"
In view of such observations as that of Prof. E.E. Barnard, in 1892,
showing that a satellite passing through the shadow of Saturn's rings
does not entirely disappear--a fact which proves that the rings are
partially transparent to the sunlight--one might be tempted to ask
whether Saturn itself, considering its astonishing lack of density, is
not composed, at least in its outer parts, of separate particles of
matter revolving independently about their center of attraction, and
presenting the appearance of a smooth, uniform shell reflecting the
light of the sun. In other words, may not Saturn be, exteriorly, a globe
of dust instead of a globe of vapor? Certainly the rings, incoherent and
translucent though they be, reflect the sunlight to our eyes, at least
from the brighter part of their surface, with a brilliance comparable
with that of the globe of the planet itself.
As bearing on the question of the interior condition of Saturn and
Jupiter, it should, perhaps, be said that mathematical considerations,
based on the figures of equilibrium of rotating liquid masses, lead to
the conclusion that those planets are comparatively very dense within.
Professor Darwin puts the statement very strongly, as follows: "In this
way it is known with certainty that the central portions of the planets
Jupiter and Saturn are much denser, compared to their superficial
portions, than is the case with the earth."[13]
[Footnote 13: The Tides, by G.
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