30 Mr. GL Barlow. Effects of Magnetisation [June 18, 



Guerin's suggestion of a symbiotic relationship. Such can be conceived 

 of as arising from a former sclerotium- (or spore-) forming habit by the 

 adoption of a new intra-seminal mode of infection. 



" On the Effects of Magnetisation on the Electric Conductivity of 

 Iron and Nickel." By Guy Babloyv, B.Sc, Eesearch Fellow 

 of the University of Wales. Communicated by Professor A. 

 Gray, F.B.S. Eeceived February 20, — Bead March 6, — Be- 

 ceivecl in revised form June 18, 1902. 



That magnetisation has an effect on the electric conductivity of 

 metals was first noticed in 1856 by "William Thomson* (Lord Kelvin), 

 and since then, on account of its very great theoretical interest, this 

 phenomenon has formed the subject of numerous experiments. These 

 later investigations have been made by Tomlinson,f Bighi,| Hurion,§ 

 Leduc,|j Ettingshausen and Nernst,^! Ettingshansen,** Goldhammer,ft 

 Lenard and Howard,} \ Lenard,§§ Henderson, 1 1 j| Beattie,1ffl Gray and 

 Jones,*** and others. 



Two cases of the phenomenon must be carefully distinguished — 

 (i.) Longitudinal effect, when the direction of the electric current is 

 parallel to the lines of magnetic force, (ii.) Transverse effect, when 

 the current is perpendicular to the lines of force. The latter effect is 

 closely connected with the Hall phenomenon, and has received the 

 name of Longitudinal Hall Effect. 



The following results obtained by previous experimenters are of 

 interest in connection with the present investigation. For bismuth, 

 Goldhammer found the change of resistance to vary as the square of 

 the magnetic field, and since in this metal the magnetisation I is pro- 

 portional to the field, this result may be written A 9 = al 2 , where A<£ 

 denotes the fractional increase of resistance, i.e., the increase of resist- 



* ' Math, and Phys. Papers,' vol, 2, p. 307. 



t ; Phil. Trans.,' 1883. 



X : Journ. de Physique,' to]. 3, p. 355 (1884). 



§ ' Compt. Rend.,' vol. 98, p. 1257 (18S4). 



|| ' Corapt. Eend.,' vol. 98, p. 673 (1884). 



«~ 1 Wien. Ber.,' vol. 91, part 2, p. 560 (1886). 



** < Wien. Per.,' vol. 95, p. 714 (1887). 



ft ' Wied. Ann.,' vol. 31, p. 360 (18S7) ; vol. 36, p. 804. 



XX ' Electro-tecknische Zeitschrift,' vol. 9, p. 341. 



§§ ' Wied. Ann.,' vol. 39, p. 619 (1890). 



I, £ Phil. Mag.,' vol. 2, p. 488 (1891). 



ft ' Phil. Mag.,' toI. 1, p. 243 (1898). 



*** ' Roy. Soc. Proc.,' 1900, vol. 67. 



