n the palm glittered a large
stone--ostensibly a diamond. In the rays of the moon it showed all the
colors of the rainbow--a beautiful gem. "That is one of the stones I
made--or rather that I supposed I had made," went on Mr. Jenks. "It is
one of several I have, but they have not all been cut and polished as
has this one.

"Naturally I was much impressed by what I saw, and, after I had made
certain tests which convinced me that the stones in the steel box were
diamonds, I paid over the money as I had promised. That was my undoing."

"How?"

"As soon as the men got the cash, they had no further use for me. The
next I remember is eating a rude meal, while we discussed the future of
making diamonds. I knew nothing more until I found myself back in the
small hotel at Indian Ridge, whence I had gone some time previous, with
the men, to the cave in the mountain."

"What happened?" asked Tom, much surprised by the unexpected outcome of
the affair. "I had been tricked, that was all! As soon as the men had my
money they had no further use for me. They did not want me to learn the
secret of their diamond making, and they drugged me, carried me away
from the cave, and left me in the hotel."

"Didn't you try to find the cave again?"

"I did, but without avail. I spent some time in the Rockies, but no one
could tell where Phantom Mountain was; in fact, few had heard of it, and
I was nearly lost searching for it.

"I came back East, determined to get even. I had given the men a
very large sum of money, and, in exchange, they had given me several
diamonds. Probably the stones are worth nearly as much as the money I
invested, but I was cheated, for I was promised an equal share in the
profits. These were denied me, and I was tricked. I determined to be
revenged, or at least to discover the secret of making diamonds. It is
my right."

"I agree with you," spoke Tom.

"But, up to the time I met you on Earthquake Island, I could form no
plan for discovering Phantom Mountain, and learning the secret of the
diamond makers," went on Mr. Jenks. "I carried the gems about with me,
as you doubtless saw when we were on the island. But I knew I needed an
airship in which to fly over the mountains, and pick out the location of
the cave where the diamonds are made."

"But how can you locate it, if you were blindfolded when you were taken
there, Mr. Jenks?"

"I forgot to tell you that, on our journey into the mountains, and just
before