BKCT. XXXII. ACTION OF ELECTRIC CURRENTS. 321 



which bodies possess derive these properties from cur- 

 rents of electricity circulating about every part in one 

 uniform direction. Although every particle of a magnet 

 possesses like properties with the whole, yet the general 

 effect is the same as if the magnetic properties were 

 confined to the surface. Consequently the internal elec- 

 tro-currents must compensate one another, and there- 

 fore the magnetism of a body is supposed to arise from 

 a superficial current of electricity constantly circulating 

 in a direction perpendicular to the axes of the magnet; 

 so that the reciprocal action of magnets, and all the phe- 

 nomena of electro-magnetism, are reduced to the action 

 and reaction of superficial currents of electricity acting 

 at right angles to then* direction. Notwithstanding the 

 experiments made by M. Ampere to elucidate the sub- 

 ject, there is still an uncertainty in the theory of the 

 induction of magnetism by an electric current in a body 

 near it. It does not appear whether electric currents 

 which did not previously exist are actually produced by 

 induction, or if its effects be only to- give one uniform 

 direction to the infinite number of electric currents pre- \ 

 viously existing in the particles of the body, and thus 

 rendering them capable of exhibiting magnetic phenom- 

 ena, in the same manner as polarization reduces those 

 undulations of light to one plane which had previously 

 been performed in every plane. Possibly both may be 

 combined in producing the effect ; for the action of an 

 electric current may not only give a common direction 

 to those already existing, but may also increase their 

 intensity. However that may be, by assuming that the 

 attraction and repulsion of the elementary portions of 

 electric currents vary inversely as the squares of the 

 distances, the action being at right angles to the direc- 

 tion of the current, it is found that the attraction and 

 repulsion of a current of indefinite length on the ele- 

 mentary portion of a parallel current at any distance 

 from it, is in the simple ratio of the shortest distance 

 between them. Consequently the reciprocal action of 

 electric currents is reduced to the composition and res- 

 olution of forces, so that the phenomena of electro-mag- 

 netism are brought under the laws of dynamics by the 

 theory of M. Ampere. 

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