CHAP. XL] COLOURS AGAIN. 347 



reduced but not published. I have set it up here this year, 

 and have just got it in working order. I expect to get 

 some more material, and work up the whole together. In 

 particular, I want to find any change or evidence of 

 constancy in the eyes of myself and wife during eight 

 years. I can exhibit the yellow spot to all who have it, 

 and all have it except Col. Strange, F.K.S., my late father- 

 in-law, and my wife, whether theybe Negroes, Jews, Parsees, 

 Armenians, Eussians, Italians, Germans, Frenchmen, Poles, 

 etc. Professor Pole, for instance, has it as strong as me, 

 though he is colour-blind; Mathison, also colour-blind, 

 being fair, had it less strongly marked. 



One J. J. Miiller in Pogg. Ann. for March and April 

 18*70, examines compound colours, and finds the violet 

 without any tendency to red, or the red to blue. He also 

 selects a typical green out of the spectrum. 



