In a few minutes the “Albatross” glided across the Yellowstone River, leaving Mount Stevenson on the right, and coasting the large lake which bears the name of the stream. Great was the variety on the banks of this basin, ribbed as they were with obsidian and tiny crystals, reflecting the sunlight on their myriad facets. Wonderful was the arrangement of the islands on its surface; magnificent were the blue reflections of the gigantic mirror. And around the lake, one of the highest in the globe, were multitudes of pelicans, swans, gulls and geese, bernicles and divers. In places the steep banks were clothed with green trees, pines and larches, and at the foot of the escarpments there shot upwards innumerable white fumaroles, the vapor escaping from the soil as from an enormous reservoir in which the water is kept in permanent ebullition by subterranean fire. The cook might have seized the opportunity of securing an ample supply of trout, the only fish the Yellowstone Lake contains in myriads. But the “Albatross” kept on at such a height that there was no chance of indulging in a catch which assuredly would have been miraculous. In three quarters of an hour the lake was overpassed, and a little farther on the last was seen of the geyser region, which rivals the finest in Iceland. Leaning over the rail, Uncle Prudent and Phil Evans watched the liquid columns which leaped up as though to furnish the aeronef with a new element. There were the Fan, with the jets shot forth in rays, the Fortress, which seemed to be defended by waterspouts, the Faithful Friend, with her plume crowned with the rainbows, the Giant, spurting forth a vertical torrent twenty feet round and more than two hundred feet high. Robur must evidently have been familiar with this incomparable spectacle, unique in the world, for he did not appear on deck. Was it, then, for the sole pleasure of his guests that he had brought the aeronef above the national domain? If so, he came not to receive their thanks. He did not even trouble himself during the daring passage of the Rocky Mountains, which the “Albatross” approached at about seven o’clock. By increasing the speed of her wings, as a bird rising in its flight, the “Albatross” would clear the highest ridges of the chain, and sink again over Oregon or Utah, But the maneuver was unnecessary. The passes allowed the barrier to be crossed without ascending for the higher ridges. There are many of these canyons, or steep valleys, more or less narrow, through which they could glide, such as Bridger Gap, through which runs the Pacific Railway into the Mormon territory, and others to the north and south of it.