( 26 ) 



On tlie Velocity of Sound. 



Xhe discordance between the theoretical and experimental ve^ 

 locities of sound has been a subject of inquiry among scientific 

 men since the theory was first started by the illustrious Newton 

 down to the present time. It is no disparagement to this great 

 philosopher to have left the subject in the state he did^ when we 

 consider the scanty data he had to go upon. Since his time, 

 some advances have been made towards a nearer approach be- 

 tween theory and expei-iment ; not^ however, in such a way as 

 to be free from objection. For the theory is, in various parti- 

 culars, :by no means settled on so sure a basis as might be wish- 

 ed. Fully to investigate the subject, may be a task reserved for 

 a future age ; if, indeed, the phenomena of sound be susceptible 

 of .thorough investigation. At present I shall throw out a few 

 hints, which, if they do not fully explain, may serve to gender 

 the discordance between theory and experiment less wonderful, 

 Of may rather, perhaps, excite our wonder that any near ap- 

 proaches should have been made to agreement at all. 



Sir Isaac Newton laid it down as a general principle, regulat- 

 ing the propagations of undulations through elastic media, that 

 the square of the velocity of such propagation is directly as the 

 elasticity of the njedium, and inversely as its density. That 

 there may be something in this theory I would not dispute ; but 

 I suspect it to be of very circumscribed application. In the ab- 

 sence .of any thing like satisfactory jH-oof, I slioyld tiiink it can, 

 at most^ be true when the elastic medi^wn is perfectly homoge- 

 neQ.us a^d ynmixed, and when the length of the vibrations bears 

 tj^e same proportion to the distances between the particles in a 

 state of equilibrium *, 



Most of the enjinent philosophers who treat on the subject, 

 have, without any such scruple or limitation, admitted this theory. 

 They have, for instance, done so, whether in estimating the se^ 

 parate effects of dep^ity, of pressure, temperature, or humidity, 

 on the rate of the propagation of sound through the atmosphere; 

 they have assumed the theory to b.e true, whether the elastic 

 medium be a simple gas, or, like the atmosphere, a compound of 

 oxygen, azote, moisture, &c. ; and they liave taken for granted, 



• See -^rt. Acoustics.— (^up. Encyc. Britan, 



