Maxwell's Curves to Three-colour Work, &c. 



57 



As the worst ink was always the Blue, I attempted to find a colour 

 which should be more transparent in the green. I obtained a bright 

 green rubbing from Fleming, but I found it was green not because it 

 was more transparent in the green and yellow-green, but because it 

 was more opaque in the blue and violet. There seems to be no ink in 

 the market at present that is sufficiently transparent in the yellow- 

 green. 



19. Attempt to find the Effect of a Difference in the Depth of the Colour. 



The intensity of the reflected beam is given (for any one colour) by 

 I' = I a e , where e is the depth and I is the original intensity of the beam. 

 For another depth of tint / 



I" = la', 



= eloga, 



=/logff, 



K ,1.1 



.-. , = log f -hlog r . 



J 1 



Thus the ratio of the log ought to be a constant through the spectrum. 

 Neglecting the readings in which the aperture was too small to be taken 

 accurately (owing to the backlash of the sector), and in which also the 

 scattered light is of importance, the following results show a very close 

 agreement with theory. 



The inks were only rubbed on with the finger, so that the patches 

 were not exactly uniform, especially the lightest one (1). In this case 



Curves showing the absorptions of the same ink printed to different depths. 



the readings were checked by drawing a smooth curve between the 

 points found, and the numbers taken from the curve, where they were 



