"Your questions are quite practical, and I am ready to answer them. There are to be three skins or coverings to our globe, with a foot of space (or air blanket, if you please) between them. This affords us two air chambers that materially prevent the radiation of heat. Once heated, a very little fuel will keep the interior of our great air-ship at the desired temperature. You see, at the inferior or lower part of the ship, a square apartment attached, plentifully supplied with windows. That represents the living and store rooms. The living rooms are to be comfortably furnished, and no reason can be alleged why we should not enjoy in them absolute comfort. In our store-rooms, we will carry one year's supply of food. And in tanks of sufficient size, petroleum (or whatever combustible we conclude to be most suitable) for heating and cooking purposes. See?" "I see," said Denison. "You will observe that so conservative of heat is this arrangement that every particle of caloric created in the living rooms, or cabin below, helps by that much to float the great globe. All the warmth from cooking and heating; the heat and smoke from our pipes and cigars; yea, even the animal heat which radiates from our bodies, all subserve the one great purpose and function--keeping up the temperature and buoyant effort of the globe. Do you begin to catch on?" fairly shouted the enthusiastic Doctor. "Well, it looks very well so far," returned Denison slowly. "But, my dear sir, I foresee one difficulty that in your enthusiasm you seem to have overlooked. You can never guide or steer this immense ship. It must go with the wind, and you are just as likely to go to the South Pole as to the North, and very unlikely to go to either. You must excuse me, but this last is certainly an insuperable obstacle to your making anything practicable of your idea."