"I don't know yet," he held up his hand to demand silence.

"That's queer," he exclaimed, after a pause, in which the receiver had buzzed and purred its message into his ear.

The others looked their questions.

"There's something funny about this message," he went on. "I cannot understand it. Whoever is calling has a very weak sending current. I can hardly hear it. One thing is certain though, it's someone in distress."

The others leaned forward eagerly, but their curiosity was not satisfied immediately by Frank. Instead his face became set in concentration once more. After some moments of silence, broken only by the slight noise of the receiver, he pressed his hand on the sending apparatus and the Southern Cross's wireless began to crackle and spit and emit a leaping blue flame.

"What's he sending?" asked Billy, turning to Harry.

"Wait a second," was the rejoinder. The wireless continued to crackle and flash.

"Cracky," suddenly cried Harry, "hark at that, Billy."

"What," sputtered the reporter, "that stuff doesn't mean anything to me. What's he done, picked up a ship or a land station or what?"

"No," was the astounding response, "he's picked up an airship!"

"Oh, get out," protested the amazed Billy.

"That's right," snapped Frank, "as far as I can make out it's a dirigible balloon that has been blown out to sea. They tried to give me their position, and as near as I can comprehend their message, they are between us and the sh.o.r.e somewhere within a radius of about twenty miles."

"Are they in distress?" demanded Billy.

"Yes. The heat has expanded their gas and they fear that the bag of the ship may explode at any moment. They cut off suddenly. The accident may have occurred already."

"Why don't they open the valve?"

"I suppose because in that case they'd stand every chance of dropping into the sea," responded Frank, disconnecting the instrument and removing the head-piece. "I have sent word to them that we will try to rescue them, but I'm afraid it's a slim chance. I must tell Captain Hazzard at once."

Followed by the other two, Frank dashed up the few steps leading to the deck and unceremoniously burst into the captain's cabin where the latter was busy with a ma.s.s of charts and doc.u.ments in company with Captain Barrington, the navigating commander.

"I beg your pardon," exclaimed Frank, as Captain Hazzard looked up, "but I have picked up a most important message by wireless,--two men, in an airship, are in deadly peril not far from us."

The two commanders instantly became interested.

"An airship!" cried Captain Hazzard.

"What's that!" exclaimed Captain Barrington. "Did they give you their position?" he added quickly.

"Yes," replied the boy, and rapidly repeated the lat.i.tude and longitude as he had noted it.

"That means they are to the west of us," exclaimed Captain Barrington as the boy concluded. He hastily picked up a speaking tube and hailed the wheel-house, giving instructions to change the course. He then emerged on deck followed by Captain Hazzard and the boys. The next hour was spent in anxiously scanning the surrounding sea.

Suddenly a man who had been sent into the crow's nest on the main mast gave a hail.

"I see something, sir," he cried, pointing to the southwest.

"What is it," demanded the captain.

"Looks like a big bird," was the response.

Slinging his binoculars round his neck by their strap, Captain Barrington himself clambered into the main shrouds. When he had climbed above the cross-trees he drew out his gla.s.ses and gazed in the direction the lookout indicated. The next minute he gave a shout of triumph.

"There's your dirigible, boys," he exclaimed, and even Billy overcame his dislike to clambering into the rigging for a chance to get a look at the airship they hoped to save.

Viewed even through the gla.s.ses she seemed a speck, no larger than a shoe b.u.t.ton, drifting aimlessly toward the south, but as the Southern Cross drew nearer to her she stood out in more detail. The watchers could then see that she was a large air craft for her type and carried two men, who were running back and forth in apparent panic on her suspended deck. Suddenly one of them swung himself into the rigging and began climbing up the distended sides of the big cigar-shaped gas bag.

"What can he be going to do?" asked Captain Hazzard.

"I think I know," said Frank. "The valve must be stuck and they have decided now that as we are so near they will take a chance and open it and risk a drop into the sea rather than have the over-distended bag blow up."

"Of course. I never thought of that," rejoined the captain, "that's just what they are doing."

"That man is taking a desperate chance," put in Professor Simeon Sandburr, who had climbed up and joined the party and looked with his long legs and big round gla.s.ses, like some queer sort of a bird perched in the rigging. "Hydrogen gas is deadly and if he should inhale any of it he would die like a bug in a camphor bottle."

Interest on board the Southern Cross was now intense in the fate of the dirigible. Even the old chief engineer had left his engines and wiping his hands with a bit of waste, stood gazing at the distressed cloud clipper.

"The mon moost be daft," he exclaimed, "any mon that wud go tae sea in sic a craft moost be daft. It's fair temptin' o' providence."

At that instant there was a sharp and sudden collapse of the balloon bag. It seemed to shrivel like a bit of burned paper, and the structure below it fell like a stone into the ocean, carrying with it the man who had remained on it. Of the other, the one who had climbed the bag, not a trace could be seen. Even as the onlookers gazed horror-stricken at the sudden blotting out of the dirigible before their eyes the loud roar of the explosion of its superheated gas reached their ears.

"Every pound of steam you've got, chief," sharply commanded Captain Barrington, almost before the dirigible vanished, "we must save them yet."

The old engineer dived into his engine room and the Southern Cross, with her gauges registering every pound of steam her boilers could carry, rushed through the water as she never had before in all her plodding career.

"Heaven grant we may not be too late," breathed Captain Hazzard, as, followed by the boys, he clambered out of the rigging. "If only they can swim we may save them."

"Or perhaps they have on life-belts," suggested Billy.

"Neither will do them much good," put in a voice at his elbow grimly.

It was Professor Sandburr.

"Why?" demanded Frank, "we will be alongside in a few minutes now and if they can only keep up we can save them."

"The peril of drowning is not so imminent as another grave danger they face," spoke the professor.

"What's that?"

"Sharks," was the reply, "these waters swarm with them."

CHAPTER V.

A TRAGEDY OF THE SKIES.