, but I can hit on no other explanation
of his actions. He is angry at us because he thinks we may see too
much. Look, they are still signalling."

"I wish we could read what they are saying."

"I think I can," rejoined Rob quietly.

"You can?"

"Yes."

"How are you going to do it?"

"By bringing my knowledge of Morse into play. I think that when the flag
is run up slowly it means a dash and a quick run is a dot. Let's try it
anyway."

Luckily the spot where the two boys were was grown with high, coarse
grass, and the sand dunes rose high in places, affording protection for
them.

As the flag rose and fell they spelled out a word according to the Morse
code.

"That's 'Ready'," proclaimed Rob exultingly; "we have hit on their code,
all right."

"They're still at it," exclaimed Merritt, as the flag continued its
eccentric rises and falls; "what's next, I wonder?"

Dash--dash--dash--dash, spelled out the flag.

"That means 'to'," declared Rob.

"Yes, and there comes 'night'," exclaimed Merritt a moment later. "And
now they've stopped. Let's see what message we've caught."

"Short and sweet," laughed Rob. "I guess we came in at the tail end of
their confab. All we've got is 'Ready to-night'."

"Well, isn't that something?" demanded Merritt. "At all events it's a
complete sentence and tells us that somebody will be ready for something
to-night."

"Right you are, and that 'somebody' is to be Barton, I'll bet a
doughnut."

"But ready for what?"

"That remains to be seen. I've always thought Barton would bear
watching. I'm certain of it now, and if the submarine isn't mixed up in
this tangle somewhere, call me a Chinaman."

"Are you going to tell the ensign about this?"

"Not till we have something more tangible to go upon. After all, we have
proved nothing, but to-night we'll keep a close watch on Barton and in
that way find out if our suspicions are correct or not."

And so it was arranged. The boys hunted a bit more, but somehow the
strange signals and the peculiar behavior of Barton had got on their
minds, and they gave up their sport earlier than they had expected and
trudged back to camp to complete their arrangements for the night's
work.

CHAPTER XVI.

SCOUTING FOR UNCLE SAM.

"Rob! Rob! Rob!"

Merritt nudged his dozing companion as they lay near to the submarine
shed, where they had taken up their position earlier in the night.
Immediately after supper the lads had, apparent