The submarine was a J boat, and her station was at the western end of the North Dogger Bank-Heligoland swept channel. The weather had been rough and wet for the first four days of her patrol, reducing the periscope visibility to a few hundred yards' range across grey and foaming seas. The boat had patrolled at twenty feet depth (which is shallow for a big boat) in order to see anything at all, and because of the steep seas she had kept always beam to them, except for the turns at the end of her ten-mile beat. Each turn had caused her to either break surface or slip down to eighty feet, owing to the quick inclinations given her as the waves met her end-on. The weather cleared suddenly on the fourth night, and next morning she dived at dawn, under a gentle swell that hourly died down to a calm deep blue ocean. The visibility was good--how good her captain had hardly realised until through his high-power periscope he picked up the unmistakable line of brown blurs to the east that meant an approaching enemy squadron at a range of at least ten miles. He turned and dived at half-speed towards them, calling his crew to "action stations" at once. He knew that his orders forbade him to fire, but there was always the chance of his having to use his torpedoes in self-defence--self-defence, that is, of a legitimate kind, not of the type said to be used in certain districts where only mad elephants are allowed to be killed, but where all the elephants are said to became indubitably mad "after the first shot." As the smoke-blurs grew he eased speed to "dead slow"; the enemy was shown by the rate of change of his bearings to be steering a course which would take him past the J boat at easy range. The periscope slid along very slowly, only about a foot of its length showing above water; the captain knew that he could see Zeppelins if they were about, but an aeroplane, especially against the sun, is a different proposition, and he did not want to risk being observed before his wireless had done its work. Twenty minutes from sighting the smoke he turned to east to pass parallel to the enemy, and he moved slowly past their line. Looking closely at them with the high-power instrument, and with his periscope top now a bold three feet above the surface, he spoke rapidly and briefly to his third officer, who, notebook in hand, stood at his elbow-- ... "Four light cruisers--_Pillau_, _Königsberg_, and two more--line ahead two cables--speed twenty--course west. A destroyer screen on each bow--two a side. Away to starboard of them at five miles are five battle-cruisers--the usual lot with a big screen--too smoky to count. Cut that down, make a signal of it and get it coded, quick!"