In the meantime the projectile had reached the altitude of the 40th degree of lunar latitude at a distance that could not be greater than 800 kilometres.  Objects appeared through the telescopes at two leagues only.  At this point rose under their feet the Helicon, 505 metres high, and on the left were the mediocre heights, which inclose a small portion of the Sea of Rains under the name of the Gulf of Iris.

The terrestrial atmosphere ought to be 170 times more transparent than it is in order to allow astronomers to make complete observations on the surface of the moon.  But in the void the projectile was moving in no fluid lay between the eye of the observer and the object observed.  What is more, Barbicane was at a less distance than the most powerful telescopes, even that of Lord Rosse or the one on the Rocky Mountains, could give.  It was, therefore, in circumstances highly favourable for solving the great question of the habitability of the moon.  Yet the solution of this question escaped him still.  He could only distinguish the deserted beds of the immense plains, and, towards the north, arid mountains.  No labour betrayed the hand of man.  No ruin indicated his passage.  No agglomeration of animals indicated that life was developed there, even in an inferior degree.  There was no movement anywhere, no appearance of vegetation anywhere.  Of the three kingdoms represented on the terrestrial globe, one only was represented on that of the moon—­viz., the mineral kingdom.

“So,” said Michel Ardan, looking rather put out, “there is nobody after all.”

“No,” answered Nicholl; “we have seen neither man, animal, nor tree as yet.  After all, if the atmosphere has taken refuge at the bottom of cavities, in the interior of the amphitheatres, or even on the opposite face of the moon, we cannot decide the question.”

“Besides,” added Barbicane, “even for the most piercing sight a man is not visible at a distance of more than four miles.  Therefore if there are any Selenites they can see our projectile, but we cannot see them.”

About 11 a.m., at the altitude of the 50th parallel, the distance was reduced to 300 miles.  On the left rose the capricious outlines of a chain of mountains, outlined in full light.  Towards the right, on the contrary, was a large black hole like a vast dark and bottomless well bored in the lunar soil.

That hole was the Black Lake, or Pluto, a deep circle from which the earth could be conveniently studied between the last quarter and the new moon, when the shadows are thrown from west to east.

This black colour is rarely met with on the surface of the satellite.  It has, as yet, only been seen in the depths of the circle of Endymion, to the east of the Cold Sea, in the northern hemisphere, and at the bottom of the circle of Grimaldi upon the equator towards the eastern border of the orb.