“What is this pendulum-looking affair, professor?” asked the colonel, pointing to a pendulum the point of which hung in a shallow basin-like depression thickly studded with needle-points which the pendulum just cleared by a hair’s-breadth.
“That,” explained the professor, “is a device for automatically regulating the balance, or ‘trim’ as you call it, of the ship when she is floating in the air. You will readily understand that when freed of air, and thus deprived of weight, as it were, the most trifling matter will suffice to derange her equilibrium; one of us, walking from side to side, or from 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 sunk by filling her with air. And then the cool way in which you talk of our ‘sinking to the bottom like a stone!’ I undertook this enterprise because I wanted to experience a new sensation; and it appears to me that there are a good many of them in store for me. However, it is all right; go on with your explanations, my dear sir.”
“These,” said the professor, indicating several levers marked with distinguishing labels ranged all along one side of the pilot-house, “are the levers opening and closing the valves of the air and water chambers, and need no further description. This,” he continued, pointing to a small box with a little knob projecting out of the top of it, “is the apparatus for firing our torpedo shells.”
The baronet glanced mutely round at his companions, and shrugged his shoulders expressively, as who should say, “What next?”
The colonel and the lieutenant nodded approvingly, however, and the latter said: