y. "If you don't get out of there in
about a second, the rats'll eat your legs off!"

Without waiting for the boys to assume the offensive, the rats began
screaming and springing at their feet.

The three boys on the outside of the barrier, understanding the peril
their friends were in, crawled up to the top of the wall of refuse which
shut the boys into the chamber and turned their lights inside.

It seemed to them then that the rats were two or three deep on the
floor. There appeared to be hundreds--thousands of them. They circled
around the boys, becoming bolder every moment. They nipped at the rubber
boots and left the marks of their teeth on the tough uppers.

"Now, boys," Tommy yelled, as they drew their automatics and leveled
them over the wall, "shoot to kill! This is no Sunday School picnic! And
while we're shooting, boys, you back up to this wall, and see if you
can't work your way to the top. If you can get up here, we can manage to
displace enough slate to let you through."

The boys fired volley after volley, but the rats came on viciously.

CHAPTER XV

STICK OF DYNAMITE

By this time Jimmie and Dick had their automatics out and were firing
into the horde of rats. They killed the rodents by the score, yet for
every one slaughtered a dozen seemed to appear.

Presently the chamber became so full of powder smoke, the air so
stifling, that the lads were obliged to cease firing.

"Work your way up this wall," Tommy cried out to the lads as he heard
them panting below. "Work your way up so we can catch hold of you, and
you'll soon be out of that mess!"

"There's a dozen rats hanging to my boots!" cried Dick.

"And mine, too!" declared Jimmie.

The three boys on the outside continued to hurl refuse from the top of
the wall into the chamber. This in a measure kept the rats back, and
before many minutes Jimmie and Dick were drawn to the top of the
barrier.

Their rubber boots were cut in scores of places by the sharp teeth of
the rats, and even their clothing as high up as their shoulders showed
ragged tears. A dozen or more rats hung to the boys' boots until the top
was reached, then they dropped back screaming with baffled rage.

"Talk about your wild Indians!" exclaimed Tommy. "I never saw anything
as vicious as that was! I told you boys not to open up an argument with
those fellows! Mine rats are noted for their courage when attacked."

"How many bites did you get?" asked Elmer anxious