Chapter IX. The Spies

"We're certainly going up!" yelled Ned, as he sat beside Tom in the cabin of the air glider.

"That's right!" agreed the young inventor rather proudly, as he grasped two levers, one of which steered the craft, the other being used to shift the weights. "We're going up. I was pretty sure of that. The next thing is to see if it will remain stationary in the air, and answer the rudder."

"Bless my top knot!" cried Mr. Damon. "You don't mean to tell me you can stand still in a gale of wind, Tom Swift."

"That's exactly what I do mean. You can't do it in an aeroplane, for that depends on motion to keep itself up in the air. But the glider is different. That's one of its specialties, remaining still, and that's why it will be valuable if we ever get to Siberia. We can hover over a certain spot in a gale of wind, and search about below with telescopes for a sign of the lost platinum mine.

"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 an elevation of four hundred feet, as evidenced by the barograph.

"I guess this is high enough," remarked Tom after a bit. "Now to see if she'll stand still."

Slowly he moved the weights along, by means of the compound levers, until the air glider was on an "even keel" so to speak. It was still moving forward, with the wind now, for Tom had warped his wing tips.

"The thing to do," said the young inventor, "is to get it exactly parallel with the wind-strata, so that the gale will blow through the two sets of planes, just as the wind blows through a box kite. Only we have