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VII. Magnetic Researches. By Prof. G. Wiedemann*. 



[Plate I.] 



SINCE the year 1857 I have published f a series of inves- 

 tigations on the relationship between the mechanical and 

 magnetic properties of bodies, and in 1877 a closely-related 

 paper J on Torsion, in which I proposed to make, in continua- 

 tion, observations on magnetism. In the mean time other 

 investigators have made researches upon the same subject, 

 which indeed are partly only repetitions and extensions of 

 previous work in slightly different form ; but partly also have 

 constituted an actual advance, and in particular points have 

 been supposed to be in opposition to the theory I have pro- 

 posed. I may therefore be permitted briefly to mention these 

 researches here, and to describe certain new experiments 

 connected w r ith them. 



§i. 



Mr. Hughes § has investigated the change in magnetic 

 moment of iron and steel, upon torsion &c, under various 

 conditions, as Wertheim and Matteuci had already done by 

 means of the currents induced in a spiral surrounding a 

 magnetic body. 



He has given a series of experiments on the behaviour, 

 during torsion, of iron wires through or round which a current 

 is passed. I have already ||, in a short note published in 

 English, called attention to the fact that the essential portion 

 of these results had been already observed by myself in the 

 years 1858-60. Nevertheless, Mr. Hughes in further com- 

 munications% after a not altogether correct or quite complete 



* Translated from Wiedemann's Annalen for March 1886. 



t Gr. Wiedemann, Verhandl. der Baseler Naturf. Ges. ii. p. 169. Poo-g. 

 Ann. c. p. 235 (1857); ciii. p. 161 (1858) ; cvi. p. 169 (1859); cxvii. 

 p. 195 (1862). Collected in Wiedemann's Galvam'smus (2nd ed.) and 

 Electricitcit (3rd ed.). 



X Gr. Wiedemann, Wied. Ann. vi. p. 485 (1879). 



§ Proc. Rov. Soc. Lond. xxxi. p. 525 (1879), xxxii. pp. 25, 213 (1881) ; 

 Beibl. v. pp. 538, 687 (1881). 



!| G. Wiedemann, Phil. Mag. (5) xii. p. 223 (1881) ; Beibl. v. p. 689 

 (1881). 



H Hughes, Chem. News, xlvii. p. 63 (1883) ; Nature, xxviii. pp. 159, 

 183 (1883) ; see also xxix. p. 459 (1884) ; Inst, of Mechan. Engineers, 

 1884; Proc. Roy. Soc. Lond. xxxv. pp. 19, 178 (1882), xxxvi. p. 405 

 (1884) ; Journ. *Soc. Telegr. Engineers, xii. p. 374 (1883) ; Theory of 

 Magnetism, Royal Inst. Lecture, February 29, 1884. 



