The boys gazed at the twelve men who stood facing them with leveled rifles and could not help but acknowledge the truth of these words. It seemed that they were utterly in the power of the j.a.panese.

"Your government shall hear about this," sputtered the professor angrily. "It will not countenance such a high-handed proceeding. We are not at war with your country. You have no right under the law of nations, or any other law, to interfere with us."

"You will oblige me by stepping into the cabin of my dirigible," was the response in an even tone. The others had paid not the slightest attention to the professor's harangue.

"And if we refuse?" demanded the professor.

"If you refuse you will be shot, and do not, I beg, make the mistake of thinking that I don't mean what I say."

There was nothing to do, under the circ.u.mstances, but to obey and, with sinking hearts, they advanced in the direction of the big air-ship. With great courtesy the interloper ushered them inside.

They found a warm and comfortable interior, well cushioned and even luxurious in its appointments. Once they were well inside the little man, with a bow, remarked:

"I now beg to be excused. You will find books and the professor something to smoke if he wishes it. Don't make any attempt to escape as I should regret to be compelled to have any of you shot."

He was gone. Closing the door behind him with a "click," that told the boys that they were locked in.

"Prisoners," exclaimed Billy.

"That's it, and just as we have accomplished our wish," said Frank bitterly; "it's too bad."

"Well, it can't be helped," said the professor, "let's look about and see if there is not some way we can get out if an opportunity presents itself."

They approached a window and through it could see the new arrivals examining the edge of the gulf and peeping down at the Viking ship.

But as soon as they opened the cas.e.m.e.nt and peered out a man with a rifle appeared, as if from out of the earth, and sharply told them to get inside.

"Well, we've got to spend the time somehow, we might as well examine the ship," said the professor closing the window.

Somewhat cheered by his philosophical manner, the boys followed him as he led the way from the main cabin through a steel door which they found led into the engine-room. The engines were cut off, but a small motor was operating a dynamo with a familiar buzzing sound. This was the sound the boys had heard when the ship pa.s.sed above them at night.

"What have they got the dynamo going for?" demanded Harry.

"I don't know. To warm the ship by electric current, or something I suppose," said Frank listlessly. "I wonder where the engineer is? The ship seems deserted."

"I guess he's out with the rest looking over OUR treasure," said the professor bitterly.

"Ours no longer,--might is right, you know," quoted Harry miserably.

Frank had been examining the machinery with some care. Even as a prisoner he felt some interest in the completeness of the engine room of the j.a.panese dirigible. He bent over her twin fifty-horse-power motors with admiring appreciation and examined the other machinery with intense interest.

The purring dynamo next came in for his attention and he was puzzling over the utility of several wires that led from it through the engine room roof when a sudden thought flashed into his mind. With a cry of triumph he bent over a small lever marked "accelerator," beside which was a small gauge. He rapidly adjusted the gauge, so that it would not register any more than the pressure it recorded at that moment and then shoved the lever over to its furthest extent.

"Whatever are you doing?" demanded Harry, much mystified at these actions, at the conclusion of which he had strolled up.

"You know that the gas in the bag of this dirigible is heated by electric radiators in order to avoid condensation of the gas?" was the seemingly incoherent reply.

"Yes," was the astonished answer, "but what has that--?"

"Hold on a minute," cried Frank, raising his hand, "and that gas when expanded by heat soon becomes too buoyant for its container, and will, if allowed to continue expanding, burst its confines."

Harry nodded his head.

"Well, then," Frank went on, "that's what's going to happen on this ship."

"Whatever do you mean? I suppose I'm dense, but I don't see yet."

"I mean," said Frank, "that I've fixed the gas-heating radiators so that in a few hours the bag above our head will be ripped into tatters by a gas explosion. The resistance coils are now heating and expanding the gas at a rate of ten times above the normal and the gauge I have adjusted so that an inspection of it will show nothing to be the matter."

"But what good will that do us?" urged Harry.

"It may save our lives. In any event the Viking treasure will never be taken from here by another nation."

CHAPTER XXVII.

THE FATE OF THE DIRIGIBLE.

"Have you any idea what time the explosion will take place?" asked Harry, anxiously, almost dumbfounded by the other's cool manner.

"Soon after dark has fallen. Don't be scared, it won't hurt us; at least I think not, but in the confusion that is certain to follow we must make a dash for the Golden Eagle."

"It's a desperate chance."

"We are in a desperate fix," was the brief reply.

An hour later something occurred which caused Frank, who had in the meantime communicated his plan to the others, considerable anxiety.

The despoilers of the adventurers' treasure h.o.a.rd returned to the ship laden down with bar gold and ivory and, from what the captain was saying to his minor officers, it seemed, though he spoke in a low tone, that it was planned to sail right off back to the camp of the men the boys had now come justifiably to regard as their enemies.

"If they do that, we are lost," said Frank, after he had whispered his fears to Harry.

"You mean they will discover the trick we have played on them?"

"No, I mean that the explosion will come off in midair and we shall all be dashed to death together."

"Phew!--Would it not be better to tell them what we have done and take our chances?"

"If the worst comes to the worst I shall do that. It would be imperiling our lives uselessly to go aloft with the overheated gas that is now in the bag."

But the "worst did not come to the worst." The little captain who had paid small or no attention to his prisoners, evidently realizing that they could not get away, didn't like the look of the weather, it seemed, and made frequent consultations of the barometer with his fellows. The gla.s.s was falling fast and there was evidently a blizzard or sharp storm of some kind approaching.

At this time a fresh fear crossed Frank's mind. What if the j.a.ps had destroyed the Golden Eagle? So far as he could judge they had not molested her, evidently not thinking it worth while to waste time they judged better spent on looting the Viking ship of its treasure. But if they had disabled her, the boy knew that in the event of his companions escaping they faced an alternative between death by freezing and starvation, or being shot down by the rifles of their captors. However, Frank resolved to put such gloomy speculations out of his mind. It was useless to worry. Things, if they were as he half feared, would not mend for thinking about them.

Supper, a well-cooked, well-served meal, was eaten under this painful strain. The boys and the professor put the best countenance they could on things, considering that their minds were riveted on the great gasbag above them which even now, as they knew, was swollen almost to bursting point with its superheated gases.

"It is too bad that the weather threatens so," remarked their captor, who was politeness itself, to his prisoners; "otherwise we should now be in the air on our way back to my camp. In three more trips we shall be able, however, to carry off the rest of the treasure. We were well repaid for keeping our eyes on you."