of equal velocity about these orbs as
distant centres; and the revolution thus engendered must proceed, so
long as the centripetal force, or that with which the discarded body
gravitates toward its parent, is neither greater nor less than that by
which it was discarded; that is, than the centrifugal, or, far more
properly, than the tangential, velocity. From the unity, however, of the
origin of these two forces, we might have expected to find them as they
are found--the one accurately counterbalancing the other. It has been
shown, indeed, that the act of whirling-off is, in every case, merely an
act for the preservation of the counterbalance.

After referring, however, the centripetal force to the omniprevalent law
of Gravity, it has been the fashion with astronomical treatises, to seek
beyond the limits of mere Nature--that is to say, of _Secondary_ Cause--a
solution of the phaenomenon of tangential velocity. This latter they
attribute directly to a _First_ Cause--to God. The force which carries a
stellar body around its primary they assert to have originated in an
impulse given immediately by the finger--this is the childish phraseology
employed--by the finger of Deity itself. In this view, the planets, fully
formed, are conceived to have been hurled from the Divine hand, to a
position in the vicinity of the suns, with an impetus mathematically
adapted to the masses, or attractive capacities, of the suns themselves.
An idea so grossly unphilosophical, although so supinely adopted, could
have arisen only from the difficulty of otherwise accounting for the
absolutely accurate adaptation, each to each, of two forces so seemingly
independent, one of the other, as are the gravitating and tangential.
But it should be remembered that, for a long time, the coincidence
between the moon's rotation and her sidereal revolution--two matters
seemingly far more independent than those now considered--was looked
upon as positively miraculous; and there was a strong disposition, even
among astronomers, to attribute the marvel to the direct and continual
agency of God--who, in this case, it was said, had found it necessary to
interpose, specially, among his general laws, a set of subsidiary
regulations, for the purpose of forever concealing from mortal eyes the
glories, or perhaps the horrors, of the other side of the Moon--of that
mysterious hemisphere which has always avoided, and must perpetually
avoid, the telescopic scrutiny of mank