The commander withdraws from his food, shouts an order and an electric alarm sounds inside the hull. The ship buzzes with activity. The guns on deck are hastily housed. Bridge appurtenances are housed also, and sailors dive down through the deck-holes. The commander follows. Water begins to gurgle into the ballast-tanks while the crew seal every opening. Down goes the U-47-1/2 until only her periscope shows, a periscope painted sea-green and white--camouflaged. The eyes of the watch-officer are glued to the periscope. "She is a Dutchman, sir," he says at length. The commander steps to the periscope and takes a look. The Dutchman has no wireless and is bound for some continental port. It is not wise to sink every Dutch boat one meets--although German submarines have sunk a sufficient number of them, in all conscience. At all events, the steamship goes in peace and the submarine comes to the surface. The commander is glad, because electric power must be used when the vessel is moving under water and there must be no waste of this essential element. So the submarine proceeds on her way, wallowing and tumbling through the heavy graybacks of the North Sea. At length after fifty-four hours the necessity of sleep becomes apparent. The ballast-tanks are filled and the craft slowly descends to the sandy bottom of the sea. It is desirable that the crew go to sleep as quickly as possible, because when men are asleep they use less of the priceless supply of oxygen which is consumed when the boat is under water. However, the commander allows the men from half an hour to an hour for music and singing. The phonograph is turned on and there on the bottom of the North Sea the latest songs of Berlin are ground out while the crew sit about, perhaps joining in the choruses--they sang more in the early days of the war than they do to-day--while the officers sit around their mess-table and indulge in a few social words before they retire. In the morning water from the tanks is expelled and the boat rises to greet a smiling sea. Also to greet a grim destroyer. The war-ship sees her as she comes up from a distance of perhaps a mile away. All steam is crowded on while the leaden-gray fighter--the one craft that the submarine fears--makes for her prey. Sharp orders ring through the U-boat. The tanks are again filled, and while the commander storms and ejaculates, everything is made tight and the vessel sinks beneath the surface. The electric-motors are started and the submarine proceeds under water in a direction previously determined, reckoned in relation to the course of the approaching destroyer.