Porte Baby with Bristol Bullet on top plane.
In designing and perfecting flying-boats there were more difficulties than in producing float seaplanes, for the technical problems were great, while engines of sufficient horse-power were not to be had in the early part of the war, and indifference and scepticism had to be overcome. It was not until the spring of 1917 that suitable flying-boats were in being. But this was in time for them to meet the big German submarine effort, when the great yards at Weser, Danzig, Hamburg, Vagesack, Kiel, and Bremen, working day and night, with production driven to its highest pitch by standardisation, were pouring out into the North Sea an incredible number of U-boats.
During this year—a year when it looked as though the Under-sea boats would strangle our merchant shipping and the danger was greater to England than her people realised—forty flying-boats were put into commission, and sighted sixty-eight enemy submarines and bombed forty-four of them.
A submarine is a steel boat shaped something like a cigar. When on the surface it is driven by two petrol engines. Under the surface it is driven by two electric motors, the electricity being obtained from storage batteries. At the bow and stern are horizontal rudders known as hydroplanes. Under ordinary circumstances, when the submarine is about to dive, water is let into tanks until the boat is just floating on the surface with only the conning-tower showing. The petrol engines are stopped and the electric motors are started. Then the hydroplanes are turned down and they force the submarine under the water. The submarine uses its power of travelling under the water to stalk its prey and to hide from its enemies.
When the intensive German submarine campaign began, the methods of hunting U-boats from surface ships had not been perfected. The hydrophone was crude, the technique of using depth charges was not perfected, and the mines and nets were not adequate. Also, the Dover barrage was not then in being. So Fritz, as the service called the Hun submarine, went south—about from his bases to his hunting-grounds.
Picture the sinister grey steel tubes dropping away from the dock in the German harbour as the Commander in the conning-tower gave the order to cast off, the swirl of water at the stern as the twin propellers took up their job, and the gay flutter of signal flags hoisted to the collapsible mast as they passed out of the harbour—a harbour which they would not see, if all went well with them, for from fifteen to twenty-five days, and which, if things went well for the Allies, they would never see again. Once outside the harbour, the Commander would order the engines whacked up to the economical cruising speed of eight to nine knots, a speed at which he could do about two hundred miles a day, and would then turn south, and so proceed on the surface through the North Sea to the Straits of Dover.
Passing through the Straits, either at night on the surface or in the daytime under the water, the Commander would pass down the south coast of England and cruise on the surface in the chops of the English Channel or off the approaches to Ireland. Here he would meet our merchant ships coming in with food, raw material, munitions, and passengers, and either sink them by gun-fire or by torpedo. The attack would be made without warning. Sometimes survivors, who had got away in boats from the doomed vessel, would be shelled. And once the survivors were taken on the deck of a submarine, their life-belts removed, and then the submarine submerged, leaving the unfortunates to drown.
On their run through the North Sea the submarines passed between the Hook of Holland and Harwich Harbour, the distance between the two places being one hundred miles.
Harwich Harbour is a sheltered stretch of water on the East Coast made by the rivers Stour and Orwell emptying into the southern portion of the North Sea. It was the centre of intense anti-Hun activity. It was here that Rear-Admiral Tyrwhitt had his "hot-stuff" destroyer flotilla, that the hydrophone for detecting enemy submarines under the surface of the sea was evolved, that our own submarines which operated in the Bight of Heligoland had their base, and where the flying-boat station of Felixstowe was situated. And it was at Felixstowe that the service experimental flying-boats were designed and built, and a flying-boat squadron operated. During 1917 this squadron, which used an average of only eight boats a month, sighted forty-seven enemy submarines and bombed twenty-five, besides destroying enemy seaplanes and bringing down a Zeppelin in flames.