"Let us hear it," said Barbican.

"Certainly," was Ardan's reply; "these streaks are all only the parts of
what we call a 'star,' as made by a stone striking ice; or by a ball, a
pane of glass."

"Not bad," smiled Barbican approvingly; "only where is the hand that
flung the stone or threw the ball?"

"The hand is hardly necessary," replied Ardan, by no means disconcerted;
"but as for the ball, what do you say to a comet?"

Here M'Nicholl laughed so loud that Ardan was seriously irritated.
However, before he could say anything cutting enough to make the Captain
mind his manners, Barbican had quickly resumed:

"Dear friend, let the comets alone, I beg of you; the old astronomers
fled to them on all occasions and made them explain every difficulty--"

--"The comets were all used up long ago--" interrupted M'Nicholl.

--"Yes," went on Barbican, as serenely as a judge, "comets, they said,
had fallen on the surface in meteoric showers and crushed in the crater
cavities; comets had dried up the water; comets had whisked off the
atmosphere; comets had done everything. All pure assumption! In your
case, however, friend Michael, no comet whatever is necessary. The shock
that gave rise to your great 'star' may have come from the interior
rather than the exterior. A violent contraction of the lunar crust in
the process of cooling may have given birth to your gigantic 'star'
formation."

"I accept the amendment," said Ardan, now in the best of humor and
looking triumphantly at M'Nicholl.

"An English scientist," continued Barbican, "Nasmyth by name, is
decidedly of your opinion, especially ever since a little experiment of
his own has confirmed him in it. He filled a glass globe with water,
hermetically sealed it, and then plunged it into a hot bath. The
enclosed water, expanding at a greater rate than the glass, burst the
latter, but, in doing so, it made a vast number of cracks all diverging
in every direction from the focus of disruption. Something like this he
conceives to have taken place around _Tycho_. As the crust cooled, it
cracked. The lava from the interior, oozing out, spread itself on both
sides of the cracks. This certainly explains pretty satisfactorily why
those flat glistening streaks are of much greater width than the
fissures through which the lava had at first made its way to the
surface."

"Well done for an Englishman!" cried Ardan in great spirits.

"He's no Englishman," said M'Nicholl, glad to