 = H-3 + 7'3 + 81 "5, 



(23-7.) RS. GS. V. (15-5.) RS. OS. 



100 = -24 + 24 + 52, 100 = 4'6 + 2'l +93'3. 



Beyond SSN's 14 and 12 respectively, where the red and green sensations vanish, 

 the violet alone remains, but having different intensities. 



(15.) Formation of the Sensation Curves. 



From the foregoing equations curves of violet-green sensation and red sensation 

 were plotted, and any small irregularity was smoothed. The ordinates thus found 

 are given in the following Table III., in Columns IV., V., and VI. 



Columns I., II., and III. represent (i) the standard scale numbers of the prismatic 

 spectrum (the same as used in my previous paper), (ii) the wave-lengths, and (iii) the 

 luminosity of the spectrum of the crater of the electric (arc) light as judged by the 

 centre of the eye. 



Columns VII., VIII. , and IX. are the luminosities of the colours in terms of the 

 red sensation (RS), the green sensation (GS), and the violet (V). These are obtained 

 by multiplying IV., V., and VI. by Column III. and dividing by 100. 



In Columns X. , XI. , and XII. are given the percentage composition of the different 

 rays in terms of RS, GS, and BS (the blue sensation). These are obtained by 

 reducing the violet sensation to -ffa of its value in Column VI. (which is the 

 percentage of blue which the violet contains), and adding i- - - of the violet to the 

 red in Column IV. GS is the same in Columns V. and XI. 



Columns XIII., XIV., and XV. are the luminosities of RS, GS, and BS as contained 

 in the different colours, and are obtained, as before, by multiplying XI., XII., and 

 XIII. by the luminosities in Column III. and dividing by 100. Column XVI. is 

 Column XIV. multiplied by 2 '3, and Column XVII. is Column XV. multiplied 

 by 178. 



