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XXIX. A Syntonic Hypothesis of Colour Vision with Mecha- 

 nical Illustrations. By ProL E. M. Barton, F.R.S., and' 

 H. M. Browning, M.Sc* 



[Plate VI.] 



Contents. 



1. Introduction. 2. Some fundamental facts of Vision. 

 3. Three vibratory responders postulated. 4. Mathematical 

 theoiy. 5. Experimental arrangements. 6. Results aud 

 their significance. 7. Summary and Conclusion. 



1. Introduction. 



Hj^HE conception of tri-colour vision due to Young, and 

 A further developed by Helmholtz and Maxwell, has 

 proved so successful as to be almost universally accepted. 

 But in one respect it appears incomplete, since red, green,, 

 and violet sensations are always referred to without any 

 indication being given of the type of mechanism to which 

 the initiation of those sensations is ascribed. 



Theories of audition often involve some kind of resonance, 

 but are occasionally attacked as demanding a larger number 

 of separate vibrators and nerves than are actually present. 

 An attempt was recently made t to reduce very consider- 

 ably the number of separate aural mechanisms and associated 

 nerves needed on such an hypothesis. 



This led us to imagine that a similar view for the explan- 

 ation of colour vision might be successful provided the 

 number of vibrating responders for each element of the 

 retina could be reduced to three ; being one each for red r 

 green, and violet. 



Probably the formulation of any such syntonic hypothesis 

 has been deferred owing to the impossibility of imagining 

 vibrators of such high frequencies in any molar system and 

 the very considerable difficulty in the way of such high 

 frequencies for molecular or atomic vibrators. These diffi- 

 culties are distinctly lessened by the advent of the electron 

 theory and the " resonators" of Planck. 



But in adopting for the eye the so-called resonance theory 

 started for the ear, this hypothesis cannot by itself suffice 



* Communicated by the Authors. 



t " The Resonance Theory of Audition," Phil. Mag. July 1919. 



