"I admit at once that this great body could not be steered, nor in any degree guided by any apparatus that we could devise," assented the Doctor. "But that we should be obliged to float aimlessly, hither and thither, altogether the creatures of chance, I do not for a moment admit. The equator, receiving as it does, the vertical rays of the sun, is by far the hottest portion of the earth. The atmosphere at that quarter, being constantly superheated and correspondingly rarified, ascends into the vault above. This creates a semi-vacuum below, and the cooler atmospheres north and south of the equator rush in and fill the aforesaid vacuum. Pouring in from opposite directions with an impetus that often amounts to hurricanes, they boil up as they meet, miles into the firmament above. They then set off in two strong currents toward either Pole. What is the natural inference? The navigators of our air-ship have the power to raise and lower at pleasure. Obviously, there is but one thing for sensible men to do: Let her rise until we strike a northerly current, if necessary, and remain in it so long as it is favorable; when it changes, rise or lower until another favorable current is found, etc. Do you happen to think of any more 'insuperable' obstacles, my dear sir?" "Well, I must say that while I am not convinced of the practicability of your scheme, still you meet my objections in a way that is quite surprising, and which shows that you have given the matter much thought; yet I am not sure that you will not run upon difficulties that will make it altogether impossible. For instance, there is the cost of so vast an undertaking. It would cost hundreds of thousands, at the least calculation." "Now, Denison, you have struck the only real difficulty that I can think of. I really have no idea of who will furnish the money. I had not thought even of asking anyone to do so." Patients came in at this juncture, and Denison took his departure. A few days later, however, he returned, and when the Doctor was at leisure, opened the conversation by asking if anything had developed with regard to the air-ship building. "O, ho!" cried Dr. Jones, "you are getting into my way of thinking on that subject, are you?" "Well, to tell you the truth, I have thought of it considerably since I saw you. I would like, at least, to see it tried." "There is but one way to do: If you get interested sufficiently to wish to take hold, we will see if we cannot stir up our friends and form a stock company. Or, failing in that, we might have a working model built, and I think we could induce the Government to take hold of the matter." Denison called frequently during the following month, and it was evident that he was fast becoming imbued with the Doctor's ideas and enthusiasm. CHAPTER II. Two Men Resolve to Go Picnicking.