“Let’s call to him,” eagerly suggested the professor. Then he lifted his voice and called loudly.
When he had repeated the cry three times, they listened.
“Didn’t you hear a distant answer?” asked Dick.
“I judge whatever we heard was an echo,” said Brad.
After a time they lifted their voices in a united shout, and then listened to the mocking echoes which fled from pillar to pillar and died in the unknown distance.
“No use!” moaned Professor Gunn. “I am satisfied that we are doomed! We’ll never leave this place alive, and our fate will forever remain a mystery!”
“I’m sure that was no echo!” exclaimed Dick, as far away in the darkness they seemed to hear an answer to their repeated shouts. “Be still and let me shout.”
When he had lifted his strong, clear voice all hushed their breathing and listened.
There was a short interval, and then out of the black distance came a faint, far-away answer.
“Some one did shout, pard!” exclaimed the Texan. “It’s a dead-sure thing!”