The top-hatted man was distinctly flattered by the Shaggy Man's mode of address. "Ah," he replied, "I can see that you recognize me as a person of importance. I am the Lord High Mayor of Hightown and my word here represents the highest law of the land. As for your being able to walk as we do on the air, I see no reason why you shouldn't since in Hightown there is no gravity to pull you to the earth." "What was that you said?--no gravity?" Twiffle was obviously excited. "Exactly," replied the Lord High Mayor with great dignity. "Within the boundaries of Hightown, the earth does not exert the least bit of gravity--none whatsoever." "Then that explains it," said Twiffle. "The Airmobile operates on the principle of gravity, and since there is no gravity here, the craft is useless." "What are we to do?" asked the Shaggy Man. "I am not sure I want to go walking around on the air, although these folks seem to take to it naturally enough." "Tell me," said Twiffle, addressing the Lord High Mayor, "is Hightown of very great area?" "Oh," exclaimed the Lord High Mayor, "it is simply enormous--no less than four square acres of the most delightful air!" "Have you any idea, your Honor," asked the Shaggy Man, "how we can get our flying machine out of Hightown?" "Oh, that's very simple," replied the Lord High Mayor. "Since your craft has only just crossed the boundary into Hightown, I would suggest that you get out and push the machine to the edge of the boundary--then push it a few inches more and it will be in the field of gravity again where it is equipped to operate." "Of course!" exclaimed Twiffle joyfully. "Why didn't I think of that?" The Lord High Mayor smiled with smug satisfaction. "I'll adjust these gravity plates now," continued Twiffle, "so the plane won't fall when it passes the boundary." After he had pressed some buttons, he and the Shaggy Man and Twink and Tom climbed out of the Airmobile. The air seemed as solid under their feet as the earth. Nevertheless, this walking on thin air was a most curious experience, and in spite of themselves they found they were treading gingerly, as though they were walking on eggs. The Lord High Mayor and the crowd of Hightowners that had gathered watched curiously as the Shaggy Man and Tom slowly pushed the Airmobile toward the boundary of Hightown. It was no task at all, since the Airmobile had no weight. They knew the sign that had greeted them as they entered Hightown marked the spot where gravity again exerted its pull, so they pushed the Airmobile slowly over this invisible line. Zoom! Like an arrow shot from a bow the Airmobile darted upward. Far above their heads it continued its mad climb into the sky. So fast did it move that within a few seconds it was visible only as a tiny speck far above them. "What in the sky has happened?" gasped the Shaggy Man.