338 PLUCKER ON THE THEORY OF DI AMAGNETISM. 



a north pole excites a south pole and a south pole a north pole, 

 in its immediate neighbourhood. 



From this way of viewing the subject, the repulsion of the mass 

 of bismuth by the pole of a magnet is explained in exactly the 

 same manner as the attraction of the mass of iron by the same. 

 While in one case the excited pole is always a friendly one, in 

 the other it is hostile. 



In like manner, the equatorial position assumed by a bar of 

 bismuth, in opposition to the axial position assumed by a bar of 

 iron, is easily explainable. For each bar we have two positions 

 of equilibrium ; the axial and the equatorial. Where both bars 

 rotate, the distribution of the magnetism is perpetually chan- 

 ging ; in the axial position both bars are longitudinal magnets ; 

 in the equatorial position both are transversal magnets. In both 

 cases the bar of iron turns the friendly pole, and the bismuth the 

 hostile pole to the electro-magnet. For the bar of iron the axial 

 position, where its ends are the poles, is the position of stable 

 equilibrium, the equatorial position that of MW5/«6/e equilibrium. 

 For the bismuth bar, the contrary holds good ; the equatorial 

 position, where the poles are drawn out as it were into straight 

 lines, is that of stable equilibrium, and the axial that of un- 

 stable equilibrium. 



The induction now under consideration is that by which, accord- 

 ing to Ampere, elementary currents are excited round the ulti- 

 mate particles of bodies, which as long as the excitation con- 

 tinues remain unchanged, or which, if we assume the currents as 

 already existing, imparts to them a single or at least one predo- 

 minant direction which they did not possess originally. In 

 magnetic bodies the induced molecular currents have the same 

 direction as the molecular currents of the inducing pole or the 

 current in the inducing spiral : in diamagnetic bodies the direc- 

 tion is the opposite. 



[I repress here the statement and discussion of the manifold 

 experiments in which with mixed bodies the magnetic deport- 

 ment passes over into the diamagnetic. From these I have 

 deduced the empirical, and as such incontrovertible law, " that 



