the balloon.

"Bless my looking glass!" cried Mr. Damon.

A second later the noise suddenly increased, and something black,
accompanied by a noise of rapidly beating wings rushed from one of
the immense doorways.

"Bats!" cried Tom. "Thousands of bats! I'm glad we didn't go in
after dark!" And bats they were, that had made the noise as they
rushed out on their nightly flight.

"Ugh!" shuddered Mr. Damon. "I detest the creatures! Let's get under
cover."

"Yes," agreed Tom, "we'll have supper, turn in, and be up early to
look for the tunnel. We're here at last. I'll dream of gold to-night."

Eradicate soon had a meal in preparation, though he stopped every
now and then to peer out at the bats, that still came in unbroken
flight from the old temple. Truly there must have been many
thousands of them.

Whether Tom dreamed of gold that night he did not say, but he was
the first one up in the morning, and Ned saw him hurrying over the
sands toward the temple.

"Hold on, Tom!" his chum called as he hastened to dress. "Where you
going?"

"To have a hunt for that tunnel before breakfast. I don't want to
lose any time. No telling when Delazes and his crowd may be after
us. And the Fogers, too, may strike our trail. Come on, we'll get
busy."

"Where do you think the tunnel will be?" asked Ned, when he had
caught up to Tom.

"Well, according to all that Mr. Illingway could tell us, it was
somewhere near this temple. We'll make a circle of it, and if we
don't come across it then we'll make another, and so on, increasing
the size of the circles each time, until we find what we're looking
for."

"Let's have a look inside the temple first," suggested Ned. "It must
have been a magnificent place when it was new, and with the
processions of people and priests in their golden robes."

"You ought to have been an Aztec," suggested Tom, as he headed for
one of the big doorways.

They found the interior of the temple almost as badly in ruins as
was the outside. In many places the roof had fallen in, the side
walls contained many gaping holes, and the stone floor was broken
away in many places, showing yawning, black caverns below. They saw
hundreds of bats clinging to projections, but the ugly creatures
were silent in sleep now.

"Bur-r-r-r-r!" murmured Ned. "I shouldn't like any of 'em to fall on
me."

"No, it's not a very nice place to go in," agreed Tom.

They saw that the temple consisted of two parts, or two circu