And so it was arranged.  Leaving the Wondership on the edge of the clearing, they made camp on the flat ledge of sandy soil interspersed with rocks that Jack had selected.  From it they had a good view in both directions.  Above them was a small island, and below them the river leaped and roared in a series of big rapids.

Their preparations for camping occupied all the afternoon.  It was supper time when they had finished and everything was shipshape and comfortable.  In the meantime Dick had wandered off with the rifle and returned with four good-sized rabbits and three squirrels which Zeb cooked into a savory stew.

They turned in early as they had all worked hard and were tired.  Just what time it was that he awakened, Jack did not know.  But he thought it was after midnight.  Taking his watch he went to the door of the tent to look at it in the moonlight, as he did not wish to arouse the others by striking a light.

The moon flooded the island.  Jack looked about him, enjoying the beauty of the scene.  The cliffs were great masses of black and white and the rushing river gleamed like silver.  He glanced toward the black waste, on the edge of which they left the Wondership.  The next instant he uttered a startled exclamation.  Above the bare patch of dark-colored earth tall white figures were dancing, gleaming in the moonlight.

Jack’s heart gave a bound and he caught his breath for an instant.  Then he felt inclined to laugh at his own fears.  What he had taken for ghostly figures were columns of vapor writhing and twisting as they steamed upward from the bare end of the island.  What caused them, Jack did not know.  He noticed, too, that the whole patch of barren land glowed with a strange phosphorescence like rotted wood.

Fascinated by the spectacle, he stood gazing at it.  There was something eerie about the dancing, pirouetting columns of vapor.  They looked like a party of ghosts dancing a quadrille.  They twisted and contorted and bowed and soared upward and sank again in a kind of rhythm.

“Gracious, this is a spooky sort of place,” thought Jack.  “I wonder what causes those wavering columns?  Maybe some sort of hidden hot springs like the one the professor fell into.  I know one thing, I don’t like this island overmuch.  As Zeb said, there is something queer about it—­something in the air.  I don’t know what, but I for one won’t be sorry when we leave it.”

He fell to musing about his father waiting so many miles away for news of the discovery that was to rehabilitate his fortunes and place the radio telephone in the list of practical inventions that have created an epoch in the world’s history.

“Poor old dad,” he thought “After all, he’s really having the most trying part of this thing.  Waiting back there for he doesn’t know what, and with nothing to do but wait.  I wonder if we are going to succeed?  We will, we must!  But, supposing that the map was wrong and that——­”