professor now laid his hand.

“This,” he said, “regulates the valve which admits vapour into the engine; and the dial-hand shows the extent to which the valve is opened. Turn the wheel in the direction of the arrow marked ‘On’—thus, and you admit vapour into the engine. You will observe that, as I turn the wheel, the hand on the dial travels over the arc and indicates the extent to which the valve is open. There; now it is fully open, and the cylinders are full of vapour.” Then he quickly reversed the wheel and sent the index hand back to “Stop,” keeping a wary eye on his companions as he did so.

“These are dangerous things to meddle with,” he remarked apologetically. “The engines are of one hundred thousand horse-power; and, full as the ship now is of air at the atmospheric pressure, they would drive her irresistibly along the ground and through all obstacles. I must beg that none of you will meddle with the machinery until you are fully acquainted with its tremendous power.”

“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:

“That is capital, professor; we ought to have the means of fighting the ship, if necessary; but I was beginning to fear you had overlooked that matter, having seen no provision for anything of the kind. But where is your torpedo port? you omitted to point that out to us when we were under the ship’s bottom.”

“There was nothing to show,” replied the professor; “and I can explain the matter just as well up here as I could have done when we were down below. The conical point which forms the extreme forward end of the ship is solid and movable. Under ordinary circumstances it remains firmly fixed in position; but when it becomes necessary to fire a torpedo-shell the solid point is made to slide in along a grooved tube for a certain distance; the shell is then placed in the tube and fired, when the solid point follows it out and becomes again securely fixed in its former position. In addition to this arrangement, I have two large guns which can be worked through ports in the dining-saloon, and six wonderful magazine rifles invented by a Mr Maxim, a friend of mine. They are perhaps the most wonderful pieces of mechanism in the ship, for when the first shot has been fired they will go on firing themselves at the marvellous rate of six hundred shots per minute so long as you keep them supplied with cartridges. Then I have also provided an ample supply of ordinary guns and rifles, swords, pikes, pistols, and in fact everything we are likely to require for the purposes of sport or defence. These small knobs afford the means of lighting the electric lamp in the lantern on the top of the pilot-house and those in the bow and stern of the ship. And that is all to which I think I need direct your attention here at present. Now, if you please, we will go down and look at the machinery.”

The party accordingly left the pilot-house and directed their steps below by way of the grand staircase. At the bottom of this they found themselves upon a spacious landing magnificently carpeted, and lighted at each end by a circular window in the side of the ship. In front of them as they descended the staircase, and at a distance of about twelve feet from its base, a partition stretched from side to side of the ship, evidently forming one of the saloon bulkheads. Along the face of this a series of Corinthian pilasters, supporting a noble cornice at the junction of wall and ceiling, divided up the partition into a corresponding number of panels, which were enriched with elegant mouldings of fanciful scroll-work and painted in creamy white and gold. In two instances, however, at points which divided the partition into three equal parts, the panels were replaced by handsome massively moulded doors of unpainted aethereum, imparting a very rich and handsome effect. These doors were, however, closed, and the curiosity of the new-comers as to what was to be seen on the other side of them had to remain for a short time ungratified.

Passing round to the back