"How high are you going up?" demanded Ned, for the air glider was still mounting upward on a slant. If you ever scaled a flat piece of tin, or a stone, you'll remember how it seems to slide up a hill of air, when it was thrown at the right angle. It was just this way with the air glider—it was mounting upward on a slant.
"I'm going up a couple of hundred feet at least," answered Tom, "and higher if the gale-strata is there. I want to give it a good test while I'm at it."
Ned looked down through a heavy plate of glass in the floor of the cabin, and could see Mr. Petrofsky and Eradicate looking up at them.
"Bless my handkerchief!" cried Mr. Damon, when his attention had been called to this. "It's just like an airship."
"Except that we haven't a bit of machinery on board," said Tom. "These weights do everything," and he shifted them forward on the sliding rods, with the effect that the air glider dipped down with a startling lurch.
"We're falling!" cried Ned.
"Not a bit of it," answered Tom. "I only showed you how it worked. By sliding the weights back we go up."
He demonstrated this at once, sending his craft sliding up another hill of air, until it reached
