s, and it was only the lofty heights, the wide
craters, the great ring mountains, and the vast plains that still
continued to give sharp, distinctive outlines.

A little to their left, the travellers could now plainly distinguish one
of the most remarkable of the Moon's craters, _Newton_, so well known to
all lunar astronomers. Its ramparts, forming a perfect circle, rise to
such a height, at least 22,000 feet, as to seem insurmountable.

"You can, no doubt, notice for yourselves," said Barbican, "that the
external height of this mountain is far from being equal to the depth of
its crater. The enormous pit, in fact, seems to be a soundless sea of
pitchy black, the bottom of which the Sun's rays have never reached.
There, as Humboldt says, reigns eternal darkness, so absolute that
Earth-shine or even Sunlight is never able to dispel it. Had Michael's
friends the old mythologists ever known anything about it, they would
doubtless have made it the entrance to the infernal regions. On the
whole surface of our Earth, there is no mountain even remotely
resembling it. It is a perfect type of the lunar crater. Like most of
them, it shows that the peculiar formation of the Moon's surface is due,
first, to the cooling of the lunar crust; secondly, to the cracking from
internal pressure; and, thirdly, to the violent volcanic action in
consequence. This must have been of a far fiercer nature than it has
ever been with us. The matter was ejected to a vast height till great
mountains were formed; and still the action went on, until at last the
floor of the crater sank to a depth far lower than the level of the
external plain."

"You may be right," said Ardan by way of reply; "as for me, I'm looking
out for another city. But I'm sorry to say that our Projectile is
increasing its distance so fast that, even if one lay at my feet at this
moment, I doubt very much if I could see it a bit better than either you
or the Captain."

_Newton_ was soon passed, and the Projectile followed a course that took
it directly over the ring mountain _Moretus_. A little to the west the
travellers could easily distinguish the summits of _Blancanus_, 7,000
feet high, and, towards seven o'clock in the evening, they were
approaching the neighborhood of _Clavius_.

This walled-plain, one of the most remarkable on the Moon, lies 55 deg. S.
by 15 deg. E. Its height is estimated at 16,000 feet, but it is considered
to be about a hundred and fifty miles in d