"I can telegraph to have some sent here to you," said Mr.
Titus eagerly. "Meantime, here is a description of it. I can
read you that"; and, taking a letter from his pocket, he
read to Tom a geological description of the hard rock.

"Hum! Yes," mused Tom, as he listened. "It seems to be of
the nature of obsidian."

"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