On came the whale. She was a huge, humpbacked monster, with a gigantic square head that looked as solid as the prow of a battleship. Every instant appeared to increase the speed at which she traveled. Fascinated by terror they could not take their eyes off the onrushing peril,—with the exception, that is, of Jack.

The boy was struggling with an auxiliary valve for gas supply which had been installed with the idea of quick-filling the bag. But the ordinary valve had worked so well alone that the auxiliary had not been used, and it was jammed and corroded.

“Hurry! hurry!” shouted Tom. “She’ll ram us in another second!”

But still the ship would not rise. The bag was swelling every instant, though, and it seemed that if they were granted only a molecule more of time there might be a possibility of rising before the whale struck them.

Among other things, the Wondership had been provided with conveniently placed life preservers. Jack now shouted to the others to put these on.

“When she hits, jump outwards!” he yelled.

They began to adjust the life saving contrivances, which laced on like jackets. But before they had them half ready the whale was within a few feet of the craft. Such was her speed that in front of her there was a mighty mass of blue water piled up. Her blunt, square forehead had raised the billow just as a round-bowed ship will “push the river in front of it,” to use a graphic sailor phrase.

And now an astonishing thing happened. The wave struck the frail motor ship a few seconds before the impact of the whale’s head. The great sea gave the craft just the impetus that was required. Buoyed up by the inflated gas-bag the wonder craft rose into the air as the wave rolled under her, and hung suspended in that element for some minutes. She did not rise far above the water, but the five or six feet that she reached was sufficient to clear the onrushing whale.

As the huge, humped back with its ugly rough hide passed under them Captain Sprowl picked up a rifle and pumped an unmerciful stream of lead into the monster.

Instantly she spouted, and the boys and their companions found themselves in the midst of a downpour of water and vapor. But the main danger had almost miraculously been avoided. As the Wondership settled down to the water once more, the whale could be seen rushing blindly on. A cheer went up from the boys.

“That’s the time we fooled her!” cried Tom exultantly.

But Captain Sprowl urged Jack to get the bag fully inflated as quickly as possible.

“She’ll be back afore long,” he prophesied. “She’s as mad as Pharaoh’s sow right now, and she won’t give up as easy as all that.”

Sure enough, in a few minutes the mound of water that marked the whale’s progress could be seen returning toward them at the same rapid speed. But by this time, Jack had secured a wrench and had managed to turn the stubborn auxiliary valve. As the whale neared them, he set the rising planes and started up the propeller.

The motor craft hesitated, and then like a wind-driven leaf she shot upward. It was not an instant too soon. As her rudder rose drippingly from the sea, the whale rushed viciously under her. Another fraction of a second and there would have been a different ending to this story.

“Saved, by the great horn spoon!” roared out Captain Sprowl. “Lad, that gas-meter thing of yours worked just in time.”

“It certainly did,” agreed Jack, ordering Tom to set the rising planes at a sharper angle.

“Look!” shouted Tom suddenly as they shot upward, soaring above the smooth surface of the ocean. “The sword-fish is going to attack the whale herself, now.”

They saw, far below them, the sword-fish’s ivory blade, stained red from its attack on the baby whale, rushing at the old cow. She gave battle bravely. In an instant the waters were lashed into such a fury that they could see nothing of the details of the battle.

But Professor Von Dinkelspeil, who had brought his binoculars with him from the wreck, determined, in the interests of science, to see all he could of the battle. He leaned far over the side.

“Ach! vot a sight! I nezzer saw such a dings!” he cried. “Oh! I vish I hadt a camera!”

“I’ve got mine,” cried Dick. “I’ll take a picture!”

The red-headed young journalist leaned out over the edge of the Wondership and tried to get a focus on the furious battle beneath.

“Look out, you’ll overbalance!” called Tom.

But the good advice came too late.

Without the slightest warning to give them a chance to save him, Dick Donovan’s body pitched over the side of the craft and fell like a stone downward through space.

For an instant the shock of the occurrence held them all spellbound. Then they woke into action with a series of shouts and cries that made inextricable confusion.

“Send us down! Send us down!” cried Mr. Chadwick.

“I daren’t,” declared Jack, “those creatures would certainly ram us.”

“Quick! Help him!” cried Tom, who had been leaning over watching the spot where Dick had vanished. It was not far from the place where the two monsters of the sea were battling, some two hundred feet beneath the flying ship.

Jack’s face was pale, but his manner was determined as he shut off the engine and ordered Tom to get out the grapnel rope. This was a rope some five hundred feet in length, of light but exceedingly strong fiber. At its end was a grapnel, a sort of four-forked anchor. The idea of it was to anchor the Wondership in case of a high wind or other emergency.

Tom produced the rope and Jack flung off his garments down to his underclothes. While he did this Tom had, in obedience to his chum’s orders, made the rope fast to an interior stanchion of the ship.

“See if you can spot him,” Jack said to Tom when the rope had been made fast.

“Yes! Yes! I see him!” cried Tom excitedly, as he looked over the side. “The life-jacket is floating him but he looks half drowned. He can’t strike out to save himself.”

“The fall must have stunned him,” cried Mr. Chadwick; “it’s a good thing he had that life-jacket on!”

Jack began climbing over the side, holding on to the rope that now dangled from the floating air craft.

“What are you going to do?” demanded Tom, who up to this moment had imagined that Jack meant to catch Dick by the grapnel.

“I’m going down after Dick,” was the quiet response as the boy shot down the rope toward the sea beneath. “Keep an eye on that rope, Tom, and haul up when I tell you!”

“Ach! dey vill both be killed!” cried the professor frenziedly. “Dis iss madtness!”

But Jack Chadwick was not a boy who did things without having first figured them out. As he slid down the rope he knew just what he meant to do when he touched the water.

In the meantime Dick’s body, buoyed up by the life-belt he had so luckily neglected to remove, was floating on the surface. About an hundred feet off, the whale and the sword-fish were battling furiously.

In mid-air the Wondership hung suspended, her white-faced, frightened passengers peering over the side, while between the air-buoyed craft and the sea Jack Chadwick’s body swung on the thin rope like a pendulum.