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 compa.s.s 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 compa.s.s 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 hara.s.sing 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 compa.s.s.

"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 compa.s.s, 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 alt.i.tude. 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 compa.s.s 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?"