[ 440 ] [Bode V. 



CHAP. X. 



OF SOUND. 



Sound cenfidered in Three Points ofView.-Caufed by a Vibration in 

 the Parti of Bodies. Propagated by an undulatory Motion of the 

 Air. Thij proved by Experiment. GlaJJes broken by an Effort of 

 the Voice.-*- -Elafilc Fluids 'not the only Means of tranfmitting Sound. 

 Water or folid Bodies convey it. Velocity of Sound. Experiments 

 on this Subjefi. Echoes."- Whifpering Gallery. 



THERE is another property of air, which could 

 not fo conveniently be introduced into the pre- 

 ceding chapter j I mean the power of tranfmitting 

 founds. 



Sound is produced by a vibrating motion, excited 

 in a fonorous body by a blow or a fhock from another 

 body, and the fame motion is communicated by this 

 fonorous body to the fluid which furrounds it, and 

 tranfmitted by this fluid to the ear, which is an organ 

 admirably adapted to receive its impreflion. 



From this definition it follows, that found fhould be 

 confidered in three different views - 3 firft, with refpect 

 to the fonorous body which produces it; fecondly, as 

 to the medium which tranfmits it j and, thirdly, as to 

 the organ which receives the impreflion. 



Thofe bodies are properly calltdfonorous which af- 

 ford a found diftinct, and of fome duration, fuch as 

 bells, the firings of a violin, &c. and not thofe which 

 caufe only a confufed noife, fuch as a ftone produces 

 when it falls upon a pavement. When bodies are, 

 ftri&ly fpeaking, fonorousj they are neceflarily elaftic, 



as 



