"Now, my friends," said the professor, "there will be little or nothing more to see until we again descend; I therefore propose that we return to the pilot-house, shut ourselves in, and at once test the soaring powers of the ship by rising to the highest attainable altitude." "Agreed!" said the baronet. "But why shut ourselves in?" "Because," answered the professor, "it will not only grow rapidly colder as we rise, but, if we remain outside, we shall also find it increasingly difficult to breathe as we reach the more rarefied air; whereas, by remaining inside, we shall be sheltered from the cold and shall be able to breathe the denser air which we shall take up with us." They accordingly entered the pilot-house, shutting the door after them, and closing all the windows; then the professor turned a full jet of vapour into the air-chambers for a moment, producing a perfect vacuum therein, and the ship at once began to mount into the ether with greatly accelerated speed, as they could easily see by watching the barometer, the bulb of which, completely protected, was situate outside the walls of the pilot-house. It was no very easy matter for cold to penetrate through the thin yet obdurate walls of the pilot-house; but by the time that the barometer had fallen to fifteen inches the voyagers experienced a distinct sensation of chilliness, whilst the windows of the pilot-house were thickly coated with a delicate frost tracery. Still the barometer continued to fall steadily, though not so rapidly as at first, indicating that the ship was still soaring upward; and with every inch fall of the mercury the professor became an increasingly interesting study of mingled delight and anxiety. At length the mercury, still falling, registered a height of eleven inches only, and the professor gave vent to a great sigh of relief. And when it further dropped to ten inches he could no longer contain himself. "Gentlemen," he exclaimed, "rejoice with me. The conquest of the mountains is ours. We are now as nearly as possible on a level with the topmost peak of Everest, the most lofty projection on the earth's surface; and in due time I hope we shall have the unique felicity of planting our feet on that as yet untrodden spot, and of leaving a record to that effect behind us." At length the mercury fell to a little below eight inches, and there it stopped; the limit of the _Flying Fish's_ buoyancy was reached. The professor stood intently regarding the barometer tube for some time; then he turned and said to his companions: