s of pressure,
when these planes are suspended horizontally, the directive force is
greatest, and the longest diameter of the body sets axial. On the other
hand, when the body was suspended so that the laminae were vertical, the
longest diameter set equatorial. Now, we know that the crust of the
earth is composed of laminae, just as the piece of shale in Doctor
Tyndal's experiments, and that these layers are disposed horizontally.
And whatever force originally arranged the land and water on our globe,
it is evident that the continents are longest from north to south, and
therefore correspond to the natural direction of the magnetic force.

In consequence of the intrinsic difficulties of this question, and the
mystery yet attaching to it, we may be permitted to enter a little more
minutely into it, and jointly consider other questions of interest, that
will enable us to refer the principal phenomena of terrestrial magnetism
to our theory.

We have before adverted to the discrepancies in the earth's compression,
as determined by the pendulum, and also to the uncertainty of the moon's
mass, as deduced from the nutation of the earth's axis. It is also
suspected that the southern hemisphere is more compressed than the
northern; and other phenomena also point out the inadequacy of the law
of gravitation, to account for the figure of the earth.

From the invariability of the axis of rotation, we must conclude that
whatever form is the true form, it is one of equilibrium. In casting our
eyes over the map of the world, we perceive that the surface is very
unequally divided into land and sea; and that the land is very unequally
arranged, both north and south, and east and west. If we compare the
northern and southern hemisphere, we find the land to the water about 3
to 1. If we take the Pacific portion, and consider the north end of New
Zealand as a centre, we can describe a great circle taking in one half
the globe, which shall not include one-tenth of the whole land. Yet the
average height of the remaining nine-tenths, above the level of the sea,
is nearly 1,000 feet. Call this nine-tenths nearly equal to one-fourth
of the whole surface, and the protuberant land in the hemisphere,
opposite the South Pacific, amounts to 1/30,000 part of the whole mass
of the earth, or about 1/700 of the mass of the moon. Again, the mean
density of the earth is about 5 1/2--water being unity,--and the mean
density of the surface land is only ab