The Sub made his way to the after-end of the raised platform, where the petty officer was standing as rigidly as a statue.
"All right there, Chalmers?"
"All right, sir," replied the imperturbable petty officer. "Only that blessed log's gone to blazes."
He held up a coiled length of log-line as a visible corroboration to his statement. The cause of the explosion was now revealed. In turning, R19 had passed perilously close to an anchored mine, while the log, towing astern, described a wider arc than that of the submarine, and also caused a reduction of speed of the revolving metal cylinder. The depth to which the log sinks varies inversely with the speed of the towing vessel. So in "cutting the corner" the trailing log descended sufficiently to come in contact with one of the horns of the submerged mine.
It was a blessing in disguise, for the explosion gave the Hon. Derek a clue as to his position, and a slight alteration of helm was sufficient to bring R19 approximately in the centre of the channel. Owing to the fog, none of the hostile patrol-boats risked making a dash between the mines, although away to the south'ard there were audible evidences of activity.
Another hour passed; then, with a partial lifting of the fog, the loom of the land could be discerned on either hand.
"White and red group flashes on the starboard beam, sir," reported the look-out, then: "Red and green occulting flashes on port bow, sir."
Raising his night-glasses, the Hon. Derek focused them first to starboard and then to port. Then he turned to the Sub.
"We're through, Mr. Fordyce," he remarked. "Those are the Malmo lights to starboard. Telegraph for full speed ahead, if you please. Good-bye to the Baltic!"