"Don't do that!" cried Mr. Whitford.

"What?" asked Tom, in some surprise.

"Don't destroy that letter. It may give us a clew. Let me have it. I'll put a man at work on that end of this game."

"Bless my checkerboard!" cried Mr. Damon. "This game has so many ends that you don't know where to begin to play it."

The government man smoothed out the crumpled piece of paper, and looked at it carefully, and also gazed at the envelope.

"It's pretty hard to identify plain print, done with a lead pencil," he murmured. "And this didn't came through the mail."

"I wonder how it got here?" mused Ned. "Maybe some of the crowd that was here when we started off dropped it for the smugglers. Maybe the smugglers were in that crowd!"

"Let's take a look outside," suggested Mr. Whitford. "We may be able to pick up a clew there."

Although our friends were tired and sleepy, and hungry as well, they forgot all this in the desire to learn more about the mysterious warning that had come to them during the night. They all went outside, and Ned pointed to where he had picked up the envelope.

"Look all around, and see if you can find anything more," directed the custom agent.

"Footprints won't count," said Tom. "There was a regular circus crowd out here yesterday."

"I'm not looking for footprints," replied Mr. Whitford, "I have an idea--"

"Here's something!" interrupted Mr. Damon. "It looks like a lead weight for a deep-sea fishing line. Bless my reel. No one could do fishing here."

"Let me see that!" exclaimed Mr. Whitford eagerly. Then, as he looked at it, he uttered a cry of delight. "I thought so," he said. "Look at this bit of cord tied to the weight."

"What does that signify?" asked Tom.

"And see this little hole in the envelope, or, rather a place that was a hole, but it's torn away now."

"I'm not much the wiser," confessed Ned, with a puzzled look.

"Why, it's as plain as print," declared the government agent. "This warning letter was dropped from an airship, Tom."

"From an airship?"

"Yes. They sailed right over this place, and let the letter fall, with this lead weight attached, to bring it to earth just where they wanted it to fall."

"Bless my postage stamp!" cried Mr. Damon. "I never heard of such a thing."

"I see it now!" exclaimed Tom. "While we were off over the river, watching for the smugglers, they were turning a trick here, and giving us a warning into the bargain. We should have stayed around here. I wonder if it was Andy's airship that was used?"

"We can easily find that out," said Mr. Whitford. "I have a detective stationed in a house not far from where the Fogers live. Andy came back from Shopton yesterday, just before you arrived here, and I can soon let you know whether he was out last night. I'll take this letter with me, and get right up to my office, though I'm afraid this won't be much of a clew after all. Print isn't like handwriting for evidence."

"And to think they sailed right over this place, and we weren't home," mourned Tom. "It makes me mad!"

But there was no use in regretting what had happened, and, after a hot breakfast in the airship, with Mr. Damon presiding at the electrical stove, they all felt more hopeful. Mr. Whitford left for his office, promising to send word to Tom as to whether or not Andy was abroad in the airship during the night.

"I wonder if that 'Committee of Three' is Andy and these two fellows with him in the airship?" asked Ned.

"Hard telling," responded his chum. "Now for a good sleep. Koku, keep the crowd away while we have a rest," for the giant had indulged in a good rest while the airship was on patrol during the night.

Not so much of a crowd came out as on the first day, and Koku had little trouble in keeping them far enough away so that Tom and the others could get some rest. Koku walked about, brandishing a big club, and looking as fierce as a giant in a fairy tale. It was afternoon when a message came from Mr. Whitford to the effect that Andy's airship was not out the previous night, and that so far no clews had developed from the letter, or from any other source.

"We'll just have to keep our eyes open," wrote Mr. Whitford. "I think perhaps we are altogether wrong about the Fogers, unless they are deeper than I give them credit for. It might be well to let the smugglers think you are frightened, and go away for a day or so, selecting a more secluded spot to remain in. That may cause them to get bolder, and we may catch them unawares."

"That's a good plan. I'll try it," decided Tom. "We'll move to-morrow to a new location."

"Why not to-night?" asked Ned.

"Because it's getting late, and I want to circle about in daylight and pick out a good place. Morning will do all right."

"Then you're not going out to-night?"

"No. Mr. Whitford writes that as goods were smuggled over last night it will hardly be likely that they will repeat the trick to-night. We'll have a little rest."

"Going to mount guard?" asked Ned.

"No, I don't think so. No one will disturb us."

Afterward the young inventor wished that he had kept a better watch that night, for it nearly proved disastrous for him.

It must have been about midnight that Tom was awakened by a movement in the airship.

"Who's that?" he asked suddenly.

"Koku," came the reassuring reply. "Too hot to sleep in my bunk. I go out on deck."

"All right, Koku," and Tom dozed off again.

Suddenly he was awakened by the sound of a terrific scuffle on deck. Up he jumped, rushing toward the door that led from his sleeping cabin.

"What is it! What's the matter!" he cried.

There came the sound of a blow, a cry of pain, and then the report of a gun.

"Bless my cartridge belt!" cried Mr. Damon.

"What's the matter? Who is it? What happened?" yelled Ned, tumbling out of his bunk.

"Something wrong!" answered Tom, as he switched on the electric lights. He was just in time to see Koku wrench a gun from a man who stood near the pedestal, on which the great searchlight was poised. Tossing the weapon aside, Koku caught up his club, and aimed a blow at the man. But the latter nimbly dodged and, a moment later leaped over the rail, followed by the giant.

"Who is he? What did he do?" cried Tom after his big servant. "What happened?"

"Him try to shoot searchlight, but I stop him!" yelled back Koku, as he rushed on in pursuit. With a leap Tom sprang to the switch of his lantern, and sent a flood of light toward where Koku was racing after the intruder.

Full in the glare of the powerful beam from the light there was revealed the giant and the man he was pursuing. The latter neither Tom, nor any one on the airship, knew. All they could see was that he was racing away at top speed, with Koku vainly swinging his club at him.

"Bless my chicken soup!" cried Mr. Damon. "Is anything damaged, Tom?"

"No, Koku was too quick for him." yelled the youth, as he, too leaped over the rail and joined in the pursuit.

"Stop! Stop!" called Koku to the man who had sought to damage the great searchlight. But the fellow knew better than to halt, with an angry giant so close behind him. He ran on faster than ever.

Suddenly the stranger seemed to realize that by keeping in the path of the light he gave his pursuers a great advantage. He dodged to one side, off the path on which he had been running, and plunged into the bushes.

"Where him go?" called Koku, coming to a puzzled halt.

"Ned, play the light on both sides!" ordered Tom to his chum, who was now on the deck of the airship, near the wheels and levers that operated the big lantern. "Show him up!"

Obediently the young bank clerk swung the searchlight from side to side. The powerful combined electric current, hissing into the big carbons, and being reflected by the parabolic mirrors, made the growth of underbrush as brightly illuminated as in day time. Tom detected a movement.

"There he is, Koku!" he called to his giant servant. "Off there to the left. After him!"

Raising his club on high, Koku made a leap for the place where the fugitive was hiding. As the man saw the light, and sprang forward, he was, for a moment, in the full glare of the rays. Then, just as the giant was about to reach him, Koku stumbled over a tree root, and fell heavily.

"Never mind, I'll get him!" yelled Tom, but the next moment the man vanished suddenly, and was no longer to be seen in the finger of light from the lantern. He had probably dipped down into some hollow, lying there hidden, and as of course was out of the focus of the searchlight.

"Come on, Koku, we'll find him!" exclaimed Tom, and together they made a search, Mr. Damon joining them, while Ned worked the lantern. But it was of no avail, for they did not find the stranger.

"Well, we might as well go back," said Tom, at length. "We can't find him. He's probably far enough off by this time."

"Who was he?" panted Mr. Damon, as he walked beside Tom and Koku to the airship. Ned had switched off the big light on a signal from the young inventor.

"I don't know!" answered Tom.

"But what did he want? What was he doing? I don't quite understand."

"He wanted to put my searchlight out of commission," responded our hero. "From that I should argue that he was either one of the smugglers, or trying to aid them."

And this theory was borne out by Mr. Whitford, who, on calling the next morning, was told of the occurrence of the night. Koku related how he had found it uncomfortable in his bunk, and had gone out on deck for air. There, half dozing, he heard a stealthy step. At once he was on the alert. He saw a man with a gun creeping along, and at first thought the fellow had evil designs on some of those aboard the Falcon.

Then, when Koku saw the man aim at the big searchlight the giant sprang at him, and there was a scuffle. The gun went off, and the man escaped. An examination of the weapon he had left behind showed that it carried a highly explosive shell, which, had it hit the lantern, would have completely destroyed it, and might have damaged the airship.

"It was the smugglers, without a doubt," declared Mr. Whitford. "You can't get away from this place any too soon, Tom. Get a new hiding spot, and I will communicate with you there."

"But they are on the watch," objected Ned. "They'll see where we go, and follow us. The next time they may succeed in smashing the lantern."

"And if they do," spoke Tom, "it will be all up with trying to detect the smugglers, for it would take me quite a while to make another searchlight. But I have a plan."

"What is it?" asked the government agent.

"I'll make a flight to-day," went on the young inventor, "and sail over quite an area. I'll pick out a good place to land, and we'll make our camp there instead of here. Then I'll come back to this spot, and after dark I'll go up, without a light showing. There's no moon to-night, and they'll have pretty good eyes if they can follow me, unless they get a searchlight, and they won't do that for fear of giving themselves away. We'll sail off in the darkness, go to the spot we have previously picked out, and drop down to it. There we can hide and I don't believe they can trace us."

"But how can you find in the darkness, the spot you pick out in daylight?" Mr. Whitford wanted to know.

"I'll arrange some electric lights, in a certain formation in trees around the landing place," said Tom. "I'll fix them with a clockwork switch, that will illuminate them at a certain hour, and they'll run by a storage battery. In that way I'll have my landing place all marked out, and, as it can only be seen from above, if any of the smugglers are on the ground, they won't notice the incandescents."

"But if they are in their airship they will," said Mr. Damon.

"Of course that's possible," admitted Tom, "but, even if they see the lights I don't believe they will know what they mean. And, another thing, I don't imagine they'll come around here in their airship when they know that we're in the neighborhood, and when the spy who endeavored to damage my lantern reports that he didn't succeed. They'll know that we are likely to be after them any minute."

"That's so," agreed Ned. "I guess that's a good plan."

It was one they adopted, and, soon after Mr. Whitford's visit the airship arose, with him on board, and Tom sent her about in great circles and sweeps, now on high and again, barely skimming over the treetops. During this time a lookout was kept for any other aircraft, but none was seen.

"If they are spying on us, which is probably the case," said Tom, "they will wonder what we're up to. I'll keep 'em guessing. I think I'll fly low over Mr. Foger's house, and see if Andy has his airship there. We'll give him a salute."

Before doing this, however, Tom had picked out a good landing place in a clearing in the woods, and had arranged some incandescent lights on high branches of trees. The lights enclosed a square, in the centre of which the Falcon was to drop down.

Of course it was necessary to descend to do this, to arrange the storage battery and the clock switch. Then, so as to throw their enemies off their track, they made landings in several other places, though they did nothing, merely staying there as a sort of "bluff" as Ned called it.

"They'll have their own troubles if they investigate every place we stopped at," remarked Tom, "and, even if they do hit on the one we have selected for our camp they won't see the lights in the trees, for they're well hidden."

This work done, they flew back toward Logansville, and sailed over Andy's house.

"There he is, on the roof, working at his airship!" exclaimed Ned, as they came within viewing distance, and, surely enough, there was the bully, tinkering away at his craft. Tom flew low enough down to speak to him, and, as the Falcon produced no noise, it was not difficult to make their voices heard.

"Hello, Andy!" called Tom, as he swept slowly overhead.

Andy looked up, but only scowled.

"Nice day; isn't it?" put in Ned.

"You get on away from here!" burst out the bully. "You are trespassing, by flying over my house, and I could have you arrested for it. Keep away."

"All right," agreed Tom with a laugh. "Don't trespass by flying over our ship, Andy. We also might have a gun to shoot searchlights with," he added.

Andy started, but did not reply, though Tom, who was watching him closely, thought he saw an expression of fear come over the bully's face.

"Do you think it was Andy who did the shooting?" asked Ned.

"No, he hasn't the nerve," replied Tom. "I don't know what to think about that affair last night."

"Excepting that the smugglers are getting afraid of you, and want to get you out of the way," put in the custom official.

That night, when it was very dark, the Falcon noiselessly made her way upward and sailed along until she was over the square in the forest, marked out by the four lights. Then Tom sent her safely down.

"Now let 'em find us if they can!" the young inventor exclaimed, as he made the craft fast. "We'll turn in now, and see what happens to-morrow night."

"I'll send you word, just as soon as I get any myself," promised Mr. Whitford, when he left the next morning.

Tom and Ned spent the day in going over the airship, making some minor repairs to it, and polishing and oiling the mechanism of the searchlight, to have it in the best possible condition.

It was about dusk when the wireless outfit, with which the Falcon was fitted, began snapping and cracking.

"Here comes a message!" cried Tom, as he clapped the receiver over his head, and began to translate the dots and dashes.

"It's from Mr. Whitford!" he exclaimed, when he had written it down, and had sent back an answer, "He says: 'Have a tip that smugglers will try to get goods over the border at some point near Niagara Falls to-morrow night. Can you go there, and cruise about? Better keep toward Lake Ontario also. I will be with you. Answer.'"

"What answer did you send?" asked Ned.

"I told him we'd be on the job. It's quite a little run to make, and we can't start until after dark, or otherwise some of the smugglers around here may see us, and tip off their confederates. But I guess we can make the distance all right."

Mr. Whitford arrived at the airship the next afternoon, stating that he had news from one of the government spies to the effect that a bold attempt would be made that night.

"They're going to try and smuggle some diamonds over on this trip," said the custom agent.

"Well, we'll try to nab them!" exclaimed Tom.

As soon as it was dark enough to conceal her movements, the Falcon was sent aloft, not a light showing, and, when on high, Tom started the motor at full speed. The great propellers noiselessly beat the air, and the powerful craft was headed for Lake Ontario.

"They're pretty good, if they attempted to cross the lake to-night," observed the young inventor, as he looked at the barometer.

"Why so?" asked Ned.

"Because there's a bad storm coming up. I shouldn't want to risk it. We'll keep near shore. We can nab them there as good as over the lake."

This plan was adopted, and as soon as they reached the great body of water--the last in the chain of the Great Lakes--Tom cruised about, he and Ned watching through powerful night glasses for a glimpse of another airship.

Far into the night they sailed about, covering many miles, for Tom ran at almost top speed. They sailed over Niagara Falls, and then well along the southern shore of Ontario, working their way north-east and back again. But not a sign of the smugglers did they see.

Meanwhile the wind had arisen until it was a gale, and it began to rain. Gently at first the drops came down, until at length there was a torrent of water descending from the overhead clouds. But those in the Falcon were in no discomfort.

"It's a bad storm all right!" exclaimed Tom, as he looked at the barometer, and noted that the mercury was still falling.

"Yes, and we have had our trouble for our pains!" declared Mr. Whitford.

"What do you mean?"

"I mean I believe that we have been deceived by a false clew. The smugglers probably had no intention of getting goods across at this point to-night. They saw to it that my agent got false information, believing that we would follow it, and leave the vicinity of Logansville."

"So they could operate there?" asked Tom.

"That's it," replied the agent. "They drew us off the scent. There's no help for it. We must get back as soon as we can. My! This is a bad storm!" he added, as a blast careened the airship.

For a time the Falcon shot onward through the storm and darkness, for Tom did not want to give up. With but a single shaded light in the pilot house, so that he could see to read the gauges and dials, telling of the condition of the machinery in the motor room, he pushed his stanch craft ahead. At times she would be forced downward toward the angry waters of Lake Ontario, over which she was sailing, but the speed of her propellers and the buoyancy of the gas bag, would soon lift her again.

"How much longer are you going to stay?" called Ned in his chum's ear--called loudly, not to be heard above the noise of the airship, but above the racket of the gale.

"Oh, I guess we may as well start back," spoke Tom, after a look at the clock on the wall. "We can just about make our camp by daylight, and they won't see us."

"It won't be light very early," observed Mr. Whitford, looking in the pilot house from the cabin, just aft of it. "But there is no use waiting around here any more, Tom. They gave us a false clew, all right."

"Bless my police badge!" cried Mr. Damon. "They must be getting desperate."

"I believe they are," went on the custom officer. "They are afraid of us, and that's a good sign. We'll keep right after 'em, too. If we don't get 'em this week, we will next. Better put back."

"I will," decided the young inventor.

"It certainly is a gale," declared Ned, as he made his way along a dim passage, as few lights had been set aglow, for fear of the smugglers seeing the craft outlined in the air. Now, however, when it was almost certain that they were on the wrong scent, Tom switched on the incandescents, making the interior of the Falcon more pleasant.

The giant came into the pilot house to help Tom, and the airship was turned about, and headed toward Logansville. The wind was now sweeping from the north across Lake Ontario, and it was all the powerful craft could do to make headway against it.

There came a terrific blast, which, in spite of all that Tom and Koku could do, forced the Falcon down, dangerously close to the dashing billows.

"Hard over, Koku!" called Tom to his giant.

As the airship began to respond to the power of her propellers, and the up-tilted rudder, Tom heard, from somewhere below him, a series of shrill blasts on a whistle.

"What's that?" he cried.

"Sounds like a boat below us," answered Mr. Whitford.

"I guess it is," agreed the young inventor. "There she goes again."

Once more came the frantic tooting of a whistle, and mingled with it could be heard voices shouting in fear, but it was only a confused murmur of sound. No words could be made out.

"That's a compressed air whistle!" decided Tom. "It must be some sort of a motor boat in distress. Quick, Mr. Whitford! Tell Ned to switch on the searchlight, and play it right down on the lake. If there's a boat in this storm it can't last long. Even an ocean liner would have trouble. Get the light on quick, and we'll see what we can do!"

It was the work of but an instant to convey the message to Ned. The latter called Mr. Damon to relieve him in the motor room, and, a few seconds later, Ned had switched on the electricity. By means of the lazy-tongs, and the toggle joints, the bank clerk lifted the lantern over until the powerful beam from it was projected straight down into the seething waters of the lake.

"Do you see anything?" asked Mr. Damon from the motor room, at one side of which Ned stood to operate the lantern.

"Nothing but white-caps," was the answer. "It's a fearful storm."

Once more came the series of shrill whistles, and the confused calling of voices. Ned opened a window, in order to hear more plainly. As the whistle tooted again he could locate the sound, and, by swinging the rays of the searchlight to and fro he finally picked up the craft.

"There she is!" he cried, peering down through the plate glass window in the floor of the motor room. "It's a small gasolene boat, and there are several men in her! She's having a hard time."

"Can we rescue them?" asked Mr. Damon.

"If anybody can, Tom Swift will," was Ned's reply. Then came a whistle from the speaking tube, that led to the pilot house.

"What is it?" asked Ned, putting the tube to his ear.

"Stand by for a rescue!" ordered Tom, who had also, through a window in the floor of the pilot house, seen the hapless motor boat. The men in it were frantically waving their hands to those on the airship. "I'm going down as close as I dare," went on Tom. "You watch, and when it's time, have Koku drop from the stern a long, knotted rope. That will be a sort of ladder, and they can make it fast to their boat and climb up, hand over hand. It's the only plan."

"Good!" cried Ned. "Send Koku to me. Can you manage alone in the pilot house?"

"Yes," came back the answer through the tube.

Koku came back on the run, and was soon tying knots in a strong rope. Meanwhile Ned kept the light on the tossing boat, while Tom, through a megaphone had called to the men to stand by to be rescued. The whistle frantically tooted their thanks.

Koku went out on the after deck, and, having made the knotted rope fast, dropped the end overboard. Then began a difficult feature of airship steering. Tom, looking down through the glass, watched the boat in the glare of the light. Now coming forward, now reversing against the rush of the wind; now going up, and now down, the young inventor so directed the course of his airship so that, finally, the rope dragged squarely across the tossing boat.

In a trice the men grabbed it, and made it fast. Then Tom had another difficult task--that of not allowing the rope to become taut, or the drag of the boat, and the uplift of the airship might have snapped it in twain. But he handled his delicate craft of the air as confidently as the captain of a big liner brings her skillfully to the deck against wind and tide.

"Climb up! Climb up!" yelled Tom, through the megaphone, and he saw, not a man, but a woman, ascending the knotted rope, hand over hand, toward the airship that hovered above her head.

"Bless my knitting needles!" cried Mr. Damon, as he looked down, and saw, in the glare of the great light, the figure of the woman clinging to the swaying rope. "Help her, someone! Tom! Ned! She'll fall!"

The eccentric man started to rush from the motor room, where he had been helping Ned. But the latter cried:

"Stay where you are, Mr. Damon. No one can reach her now without danger to himself and her. She can climb up, I think."

Past knot after knot the woman passed, mounting steadily upward, with a strength that seemed remarkable.

"Come on!" cried Tom to the others. "Don't wait until she gets up. There isn't time. Come on--the rope will hold you all! Climb up!"

The men in the tossing and bobbing motor boat heard, and at once began, one after the other, to clamber up the rope. There were five of them, as could be seen in the glare of the light, and Tom, as he watched, wondered what they were doing out in the terrific storm at that early hour of the morning, and with a lone woman.

"Stand by to help her, Koku!" called Ned to the giant.

"I help," was the giant's simple reply, and as the woman's head came above the rail, over which the rope ran, Koku, leaning forward, raised her in his powerful arms, and set her carefully on the deck.

"Come into the cabin, please," Ned called to her. "Come in out of the wet."

"Oh, it seems a miracle that we are saved!" the woman gasped, as, rain-drenched and wind-tossed, she staggered toward the door which Tom had opened by means of a lever in the pilot house. The young inventor had his hands full, manipulating the airship so as to keep it above the motor boat, and not bring too great a strain on the rope.

The woman passed into the cabin, which was between the motor room and the pilot house, and Ned saw her throw herself on her knees, and offer up a fervent prayer of thanksgiving. Then, springing to her feet, she cried:

"My husband? Is he safe? Can you save him? Oh, how wonderful that this airship came in answer to our appeals to Providence. Whose is it?"

Before Ned got a chance to answer her, as she came to the door of the motor room, a man's voice called:

"My wife! Is she safe?"

"Yes, here I am," replied the woman, and a moment later the two were in each other's arms.

"The others; are they safe?" gasped the woman, after a pause.

"Yes," replied the man. "They are coming up the rope. Oh, what a wonderful rescue! And that giant man who lifted us up on deck! Oh, do you recall in Africa how we were also rescued by airship--"

"Come on now, I got you!" interrupted the voice of Koku out on the after deck, and there was a series of thumps that told when he had lifted the men over the rail, and set them down.

"All saved!" cried the giant at last.

"Then cut the rope!" shouted Tom. "We've got to get out of this, for it's growing worse!"

There was the sound of a hatchet blow, and the airship shot upward. Into the cabin came the dripping figures of the other men, and Ned, as he stood by the great searchlight, felt a wave of wonder sweep over him as he listened to the voices of the first man and woman.

He knew he had heard them before, and, when he listened to the remark about a rescue by airship, in Africa, a flood of memory came to him.

"Can it be possible that these are the same missionaries whom Tom and I rescued from the red pygmies?" he murmured. "I must get a look at them."

"Our boat, it is gone I suppose," remarked one of the other men, coming into the motor room.

"I'm afraid so," answered Ned, as he played the light on the doomed craft. Even as he did so he saw a great wave engulf her, and, a moment later she sank. "She's gone," he said softly.

"Too bad!" exclaimed the man. "She was a fine little craft. But how in the world did you happen along to rescue us? Whose airship is this?"

"Tom Swift's," answered Ned, and, at the sound of the name the woman uttered a cry, as she rushed into the motor room.

"Tom Swift!" she exclaimed. "Where is he? Oh, can it be possible that it is the same Tom Swift that rescued us in Africa?"

"I think it is, Mrs. Illingway," spoke Ned quietly, for he now recognized the missionary, though he wondered what she and her husband were doing so far from the Dark Continent.

"Oh, I know you--you're Ned Newton--Tom's chum! Oh, I am so glad! Where is Tom?"

"In the pilot house. He'll be here in a moment."

Tom came in at that juncture, having set the automatic steering geer to take the ship on her homeward course.

"Are they all saved?" he asked, looking at the little group of persons who had climbed up from the motor boat. "Mr. Damon, you had better make some hot coffee. Koku, you help. I--"

"Tom Swift!" cried out Mr. and Mrs. Illingway together, as they made a rush for the young inventor. "Don't you know us?"

To say that Tom was surprised at this, would be putting it mildly. He had to lean up against the side of the cabin for support.

"Mrs. Illingway!" he gasped. "You here--were you in that boat?"

"Yes. it's all very simple. My husband and I are on a vacation for a year. We got fever and had to leave Africa. We are staying with friends at a resort on the lake shore. These are our friends," she went on, introducing the other gentlemen.

"We went out for a trip in the motor boat," the missionary continued, "but we went too far. Our motor broke down, we could get no help, and the storm came up. We thought we were doomed, until we saw your lights. I guessed it was a balloon, or some sort of an airship, and we whistled; and called for help. Then you rescued us! Oh, it is almost too wonderful to believe. It is a good thing I have practiced athletics or I never could have climbed that rope."

"It is like a story from a book!" added Mr. Illingway, as he grasped Tom's hand. "You rescued us in Africa and again here." I may say here that the African rescue is told in detail in the volume entitled, "Tom Swift and His Electric Rifle."

The shipwrecked persons were made as comfortable as possible. There was plenty of room for them, and soon they were sitting around warm electric heaters, drinking hot coffee, and telling their adventures over again. Mr. and Mrs. Illingway said they soon expected to return to Africa.

Tom told how he happened to be sailing over the lake, on the lookout for smugglers, and how he had been disappointed.

"And it's a good thing you were--for our sakes," put in Mrs. Illingway, with a smile.

"Where do you want to be landed?" asked Tom. "I don't want to take you all the way back to Logansville."

"If you will land us anywhere near a city or town, we can arrange to be taken back to our cottage," said one of the men, and Tom sent the airship down until, in the gray dawn of the morning, they could pick out a large village on the lake shore. Then, in much better condition than when they had been saved, the rescued ones alighted, showering Tom and the others with thanks, and sought a hotel.

"And now for our camp, and a good rest!" cried the young inventor, as he sent the airship aloft again.

They reached their camp in the forest clearing without having been observed, as far as they could learn, and at once set about making things snug, for the storm was still raging.

"I don't believe any of the smugglers were abroad last night," remarked Mr. Whitford, as he prepared to go back into town, he having come out on horseback, leaving the animal over night in an improvised stable they had made in the woods of boughs and tree branches.

"I hope not," replied Tom, but the next day, when the government agent called again, his face wore a look of despair.

"They put a big one over on us the night of the rescue." he said. "They flew right across the border near Logansville, and got away with a lot of goods. They fooled us all right."

"Can you find out who gave the wrong tip?" asked Tom.

"Yes, I know the man. He pretended to be friendly to one of my agents, but he was only deceiving him. But we'll get the smugglers yet!"

"That's what we will!" cried Tom, determinedly.

Several days passed, and during the night time Tom, in his airship, and with the great searchlight aglow, flew back and forth across the border, seeking the elusive airships, but did not see them. In the meanwhile he heard from Mr. and Mrs. Illingway, who sent him a letter of thanks, and asked him to come and see them, but, much as Tom would liked to have gone, he did not have the time.

It was about a week after the sensational rescue, when one evening, as Tom was about to get ready for a night flight, he happened to be in the pilot house making adjustments to some of the apparatus.

Mr. Damon and Ned had gone out for a walk in the woods, and Mr. Whitford had not yet arrived. As for Mr. Koku, Tom did not know where his giant servant was.

Suddenly there was a commotion outside. A trampling in the bushes, and the breaking of sticks under feet.

"I got you now!" cried the voice of the giant.

Tom sprang to the window of the pilot house. He saw Koku tightly holding a man who was squinting about, and doing his best to break away. But it was useless. When Koku got hold of any one, that person had to stay.

"What is it, Koku!" cried Tom.

"I got him!" cried the giant. "He sneaking up on airship, but I come behind and grab him," and Koku fairly lifted his prisoner off his feet and started with him toward the Falcon.

"Hello!" cried Tom. "What's up, Koku?"

"Him up!" replied the giant with a laugh, as he looked at his squirming prisoner, whose feet he had lifted from the ground.

"No, I mean what was he doing?" went on Tom, with a smile at the literal way in which the giant had answered his question.

"I wasn't doing anything!" broke in the man. "I'd like to know if I haven't a right to walk through these woods, without being grabbed up by a man as big as a mountain? There'll be something up that you won't like, if you don't let me go, too!" and he struggled fiercely, but he was no match for giant Koku.

"What was he doing?" asked Tom of his big servant, ignoring the man. Tom looked closely at him, however, but could not remember to have seen him before.

"I walking along in woods, listen to birds sing," said Koku simply, taking a firmer hold on his victim. "I see this fellow come along, and crawl through grass like so a snake wiggle. I to myself think that funny, and I watch. This man he wiggle more. He wiggle more still, and then he watch. I watch too. I see him have knife in hand, but I am no afraid. I begin to go like snake also, but I bigger snake than he."

"I guess so," laughed Tom, as he watched the man trying in vain to get out of Koku's grip.

"Then I see man look up at balloon bag, so as if he like to cut it with knife. I say to myself, 'Koku, it is time for you to go into business for yourself.' You stand under me?"

"I understand!" exclaimed Tom. "You thought it was time for you to get busy."

"Sure," replied Koku. "Well, I get business, I give one jump, and I am so unlucky as to jump with one foot on him, but I did not mean it. I go as gentle as I can."

"Gentle? You nearly knocked the wind out of me!" snarled the prisoner. "Gentle! Huh!"

"I guess he was the unlucky one, instead of you," put in Tom. "Well, what happened next?"

"I grab him, and--he is still here," said Koku simply. "He throw knife away though."

"I see," spoke Tom. "Now will you give an account of yourself, or shall I hand you over to the police?" he asked sternly of the man. "What were you sneaking up on us in that fashion for?"

"Well, I guess this isn't your property!" blustered the man. "I have as good a right here as you have, and you can't have me arrested for that."

"Perhaps not," admitted Tom. "You may have a right on this land, but if you are honest, and had no bad intentions, why were you sneaking up, trying to keep out of sight? And why did you have a big knife?"

"That's my business, young man."

"All right, then I'll make it my business, too," went on the young inventor. "Hold him, Koku, until I can find Mr. Damon, or Ned, and I'll see what's best to be done. I wish Mr. Whitford was here."

"Aren't you going to let me go?" demanded the man.

"I certainly am not!" declared Tom firmly. "I'm going to find out more about you. I haven't any objections to any one coming to look at my airship, out of curiosity, but when they come up like a snake in the grass and with a big knife, then I get suspicious, and I want to know more about them."

"Well, you won't know anything more about me!" snarled the fellow. "And it will be the worse for you, if you don't let me go. You'd better!" he threatened.

"Don't pay any attention to him, Koku," said Tom. "Maybe you'd better tie him up. You'll find some rope in the motor room."

"Don't you dare tie me up!" blustered the prisoner.

"Go ahead and tie him," went on Tom. "You'll be free to guard the ship then. I'll go for Ned and Mr. Damon."

"Tie who up? What's the matter?" asked a voice, and a moment later the government agent came along the woodland path on his horse. "What's up, Tom? Have you captured a wild animal?"

"Not exactly a wild animal. Mr. Whitford. But a wild man. I'm glad you came along. Koku has a prisoner." And Tom proceeded to relate what had happened.

"Sneaking up on you with a knife; eh? I guess he meant business all right, and bad business, too," said Mr. Whitford. "Let me get a look at him, Tom," for Koku had taken his prisoner to the engine room, and there, amid a storm of protests and after a futile struggle on the part of the fellow, had tied him securely.

Tom and the custom officer went in to look at the man, just as Ned and Mr. Damon came back from their stroll in the woods. It was rapidly getting dusk, and was almost time for the start of the usual flight, to see if any trace could be had of the smugglers.

"There he is," said Tom, waving his hand toward the bound man who sat in a chair in one corner of the motor room. The young inventor switched on the light, and a moment later Mr. Whitford exclaimed:

"Great Scott! It's Ike Shafton!"

"Do you know him?" asked Tom eagerly.

"Know him? I should say I did! Why he's the man who pretended to give one of my men information about smugglers that drew us off on the false scent. He pretended to be for the government, and, all the while, he was in with the smugglers! Know him? I should say I did!"

A queer change had come over the prisoner at the sight of Mr. Whitford. No longer was Shafton surly and blustering. Instead he seemed to slink down in his chair, bound as he was, as if trying to get out of sight.

"Why did you play double?" demanded the government agent, striding over to him.

"I--I--don't hit me!" whined Shafton.

"Hit you! I'm not going to hit you!" exclaimed Mr. Whitford, "but I'm going to search you, and then I'm going to wire for one of my men to take you in custody."

"I--I didn't do anything!"

"You didn't; eh? Well, we'll see what the courts think of giving wrong information to Uncle Sam with the intent to aid criminals. Let's see what he's got in his pockets."

The spy did not have much, but at a sight of one piece of paper Mr. Whitford uttered a cry of surprise.

"Ha! This is worth something!" he exclaimed. "It may be stale news, and it may be something for the future, but it's worth trying. I wonder I didn't think of that before."

"What is it?" asked Tom.

For answer the custom officer held out a scrap of paper on which was written one word.

St. Regis.

"What does it mean," asked Ned, who, with Mr. Damon, had entered the motor room, and stood curiously regarding the scene.

"Bless my napkin ring!" said the odd man. "That's the name of a hotel. Do you suppose the smugglers are stopping there?"

"Hardly," replied Mr. Whitford with a smile. "But St. Regis is the name of an Indian reservation in the upper part of New York state, right on the border, and in the corner where the St. Lawrence and the imaginary dividing line between New York and Canada join. I begin to see things now. The smugglers have been flying over the Indian Reservation, and that's why they have escaped us so far. We never thought of that spot. Tom, I believe we're on the right track at last! Shafton was probably given this to inform him where the next trick would be turned, so he could get us as far away as possible, or, maybe prevent us leaving at all."

An involuntary start on the part of the prisoner seemed to confirm this, but he kept silent.

"Of course," went on Mr. Whitford, "they may have already flown over the St. Regis reservation, and this may be an old tip, but it's worth following up."

"Why don't you ask him?" Tom wanted to know, as he nodded toward Shafton.

"He wouldn't tell the truth. I'll put him where he can't get away to warn his confederates, and then we'll go to the reservation. And to think that my man trusted him!"

Mr. Whitford was soon in communication with his headquarters by means of the wireless apparatus on Tom's airship, and a little later two custom officers arrived, with an extra horse on which they were to take their prisoner back.

"And now we'll try our luck once more," said Mr. Whitford as his men left with Shafton securely bound. "Can you make the reservation in good time, Tom? It's quite a distance," and he pointed it out on the map.

"Oh, I'll do it," promised the young inventor, as he sent his powerful craft aloft in the darkness. Then, with her nose pointed in the right direction, the Falcon beat her way forward through the night, flying silently, with the great searchlight ready for instant use.

In comparatively short time, though it was rather late at night, they reached the St. Lawrence, and then it was an easy matter to drop down into the midst of the reservation grounds. Though the redmen, whom the state thus quartered by themselves, had all retired, they swarmed out of their cabins as the powerful light flashed back and forth.

"We want to question some of the head men of the tribe," said Mr. Whitford. "I know some of them, for on several occasions I've had to come here to look into rumors that tobacco and liquor and other contraband goods dear to the Indian heart were smuggled into the reservation against the law. I never caught any of them at it though."

With guttural exclamations, and many grunts of surprise, the redmen gathered around the big airship. It was too much even for their usual reserve, and they jabbered among themselves.

"How Big Foot!" greeted the custom officer, to one Indian who had an extremely large left foot. "How!"

"How!" responded the Indian, with a grunt.

"Plenty much fine air-bird; eh?" and the agent waved his hand toward the Falcon.

"Yep. Plenty much big."

"Big Foot never see bird like this; eh?"

"Oh sure. Big Foot see before many times. Huh!"

"What! Has he seen this before?" asked Tom.

"No. Wait a minute," cautioned Mr. Whitford. "I'm on the track of something. Big Foot see air-bird like this?" he questioned.

"Sure. Fly over Indians' land many times. Not same as him," and he nodded toward Tom's ship, "but plenty much like. Make heap noise. Come down once--break wheel mebby. Indians help fix. Indians get firewater. You got firewater in your air-bird?"

"No firewater, but maybe we've got some tobacco, if you tell us what we want to know, Big Foot. And so you've seen air-birds flying around here before?"

"Sure, Heap times. We all see," and he waved his hand to indicate the redmen gathered around him.

There came grunts of confirmation.

"We're getting there!" exclaimed Mr. Whitford to Tom. "We're on the right track now. Which way air-birds come, Big Foot?"

"Over there," and he pointed toward Canada.

"Which way go?"

"Over there," and he pointed toward the east, in the direction of Shopton, as much as anywhere.

"That's what we want to know. Tom, we'll just hang around here for a while, until one of the smugglers' airships pass over head. I believe one is due to-night, and that's why Shafton had that paper. It was sent to him to tip him off. He was sneaking up, trying to put your airship out of commission when Koku caught him. These Indians have used their eyes to good advantage. I think we're on the trail at last."

"Baccy for Big Foot?" asked the redman.

"Yes, plenty of it. Tom, give them some of Koku's, will you? I'll settle with you later," for the giant had formed a liking for the weed, and Tom did not have the heart to stop him smoking a pipe once in a while. With his usual prodigality, the giant had brought along a big supply, and some of this was soon distributed among the Indians, who grunted their thanks.

"What plan have you in mind?" asked Tom of Mr. Whitford, when some of the Indians had gone back to their shanties, leaving a few staring curiously at the airship, as she rested on the ground, bathed in the glow of her electric lights.

"Well, I think the best thing we can do is just to stay right here, Tom; all night if need be. As Big Foot says, there have been airships passing overhead at frequent intervals. Of course that is not saying that they were the smugglers, but I don't see who else they could be. There's no meet going on, and no continental race. They must be the smugglers."

"I think so," put in Ned.

"Bless my diamond ring!" exclaimed Mr. Damon. "But what are you going to do when you see them overhead?"

"Take after them, of course!" exclaimed Tom. "That's what we're here for; isn't it Mr. Whitford?"

"Yes. Do you think you can rise from the ground, and take after them in time to stand a chance of overhauling them, Tom? You know they may go very fast."

"I know, but I don't believe they can beat the Falcon. I'd rather wait down here than hover in the air. It isn't as dark as it was the other night, and they might see us with their glasses. Then they would turn back, and we'd have our trouble for nothing. They've actually got to cross the border with smuggled goods before the law can touch them; haven't they?"

"Yes, I couldn't arrest them on Canadian territory, or over it. I've got to get them on this side of the border. So perhaps it will be as well to lie here. But do you suppose you can hear them or see them, as they fly over?"

"I'm pretty sure I can. The sound of their motor and the whizz of the propellers carries for some distance. And then, too, I'm going to set the searchlight to play a beam up in the air. If that gets focused on 'em, we'll spot 'em all right."

"But suppose they see it, and turn back?"

"I don't believe they will. The beam will come from the ground straight upward you know, and they won't connect it with my ship."

"But that fellow who was sneaking up when Koku caught him, may find some way to warn them that you have come here," suggested Ned.

"He won't get much chance to communicate with his friends, while my men have him," said Mr. Whitford significantly. "I guess we'll take a chance here, Tom."

So it was arranged. Everything on the airship was gotten ready for a quick flight, and then Tom set his great searchlight aglow once more. Its powerful beams cut upward to the clouds, making a wonderful illumination.

"Now all we have to do is to wait and watch," remarked Tom, as he came back from a last inspection of the apparatus in the motor room.

"And that is sometimes the hardest kind of work," said Mr. Whitford. "Many a time I have been watching for smugglers for days and nights at a stretch, and it was very wearying. When I got through, and caught my man, I was more tired than if I had traveled hundreds of miles. Just sitting around, and waiting is tiresome work."

The others agreed with him, and then the custom officer told many stories of his experiences, of the odd places smugglers would hit upon to conceal the contraband goods, and of fights he had taken part in.

"Diamonds and jewels, from their smallness, and from the great value, and the high duty on them when brought into the United States, form the chief articles of the high class smugglers," he said. "In fact the ones we are after have been doing more in diamonds than anything else, though they have, of late, brought much valuable hand-made lace. That can be bought comparatively cheap abroad, and if they can evade paying Uncle Sam the duty on it, they can sell it in the United States at a large profit."

"But the government has received so many complaints from legitimate dealers, who can not stand this unfair competition, that we have been ordered to get the smugglers at any cost."

"They are sharp rascals," commented Mr. Damon. "They seem to be making more efforts since Tom Swift got on their trail."

"But, just the same, they are afraid of him, and his searchlight," declared Mr. Whitford. "I guess they fancied that when they took to airships to get goods across the border that they would not be disturbed. But two can play at that game."

The talk became general, with pauses now and then while Tom swept the sky with the great searchlight, the others straining their eyes for a sight of the smugglers' airships. But they saw nothing.

The young inventor had just paid a visit to the pilot house, to see that his wheels and guiding levers were all right, and was walking back toward the stern of the ship, when he heard a noise there, and the fall of a heavy body.

"Who's that?" he cried sharply. "Is that you, Koku?"

A grunt was the only answer, and, as Tom called the giant's name the big man came out.

"What you want, Mr. Tom?" he asked.

"I thought you were at the stern," spoke Tom. "Someone is there. Ned, throw the light on the stern!" he called sharply.

In a moment that part of the ship was in a bright glare and there, in the rays of the big lantern, was stretched out Big Foot, the Indian, comfortably sleeping.

"Here! What are you doing?" demanded Mr. Whitford, giving him a vigorous shake.

"Me sleep!" murmured Big Foot. "Lemme be! Me sleep, and take ride to Happy Hunting Grounds in air-bird. Go 'way!"

"You'll have to sleep somewhere else, Big Foot," spoke the agent with a laugh. "Koku, put him down under one of the trees over there. He can finish his nap in the open, it's warm."

The Indian only protested sleepily, as the giant carried him off the ship, and soon Big Foot was snoring under the trees.

"He's a queer chap," the custom officer said. "Sometimes I think he's a little off in his head. But he's good natured."

Once more they resumed their watching. It was growing more and more wearisome, and Tom was getting sleepy, in spite of himself.

Suddenly the silence of the night was broken by a distant humming and throbbing sound.

"Hark!" cried Ned.

They all listened intently.

"That's an airship, sure enough!" cried Tom.

He sprang to the lever that moved the lantern, which had been shut off temporarily. An instant later a beam of light cut the darkness. The throbbing sounded nearer.

"There they are!" cried Ned, pointing from a window toward the sky. A moment later, right into the glare of the light, there shot a powerful biplane.

"After 'em, Tom!" shouted Mr. Whitford.

Like a bird the Falcon shot upward in pursuit noiselessly and resistlessly, the beam of the great searchlight playing on the other craft, which dodged to one side in an endeavor to escape.

"On the trail at last!" cried Tom, as he shoved over the accelerator lever, sending his airship forward on an upward slant, right at the stern of the smugglers' biplane.

Upward shot the Falcon. With every revolution of her big propellers she came nearer and nearer to the fleeing craft of the supposed smugglers who were using every endeavor to escape.

"Do you think you can catch them, Tom?" asked Mr. Whitford as he stood at the side of our hero in the pilot house, and looked upward and forward to where, bathed in the light of the great search-lantern, the rival craft was beating the air.

"I'm sure we can--unless something happens."

"Bless my overshoes! What can happen?" asked Mr. Damon, who, after finding that everything in the motor room was running smoothly, had come forward. Ned was attending to the searchlight. "What can happen, Tom?"

"Almost anything, from a broken shaft to a short-circuited motor. Only, I hope nothing does occur to prevent us from catching them."

"You don't mean to say that you're actually going to try to catch them, do you, Tom?" asked the custom officer, "I thought if we could trail them to the place where they have been delivering the goods, before they shipped them to Shopton we'd be doing well. But I never thought of catching them in mid-air."

"I'm going to try it," declared the young inventor. "I've got a grappling anchor on board," he went on, "attached to a meter and windlass. If I can catch that anchor in any part of their ship I can bring them to a stop, just as a fisherman lands a trout. Only I've got to get close enough to make a cast, and I want to be above them when I do it."

"Don't you think you can catch them, Tom?" asked Mr. Damon.

"Well, I'm pretty sure I can, and yet they seem to have a faster biplane than I gave them credit for. I guess I'll have to increase our speed a little," and he shifted a lever which made the Falcon shoot along at nearly doubled speed.

Still the other airship kept ahead, not far, but sufficiently so to prevent the grappling anchor from being tossed at her rail.

"I wonder if they are the smugglers?" questioned Mr. Damon. "It might be possible, Tom, that we're chasing the wrong craft."

"Possible, but not probable," put in Mr. Whitford. "After the clew we got, and what the Indians told us, and then to have a biplane come sailing over our heads at night, it's pretty sure to be the one we want. But, Tom, can't you close up on 'em?"

"I'm going to try. The machinery is warmed up now, and I'll send it to the limit."

Once more he adjusted the wheels and levers, and at his touch the Falcon seemed to gain new strength. She fairly soared through the air.

Eagerly those in the pilot house watched the craft they were pursuing. She could be seen, in the glare of the big searchlight, like some bird of gloom and evil omen, fluttering along ahead of them.

"They certainly have a fine motor!" cried Tom. "I was sure I could have caught up to them before this."

"How do you account for it?" asked Mr. Damon.

"Well, they're flying a good deal lighter than we are. They probably have no load to speak of, while we carry a heavy one, to say nothing of Koku."

"Diamonds aren't very heavy," put in Mr. Whitford grimly. "I think they are smuggling diamonds to-night. How I wish we could catch them, or trace them to where they have their headquarters."

"We'll do it!" declared Tom.

"Bless my stars! They've gone!" suddenly exclaimed Mr. Damon. "They've disappeared, Tom, I can't see them."

It was indeed true. Those in the pilot house peering ahead through the darkness, could not get a glimpse of the airship they were pursuing. The beam of the searchlight showed nothing but a black void.

All at once the beam shifted downward, and then it picked up the white-winged craft.

"They went down!" cried Tom. "They tried to drop out of sight."

"Can't you get them?" asked Mr. Whitford.

"Oh, yes, we can play that game too. I'll do a little volplaning myself," and the young inventor shut off the power and coasted earthward, while Ned, who had picked up the forward craft, kept the searchlight playing on her.

And now began a wonderful chase. The smugglers' craft, for such she proved later to be, did her best to dodge the Falcon. Those managing the mechanism of the fleeing airship must have been experts, to hold out as they did against Tom Swift, but they had this advantage, that their craft was much lighter, and more powerfully engined as regards her weight. Then, too, there were not so many on board, and Tom, having a combined balloon and aeroplane, had to carry much machinery.

It was like the flight of two big birds in the air. Now the smugglers' craft would be mounting upward, with the Falcon after her. Again she would shoot toward the earth, and Tom would follow, with a great downward swoop.

Ned kept the great lantern going, and, though occasionally the craft they were after slipped out of the focus of the beams, the young bank clerk would pick her up again.

To the right and left dodged the forward airship, vainly endeavoring to shake off Tom Swift, but he would not give up. He followed move for move, swoop for swoop.

"She's turning around!" suddenly cried Mr. Damon. "She's given up the flight, Tom, and is going back!"

"That's so!" agreed Mr. Whitford. "They're headed for Canada, Tom. We've got to catch 'em before they get over the Dominion line!"

"I'll do it!" cried Tom, between his clenched teeth.

He swung his airship around in a big circle, and took after the fleeing craft. The wind was against the smugglers now, and they could not make such good speed, while to Tom the wind mattered not, so powerful were the propellers of the Falcon.

"I think we're gaining on them," murmured Mr. Damon.

Suddenly, from the engine room, came a cry from Ned.

"Tom! Tom!" he shouted, "Something is wrong with the gas machine! She registers over five hundred pounds pressure, and that's too much. It's going up, and I haven't touched it!"

"Mr. Damon, take the wheel!" exclaimed the young inventor. "I've got to see what's wrong. Hold her right on their trail."

Tom sprang to the motor room, and one glance at the gas generating machine showed him that they were in dire peril. In some manner the pressure was going up enormously, and if it went up much more the big tank would blow to pieces.

"What is it?" cried Ned, from his position near the light.

"I don't know! Something wrong."

"Are you going to give up the chase?"

"I am not. Stick to the light. Koku, tell Mr. Damon to hold her on the course I set. I'll try to get this pressure down!" And Tom Swift began to work feverishly, while his ship rushed on through the night in danger, every moment, of being blown to atoms. Yet the young inventor would not give up, and descend to earth.

The chase was kept up, and Tom, when he had a chance to look up at the speed register, as he labored frantically at the clogged gas machine, saw that they were rushing along as they never had before.

"Are we catching them, Ned?" he cried to his chum, who was not far away, playing the powerful light on the smugglers' craft.

"I think we're coming closer, but it's going to be a long chase. I don't see why we can't close up on 'em."

"Because they've got a very fast ship, Ned, and they are flying much lighter than we are. But we'll get 'em!"

"How are you making out with that gas machine?"

"Well, I'm doing all I can, but I can't seem to get the pressure down. I can't understand it. Some of the pipes must be clogged with a carbon deposit. I ought to have cleaned them out some time ago."

Ned gave a hasty glance at the gauge which showed the gas pressure. It registered six hundred pounds now, having risen a hundred in a short time.

"And she'll go up, sure, at eight hundred," murmured Ned, as he held the light steadily on the smugglers' aircraft. "Well, if Tom sticks to the chase, I will too, but I think it would be better to go down, open up everything, and let the gas escape. We could get the rascals later."

Tom, however, did not seem to think so, for he kept on with his task, working away at the pipes, trying to force the obstruction out, so that the gas from the generator would flow into the bag. At the same time he tried to shut off the generating apparatus, but that had become jammed in consequence of the pipe clogging, and the powerful vapor continued to manufacture itself automatically in spite of all that Tom could do.

The only safe way out of the danger, unless he could remove the obstruction, was to descend to earth, and, as Ned had said, open every outlet. But to have done that in mid-air would have been dangerous, as the large volume of gas, suddenly liberated, would have hung about the airship in a cloud, smothering all on board. If they were on the earth they could run away from it, and remain away until the vapor had blown off.

"Is Mr. Damon keeping her on the course, Ned?" asked Tom, pausing a moment to get his breath after a series of frantic efforts.

"Yes, and I think we're closing in on them a little."

"That's good. Are they still headed for the border?"

"Yes, I guess they're going to take no chances to-night. They're going right back to Canada where they came from."

"Well, we'll be hot after 'em. Whistle through the tube, and tell Koku to come here and give me a hand. He's with Mr. Damon in the pilot house."

Ned sent the message, and then gave his whole attention to the light. This was necessary, as the smugglers were resorting to dodging tactics, in an endeavor to escape. Now they would shoot upward, and again toward the earth, varying the performance by steering to the right or left. Ned had constantly to shift the light to keep them in focus, so that Mr. Damon could see where to steer, but, with all this handicap, the eccentric man did very well, and he was never far out in his judgment.

"By Jove!" suddenly murmured Tom, as he tried once more in vain to open a clogged valve. "I'm afraid we can't do it. Koku, lend a hand here!" he exclaimed as the giant entered. "See if you can twist this wrench around, but don't break off the handle, whatever you do."

"Me shove," replied the giant simply, as he grasped the big wrench.

Once more Ned glanced at the pressure gage. It showed seven hundred pounds now, and there was only a margin of safety of one hundred pounds more, ere a terrific explosion would occur. Still Tom had not given the order to descend to earth.

"Are you going to make it, Tom?" asked the government agent, anxiously, as he stood over the young inventor.

"I--I think so," panted Tom. "Are we near the Dominion line,"

"Pretty close," was the discouraging answer. "I'm afraid we can't get 'em before they cross. Can you use any more speed?"

"I don't know. Ned, see if you can get another notch out of her."