Throughout the day U 247 had been feeling her way through fog of varying intensity by aid of compass, lead line, and patent log. Whenever the thud of the engines of an approaching vessel was heard the U-boat submerged promptly and without ceremony. Although five out of every six vessels that passed within audible distance were of the British Mercantile Marine, U 247 made no effort to ascertain that they were not warships. The risk of closing with any craft in the fog was too great, for, although the U-boat could shell an unarmed merchantman with impunity, she had long learnt to respect both men-of-war and armed merchant ships. Von Preugfeld had vivid recollections of the s.s. _Contraption_, a six-knot tramp two hours out of Grimsby. He had had information from an unimpeachable source that the _Contraption_ was unarmed, that she carried munitions for Archangel, and that she expected to join a convoy off Flamborough Head. With these facts in his possession, the ober-leutnant showed far less discretion than he usually exercised. Unable to resist a chance of playing upon the nerves of the crew of the English ship, he brought U 247 to the surface, and at reduced speed maintained a position a bare cable's length from the tramp's starboard bow. Therein he made a great mistake. He had completely underrated the stubborn courage of the British Mercantile Marine. Hard-a-port went the _Contraption's_ helm. Barely had the crew of the U-boat time to scurry below and submerge at record speed when the tramp's forefoot rasped athwart the U-boat's deck. It was a near thing, as the moisture on von Preugfeld's ashen-grey features testified. Twenty minutes later U 247 rose to the surface, and at a safe distance shelled her antagonist and sent her to the bottom; but the U-boat had to "leg it" back to Wilhelmshaven with her pumps going continuously to keep down the water that oozed through ominous dents in her hull. "Ten metres, Herr Kapitan." "Any signs of the lighthouse?" he demanded. "None, Herr Kapitan." "Keep her at that," continued the ober-leutnant. "Inform me when you strike eight metres, unless you sight the headland before that." Running just awash, and with her surface motors well throttled down, U 247 held on until the look-out man gave the much desired information: "Land right ahead, Herr Kapitan. A white lighthouse two points on our starboard bow." It was now close on sunset. A partial lifting of the fog revealed at a distance of about a mile a serrated ridge of dark cliffs culminating in a bold promontory crowned by the massive squat tower of a lighthouse. There was no need for von Preugfeld to verify the statement by means of his reflex glasses. He rapped out a curt order, and the U-boat swung round through eight points of the compass and settled down to a course south-south-west, or parallel with the forbidding shore.