"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
always something else to take its place. At the very worst, we
can but be blown about a bit."

"But it's exactly like a bird, then."

"Of course, Monsignor," said the priest, with twinkling eyes,
"it isn't likely that we could improve upon Almighty God's
design. We're very simple, you know. . . . Look, he's
signalling. We're going to start. Come to the prow. We shall see
better from there."