"Which is a lesson that will keep you for a while," smiled the Commander. "Ah, there's our host, and I hear the breakfast gong sounding. Come, Dick, my lad, you could eat, you think? the great height at which we fly does not rob you of your appetite?" Not by a long way. The young fellow was beginning to revel in his strange surroundings, and to quite like this residence at a height. More than all, he was vastly interested in the intricacies of the vessel. And we record only the fact when we say that he and Alec spent the whole of the morning in a close and thorough investigation, an investigation which disclosed, among other matters, the interesting fact that centrally-placed propellers, operating in tubes built transversely at either end of the ship, controlled her sideways movements, making entrance to a hangar easy, while she could be caused to descend or rise by others, located fore and aft likewise, with their tubes built in the vertical direction. As for the huge framework that held the gas, it was divided into twenty compartments, to each of which pipes of that strange transparent material led. These latter ended in one large branch which was attached to a machine at one end of the engine-room. Joe explained its action with a gusto that showed it to be one of his pet items, one on which he prided himself not a little. "What's the good of a ship which has to constantly return to land for gas supplies?" he said. "We take ours with us. Not compressed and in steel cylinders. Anyone can do that. But in the form of fuel. We carry a matter of seven tons, and can get a further supply in any part of the world. A gas producer of my own designing deals with the stuff, and at desire we can supply gas to replace leakages. Not that we experience those. Otherwise it would not be safe to smoke. But each one of our compartments aboard the ship contains a proportion of air. When we want to go higher, or lift a bigger weight, we simply set the producer going, and by means of one of our motors pump gas to the top of the compartments. Simple, isn't it? But it makes us wonderfully independent. That's why we've undertaken to make a trip round the world." "Round the world? When?" "Now--to-morrow, that is to say." "And--and I go with you?" gasped Dick. "Of course; you've been detailed by the Admiralty."