340 Prof. Barton and Miss Browning on a Syntonic 



T ie visual analysis of colours into tlieir components is 

 practically lacking, but t! e spatial properties of the eye and 

 associated judgment have great power in perceiving direction 

 and estimating range. 



The ear, on the other hand, has an astonishing develop- 

 ment of analytical power, but its perception of direction 

 does not approach that of the eye. 



3. Three Vibratory Responders postulated. 



As shown in a previous paper on " The Resonance Theory 

 of Audition " *, we saw that the resonators must have a 

 range comparable to that of distinct recognition of pitch. 

 Similarly, if a " resonance theory " is to play any part in 

 accounting for colour vision the " resonators " must be 

 supposed to have a range approximately equivalent to that 

 of the visible spectrum. The exact relations between the 

 range of perception and that of the resonators may be 

 slightly different in the case of the ear and the eye because 

 of the different dampings which are probable in each 

 •case. 



Obviously if the facts of colour vision depend upon 

 syntony the number of responders (for each element of the 

 retina) will probably be three only, since the tri-colour 

 theory of Young-Helmholtz has been so successful. Accord- 

 ingly if only three responders are provided for about one 

 octave, the resonance of each must be very much spread 

 instead of very sharp, as the latter would involve gaps in 

 the spectrum seen by the eye. From this it follows that 

 the damping of the responders (as measured by logarithmic 

 decrement) must be greater for the eye, than in the case of 

 those that have any measure of success in explaining 

 audition. 



These considerations point to the postulation of a set of 

 three vibratory responders tuned respectively to red, green, 

 and violet, their precise frequencies and dampings being 

 chosen to accord with the facts of the case. 



Having previously used, for the imitation of the ear's 

 mechanism, a set of pendulum responders tuned to each 

 semitone of an octave, it now seemed well to adopt, as a 

 trial for the eye, three of the same responders, namely, 

 those then referred to as 0$, F#, and B. 



For the purpose of imitating vision these responders may 

 btj taken as corresponding to wave-lengths of 0*76//,, 0*55 /*, 



* Phil. Mag. July 1919. 



