408 Dr. Faraday on the Physical Character of 



3258. But supposing this necessary relation, which constitutes 

 polarity, to exist, then how is it sustained, or permitted in the 

 case of an independent bar-magnet situated in free space ? It 

 appears to me, that the outer forces at the poles can only have 

 relation to each other by curved lines of force through the sur- 

 rounding space; and I cannot conceive curved lines of force 

 without the conditions of a physical existence in that interme- 

 diate space. If they exist, it is not by a succession of particles, 

 as in the case of static electric induction (1215. 1231.), but by 

 the condition of space free from such material particles. A mag- 

 net placed in the middle of the best vacuum we can produce, 

 and whether that vacuum be formed in a space previously occu- 

 pied by paramagnetic or diamagnetic bodies, acts as well upon 

 a needle as if it were surrounded by air, water or glass ; and 

 therefore these lines exist in such a vacuum as well as where 

 there is matter. 



3259. It may perhaps be said that tbere is no proof of any 

 outer lines of force, in the case of a magnet, except when the 

 objects employed experimentally to show these lines, as a mag- 

 netic needle, soft iron, a moving wire, or a crystal of bismuth, 

 are present ; that these bodies, in fact, cause and develope the 

 lines ; just as in the case of gravity no idea of a line of gravita- 

 ting force, in respect of a particle of matter by itself, can be 

 formed : the idea exists only when a second particle is concerned. 

 We are dealing, however, with a dual power ; and we know that 

 we cannot call into action, by magnetic induction upon soft iron 

 or by electric currents, or otherwise, one magnetism without the 

 other. Supposing, therefore, a bar of soft iron, or another bar- 

 magnet, when brought end on and near to the first magnet, did 

 by that approach develope the external force, the power which 

 then only would become external should produce a corresponding 

 external force of the contrary kind at the opposite extremity, or 

 should not. If the first case occurs, it should be accompanied 

 by the development of lines of force equivalent to it within the 

 magnet. But I think we know, now, that in a very hard and 

 perfect magnet there is no change of this kind (3223.). The outer 

 and the inner lines of force remain the same in amount, whether 

 the secondaiy magnet or the soft iron is present or away. It is 

 the disposition only of the outer lines that is changed ; their sum, 

 and therefore their existence, remains the same. If the second 

 case occurs, then the magnet, if broken in half under induction, 

 should present in its fragments cases of absolute magnetic charge, 

 or charge with one magnetism only (3257. 3261.). 



3260. Or if it be imagined for a moment, that the two polarities 

 of the bar- magnet are in relation to each other, but that whilst 

 there is no external object to be acted upon they are related to 



