24 Voltaic Induction. 



factory results upon the subject. The difficulty of investigation 

 arose, chiefly, from the peculiar manner in which the magnetic forces 

 exhibit themselves j for, instead of acting in right lines, across or 

 parallel to the current, as might have been anticipated from a knowl- 

 edge of other forces, they invariably revolve in planes at right angles 

 to the current, so as to act tangentially upon bodies placed within 

 their influence. The opposite forces move against each other, and 

 exhibit no tendency to interfere with each other's movement as long 

 as the voltaic circulation continues. It is well known, also, that this 

 singular manifestation, so different from that of any other kind of at- 

 traction and repulsion, soon became, in the hands of Ampere, the 

 means of illustrating the construction and action of artificial magnets. 

 The merit of discovery has, indeed, become almost obliterated by 

 the brilliant results of subsequent research ; although it is apparent 

 that most of them must be regarded as merely illustrations of Oer- 

 sted's first observations upon the five positions which a magnetized 

 needle assumes, when placed near a voltaic current. The position 

 of equilibrium to which the needle, in all cases, tends, lies exactly in 

 the plane of magnetic revolution, and which itself is at right angles to 

 the voltaic current. All the peculiar movements of the needle result 

 from a disposition to take this direction, and when once in it, the 

 current has no influence or power to invert the needle. Thus, when 

 the needle lies north and south, the pos. current may move towards 

 the east or towards the west, without changing its position. Hence 

 both the magnetic forces revolve in the same plane, accurately, and 

 at right angles to the current. Whether they are generated simul- 

 taneously in every part of the circuit, or rapidly propelled from one 

 of the voltaic elements towards the other, cannot be determined ; but 

 there is some reason for believing that their distribution is unequal as 

 to intensity, for very fine iron dust, as Mr. Watkins has shown, when 

 sifted upon the circuit wire, arranges itself in distinct bands across it. 

 Magnetic forces revolving so independently of each other, must be 

 under the influence of a common central attraction, either existing in 

 the voltaic current, or the matter through which it passes. It is prob- 

 able, therefore, that the curve they describe is an ellipse, and not a 

 circle. Incessant rotation, while the forces are free to move, is emi- 

 nently characteristic of magnetism, and such must be its existence in 

 magnetised steel, according to the theory of Ampere, founded upon 

 the electro-dynamic cylinder. Whether we regard their develope- 

 ment as depending upon a pre-existing voltaic current, or not, it is 



