d the mouth of the cave
where we first entered."

"It's a chance worth taking," said Mr. Damon. "Of course it is a
chance. But then everything connected with this expedition is; so one
is no worse than another. As you say, we may find the entombed men
more easily this way than any other."

"I wonder," said Tom slowly, "if, by any chance, we shall find, through
this passage, the lost city we are looking for."

"And the idol of gold," added Ned.

"Goosal, do you know anything about this?" asked Professor Bumper.
"Did you ever hear of another passage leading to the cave where you saw
the ancient city?"

"No, Learned One, though I have heard stories about there being many
cities, or parts of a big one, beneath the mountain, and when it was
above ground there were many entrances to it."

"That settles it!" cried the professor in English, having talked to
Goosal in Spanish. "We'll try this and see where it leads."

They entered the stone-lined passage. In spite of the fact that it had
probably been buried and concealed from light and air for centuries, as
evidenced by the growth of the giant trees above it, the air was fresh.

"And this is one reason," said Tom, in commenting on this fact, "why I
believe it leads to some vast cavern which is connected in some fashion
with the outer air. Well, perhaps we shall soon make a discovery."

Eagerly and anxiously the little party pressed forward by the light of
the pocket electric lamps. They were obsessed by two thoughts--what
they might find and the necessity for aiding in the rescue of their
rivals.

On and on they went, the darkness illuminated only by the torches they
carried. But they noticed that the air was still fresh, and that a
gentle wind blew toward them. The passage was undoubtedly artificial,
a tunnel made by the hands of men now long crumbled into dust. It had
a slightly upward slope, and this, Professor Bumper said, indicated
that it was bored upward and perhaps into the very heart of the
mountain somewhere in the interior of which was the Beecher party.

Just how far they went they did not know, but it must have been more
than two miles. Yet they did not tire, for the way was smooth.

Suddenly Tom, who, with Professor Bumper, was in the lead, uttered a
cry, as he held his torch above his head and flashed it about in a
circle.

"We're blocked!" he exclaimed. "We're up against a stone wall!"

It was but too true. Confronting them, and ext