COMPOSITION OF SOUND WAVES. 297 



of no motion, called nodes or nodal points. The tone 

 produced by the vibrations of the whole length of 

 a string is called its fundamental tone. Tlie tones 

 produced by the vibrations of the segments of a 

 string are called its overtones or harmonics. 



(a.) The fact that a string may thus vibrate in segments, with the 

 further fact that a string, or other sounding body, can hardly be made 

 to vibrate as a whole without vibrating in segments at the same time, 

 furnishes a means of explaining quality or timbre of sound. ( 430.) 



461. Fundamental Tones. When a string 

 vibrates so as to produce its fundamental tone, its extreme 

 positions may be represented ^~~ ^^ 



by the continuous and the 



J FIG. 232. 



dotted lines of Fig. 232. 



This effect is obtained by leaving the string free and bowing 

 it near one of its ends. If a number of little strips of 

 paper, doubled in the middle, be placed like riders upon 

 the string, and the string bowed as just described, all of 

 the riders will be thrown up and most of them off. This 

 shows that the whole string vibrates as one string ; that 

 there is no part of it between the fixed ends that is not in 

 vibration. 



462. The First Overtone. If the string of the, 

 sonometer be touched exactly at its middle with a finger, 

 or better, with a feather, a higher tone is produced when 

 the string is bowed. This higher tone is the octave of the 

 fundamental. The string now vibrates in such a way that 

 the point touched remains at rest. Its extreme positions 



C N D may be represented by the 



of Fiff. 233. The 



point N is acted upon by 

 two equal and opposite forces ; it is urged to move both 



