AND MODEKX PHYSICS. 107 



and blue belonging respectively to three particular 

 parts of the spectrum. 



It should be noticed in concluding our remarks 

 on this part of Maxwell's work that his results are 

 purely physical They are not inconsistent with the 

 physiological part of Young's theory, viz., that there 

 are three primary sensations of colour which can IKJ 

 transmitted to the brain, and that the colour of any 

 object depends on the relative proportions in which 

 these sensations are excited, but they do not prove 

 that theory. Any physiological theory which can be 

 accepted as true must explain Maxwell's observations, 

 and Young's theory docs this ; but it is, of course, 

 possible that other theories may explain them equally 

 well, and bo more in accordance with physiological 

 observations than Young's. Maxwell has given us 

 the physical facts which have to be explained ; it is 

 for tlio physiologists to do the rest. 



