des were sent headlong to the rocks,
some of them receiving bumps that would prove more or less painful later
on.

There was no mystery about the matter, because accompanying their upset
had come a loud explosion that sounded doubly severe to them, since they
were underground.

Plainly the conspirators had looked far enough ahead to make ready to
entomb any prowling visitors who might succeed in gaining access to the
mine, and learn something of its secrets. They had a charge of blasting
powder, or possibly a dynamite cartridge, placed so that it could be
fired with ease.

"Wow!" exclaimed Jimmy, struggling half erect, "who hit me with that
brick?"

"What happened, Ned?" asked Teddy, almost dazed from the way his head
had collided with a hard rock, causing him to see about a million
flashing stars in that one second of time.

"They've fired some sort of explosive, to seal up the exit of the mine!"
broke from Jack, who was quick to guess the appalling truth.

"Then we're shut up here like rats in a trap, is that it?" persisted
Jimmy, now so astonished that he even forgot to rub the back of his head
where the seat of the pain seemed to be located.

"I don't know," said Ned, "but we can soon settle that by pushing on."

"What if another bomb lets go?" Teddy inquired.

"Small danger of that happening," the leader assured him; "but anyhow
we'll have to take the chances. Come along, everybody!"

That was Ned's way of doing things, and proved him to be the right type
of leader, capable of winning the respect of his patrol. Seldom had any
of the scouts heard him tell them to "go on" when there was a spice of
peril in the air.

They were not long in finding out the dismal truth. Indeed, as they
advanced along the tortuous passage, the air became more and more foul
with the odor of burnt powder. And, finally, the light from the several
electric hand-torches disclosed the presence ahead of a mass of fallen
rock and dirt that effectually filled the narrow passage.

The boys stared at the barrier in more or less dismay. It effectually
cut them off from making their exit, and so far as they knew there was
no other means of leaving the mine.

Jimmy started in to lifting several of the rocks and tossing them aside.
With his customary zeal, he fancied that if they all got to work they
might in a short time bore through the barrier.

"Be careful there!" warned Jack, as the action of the "busy bee"
dislodged several othe