_weight_ to the sun. They also show us that it would take 316 globes as
heavy as our Earth to counterbalance the weight of Jupiter.

No doubt this proves Jupiter to be a body of magnificent proportions;
but the remarkable circumstance is not that Jupiter should be 316 times
as heavy as the earth, but that he is not a great deal more. Have we not
stated that Jupiter is 1,300 times as _large_ as the earth? How then
comes it that he is only 316 times as _heavy_? This points at once to
some fundamental contrast between the constitution of Jupiter and of the
earth. How are we to account for this difference? We can conceive of two
explanations. In the first place, it might be supposed that Jupiter is
constituted of materials partly or wholly unknown on the earth. There
is, however, an alternative supposition at once more philosophical and
more consistent with the evidence. It is true that we know little or
nothing of what the elementary substances on Jupiter may be, but one of
the great discoveries of modern astronomy has taught us something of the
elementary bodies present in other bodies of the universe, and has
demonstrated that to a large extent they are identical with the
elementary bodies on the earth. If Jupiter be composed of bodies
resembling those on the earth, there is one way, and only one, in which
we can account for the disparity between his size and his mass. Perhaps
the best way of stating the argument will be found in a glance at the
remote history of the earth itself, for it seems not impossible that the
present condition of Jupiter was itself foreshadowed by the condition of
our earth countless ages ago.

In a previous chapter we had occasion to point out how the earth seemed
to be cooling from an earlier and highly heated condition. The further
we look back, the hotter our globe seems to have been; and if we project
our glance back to an epoch sufficiently remote, we see that it must
once have been so hot that life on its surface would have been
impossible. Back still earlier, we find the heat to have been such that
water could not rest on the earth; and hence it seems likely that at
some incredibly remote epoch all the oceans now reposing in the deeps on
the surface, and perhaps a considerable portion of its now solid crust,
must have been in a state of vapour. Such a transformation of the globe
would not alter its _mass_, for the materials weigh the same whatever be
their condition as to temperature, but