Tom Swift tossed a quarter to the messenger boy, and leaped over the rail to the deck of his airship, making his way toward the pilot house.

"Start the motor, Ned," he called. "Are you all ready, Mr. Damon?"

"Bless my ancient history, yes. But--"

"Are you going, Tom?" asked Ned.

"Of course. That's why we're here; isn't it? We're going to start for the border to catch the smugglers. Give me full speed, I want the motor to warm up."

"But that message from Mr. Whitford? He says he has a new clew to the Fogers."

"That's all right. He may have, but he doesn't ask us to work it up. He says he will meet us in Logansville, and he can't if we don't go there. We're off for Logansville. Good-bye dad. I'll bring you back a souvenir, Mrs. Baggert," he called to the housekeeper. "Sorry you're not coming, Rad, but I'll take you next time."

"Dat's all right, Massa Tom. I doan't laik dem smugger-fellers, nohow. Good-bye an' good luck!"

"Bless my grab bag!" gasped Mr. Damon. "You certainly do things, Tom."

"That's the only way to get things done," replied the young inventor. "How about you, Ned? Motor all right?"

"Sure."

"Then let her go!"

A moment later Ned had started the machinery, and Tom, in the pilot house, had pulled the lever of the elevating rudder. Whizzing along, but making scarcely any sound, the noiseless airship mounted upward, and was off on her flight to capture the men who were cheating Uncle Sam.

"What are you going to do first, when you get there, Tom?" asked Ned, as he joined his chum in the pilot house, having set the motor and other apparatus to working automatically. "I mean in Logansville?"

"I don't know. I'll have to wait and see how things develop."

"That's where Mr. Foger lives, you know."

"Yes, but I doubt if he is there now. He and Andy are probably still in the old house here, though what they are doing is beyond me to guess."

"What do you suppose this new clew is that Mr. Whitford wired you about?"

"Haven't any idea. If he wants us to get after it he'll let us know. It won't take us long to get there at this rate. But I think I'll slow down a bit, for the motor is warmed up now, and there's no use racking it to pieces. But we're moving nicely; aren't we, Ned?"

"I should say so. This is the best all-around airship you've got."

"It is since I put the new motor in. Well, I wonder what will happen when we get chasing around nights after the smugglers? It isn't going to be easy work, I can tell you."

"I should say not. How you going to manage it?"

"Well, I haven't just decided. I'm going to have a talk with the customs men, and then I'll go out night after night and cruise around at the most likely place where they'll rush goods across the border. As soon as I see the outlines of an airship in the darkness, or hear the throb of her motor, I'll take after her, and--"

"Yes, and you can do it, too, Tom, for she can't hear you coming and you can flash the big light on her and the smugglers will think the end of the world has come. Cracky! Its going to be great, Tom! I'm glad I came along. Maybe they'll fight, and fire at us! If they have guns aboard, as they probably will have, we'll--"

"Bless my armor plate!" interrupted Mr. Damon. "Please don't talk about such hair-raising things, Ned! Talk about something pleasant."

"All right," agreed Tom's chum, and then, as the airship sailed along, high above the earth, they talked of many things.

"I think when we sight Logansville." said Tom, after a while, "that I will come down in some quiet spot, before we reach the city."

"Don't you want to get into a crowd?" asked Ned.

"No, it isn't that. But Mr. Foger lives there you know, and, though he may not be at home, there are probably some men who are interested in the thing he is working at."

"You mean smuggling?"

"Well, I wouldn't say that. At the same time it may have leaked out that we are after the smugglers in an airship and it may be that Mr. Whitford doesn't want the Fogers to know I'm on the ground until he has a chance to work up his clew. So I'll just go slowly, and remain in the background for a while."

"Well, maybe it's a good plan," agreed Tom.

"Of course," began Tom, "it would be--"

He was interrupted by a shout from Koku, who had gone to the motor room, for the giant was as fascinated over machinery as a child. As he yelled there came a grinding, pounding noise, and the big ship seemed to waver, to quiver in the void, and to settle toward the earth.

"Something's happened!" cried Ned, as he sprang for the place where most of the mechanism was housed.

"Bless my toy balloon!" shouted Mr. Damon. "We're falling, Tom!"

It needed but a glance at the needle of the barograph, to show this. Tom followed Ned at top speed, but ere either of them reached the engine room the pounding and grinding noises ceased, the airship began to mount upward again, and it seemed that the danger had passed.

"What can have happened?" gasped Tom.

"Come on, we'll soon see," said Ned, and they rushed on, followed by Mr. Damon, who was blessing things in a whisper.

The chums saw a moment later--saw a strange sight--for there was Koku, the giant, kneeling down on the floor of the motor room, with his big hands clasped over one of the braces of the bed-plate of the great air pump, which cooled the cylinders of the motor. The pump had torn partly away from its fastenings. Kneeling there, pressing down on the bed-plate with all his might, Koku was in grave danger, for the rod of the pump, plunging up and down, was within a fraction of an inch of his head, and, had he moved, the big taper pin, which held the plunger to the axle, would have struck his temple and probably would have killed him, for the pin, which held the plunger rigid, projected several inches from the smooth side of the rod.

"Koku, what is the matter? Why are you there?" cried Tom, for he could see nothing wrong with the machinery now. The airship was sailing on as before.

"Bolt break," explained the giant briefly, for he had learned some engineering terms since he had been with Tom. "Bolt that hold pump fast to floor crack off. Pump him begin to jump up. Make bad noise. Koku hold him down, but pretty hard work. Better put in new bolt, Mr. Tom."

They could see the strain that was put upon the giant in his swelling veins and the muscles of his hands and arms, for they stood out knotted, and in bunches. With all his great strength it was all Koku could do to hold the pump from tearing completely loose.

"Quick, Ned!" cried Tom. "Shut off all the power! Stop the pump! I've got to bolt it fast. Start the gas machine, Mr. Damon. You know how to do it. It works independent of the motor. You can let go in a minute, Koku!"

It took but a few seconds to do all this. Ned stopped the main motor, which had the effect of causing the propellers to cease revolving. Then the airship would have gone down but for the fact that she was now a balloon, Mr. Damon having started the generating machine which sent the powerful lifting gas into the big bag over head.

"Now you can let go, Koku," said Tom, for with the stooping of the motor the air pump ceased plunging, and there was no danger of it tearing loose.

"Bless my court plaster!" cried Mr. Damon. "What happened, Tom?"

As the giant arose from his kneeling position the cause of the accident could easily be seen. Two of the big belts that held down one end of the pump bed-plate to the floor of the airship, had cracked off, probably through some defect, or because of the long and constant vibration on them.

This caused a great strain on the two forward bolts, and the pump starter! to tear itself loose. Had it done so there would have been a serious accident, for there would have been a tangle in the machinery that might never have been repairable. But Koku, who, it seems, had been watching the pump, saw the accident as soon as it occurred. He knew that the pump must be held down, and kept rigid, and he took the only way open to him to accomplish this.

He pressed his big hands down over the place where the bolts had broken off, and by main strength of muscle he held the bed-plate in place until the power was shut off.

"Koku, my boy, you did a great thing!" cried Tom, when he realized what had happened. "You saved all our lives, and the airship as well."

"Koku glad," was the simple reply of the giant.

"But, bless my witch hazel!" cried Mr. Damon. "There's blood on your hands, Koku!"

They looked at the giant's palms. They were raw and bleeding.

"How did it happen?" asked Ned.

"Where belts break off, iron rough-like," explained Koku.

"Rough! I should say it was!" cried Tom. "Why, he just pressed with all his might on the jagged end of the belts. Koku you're a hero!"

"Hero same as giant?" asked Koku, curiously.

"No, it's a heap sight better," spoke Tom, and there was a trace of tears in his eyes.

"Bless my vaseline!" exclaimed Mr. Damon, blowing his nose harder than seemed necessary. "Come over here, Koku, and I'll bandage up your hands. Poor fellow, it must hurt a lot!"

"Oh, not so bad," was the simple reply.

While Mr. Damon gave first aid to the injured, Tom and Ned put new bolts in place of the broken ones on the bed-plate, and they tested them to see that they were perfect. New ones were also substituted for the two that had been strained, and in the course of an hour the repairs were made.

"Now we can run as an aeroplane again," said Tom. "But I'm not going to try such speed again. It was the vibration that did it I guess."

They were now over a wild and desolate stretch of country, for the region lying on either side of the imaginary line dividing Canada and New York State, at the point where the St. Lawrence flows north-east, is sparsely settled.

There were stretches of forest that seemed never to have been penetrated, and here and there patches of stunted growth, with little lakes dotted through the wilderness. There were hills and valleys, small streams and an occasional village.

"Just the place for smuggling," observed Tom, as he looked at a map, consulted a clock and figured out that they must be near Logansville. "We can go down here in one of these hollows, surrounded by this tangled forest, and no one would ever know we were here. The smugglers could do the same."

"Are you going to try it?" asked Ned.

"I think I will. We'll go up to quite a height now, and I'll see if I can pick out Logansville. That isn't much of a place I guess. When I sight it I'll select a good place to lay hidden for a day or two, until Mr. Whitford has had a chance to work up his clew."

The airship machinery was now working well again, and Tom sent his craft up about three miles. From there, taking observations through a powerful telescope, he was able, after a little while, to pick out a small town. From its location and general outline he knew it to be Logansville.

"We'll go down about three miles from it," he said to his chum. "They won't be likely to see us then, and we'll stay concealed for a while."

This plan was put into operation, and, a little later the Falcon came to rest in a little grassy clearing, located in among a number of densely wooded hills. It was an ideal place to camp, though very lonesome.

"Now, Ned, let's cut a lot of branches, and pile them over the airship," suggested Tom.

"Cover over the airship? What for?"

"So that in case anyone flies over our heads they won't look down and see us. If the Fogers, or any of the smugglers, should happen to pass over this place, they'd spot us in a minute. We've got to play foxy on this hunt."

"That's so," agreed his chum; and soon the three of them were busy making the airship look like a tangled mass of underbrush. Koku helped by dragging big branches along under his arm, but he could not use his hands very well.

They remained in the little grassy glade three days, thoroughly enjoying their camp and the rest. Tom and Ned went fishing in a nearby lake and had some good luck. They also caught trout in a small stream and broiled the speckled beauties with bacon inside them over live coals at a campfire.

"My! But that's good!" mumbled Ned, with his mouth full of hot trout, and bread and butter.

"Yes, I'd rather do this than chase smugglers," said Tom, stretching out on his back with his face to the sky. "I wish--"

But he did not finish the sentence. Suddenly from the air above them came a curious whirring, throbbing noise. Tom sat up with a jump! He and Ned gazed toward the zenith. The noise increased and, a moment later, there came into view a big airship, sailing right over their heads.

"Look at that!" cried Tom.

"Hush! They'll hear you," cautioned Ned.

"Nonsense! They're too high up," was Tom's reply. "Mr. Damon, bring me the big binoculars, please!" he called.

"Bless my spectacles, what's up?" asked the odd gentleman as he ran with the glasses toward Tom.

Our hero focused them on the airship that was swiftly sailing across the open space in the wilderness but so high up that there was no danger of our friends being recognized. Then the young inventor uttered a cry of astonishment.

"It's Andy Foger!" he cried. "He's in that airship, and he's got two men with him. Andy Foger, and it's a new biplane. Say, maybe that's the new clew Mr. Whitford wired me about. We must get ready for action! Andy in a new airship means business, and from the whiteness of the canvas planes, I should say that craft was on its first trip."