But it was one of their own choosing, in an endeavor to solve the mystery, though as Bud and his companions watched the waters creeping higher and higher up the surface of the rock on which they stood, their hearts were not altogether easy.
"Suppose it covers the rock?" asked Dick.
"Then we'll have to swim back where Nort is," Bud answered.
"Shucks! You won't have to do nothin' of the sort!" declared Old Billee stoutly. "She won't come up any farther than it did before!"
And he was right. When the water around the rock lapped the erosion mark, which had been worn in the hard stone by centuries of the flow of the fluid, the flood ceased. The roaring, bubbling and seething, like that which takes place in a canal lock, came to an end, and the water of the pool became quiet.
"There! What'd I tell you?" cried Old Billee. "I closed th' water gate, that Bud opened to let th' water out, an' she come back. Now all we have t' do, so we can walk back, is t' yank this lever again."
"Does it only work two ways?" asked Yellin' Kid, his voice again softened, as the mystery of the place seemed to cast a shadow over him and the others.
"Seems to," Bud answered, holding his lantern down close to where the copper handle entered the rock.
There appeared to be a slot cut in the hard stone—a slot about three inches wide, and a foot long, in which the copper lever could be moved backward and forward, but not from side to side.
"Let's try the other way, now," suggested Dick.