1894.] Measurement of Colour produced by Contrast. 

 Table I. Diluted Background. 



225 



as matched could ever make white when mixed with the colour which 

 caused it was very readily proved. The two colours were thrown on 

 the same cube, and the proportions of the colours altered. In some 

 few cases there was a very close approximation to the formation of a 

 white which matched the electric light, but in the majority no match 

 could be made. 



Another set of experiments further exemplified this. In instru- 

 ment No. II three colours were chosen one in the red, another in 

 the green, and the third in the violet. The same three colours were 

 found in instrument No. I, and three adjustable ones placed in them. 

 With these three slits a match was made with the white of the 

 electric light in the first instance a contrast between white and the 

 red was then formed on the cube, illuminated by No. II instrument. 

 The red was then shut off from instrument No. I, and the mixed 

 violet and green lights were diluted with white light, but in no state 

 of dilution did the white stripe as coloured by contrast appear of the 

 same tint as the complementary colour of the red as obtained from 

 the dilated mixture. The same negative results were obtained by 

 making the contrast with the green. With the violet a much, nearer 

 approach was made. 



This experiment was varied by matching the light from an 

 Argand gas burner, and by forming the contrasts by means of the 

 same quality of light. The same negative results were again obtained. 



The difference, if any, was next observed between a contrast made 

 by a saturated colour and that given by the diluted colour. 



VOL. LVI. y 



