Prof. Faraday on some Points of Magnetic Philosophy. 103 



the copper within the constant influence of the magnet has a 

 permanent, static, magnetic condition ; and is therefore a mag- 

 netic medium, having lines of force passing through it. If C 

 be of bismuth instead of coppei', the same currents in the same 

 direction occur, though in a far smaller degree; and, as it is 

 believed, only because of deficiency in its conducting power. 



3340. There can be no doubt that very much is involved in 

 these phsenomena, of the nature of which we have little or no 

 knowledge ; and the results obtained by Matteucci will probably 

 lead to developments and discoveries of great importance. He 

 states* that copper, when finely divided, presents very persisting 

 phaenomena, proving its right to be considered as a diamagnetic 

 body ; but that when aggregated, all, or nearly all, its diamag- 

 netic character disappears. Nothing is known as yet of the 

 manner in which the mere difference of cohesion or division 

 can so affect the diamagnetic character. He finds, too, that in 

 other respects, as in Arago's rotation, particles of matter act in 

 a manner not to be anticipated from what is at present known 

 of them as masses ; and it is to be hoped and expected that 

 when these results are enlarged and developed, we shall be able 

 to form a better judgement of the true physical action of mag- 

 netism than at present. 



Places of no magnetic action. 



3341. The essential relation and dependence of the two mag- 

 netic dualities is manifested, I think, in a very striking manner, 

 by the results which occur when we attempt to isolate northness 

 or southness, by concentrating either of them on one space or 

 piece of matter, and looking for their presence by effects, either 

 of tension or any other kind, whether connected with polarity 

 or not. A soft iron bar, an inch square, 3 or 4 inches long and 

 rounded at the edges, had thirty-two convolutions of covered 

 copper wire 0*05 of an inch in diameter put round it, so that 

 covering the middle part of the bar, chiefly, it could be shifted 

 if needful a little nearer to one end than the other ; such a bar 

 could be rendered magnetic by an electric 

 current passed through the wire, and a 

 degree of adjustment, in the strength of 

 the N and S extremities, could be effected 

 by this motion of the iron in its helix. 

 Having six of these, it was easy to arrange 

 them with their like poles together, so as to 

 include a cubical space or chamber, fig. 9 ; 

 and in this space I worked by every means 

 at my disposal. Access to it was easily 

 obtained by a previous removal of a portion of the solid angles 



* Court special iwr Pindmction, fyc, 1864. pp. 165, 2fi9. 



