"Well, I hope you do, Tom, but I doubt it. However, I suppose you will hurry your preparations for going away, now that you have all the information you can get."

"Right, dad. I must send word to Mr. Damon and Ned at once. A few more days' work, and my balloon will be in shape for a trial flight, and then I can take it apart, pack it up, and s.h.i.+p it. Then ho! for the city of gold!"

Mr. Swift smiled at his son's enthusiasm, but he did not check it.

He knew Tom too well for that.

Naturally Mr. Damon and Ned were delighted with the additional information the missionary had sent, and Ned agreed with Tom that it was a mere matter of diligent search to find the underground city.

"Bless my collar b.u.t.ton!" cried Mr. Damon. "It may not be as easy as all that, but Tom Swift isn't the kind that gives up! We'll get there!"

Meanwhile Tom worked diligently on his balloon. He sent a letter of thanks to Mr. Illingway, at the same time requesting that if any more information was obtained within the next three weeks to cable it, as there would not be time for a letter to reach Shopton ere Tom planned to leave for Mexico.

The following days were busy ones for all. There was much to be done, and Tom worked night and day. They had to get rifles ready, for they might meet hostile natives. Then, too, they had to arrange for the proper clothing, and other supplies.

To take apart and s.h.i.+p the balloon was no small task, and then there were the pa.s.sages to engage on a steamer that would land them at the nearest point to strike into the interior, the question of transportation after reaching Mexico, and many other matters to consider.

But gradually things began to shape themselves and it looked as though the expedition could start for the city of gold in about two weeks after the receipt of the second letter from the missionary.

"I think I'll give the balloon a trial to-morrow," said Tom one night, after a hard day's work, "It's all ready, and it ought to work pretty good. It will be just what we need to sail over some dense jungle and land down on the plain by the great temple."

"Bless my slippers!" exclaimed Mr. Damon. "I must think up some way of telling my wife that I'm going."

"Haven't you told her yet?" asked Ned.

The eccentric man shook his head.

"I haven't had a good chance," he said, "but I think I'll tell her to-morrow, and promise her one of the gold images. Then she won't mind."

Tom was just a little bit nervous when he got ready for a trial flight in the new dirigible balloon. To tell the truth he much preferred aeroplanes to balloons, but he realized that in a country where the jungle growth prevailed, and where there might be no level places to get a "take off," or a starting place for an aeroplane, the balloon was more feasible.

But he need have had no fears, for the balloon worked perfectly. In the bag Tom used a new gas, much more powerful even than hydrogen, and which he could make from chemicals that could easily be carried on their trip.

The air craft was small but powerful, and could easily carry Tom, Ned and Mr. Damon, together with a quant.i.ty of food and other supplies. They intended to use it by starting from the place where they would leave the most of their baggage, after getting as near to the city of gold as they could by foot trails. Tom hoped to establish a camp in the interior of Mexico, and make trips off in different directions to search for the ruined temple. If unsuccessful they could sail back each night, and if he should discover the entrance to the buried city there was food enough in the car of the balloon to enable them to stay away from camp for a week or more.

In order to give the balloon a good test, Tom took up with him not only Ned and Mr. Damon, but Eradicate and Mr. Swift to equalize the weight of food and supplies that later would be carried. The test showed that the craft more than came up to expectations, though the trial trip was a little marred by the nervousness of the colored man.

"I doan't jest laik dis yeah kind of travelin'," said Eradicate.

"I'd radder be on de ground."

Most of the remaining two weeks were spent in packing the balloon for s.h.i.+pment, and then the travelers got their own personal equipment ready. They put up some condensed food, but they depended on getting the major portion in Mexico.

It was two days before they were to start. Their pa.s.sage had been engaged on a steamer, and the balloon and most of their effects had been s.h.i.+pped. Mr. Damon had broken the news to his wife, and she had consented to allow him to go, though she said it would be for the last time.

"But if I bring her back a nice, big, gold image I know she'll let me go on other trips with you, Tom." said the eccentric man. "Bless my yard stick, if I couldn't go off on an adventure now and then I don't know what I'd do."

They were in the library of the Swift home that evening. Tom, Ned, Mr. Damon and the aged inventor, and of course the only thing talked of was the prospective trip to the city of gold.

"What I can't understand," Mr. Swift was saying, "is why the natives made so many of the same images of gold, and why there is that large one in the underground place. What did they want of it?"

"That's part of the mystery we hope to solve," said Tom. "I'm going to bring that big image home with me if I can. I guess--"

He was interrupted by a ring at the front door.

"I hope that isn't Andy Foger," remarked Ned.

"No danger," replied Tom. "He'll keep away from here after what he did to my aeroplane."

Mrs. Baggert went to the door.

"A message for you, Tom," she announced a little later, handing in an envelope.

"h.e.l.lo, a cablegram!" exclaimed the young inventor. "It must be from Mr. Illingway, in Africa. It is," he added a moment later as he glanced at the signature.

"What does he say?" asked Mr. Swift.

"Can he give us any more definite information about the city of gold?" inquired Ned.

"I'll read it," said Tom, and there was a curious, strained note in his voice. "This is what it says:"

"'No more information obtainable. But if you go to the city of gold beware of the head-hunters!'"

"Head-hunters!" exclaimed Mr. Damon. "Bless my top-knot, what are they?"

"I don't know," answered Tom simply, "but whatever they are we've got to be on the lookout for them when we get to the gold city, and that's where I'm going, head-hunters or no head-hunters!"

CHAPTER VII

TOM MAKES A PROMISE

It may well be imagined that the cable warning sent by Mr. Illingway caused our friends considerable anxiety. Coming as it did, almost at the last minute, so brief--giving no particulars--it was very ominous. Yet Tom was not afraid, nor did any of the others show signs of fear.

"Bless my shotgun!" exclaimed Mr. Damon, as he looked at the few words on the paper which Tom pa.s.sed around. "I wish Mr. Illingway had said more about the head-hunters--or less."

"What do you mean?" asked Ned.

"Well, I wish he'd given us more particulars, told us where we might be on the lookout for the head-hunters, what sort of chaps they were, and what they do to a fellow when they catch him."

"Their name seems plainly to indicate what they do," spoke Mr. Swift grimly. "They cut off the head of their enemies, like that interesting Filipino tribe. But perhaps they may not get after you.

If they do--"

"If they do," interrupted Tom with a laugh, "we'll hop in our dirigible balloon, and get above THEIR heads, and then I guess we can give a good account of ourselves. But would you rather Mr.

Illingway had said less about them, Mr. Damon?"

"Yes, I wish, as long as he couldn't tell us more, that he'd kept quiet about them altogether. It's no fun to be always on the lookout for danger. I'm afraid it will get on my nerves, to be continually looking behind a rock, or a tree, for a head-hunter. Bless my comb and brus.h.!.+"