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——"
His musing broke off suddenly and he crouched forward watching intently. His eyes were staring wide-open and startled at the Wondership. Its bulk lay blackly against the faint, phosphorescent glow of the black barren.
Then he felt his scalp tighten and his mouth go dry while his heart seemed to stop for an instant and then pound furiously, shaking his frame.
For a second he had seen something that had almost startled him into a cry. A dark figure was creeping round the Wondership, crouched like an ape as it examined the craft.
The boy had hardly caught a glimpse of it before it vanished, gliding swiftly like an animal into the brush. Jack rubbed his eyes.
"Am I seeing things?" he asked himself, "but no, I'm positive, as sure as I stand here, that that was a human figure sneaking about down there. Who could it have been?"