

348 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



It is hardly necessary to define a discord here ; I will 

 use the term for any combination of two tones whose 

 beat- number is less than one fifth the vibration-number 

 of the lower tone, that is tones whose resultant tone is 

 removed from both of them by more than a major 

 seventeenth {i.e., more than two octaves and a major 

 third). 



If the interval be a major second (ratio of vibration- 

 numbers 8:9), the interval between c' and d' for instance, 

 then the highest resultant tone of the two is three, octaves 

 below the lower of the two : i.e., it is C,. 



The basilar waves produced by combination of these 

 two are of complex form, eight waves of one series cor- 

 responding to nine of the other. At the points c' and 

 d' and also at points between them the tectoria will be 

 brought down upon the sense-hairs, and with rhythmically- 

 varying force. The violence of the disturbance being at 

 its maximum at intervals of time corresponding to eight 

 periods of the lower tone (or nine of the upper) : the 

 disturbance being at these moments about twice as 

 violent as that produced by either tone separately, while 

 at the moment intermediate between two of these the 

 disturbance will be practically nil. 



At the point C,, every eighth wave of the series c' and 

 every ninth wave of the series a" will pass simultaneously 

 and there produce a stimulation leading to a sensation of 

 the tone C, . 



An interesting example of this effect is Koenig's, now 

 classic, experiment of sounding the notes c"" and d"" simul- 

 taneously {i.e., 2048 and 2304) the resultant (" differential") 

 tone 256 {c') being distinctly heard. (See Nature, XLIL, 

 p. 190.) 



Besides these resultant-tone stimuli there will be pro- 

 duced disturbances of the relative positions of tectoria 



