144 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK n. 



the stiings are touched by the bow. The bow is furnished with hairs 

 equally and smoothly stretched out like a ribbon 

 and rubbed with rosin, and when drawn across the 

 string it produces a rapid series of shocks more or 

 less distinct, which, according as the bow is moved 

 up or down, displace the string to the right or left 

 from its state of equilibrium and give it, at each 

 short interval, a series of periodic oscillations, the 

 velocity of which depends upon the length of the 

 vibrating portion, the tension of the string, and its 

 diameter. By these multitudinous and isochronous 

 vibrations, a note is produced the pitch of which 

 is determined by the number of vibrations within 

 a second of time. 



If it were the string only that vibrated between 

 its points of support, which are, on the one hand 

 the bridge, and on the other the nut or the finger 

 acting as a nut, the tone would be thin, without 

 fulness, and without brilliancy. But by means of 

 the bridge, the vibrations of the string are trans- 

 mitted to the belly, and from thence, either by the 

 ribs or sides, or by the sound-post, to the back and 

 through the entire instrument. But the mass of air 

 contained between these two plates has an important 

 part to play through the vibiations which are com- 

 municated to it. It has the effect of imparting 

 strength to the .tone like a tube of large area and 

 little depth, and this explains why it strengthens 

 all the notes emitted by the instrument, although 

 there are always, in the indefinite series of the 

 notes of the violin, some amongst them which come 

 out with more force and fulness than others. 



The / holes are necessary to transmit the vibra- 

 tions of the mass of air inclosed in the sounding- 

 box, outside, to the exterior air. Without the / 

 holes, the notes would be dull. Savart, who long- 

 studied the mechanism of the violin, in a series' 

 of remarkable experiments discovered that this mass 



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