There was but one vessel in sight. She proved to be a tramp bound up-channel. There were no signs of the light cruiser Spanker.
Even as he looked, came another faint report.
The man, by reason of long experience, knew that it was not a quick-firer. The interval was too great for that. The unusual pitch of the whine of the projectile puzzled him.
Suddenly a long, low-lying dark object appeared in the field of the high-powered telescope.
"Gosh!" ejaculated the bluejacket, "s'elp me if she ain't a perishin' submarine."
Even as he looked, he saw a long, slender object rise from the for'ard deck of the distant vessel. Slowly but unhesitatingly it moved until the watcher found himself gazing down the muzzle of a gun. Instinctively he shut his eyes, forgetting that a distance of about fifteen miles separated him from that menacing ring of metal.
When he looked again, the gun had been trained to an elevation of nearly forty-five degrees. There was a flash... thirty seconds later he heard the report.
Twice more the gun was discharged; then the mysterious vessel submerged.
The spell was broken as far as the signalman was concerned. Clamping the telescope, so that it remained trained upon the spot where he had seen the submarine disappear, he shouted to his mate, who was leisurely bending the hoist of flags to the signal halliards.
"Belay there," he exclaimed excitedly. "Get on the telephone to the C.-in-C. There's a bloomin' submarine been shellin' Pompey."