in the Problem of Sound. 405 



a hiss, a buzz, or a whisper, and of which the phonetic symbol 

 is S or Z. Perhaps also the sound which we call a roar, of 

 which the symbol is R, is related to it; for philologists appear 

 to take for granted that these letters represent cognate sounds 

 (thus Niebuhr assumes as indubitable that Aurunci and Au- 

 sonii are the same word). My reasons for connecting the 

 sound of S with the interruption of continuity, or with the 

 broken character of the aerial wave, are the following: — 



1. It has long ago been remarked that the sound of S is 

 not returned by an ordinary echo. In like manner, a broken- 

 headed sea is not reflected by a vertical pier. When a broken- 

 headed sea strikes a pier perpendicularly, it is thrown upwards ; 

 when it strikes it obliquely, it is partly thrown upwards and 

 partly it runs horizontally along the face of the pier. In 

 neither case is there any reflexion of the broken head, or any 

 creation of a broken wave travelling in the opposite direction, 

 although the swell is reflected according to the usually under- 

 stood laws. 



2. It is well known that in whispering galleries the sound 

 of a whisper is carried along the surface of the dome, and never 

 quits that surface, and can be heard on the opposite side only 

 by applying the ear very near to that surface ; while an ordi- 

 nary sound is not transmitted along the surface, and is not 

 heard at the opposite side of the dome in any striking inten- 

 sity. In like manner, a broken-headed sea will run along the 

 face of a vertical pier for a considerable distance without show- 

 ing any disposition to quit it; while an ordinary fluctuation is 

 thrown ofl'it at once, in the form of a swell rolling away at an 

 angle given by the usual laws of refiexion. 



Whether there is any well-established instance of the con- 

 version of a clear musical sound into a hiss or buzz by mere 

 distance of transmission, I am not able to say ; but I should 

 think that, long before the wave could have received its change 

 of character to the degree necessary to produce discontinuity 

 of particles, even supposing that its coefiicient had remained 

 undiminished, that coefficient would from friction or from ex- 

 pansion of the wave have become so small, that there would 

 be no perceptible tendency in the wave to change its form. 

 So far however as the tendency to change the form exists, it 

 will be greater for loud sounds than for faint sounds, and 

 greater for sounds in a high key than for sounds in a low key ; 

 or in other words, the sounds which might be expected soonest 

 to degenerate into hiss or buzz would be loud sounds on a 

 high key. I am, Gentlemen, 



Royal Observatory, Greenwich, Your obedient Servant, 



May 17, 1849. G. B. AlRY. 



