It was soon evident that the two men were supporting themselves in the water. Their heads made black dots on the surface beneath which the heavy deck structure of the dirigible had vanished. Through the gla.s.ses it could be seen that they were swimming about awaiting the arrival of the vessel which was rushing at her top speed to their aid.

Soon the Southern Cross was alongside and a dozen ropes and life buoys were hastily cast over the side. But even as one of the men grasped a rope's end he gave a scream of terror that long rang in the boys'

ears.

At the same instant a huge, dark body shot through the water and then there was a whitish gleam as the monster shark turned on its back with its jaws open displaying a triple row of saw-like teeth.

"Quick, shoot him," cried Captain Hazzard.

But n.o.body had a rifle or revolver. Frank hastily darted into his cabin for his magazine weapon but when he reappeared there was only a crimson circle on the water to mark where the terrible, man-killing shark had vanished with his prey. Attracted, no doubt, by the mysterious sense that tells these sea tigers where they can snap up a meal, other dark fins now began to cut through the water in all directions.

The second man, almost overcome by the horror of his companion's fate, however, had presence of mind enough to grasp a rope's end. In a few seconds he had been hauled to the vessel's side and several of the crew were preparing to hoist him on board when two of the monsters made a simultaneous rush at him, Frank's revolver cracked at the same instant and the sea tigers, with savage snaps of their jaws, which, however, fell short of their intended prey, rolled over and vanished.

The rescued man when hauled on deck was a pitiable object. But even in his half famished condition and with the great beard that he wore there was something very familiar--strangely so--about him to the boys. Frank was the first to solve the mystery.

"Ben Stubbs," he exclaimed.

"Who's that that called Ben Stubbs," exclaimed the man over whom a dozen sailors and the doctor had been bending.

"It's me," shouted Frank, regardless of grammar, "Frank Chester."

The amazement on the face of the old salt who had accompanied the boys in Africa and the Everglades and shared their perils in the Sarga.s.so Sea, was comical to behold.

"Well, what in the name of the great horn-spoon air you boys doing here," he gasped, for Harry and Billy had now come forward and were warmly shaking his hand.

"Well, answer us first: what are you doing here?" demanded Frank.

"Coming mighty near my finish like my poor mate," was the reply.

"Perhaps your friend had better come in the cabin and have something to eat while he talks," suggested Captain Hazzard to the boys.

All agreed that that would be a good idea and the castaway was escorted to the cabin table on which Hiram Scroggs the Vermonter soon spread a fine meal.

"Wall, first and foremost," began Ben, the meal being dispatched, "I 'spose you want to know how I come to be out here skydoodling around in a dirigible?"

"That's it," cried Billy.

"It's just this way," resumed the old sailor drawing out his aged pipe. "Yer see, my pardner, James Melville,--that's the poor feller that's dead,--and me was trying out his new air-craft when we got blown out ter sea. We'd been goin' fer two days when you picked up the wireless call for help he was sending out. I used ter say that wireless was a fool thing ter have on an air-ship, but I owe my life ter it all right.

"Ter go back a bit, I met Melville soon after we got back from the treasure hunt. He was a friend of my sister's husband and as full of ideas as a bird dog of fleas. But he didn't have no money to carry out his inventions and as I had a pocketful I couldn't exactly figure how to use, I agreed to back him in his wireless dirigible. We tried her out several times ash.o.r.e and then shipped her to Floridy, meaning to try to fly to Cuba. But day afore yesterday while we was up on a trial flight the wind got up in a hurry and at the same moment something busted on the engine and, before we knew where we was, we was out at sea."

"You must have been scared to death," put in Professor Sandburr who was an interested listener.

"Not at first we wasn't. Poor Melville in fact seemed to think it was a fine chance to test his ship. He managed to tinker up the engine after working all night and part of yesterday on it and as we had plenty to eat and drink on board--for we had stocked the boat up preparatory to flying to Cuba--we didn't worry much.

"Howsomever, early this morning, after we'd had the engine going all night we found we was still in the same position and for a mighty good reason--one of the blades of the propeller had snapped off and there we were,--practically just where we'd been the night before and with no chance doing anything but drift about and wait for help. Melville never lost his nerve though.

"'We'll be all right, Ben,' says he to me, and though I didn't feel near so confident, still I chirped up a little for I had been feeling pretty blue, I tell you.

"Right after we had had a bite to eat he starts in hammering away at the wireless, sending out calls for help while I just sat around and hoped something would turn up. Some observations we took showed that we had not drifted very much further from land in the night on account of there being no wind. This looked good for it meant that we were, or should be, in the path of ships. The only thing that worried me was that mighty few coasting vessels carry wireless, and I was surprised when we got an answer from what I knew later was the Southern Cross.

"It was just as Melville was getting your answer that I noticed the bag. The air had grown hot as an oven as the sun rose higher and about noon I looked up just to see if there wasn't a cloud in the sky that might mean a storm, and perhaps a change of wind that maybe would blow us back over land again. What I saw scared me. The bag was blown out as tight as the skin of a sausage, and it didn't look to me as if it could swell much more without busting.

"I pointed it out to Melville and he went up in the air--worried to death.

"'The gas is expanding,' he explains, 'it's the sun that's doing it.

If we don't let some gas out we'll bust.'

"And if we do we'll drop into the sea," says I.

"'Yes, that's very likely,' he replied, as cool as a cuc.u.mber, 'when the evening comes and the gas condenses, with what we've lost, if we pull the valve open, we won't have enough to keep the ship in the air.'

"'There's only one thing to do,' he went on, 'we must wait till this ship I've been speaking to by wireless comes in sight. Then we'll take a chance. If the worst comes to worst we can float about till they pick us up.'

"That seemed a good plan to me and I never gave the sharks a thought.

But when you drew near and it seemed as if the bag was going to bust in a second's time and we tried to open the valve--we couldn't. The halliards that work it had got twisted in the gale that blew us out to sea and they wouldn't come untangled.

"Melville takes a look at the pressure gauge. Then he gave a long whistle.

"'If we don't do something she'll bust in five seconds,' he says.

"Then I suddenly made up my mind. Without saying a word to him I kicked off my boots and started to climb into the rigging.

"'What are you going to do?' asked Melville.

"Open that valve, says I.

"We saw you climbing and could not imagine what you were doing," put in Billy.

"Wall," continued the old sailor, "I managed fine at first, although that thar gas sausage was stretched as smooth and tight as a drum. The network around it gave me a foothold though, and once I was half-way round the lower bulge of the bag--where I was clinging on upside down,--I was all right.

"I had the valve lever in my hand and was just going to open it when I felt everything cave in around me like something had been pulled from under my feet--or as if I had been sitting on a cloud and it had melted.

"The dirigible had blown up.

"Luckily I kept my wits about me and deliberately made a dive for the sea. It was a good height but I struck it clean. Down and down I went till I thought I'd never come up again. My ear-drums felt like they'd bust and my head seemed to have been hit with an axe. But come up I did eventually as you know, and found poor George Melville there, too.

Of the dirigible there was not so much of as a match-stick left. The rest you know."

Ben's voice shook a little as he reached the latter part of his narrative. The rugged sailor's face grew soft and he winked back a tear. The others said nothing for a few seconds and then Captain Hazzard looked up.

"Since you have become one of us in such a strange way, I presume you would like to know where we are bound for?"

"Wall, if it ain't askin' too much I would," rejoined the rugged adventurer.

"We are bound for the South Pole."

Ben never flicked an eyelid.