ere instantly given.

"Keep the engines up to their best performance all the way," was
Dave's order. "Boatswain's mate, watch sharp for the courses, as I may
change frequently."

"Aye, aye, sir."

Heading out of North Channel, Dave drove back for Valetta, keeping
about a mile off the coast.

After making a few knots, he came abreast of another British launch
that lay further to seaward. With lantern signals the Englishman
asked:

"Is the submarine supposed to be loose?"

"Yes," Dave had his signalman reply.

"Where?"

"Don't know."

"I'm here to warn incoming ships against entering Grand Harbor
to-night," the Englishman wound up. "Are you seeking the submarine?"

"Yes," Dave had flashed back.

"Good luck to you!" came heartily from the English launch.

"Thank you," was Darrin's final response.

The searchlight of Dave's launch was swinging busily from side to
side, searching every bit of the water's surface that could be
reached.

"If the submarine comes up, Runkle, you may be the first to sight
her," Dave smiled to that seaman, who stood beside him.

"Aye, aye, sir; if I sight that craft I won't be mean enough to keep
my news to myself."

"I wonder where Dalzell is," thought Dave. "What is he doing in this
night's work?"

As for Ensign Dave, his every nerve was keyed to its highest pitch.
Outwardly he was wholly calm, but he felt all the responsibility that
rested upon him to-night, as did every other officer who commanded a
launch from either fleet.

Searchlight and naked vision were not enough. Almost constantly Darrin
had his night glass at his eyes.

Suddenly, as the light shifted over the water, Dave thought he caught
sight of something unusual.

"Steady with that light there, signalman," he commanded suddenly.
"Back slowly to port with the beam."

Darrin forced himself to be calm.

"Steady," he called, again. "Hold the light on anything you see,
signalman."

"Aye, aye, sir; I _do_ see something," replied the man who was
manipulating the searchlight.

That he did see the mysterious something was proved by the manner in
which he kept the light upon it.

That on which Darrin now trained his night glass was a marked rippling
on the water, half a mile away, and farther seaward. A landsman would
have missed it altogether. Yet that rippling on the sea's surface was
clearly different from the motion of the water near by.

"It might be a school of large fish," Dave mused aloud, in Run