500 



Capt. W. de W. Abney. Examination for [May 14, 



He was subsequently tested with colour discs Ultramarine (U), 

 Red-royal (R), Emerald-green (G), Chrome-yellow (Y), White (W), 

 and Black (B). 



It was found that 



165 (U) + 48 (R) + 147 (G) = 75 (W) + 285 (B). 

 The black reflected 3 "4 of white ; hence the true equation is 



(i). 165 (U) + 48 (R) + 147 (G) = 84-7 (W) + 275 (B). 

 (ii). 120 (U) -|- 240 (Y) = 196 (W) + 164 (B) (corrected) 



With 260 (U) + 100 (Y) he sees blue. 



250 (U) + 110 (Y) light-blue. 

 242 (U) + 118 ( Y) no blue. 



This last in connexion with (ii) shows that his blue perception is 



