"Come on!" And he swam on boldly and Merwell followed as quickly as he could.
Soon the pair reached a break in the cave. On either side were walls of rocks, uneven and covered with scanty bushes and immense trailing vines. The opening was about a hundred feet in length, and beyond it the stream of salty water plunged into another cavern, undoubtedly on its way to the ocean.
"Well, we are out of the cave in one way but not in another," observed Dave, as he stood on the dry rocks and gazed about. "It's going to be a stiff climb to get out of here."
"Ca-can't you wait till I—I get my breath," panted Merwell.
"Yes, for I want to get my own breath back. Perhaps we'll have to go through that next cave to get out," he continued, after a pause.
"Oh, I hope not! I hate it underground!" And Merwell shivered. "Besides, it's cold," he went on, to cover up the tremor in his voice.
"Yes, it is cold," returned Dave, shortly.
He sat down to rest, and Merwell followed suit. On all sides were the rocky walls and trailing vines, while at their feet ran the silent, mysterious stream of salty water.
Dave looked at the walls and the stream, and then looked at Merwell. The face of the other
