Mr. Sharp and
Mr. Jackson in the engine-room.

"All ready," came the answer.

Tom threw over the connecting lever, while his father grasped the
steering wheel. The Advance shot forward, moving swiftly along, about
half submerged.

"She goes! She goes!" cried Tom.

"She certainly does, if I may be permitted to say so," was the calm
contribution of Captain Weston. "I congratulate you."

Faster and faster went the new craft. Mr. Swift headed her toward the
open sea, but stopped just before passing out of the creek, as he was
not yet ready to venture into deep water.

"I want to test the auxiliary propellers," he said. After a little
longer trial of the electric propulsion plates, which were found to
work satisfactorily, sending the submarine up and down the creek at a
fast rate, the screws, such as are used on most submarines, were put
into gear. They did well, but were not equal to the plates, nor was so
much expected of them.

"I am perfectly satisfied," announced Mr. Swift as he once more headed
the boat to sea. "I think, Captain Weston, you had better go below now."

"Why so?"

"Because I am going to completely submerge the craft. Tom, close the
conning tower door. Perhaps you will come in here with us, Captain
Weston, though it will be rather a tight fit."

"Thank you, I will. I want to see how it feels to be in a pilot house
under water."

Tom closed the water-tight door of the conning tower. Word was sent
through the tube to the engine-room that a more severe test of the ship
was about to be made. The craft was now outside the line of breakers
and in the open sea.

"Is everything ready, Tom?" asked his father in a quiet voice.

"Everything," replied the lad nervously, for the anticipation of being
about to sink below the surface was telling on them all, even on the
calm, old sea captain.

"Then open the tanks and admit the water," ordered Mr. Swift.

His son turned a valve and adjusted some levers. There was a hissing
sound, and the Advance began sinking. She was about to dive beneath the
surface of the ocean, and those aboard her were destined to go through
a terrible experience before she rose again.

Chapter Eleven

On the Ocean Bed

Lower and lower sank the submarine. There was a swirling and foaming of
the water as she went down, caused by the air bubbles which the craft
carried with her in her descent. Only the top of the conning tower was
out of water now, the ocean having