"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 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."
The upper deck ended in a railing, below which protruded, from the level of the lower deck, the prow proper of the boat. Upon this prow, in a small compartment of which the roof, as well as the walls, was of hardened glass, stood the steersman amid his wheels. But the wheels were unlike anything that the bewildered man who looked down had ever dreamed of. First, they were not more than six inches in diameter; and next, they were arranged, like notes on a keyboard, with their edges towards him, with the whole set curved round him in a semicircle.
"Those to right and left," explained the priest, "control the planes on either side; those in front, on the left, control the engines and the gas supply; and on the right, the tail of the boat. Watch him, and you'll see. We're just starting."