dy, even
glow from invisible lights.

In the very centre of the deck, however, was a low railing
that protected the head of a staircase, and down this well
the two looked.

"Shall I explain?" asked the old priest, smiling. "This is
the latest model, you know. It has not been in use for more
than a few months."

The other nodded.

"Tell me everything, please."

"Well, look right down there, below the second flight. The first
flight leads to the second-class deck, and the flight below to the
working parts of the ship. Now do you see that man's head, straight
in the middle, in the bright light?--yes, immediately under. Well,
that's the first engineer. He's in a glass compartment, you see,
and can look down passages in every direction. The gas arrangements
are all in front of him, and the----"

"Stop, please. What power is it that drives the ship? Is it
lighter than air, or what?"

"Well, you see the entire framework of the ship is hollow. Every
single thing you see--even the chairs and tables--they're all
made of the metal _aerolite_ (as it's generally called). It's
almost as thin as paper, and it's far stronger than any steel.
Now it's the framework of the ship that takes the place of the
old balloon. It's infinitely safer, too, for it's divided by
automatically closing stops into tens of thousands of
compartments, so a leak here and there makes practically no
difference. Well, when the ship's at rest, as it is now, there's
simply air in all these tubes; but when it's going to start,
there is forced into these tubes, from the magazine below, the
most volatile gas that has been discovered----"

"What's it called?"

"I forget the real name. It's generally called _aeroline_. Well,
this is forced in, until the specific gravity of the whole
affair, passengers and all, is as nearly as possible the same as
the specific gravity of the air."

"I see. Good Lord, how simple!"

"And the rest is done with planes and screws, driven by
electricity. The tail of the boat is a recent development.
(You'll see it when we're once started.) It's exactly like the
tail of a bird, and contracts and expands in every direction.
Then besides that there are two wings, one on each side, and
these can be used, if necessary, in case the screws go wrong, as
propellers. But usually they are simply for balancing and
gliding. You see, barring collisions, there's hardly the
possibility of an accident. If one set of things fails, there's
a