"That is not a valuable argument, as the poles are not inhabited."

"In the actual state of the moon," resumed Barbicane, "the long nights
and days create differences of temperature insupportable to the
constitution, but it was not so at that epoch of historical times. The
atmosphere enveloped the disc with a fluid mantle. Vapour deposited
itself in the form of clouds. This natural screen tempered the ardour of
the solar lays, and retained the nocturnal radiation. Both light and
heat could diffuse themselves in the air. Hence there was equilibrium
between the influences which no longer exists now that the atmosphere
has almost entirely disappeared. Besides, I shall astonish you--"

"Astonish us?" said Michel Ardan.

"But I believe that at the epoch when the moon was inhabited the nights
and days did not last 354 hours!"

"Why so?" asked Nicholl quickly.

"Because it is very probable that then the moon's movement of rotation
on her axis was not equal to her movement of revolution, an equality
which puts every point of the lunar disc under the action of the solar
rays for fifteen days."

"Agreed," answered Nicholl; "but why should not these movements have
been equal, since they are so actually?"

"Because that equality has only been determined by terrestrial
attraction. Now, how do we know that this attraction was powerful enough
to influence the movements of the moon at the epoch the earth was still
fluid?"

"True," replied Nicholl; "and who can say that the moon has always been
the earth's satellite?"

"And who can say," exclaimed Michel Ardan, "that the moon did not exist
before the earth?"

Imagination began to wander in the indefinite field of hypotheses.
Barbicane wished to hold them in.

"Those," said he, "are speculations too high, problems really insoluble.
Do not let us enter into them. Let us only admit the insufficiency of
primordial attraction, and then by the inequality of rotation and
revolution days and nights could succeed each other upon the moon as
they do upon the earth. Besides, even under those conditions life was
possible."

"Then," asked Michel Ardan, "humanity has quite disappeared from the
moon?"

"Yes," answered Barbicane, "after having, doubtless, existed for
thousands of centuries. Then gradually the atmosphere becoming rarefied,
the disc will again be uninhabitable like the terrestrial globe will one
day become by cooling."

"By cooling?"

"Certainly," answered Barbicane