ME. W. POLE ON COLOIJE-BLINDNESS. 
339 
POSTSCEIPT. 
Since the foregoing paper was written, I have had the opportunity of examinmg three 
colour-blind persons, and have found that the vision of each is perfectly dichromic, 
corresponding precisely in general character with my own. But the remarkable feature 
has presented itself, that the coefficients of the colour-top equations vary considerably in 
the different cases. Thus, for example, although my equation XV. will always hold in 
its general form, 
m Vermilion Ult.=j) Black White, 
yet the values of m, w,^, and g will vary for different individuals. 
I have also found reason to suspect that the values of the coefficients may varv to 
some extent, even in the same individual, at different times. 
I hope to investigate both these points more fully. 
October 1859. 
