iameter. 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 AEtna, 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,