THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



NOVEMBER 1874. 



XLVI. On the Magnetic Permeability and Maximum of Magne- 

 tism of Nickel and Cobalt. By Henry A. Rowland, C.E.* 



SOME time ago a paper of mine on the magnetic permeabi- 

 lity of iron, steel, and nickel was published in the Philo- 

 sophical Magazine (August 1873) ; and the present paper is to 

 be considered as a continuation of that one. But before pro- 

 ceeding to the experimental results, I should like to make a few 

 remarks on the theory of the subject. The mathematical theory 

 of magnetism and electricity is at present developed in two radi- 

 cally different manners, although the results of both methods of 

 treatment are in entire agreement with experiment as far as we 

 can at present see. The first is the German method ; and the 

 second is Faraday's, or the English method. When two mag- 

 nets are placed near each other, we observe that there is a mu- 

 tual force of attraction or repulsion between them. Now, accord- 

 ing to the German philosophers, this action takes place at a dis- 

 tance without the aid of any intervening medium : they know that 

 the action takes place, and they know the laws of that action ; but 

 there they rest content, and seek not to find how the force tra- 

 verses the space between the bodies. The English philosophers, 

 however, led by Newton, and preeminently by Faraday, have 

 seen the absurdity of the proposition that two bodies can act 

 upon each other across a perfectly vacant space, and have 

 attempted to explain the actio a by some medium through which 

 the force can be transmitted along what Faraday has called 

 " lines of force/' 



These differences have given rise to two different ways of look- 



* Communicated by Professor J. Clerk Maxwell, M.A., F.R.S. 

 Phil Mag. S. 4. Vol. 48. No. 319. Nov. 1874. Y 



