kle's
hearing, "though at night they are likely to rest. Runkle, and you,
men, keep your eyes peeled to see if you can make out fish leaping out
of the water."

The ripple continued, unbroken at any point. Moreover, it moved at
uniform speed, and in a line nearly parallel with the coast.

Gradually the launch gained on that ripple. Dave could not turn his
fascinated gaze away from the sight.

"I think I know what that is, sir," broke in Seaman Runkle, after
three minutes of watching.

"I am sure that I _do_, Runkle," Dave Darrin returned. "It's a
submarine, for some reason just barely submerged. That line of ripple
is the wake left by her periscope."

As if to confirm the young naval officer's words, the ripple parted.
As the line on the water broke, the periscope came fully into view,
and the turret showed above water, continuing to rise until the deck
was awash.

"There's the pest of the seas!" cried an excited voice.

Every man on the launch was now straining his eyes for a better look
at the submarine, barely a quarter of a mile away.

CHAPTER XXIII

THE PUZZLE OF THE DEEP

"Coxswain!" shouted Dave.

"Aye, aye, sir."

"Send up three blue rockets!"

"Aye, aye, sir."

One after another the rockets ascended, bursting high overhead and
slowly falling.

From Grand Harbor, several miles distant, a rocket ascended and burst,
showing red.

Darrin's signal had been seen and answered. Both fleets now knew that
one of the launches had sighted the submarine craft. The three blue
rockets had been the signal agreed upon in advance. Runkle was at the
gun. Ensign Darrin gave him the range.

"I wish we had a four-inch gun in the bow," Dave muttered wistfully,
"but we'll have to do the best we can with the one-pounder. Ready!
Fire!"

Even before the command to fire had been uttered the craft ahead had
begun to submerge.

As the brisk, snappy report of the little piece sounded, and a faint
puff of smoke left her muzzle, Runkle's head bobbed up to watch the
result of his shot.

"Forward of her turret by about a foot!" Runkle muttered in disgusted
criticism of his own shooting.

A sailor had thrown the breech open, while a second swabbed the bore
through and the first fitted in a fresh shell, closing the breech with
a snap.

Runkle seemed to sight and fire almost in the same instant, and, as
before, straightened up to watch the accuracy of his shot by the
splash of water on the other side of the