112 Notice of some Recent 



a portion of the cord will unfold itself upon the bridges, 

 the vibrating cord will thus be lengthened and the tension 

 diminished. By this means, the duration of the vibration 

 will be increased which had been lessened by the greater 

 tension ; it becomes no difficult calculation, to find the 

 proportion at which both influences compensate themselves, 

 and at which this practical correction is available. 



The experiments of Weber and H'allstrbm upon com- 

 pound tones did not agree, but by new researches, the for- 

 mer has ascertained, that one and the same cord (without re- 

 ference to the falsetto tone) gives not merely one fundamen- 

 tal tone (grundton) but two, and, perhaps more, but which 

 cannot be discriminated. When these tones are produced 

 at the same time, a sound which is marked as false affects 

 the ear. Wherefore this, which was not before taken into ac- 

 count by the theory, has its foundation in the circumstance, 

 that, in the theory, the cords are considered as very flexible 

 fibrous bodies, as bodies which do not Occur in nature, 

 while yet they may be so fine and so long, especially when 

 they are made of metal, as to be considered elastic rods. 

 Weber made some trials with fine and large brass, and iron 

 wire, and found the deviations to increase with the thickness 

 of the cord and hardness of the metal. Since, by calculat- 

 ing these results, we find a certain agreement with natural 

 phenomena, Weber thinks, that a more rigid theoretical cal- 

 culation would explain the variations in the tones obtained 

 by Baron Blein, and also in the organ pipes described in 

 Hallstrom's experiments. 



2. Strehlke* has published a mathematical paper upon the 

 situation of the nodes of vibration in straight elastic rods, 

 which vibrate transversely when both ends are free. The 

 object in view, is the same as that obtained by Bernoulli 

 and Ricatti. The calculations are accompanied by experi- 

 ments which shew their agreement with theory. 



3. M. Cagniard Letourf has found, 1st, that the tone pro- 

 duced by the longitudinal vibration of a metallic rod be- 

 comes neither higher nor deeper, by tempering the rods 

 with hammers. 2nd, A steel-wire tempered by sudden 

 cooling, gives, in longitudinal vibrations, a deeper tone 



* Poggendorff 's Annalen, xxvii. 515 ; xxix. 512. 

 t Journal de Chim. Med. ix. 309. 



