242 



Dr. W. Huggins. 



[May 24„ 



holes. One foot of the bridge rests npon a comparatively firm 

 support, namely, the sound-post, which is a solid rod inserted between 

 the two plates, back and belly, of the instrument. It is only the 

 other leg which agitates the elastic wooden plates, and through them 

 the included mass of air."* 



The experimentsf which follow have been made for the purpose of 

 ascertaining whether it be any part of the function of the sound-post 

 to convey vibrations to the back, or whether this post acts solely as a 

 prop supporting the belly, so that its elasticity is not injured by the 

 pressure from the strings, and also, as Daguin states, affords the firm 

 basis which he considers necessary for one foot of the bridge. 



Mr. Hill, and other practical men, maintain that the quality of the 

 wood of which the sound-post is made affects the tone of the violin, 

 as undoubtedly do very minute differences of position. If the quality 

 of the wood is important we must admit that vibrations are conveyed 

 by the post. 



Whether or not the sound-post exercises the function of trans- 

 mitting vibrations, it is obvious (1) that it performs the important 

 duty of contributing to the support of the belly ; (2) that the nodal 

 arrangement of the belly, and also that of the back, are influenced by 

 the pressure of the ends of the post against the upper and lower 

 plates ; (3), that Helmholtz is right, at least so far that the leg of the 

 bridge under the 4th or Gr string has much more power than the other 7 

 in setting the belly into vibration. 



The usual way of investigating vibrations by the scattering of 

 sand over the surface of the agitated body is difficult of application 

 to the violin, on account of the curved form of the upper and lower 

 plates. I found a convenient method to be by the use of what I may 

 call a touch-rod. It consists of a small round stick of straight- 

 grained deal a few inches long ; the forefinger is placed on one end,, 

 and the other end is put lightly in contact with the vibrating surface. 

 The finger soon becomes very sensitive to small differences of agitation 

 transmitted by the rod. 



The experiments were made on a strongly made modern violin, and 

 in some cases repeated on a fine violin by Stradiuarius in the posses- 

 sion of the writer. 



The sand method, and also the touch-rod, showed that the position 

 of maximum vibration of the belly is close to the foot of the 

 bridge under the 4th or G string. The place of least vibration is 

 exactly over the top of the sound-post behind the other foot of the 

 bridge. The back is strongly agitated, the vibrations being least 



* " Sensations of Tone," translated by Ellis, p. 137. In the 4th German edition 

 this passage remains unaltered. 



f I wish to express my indebtedness to Mr. A. J. Ellis, F.E.S., for some sugges- 

 tions in connexion with these experiments. 



