“Then, some fine day,” said Pencroft, who did not appear to be entirely convinced, “the rest of this ancient continent may disappear in its turn, and there will be nothing between America and Asia.”

“Yes,” replied Harding, “there will be new continents which millions and millions of animalculae are building at this moment.”

“And what are these masons?” asked Pencroft.

“Coral insects,” replied Cyrus Harding.  “By constant work they made the island of Clermont-Tonnerre, and numerous other coral islands in the Pacific Ocean.  Forty-seven millions of these insects are needed to weigh a grain, and yet, with the sea-salt they absorb, the solid elements of water which they assimilate, these animalculae produce 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 alter 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