Mines, like their cousin the depth charge, played a very important part in combating the submarine menace. As Germany showed a partiality for them, we did our best to oblige her. The most extensive mine-field ever planted was sown by Great Britain. It stretched from the Orkney Islands to the fringe of the territorial waters of Norway, and covered an area of not less than 22,000 square miles. Access to the Atlantic, rigidly guarded by the naval police of the Patrol, was provided on the Scottish side. Other British mine-fields existed at the farther end of the North Sea, guarded by a hundred or more surface craft, and in the neighbourhood of Flanders, Heligoland, and Denmark. The object of these vast prohibited areas was to prevent U-boats from gaining easy access to the great ocean routes. Germany early laid a mine-field inside the Skager-Rack to prevent British submarines from entering the Baltic—which it did not do—and afterward violated international law by taking similar steps in the Cattegat. While the latter operation was proceeding, certain of our naval forces came across a batch of enemy mine-layers at their nefarious task, sank ten of them, and rescued their crews. The men ought to have been ordered to walk the plank, _pour encourager les autres_, as Voltaire said of Admiral Byng’s execution. Britain’s bold bid to foil the U-boats was undertaken, in the words of the official explanation, “in view of the unrestricted warfare carried on by Germany at sea by means of mines and submarines, not only against the Allied Powers, but also against neutral shipping,” and because merchant ships were “constantly sunk without regard to the ultimate safety of their crews.” The big northern mine-field proved very useful. That was why the enemy immediately started a loud-mouthed campaign in neutral countries in the hope of inciting their Governments to protest against an effective method of warfare decidedly prejudicial to the German cause. A word or two about the surface barrage maintained across the Channel. Every day and night, ceaselessly and relentlessly, in fair weather and foul, over a hundred armed patrolling craft of various sorts and sizes kept sentinel at the great southern gateway, and enabled troops and munitions to cross the drawbridge from England to France. It was not so difficult a task during the day as at night. When darkness fell the guard burned flares that made the passage of a submarine travelling on the surface an exceedingly dangerous undertaking. If a U-boat tried the underwater route, there were other means of obstruction quite as deadly as the methods of the fire-breathing trawlers. There is no truth in the yarn that a steel net stretched across the Straits of Dover, thereby guaranteeing with more or less certainty the immunity of transports from attack by underwater vessels.