ished a
still easier method of pursuing their observation, they had but to
remain poised between the sun and Jupiter, beyond the latter's upper
air, and photograph or map it as it revolved before them.

By sunset they had gone a hundred miles. Wishing to push along, they
closed the windows, rose higher to avoid any mountain-tops that might
be invisible in the moonlight, and increased their speed. The air made
a gentle humming sound as they shot through it, and towards morning
they saw several bright points of light in which they recognized, by
the aid of their glasses, sheets of flame and torrents of molten
glowing lava, bursting at intervals or pouring steadily from several
volcanoes. From this they concluded they were again near an ocean,
since volcanoes need the presence of a large body of water to provide
steam for their eruptions.

With the rising sun they found the scene of the day before entirely
changed. They were over the shore of a vast ocean that extended to the
left as far as they could see, for the range of vision often exceeded
the power of sight. The coast-line ran almost due north and south,
while the volcanoes that dotted it, and that had been luminous during
the night, now revealed their nature only by lines of smoke and
vapours. They were struck by the boldness and abruptness of the
scenery. The mountains and cliffs had been but little cut down by
water and frost action, and seemed in the full vigour of their youth,
which was what the travellers had a right to expect on a globe that was
still cooling and shrinking, and consequently throwing up ridges in the
shape of mountains far more rapidly than a planet as matured and
quiescent as the earth. The absence of lakes also showed them that
there had been no Glacial period, in the latitudes they were crossing,
for a very long time.

"We can account for the absence of ice-action and scratches," said
Cortlandt, "in one of two ways. Either the proximity of the internal
heat to the surface prevents water from freezing in all latitudes, or
Jupiter's axis has always been very nearly perpendicular to its orbit,
and consequently the thermometer has never been much below thirty-two
degrees Fahrenheit; for, at the considerable distance we are now from
the sun, it is easy to conceive that, with the axis much inclined,
there might be cold weather, during the Northern hemisphere's winter,
that would last for about six of our years, even as near the equator