equal in bulk to Saturn, would
actually weigh more. If we could conceive a vast ocean into which a
globe equal to Saturn in size and weight were cast, the great globe
would not sink like our earth or like any of the other planets; it would
float buoyantly at the surface with one-fourth of its bulk out of the
water.

We thus learn with high probability that what our telescopes show upon
Saturn is not a solid surface, but merely a vast envelope of clouds
surrounding a heated interior. It is impossible to resist the suggestion
that this planet, like Jupiter, has still retained its heat because its
mass is so large. We must, however, allude to a circumstance which
perhaps may seem somewhat inconsistent with the view here taken. We have
found that Jupiter and Saturn are, both of them, much less dense than
the earth. When we compare the two planets together, it appears that
Saturn is much less dense than Jupiter. In fact, every cubic mile of
Jupiter weighs nearly twice as much as each cubic mile of Saturn. This
would seem to point to the conclusion that Saturn is the more heated of
the two bodies. Yet, as Jupiter is the larger, it might more reasonably
have been expected to be hotter than the other planet. We do not attempt
to reconcile this discrepancy; in fact, in our ignorance as to the
material constitution of these bodies, it would be idle to discuss the
question.

Even if we allow for the lightness of Saturn, as compared bulk for bulk
with the earth, yet the volume of Saturn is so enormous that the planet
weighs more than ninety-five times as much as the earth. The adjoining
view represents the relative sizes of Saturn and the earth (Fig. 65).

[Illustration: Fig. 65.--Relative Sizes of Saturn and the Earth.]

As the unaided eye discloses none of those marvels by which Saturn is
surrounded, the interest which attaches to this planet may be said to
commence from the time when it began to be observed with the telescope.
The history must be briefly alluded to, for it was only by degrees that
the real nature of this complicated object was understood. When Galileo
completed his little refracting telescope, which, though it only
magnified thirty times, was yet an enormous addition to the powers of
unaided vision, he made with it his memorable review of the heavens. He
saw the spots on the sun and the mountains on the moon; he noticed the
crescent of Venus and the satellites of Jupiter. Stimulated and
encouraged by such b