"Letter for you, Tom Swift."

"Ah, thanks, Mr. Wilson. This is the first mail I've had this week. You've been neglecting me," and the young inventor took the missive which the Shopton postman handed to him over the gate, against which Tom was leaning one fine, warm Spring day.

"Well, I get around as often as I can, Tom. You're not home a great deal, you know. When you're not off in your sky racer seeing how much you can beat the birds, you're either hunting elephants in Africa, or diving down under the ocean, or out in a diamond mine, or some such out-of-the-way place as that. No wonder you don't get many letters. But that one looks as if it had come quite a distance."

"So it does," agreed Tom, looking closely at the stamp and postmark. "What do you make out of it, Mr. Wilson?" and then, just as many other persons do when getting a strange letter, instead of opening it to see from whom it has come, Tom tried to guess by looking at the handwriting, and trying to decipher the faint postmark. "What does that say?" and the young inventor pointed to the black stamp.

"Hum, looks like Jube--no, that first letter's a 'K' I guess," and Mr. Wilson turned it upside down, thinking that would help.

"I made it out a 'G'," said Tom.

"So it is. A 'G'--you're right. Gumbo--Twamba--that's what it is-- Gumba Twamba. I can make it out now all right."

"Well, where, for the love of my old geography, is Gumba Twamba?" asked the lad with a laugh.

"You've got me, Tom. Must be in Sweden, or Holland, or some of those foreign countries. I don't often handle letters from there, so I can't say. Why don't you open your letter and find out who its from?"

"That's what I ought to have done at first." Quickly Tom ripped open the much worn and frayed envelope, through the cracks of which some parts of the letter already could be seen, showing that it had traveled many thousand miles before it got to the village of Shopton, in New York State.

"Well, I've got to be traveling on," remarked the postman, as Tom started to read the mysterious letter. "I'm late as it is. You can tell me the news when I pass again, Tom."

But the young inventor did not reply. He was too much engaged in reading the missive, for, no sooner had he perused the first few lines than his eyes began to open wide in wonder, and his manner plainly indicated his surprise. He read the letter once, and then over again, and when he had finished it a second time, he made a dash for the house.

"I say dad!" cried Tom. "This is great! Great news here! Where are you, dad? Say, Mrs. Baggert," he called as he saw the motherly housekeeper, "where's father? I've got great news for him? Where is he?"

"Out in the shop, I think. I believe Mr. Damon is with him."

"And blessing everything as usual, from his hat to his shoe laces, I'll wager," murmured Tom as he made his war to the shop where his father, also an inventor like himself, spent much of his time. "Well, well, I'm glad Mr. Damon is here, for he'll be interested in this."

Tom fairly rushed into the building, much of the space of which, was taken up by machinery, queer tools and odd devices, many of them having to do with the manufacture of aeroplanes, for Tom had as many of them as some people have of automobiles.

"I say, dad!" cried Tom, waving the letter above his head, "what do you think of this? Listen to--"

"Easy there now, Tom! Easy, my boy, or you'll oblige me to do all my work over again," and an aged man, beside whom a younger one was standing, held up a hand of caution, while with the other hand he was adjusting some delicate piece of machinery.

"What are you doing?" demanded the son.

"Bless my scarf pin!" exclaimed the other man--Mr. Wakefield Damon-- "Bless my rubbers, Tom Swift! What should your father be doing but inventing something new, as he always is. I guess he's working on his new gyroscope, though it is only a guess, for he hasn't said ten words to me since I came out to talk to him. But that's like all inventors, they--"

"I beg your pardon, Mr. Damon," spoke Mr. Swift with a smile, "I'm sure--"

"Say, can't you listen to me for five minutes?" pleaded Tom. "I've got some great news--simply great, and your gyroscope can wait, dad. Listen to this letter," and he prepared to read it.

"Who's it from?" asked Mr. Damon.

"Mr. Jacob Illingway, the African missionary whom you and I rescued, together with his wife, from the red pigmies!" cried Tom. "Think of that! Of all persons to get a letter from, and such a letter! Such news in it. Why, it's simply great! You remember Mr. and Mrs. Illingway; don't you Mr. Damon? How we went to Africa after elephant's tusks, with Mr. Durban the hunter, and how we got the missionaries away from those little savages in my airship--don't you remember?"

"I should say I did!" exclaimed Mr. Damon. "Bless my watch chain-- but they were regular imps--the red Pygmies I mean, not the missionaries. But what is Mr. Illingway writing to you about now, Tom? I know he sent you several letters since we came back from Africa. What's the latest news?"

"I'll tell you," replied the young inventor, sitting down on a packing box. "It would take too long to read the letter so I'll sum it up, and you can go over it later."

"To be brief, Mr. Illingway tells of a wonderful golden image that is worshiped by a tribe of Africans in a settlement not far from Gumba Twamba, where he is stationed. It's an image of solid gold--"

"Solid gold!" interrupted Mr. Swift.

"Yes, dad, and about three feet high," went on Tom, referring to the letter to make sure. "It's heavy, too, no hollows in it, and these Africans regard it as a god. But that's not the strangest part of it. Mr. Illingway goes on to say that there is no gold in that part of Africa, and for a time he was at a loss how to account for the golden image. He made some inquiries and learned that it was once the property of a white traveler who made his home with the tribe that now worships the image of gold. This traveler, whose name Mr. Illingway could not find out, was much liked by the Africans. He taught them many things, doctored them when they were sick, and they finally adopted him into the tribe."

"It seems that he tried to make them better, and wanted them to become Christians, but they clung to their own beliefs until he died. Then, probably thinking to do his memory honor, they took the golden image, which was among his possessions, and set it up as a god."

"Bless my hymn book!" exclaimed Mr. Damon. "What did they do that for?"

"This white man thought a great deal of the image," said Tom, again referring to the letter, "and the Africans very likely imagined that, as he was so good to them, some of his virtues had passed into the gold. Then, too, they may have thought it was part of his religion, and as he had so often wanted them to adopt his beliefs, they reasoned out that they could now do so, by worshiping the golden god."

"Anyhow, that's what they did, and the image is there to-day, in that far-off African village. But I haven't got to the real news yet. The image of solid gold is only a part of it."

"Before this traveler died he told some of the more intelligent natives that the image had come from a far-off underground city--a regular city of gold--nearly everything in it that was capable of being made of metal, being constructed of the precious yellow gold. The golden image was only one of a lot more like it, some smaller and some larger--"

"Not larger, Tom, not larger, surely!" interrupted Mr. Swift. "Why, my boy, think of it! An image of solid gold, bigger even than this one Mr. Illingway writes of, which he says is three feet high. Why, if there are any larger they must be nearly life size, and think of a solid gold statue as large as a man--it would weigh--well, I'm afraid, to say how much, and be worth--why, Tom, it's impossible. It would be worth millions--all the wealth of a world must be in the underground city. It's impossible Tom, my boy!"

"Well, that may be," agreed Tom. "I'm not saying it's true. Mr. Illingway is telling only what he heard."

"Go on! Tell some more," begged Mr. Damon. "Bless my shirt studs, this is getting exciting!"

"He says that the traveler told of this underground city of gold," went on Tom, "though he had never been there himself. He had met a native who had located it, and who had brought out some of the gold, including several of the images, and one he gave to the white man in return for some favor. The white man took it to Africa with him."

"But where is this underground city, Tom?" asked Mr. Swift. "Doesn't Mr. Illingway give you any idea of its location."

"He says it is somewhere in Mexico," explained the lad. "The Africans haven't a very good idea of geography, but some of the tribesmen whom the white traveler taught, could draw rude maps, and Mr. Illingway had a native sketch one for him, showing as nearly as possible where the city of gold is located."

"Tom Swift, have you got that map?" suddenly cried Mr. Damon. "Bless my pocketbook, but--"

"I have it!" said Tom quietly, taking from the envelope a piece of paper covered with rough marks. "It isn't very good, but--"

"Bless my very existence!" cried the excitable man. "But you're not going to let such a chance as this slip past; are you Tom? Are you going to hunt for that buried city of gold?"

"I certainly am," answered the young inventor quietly.

"Tom! You're not going off on another wild expedition?" asked Mr. Swift anxiously.

"I'm afraid I'll have to," answered his son with a smile.

"Go? Of course he'll go!" burst out Mr. Damon. "And I'm going with him; can't I, Tom?"

"Surely. The reason Mr. Illingway sent me the letter was to tell me about the city of gold. He thought, after my travels in Africa, that to find a buried city in Mexico would be no trouble at all, I suppose. Anyhow he suggests that I make the attempt, and--"

"Oh, but, Tom, just when I am perfecting my gyroscope!" exclaimed Mr. Swift. "I need your help."

"I'll help you when I come back, dad. I want to get some of this gold."

"But we are rich enough, Tom."

"It isn't so much the money, dad. Listen. There is another part to the letter. Mr. Illingway says that in that underground city, according to the rumor among the African natives, there is not only gold in plenty, and a number of small gold statues, but one immense big one--of solid gold, as large as three men, and there is some queer mystery about it, so that white traveler said. A mystery he wanted to solve but could not."

"So, dad, I'm going to search for that underground city, not only for the mere gold, but to see if I can solve the mystery of the big gold statue. And if I could bring it away," cried Tom in great excitement as he waved the missionary's letter above his head, "it would be one of the wonders of the world--dad, for, not only is it very valuable, but it is most beautifully carved."

"Well, I might as well give up my gyroscope work until you come back from the city of gold, Tom, I can see that," said Mr. Swift, with a faint smile. "And if you go, I hope you come back. I don't want that mysterious image to be the undoing of you."

"Oh, I'll come back all right!" cried Tom confidently. "Ho! for the city of gold and the images thereof! I'm going to get ready to start!"

"And so am I!" cried Mr. Damon. "Bless my shoe strings, Tom, but I'm with you! I certainly am!" and the little man excitedly shook hands with Tom Swift, while the aged inventor looked on and nodded his head doubtfully. But Tom was full of hope.