"The tunnel entrance!" cried Ned. "That's what it is! You've found it, Tom! The entrance to the city of gold at last!"
Chapter XIX The Underground River
They gathered around the opening so unexpectedly disclosed to them, and stared down into the black depths. Beyond the first few steps of the flight that led to they knew not where, nothing could be seen. In his impatience Tom was about to go down.
"Bless my match box!" cried Mr. Damon. "What are you going to do, Tom, my boy?"
"Go down there, of course! What else? I want to get to the underground city."
"Don't!" quickly advised the odd man. "You don't know what's there. It may be a trap, where the old Aztecs used to throw their victims. There may be worse things than bats there. You'll need torches--lights--and you'd better wait until the air clears. It may have been centuries since that place was opened."
"I believe that's right," agreed Ned. "Whew; Smell it! It's as musty as time!"
An unpleasant odor came up the tunnel entrance, and it was stifling to stand too close. Tom lighted a match and threw it down. Almost instantly the flame was snuffed out.
"We couldn't live down there a minute," said the young inventor. "We've got to wait for it to clear. We'll go back to the balloon and get some electric flash lamps. I brought along a lot of 'em, with extra strong batteries. I thought we'd need some if we did find the city of gold, and it looks as if we were almost there now."