THE EARTH AS A MAGNET.--The earth is a huge magnet and the magnetic
lines run from the north pole to the south pole around all sides of the
globe.

[Illustration: _Fig. 8._ HORSESHOE MAGNET]

The north magnetic pole does not coincide with the true north pole or
the pivotal point of the earth's rotation, but it is sufficiently near
for all practical purposes. Fig. 9 shows the magnetic lines running from
the north to the south pole.

WHY THE COMPASS POINTS NORTH AND SOUTH.--Now, let us try to ascertain
why the compass points north and south.

Let us assume that we have a large magnet (A, Fig. 10), and suspend a
small magnet (B) above it, so that it is within the magnetic field of
the large magnet. This may be done by means of a short pin (C), which is
located in the middle of the magnet (B), the upper end of this pin
having thereon a loop to which a thread (D) is attached. The pin also
carries thereon a pointer (E), which is directed toward the north pole
of the bar (B).

[Illustration: _Fig. 9._ EARTH'S MAGNETIC LINES]

You will now take note of the interior magnetic lines (X), and the
exterior magnetic lines (Z) of the large magnet (A), and compare the
direction of their flow with the similar lines in the small magnet (B).

The small magnet has both its exterior and its interior lines within the
exterior lines (Z) of the large magnet (A), so that as the small magnet
(B) is capable of swinging around, the N pole of the bar (B) will point
toward the S pole of the larger bar (A). The small bar, therefore, is
influenced by the exterior magnetic field (Z).

[Illustration: _Fig. 10._ TWO PERMANENT MAGNETS]

[Illustration: _Fig. 11._ MAGNETS IN THE EARTH'S MAGNETIC FIELD]

Let us now take the outline represented by the earth's surface (Fig.
11), and suspend a magnet (A) at any point, like the needle of a
compass, and it will be seen that the needle will arrange itself north
and south, within the magnetic field which flows from the north to the
south pole.

PECULIARITY OF A MAGNET.--One characteristic of a magnet is that, while
apparently the magnetic field flows out at one end of the magnet, and
moves inwardly at the other end, the power of attraction is just the
same at both ends.

In Fig. 12 are shown a bar (A) and a horseshoe magnet (B). The bar (A)
has metal blocks (C) at each end, and each of these blocks is attracted
to and held in contact with the ends by magnetic influence, just the
same as the bar (D) i