A revolving
fluid will continue to change its shape, till it attains that in which
its principles of contrary motion are balanced. For if you suppose them
not balanced, it will change its form. Now the same balanced form
is necessary for the preservation of a revolving solid. The creator,
therefore, of a revolving solid, would make it an oblate spheroid, that
figure alone admitting a perfect equilibrium. He would make it in that
form, for another reason; that is, to prevent a shifting of the axis of
rotation. Had he created the earth perfectly spherical, its axis might
have been perpetually shifting, by the influence of the other bodies
of the system; and by placing the inhabitants of the earth successively
under its poles, it might have been depopulated; whereas, being
spheroidical, it has but one axis on which it can revolve in equilibrio.
Suppose the axis of the earth to shift forty-five degrees; then cut it
into one hundred and eighty slices, making every section in the plane
of a circle of latitude, perpendicular to the axis: every one of these
slices, except the equatorial one, would be unbalanced, as there would
be more matter on one side of its axis than on the other.
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