From the fact that the exposed surface farther south must be old, on
account of the slow upheaval and the slight wear to which it is
exposed, about the only wearing agent being the wind, which would be
powerless to erase ice-scratches, especially since, on account of
gravity's power, it cannot, like our desert winds, carry much
sand--which, as we know, has cut away the base of the Sphinx--I think
it is logical to conclude that, though Jupiter's axis is changing
naturally as the earth's has been, it has never varied as much as
twenty-three and a half degrees, and certainly to nothing like the
extent to which we see Venus and Uranus tilted to-day."

[2] It is well known that mountain chains are but ridges or foldings
in the crust upheaved as the interior cools and shrinks. This is
proved by reason and by experiments with viscous clay or other material
placed upon a sheet of stretched rubber, which is afterwards allowed to
contract, whereupon the analogues of mountain ridges are thrown up.

"I follow you," said Bearwarden, "and do not see how we could arrive at
anything else. From Jupiter's low specific gravity, weighing but
little more than an equal bulk of water, I should say the interior must
be very hot, or else is composed of light material, for the crust's
surface, or the part we see, is evidently about as dense as what we
have on earth. These things have puzzled me a good deal, and I have
been wondering if Jupiter may not have been formed before the earth and
the smaller planets."

"The discrepancies between even the best authorities," replied
Cortlandt, "show that as yet but little has been discovered from the
earth concerning Jupiter's real condition. The two theories that try
to account for its genesis are the ring theory and the nebulous. We
know that the sun is constantly emitting vast volumes of heat and
light, and that, with the exception of the heat resulting from the
impact of falling meteors, it receives none from outside, the principal
source being the tremendous friction and pressure between the cooling
and shrinking strata within the great mass of the sun itself. A
seeming paradox therefore comes in here, which must be considered: If
the sun were composed entirely of gas, it would for a time continue to
grow hotter; but the sun is incessantly radiating light and heat, and
consequently becoming smaller. Therefore the farther back we go the
hotter we find the sun, and also the larger, till,