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CHAPTER I. 



PRELUDE TO THE SOLUTION OF PROBLEMS IN 

 ACOUSTICS. 



IN some measure the true theory of sound was 

 guessed by very early speculators on the sub- 

 ject; though undoubtedly conceived in a very vague 

 and. wavering manner. That sound is caused by 

 some motion of the sounding body, and conveyed 

 by some motion of the air to the ear, is an opinion 

 which we trace to the earliest times of physical 

 philosophy. We may take Aristotle as the best 

 expounder of this stage of opinion. In his Treatise 

 On Sound and Hearing., he says, "Sound takes 

 place when bodies strike the air, not by the air 

 laving a, form impressed upon it, (a^rinaTi^o/mevoi',) 

 as some think, but by its being moved in a corre- 

 sponding manner ; (probably he means in a manner 

 corresponding to the impulse ;) the air being con- 

 tracted, and expanded, and overtaken, and again 

 struck by the impulses of the breath and of the 

 strings. For when the breath falls upon and strikes 

 the air which is next it, the air is carried forwards 

 with an impetus, and that which is contiguous to 

 the first is carried onwards ; so that the same voice 

 spreads every way as far as the motion of the air 

 takes place." 



