This walled-plain, one of the most remarkable on the Moon, lies 55° S. by 15° E. Its height is estimated at 16,000 feet, but it is considered to be about a hundred and fifty miles in diameter. Of this vast crater, the travellers now at a distance of 250 miles, reduced to 2-1/2 by their telescopes, had a magnificent bird's-eye view.
"Our terrestrial volcanoes," said Barbican, "as you can now readily judge for yourselves, are no more than molehills when compared with those of the Moon. Measure the old craters formed by the early eruptions of Vesuvius and Ætna, and you will find them little more than three miles in diameter. The crater of Cantal in central France is only about six miles in width; the famous valley in Ceylon, called the Crater, though not at all due to volcanic action, is 44 miles across and is considered to be the greatest in the world. But even this is very little in comparison to the diameter of Clavius lying beneath us at the present moment."
"How much is its diameter?" asked the Captain.
"At least one hundred and forty-two miles," replied Barbican; "it is probably the greatest in the Moon, but many others measure more than a hundred miles across."
"Dear boys," said Ardan, half to himself, half to the others, "only imagine the delicious state of things on the surface of the gentle Moon when these craters, brimming over with hissing lava, were vomiting forth, all at the same time, showers of melted stones, clouds of blinding smoke, and sheets of blasting flame! What an intensely overpowering spectacle was here presented once, but now, how are the mighty fallen! Our Moon, as at present beheld, seems to be nothing more than the skinny spectre left after a brilliant display of fireworks, when the spluttering crackers, the glittering wheels, the hissing serpents, the revolving suns, and the dazzling stars, are all 'played out', and nothing remains to tell of the gorgeous spectacle but a few blackened sticks and half a dozen half burned bits of pasteboard. I should like to hear one of you trying to explain the cause, the reason, the principle, the philosophy of such tremendous cataclysms!"
Barbican's only reply was a series of nods, for in truth he had not heard a single word of Ardan's philosophic explosion. His ears were with his eyes, and these were obstinately bent on the gigantic ramparts of Clavius, formed of concentric mountain ridges, which were actually leagues in depth. On the floor of the vast cavity, could be seen hundreds of smaller craters, mottling it like a skimming dish, and pierced here and there by sharp peaks, one of which could hardly be less than 15,000 feet high.
All around, the plain was desolate in the extreme. You could not conceive how anything could be barrener than these serrated outlines, or gloomier than these shattered mountains—until you looked at the plain that encircled them. Ardan hardly exaggerated when he called it the scene of a battle fought thousands of years ago but still white with the hideous bones of overthrown peaks, slaughtered mountains and mutilated precipices!
"Hills amid the air encountered hills,
Hurled to and fro in jaculation dire,"
murmured M'Nicholl, who could quote you Milton quite as readily as the Bible.
"This must have been the spot," muttered Barbican to himself, "where the brittle shell of the cooling sphere, being thicker than usual, offered greater resistance to an eruption of the red-hot nucleus. Hence these piled up buttresses, and these orderless heaps of consolidated lava and ejected scoriæ."