Solid Bodies when they are Sounded. 139 



The phenomenon of deadening produced when bodies are con- 

 nected with other sounding bodies gives rise to similar considera- 

 tions. If a leaden tube (even a thin one) be so fitted to a glass tube 

 as to form its prolongation, it is found that the longitudinal tone 

 of the glass tube is very considerably deadened. This is the case 

 even if the leaden tube is as long as half a wave-length, in which 

 case the deadening is least. A steel or brass rod produces under 

 these circumstances scarcely any perceptible deadening. These 

 phenomena lead to the assumption that part of the vis viva of the 

 vibrations in the interior of the body is consumed — and therefore 

 also to the assumption that by sounding there is a production of 

 heat, and a greater one in lead than in steel. 



The author proposed to himself the task of investigating the 

 production of heat by sound from this point of view*. He 

 placed the soldering of a thermopile, in the circuit of which was 

 inserted an astatic galvanometer, against the part to be examined 

 after a body had been made to sound. Before each experiment, 

 he proved that placing the soldering against the body produced 

 no deflection on the galvanometers. 



Longitudinal Tones. 



He first succeeded in demonstrating the heating produced by 

 sound by means of a bar of wax, the sound of which rapidly fades 

 away. A rod of wax was fixed to a thick glass tube in such a 

 manner that it formed its prolongation; its length amounted 

 to half a wave-length of the note (calculated from the velocity 

 of the propagation of sound in wax, which the author has ascer- 

 tained, and the detail of which will appear in PoggendorfPs 

 Annalen). When the soldering of the thermo-element was placed 

 against a node, a deflection of 300 divisions in the direction of 

 heat was produced, while in the loops there was only a deflection 

 of fifty divisions in the same direction. 



A leaden tube of 9 millims. external diameter fastened to the 

 glass rod instead of wax, and also as long as half a wave-length, 

 exhibited a heating of 300 to 400 divisions at a node, and 

 of 40 divisions in a loop. A thinner lead tube (4 millims. ex- 

 ternal diameter) of the same length, connected with the same 

 glass tube, became more strongly heated : a deflection of 600 di- 

 visions was obtained when the thermo-element was placed against 

 the node after sounding the tube. The two leaden tubes were 

 then placed end to end at the same end of the glass tube : in 

 this case there was the same heating virtually in both. It is 



* It has not hitherto been proved experimentally that heat is produced in 

 solids by sounding; for Sullivan's experiments (Phil. Mag. S.3. vol. xxvii. 

 p. 261) and Le Roux's (Comptes Rendus, vol. 1. p. 656) cannot be regarded 

 as a proof of this. 



