"Is it really Tank A, Tom?" cried Ned, through the tube, as soon as he became aware of his companion's intention. "Are you sure?"

"That's the girl, and just where you spotted her with the glasses--in that clump of bushes. But they've daubed her with green and brown paint--camouflaged her, so to speak-- until she looks like part of the landscape. What made you suspicious of that particular place?"

"The green was such a bright one in contrast to the rest of the foliage around it.',

"That's what struck me," Tom answered, as he continued to drive the Hawk earthward. "They thought they were doing a smart trick--imitating the tactics of the Allies with their tanks--but they must be color blind."

Ned took another observation through the glasses. He could see the tank more easily now. There she was, fairly well hidden in a clump of bushes and small trees on the banks of a river, about a hundred miles away from Shopton. It was in a wild and desolate country, and only with the airship could the trail have thus been followed.

Ned saw that the tank had been daubed with green, yellow, and brown paint, in fantastic blotches, to make the big machine blend with the foliage; and, to a certain extent, this had been accomplished.

But, as Ned had remarked, the green used was of too vivid a hue. No natural tree put forth leaves like that, and the glass had further revealed the error.

"Look, Tom!" suddenly cried Ned. "She's moving!"

"You're right!" answered the young inventor. "They've seen us and are trying to get away."

"But they can't beat your airship, Tom."

"I know that. But their game--Oh, Ned, they're going to wreck her!" cried Tom, and there was anguish in his voice.

As the two looked down from their seats In the Hawk they saw the tank, in its fantastic dress of splotchy paint, leave her lair amid the bushes and trees, and head toward the river. Like some ponderous prehistoric monster about to take a drink, she careened her way toward the stream, which, at this point, ran between high banks.

"What's the game?" cried Ned.

"They're going to send her to smash!" cried Tom. "She's pretty tough, Tom, but she'll never stand a tumble down into the river without breaking a lot of machinery inside her."

"But if they demolish the tank they'll kill themselves, won't they? And Koku and your men, too, who must be prisoners in her!"

"They won't risk their own worthless hides, you may be sure of that!" exclaimed Tom.

"There they go, but they must have left Koku and the others to their fate!"

"Oh, if they could only get loose and take control now, Tom, they'd save your tank for you!" shouted Ned.

"Yes; but they can't, I'm afraid. They may be killed, or so securely bound that they can't get loose!"

"Can't you get the Hawk there in time to stop her?"

"I'm afraid not. By that time she'll have attained top speed and it would be taking our lives in our bands to try to make a flying jump, get inside, and shut off the motors."

"Then the tank's got to smash!" said Ned gloomily.

Tom did not answer for a moment. He and his chum watched the fleeing figures running away from the war engine. What the plotters had done, as soon as they saw the aircraft and realized that Tom had discovered them, was to start the motors and leap from the tank, closing the doors after them. Whether or not they had left Koku and the others prisoners inside remained to be seen.

But the tank was plunging her way toward the steep bank of the river, doomed, it seemed, to great damage, if not to destruction.

"Oh, if we could only halt her!" murmured Ned.

Tom Swift was busy with some apparatus on the Hawk. Ned heard the hum of an electric motor which was connected with the engine, and there soon sounded the crackle of the wireless.

"What are you doing? Signaling for help from those inside the tank?" asked Ned, for the big machine was fitted to receive and send messages of this sort

"I'm trying something more desperate than that," Tom answered.

Again the wireless crackled, Tom working it with one hand while, with the other, he guided the aircraft. Ned looked downward with wondering eyes.

The tank was still plunging her way toward the steep bank of the river. If she tumbled down this, there would be little left of the expensive and complicated machinery inside.

"The rascals did their work well," mused Ned. "They've probably gotten all the secrets they want and now they're going to spoil all Tom's hard work. It's a shame! If only--"

Ned ceased his musing. Something was taking place down below that he could not explain. The tank seemed to be slackening her progress. More and more slowly she approached the edge of the cliff.

"Tom! Tom!" yelled Ned. "You must have waked some of them up inside and they've thrown the motors out of gear! Hurrah! She's stopping!"

"I believe she is!" yelled Tom. "Oh, if it only works!"

The tank was still moving, though more slowly. Still the crackle of the wireless was heard.

And then, just as Tom shut off his own motor and let the Hawk glide on her downward way in a volplane to earth, the great, ponderous tank came to a stop, on the very edge of the precipice at the foot of which rolled the river.

"Whew!" whistled Ned, as the aircraft rolled along the ground near the war machine. "That was touch and go, Tom! They stopped her just in time."

"You mean the wireless stopped her," said Tom quietly. "I'm very much afraid that if Koku and the others are alive they're still prisoners in the craft."

"The wireless!" gasped Ned, as he and his chum got out of the Hawk. "Do you mean that you stopped her by wireless, Tom?"

"That's what I did. It was a desperate chance, but I took it. I had just installed in the tank a system of wireless control, so she could be guided as some torpedos and submarines are, by wireless impulses from the shore.

"Only I'd never given the tank system a tryout. It was all installed, and had worked perfectly on the small model I constructed. And when I saw her running away, out of control as she was, I realized the wireless was the only thing that would stop her, if that would. It might operate just opposite to what I wanted, though, and increase her speed."

"But I took the chance. I set the airship wireless current to working, and tuned it in to coincide with the control of the tank. Then, by means of the wireless impulse I shut off the motors, which can he stopped or started by hand or by electricity. I shut 'em off."

"And only just in time!" cried Ned. "Whew, Tom Swift, but that was a close call!"

"I realize that myself!" said the young inventor. "This is a new idea and has to be worked out further for our newer tanks."

"Gee!" ejaculated Ned. "Out of date before got into use! Now let's see about our friends!"

It was the work of but a moment to enter the tank, and, after making sure that the machinery was all right, Tom and Ned made their way to the interior. In one of the smallest rooms they found Koku and the others bound with ropes, and in a bad way. Koku was so tied with cords and hemp as to resemble a bale of Manilla cable.

"Cut 'em loose, Ned!" cried Tom, and the bonds were soon severed. Then came explanations.

As has been told, one of the plotters, whose identity was not learned until later, came with the forged note. The giant and Tom's men set out in the tank, and the machine was stopped at a certain place where the plotter, who gave the name of Crossleigh, told them Tom was to meet his men.

Out of ambush leaped Simpson and others, who overpowered the mechanics, even subduing Koku after a fierce fight, and then they took possession of the tank, making the others prisoners.

What happened after that could only be conjectured by Tom's men, for they were shut up in an inner room. It seemed certain, though, that the tank was taken to some secret place and there painted to resemble the verdure. Then she went on again, coming to rest where Tom and Ned saw hen

Meanwhile the plotters were gradually getting at the secrets of construction, and they were in the midst of this work when one of them saw the aeroplane. Rightly guessing what it portended, they left hurriedly, still leaving the hapless men bound, and started the tank on what they thought would be her last trip.

"But you saved her, Tom!" cried Ned. "You saved her with the wireless."

And word was sent back to Shopton by the same means to tell Mr. Swift, Mr. Damon, and the others that Tom and his tank were safe. And then, a little later, when the bound men had recovered the use of their cramped limbs, the tank was backed away from the ledge and started on her homeward way, Tom and Ned preceding her in the Hawk.

Without further incident, save a slight break which was soon repaired, Tank A soon reached her harbor again, and a double guard was posted about the shop.

"And they won't get much more chance to steal her secrets," said Tom that night, when the stories had been told.

"Why?" asked Ned.

"We start to dismantle her at once," Tom answered, "and she goes to England to be reproduced for France."

"If only those plotters haven't stolen the secrets," mused Ned.

But if they had they got little good of them. For shortly afterward government secret service agents rounded up the chief members of the gang, including Simpson and Blakeson. They, with Schwen, were sent to an internment camp for the period of the war, and enough information was obtained from them to disclose all the workings of the plot.

"It was just like lots of other stunts the German spies tried to put over on the good old U.S.A.," said Tom to Ned, the day after the dismantled tank was shipped to Great Britain. "In some way the spies found out what I was making, and then they got hold of Blakeson and Grinder. Those fellows, who so nearly queered me in the big tunnel game promised to make a tank that would beat those the British at first put out, and they took some German money in advance for doing it.

"When they found they couldn't make good, the German spies agreed to help them get possession of my secrets. They worked hard enough at it, too, but, thanks to you, Ned, and to Eradicate, who gave us the tip on Schwen, we beat 'em out"

"And so it's all over, Tom?"

"Yes, practically all over. I've given all my interests in the tank to Uncle Sam. It was the only way I could do my bit, at this time. But I've something else up my sleeve."

And those of you who care to learn what the young inventor next did may do so by reading the next volume of this series.

It was about a week after Tank A, as she was still officially called, had been shipped in sections that Ned Newton called at Tom's home. He found his chum, with a flower in his buttonhole, about to leave in his small runabout

"Oh, excuse me!" exclaimed Ned. "This is Wednesday night. I might have known. Give Mary my regards."

"I will," promised Tom, with a smile."