of the inner ring is more distinct seems to indicate that
the approach towards the planet is less rapid near the
edge, as we had reason to conjecture. As to the apparent
unchangeableness of the exterior diameter of
the outer ring, we must remember that the outer rings
are certainly far more dense than the inner one, and
that a small change in the outer rings must balance a
great change in the inner one. It is possible, however,
that some of the observed changes may be due
to the existence of a resisting medium. If the changes
already suspected should be confirmed by repeated
observations with the same instruments, it will be
worth while to investigate more carefully whether
Saturn's rings are permanent or transitory elements
of the solar system, and whether in that part of the
heavens we see celestial immutability or terrestrial
corruption and generation, and the old order giving
place to the new before our eyes."[4]


Studies of the Moon

But perhaps the most interesting accomplishments
of mathematical astronomy--from a mundane standpoint,
at any rate--are those that refer to the earth's
own satellite. That seemingly staid body was long
ago discovered to have a propensity to gain a little on
the earth, appearing at eclipses an infinitesimal moment
ahead of time. Astronomers were sorely puzzled
by this act of insubordination; but at last Laplace and