o forces,
and which is such as would have been assumed by a fluid body actuated by
them. The figure that fulfils these conditions is an oblate spheroid,
the axis of the generating ellipse coinciding with the polar diameter of
the body. Had the earth a figure absolutely spherical, or less flattened
than is consistent with the conditions of equilibrium, the ocean, by
which so large a part of its surface is covered, would have arranged
itself in a meniscoid zone around its equatorial regions; were the
figure, on the other hand, one of greater oblateness, the waters would
have been divided and accumulated at either pole, leaving the
equatorial regions dry. But did its figure fulfil the conditions of
equilibrium, the fluid mass would tend to distribute itself equally over
the whole surface, unless prevented by irregularities in the solid mass.
The last is the actual state of things; the ocean occupies a bed formed
of cavities, lying below the mean surface of the spheroid, and the land
presents to us those asperities and elevations, which rise, although to
a comparatively small height, above the general level.

Was then the earth originally in a fluid state, and has it assumed its
present form under the strict action of mechanical laws, on a body of
that class? are the bed of the ocean and the continents merely crusts
formed upon the surface of a liquid globe? Does the interior still
remain liquid, or has the induration proceeded until the whole internal
mass has become solid? Nay, may not the interior be hollow, as we have
recently seen gravely maintained, and heard sage legislatures recommend
to the public attention?

Mathematical investigations of incontrovertible evidence, show us that
were the earth of equal density throughout, the flattening at the poles
would be 1/234 of the equatorial diameter; that in the hypothetical case
of infinite density at the centre, and infinite rarity at the surface,
the flattening would be no more than 1/578; while, were the surface more
dense than the interior, or did a cavity exist within, the oblateness
must be greater than 1/234. Actual measurements of portions of the
surface, the variation in the length of the pendulum which beats seconds
in different latitudes, and the effect of the earth's figure on the
lunar motions, show us that the earth cannot be flattened more than
1/289, nor less than 1/312, or may, at a mean, be considered as a
spheroid, whose polar and equatorial diameters a