l80 THE SPEECH OF MONKEYS. 



unit, but there seems to be a difference of ulti- 

 mate form and mode of propagation which has 

 much to do with the contour of the developed 

 sound. 



By mode of propagation I mean the conduct of 

 the organs used for the purpose of producing the 

 sound, the apertures through which the sound- 

 force passes, and the auxiliaries by which it is 

 moulded into certain shapes. By ultimate form 

 I mean the geometrical shape of the sound-force 

 when first converted into sound. That there is 

 such a thing as form has been clearly demon- 

 strated by the phoneidoscope. Prof. John B. De 

 Mott has very kindly aided me in reducing cer- 

 tain sounds to a visible condition. I had con- 

 ceived an idea before this that if the path 

 described by the energy which produced sound 

 could be made visible it would be found to 

 have the form of a convolute spiral ; that these 

 spirals recede from the centre or point of prop- 

 agation in every direction like the radii of a 

 sphere, and that that aspect of sound which we 

 call waves is simply the point at which these 

 spirals intercept each other, which of necessity 

 would be of uniform distance from the centre, 

 increasing at each successive point throughout 



