"That," I said, "is just what I need. Something to arouse my interest and exclude disquieting reflections. But what of this excursion beneath the waters of the lake? I had not heard of that." "Oh yes," said Oqua, "the Superintendent of Festivities would not think of slighting the Sea Rovers who make the navigation of our shallow lakes, bays and rivers safe for such vessels as the Silver King and their numerous passengers. They wanted to entertain our visitors from the outer world on their own vessel and of course the excursion beneath the water was made a part of the program." "Well, the arrangement," I said, "is better than I anticipated and it surely will be, to me, a novel experience to be able to see the world of marine life as the fishes see it." "And as the Sea Rovers see and improve it," said Oqua. "But see! They are signaling for us to come on board." In a few minutes we had passed out upon the dancing floor of the Rovers and descended into an elegantly furnished cabin. I was the only one present who had not become acquainted with the crew, and Oqua introduced me as the Scientist of the Ice King, to Captain Doris of the Sea Rover who gave me a cordial greeting and introduced me to a number of his comrades. In answer to my inquiries, he gave me an entertaining and instructive description of the duties of the submarine service. "Our work," he said, "is to keep a careful lookout for obstructions that might impede navigation and endanger life. This is especially necessary in rivers like the Cocytas, where huge stones are sometimes loosened from the rocky shores and fall into the channel, and sand-bars form rapidly. These are discovered and removed by the submarine patrols." "But how," I asked, "can you get at them?" "Nothing easier," said Doris, "as I will show you." At once I heard the water pouring into the hold and the Sea Rover sank to the bottom. The Captain and two of the crew passed into a little room at the rear of the cabin and immediately I noticed that the sides of the vessel were transparent and brilliantly lighted from the outside. Looking out I saw the men in diving suits leisurely walking around on the bottom, which looked like a smooth floor. Oqua explained that by means of powerful arc lights and reflectors, these submarine navigators were able to see for long distances even at great depths, and that the work of removing obstructions was carried on by means of machinery, and that the stones which fell into the channel were reduced to powder by powerful explosives, and the surface smoothed down like a well cultivated field. The air was continually renewed from stores of condensed air, while the poisonous exhalations from the lungs were absorbed by sponges having a peculiar affinity for carbon.