one end of the deck to the other, would very seriously
incline her from the horizontal, and thus alter the direction of her
flight, possibly with disastrous results; so I have devised this little
apparatus to prevent all that. This pendulum, as you see, is so
delicately poised that it will instantly respond to the slightest
deviation from a horizontal position, and, swaying over one of these
needle-points, will send an electric current to the air-pump, causing it
to promptly inject a sufficient quantity of air into the proper chamber
to restore the equilibrium. But, as we may desire occasionally to
direct the flight of the ship in an upward or a downward direction, I
have so arranged matters that the apparatus shall be thrown out of gear
when the tiller is sloped in either direction out of the horizontal; and
as we shall not require it when the ship is on or below the surface of
the ocean, I have here provided a small knob by pressing which inwards
the apparatus can also be thrown out of gear until it is again wanted."

"Excellent!" exclaimed the baronet. "I must again congratulate you,
professor, on your truly wonderful forethought. And what is this,
pray?"

"That," said the German, "is the controlling lever of the air-pump.
When we want to sink into the depths of the ocean, I thrust this lever
over--so; and the pump at once begins to pump air into the air-
chambers."

"_Out_ of them, I suppose you mean," interrupted the baronet.

"_Into_ them, I mean," insisted the professor. "You must understand,"
he continued, noting the baronet's look of astonishment, "that air, like
everything else, has _weight_. Feathers are light; but you may pack
them so tightly into a receptacle as to make them very weighty; and so
is it with air: the more air you force into a receptacle of given size
the heavier you make that receptacle; and, provided that both your
forcing apparatus and your receptacle are strong enough to endure the
tremendous pressure, you may at last force enough air into the
receptacle to sink it. And that is precisely what we shall do; we shall
force air into our air-chambers until the ship is on the point of
sinking, and we shall then close the valves, stop the air-pump, and,
opening the sea-cocks of the water-chambers, admit water enough into the
ship to send her to the bottom like a stone."

"Well! you astonish me, I freely admit," gasped the baronet. "This is
the first time I ever heard of a ship being