338 K. Honda and S. Shimizu on Change of Length of 



The fact that Ramsay and Young's formula is deducible 

 from Rankine's shortened formula is indicated by Ayrton 

 and Perry in a paper to the Physical Society*, in which 



the accuracy of Rankine's complete formula is strongly 

 insisted on. 



11 Leopold Road, Ealing, W. 



XXXVII. Change of Length of Ferromagnetic Wires under 

 Constant Tension by Magnetization. By K. Honda, Riga- 

 kushi, and S. Shimizu, Rigakushif, 



1. T~N his earliest systematic experiments on the change of 

 JL length by magnetization of iron and steel rods, 

 Joule t noticed that the effect of tension is to diminish the 

 elongation, and that if the tension exceeds a certain limit 

 the magnetization causes contraction instead of elongation. 

 Repeating the same experiment, S. Bidwell§ made special 

 investigation on this point, and confirmed Joule's results. 

 Besides iron he examined nickel wire ; the magnetic contrac- 

 tion of the wire is decreased by tension in weak fields, but it 

 is increased in strong. These changes also increase with 



* Phil. Mag. [5]xxi. p. 255; Proc. Pkys. Soc. vii. p. 372 (1886). 

 f Communicated by Prof. Nagaoka. 

 % Joule, Phil. Mag. xxx. pp. 76, 225 (1847). 



§ Bidwell, Proc. Roy. Soc. xl. p. 109 (1885) ; torn. cit. p. 257 (1886) : 

 ibid, xlvii. p. 469 (1890) ; Ewing's Magnetic Induction, p. 240. 



