286 



SOUND 



of some convenient weight ; then lay a yardstick along the box 

 in order that the lengths may be determined accurately. If 

 the stretched string is plucked with the fingers or bowed with 

 the violin bow, a clear musical sound of definite pitch will be 



produced. Now divide the 

 string into two equal parts by 

 inserting the bridge midway 

 between the two ends ; and 



FIG. 147. The length of a string in- pluck either half as before, 

 fluences the pitch. The note given forth is of a 



decidedly* higher pitch, and is the octave of the note sounded 

 by the entire wire. If now the bridge is placed so that the 

 string is divided into two unequal portions such as i : 3 and 2 : 3, 

 and the shorter portion is plucked, the pitch will be still higher; 

 the shorter the length plucked, the higher the pitch produced. 

 This movable bridge corresponds to the finger of the violinist ; 

 the finger slides back and forth along the string, thus changing 

 the length of the bowed portion and producing 

 variations in pitch. 



If there were but one string, only one pitch 

 could be sounded at anyone time; the additional 

 strings of the violin allow of the simultaneous 

 production of several tones. 



Wind instruments. In the so-called wind 

 instruments, such as clarinet and flute, sound is 

 produced by vibrating columns of air inclosed 

 in tubes or pipes of different lengths. The air 

 column is thrown into vibration either directly, 

 by blowing across a narrow opening at one end 

 of a pipe, as in the case of the whistle, or indi- 

 rectly, by exciting vibrations in a thin strip of 

 wood or metal, called a reed, which in turn com- 

 municates its vibrations to the air column within. organ pipes. 



