286 OUTLINES OF NATURAL PHILOSOPHY. 



The pleasure derived from the successive or simulta- 

 neous perception of the sounds of this series, ap- 

 pears to be an ultimate fact which can be no farther 

 analysed, but must be referred to the original con- 

 stitution of the mind. The selection of the com- 

 bination of these notes, capable of affording high 

 degrees of pleasure, is the object of the musical 



art. 



'Mifroii . .;;. m 



383. All other sonorous bodies, at the time they 

 emit sound, vibrate in like manner, but according 

 to laws less simple. In wind instruments, the 

 sounding and vibrating body is the air itself. 



The number of vibrations performed in a given time, 

 by any sonorous body, may be determined by com- 

 paring its sound with the note which is sounded by a 

 musical string of a given length, weight and tension. 

 The ear is sufficient to decide what string in a harp- 

 sichord is in unison with the given sound. The num- 

 ber of vibrations performed in a given time by the 

 former, is equal to the number of those performed in 

 the same by the latter. 



384. All musical sounds are computed to be con- 

 tained within ten octaves ; so that the number of 

 vibrations in a given time that yields the gravest 

 note, is to that which yields the most acute, as 1 

 to 2 10 , or as 1 to 1024. 



3 Propagation 



