who was searching as eagerly as the others, went back
a little, flashing his lamp on every square of stone. Suddenly he
uttered a cry.

"Look yeah, Massa Tom! Heah's suffin' dat looks laik a big door
knob. Maybe yo' kin push it or pull it."

They rushed to where he was standing in front of a niche similar to
the one where he had found the golden image. Sunken in the wall was
a round black stone. For a moment Tom looked at it, and then he said
solemnly:

"Well, here goes. It may shut off the water, or it may make it rise
higher and drown us all, or the whole tunnel may cave in, but I'm
going to risk it. Hold hard, everybody!"

Slowly Tom put forth his hand and pushed the knob of stone. It did
not move. Then he pulled it. The result was the same--nothing.

"Guess it doesn't work any more," he said in a low tone.

"Twist it!" cried Ned. "Twist it like a door knob."

In a flash Tom did so. For a moment no result was apparent, then,
from somewhere far off, there sounded a low rumble, above the roar
of the black stream.

"Something happened!" cried Mr. Damon.

"Back to the river!" shouted Tom, for they were some distance away
from it now. "If it's rising we may have a chance to escape."

They hurried to the edge of the stone channel, and Ned uttered a cry
of delight.

"It's going down!" he yelled, capering about. "Now we can go on!"

And, surely enough, the river was falling rapidly. It no longer
roared, and it was flowing more slowly.

"The water is shut off," remarked Tom.

"Yes, and see, there are steps which lead across the channel," spoke
Ned, pointing to them as the receding water revealed them.
"Everything is coming our way now."

In a short time the water was all out of the channel, and they could
see that it was about twenty feet deep. Truly it would have been a
formidable stream to attempt to swim over, but now it had completely
vanished, merely a few little pools of water remaining in
depressions on the bottom of the channel. There were steps leading
down to the bottom, and other steps ascending on the other side,
showing that the river was used as a barrier to further progress
along the tunnel.

"Forward!" cried Tom gaily, and they went on.

They went down into the river channel, taking care not to slip on
the wet steps, and a few seconds later they had again ascended to
the tunnel, pressing eagerly on.

Straight and true the tunnel ran through the darkness, the only
illumination being the