Dan thought suddenly of a reply. He rushed into the charthouse, to return in a moment with a lighted lantern and a copy of the Nautical Almanac which would serve to hide the flame between flashes. He flashed an answer.
Again the pale light flickered from the dark mass of land, spelling words out rather slowly, as if the sender were uncertain in his knowledge of Morse. Surprised as Dan had been by the signal from an island marked on the charts as uninhabited, he was astonished at the message that now came to him.
"You are in terrible danger," he read in the flashes. "Dreadful thing here. Hurry away. Radio for warships. I am—"
The winking light suddenly went out. Dan strained his eyes to watch the point where it had been, and a few seconds later he saw a curious thing. A darting, stabbing lance of green fire flashed out across the barren, rocky cliff, lighting it fleetingly with pale green radiance. It leapt out and was gone in an instant, leaving the shoulder of the island dark as before.
Dan watched for long minutes, but he saw nothing more brilliant than the pale gleam of phosphorescence where the waves dashed against the sheer granite wall of the island.
"What you t'ank?" Larsen broke in upon him.
an started, then answered slowly. "I don't know. First I thought there must be a lunatic at large. But that green light! I didn't like it."
He stared again at the looming mass of the island. Davis Island is one of the innumerable tiny islets that dot the South Pacific; merely the summit of a dead volcano, projecting above the sea. Nominally claimed by Great Britain, it is marked on the charts as uninhabited.