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 ; for, instead of acting in right lines, aeross 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 Ampére, 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 
