"Then," resumed Barbicane, "it was surrounded by atmosphere. The water held in by the gassy element could not evaporate. Under the influence of air, water, light, and heat, solar and central, vegetation took possession of these continents prepared for its reception, and certainly life manifested itself about that epoch, for Nature does not spend itself in inutilities, and a world so marvellously habitable must have been inhabited." "Still," answered Nicholl, "many phenomena inherent to the movements of our satellite must have prevented the expansion of the vegetable and animal kingdoms. The days and nights 354 hours long, for example." "At the terrestrial poles," said Michel, "they last six months." "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?"