“Now,” continued the professor when the quartette had made their way to the upper floor of the pilot-house, which was moderately illuminated by an electric lamp of small power, “the first thing to be done is to place the tiller of the ship in a horizontal position, and thus bring into action the automatic balancing gear. So! It is done. The next thing is to expel the air from the entire hull of the ship, excepting, of course, the comparatively insignificant portion reserved for habitation, and this I do by injecting vapour into the several compartments. The vapour drives out the air, and then, condensing like steam, creates, if required, a perfect vacuum. This large wheel controls the valve which we now want to open. I turn it this way, so—and now we shall see what will happen.”
Two large dials were attached to the side of the pilothouse, close together; and upon these the professor now intently fixed his gaze. The index-hands of both were seen to be moving. A period of perhaps half a minute elapsed, and then the professor, suddenly shutting off the vapour, went over and closely inspected both dials.
“Good!” he exclaimed, after a single keen glance at each of them. “Gentlemen, let us congratulate each other. Our experiment is a Signal Success!”
“How do you know that, professor? How can you tell?” eagerly asked his companions.
“Look at these two dials; they will tell you,” replied the professor. “This dial,” tapping one with his finger, “indicates the weight of the ship, or the pressure with which she bears upon the ground. This one,” indicating the other, “shows the pressure of air inside the hull of the ship. The first, as you see, shows that the ship is now pressing upon the ground with a force of less than a single ton—in other words, she now weighs less than one ton. The air-gauge shows that there is still an air pressure of six pounds per square inch inside the hull, and we therefore have, as I expected we should, a large margin of buoyancy. Now, lieutenant, do me the favour to turn on the vapour once more, very cautiously. Steady! Stop! There, Sir Reginald, the index has reached zero, and your ship is now as nearly as possible without weight; and if a man were now underneath her, he might, notwithstanding her gigantic proportions, easily raise her upon his shoulders. Now comes the delicate part of our operation. To your stations on the deck quickly, gentlemen, if you please.”
The professor’s companions, just a trifle excited, perhaps, hurried away to their posts, and the scientist was left alone. The circular windows in the sides of the pilothouse were all left open, and in through them presently floated the voice of the lieutenant shouting:
“All ready abaft, professor.”
“All ready at this end,” replied the colonel.
The professor reversed the engines, turned on the vapour very cautiously indeed, and simultaneously, with the engines below only just barely moving, the huge propeller began to whirl round at a speed of some sixty revolutions a minute.
A breathless pause of perhaps two seconds followed, and then the professor, his forehead damp with nervous perspiration, heard: