SENSATIONS IN TERMS OF LUMINOSITY. 269 



of coloured rays was issuing from it, when it was closed till the match was made. 

 Again it was closed till it was evident that the colour was in defect, when it was 

 opened till the match appeared correct. A mean of six observations was taken as 

 being the most probable value of the mixture. 



(XIV.) The Red and Green Sensations Unmixed with Violet. 



To find the luminosities of the red and green sensations in the orange which 

 matches a solution of bichromate of potash. 



W R 288-5 



(Bich) + 16-5 = 45-5 + 32. 



W 



In the bichromate there is 4 '5. Therefore 



W R 288-5 

 (Or) + 21 = 45-5 + 32. 



RS G 



(Or) = 45-5 + (32 -21) 



RS GS 

 = 45-5 + 11. 



Therefore 



RS GS 



(1) 100 Or =80-53 + 19-47. 



Taking another example in detail, the slits being at 205 (R) and 270 (G), 



W R 270 



(Bi) + 8-5 = 39-95 +24-5. 



W W R 270 



(Or) + 4-5 + 8-5 = 39'95 + 24*5. 



R 270 W. 



(Or) = 39-95 + 24-5 13 



R 270'* 



= 39-95 + 11-5. 



R 270' 

 (2) 100 (Or) = 77-6 + 22-4. 



* 270' means 270 deprived of all violet. 



