hich
the earth and other larger planets vary but little. This no doubt is
due to the near approach and disturbing attraction of some large comet,
or else it was flung above or below the ordinary plane in the
catastrophe that we think befell the large planet that doubtless
formerly existed where we now find this swarm. You can see that its
path makes a considerable angle to the plane of the ecliptic, and that
it is now about crossing the line."

It soon presented the phase of a half moon, but the waviness of the
straight line, as in the case of Venus and Mercury, showed that the
size of the mountains must be tremendous compared with the mass of the
body, some of them being obviously fifteen miles high. The intense
blackness of the shadows, as on the moon, convinced them there was no
trace of atmosphere.

"There being no air," said Cortlandt, "it is safe to assume there is no
water, which helps to account for the great inequalities on the body's
surface, since the mountains will seem higher when surrounded by dry
ocean-bottom than they would if water came halfway up their sides.
Undoubtedly, however, the main cause of their height is the slight
effect of gravitation on an asteroid, and the fact that the shrinking
of the interior, and consequent folding of the crust in ridges, may
have continued for a time after there was no longer water on the
surface to cut them down.

"The temperature and condition of a body," continued Cortlandt, "seem
to depend entirely on its size. In the sun we have an incandescent,
gaseous star, though its spots and the colour of its rays show that it
is becoming aged, or, to be more accurate, advanced in its evolutionary
development. Then comes a great jump, for Jupiter has but about one
fourteen-hundredth of the mass of the sun, and we expect to find on it
a firm crust, and that the planet itself is at about the fourth or
fifth period of development, described by Moses as days. Saturn is
doubtless somewhat more advanced. The earth we know has been habitable
many hundreds of thousands or millions of years, though three fourths
of its surface is still covered by water. In Mars we see a further
step, three fourths of its surface being land. In Mercury, could we
study it better, or in the larger satellites of Jupiter or Saturn, we
might find a stepping-stone from Mars to the moon, perhaps with no
water, but still having air, and being habitable in all other respects.
In our own satellit