limestone, and
this limestone forms enormous submarine erections, of which the hardness
and solidity equal granite. Formerly, at the first periods of creation,
nature employing fire, heaved up the land, but now she entrusts to these
microscopic creatures the task of replacing this agent, of which
the dynamic power in the interior of the globe has evidently
diminished--which is proved by the number of volcanoes on the surface of
the earth, now actually extinct. And I believe that centuries succeeding
to centuries, and insects to insects, this Pacific may one day be
changed into a vast continent, which new generations will inhabit and
civilize in their turn."

"That will take a long time," said Pencroft.

"Nature has time for it," replied the engineer.

"But what would be the use of new continents?" asked Herbert. "It
appears to me that the present extent of habitable countries is
sufficient for humanity. Yet nature does nothing uselessly."

"Nothing uselessly, certainly," replied the engineer, "but this is
how the necessity of new continents for the future, and exactly on the
tropical zone occupied by the coral islands, may be explained. At least
to me this explanation appears plausible."

"We are listening, captain," said Herbert.

"This is my idea: philosophers generally admit that some day our globe
will end, or rather that animal and vegetable life will no longer be
possible, because of the intense cold to which it will be subjected.
What they are not agreed upon, is the cause of this cold. Some think
that it will arise from the falling of the temperature, which the
sun will experience after millions of years; others, from the gradual
extinction of the fires in the interior of our globe, which have a
greater influence on it than is generally supposed. I hold to this last
hypothesis, grounding it on the fact that the moon is really a cold
star, which is no longer habitable, although the sun continues to throw
on its surface the same amount of heat. If, then, the moon has become
cold, it is because the interior fires to which, as do all the stars of
the stellar world, it owes its origin, are completely extinct. Lastly,
whatever may be the cause, our globe will become cold some day, but this
cold will only operate gradually. What will happen, then? The temperate
zones, at a more or less distant period, will not be more habitable than
the polar regions now are. Then the population of men, as well as the
animals, w