found that there is a second north pole in northern Siberia. Its
location has not, however, been so well determined as in the case
of the American pole, and it is not yet satisfactorily shown that
there is any one point in Siberia where the direction of the force
is exactly downward.

[Illustration with caption: DIP OF THE MAGNETIC NEEDLE IN VARIOUS
LATITUDES. The arrow points show the direction of the north end of
the magnetic needle, which dips downward in north latitudes, while
the south end dips in south latitudes.]

The declination and dip, taken together, show the exact direction
of the magnetic force at any place. But in order to complete the
statement of the force, one more element must be given--its
amount. The intensity of the magnetic force is determined by
suspending a magnet in a horizontal position, and then allowing it
to oscillate back and forth around the suspension. The stronger
the force, the less the time it will take to oscillate. Thus, by
carrying a magnet to various parts of the world, the magnetic
force can be determined at every point where a proper support for
the magnet is obtainable. The intensity thus found is called the
horizontal force. This is not really the total force, because the
latter depends upon the dip; the greater the dip, the less will be
the horizontal force which corresponds to a certain total force.
But a very simple computation enables the one to be determined
when the value of the other is known. In this way it is found
that, as a general rule, the magnetic force is least in the
earth's equatorial regions and increases as we approach either of
the magnetic poles.