"Bless my watch chain!" cried Mr. Damon. "What's that?"
"Obsidian is a volcanic rock—a sort of combination of glass and flint for hardness," Tom explained. "It is brittle, black in color, and the natives of the Admiralty Islands use it for tipping their spears with which they slay victims for their cannibalistic feasts."
"Bless my—bless my ear-drums!" gasped Mr. Damon. "Cannibals!"
"Obsidian was also used by the ancient Mexicans to make knives and daggers," Tom went on. "When Cortez conquered Mexico he found the priests cutting the hearts from their living victims with knives made from this volcanic glass-like rock, known as obsidian. It may be that your brother has met with a vein of that in the tunnel," Tom said to the contractor.
"Possibly," admitted Mr. Titus.
"In that case," Tom stated, "I may have to use a new kind of explosive. That used for my giant cannon would merely crumble the hard rock for a short distance."
"Then will you accept the contract, and help us out?" asked Mr. Titus eagerly. "We will pay you well. Will you come to Peru and look over the ground?"
"And kill two birds with one stone, and come with me also?" put in Mr. Damon.
Tom pondered for a moment. He was about to answer when the tunnel contractor, who was looking from the library window, suddenly jumped from his chair crying:
"There he is again! Once more dogging me!"