54>6 Mr. E. F. Teschemacher on various Substa?ices 



and of various scientific men, that the prolonged passage of 

 the electricity by metallic wires alters essentially their tena- 

 city. It seemed to me very probable that the elasticity of wires 

 subjected for some time to the intermittence of currents which 

 renders them sonorous, must be altered in a permanent man- 

 ner. 



Since the experiments just mentioned were made, M. Wer- 

 theim has published • a very interesting note, in which he de- 

 scribes a process of observation analogous to mine, although 

 less delicate, and indicates the causes to which he attributes 

 the sounds produced. Although I agree with him on most 

 points, I differ from him both as to what relates to the attrac- 

 tion exerted from the two sides of the centre of the helix, an 

 attraction which he does not mention, and in the explanation of 

 the case in which the wire is directly traversed by the disconti- 

 nuous current. The skilful experimentalist whom I have just 

 named attributes the sound produced to the heat engendered 

 by the current. Nevertheless my wire indicated no percep- 

 tible heat. It results from the experiments of M. de la Rive 

 and my own, that the sonorous state continues with more than 

 600 interruptions a second. How shall we admit that the ele- 

 vation of temperature and the diminution of elasticity which 

 accompany it can disappear in ^^th of a second? The cur- 

 rent of a pile of eleven pairs certainly does not alter the ther- 

 mical state of a bar of a centimetre square in section, as I 

 have directly established f : nevertheless, if it is discontinuous, 

 it renders it sonorous. I may add, finally, that this heating 

 does not take place when the reel is employed, as any one 

 may convince himself by placing a bismuth and iron pair in 

 its hollow, connected with a very delicate rheometer. Never- 

 theless the sonorous property may be the same as with the 

 wire directly subjected to the current. 



Lausanne, March 16, 1846. 



LXXXIV. An Account of various Substances found in the 

 Guano Deposits and in their Vicinity. By E. F. Tesche- 

 macher, Esq.% 



REPORTS having been circulated that large quantities of 

 saltpetre (nitrate of potash and nitrate of soda) were to 

 be found of a very good quality in the neighbourhood of the 

 guano deposits on the coast of Africa, numerous vessels were 



* Comptes Rendus, Feb. 23, 1846. 



f Phil. Mag., Oct. 1843; Archives de I'JElectricile, vol. ii. page 601. 

 I Communicated by the Chemical Society • having been read December 

 1, 1845. 



