the magnet really exert no influence on the pole presented to
its centre? Let us see.

Let SN, fig. 13, be our magnet, and let n represent a particle of
north magnetism placed exactly opposite the middle of the magnet. Of
course this is an imaginary case, as you can never in reality thus
detach your north magnetism from its neighbour. But supposing us to
have done so, what would be the action of the two poles of the magnet
on n? Your reply will of course be that the pole S attracts n while
the pole N repels it. Let the magnitude and direction of the
attraction be expressed by the line n m, and the magnitude and
direction of the repulsion by the line n o. Now, the particle n being
equally distant from s and N, the line n o, expressing the repulsion,
will be equal to m n, which expresses the attraction. Acted upon by
two such forces, the particle n must evidently move in the direction n
p, exactly midway between m n and n o. Hence you see that, although
there is no tendency of the particle n to move towards the magnetic
equator, there is a tendency on its part to move parallel to the
magnet. If, instead of a particle of north magnetism, we placed a
particle of south magnetism opposite to the magnetic equator, it would
evidently be urged along the line n q; and if, instead of two separate
particles of magnetism, we place a little magnetic needle, containing
both north and south magnetism, opposite the magnetic equator, its
south pole being urged along n q, and its north along n p, the little
needle will be compelled to set itself parallel to the magnet s N.
Make the experiment, and satisfy yourselves that this is a true
deduction.

Substitute for your magnetic needle a bit of iron wire, devoid of
permanent magnetism, and it will set itself exactly as the needle
does. Acted upon by the magnet, the wire, as you know, becomes a
magnet and behaves as such; it will turn its north pole towards p, and
south pole towards q, just like the needle.

But supposing you shift the position of your particle of north
magnetism, and bring it nearer to one end of your magnet than to the
other; the forces acting on the particle are no longer equal; the
nearest pole of the magnet will act more powerfully on the particle
than the more distant one. Let SN, fig. 14, be the magnet, and n the
particle of north magnetism, in its new position. It is repelled by
N, and attracted by S. Let the repulsion be represented in magnitude
and