146 THE APPLICATIONS. OF PHYSICAL FORCES. [BOOK n. 



respecting the sound-post, pronounces it inaccurate or incomplete, and 

 the reasons he produces in support of this criticism appear very just : 

 "Upon this explanation," he says, "one cannot understand why the 

 sound-post must be under one foot of the bridge and not in the 

 middle. A second post under the other foot ought to increase the 

 effect, whereas it would in fact deaden the tone of the violin. Ought 

 not the ribs, moreover, to produce the same effect as the sound-post ? 

 Upon due consideration, it appears to me that the effect of the sound- 

 post ought to be explained in the following way. The sound-post has 

 the effect of giving to one foot of the bridge a support by means of 

 which the vibrations are communicated to the belly through the other 

 foot. If one of the feet were not supported on a fixed point, it would 

 rise up whilst the other would fall, because the strings do not vibrate 

 normally with the belly, for the bow being in practice drawn over 

 them very obliquely would, if the bridge had no fixed point, drag it 

 in a transversal direction." 



This is the reason also that the bridge lias two feet resting on the 

 belly. It is perforated because if its bulk were greater, the strings 

 would only communicate feeble vibrations, and the sonorousness of the 

 instrument would be diminished. 1 This is exactly what is done in 

 passages which are to be played pianissimo, and are accordingly 

 marked con sordini, that is, to be played with a mute. The mute, 

 which is a piece of wood or metal fixed on the bridge, communicates 

 to the notes of the instrument a peculiar tone of a muffled, dull, 

 and melancholy character; pressure, however, answers as well as 

 increased weight. 



Savart, who made stringed instruments the subject of much study, 

 tried to account for the influence exercised on the tone by the form of 



elasticity. To the first string, the post secures by its direct pressure a special bril- 

 liancy, whilst the bar having less rigidity^in support, although equal to its work, 

 gives to the other strings a more mellow body and sympathetic fulness of tone. The 

 sound-post is set back to ensure that the bridge gives its full transmission to the 

 belly before its vibrations pass to the back, so that nothing is lost. H. S. 



1 It was Stradivarius who finally 'determined on the present form of bridge ; and 

 it has been found that modifications of it tend to diminish the tone of a good 

 instrument. 



2 The perforation has no reference to bulk ; if the form is truly studied, it will be 

 seen that it is a spring (as a carriage spring) and no doubt Stradivarius saw the 

 desirability of providing this reciprocity of action. H. S. 



