34 HISTORY OF 



Every body that strikes against another pro- 

 duces a sound, which is simple, and but one, in 

 bodies which are not elastic, but which is often 

 repeated in such as are. If we strike a bell, or a 

 stretched string, for instance, which are both elas- 

 tic, a single blow produces a sound, which is re- 

 peated by the undulations of the sonorous body, 

 and which is multiplied as often as it happens to 

 undulate or vibrate. These undulations each 

 strike their own peculiar blow ; but they succeed 

 so fast, one behind the other, that the ear sup- 

 poses them one continued sound ; whereas, in 

 reality, they make many. A person who should 

 for the first time hear the toll of the bell, would 

 very probably be able to distinguish these breaks 

 of sound ; and, in fact, we can readily ourselves 

 perceive an intension and remission in the sound. 



In this manner, sounding bodies are of two 

 kinds ; those unelastic ones, which being struck 

 return but a single sound ; and those more elastic, 

 returning a succession of sounds, which, uniting 

 together, form a tone. This tone may be consi- 

 dered as a great number of sounds, all produced 

 one after the other by the same body, as we find 

 in a bell, or the string of a harpsichord, which 

 continues to sound for some time after it is struck. 

 A continuing tone may be also produced from a 

 non-elastic body, by repeating the blow quick and 

 often ; as when we beat a drum, or when we draw 

 a bow along the string of a fiddle. 



Considering the subject in this light, if we 

 should multiply the number of blows, or repeat 

 them at quicker intervals upon the sounding body, 



