In a word, Jupiter
seems to be in the last stage of stellar development. Such, at
some remote time, was our earth; such one day will be the sun.
The neighbouring planet Saturn supports the conclusion. Here
again we have a gigantic globe, 28,000 miles in diameter, turning
on its axis in the short space of ten hours; and here again we
find the conspicuous flattening of the poles, the trailing belts
of massed vapour across the disk, the red glow lighting the edges
of the belts, and the spectroscopic evidence of an emission of
light. Once more it is difficult to doubt that a highly heated
body is wrapped in that thick mantle of vapour. With its ten
moons and its marvellous ring-system--an enormous collection of
fragments, which the influence of the planet or of its nearer
satellites seems to have prevented from concentrating--Saturn has
always been a beautiful object to observe; it is not less
interesting in those features which we faintly detect in its
disk.
The next planet, Uranus, 32,000 miles in diameter, seems to be
another cloud-wrapt, greatly heated globe, if not, as some think,
a sheer mass of vapours without a liquid core. Neptune is too dim
and distant for profitable examination.
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