there sounded throughout the underground city, a dull, booming noise, like distant thunder.
"What's that?" cried Ned.
"Bless my bath sponge!" exclaimed Mr. Damon, "I hope the water isn't rising in the river."
"Oh land a massy!" gasped Eradicate.
Without a word Tom dropped the golden head and made for the street that led to the tunnel. The others followed, and soon caught up to the young inventor. On and on they ran, with only the light of their electric flash torches to guide them. Suddenly Tom stopped.
"Go on!" cried Ned. "See what's happened! Go on!" .
"I can't," answered Tom, and they all wondered at his voice. "There's a big block of stone across the tunnel, and I can't go another step. The stone gate has fallen. We're trapped here in the underground city of gold!"
"Bless my soul! The tunnel closed?" cried Mr. Damon.
"Look," said Tom simply and in hopeless tones, as he flashed his light. And there, completely filling the tunnel, was a great block of stone, fitting from ceiling to floor and from side wall to side wall, completely cutting off all escape.
"Trapped!" gasped Ned. "The Mexicans or Andy Foger did this."
