m, Mr. Damon and the two contractors sat in the main office and
talked things over. Koku was eating supper, though the others had
finished, but, naturally, it took Koku twice as long as any one else.
Professor Bumper was busy transcribing material in his note-book.

"Well, I'm glad you've come back, Job," said his brother. "Things have
been going at sixes and sevens here since you went to get some new kind
of blasting powder. By the way, I hope you got it, for we are
practically at a standstill."

"Oh, I got it all right--some of Tom Swift's best--specially made for
us. And, better still, I've brought Tom back with me."

"So I see. Well, I'm glad he's here."

"Now what about this accident to-day?" went on Job.

"Well, as I said, it's the third this week. All of them seemed to be
premature blasts. But I've sent for some of the fuses used. I'm going
to get at the bottom of this. Here is Sullivan with them now. Come in,
Tim," he called, as the Irishman knocked at the door.

"Are they the fuses used in the blasts?" Walter asked.

"They are, sor. An' they mostly burn five minutes, which is plenty of
time fer all th' min t' git out of danger. Only this time th' fuse
didn't seem to burn more than a minute, an' I lit it meself."

"Let's see how long they burn now," suggested Job.

One of the longer fuses was lighted. It spluttered and smoked, while
the contractors timed it with their watches.

"Four minutes!" exclaimed Job. "That's queer, and they're the regular
ten minute length. I wonder what this means.

He took up another fuse, and examined it closely.

"Why!" he cried. "These aren't our fuses at all. They're another make,
and much more rapid in burning. No wonder you've been having premature
blasts. They go off in about half the time they should."

"I can't understhand thot!" said Tim, thoughtfully. "I keep all the
fuses locked up, and only take thim out when I need thim."

"Then somebody has been at your box, Tim, and they took out our regular
fuses and put in these quicker ones. It's a game to make trouble for us
among our men, and to damage the tunnel."

"Bless my rubber boots!" cried Mr. Damon. "Who would do a thing like
that?"

"Our rivals, perhaps, though I do not like to accuse any man on such
small evidence," said Walter. "But we must adopt new measures."

"And be very careful of the fuses," said Job.

"Thot's what I will!" declared Tim. "I'll put th' supply in a new
place. No wonder there was