"Look!" the young inventor cried. "No wonder it jammed!" and from a copper sleeve, through which ran the wire that worked the rudder, he pulled a small iron bolt. "That got between the sleeve and the wire, and I couldn't move it," he explained. "But when I pulled hard I loosened it."

"How did it fall in there?" asked Ned.

"It didn't FALL there." spoke Tom quietly. "It was PUT there."

"Put there! Bless my insurance policy! Who did such a dastardly trick?" cried Mr. Damon.

"I don't know," answered Tom still quietly, "but I suspect it was Andy Foger, and he was never any nearer to putting us out of business than a little while ago, Ned."

"Do you mean to say that he deliberately tried to injure you?" asked Mr. Damon.

"Well, he may not have intended to hurt us, but that's what would have happened if I hadn't been able to throw her up into the wind when I did," replied Tom. Then he told of Mr. Swift having seen the red-haired bully near the aeroplane. "Andy may have only intended to put my machine out of working order," went on the young inventor, "but it might have been worse than that," and he could not repress a shudder.

"Are you going to say anything to him?" asked Ned.

"I certainly am!" replied Torn quickly. "He doesn't realize that he might have crippled us both for life. I sure am going to say something to him when I get back."

But Tom did not get the chance, for when he and Ned returned to Shopton,--the sky racer behaving beautifully on the homeward trip,--it was learned that Mr. Foger had suddenly left town, taking Andy with him.

"Maybe he knew I'd be after him," said Tom grimly, and so that incident was closed for the time being, but it was a long time before Tom and Ned got over their fright.

They had a nice visit with Mr. Damon, and talked of the city of gold to their heart's content, looking at several large maps of Mexico that the eccentric man had procured, and locating, as well as they could from the meager map and description they had, where the underground treasures might be.

"I suppose you are getting ready to go, Mr. Damon?" remarked Ned.

"Hus.h.!.+" cautioned the odd man, looking quickly around the room. "I haven't said anything to my wife about it yet. You know she doesn't like me to go off on these 'wild goose chases' as she calls them, with you, Tom Swift. But bless my railroad ticket! It's half the fun of my life."

"Then don't you think you can go?" asked the young inventor eagerly, for he had formed a strong like for Mr. Damon, and would very much regret to go without him.

"Oh, bless my necktie! I think I'll be able to manage it," was the answer. "I'm not going to tell her anything about it until the last minute, and then I'll promise to bring her back one of the golden images. She won't object then."

"Good!" exclaimed Tom. "I hope we can all bring back some of the images."

"Yes, I know who you'll bring one for," said Ned with a laugh, and he took care to get beyond the reach of Tom's fist. "Her first name is Mary," he added.

"You get out!" laughed Tom, blus.h.i.+ng at the same time.

"Ah! What a thing it is to be young!" exclaimed Mr. Damon with a mock sigh. The boys laughed, for the old man, though well along in years, was a boy at heart.

They talked at some length, speculating when they might hear from Mr. Illingway, and discussing the sort of an outfit that would be best to take with them.

Then, as the afternoon was drawing to a close, Tom and Ned went back in the aeroplane, hearing the news about the Fogers as I have previously mentioned.

"Well, I'll have to wait until I do see Andy to take it out of his hide," remarked Tom grimly. "I'm glad he's out of the way, though.

There won't be any more danger of his overhearing our plans, and I can work in peace on the dirigible balloon."

Though Tom had many air crafts, the one he thought best suited to take with them on their search for the city of gold would have to be constructed from parts of several machines, and it would take some time.

Tom began work on it the next day, his father helping him, as did Mr. Damon and Ned occasionally. Several weeks were spent in this way, meanwhile the mails being anxiously watched for news from Africa.

"Here you are, Tom!" called the postman one morning, as he walked out to the shop where the young inventor was busy over the balloon.

"Here's another letter from that Buggy-wuggy place."

"Oh, you mean Gumba Twamba, in Africa!" laughed the lad. "Good!

That's what I've been waiting for. Now to see what the missionary says."

"I hope you're not going to go as a missionary to Africa, Tom," said the postman.

"No danger. This is just a letter from a friend there. He sent me some facts so I can go off on another expedition."

"Oh, you're always going off on wild adventures," commented Uncle Sam's messenger with a shake of his head as he hurried away, while Tom tore open the letter from Africa and eagerly read it.

CHAPTER VI

"BEWARE THE HEAD-HUNTERS!"

"That's what I want!" exclaimed the young inventor, as he finished the perusal of the missionary's missive.

"What is it?" asked Mr. Swift, entering the shop at that moment.

"News from Africa, dad. Mr. Illingway went to a lot of trouble to get more information for us about the city of gold, and he sends a better map. It seems there was one among the effects of the white man who died near where Mr. Illingway has his mission. With this map, and what additional information I have, we ought to locate the underground city. Look, dad," and the lad showed the map.

"Humph!" exclaimed Mr. Swift with a smile. "I don't call that a very clear map. It shows a part of Central Mexico, that's true, but it's on such a small scale I don't see how you're going to tell anything by it."

"But I have a description," explained Tom. "It seems according to Mr. Illingway's letter, that you have to go to the coast and strike into the interior until you are near the old city of Poltec. That used to be it's name, but Mr. Illingway says it may be abandoned now, or the name changed. But I guess we can find it."

"Then, according to what he could learn from the African natives, who talked with the white man, the best way is to hire ox carts and strike into the jungle. That's the only way to carry our baggage, and the dirigible balloon which I'm going to take along."

"Pretty uncertain way to look for a buried city of gold," commented Mr. Swift. "But I suppose even if you don't find it you'll have the fun of searching for it, Tom."

"But we ARE going to find it!" the lad declared. "We'll get there, you'll see!"

"But how are you going to know it when you see it?" asked his father. "If it's underground even a balloon won't help you much."

"It's true it is underground," agreed Tom, "but there must be an entrance to it somewhere, and I'm going to hunt for that entrance.

Mr. Illingway writes that the city is a very old one, and was built underground by the priests of some people allied to the Aztecs. They wanted a refuge in times of war and they also hid their valuables there. They must have been rich to have so much gold, or else they didn't value it as we do."

"That might be so," a.s.sented Mr. Swift. "But I still maintain, Tom, that it's like looking for a needle in a haystack."

"Still, I'm going to have a try for it," a.s.serted the lad. "If I can once locate the plain of the big temple I'll be near the entrance to the underground city."

"What is the 'plain of the big temple,' Tom?"

"Mr. Illingway writes," said the lad, again referring to the letter, "that somewhere near the beginning of the tunnel that leads into the city of gold, there is an immense flat plain, on which the ancient Aztecs once built a great temple. Maybe they wors.h.i.+ped the golden images there. Anyhow the temple is in ruins now, near an overgrown jungle, according to the stories the white man used to tell. He once got as near the city of gold as the big temple, but hostile natives drove him and his party back. Then he went to Africa after getting an image from someone, and died there. So no one since has ever found the city of gold."