streaked with the great divergent fissures that radiate from it as a
centre.

Of what this incomparable mountain really is, with all these lines of
projections converging towards it and with all these prominent points
of relief protruding within its crater, photography has, so far, been
able to give us only a very unsatisfactory idea. The reason too is very
simple: it is only at Full Moon that _Tycho_ reveals himself in all his
splendor. The shadows therefore vanishing, the perspective
foreshortenings disappear and the views become little better than a dead
blank. This is the more to be regretted as this wonderful region is well
worthy of being represented with the greatest possible photographic
accuracy. It is a vast agglomeration of holes, craters, ring formations,
a complicated intersection of crests--in short, a distracting volcanic
network flung over the blistered soil. The ebullitions of the central
eruption still evidently preserve their original form. As they first
appeared, so they lie. Crystallizing as they cooled, they have
stereotyped in imperishable characters the aspect formerly presented by
the whole Moon's surface under the influences of recent plutonic
upheaval.

Our travellers were far more fortunate than the photographers. The
distance separating them from the peaks of _Tycho's_ concentric terraces
was not so considerable as to conceal the principal details from a very
satisfactory view. They could easily distinguish the annular ramparts of
the external circumvallation, the mountains buttressing the gigantic
walls internally as well as externally, the vast esplanades descending
irregularly and abruptly to the sunken plains all around. They could
even detect a difference of a few hundred feet in altitude in favor of
the western or right hand side over the eastern. They could also see
that these dividing ridges were actually inaccessible and completely
unsurmountable, at least by ordinary terrestrian efforts. No system of
castrametation ever devised by Polybius or Vauban could bear the
slightest comparison with such vast fortifications, A city built on the
floor of the circular cavity could be no more reached by the outside
Lunarians than if it had been built in the planet Mars.

This idea set Ardan off again. "Yes," said he, "such a city would be at
once completely inaccessible, and still not inconveniently situated in a
plateau full of aspects decidedly picturesque. Even in the depths of
this immen