hidden river, such as are common enough among the
mountains, but the stream had been diverted, probably by some sort of
landslide, and had left this tumbler-shaped cave, resembling a pit
shaft. Now, I thought, I have only to find out what all this machinery
is for and the whole mystery is solved. I opened the trap a little
further, and allowed my body to hang slightly over the edge.

Then for the first time I saw, to my right, fixed so that it almost
touched the floor of the hut, a great round brass object, mounted on
an enormous tripod, which, again, stood on a platform. In front of
this was a large square thing like a mammoth rectangular condenser,
such as is used for photographic enlarging and other projection
purposes. Had it not been for this condenser I should have taken the
whole thing to be an elaborate searchlight. But, I asked myself, what
would be the good of a searchlight there? Suddenly the whole truth
dawned upon me.

The searchlight must operate through a trap in the wall of the hut
just below the floor. I leaned further in, forgetting my danger in the
intoxication of sudden discovery.

Only a foot or two away from me a man was working on the searchlight.
Carefully taking it to pieces, he was handing the parts to another
man, who was perched on the scaffold below him. He was so close to
me that I could hear him breathing. I was about to wriggle back to
safety when he looked up. He gave a sudden loud shout. I lay there
fascinated. After all, I thought, before they can reach me I can slip
out and edge round the cliff, run down on to the shore, and get away
in the motor-boat. But I had reckoned without my host. Even as the man
shouted, and the others left their work to see what was the matter,
Fuller dashed out from behind the platform, gave one terrified look at
me, and, flinging himself at the wall of the cavern, threw all his
weight on a rope which dangled there. I scuttled to my feet, intending
to make a bolt for it. But the boards shivered beneath me, and, before
I could realise what was happening, I found myself hurtling through
the air to the floor of the cavern below.

CHAPTER XVII.

SOME GRAVE FEARS.

And now, as the reader will readily understand, I must continue the
story as it was afterwards related to me.

Myra, the General, and Dennis sat up and waited for me till the
early hours of the morning, but I did not return. The young people did
what they could to assure the old man t