is slighter still. Jupiter would sink if thrown into water, but Saturn
would actually float, if not "like a cork," yet quite as buoyantly as
many kinds of wood, for its mean density is only three quarters that of
water, or one eighth of the earth's. In fact, there is no known planet
whose density is so slight as Saturn's. Thus it happens that,
notwithstanding its vast size and mass, the force of gravity upon Saturn
is nearly the same as upon our globe. Upon visiting Venus we should find
ourselves weighing a little less than at home, and upon visiting Saturn
a little more, but in neither case would the difference be very
important. If the relative weight of bodies on the surfaces of planets
formed the sole test of their habitability, Venus and Saturn would both
rank with the earth as suitable abodes for men.

But the exceedingly slight density of Saturn seems to be most reasonably
accounted for on the supposition that, like Jupiter, it is in a vaporous
condition, still very hot within--although but slightly, if at all,
incandescent at the surface--and, therefore, unsuited to contain life.
It is hardly worth while to speculate about any solid nucleus within,
because, even if such a thing were possible, or probable, it must lie
forever hidden from our eyes. But if we accept the theory that Saturn is
in an early formative stage, and that, millions of years hence, it may
become an incrusted and habitable globe, we shall, at least, follow the
analogy of what we believe to have been the history of the earth, except
that Saturn's immense distance from the sun will always prevent it from
receiving an amount of solar radiation consistent with our ideas of what
is required by a living world. Of course, since one can imagine what he
chooses, it is possible to suppose inhabitants suited to existence in a
world composed only of whirling clouds, and a poet with the imagination
of a Milton might give us very imposing and stirring images of such
creatures and their chaotic surroundings, but fancies like these can