Scapa Flow in the Orkney Islands off the north of Scotland was a perfect base for the Grand Fleet, because it was well placed to watch the way out of the North Sea through the two-hundred-mile gap between Norway and the Shetlands, and also because the tremendous tidal currents sweeping through it prevented submarines from sneaking about too close. Six hundred miles south-east was the German Fleet, near the North Sea end of the Kiel Canal. Between lay a hundred and twenty-five thousand square miles of water on which, taking one day with another the whole year round, you could not see clearly more than five miles. This "low average visibility" accounts for all the hide-and-seek that suited German tricks so well. Within three hours of the British Declaration of War two British submarines were off for Heligoland, where they spied out the enemy's fleet. From that time on every German move was watched from under the water, on the water, or over the water, and instantly reported by wireless to the Admiralty in London and to the Grand Fleet based on Scapa Flow. Then, when the first British army began to cross into France, the Fleet covered its flank against the Germans, and went on covering it for fifty-one months without a break, through cold and wet, through ceaseless watching, and through many fights. The first fight was off Heligoland, when British light cruisers and destroyers went into the Bight on a scouting cruise planned by the Admiralty, not the Grand Fleet. The German destroyers fell back to lure the British within range of the enormous guns on Heligoland. That failed. But suddenly, out of the morning mist, came a bunch of German shells throwing up water-spouts that almost splashed aboard. Instantly the British destroyers strung out, farther apart, and put on full racing speed as the next two bunches crept closer in. _Whirrh!_ went the fourth, just overhead, as the flotilla flagship _Arethusa_ signalled to fire torpedoes. At once the destroyers turned, all together, lashing the sea into foam as their sterns whisked round, and charged, faster than any cavalry, straight for the enemy. When the Germans found the range and once more began bunching their shells too close in, the British destroyers snaked right and left, threw out the range-finding, and then raced ahead again. In less than ten minutes they had made more than five miles, fired their torpedoes, and were on their way back. Then up came the British cruisers and converged on the _Mainz_, which went down fighting. "The _Mainz_," wrote one of the British officers who saw her, "was immensely gallant. With her whole midships a fuming inferno she kept one gun forward and another aft still spitting forth fury and defiance like a wild cat mad with wounds." In the mean time Jellicoe, rightly anxious about leaving British light craft unsupported by heavier vessels so close to the German Fleet, urged the Admiralty to change their plan by sending on the battle cruisers.