H. Darwin, p. 333.]
The globe and rings of Saturn witness an imposing spectacle of gigantic
moving shadows. The great ball stretches its vast shade across the full
width of the rings at times, and the rings, as we have seen, throw their
shadow in a belt, whose position slowly changes, across the ball,
sweeping from the equator, now toward one pole and now toward the
other. The sun shines alternately on each side of the rings for a space
of nearly fifteen years--a day fifteen years long! And then, when that
face of the ring is turned away from the sun, there ensues a night of
fifteen years' duration also.
Whatever appearance the rings may present from the equator and the
middle latitudes on Saturn, from the polar regions they would be totally
invisible. As one passed toward the north, or the south, pole he would
see the upper part of the arch of the rings gradually sink toward the
horizon until at length, somewhere in the neighborhood of the polar
circle, it would finally disappear, hidden by the round shoulder of the
great globe.
URANUS, NEPTUNE, AND THE SUSPECTED ULTRANEPTUNIAN PLANET
What has been said of Jupiter and Saturn applies also to the remaining
members of the Jovian group of planets, Uranus and Neptune, viz., that
their density is so small that it seems probable that they can not, at
the present time, be in a habitable planetary condition. All four of
these outer, larger planets have, in comparatively recent times, been
solar orbs, small companions of the sun.
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