“Spiked your guns, Mister Jarrold,” he laughed, as the signaling continued. Plainly on the other ship they could not understand why they no longer got flashed replies from Jarrold’s room.

“Oh, I’ll bet the air is blue below,” chuckled Jack, delighted at the success of his plan. “Now I’ll just watch till they get sick of waiting for Mr. Jarrold, and then go below and put that switch on again.”

For half an hour the vain red flashes came out of the night and then they ceased.

“I guess they’ve sneaked off for fear daylight would discover them,” said Jack. “Now to switch the light on again, and then for a snooze. I think I’ve earned it.”

[CHAPTER XVI—S. O. S.]

Dawn showed a smudge of black smoke on the far horizon which might or might not have been the mysterious visitant of the night. At any rate, by noon something occurred which quite put out of Jack’s mind, and those of the ship’s officers, who were considerably exercised over the midnight signals, all thoughts of the secretive craft.

To Jack, seated at his instruments, there had suddenly come a sharp call:

“S.O.S.—S.O.S.—S.O.S.”

Coming as it did, like a bolt from the blue, the urgent call thrilled the young operator. He galvanized into action instantly and sent Sam scurrying to the bridge with word that the most urgent call that can assail a wireless man’s ears had just come to him.

It was faint and far away, but that very fact made it evident to Jack’s experienced mind that whoever was sending the message, was in dire straits and running out of current.