s mass was as
large as a house.

"Look at the hole left when the roots pulled out!" cried Ned. "Why,
it's like the crater of a small volcano!" he added. And, as they stood
on the edge of it looking curiously at the hole made, the others agreed
with Tom's chum.

Professor Bumper was looking about, trying to ascertain if there were
any evidences of the earthquake in the vicinity, when Tom, who had
cautiously gone a little way down into the excavation caused by the
fallen trees, uttered a cry of surprise.

"Look!" he shouted. "Isn't that some sort of tunnel or underground
passage?" and he pointed to a square opening, perhaps seven feet high
and nearly as broad, which extended, no one knew where, downward and
onward from the side of the hole made by the uprooting of the trees.

"It's an underground passage all right," said Professor Bumper eagerly;
"and not a natural one, either. That was fashioned by the hand of man,
if I am any judge. It seems to go right under the mountain, too.
Friends, we must explore this! It may be of the utmost importance!
Come, we have our electric torches, and we shall need them, for it's
very dark in there," and he peered into the passage in front of which
they all stood now. It seemed to have been tunneled through the earth,
the sides being lined by either slabs of stone, or walls made by a sort
of concrete.

"But what about the rescue work?" asked Mr. Damon.

"I am not forgetting Professor Beecher and his friends," answered the
scientist.

"Perhaps this may be a better means of rescuing them than by digging
them out, which will take a week at least," observed Tom.

"This a better way?" asked Ned, pointing to the tunnel.

"That's it," confirmed the savant. "If you will notice it extends back
in the direction of the cave from which we were driven. Now if there
is a buried city beneath all this jungle, this mountain of earth and
stones, the accumulation of centuries, it is probably on the bottom of
some vast cavern. It is my opinion that we were only in one end of
that cavern, and this may be the entrance to another end of it."

"Then," asked Mr. Damon, "do you mean that we can enter here, get into
the cave that contains the buried city, or part of it, and find there
Beecher and his friends?"

"That's it. It is possible, and if we could it would save an immense
lot of work, and probably be a surer way to save their lives than by
digging a tunnel through the landslide to fin