1 68 On the Deadening of the Sounds of Solid Bodies. 



Hence, by the resistance of the air, the quicker vibrations are 

 more powerfully deadened than the slower ones. 



It must be remarked in reference to (2) that, according to 

 Stokes*, the quicker vibrations of solids in air are more power- 

 fully deadened than slower ones. 



The first result recalls to mind the view of W. Weber f as to 

 that cause of the decrease in the amplitude of oscillation which 

 has its origin in the nature of the body itself. W. Weber shows 

 that the phenomenon which he discovered, the elastic reac- 

 tion, must produce a diminution in the amplitude of vibration. 

 Now it is a priori probable that this reaction must manifest 

 so much the stronger effect the slower the vibrations — which is 

 in accordance with the author's experiments, according to which 

 the slower torsion vibrations of a thread are more powerfully 

 deadened by the internal resistance than more rapid ones. 



We have hitherto been concerned alone with the dependence 

 of the deadening arising from the internal resistance on the time 

 of vibration, the length of the thread remaining constant. To 

 ascertain the dependence of this deadening on the length of the 

 thread, it is unnecessary to eliminate the resistance of the air ; 

 for an alteration in the deadening with a change in the length 

 of the thread, the time of vibration remaining constant, can only 

 be ascribed to the thread. It has now been found that the 

 deadening increases with a decrease in the length of the thread — 

 that is, that, for the same duration of vibration, shorter threads 

 produce stronger deadening than longer ones. 



To apply vibration-experiments to experiments on the conduc- 

 tion of sound, the assumption must be made that the deadening 

 arising from the internal resistance, in the sound-vibrations of 

 solids, must depend in the same manner on the duration of vi- 

 bration and the magnitude of the vibrating divisions as has been 

 established in the case of slow torsion vibrations. 



On this assumption, the reason that the higher tones when 

 conducted through solids are more powerfully deadened than 

 the deeper ones cannot arise from the fact that with the higher 

 notes the vibrations are more rapid-; for, according to the vibra- 

 tion-experiments, it is just the slower vibrations which for the 

 same wave-length are more rapidly deadened by the internal re- 

 sistance than the quicker ones. This cause can only be that, 

 in the higher notes, smaller vibrating divisions (wave-lengths) 

 are formed ; for, according to the vibration-experiments, a greater 

 deadening force is developed in shorter waves (for the same du- 

 ration of vibration) than in longer ones J. 



* Transactions of the Cambridge Philosophical Society, vol.ix. part 2. 



t Pogg. Ann. vol. xxxiv. 



X To this must be added that the mass to be moved is less in the case 



