hey had tramped around the
spot without ascertaining what had become of the man.

"Looks as if the earth had opened and swallowed him up," remarked
Randy.

The cadets had advanced with caution, but now they grew bolder, and
made a closer examination. But it was all of no avail--the man had
disappeared, and where he had gone to or how, there was no telling.

"One thing is sure," declared Jack. "He didn't walk away from here,
and he didn't go up into the air. That being so, he must have gone
down somewhere among the rocks and bushes. We had better hunt around
for some sort of an opening to a cave, or something like that."

The others were willing enough, and spent the best part of an hour in
the task. But no opening presented itself, although the rocks and
rough places in that vicinity were numerous.

"Here is something else we can report to Captain Dale," was Fred's
comment.

Not knowing what else to do, the boys marked the spot so that they
could remember it, and then pushed onward through the forest. Two
hours later they reached a sort of gully, with the rough rocks on one
side and an overhanging cliff on the other.

"Fine place for snakes," remarked Spouter, as they walked along.

"We're not looking for snakes, so please don't mention them," answered
Jack.

Why they did it, the boys could not explain afterwards, but they
continued along the gully until they reached a point where there was
something of a split in the face of the cliff.

"Here's another one of those caves just like that which we found over
on the bay front," declared Fred. "Let's go in and see what it looks
like."

With nothing in particular in view, the others were willing, and,
turning on a flashlight which they had brought along, they climbed
down into the cave-like opening. It was very irregular in shape, and
they had to proceed with caution.

And then, while they were climbing down among the rocks, something
happened which caused each of the cadets to start wildly. A strange
rumbling sound filled the air, a blowing and hissing, and then came a
pounding and a clanking, sounding with great clearness in that
confined space.

"It's the same noises we heard before, and they are not very far off!"
cried Jack to the others. "There must be a workshop of some sort
around here."

Hardly knowing what to expect, the boys continued to climb down into
the opening they had discovered. Soon they reached a narrow
passageway, where going was a li