Instead, as in all other
satellites, of having their orbits but slightly inclined toward the ecliptic
and (not excepting even Saturn's ring, which may be regarded as a fusion of
agglomerated satellites) moving from west to east, the satellites of Uranus
are almost perpendicular to the ecliptic, and move retrogressively from east
to west, as Sir John Herschel has proved by observations continued during
many years. If the primary and secondary planets have been formed by the
condensation of rotating rings of solar and planetary atmospheric vapor,
there must have existed singular causes of retardation or impediment in the
vaporous rings revolving round Uranus, by which, under the relations with
which we are unacquainted, the revolution of the second and fourth of its
satellites was made to assume a direction opposite to that of the rotation
of the central planet.
It seems highly probable that the period of rotation of 'all' secondary
planets is equal to that of their revolution round the main planet, and
therefore that they always present to the latter the same side.
Inequalities, occasioned by sight variations in the revolution, give rise to
fluctuations of from 6 degrees to 8 degrees, or to an apparent libration in
longitude as well as in latitude.
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