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 immense crater, Nature, as you can see, has left no flat and empty void. You can easily trace its special oreography, its various mountain systems which turn it into a regular world on a small scale. Notice its cones, its central hills, its valleys, its substructures already cut and dry and therefore quietly prepared to receive the masterpieces of Selenite architecture. Down there to the left is a lovely spot for a Saint Peter's; to the right, a magnificent site for a Forum; here a Louvre could be built capable of entrancing Michael Angelo himself; there a citadel could be raised to which even Gibraltar would be a molehill! In the middle rises a sharp peak which can hardly be less than a mile in height--a grand pedestal for the statue of some Selenite Vincent de Paul or George Washington. And around them all is a mighty mountain-ring at least 3 miles high, but which, to an eye looking from the centre of our vast city, could not appear to be more than five or six hundred feet. Enormous circus, where mighty Rome herself in her palmiest days, though increased tenfold, would have no reason to complain for want of room!" He stopped for a few seconds, perhaps to take breath, and then resumed: "Oh what an abode of serene happiness could be constructed within this shadow-fringed ring of the mighty mountains! O blessed refuge, unassailable by aught of human ills! What a calm unruffled life could be enjoyed within thy hallowed precincts, even by those cynics, those haters of humanity, those disgusted reconstructors of society, those misanthropes and misogynists old and young, who are continually writing whining verses in odd corners of the newspapers!" "Right at last, Ardan, my boy!" cried M'Nicholl, quietly rubbing the glass of his spectacles; "I should like to see the whole lot of them carted in there without a moment's delay!" "It couldn't hold the half of them!" observed Barbican drily. [Footnote D: BALTIMORE GUN CLUB, pp. 295 _et seq._] CHAPTER XVIII. PUZZLING QUESTIONS. It was not until the Projectile had passed a little beyond _Tycho's_ immense concavity that Barbican and his friends had a good opportunity for observing the brilliant streaks sent so wonderfully flying in all directions from this celebrated mountain as a common centre. They examined them for some time with the closest attention. What could be the nature of this radiating aureola? By what geological phenomena could this blazing coma have been possibly produced? Such questions were the most natural things in the world for Barbican and his companions to propound to themselves, as indeed they have been to every astronomer from the beginning of time, and probably will be to the end.