enter the lock and fill it with water. Once the external pressure is
released he can open the outer door and step out. Coming back, he seals
the outer door and the man inside blows out the lock and compressed air
and then the inner door can be opened. It is the same principle as a
torpedo tube."

* * * * *

A jangle of bells interrupted them and the _Minneconsin_ slowed down.
Commander Lawrence stepped to the rail and gave a sharp order to the
navigating officer on the bridge. The bells jangled again and the ship's
engines stopped.

"We are almost over the buoy, Doctor," he said.

Dr. Bird nodded and spoke to the two mechanics. With a few final
touches to the apparatus they emerged from the globe and Dr. Bird
entered.

"Come on, Carnes," he called. "No backing out at the last minute."

Carnes stepped forward with a sickly smile and joined the Doctor in the
huge sphere.

"All right, boys; close her up."

The mechanics swung the outer door into place with a crane. Both the
edge of the door and the surface against which it fitted had been ground
flat and were in addition faced with soft rubber. Bolts were fastened in
the door which passed through holes in the main sphere, and Dr. Bird
spun nuts onto them and tightened them with a heavy wrench. He and
Carnes lifted the smaller inner door into place and bolted it tight. Dr.
Bird stepped to the telephone.

"Lower away," he directed.

From a boom attached to the _Minneconsin's_ forward fighting top, a huge
steel cable swung down, and the latch at the end of the cable was closed
over a vitrilene ring which was fastened to the top of the sphere. The
cable tightened and the globe with the two men in it was lifted over the
side of the battleship and lowered gently into the water. Carnes
involuntarily ducked and threw up his hand as the waters closed over
them. Dr. Bird laughed.

"Look up, Carnes," he said.

Carnes gasped as he looked up and saw the surface of the water above
him. Dr. Bird laughed again and turned to the telephone.

"Lower away," he said. "Everything is tight."

* * * * *

The globe descended into the depths of the sea. Darker and darker it
grew until only a faint twilight glow filled the sphere. A dark bulk
loomed before them. Dr. Bird snapped on one of his huge floodlights and
pointed.

"The _Arethusa_," he said.

The ill-fated vessel lay on her side with a huge jagged hole torn