f the lanterns, set about
examining the rock of which the cave consisted.

In a short time Bill Renshaw returned with enough food to last for two
days. He said he was going out on the mountain once more to act the part
of a lookout, and would visit the adventurers again the next day.

"In the meanwhile you can do just as you please," he said. "Nobody is
likely to disturb you here, and you can sneak up and take a look at the
men in the other cave whenever you're ready. Only be careful--that's all
I've got to say. They're desperate men."

It was not very pleasant, eating in the gloomy cavern, but they made the
best of it. They cooked on a small oil-stove they found in the place,
and after some hot coffee they felt much better.

"Well," remarked Tom, after a while, "shall we take a chance, and go
look at the men at work?"

"I think so," answered Mr. Jenks. "The sooner we discover this mystery,
the better. Then we can go back home."

"And recover my airship," added Tom, who was a bit uneasy regarding the
safety of the Red Cloud.

"Then, bless my finger-rings! let's go and see if we can find the big
cave your friend the ghost told us of," suggested Mr. Damon.

Cautiously they made their way along the passage Bill had pointed out.
As they went forward the subdued noise became louder, and finally they
could feel the vibration of machinery.

"This is the place," whispered Mr. Jenks. "That sound we hear is one of
the mixing machines, for grinding the materials--carbon and the other
substances--which go to make up the diamonds. I remember hearing that
when I was in the cave before."

"Then we must be near the place," observed Tom.

"Yes, but I didn't have much chance to look around when I was here
before. They wouldn't let me. I never even knew of the small cave Bill
took us to."

"Well, if we're close to it, we'd better go cautiously, and not talk any
more than we're obliged to," suggested Mr. Parker, and they agreed that
this was good advice.

They walked on softly. Suddenly Tom, who was in the lead, saw a gleam of
light.

"We're here," he whispered. "I'll put out our lantern, now," which he
did. Then, stealing forward he and the others beheld a curious sight.
The tunnel they were in ended at a small hole which opened into a large
cavern, and, fortunately, this opening was concealed from the view of
those in the main place.

"The diamond makers!" whispered Tom, hoarsely, pointing to several men
grouped about