"Enough said! I see it at a glance! Thank you, Barbican. Why did not they make you a professor of astronomy? Your hint will save me a world of trouble."[C]
Aided by the Mappa Selenographica, the travellers could easily recognize the different portions of the Moon over which they were now moving. An occasional glance at our reduction of this map, given as a frontispiece, will enable the gentle reader to follow the travellers on the line in which they moved and to understand the remarks and observations in which they occasionally indulged.
"Where are we now?" asked Ardan.
"Over the northern shores of the Mare Nubium," replied Barbican. "But we are still too far off to see with any certainty what they are like. What is the Mare itself? A sea, according to the early astronomers? a plain of solid sand, according to later authority? or an immense forest, according to De la Rue of London, so far the Moon's most successful photographer? This gentleman's authority, Ardan, would have given you decided support in your famous dispute with the Captain at the meeting near Tampa, for he says very decidedly that the Moon has an atmosphere, very low to be sure but very dense. This, however, we must find out for ourselves; and in the meantime let us affirm nothing until we have good grounds for positive assertion."
Mare Nubium, though not very clearly outlined on the maps, is easily recognized by lying directly east of the regions about the centre. It would appear as if this vast plain were sprinkled with immense lava blocks shot forth from the great volcanoes on the right, Ptolemaeus, Alphonse, Alpetragius and Arzachel. But the Projectile advanced so rapidly that these mountains soon disappeared, and the travellers were not long before they could distinguish the great peaks that closed the "Sea" on its northern boundary. Here a radiating mountain showed a summit so dazzling with the reflection of the solar rays that Ardan could not help crying out:
"It looks like one of the carbon points of an electric light projected on a screen! What do you call it, Barbican?"
"Copernicus," replied the President. "Let us examine old Copernicus!"
This grand crater is deservedly considered one of the greatest of the lunar wonders. It lifts its giant ramparts to upwards of 12,000 feet above the level of the lunar surface. Being quite visible from the Earth and well situated for observation, it is a favorite object for astronomical study; this is particularly the case during the phase existing between Last Quarter and the New Moon, when its vast shadows, projected boldly from the east towards the west, allow its prodigious dimensions to be measured.
After Tycho, which is situated in the southern hemisphere, Copernicus forms the most important radiating mountain in the lunar disc. It looms up, single and isolated, like a gigantic light-house, on the peninsula separating Mare Nubium from Oceanus Procellarum on one side and from Mare Imbrium on the other; thus illuminating with its splendid radiation three "Seas" at a time. The wonderful complexity of its bright streaks diverging on all sides from its centre presented a scene alike splendid and unique. These streaks, the travellers thought, could be traced further north than in any other direction: they fancied they could detect them even in the Mare Imbrium, but this of course might be owing to the point from which they made their observations. At one o'clock in the morning, the Projectile, flying through space, was exactly over this magnificent mountain.
In spite of the brilliant sunlight that was blazing around them, the travellers could easily recognize the peculiar features of Copernicus. It belongs to those ring mountains of the first class called Circuses. Like Kepler and Aristarchus, who rule over Oceanus Procellarum, Copernicus, when viewed through our telescopes, sometimes glistens so brightly through the ashy light of the Moon that it has been frequently taken for a volcano in full activity. Whatever it may have been once, however, it is certainly nothing more now than, like all the other mountains on the visible side of the Moon, an extinct volcano, only with a crater of such exceeding grandeur and sublimity as to throw utterly into the shade everything like it on our Earth. The crater of Etna is at most little more than a mile across. The crater of Copernicus has a diameter of at least 50 miles. Within it, the travellers could easily discover by their glasses an immense number of terraced ridges, probably landslips, alternating with stratifications resulting from successive eruptions. Here and there, but particularly in the southern side, they caught glimpses of shadows of such intense blackness, projected across the plateau and lying there like pitch spots, that they could not tell them from yawning chasms of incalculable depth. Outside the crater the shadows were almost as deep, whilst on the plains all around, particularly in the west, so many small craters could be detected that the eye in vain attempted to count them.