lar
buildings, one within the other. Around the outer part were many
rooms, which had evidently formed the living apartments of the
priests. There were galleries, chambers, halls and assembly rooms.
Then the whole of the interior of the temple, under a great dome
that had mostly fallen in, consisted of a vast room, which was
probably where the worship went on. For, even without going farther
than to the edge of it, the youths could see stone altars, and many
strangely-carved figures and statues. Some had fallen over and lay
in ruins on the floor. The whole scene was one of desolation.

"Come on," invited Tom, "it's healthier and more pleasant outside.
Let's look for that tunnel."

But the lads soon realized that it was not going to be as easy to
locate this as they had hoped. They were looking for some sort of
slanting opening, going down into the earth--the entrance to the
underground city--but though they both made a complete circuit of
the temple, each at a varying distance from the outer walls, no
tunnel entrance showed.

"Breakfust! Breakfust!" called Eradicate, when Tom was about to
start on a second round.

"Let's eat," suggested Ned, "and then we four can circle around
together." Tom agreed that this would be a good plan. A little later
then, with Tom nearest the temple walls, the four began their march
around them.

Four times that morning they made the circuit, and the same number
in the afternoon, until they were nearly half a mile away from the
ruin, but no tunnel showed.

"Well, we'll have to keep at it to-morrow," suggested Tom. "It's too
soon to give up."

But the morrow brought no better success, nor did the following two
days. In fact for a week they kept up the search for the tunnel, but
did not come upon it, and they had now pretty well covered the big
plain. They found a few ruins of the ancient city of Poltec.

"Well, what about it?" asked Ned one night as they sat in the
balloon, talking it over. "What next, Tom?"

"We've got to keep at it, that's all. I think we'll go up in the
balloon, circle around over the plain at just a little elevation,
and maybe we can spot it that way."

"All right, I'm with you."

But they did not try that plan. For in the middle of the night Ned
suddenly awakened. Something had come to him in his sleep.

"Tom! Tom!" he cried. "I have it! What chumps we were!"

"What's the matter, old man?" asked Tom anxiously. "Are you sick--talking
in your sleep?"