104 SOUND. f Lesson xvm. 



souuds, which well deserves the attention of my 

 young readers, is, that every substance whatever, 

 whose parts are so connected as to be capable of 

 an uniform vibration, may have that vibration pro- 

 duced in it by the sounding of a certain musical 

 note or tone, with which it is in unison. Thus 

 Kircher speaks of a large stone that would tremble 

 at the sound of one particular organ-pipe. Mr. 

 Eoyle states the fact of seats trembling at the sound 

 of organs ; he tells us also, that he has felt his 

 hat to shake under his hand at certain notes, both 

 of organs and other instruments ; and he was 

 told by an experienced builder, that any well- 

 built vault will answer some determinate note. 

 JEven liquids, when so suspended as to be capable 

 of vibration (for example, water in a glass), are 

 observed, not only to vibrate when a particular 

 note is struck or sounded, but actually sound 

 themselves in concord. That water suspended in 

 a glass becomes in reality a sonorous body, is 

 proved by the mode of tuning a set of musical 

 glasses, which become the graver in tone, the more 

 water is poured into them ; for, were it only the 

 empty part of the glass that sounded, the sound 

 would become more acute, as more water is pour- 

 ed in ; but, as the contrary is the fact, it is thence 

 evident that the water and glass together form one 

 compound sonorous substance, of which the 

 greater the quantity or volume, the deeper is its 

 musical tone. 



From what has been already stated, it will ap- 

 pear manifest; that when the producing cause of 



any 



