360 VIBRATION OF STRINGS 



indicate a difference in the pitch of the two notes, which is the greate 

 the more frequent the beats. One string by way of trial is mad 

 a very little tighter, and if the beats become slower, that string i 

 still more tightened until the beats disappear altogether ; if, on th 

 contrary, the beats become more frequent, the string is slackene 

 until they cease. 



When the note of the shortened string is to be compared with tli 

 fundamental note of the unshortened one, one end of the woode 

 bar is placed so far under the string which is to be shortened, ast 

 leave the other siring perfectly free. 



If the string be lightly touched in the middle, usin 

 the soft tip of the finger, or if the edge of a small mov( 

 able triangular bridge be placed at that point, and tb 

 string be plucked near one end, the note produced wi 

 again be the octave of the fundamental note of tl 

 string ; the string will be seen to vibrate on both sid( 

 of the middle point, and will present the appearaiK 



FIG. 215 (yg- real size]. 



shown in fig. 215 (in which, as in the next two figure 

 the flexure is, for the sake of clearness, much exagg 

 rated). 



The point touched will remain at rest ; it is term< 

 a nodal point, or simply a node, while the vibrating po 

 tions are called ventral segments or loops. 



If the finger be removed after the string h 

 begun to vibrate, the vibrations will continue in tl' 

 same manner, the node will remain in the middle, ai 

 the note will be the octave of the fundamental note. 



Next let the string be touched at a point distant on 

 third of its whole length from one end (at 40 or 80 cn 

 Close observation will show that the string is nc 



