"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 Japanese 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 hoard 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 glass 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 Japs 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."

The boys answered something, they hardly knew what. Frank in his nervousness looked at his watch. The strain was becoming painful. At last, to their intense relief, they rose from supper and the little officer shut himself in his own cabin. Outside, the boys could hear the feet of the two armed sentries crunching on the snow.

"The outrush of gas will stupefy them," whispered Frank, "we shall have nothing to fear from them after the explosion takes place."

"When is it due?" gasped Billy, with a ghastly attempt at a smile.

"At any moment now. It is impossible to calculate the exact time. But within half an hour we should know our fate."

Silently the boys and the professor waited, although the scientist was so nervous that he strode up and down the cabin floor.

Suddenly the silence was shattered by a loud shout from the engine room.

"The gas! The gas! We are—"

The sentence was never finished.

There was a sudden convulsion of the entire fabric of the big dirigible—as if a giant hand from without were shaking her like a puppy shakes a rat.

She seemed to lift from the ground in a convulsive leap and settled back with a crash that smashed every pane of glass and split her stout sides.

At the same instant, there was an ear-splitting roar as if a boiler had exploded and a flash of ruddy flame.

The exploding gas had caught fire—possibly from a spark from the electric radiators as the bag and their supporting framework was ripped apart by the explosion.

Dazed and half stunned, the boys groped about in total darkness; for the explosion had extinguished every light on the ship.

"Boys, where are you?"

It was Frank calling.

"Great heavens, what a sensation!" gasped the professor, half choked by the powerful fumes of the hydrogen gas which filled the air.

Rapidly the others answered to Frank and groped through the darkness toward his voice. Before them was the shattered side of the cabin. Through the gap was the sky. They could see the bright antarctic stars gleaming. Beyond the rent they knew lay freedom, provided the marauders had not molested their aeroplane.

It was the work of a second to stagger through the opening made by the explosion and gain the fresh air, which they inhaled in great mouthfuls. Then began the dash for the aeroplane.

In the wild confusion that reigned following the explosion, their absence, so far as they could perceive, had not been noticed. As Frank had guessed, the two sentries were knocked senseless by the explosion and the fugitives stumbled over their unconscious figures recumbent on the snow.

Gasping and staggering they plunged on in the direction they knew the Golden Eagle lay. It was not more than a mile distant, but before they reached their goal the professor gave out and the boys had to half-drag, half-carry him over the frozen surface. They were bitterly cold, too, and the thought of the blankets and warm clothing aboard the Golden Eagle lent them additional strength—as much so, in fact, as the peril that lay behind them.

"Can you see her?" gasped Harry, after about fifteen minutes of this heart-breaking work.

"Yes. I think so at least. There seems to be a dark object on the snow ahead. If only they have not molested her," panted Frank.

"If they have, it's all up," exclaimed Billy Barnes. At the same moment Harry breathed:

"Hark!"

Borne over the frozen ground they could hear shouts.

"They have discovered our escape!" exclaimed Frank, "it's a race for life now."



His words threw fresh determination into all. Even the professor made a desperate struggle. A few more paces and there was no doubt that the dark object ahead was the Golden Eagle. Only one anxiety now remained. Was she unharmed?

Bang!

It was a shot from the men of the dirigible.

"They are firing after us," exclaimed Billy.

"They can fire all they want to if they come as wide of the mark as that," said Frank; "they are shooting at random to scare us."

A few seconds later they gained the side of the Golden Eagle and, worn and harried as they were, they could not forbear setting up a cheer as they found that the aeroplane was in perfect shape.

Hastily they cranked the Golden Eagle motor up, blue flame and sharp reports bursting from her exhausts as they did so. The engine was working perfectly,—every cylinder taking up its work as the sparks began to occur rhythmically.

"We've put the fat in the fire now," exclaimed Frank, as he took his seat at the steering wheel. "If they could not locate us before, the noise of the exhaust and the blue flame will betray us to them."

"Well, it can't be helped," shouted Harry, above the roar of the engine. "We've got to get every ounce of power out of her to-night."

The other lad nodded and as he did so a sound like a bee in flight fell on the adventurers' ears—a bullet.

It was followed by several reports.

"They've got the range," cried Harry.

"They won't have it long," said his brother as he threw in the clutch and rapidly the Golden Eagle sped forward, crashing faster and faster over the frozen surface as her young driver worked the engine up to full speed.

In a few seconds more they felt the aeroplane begin to lift and soar into the night air.

They were exploding skyward to safety, while far below them their baffled captors were firing aimlessly in the hope of a random shot shattering some vital part of the aeroplane.

But no such thing happened and as the boys sped toward the west, bound for Camp Hazzard, they sent out a wireless message. Again and again they tried but without success. They could not raise an answer.

"Of course we can't raise them. They are on the march!" shouted Frank suddenly.

"On the motor-sledge bound for the Viking ship," cried Billy, "they should be there to-morrow."

"Say, fellows, we have done it now," cried Frank, with a sudden twinge.

"What's the matter?" inquired the professor.

"Why, they will arrive there to find the others in possession and no sign of us. They'll think we ran away without even putting up a fight."

"We'll have to try to pick them up in the daylight," was the reply; "we know about the route along which they'll drive and from this altitude we can't miss them if they are anywhere within miles of us."

The boys were then at a height of about 1,500 feet. The air was bitter chill and warm wraps and furs had been donned long before. Suddenly the aeroplane gave a sickening sidewise dip and seemed about to capsize. Frank caught and righted her just in time. The gyroscopic balance whizzed furiously.

A curious moaning sound became perceptible in the rigging and a wind, which they had not noticed before, lashed their faces with a stinging sensation. The recollection of the falling barometer flashed across Frank's mind. They were in for a storm.

The boy gazed at the compass beneath its binnacle light. As he did so he gave a gasp.

"We are way off our course," he cried, "the wind is out of the north and it is blowing us due south."

"Due south!" exclaimed Harry.

"That's it. And the worst of it is I can do nothing. With this load on board I don't dare try to buck the wind and it's freshening every minute."

"But if we are being blown due south from here, where on earth will we fetch up?" cried Billy, in dismayed tones.

They all looked blank as they awaited the reply. Frank glanced at his watch and then at the compass and made a rapid mental calculation.

"At the rate we are going we should be over the South Pole, roughly speaking, at about midnight," he said.



CHAPTER XXVIII.

THE HEART OF THE ANTARCTIC.

The professor was the first to break the tense silence that followed Frank's words.

"Into the heart of the Antarctic," he breathed.

There seemed to be something in the words that threw a spell of awed silence over them all. Little was said as on and on through the polar night the aeroplane drove,—the great wind of the roof of the world harassing her savagely, viciously,—as if it resented her intrusion into the long hidden arcana of the polar Plateau.

It grew so bitter cold that the chill ate even through their furs and air-proofed clothing. The canvas curtains were hoisted for a short distance to keep off the freezing gale. They dared not set them fully for fear they might act as sails and drive the ship before the gale so fast that all control would be lost.

At ten o'clock Frank, his hands frozen almost rigid, surrendered the wheel to Harry.

It now began to snow. Not a heavy snowfall but a sort of frozen flurry more like hail in its texture. Frank glanced at his watch.

Eleven o'clock.

"How's she headed?" shouted Harry, above the song of the polar gale.

"Due south," was the short reply as the other boy bent over the compass.

"Well, wherever we are going, we are bound for the pole, there's some grim satisfaction in that," remarked Frank.

On and on through the cold they drove. The snow had stopped now and suddenly Billy called attention to a strange phenomenon in the southern sky.

It became lit with prismatic colors like a huge curtain, gorgeously illuminated in its ample folds by the rays of myriad colored searchlights.

"Whatever is it?" gasped Billy in an awed tone as the mystic lights glowed and danced in almost blinding radiance and cast strange colored lights about the laboring aeroplane.

"The Aurora Australis," said the professor in an almost equally subdued voice, "the most beautiful of all the polar sky displays."

"The Aurora Australis," cried Frank, "then we are near the pole indeed."

Half past eleven.

The lights in the sky began to dim and soon the aeroplane was driving on through solid blackness. The suspense was cruel. Not one of the adventurers had any idea of the conditions they were going to meet. A nameless dread oppressed all.

Suddenly Frank, after a prolonged scrutiny of the compass, voiced what was becoming a general fear.

"What if we are being drawn by magnetic force toward the pole?"

"And be dashed to destruction as we reach it?" the professor finished for him.

Brave as they were, the adventurers gave a shudder that was not born of the gnawing cold as the possibility occurred to them. Frank glanced at the barograph. Fifteen hundred feet. They were then holding their own in altitude. This was a cheering sign.

Ten minutes to twelve.

The strange lights began to reappear. Glowing in fantastic forms they seemed alive with lambent fire. As the boys gazed at each other they could see that their features were tinted with the weird fires of the polar sky.

Twelve o'clock.

Frank gave a hurried dash toward the compass and drew back with a shout.

"Look," he shouted, "we are within the polar influence."

The needle of the instrument was spinning round and round at an almost perpendicular angle in the binnacle with tremendous velocity. The pointer tore round its points like the hands of a crazy clock.

"What does it mean?" quavered Harry.

"The South Pole, or as near to it as we are ever likely to get," exclaimed Frank, peering over the side.

Far below illuminated fantastically by the lights of the dancing, flickering aurora he could see a vast level plain of snow stretching, so it seemed, to infinity. There was no open sea. No strange land. Nothing but a vast plateau of silent snow.

"Fire your revolvers, boys," shouted Frank, as, suiting the action to the word, he drew from his holster his magazine weapon and saluted the silent skies.

"The South Pole—Hurrah!"

It was a quavering cry, but the first human sound that had ever broken the peace of the mysterious solitudes above which they were winging.

Suddenly in the midst of the "celebration" the aeroplane was violently twisted about. Every bolt and stay in her creaked and strained under the stress, but so well and truly had she been built that nothing started despite Frank's fears that the voyage to the pole was to end right there in disaster.

The adventurers were thrown about violently. All, that is, but Frank, who had now resumed the wheel and steadied himself with it. As they scrambled to their feet Billy chattered:

"Whatever happened—did a cyclone strike us?"

For answer Frank bent over the compass and gave a puzzled cry.

"I don't understand this," he exclaimed.

"Don't understand what?" asked Harry, coming to his side.

"Why look here—what do you make of that?"

"The needle has steadied and is pointing north!" cried Harry, as he gazed at the compass.

"North," echoed the professor.

"There's no question about it," rejoined Frank, knitting his brows.

"What is your explanation of this sudden reversal of the wind?" asked the professor.

"I know no more than you," replied the puzzled young aviator, "the only reason I can advance is that at the polar cap some strange influences rule the wind currents and that we are caught in a polar eddy, as it were."

"If it holds we are saved," cried the professor, who had begun to fear that they might never be able to emerge from their newly discovered region.

Hold it did and daybreak found the aeroplane above the same illimitable expanse of snow that marked the pole, but several miles to the north.

"I'm going down to take an observation," said Frank, suddenly, "and also, has it occurred to you fellows that we haven't eaten a bite since last night?"

"Jiminy crickets," exclaimed Billy Barnes, his natural flow of spirits now restored, "that's so. I'm hungry enough to eat even a fur-bearing pollywog, if there's one around here."

"Boys," began the professor solemnly as Billy concluded, "I have a confession to make."

"A confession?" cried Harry, "what about?"

"Why for some time I have entertained a doubt in my mind and that doubt has now crystallized to a certainty. I don't believe there is such a creature as the fur-bearing pollywog."

"Then Professor Tapper is wrong?" asked Harry, amazed at the scientist's tone.

"I am convinced he is. I shall expose him when we return—if we ever do," declared the scientist.

A few minutes later they landed on the firm snow and soon a hearty meal of hot canned mutton, vegetables, soup, and even a can of plum pudding, warmed on their stove and washed down with boiling tea, was being disposed of.

"And now," said Frank, as he absorbed the last morsels on his plate, "let's see whereabouts on the ridgepole of the earth we have lighted."

The boy's observation showed that they were at a point some two hundred miles to the southwest of the spot in which they had left the crippled dirigible and the Viking ship. The wind had dropped, however, and conditions were favorable for making a fast flight to the place they were now all impatient to reach Frank, after a few minutes' figuring, announced that dusk ought to find them at the Viking ship and, if all went well, in communication with their friends.

No time was lost in replenishing the gasolene tank from the reserve "drums," and carefully inspecting the engine and then a long farewell was bade to the Polar plateau. Without a stop the Golden Eagle winged steadily toward the northeast, and as the wonderful polar sunset was beginning to paint the western sky they made out the black form of the disabled dirigible on the snow barrens not far from the Viking ship's gully.

As they gazed they broke into a cheer, for advancing toward the other dark object at a rapid rate was another blot on the white expanse, which a moment's scrutiny through the glasses showed them was the motor-sledge packed with men on whose rifles the setting sun glinted brightly. The Golden Eagle ten minutes later swooped to earth at a spot not twenty yards from her original landing place and a few moments later the boys were shaking hands and executing a sort of war dance about Captain Barrington and Captain Hazzard, while Ben Stubbs was imploring some one to "shiver his timbers" or "carry away his top-sails" or "keel-haul him" or something to relieve his feelings.

Eagerly the officers pressed for details of the polar discovery, but Frank, after a rapid sketching of conditions as they had observed them at the world's southern axis, went on to describe the events that had led up to their wild flight and urged immediate negotiations with the rival explorers. Both leaders agreed to advance at once, convinced that their force was sufficiently formidable to overcome the Japs.

"Steady, men, and be ready for trouble but make no hostile move till you get the word," warned Captain Hazzard, as the somewhat formidable looking party advanced on the stricken dirigible. At first no sign of life was visible about her, but as they neared the ship Frank saw that the wrecked cabin had been patched up with canvas, and parts of the balloon bag that had not burned, till it formed a fairly snug tent. They were within a hundred paces of it before anyone appeared to have taken any notice of their arrival and then the little officer, who had directed the capture of the adventurers, appeared.

As Billy said afterward, he "never turned a hair," over the conditions that confronted him. He was a beaten man and knew it; but his manner was perfectly suave and calm.

"Good evening, gentlemen," was all he said, with a wave of his hand toward the Viking ship and the pile of ivory and gold that still lay on the edge of the gully, "to the victors belong the spoils and you are without doubt the victors."

He gazed at the array of armed men that backed up the two officers and the boys.

"We have come to take formal possession in the name of the United States, of the remains of the Viking ship," said Captain Hazzard, somewhat coldly, for, after what he had heard from the boys, he felt in no way amiably disposed toward the smiling, suave, little man.

"If you have pen and ink and paper in your cabin we will draw up a formal agreement which will hold good in an international court," supplemented Captain Barrington.

A flash of resentment passed across the other's face but it was gone in an instant.

"Certainly, sir, if you wish it," he said, "but, if it had not been for those boys we should by this time have been far away."

"I do not doubt it," said Captain Barrington, dryly, "and, now, if you please, we will draw up and sign the paper."

Ten minutes later, with the boys' signatures on it as witnesses, the important document was drawn up and sealed with a bit of wax that Captain Hazzard had in his pocket writing-set. And so ended the episode of the attempt to seize the treasure of the Viking ship.

Now only remains to be told the manner of its transporting to the Southern Cross and the last preparations before bidding farewell to the inhospitable land in which they had spent so much time. First, however, the castaways of the dirigible were given transportation on the motor-sledge to their ship which, to the astonishment of all the American party, they found was snugly quartered in a deep gulf, not more than twenty miles to the westward of the berth of the Southern Cross. This accounted for the light and the buzzing of the air-ship being heard so plainly by the Southern Crucians. The defeated Japs sailed at once for the north, departing as silently as they had arrived.

It took many trips of the motor-sledge before the last load of the Viking ship's strange cargo was snugly stored in the hold of the Southern Cross. At Captain Hazzard's command the dead Viking was buried with military honors and his tomb still stands in the "White silence." Then came the dismantling of the Golden Eagle and the packing of the aeroplane in its big boxes.

"Like putting it in a coffin," grunted Billy, as he watched the last cover being screwed on.

All the time this work was going forward the nights and days were disturbed with mighty reports like those of a heavy gun.

The ice was breaking up.

The frozen sea was beginning to be instinct with life. The time for the release of the Southern Cross was close at hand.

At last the tedious period of waiting passed and one night with a mighty crash the ice "cradle" in which the Southern Cross rested parted from the ice-field and the ship floated free. The engineers' force had been busy for a week and in the engine-room all was ready for the start north, but another tedious wait occurred while they waited for the field-ice to commence its weary annual drift.

At last, one morning in early December, Captain Barrington and Captain Hazzard gave the magic order:

"Weigh anchor!"

"Homeward bound!" shouted Ben Stubbs, racing forward like a boy.

A week later, as the Southern Cross was ploughing steadily northward, a dark cloud of smoke appeared on the horizon. It was not made out positively for the relief ship Brutus till an hour had passed and then the rapid-fire gun crackled and the remainder of the daylight rockets were shot off in joyous celebration.

In the midst of the uproar Billy Barnes appeared with a broom.

"Whatever are you going to do with that?" demanded Captain Hazzard, with a smile, as the lad, his eyes shining with eagerness, approached.

"Please, Captain Hazzard, have it run up to the main-mast head," beseeched Billy.

"Have halliards reeved and run it up, Hazzard," said Captain Barrington, who came up at this moment, "the lads have certainly made a clean sweep."

So it came about that a strange emblem that much puzzled the captain of the Brutus was run up to the main-mast head as the two ships drew together.

"That's the Boy Aviators' standard," said Billy, proudly surveying it. "We win."

Shortly afterward a boat from the Brutus came alongside with the mail. "Letters from home," what magic there is in these words to adventurers who have long sojourned in the solitary places of the earth! Eagerly the boys seized theirs and bore them off to quiet corners of the deck.

"Hurrah," cried Billy, after he had skimmed through his epistles. "I'm commissioned to write up the trip for two newspapers and a magazine. How's your news, boys, good?"

The boys looked up from their pile of correspondence.

"I'm afraid we're going to have a regular reception when we get home," said Frank rather apprehensively.

"Hurray! Brass-bands—speeches—red-fire and big-talk," cried Billy.

"None of that for us," said Harry, "I guess we'll retire to the country for a while, till it blows over."

But they did not escape, for on the arrival of the Polar ships in New York the boys and the commanders of the expedition were seized on and lionized till newer idols caught the popular taste. Then, and not till then, were they allowed to settle down in peace and quiet to tabulate the important scientific results of the expedition.

As for the Professor, what he wrote about Professor Tapper—a screed by the way that nearly caused a mortal combat between the two savants—may be read in his massive volume entitled "The Confutation of the Tapper Theory of a South Polar Fur-Bearing Pollywog, by Professor Simeon Sandburr." It weighs twelve pounds, and can be found in any large library.



CONCLUSION.

And here, although the author would dearly like to detail their further adventures, we must bid the Boy Aviators "Farewell." Those who have followed this series know, however, that the lads were not likely to remain long inactive without seeking further aerial adventures. Whether the tale of these will ever be set down cannot at this time be forecast. The Chester boys adventures have been recorded, not as the deeds of paragons or phenomenons, but as examples of what pluck, energy, and a mixture of brains, can accomplish,—and with this valedictory we will once more bid "God speed" to "The Boy Aviators."

THE END.