Then, in the face of the cliff there showed something black—like a blot of ink, though more regular in outline.
"The mouth of the tunnel," said Mr. Titus to Tom. "Come on over to the office and I'll introduce you to my brother. I guess he will be glad we've arrived."
Tom dismounted from his mule, an example followed by the others. Professor Bumper gazed up at the great mountains and murmured:
"I wonder if the lost city of Pelone lies among them?"
Suddenly the silence of the evening was broken by a dull, rumbling sound.
"Bless my court plaster!" cried Mr. Damon. "What's that?"
"A blast," answered Mr. Titus. "But I never knew them to set off one so late before. I hope nothing is wrong!"
And, as he spoke, panic-stricken men began running out of the mouth of the tunnel, while those outside hastened toward them, shouting and calling.