The change consisted in this, that the base of the projectile had turned toward the moon’s surface, and was so held by a perpendicular passing through its axis. The attraction, that is to say the weight, had brought about this alteration. The heaviest part of the projectile inclined toward the invisible disc as if it would fall upon it. Was it falling? Were the travelers attaining that much desired end? No. And the observation of a sign-point, quite inexplicable in itself, showed Barbicane that his projectile was not nearing the moon, and that it had shifted by following an almost concentric curve. This point of mark was a luminous brightness, which Nicholl sighted suddenly, on the limit of the horizon formed by the black disc. This point could not be confounded with a star. It was a reddish incandescence which increased by degrees, a decided proof that the projectile was shifting toward it and not falling normally on the surface of the moon. “A volcano! it is a volcano in action!” cried Nicholl; “a disemboweling of the interior fires of the moon! That world is not quite extinguished.” “Yes, an eruption,” replied Barbicane, who was carefully studying the phenomenon through his night glass. “What should it be, if not a volcano?” “But, then,” said Michel Ardan, “in order to maintain that combustion, there must be air. So the atmosphere does surround that part of the moon.” “Perhaps so,” replied Barbicane, “but not necessarily. The volcano, by the decomposition of certain substances, can provide its own oxygen, and thus throw flames into space. It seems to me that the deflagration, by the intense brilliancy of the substances in combustion, is produced in pure oxygen. We must not be in a hurry to proclaim the existence of a lunar atmosphere.” The fiery mountain must have been situated about the 45° south latitude on the invisible part of the disc; but, to Barbicane’s great displeasure, the curve which the projectile was describing was taking it far from the point indicated by the eruption. Thus he could not determine its nature exactly. Half an hour after being sighted, this luminous point had disappeared behind the dark horizon; but the verification of this phenomenon was of considerable consequence in their selenographic studies. It proved that all heat had not yet disappeared from the bowels of this globe; and where heat exists, who can affirm that the vegetable kingdom, nay, even the animal kingdom itself, has not up to this time resisted all destructive influences? The existence of this volcano in eruption, unmistakably seen by these earthly savants, would doubtless give rise to many theories favorable to the grave question of the habitability of the moon.