"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 depression of considerable size.

"Nothing doing here!" Will exclaimed as he flashed his searchlight
around the place. "This chamber looks as if there hadn't been an
ounce of coal mined here for a hundred years."

"Then let's get out," George proposed, "and make our way back to the
shaft if possible. If we can't, we'll make noise enough to attract
Canfield's attention and let him come and lead us out."

"Here we go, then," cried Will, giving the boat a great push toward
the dip. "We can't get out any too fast."