"But how do you account for this incredible fountain?" I asked. "It must be due to geological causes, if I may use a terrestrial term. You observe that the land all has a slope hitherward from the distant range of mountains, and that between us and the sea there is a chain of hills. The metropolis lies at the lower edge of a vast basin, and it must be that the relatively porous surface, over many thousands of square miles, is underlain by an almost unbroken shell of rock, impermeable to water. The result is that the drainage of this whole immense region, after being collected under ground, flows together to this point, where the existence of a huge vent in the upper layer offers it a way of escape, and it comes spouting out of the great crater with the consequences which you behold." Many objections to Edmund's theory occurred to my mind; but he spoke so confidently, the course of things on this strange planet had so often followed his indications, and I felt myself so incapable of suggesting a more satisfactory hypothesis, that I made no reply, as a geologist, perhaps, would have done. At any rate the wonderful phenomenon existed before our eyes, explanation or no explanation. We learned afterwards that the river formed by the giant fountain passed through a gap in the hills to the seaward, and the more I reflected upon Edmund's idea the more acceptable I found it. A great deal of the water was led away from the foot of the plateau out of which the fountain issued by ditches constructed to irrigate the rich gardens surrounding the metropolis and the open agricultural country for many miles around. At the queen's invitation, although she did not accompany us, we inspected one of the power houses, and Edmund found the greatest delight in studying the details of the enormous dynamos and the system of cables by which, quite in our own manner, the electric power was conveyed to the city. We noticed that everywhere the most ingenious devices were employed for killing noise. "I knew we should find all this," said Edmund--"although I did not precisely anticipate the form that the natural supply of energy would take--as soon as I saw the aerial screws that give buoyancy to the great towers. In fact, I foresaw it as soon as I found, in inspecting the machinery of the air ship which brought us from the sea, that their motors were driven by storage batteries. It was obvious, then, that they had some extraordinary source of energy." "Oh, of course, you knew it all!" muttered Henry under his breath. "But if you were as omniscient as you think yourself, you'd not be in this fool's paradise." "What's that you're saying?" demanded Jack, partly catching the import of Henry's remark, and beginning to ruffle his feathers.