326 HISTORY OF ACOUSTICS. 



As is the case with all such specimens of ancient 

 physics, different persons would find in such a state- 

 ment very different measures of truth and distinct- 

 ness. The admirers of antiquity might easily, by 

 pressing the language closely, and using the light of 

 modern discovery, detect in this passage an exact 

 account of the production and propagation of 

 sound : while others might maintain that in Aris- 

 totle's own mind, there were only vague notions 

 and verbal generalizations. This latter opinion is 

 very emphatically expressed by Bacon 1 . "The col- 

 lision or thrusting of air, which they will have to be 

 the cause of sound, neither denotes the form nor 

 the latent process of sound ; but is a term of igno- 

 rance and of superficial contemplation." Nor can it 

 be justly denied, that an exact and distinct appre- 

 hension of the kind of motion of the air by which 

 sound is diffused, was beyond the reach of the 

 ancient philosophers, and made its way into the 

 world long afterwards. It was by no means easy to 

 reconcile the nature of such motion with obvious 

 phenomena. For the process is not evident as 

 motion; since, as Bacon also observes 2 , it does not 

 visibly agitate the flame of a candle, or a feather, or 

 any light floating substance, by which the slightest 

 motions of the air are betrayed. Still, the per- 

 suasion that sound is some motion of the air, con- 

 tinued to keep hold of men's minds, and acquired 

 additional distinctness. The illustration employed 



1 Historia Soni et Auditus, vol. ix. p. 68. 2 Ibid. 



