106 JAMES CLEUK MAXWELL 



colour. It verified the essential part of Newton's 

 construction, and obtained for the first time the true 

 form of the spectrum curve on the diagram. 



The form of this curve will of course depend 

 on the eye of the individual observer. Thus Max.- 

 well and Mrs. Maxwell both made observations, and 

 distinct ditto rences were found in their eyes. It 

 appears, however, that a large majority of persons 

 have normal vision, and that matches made by one 

 such person are accepted by most others as satis- 

 factory. Some people, however, are colour blind, and 

 Maxwell examined a few such. In the case of those 

 whom he examined it appeared as though vision was 

 dichromatic, the red sensation seemed to he absent; 

 nearly all colours could be matched by combinations 

 of green and violet. The colour diagram was reduced 

 to the straight line B (A Other forms of colourblind- 

 ness have since been investigated. 



In awarding to Maxwell the Kumford medal in 

 I860, Major-General Sabino, vice-president of the 

 Royal Society, alter explaining the theory of colour 

 vision and the possible method of verifying it, said : 

 "Professor Maxwell has subjected the theory to this 

 verification, and thereby raised the composition of 

 colours to the rank of a branch of mathematical 

 physics," and he continues: "The researches for which 

 the Rumford medal is awarded lead to the remark- 

 able result that to a very near degree of approxi- 

 mation all the colours of the spectrum, and therefore 

 all colours in nature which are only mixtures of these, 

 can be perfectly imitated by mixtures of three 

 actually attainable colours, which are the red, green 



