round to the other. They are never broken, and apparently they are
lines of stress in the circumambient ether. A pivoted magnet tends
to range itself along these lines, and thus the compass guides the
sailor on the ocean by keeping itself in the line between the
north and south magnetic poles of the earth. Faraday called them
lines of magnetic force, and said that the stronger the magnet the
more of these lines pass through a given space. Along them
"magnetic induction" is supposed to be propagated, and a magnet is
thus enabled to attract iron or any other magnetic substance. The
pole induces an opposite pole to itself in the nearest part of the
induced body and a like pole in the remote part. Consequently, as
unlike poles attract and like repel, the soft iron is attracted by
the inducing pole much as a pithball is attracted by an electric
charge.

The resemblances of electricity and magnetism did not escape
attention, and the derangement of the compass needle by the
lightning flash, formerly so disastrous at sea, pointed to an
intimate connection between them, which was ultimately disclosed
by Professor Oersted, of Copenhagen, in the year 1820. Oersted was
on the outlook for the required clue, and a happy chance is said
to have rewarded him. His experiment is shown in figure 29, where
a wire conveying a current of electricity flowing in the direction
of the arrow is held over a pivoted magnetic needle so that the
current flows from south to north. The needle will tend to set
itself at right angles to the wire, its north or north-seeking
pole moving towards the west. If the direction of the current is
reversed, the needle is deflected in the opposite direction, its
north pole moving towards the east. Further, if the wire is held
below the needle, in the first place, the north pole will turn