k here," Will continued, as the boat bumped into a pyramid of
shale which had been thrown up to within a few inches of the roof, "some
one has been building this hill of refuse and using it for a refuge!"

"It does look that way," George agreed. "That shows that at some time
the water must have ascended to the very top of the wall. We may have to
climb up there ourselves in order to keep from getting our clothing
soaked in that ink down there!"

The water rose higher and higher in the passage, and it seemed to the
boys that by this time most of the lower gangways were entirely
impassible.

"It doesn't seem to me that the water in this blooming old mine could
rise any faster if the whole Mississippi river were turned into it!"
cried George in a tone of disgust. "If Canfield doesn't get his pumps
going before long, he'll have a job here that'll take him all winter!"

"I presume he's doing the best he can," Will argued. "For all we know,
the boilers as well as the electric motors may have been tampered with.
That would be just our luck!"

"I wonder what's become of that bum detective?" asked George after a
short silence. "We heard him rowing along in front of us one minute, and
the next minute there wasn't a single sound to indicate that there was
another boat in the mine."

"As soon as I get out of this," Will stated, "I'm going to make it my
business to find out whether that detective is regularly employed on
this case. He looks to me like a crook!"

It was dreary waiting there in the sealed-up chamber, and the boys found
themselves dropping into long intervals of silence while they listened
for the gurgle of the water which would indicate that the great pumps
had been set in motion.

During one of those intervals of silence, they heard sounds which
brought them to their feet in great excitement. Almost unable to believe
his ears, Will turned to George with a question on his lips:

"Did you hear that?" he asked.

"Of course I did!"

"I did, too, but I thought I must be dreaming."

"No dream about that!" replied George. "That's the call of the Beaver
Patrol!"

"And that means that Tommy and Sandy are not far away!"

"We heard the call of the Wolf Patrol not long ago," suggested George.
"I wonder if this blooming old mine is chock full of Boy Scouts of
assorted sizes. There can't be too many here to please me!"

The boys returned the Beaver call but no answer came. At times they
thought they heard whispe