icb 



364 OVERTONES 



The jingling sound is caused by its striking against 

 neighbouring bodies as soon as it begins to vibrate. 



In order to understand how undulations of air, whic 

 are altogether imperceptible to the most delicate sensa- 

 tions, can produce sensible motion in heavy solid bodies. 

 we must consider in the first instance, that such a motior 

 is not produced in any other bodies but those capabk 

 of performing vibrations of exactly the same period at 

 the original vibrations ; further, even in such bodies, r 

 single impulse produces a vibration which is quite in 

 sensible, although the body, in consequence of its inertia 

 repeats the motion several times before it returns t( 

 rest; but if a new impulse is given to the body at th< 

 precise moment when it is beginning its second move 

 ment, then the next vibration will carry the bod; 

 further from its position of .rest than the first did ; an< 

 if a great number of undulations of the air follow eacl 

 other at such intervals that each one augments th 

 movement which the previous impulses have alread 

 produced, the vibrations of the body will at last b 

 strong enough to be easily perceived. 



When several ventral segments are produced in or 

 string of the monochord, the other string will form tt 

 same number of segments if both strings are in unisoi 

 Thus let one string be touched at 30 or 90 cm , and plucke 

 at 15 or 105 cm , while the second string is provided wit> 

 riders at 15, 30, 45, 60, 75, 90, and 105 cm : the riders i 

 30, 60, and 90 cm will remain at rest, while the othe.j 

 will be set in motion. 



We may proceed conversely. Let the second strii 

 which carries the riders be touched at any of the poin 

 of division, and the first string be plucked so as 



