PNEUMATICS. 285 



invariably produce sounds that are more acute, 

 &c. 



382. If eight strings be such, that the number 

 of vibrations which they perform in a given time 

 are as the numbers 24, 27, 30, 32, 36, 40, 45, 48, the 

 sounds of the first seven will be perceived as in- 

 creasing in acuteness one above another, from the 

 first to the last, and will yield the notes from the 

 combinations of which all musical effects are pro- 

 duced. 



The tone is not affected by the extent of the vibra- 

 tions, but merely by their time. The loudness of 

 the sound is supposed to depend on the greater ex- 

 tent of the vibrations. Noise and discordant sounds 

 arise from a want of isochronism of vibration. When 

 the vibrations of a sonorous body are isochronous, 

 the sound is always musical. 



The last of the strings will sound what is called the 

 octave above the first, and the same series may be 

 repeated again between the number 48 and its 

 double 96, and each note will be an octave above 

 its corresponding note in the first interval ; the num- 

 bers of vibrations will be 54, 60, 64, 72, 80, 90, 96; 

 and it is evident that this series may be continued 

 either up or down without limit. 



The musical scale thus formed, is called the Diatonic 

 Scale. 



The 



