"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 no string to hold us from moving. We have to depend on the equalization of friction on the surfaces of the wings. I wonder if I can do it."

It was a delicate operation, and Tom had not had much experience in that sort of thing, for his other airships and aeroplanes worked on an entirely different principle. But he moved the weights along, inch by inch, and flexed the tips, planes and rudders until finally Ned, who was looking down through the floor window, cried out

"We're stationary!"

"Good!" exclaimed Tom. "Then it's a success."

"And we can go to Siberia?" added Mr. Damon.

"Sure," assented the young inventor. "And if we have luck we'll rescue Mr. Petrofsky's brother, and get a lot of platinum that will be more valuable than gold."

It would not be true to say that the air glider was absolutely stationary. There was a slight forward motion, due to the fact that it was not yet perfected, and also because Tom was not expert enough in handling it.

The friction on the plane surfaces was not equalized, and the gale forced the craft along slightly. But, compared to the terrific power of the wind, the air glider was practically at a standstill, and this was remarkable when one considers the force of the hurricane that was blowing above below and through it.

For actually that was what the hurricane was doing. It was as if an immense box kite was suspended in the air, without a string to hold it from moving, and as though a cabin was placed amidships to hold human beings.

"This sure is great!" cried Ned. "Have you got her in control, Tom?"

"I think so. I'll try and see how she works."

By shifting the weights, changing the balance, and warping the wings, the young inventor sent the craft higher up, made it dip down almost to the earth, and then swoop upward like some great bird. Then he turned it completely about and though he developed no great speed in this test made it progress quarteringly against the wind,

"It's almost perfect," declared Tom. "A few touches and she'll be all right."

"Is it all right?" asked Ivan Petrofsky anxiously, as the three left the cabin, and Eradicate hitched his mule to the glider to take it back to the shed.

"I see where it can be improved," he said, as they made ready to descend. "I'll soon have it in shape."

"Then we can go to Siberia?"

"In less than a month. The big airship needs some repairs, and then we'll be off."

The Russian said nothing, but he looked his thanks to Tom, and the manner in which he grasped the hand of our hero showed his deep feelings.

The glider was given several more trials, and each time it worked better. Tom decided to change some of the weights, and he devoted all his time to this alteration, while Ned, Mr. Damon, and the others labored to get the big airship in shape for the long trip to the land of the exiles.

So anxious was Tom to get started, that he put in several nights working on the glider. Ned occasionally came over to help him, while Mr. Damon was on hand as often as his wife would allow. Mr. Petrofsky spent his nights writing to friends in Russia, hoping to get some clew as to the whereabouts of his brother.

It was on one of these nights, when Tom and Ned were laboring hard, with Eradicate to help them that an incident occurred which worried them all not a little. Tom was adjusting some of the new weights on the sliding rods, and called to Ned:

"I say, old man, hand me that big monkey wrench, will you. I can't loosen this nut with the small one. You'll find it on the bench by that back window."

As Ned went to get the tool he looked from the casement. He started, stood staring through the glass for a moment into the outer darkness, and then cried out:

"Tom, we're being watched! There are some spies outside!"

"What?" exclaimed the young inventor "Where are they? Who are they?"

"I don't know. Those Russian police, maybe out front, and maybe we can catch them!"

Grabbing up the big monkey wrench, Ned made a dash for the large sliding doors, followed by Tom who had an iron bar, and Eradicate with a small pair of pliers.

"By golly!" cried the colored man, "ef I gits 'em I'll pinch dere noses off!"