ttle easier. Then they came to a spot
where there was considerable wetness, showing that they had reached
the level of the water in the bay beyond.

"Here is a regular underground waterway," declared Gif presently. "It
looks to be pretty deep, too."

He was right. To the surprise of everybody they had come out upon what
seemed to be an underground pond. On the side upon which they had
emerged there was a small sandy slope. The other side, and the far
end, were covered with jagged rocks.

The strange blowing, pounding, and clanking continued, and almost
deafened the cadets. They felt that they were on the point of a great
discovery, but could not imagine what it would be.

"It's a workshop, all right enough," declared Fred, a minute later.
"Jack, put out that light, quick!" And at this command the flashlight
was turned off.

The cadets had rounded a bend of the underground waterway, and now at
a distance they saw a number of electric lights shining brightly.
There was some machinery set up among the rocks, and several workmen
were present, all seemingly busy.

"Look!" exclaimed Jack, his eyes almost starting out of his head at
the sight. "What do you think of that, fellows?"

He pointed to a spot beyond where the strange men were working. There
the waterway seemed to broaden and deepen, and in the water lay a
strange-looking craft more than three-quarters submerged.

"It's a submarine!" breathed Fred excitedly. "A submarine! What do you
know about that?"

[Illustration: "A SUBMARINE! WHAT DO YOU KNOW ABOUT THAT?"
_Page 270_]

CHAPTER XXVII

ON BOARD THE SUBMARINE

The Rover boys and their chums were so astonished at the discovery
they had made that for a moment they could do little else than stare
at the strange object resting in the water ahead of them.

"Get out of sight, every one of you!" whispered Jack, who was the
first to recover his self-possession. "Don't let those men see you!"

All backed away as silently as possible until they were once more in
the shelter of the rocks of the bend around which they had come.

"Say, do you think those fellows are Germans?" whispered Randy
excitedly.

"I certainly do, Randy," answered the young captain.

"Of course they are Germans!" put in Gif. "If they were Americans why
would they be concealing themselves in such an out-of-the-way place as
this?"

"It's a German submarine, as sure as you're alive!" remarked Spouter.
"Fellows, we have made a w