AND MODERN' PHYSICS. 105 



A B <J. Maxwell showed that, with his standards, 

 nearly all colours could bo represented by points 

 inside the triangle. The colours ho had selected 

 as standards were very close to primary colours. 



Again, he proved that any spectrum colour between 

 red and green, when combined with a very slight 

 admixture of violet, could be matched, in the case 

 of cither Mrs. Maxwell or himself, by a proper mix- 

 ture of the red and green. The positions, therefore, 

 of the spectrum colours between red and green lie 

 just outside the triangle A B C, being very close 

 to the lino A B, while for the colours between green 

 and violet Maxwell obtained a curve lying rather 

 further outside the side B C. Any spectrum colour 

 between green and violet, together with a slight 

 admixture of rod, can bo matched by a proper mix- 

 ture of green and violet 



Thus tho circle of Newton's diagram should bo 

 replaced by a curve, which coincides very nearly 

 with tho two sides A B and B C of Maxwell's figure. 

 Strictly, according to his observations, the curve lies 

 just outside these two sides. Tho purples of the 

 spectrum lie nearly along tho third side, C A, of the 

 triangle, being obtained approximately by mixing 

 the violet and the red. 



To tind the point on the diagram corresponding 

 to the colour obtained by mixing any two or more 

 spectrum colours we must, in accordance with New- 

 ton's rule, place weights at the points corresponding 

 to the selected colours, and tind the centre of gravity 

 of these weights. 



This, then, was the outcome of Maxwell's work on 



