Vibration of Ferromagnetic Wires in a Magnetizing Field. 645 



would appear that molecular couples, do not enter directly 

 into the molecular theory of rigidity. But the existence of 

 similarly directed electric axes in neighbouring molecules is 

 suggestive of the existence of similarly directed axes of rotation 

 in neighbouring molecules; and this would bring in gyrostatic 

 properties of molecules as an element in rigidity. In 

 "A Kinetic Theory of Solids" (Phil. Mag. [5] xxxii.) the 

 ascription of independent kinetic energies in the directions of 

 three rectangular axes amounts to the same thing as taking 

 account of gyrostatic energy. 



It is obvious that a logical deduction from the above prin- 

 ciples must be the formulation of a dynamic theory of 

 dielectric capacity in which electric doublets and molecular 

 gyrostatic properties will play the most important part, and 

 also the systematic development of an electrical theory of 

 thermochemistry on Helmholtz's lines. 



Melbourne, August 1902. 



LXXI. Note on tlie Vibration of Ferromagnetic Wires 

 placed in a Varying Magnetizing Field. By K. Honda and 

 S. Shimizu*. 



IT is well known that ferromagnetic bodies emit an audible 

 sound at the moment of making and breaking the mag- 

 netizing current. Page t first heard the sound in the magnet, 

 when an electric current passed through a copper spiral 

 placed between the poles of a horse-shoe magnet. The sound 

 was more intense at the break than at the make. A similar phe- 

 nomenon was also observed by Delezenne J. Marrian § placed 

 iron and steel wires in a coil, and by making and breaking the 

 magnetizing current, he heard a sound due to the longitudinal 

 fundamental vibration of the wires. Matteucci || examined the 

 effect of tension, and found that the pitch of the sound 

 was independent of the tension, but that the intensity was 

 decidedly increased. The investigation with iron bars of 

 different lengths led Wertheim ^f to the conclusion that each 

 bar vibrated in its fundamental mode. By passing an inter- 

 mittent current through the magnetizing coil, he heard a 

 continuous sound, the pitch of which was the same as that 



* Communicated by the Authors. 



+ Page, Pogg. Ann. vol. xliii. p. 411 (1838) ; Wiedemann's JElectricitat, 

 vol. iii. p. 838. 



t Delezenne, Pogg. Ann. vol. lxiii. p. 530 (1838). 



* Marrian, Phil Mag. vol. xxv. p. 382 (1841). 

 || Matteucci, Archives, vol. v. p. 389 (1845). 



f Wertheim, Pogg. Ann. vol. lxxvii. p. 43 (1848). 



