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.

Chapter XIII

Tom's Explosive

"Something has happened!" cried Mr. Titus as he ran forward, followed
by Tom, Mr. Damon and Koku. Professor Bumper started with them, but on
the way he saw a curious bit of rock which he stopped to pick up and
examine.

At the entrance of the tunnel, from which came rushing dirt-stained and
powder-blackened men, Mr. Titus was met by a man who seemed to be in
authority.

"Hello, Job!" he cried. "Glad you're back. We're in trouble!"

"What's the matter?" was the question. "This is my brother Walter," he
said. "This is Tom Swift and Mr. Damon," thus hurriedly he introduced
them. "What happened, Walter?"

"Premature blast. Third one this week. Somebody is working against us!"

"Never mind that now," cried Job Titus. "We must see to the poor
fellows who are hurt." "I guess there aren't many," his brother said.
"They were on their way out when the charge went off. Some more of
Blakeson & Grinder's work, I'll wager!"

They were rushing in to the smoke-filled tunnel now, followed by Tom,
Mr. Damon and Koku, who would follow his young master anywhere. Tom saw
that the tunnel was lighted with incandescent lamps, suspended here and
there from the rocky roof or sides. The electric lights were supplied
with current from a dynamo run by a gasoline engine.

"Where is it, Serato? Where was the blast?" asked Walter Titus, of a
tall Indian, who seemed to be in some authority.

"Back at second turn," was the answer, in fairly good English. "I go
get beds."

"He means stretchers," translated Job. "That's our Peruvian foreman. A
good fellow, but easily scared."

They ran on into the tunnel, Tom and Mr. Damon noticing that a small
narrow-gage railroad was laid on the fl