original idea!" said Barbican with a smile.

"My ideas generally are of that category," observed Ardan with an
affectation of dry pomposity.

"Not this time, however, friend Michael," observed M'Nicholl.

"Oh! I'm a plagiarist, am I?" asked the Frenchman, pretending to be
irritated.

"Well, something very like it," observed M'Nicholl quietly. "Apollonius
Rhodius, as I read one evening in the Philadelphia Library, speaks of
the Arcadians of Greece having a tradition that their ancestors were so
ancient that they inhabited the Earth long before the Moon had ever
become our satellite. They therefore called them [Greek: _Proselenoi_]
or _Ante-lunarians_. Now starting with some such wild notion as this,
certain scientists have looked on the Moon as an ancient comet brought
close enough to the Earth to be retained in its orbit by terrestrial
attraction."

"Why may not there be something plausible in such a hypothesis?" asked
Ardan with some curiosity.

"There is nothing whatever in it," replied Barbican decidedly: "a simple
proof is the fact that the Moon does not retain the slightest trace of
the vaporous envelope by which comets are always surrounded."

"Lost her tail you mean," said Ardan. "Pooh! Easy to account for that!
It might have got cut off by coming too close to the Sun!"

"It might, friend Michael, but an amputation by such means is not very
likely."

"No? Why not?"

"Because--because--By Jove, I can't say, because I don't know," cried
Barbican with a quiet smile on his countenance.

"Oh what a lot of volumes," cried Ardan, "could be made out of what we
don't know!"

"At present, for instance," observed M'Nicholl, "I don't know what
o'clock it is."

"Three o'clock!" said Barbican, glancing at his chronometer.

"No!" cried Ardan in surprise. "Bless us! How rapidly the time passes
when we are engaged in scientific conversation! Ouf! I'm getting
decidedly too learned! I feel as if I had swallowed a library!"

"I feel," observed M'Nicholl, "as if I had been listening to a lecture
on Astronomy in the _Star_ course."

"Better stir around a little more," said the Frenchman; "fatigue of body
is the best antidote to such severe mental labor as ours. I'll run up
the ladder a bit." So saying, he paid another visit to the upper portion
of the Projectile and remained there awhile whistling _Malbrouk_, whilst
his companions amused themselves in looking through the floor window.

Ardan was coming down the l