shaft," Sandy said, after the boys
had walked for nearly half an hour on the backward track.

"Pull on your string," suggested Tommy, "and see if it stiffens up like
only a short length of it remained out."

Sandy did as requested, and then dropped to the floor with his
searchlight laid along the extension of the cord.

"The other end is loose!" he said in a tone of alarm.

"Loose?" echoed Tommy. "How did it ever get loose?"

Sandy sat down on the floor of the passage and began drawing the cord
in, hand over hand.

"I'm going to see if it's been cut!" he said.

Tommy stepped on the swiftly moving cord and held it fast to the floor.

"You mustn't draw it in!" he exclaimed. "As long as it lies on the floor
as we strung it out, we can follow it without taking any chances. If you
pull it in, then it's all off."

"I understand!" Sandy agreed. "I didn't pull much of it in."

The boys started up the gangway, one of them keeping a searchlight on
the white thread of cord.

They seemed to make a great many turns and once or twice Sandy declared
that they were walking round and round in a circle.

"I don't believe the passages run so we could walk around in a circle!"
argued Tommy. "That ain't the way they run passages in mines!"

"I don't care!" Sandy insisted. "We've been turning to the left about
all the time, and if you leave it to me, we'll presently come out in the
chamber where we heard the call of the pack!"

"That may be right," admitted Tommy. "It does seem as if we'd been
turning to the left most of the time. Besides," he went on, "we've been
walking long enough to have reached the shaft three or four times."

"And yet," argued Sandy, "we've been following the line of the cord
every step. It lies right in the middle of the gangway here, and we're
going the way it points all the time."

This bit of reasoning seemed to give the boys fresh courage, and they
walked on, expecting every moment to come in sight of the frame work
which surrounded the shaft. At length, after a long half hour, Tommy
stumbled over an obstruction lying in a chamber which somehow seemed
strangely familiar. He lifted his foot and gave the obstruction a hearty
kick.

"That's my Indian sign of the trail!" grunted Sandy.

"For the love of Mike!" exclaimed Tommy. "Have we been traveling all
this time to come out in this same old hole at last?"

"That's what we have!" replied Sandy. "If we had paid no attention to
the string whateve