ce was found to be the
spreading-out of the rings in breadth, the outer rings pressing outward,
while the inner rings press inward.

"The final result, therefore, of the mechanical theory is that the only
system of rings which can exist is one composed of an indefinite number
of unconnected particles, revolving around the planet with different
velocities, according to their respective distances. These particles
may be arranged in series of narrow rings, or they may move through one
another irregularly. In the first case the destruction of the system
will be very slow, in the second case it will be more rapid, but there
may be a tendency towards arrangement in narrow rings which may retard
the process.

"We are not able to ascertain by observation the constitution of the two
outer divisions of the system of rings, but the inner ring is certainly
transparent, for the limb of Saturn has been observed through it. It is
also certain that though the space occupied by the ring is transparent,
it is not through the material parts of it that the limb of Saturn is
seen, for his limb was observed without distortion; which shows that
there was no refraction, and, therefore, that the rays did not pass
through a medium at all, but between the solar or liquid particles of
which the ring is composed. Here, then, we have an optical argument
in favor of the theory of independent particles as the material of
the rings. The two outer rings may be of the same nature, but not
so exceedingly rare that a ray of light can pass through their whole
thickness without encountering one of the particles.

"Finally, the two outer rings have been observed for two hundred years,
and it appears, from the careful analysis of all the observations of M.
Struve, that the second ring is broader than when first observed, and
that its inner edge is nearer the planet than formerly. The inner ring
also is suspected to be approaching the planet ever since its discovery
in 1850. These appearances seem to indicate the same slow progress of
the rings towards separation which we found to be the result of theory,
and the remark that the inner edge 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 th