aptain of the tug, which held the former to
his course, and the latter was biding his time. Studying hard, the
American could think of no scheme which promised the slightest success
in this direction, but none the less, he was convinced that something
was on foot, and that it could be frustrated only by alertness on his
own part.

In this uncomfortable frame of mind, he came down from the upper deck
and followed his two friends forward, where they were leaning against
the pile of wood near the gun. Both were smoking and occasionally
glancing up at the pilot house, as if they too were apprehensive of
the man, whose head and shoulders were in sight. He had resumed
smoking and the tip of his cigarette glowed in the moonlight.

The three stood for a few minutes without speaking, when Martella
straightened up and asked in a low voice:

"Have you noticed, Major, that our speed has increased within the last
few minutes?"

The American looked off over the water and then at the shore, but
could see nothing to enlighten him.

"The other boat is falling behind," said Captain Guzman.

Glancing at the smaller craft, all doubt was instantly removed. The
tug was steadily drawing away from it.

"Captain," he called, looking up at the pilot house; "we are going too
fast; slacken your speed."

"As you please, Senor; I beg your pardon."

The signal was sent down to the engineer, who quickly brought about a
diminution in the progress of the tug.

"Probably it was unintentional--"

At that moment, all felt a jar through the craft, accompanied by such
a rapid slackening of pace that the three took an involuntary step
forward.

"We've run aground!" exclaimed Starland.

"There's no doubt of it," calmly added Martella.

CHAPTER XXX.

"It was done purposely!" added the American, placing his hand on his
revolver. Glancing up from where he stood, the head and shoulders of
Captain Ortega were in fair sight through the lowered slide at the
front of the pilot house. He made no attempt to elude the bullet that
he must have expected.

But prudence told the American to wait. The services of the other were
too valuable for the time to be thrown away, even though the man was
under suspicion. Besides, there was one chance in a hundred that the
mishap was unintentional.

Hardly had the motion of the boat ceased, when the double clinking of
the gong in the engine room sounded, accompanied by the jangling of
the bell, which cal