Still the Dart kept on her course.

Frank looked in vain for the signs of land described by Captain Bell. To him they did not exist.

He had no means of knowing at what depth they were.

But he knew that their situation was hourly growing more critical.

Then Prof. Von Bulow came to him.

“I have a request to make.

“If you should succeed in reaching home alive tell my wife that I sent her my love in my dying breath.”

Frank took the scientist’s hand.

“Of course I would do that,” he said. “But there is no more chance for me to reach home safely than for you.”

“I understand,” said Von Bulow, sadly; “but it is a comfort to me.”

“Then I will promise,” said Frank.

Just at this moment came the climax.

Barney came running into the cabin with his face as pale as chalk.

“Misther Frank!” he cried, “the chemical generator has failed to worruk, an’ the air is all going, sor!”

At once active measures were taken to meet the end.

The helmets were hurriedly brought and donned.

It was none too soon, for the air in the cabin was quickly exhausted. Then the Dart came to a stop, for it was useless to attempt to run it without the aid of the pneumatic engine.

The Dart was securely anchored, and then, as lightly equipped as possible, the explorers set forth upon their apparently hopeless quest for land.

On and on they wandered.

What seemed like an interminable period elapsed.

Still there was no sign of land.

............