“There exist,” said Barbicane, “several sorts of amphitheatres an the surface of the moon, and it is easy to see that Copernicus belongs to the radiating class.  If we were nearer it we should perceive the cones which bristle in the interior, and which were formerly so many fiery mouths.  A curious arrangement, and one without exception on the lunar disc, is presented on the interior surface of these amphitheatres, being notably downward from the exterior plane, a contrary form to that which terrestrial craters present.  It follows, therefore, that the general curvature at the bottom of these amphitheatres gives us fear of an inferior diameter to that of the moon.”

“What is the reason of this special arrangement?” asked Nicholl.

“It is not known,” answered Barbicane.

“How splendidly it shines!” said Michel.  “I think it would be difficult to see a more beautiful spectacle!”

“What should you say, then,” answered Barbicane, “if the chances of our journey should take us towards the southern hemisphere?”

“Well, I should say it is finer still,” replied Michel Ardan.

At that moment the projectile hung right over the amphitheatre.  The circumference of Copernicus formed an almost perfect circle, and its steep ramparts were clearly defined.  A second circular inclosure could even be distinguished.  A grey plain of wild aspect spread around on which every relief appeared yellow.  At the bottom of the amphitheatre, as if in a jewel-case, sparkled for one instant two or three eruptive cones like enormous dazzling gems.  Towards the north the sides of the crater were lowered into a depression which would probably have given access to the interior of the crater.

As they passed above the surrounding plain Barbicane was able to note a large number of mountains of slight importance, amongst others a little circular mountain called “Gay-Lussac,” more than twenty-three kilometres wide.  Towards the south the plain was very flat, without one elevation or projection of the soil.  Towards the north, on the contrary, as far as the place where it borders on the Ocean of Tempests, it was like a liquid surface agitated by a storm, of which the hills and hollows formed a succession of waves suddenly coagulated.  Over the whole of this, and in all directions, ran the luminous trails which converged to the summit of Copernicus.  Some had a width of thirty kilometres over a length that could not be estimated.

The travellers discussed the origin of these strange rays, but they could not determine their nature any better than terrestrial observers.

“Why,” said Nicholl, “may not these rays be simply the spurs of the mountains reflecting the light of the sun more vividly?”

“No,” answered Barbicane, “if it were so in certain conditions of the moon they would throw shadows, which they do not.”

In fact, these rays only appear when the sun is in opposition with the moon, and they disappear as soon as its rays become oblique.