ON THE MAGNETIC PEEMEABILITY AND MAXIMUM OF 

 MAGNETISM OF NICKEL AND COBALT 



[Philosophical Magazine [4], XL VIII, 321-340, 1874J 



Some time ago a paper of mine on the magnetic permeability of iron, 

 steel, and nickel was published in the Philosophical Magazine (August, 

 1873); and the present paper is to be considered as a continuation of 

 that one. But before proceeding to the experimental results, I should 

 like to make a few remarks on the theory of the subject. The mathe- 

 matical theory of magnetism and electricity is at present developed in 

 two radically 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 magnets are placed near 

 each other, we observe that there is a mutual force of attraction or 

 repulsion between them. Now, according to the German philosophers, 

 this action takes place at a distance 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 traverses 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 ex- 

 plain the action by some medium through which the force can be trans- 

 mitted along what Faraday has called " lines of force." 



These differences have given rise to two different ways of looking 

 upon magnetic induction. Thus if we place an electromagnet neat" a 

 compass-needle, the Germans would say that the action was due in part 

 to two causes the attraction of the coil, and the magnetism induced in 

 the iron by the coil. Those who hold Faraday's theory, on the other 

 hand, would consider the substance in the helix as merely " conduct- 

 ing " the lines of force, so that no action would be exerted directly on 

 the compass-needle by the coil, but the latter would only affect it in 

 virtue of the lines of force passing along its interior, and so there could 

 be no attraction in a perfectly vacant space. 



