286 Mr. H. Tomlinson on the Effect of Magnetization 



The data in this table refer to the effects of temporary 

 magnetization ; and in the case of iron, steel, and nickel, 

 represent only verifications and extensions of the labours of 

 previous observers. Abraham, Edlund, Mousson, and Wart- 

 mann all made search for magnetic alteration of the resistance 

 of iron. W. Thomson * seems, however, to have been the first 

 to arrive at any definite result. He found the resistance to be 

 increased along the lines of magnetization and decreased 

 across them. W. Thomson has been followed by Beetz f, Tom- 

 linson %, Chwolson§, Auerbach||, and De LucchiH. These 

 have all confirmed the results of Thomson so far as longitu- 

 dinal magnetization is concerned ; but Beetz failed to obtain 

 anything but negative results with transverse magnetization, 

 and attributed the decrease of resistance observed by Thomson 

 to mere mechanical pull. The author has, however, pointed 

 out** the improbability of this last supposition. W. Thomson 

 had also previously proved |f that the electrical resistance of 

 nickel is increased to a greater extent than that of ironbylongi- 

 dinal magnetization; whilst Faeff has recently verified the 

 author's result concerning cobalt. Lastly, Goldhammer§§ has 

 published a comparative study of the three paramagnetic 

 metals — iron, cobalt, and nickel, and of the three diamagnetic 

 metals — bismuth, antimony, and tellurium || || . 



There are several points in the table given above to which 

 it is desirable to direct attention. In the first place the resist- 

 ance of all the metals is increased by longitudinal magnetization. 

 In the second it by no means always follows that the metals 

 which possess the greatest magnetic susceptibility are those 

 which are most affected in their conductivity by a given 

 amount of magnetizing-stress. We see, for instance, from 



Ay 

 the third and fourth columns, that whilst the value of -^ for 

 ; rMf 



nickel is twice that for iron, the magnetic susceptibility of 



iron is between three and four times as great as that of nickel. 



It is, however, when we come to consider the fifth column 



that we meet with the most remarkable differences in the 



* " Electrodynamic Qualities of Metals," Phil. Trans. 1856, Part iv. 

 t Pogg. Ami. vol. cxxviii. (1886). 

 } Proc. Roy. Soc. vol. xxiii. (1875). Also loc. cit. 

 § Carl's Rep. vol. xiii. (1877). || Phil. Mag. vol. viii. (1879). 



% Atti del R. 1st. Veneto, viii. (1882). ** Loc. cit. pp. 16-5, 166. 



ft Proc. Roy. Soc. vol. viii. (1857). \\ Atti del R. 1st. Veneto, 1887. 

 §§ Wied. Ann. xxxi. (1887). 



|| || See also a rneinoir, entitled "An Experimental Study of the Influence 

 of Magnetism and Temperature on the Electrical Resistance of Bismuth 

 and its Alloys with Lead and Tin," by Edmond von Auhel. Phil. Mag. 

 p. 191 of the present volume. 



