Without loss of time the young inventor and the aeronaut began to repair the damage done to the Red Cloud by colliding with the tower. The most important part to reconstruct was the propeller, and Mr. Sharp decided to make two, instead of one, in order to have an extra one in case of future accidents.  
Tom's task was to arrange the mechanism so that, hereafter, the rudder could not become jammed, and so prevent the airship from steering properly. This the lad accomplished by a simple but effective device which, when the balloonist saw it, caused him to compliment Tom.
 
"That's worth patenting," he declared. "I advise you to take out papers on that."
 
"It seems such a simple thing," answered the youth. "And I don't see much use of spending the money for a patent. Airships aren't likely to be so numerous that I could make anything off that patent."
 
"You take my advice," insisted Mr. Sharp. "Airships are going to be used more in the future than you have any idea of. You get that device patented."
 
Tom did so, and, not many years afterward he was glad that he had, as it brought him quite an income.
 
It required several days' work on the Red Cloud before it was in shape for another trial. During the hours when he was engaged in the big shed, helping Mr. Sharp, the young inventor spent many minutes calling to mind the memory of a certain fair face, and I think I need not mention any names to indicate whose face it was.
 
"She promised to go for a ride with me," mused the lad. "I hope she doesn't back out. But I'll want to learn more about managing the ship before I venture with her in it. It won't do to have any accidents then. There's Ned Newton, too. I must take him for a skim in the clouds. Guess I'll invite him over some afternoon, and give him a private view of the machine, when we get it in shape again."
 
About a week after the accident at the school Mr. Sharp remarked to Tom one afternoon:
 
"If the weather is good to-morrow, we'll try another flight. Do you suppose your father will come along?"
 
"I don't know," answered the lad. "He seems much engrossed in something. It's unusual, too, for he most generally tells me what he is engaged upon. However, I guess he will say something about it when he gets ready."
 
"Well, if he doesn't feel just like coming, don't argue him. He might be nervous, and, while the ship is new, I don't want any nervous passengers aboard. I can't give them my attention and look after the running of the machinery."
 
"I was going to propose bringing a friend of mine over to see us make the trip to-morrow," went on the young inventor. "Ned Newton, you know him. He'd like a ride."
 
"Oh, I guess Ned's all right. Let him come along. We won't go very high to-morrow. After a trial rise by means of the gas, I'm going to lower the ship to the ground, and try for an elevation by means of the planes. Oh, yes, bring your friend along."
 
Ned Newton was delighted the next day to receive Tom's invitation, and, though a little dubious about trusting himself in an airship for the first time, finally consented to go with his chum. He got a half holiday from the bank, and, shortly after dinner went to Tom's house.
 
"Come on out in the shed and take a look at the Red Cloud," proposed the young inventor. "Mr. Sharp isn't quite ready to start yet, and I'll explain some things to you."
 
The big shed was deserted when the lads entered, and went to the loft where they were on a level with the big, red aluminum tank. Tom began with a description of the machinery, and Ned followed him with interest.
 
"Now we'll go down into the car or cabin," continued the young navigator of the air, "and I'll show you what we do when we're touring amid the clouds."
 
As they started to descend the flight of steps from the loft platform, a noise on the ground below attracted their attention.
 
"Guess that's Mr. Sharp coming," said Ned.
 
Tom leaned over and looked down. An instant later he grasped the arm of his chum, and motioned to him to keep silent.
 
"Take a look," whispered the young inventor.
 
"Andy Foger!" exclaimed Ned, peering over the railing.
 
"Yes, and Sam Snedecker and Pete Bailey are with him. They sneaked in when I left the door open. Wonder what they want?"
 
"Up to some mischief, I'll wager," commented Ned. "Hark! They're talking."
 
The two lads on the loft listened intently. Though the cronies on the ground below them did not speak loudly, their voices came plainly to the listeners.
 
"Let's poke a hole in their gas bag," proposed Sam. "That will make them think they're not so smart as they pretend."
 
"Naw, we can't do that," answered Andy.
 
"Why not?" declared Pete.
 
"Because the bag's away up in the top part of the shed, and I'm not going to climb up there."
 
"You're afraid," sneered Sam.
 
"I am not! I'll punch your face if you say that again! Besides the thing that holds the gas is made of aluminum, and we can't make a hole in it unless we take an axe, and that makes too much noise."
 
"We ought to play some sort of a trick on Tom Swift," proposed Pete. "He's too fresh!"
 
Tom shook his fist at the lads on the ground, but of course they did not see him.
 
"I have it!" came from Andy.
 
"What?" demanded his two cronies.
 
"We'll cut some of the guy wires from the planes and rudders. That will make the airship collapse. They'll think the wires broke from the strain. Take out your knives and saw away at the wires. Hurry, too, or they may catch us."
 
"You're caught now," whispered Ned to Tom. "Come on down, and give 'em a trouncing."
 
Tom hesitated. He looked quickly about the loft, and then a smile replaced the frown of righteous anger on his face.
 
"I have a better way," he said.
 
"What is it?"
 
"See that pile of dirt?" and he pointed to some refuse that had been swept up from the floor of the loft. Ned nodded. "It consists of a lot of shavings, sawdust and, what's more, a lot of soot and lampblack that we used in mixing some paint. We'll sweep the whole pile down on their heads, and make them wish they'd stayed away from this place."
 
"Good!" exclaimed Ned, chuckling. "Give me a broom. There's another one for you."
 
The two lads in the loft peered down. The red-headed, squint-eyed bully and his chums had their knives out, and were about to cut some of the important guy wires, when, at a signal from Tom, Ned, with a sweep of his broom, sent a big pile of the dirt, sawdust and lampblack down upon the heads of the conspirators. The young inventor did the same thing, and for an instant the lower part of the shed looked as if a dirtstorm had taken place there. The pile of refuse went straight down on the heads of the trio, and, as they were looking up, in order to see to cut the wires, they received considerable of it in their faces.
 
In an instant the white countenances of the lads were changed to black—as black as the burnt-cork performers in a minstrel show. Then came a series of howls.
 
"Wow! Who did that!"
 
"I'm blinded! The shed is falling down!"
 
"Run fellows, run!" screamed Andy. "There's been an explosion. We'll be killed!"
 
At that moment the big doors of the shed were thrown open, and Mr. Sharp came in. He started back in astonishment at the sight of the three grotesque figures, their faces black with the soot, and their clothes covered with sawdust and shavings, rushing wildly around.
 
"That will teach you to come meddling around here. Andy Foger!" cried Tom.
 
"I—I—you—you—Oh, wait—I—you—" spluttered the bully, almost speechless with rage. Sam and Pete were wildly trying to wipe the stuff from their faces, but only made matters worse. They were so startled that they did not know enough to run out of the opened doors.
 
"Wish we had some more stuff to put on 'em," remarked Ned, who was holding his sides that ached from laughter.
 
"I have it!" cried Tom, and he caught up a bucket of red paint, that had been used to give the airship its brilliant hue. Running to the end of the loft Tom stood for an instant over the trio of lads who were threatening and imploring by 'turns.
 
"Here's another souvenir of your visit," shouted the young inventor, as he dashed the bucket of red paint down on the conspirators. This completed the work of the dirt and soot, and a few seconds later, each face looking like a stage Indian's ready for the war-path, the trio dashed out. They shed shavings, sawdust and lampblack at every step, and from their clothes and hands and faces dripped the carmine paint.
 
"Better have your pictures taken!" cried Ned, peering from an upper window.
 
"Yes, and send us one," added Tom, joining his chum. Andy looked up at them. He dug a mass of red paint from his left ear, removed a mass of soot from his right cheek, and, shaking his fist, which was alternately striped red and black, cried out in a rage:
 
"I'll get even with you yet, Tom Swift!"
 
"You only got what was coming to you," retorted the young inventor. "The next time you come sneaking around this airship, trying to damage it, you'll get worse, and I'll have you arrested. You've had your lesson, and don't forget it."
 
The red-haired bully, doubly red-haired now, had nothing more to say. There was nothing he could say, and, accompanied by his companions, he made a bee-line for the rear gate in the fence, and darted across the meadow. They were all sorry enough looking specimens, but solely through their own fault.