The safety valve could be set for any desired depth; when the vessel
dropped to that depth the ballast tanks were automatically opened and
every ounce of water expelled. As a result the submarine would shoot
to the surface. The older "submarine salts" called the safety the
"tripper."

"If they've punctured us we might as well cut loose and take our
chances on the surface," declared Lieutenant McClure to the little
group of officers standing with him amidships in the control chamber.

Not a man dissented. They were content to abide by the word of their
chieftain. It was some relief to know that the nose of the destroyer
had not crashed through the skin of the submarine; but, from the
concussion astern and Chief Engineer Blaine's report, it was very
evident that the _Dewey_ had been struck a glancing blow. Deep-sea
pressure against a weakened plate could have but one inevitable
sequel---the rending of the ship's hull.

"They have gone completely over us," came the announcement from the
wireless room.

Hardly had the electrician concluded the report before the _Dewey_
was rocked by another submarine detonation---the explosion of a
second depth bomb. This time it was farther from the hiding vessel;
however, the ship was shaken until every electric light blinked in
its socket.

"I hope they soon get done with their Fourth of July celebration,"
remarked Bill Witt by way of a bit of subsea repartee.