n back now," George proposed, in a short time,
seeing that they came no nearer to the boat in advance. "We left the
main gangway some time ago, and we ought not to get too far away from
it."

Will turned and looked back, facing only an inky blackness.

"We should have stuck to the main gangway," he said. "I don't even
remember when we left it! Is it very far back?"

"Some distance," answered George. "You see we followed this other boat
without thinking what we were doing."

"Perhaps, if we continue to follow the other boat, it will lead us
somewhere. The fellow rowing must know something about the interior of
the mine or he probably wouldn't be here!"

"I've been listening for a minute or more, trying to catch sound of the
fellow's oars," George went on, "but there's nothing doing. I guess he's
led us into a blind chamber and slipped away!"

"We don't seem to be lacking for excitement," Will suggested with a
grin. "We've lost Tommy and Sandy, and the machinery of the mine has
been interfered with, and the lower levels are filling with water! Any
old time we start out to do things, there's a general mixup!"

"Aw, quit growling and listen a minute," suggested George.

The boys listened only for a moment when the sound George had heard was
repeated. It was the call of the Wolf pack!

CHAPTER VI

THE BEAVER CALL

"That's Tommy!" exclaimed Will.

"I never knew that he belonged to the Wolf Patrol!" George observed.

"He might give the call without belonging to the Patrol!" urged Will.

The boys listened, but the sound was not repeated, although they called
out the names of their chums and gave the Beaver call repeatedly.

"I guess it was a dream," George suggested.

"Then it was the most vivid dream I ever had!" Will declared.

They rowed about the chamber for some moments searching for the source
of the call, but to no purpose.

"Let's go back to the shaft," urged George.

"I'm agreeable," answered Will. "The only question now is whether we can
find the shaft. The water is so deep that all branches of the mine look
alike to me!"

In passing out of the chamber into another passage the boys were obliged
to stoop low in order to avoid what is called a dip.

After passing under the dip so close to the ceiling that the boys were
obliged to lie down in the boat in order to protect their heads, they
came to a large chamber which seemed to be fairly dry save in the
center, where there was a depressi