exceeds that of all the other planets,
even Jupiter. It follows that its equatorial diameter is 112,500
kilometers (69,750 miles), while its polar diameter measures only
110,000 kilometers (68,200).

In volume, Saturn is 719 times larger than the Earth, but its density is
only 128/1000 of our own; _i.e._, the materials of which it is composed
are much less heavy, so that it weighs only 92 times more than our
Earth. Its surface is 85 times vaster than that of the Earth, no
insignificant proportion.

[Illustration: FIG. 47.--Saturn.]

The dipping of Saturn's axis of rotation is much the same as our own.
Hence we conclude that the seasons of this planet are analogous to ours
in relative intensity. Only upon this far-off world each season lasts
for seven years. At the distance at which it gravitates in space, the
heat and light which it receives from the Sun are 90 times less active
than such as reach our selves; but it apparently possesses an atmosphere
of great density, which may be constituted so that the heat is
preserved, and the planet maintained in a calorific condition but little
inferior to our own.

In the telescope, the disk of Saturn exhibits large belts that recall
those of Jupiter, though they are broader and less accentuated (Fig.
47). There are doubtless zones of clouds or rapid currents circulating
in the atmosphere. Spots are also visible whose displacement assists in
calculating the diurnal motions of this globe.

The most extraordinary characteristic of this strange world is, however,
the existence of a vast _ring_, which is almost flat and very large, and
entirely envelops the body of the planet. It is suspended in the
Saturnian sky, like a gigantic triumphal arch, at a height of some
20,000 kilometers (12,400 miles) above the equator. This splendid arch
is circular, like an immense crown illuminated by the Sun. From here we
only see it obliquely, and it appears to us elliptical; a part of the
ring seems to pass in front of Saturn, and its shadow is visible on the
planet, while the opposite part passes behind.

This ring, which measures 284,000 kilometers (176,080 miles) in
diameter, and less than 100 kilometers (62 miles) in breadth, is divided
into three distinct zones: the exterior is less luminous than the
center, which is always brighter than the planet itself; the interior is
very dark, and spreads out like a dusky and faintly transparent veil,
through which Saturn can be distinguished.