gas, and they call it a blower because it blows up out of
crevices in the coal and in the rocks."

"If I should light a match, would it set it on fire?" asked Tommy.

"I wouldn't like to have you try it!"

The boys continued on their way for some moments, and then Tommy stopped
and extinguished his light, whispering to Sandy to do the same.

"What's that for?" demanded the latter.

"Didn't you hear that noise behind the cribbing?" asked Tommy.

"Rats, probably!"

"Rats nothing!" replied Tommy. "Rats don't make sounds like people
whispering, do they? Keep still a minute, and we'll find out what it
is!"

"You'll be seeing a light next!" Sandy suggested.

"I see it now!" answered Tommy.

Sandy saw it, too, in a moment. It seemed at first to be floating in the
air at the very top of the gangway. It moved from side to side, and
finally dropped down nearer to the floor. There seemed to be no one near
it or under it. Its small circle of illumination showed only the empty
air.

"What do you make of it?" asked Tommy.

"Is this Tunnel Six?" asked his chum.

"I don't know! If it is, we've seen the light the caretaker referred to.
We'll have a great story to tell in the morning!"

The boys stood in the darkness of the gangway watching the light for
what seemed to them to be a long time. Now the light advanced toward
them, now it receded. Now it lifted to the roof of the gangway, now it
dropped almost to the floor.

At intervals, the noises behind the cribbing to which Tommy had referred
were repeated, and the boys at last moved over so as to stand with their
ears almost against the wooden walls.

"There is some one behind the cribbing, all right!" Tommy declared. "I
hear some one breathing."

"Aw, keep still!" whispered Sandy. "If there is anyone there, you'll
frighten them away! I thought I heard some one myself!"

"I'll tell you what I think," Tommy suggested in a moment, "and that is
that either Will and George, or both of them, beat us to this gangway.
They are hiding behind there on purpose to give us a scare."

"That's a dream!" replied Sandy. "We left them both asleep."

"Dream, is it?" repeated Tommy scornfully. "You just listen to the sound
that comes from behind this cribbing, and tell me what you make of it!"

Both boys listened intently for a moment, and then Sandy switched on his
light and moved swiftly along the cribbing as if in search of an
opening. Tommy gazed at him in astonishment.

"