"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.