in weight as a result of their ethereal
journey, this did not incommode them; for though Jupiter's volume is
thirteen hundred times that of the earth, on account of its lesser
specific gravity, it has but three hundred times the mass--i. e., it
would weigh but three hundred times as much. Further, although a cubic
foot of water or anything else weighs 2.5 as much as on earth, objects
near the equator, on account of Jupiter's rapid rotation, weigh one
fifth less than they do at the poles, by reason of the centrifugal
force. Influenced by this fact, and also because they were 483,000,000
miles from the sun, instead of 92,000,000 as on earth, they had steered
for the northern limit of Jupiter's tropics. And, in addition to this,
they could easily apply the apergetic power in any degree to themselves
when beyond the limits of the Callisto, and so be attracted to any
extent, from twice the pull they receive from gravitation on earth to
almost nothing.

Bearwarden and Ayrault shouldered their rifles, while Dr. Cortlandt
took a repeating shot-gun with No. 4 shot, and, having also some
hunting-knives and a sextant, all three set out in a northwesterly
direction. The ground was rather soft, and a warm vapor seemed to rise
from it. To the east the sky was veiled by dense clouds of smoke from
the towering volcanoes, while on their left the forest seemed to extend
without limit. Clumps of huge ferns were scattered about, and the
ground was covered with curious tracks.

"Jupiter is evidently passing through a Carboniferous or Devonian
period such as existed on earth, though, if consistent with its size,
it should be on a vastly larger scale," said the doctor. "I never
believed in the theory," he continued, "that the larger the planet the
smaller should be its inhabitants, and always considered it a
makeshift, put forward in the absence of definite knowledge, the idea
being apparently that the weight of very large creatures would be too
great for their strength. Of the fact that mastodons and creatures far
larger than any now living on earth existed there, we have absolute
proof, though gravitation must have been practically the same then as
now."

Just here they came upon a number of huge bones, evidently the remains
of some saurian, and many times the size of a grown crocodile. On
passing a growth of most luxuriant vegetation, they saw a half-dozen
sacklike objects, and drawing nearer noticed that the tops began to
sw