According to Sir John, a submarine in order to remain submerged indefinitely, must be able to extract air from the water, as does a fish, for it is air that is needed most under water. Up to the time of Sir John H——’s discovery this had never been accomplished.
Reasoning that it must be a peculiarity about the gills of a fish that permitted it to extract air from the water, Sir John had experimented along this line, and his experiments finally terminated successfully. When the D-16 had proved the practicability of Sir John’s theory, the vessel had immediately been put into commission, and the construction of others begun.
The secret of the D-16 was known to only a trusted few besides the crew of the vessel—the King, Winston Churchill, and David Lloyd George, Chancellor of the Exchequer. Besides her ability to remain submerged, D-16 was also many knots faster than any other submarine.
From a naval viewpoint, perhaps, the war up to this time had not progressed as favorably as had been expected. While the allied forces on the continent had been hemming in the Germans and their allies, driving them back from beneath the very walls of Paris, back across the Marne and across the Aisne, and while the legions of the Czar had been attempting to force a passage of the Carpathian mountains for an invasion of Hungary and Austria, and making determined assault within the borders of East Prussia, the British, French and Russian fleets had been practically inactive.
True, there had been several important naval battles, but none which could be called decisive, although whatever advantage there was was with the British.
The French, with the Austrian fleet cooped up in their base in the Adriatic, had little to do but to see that the Austrians were not allowed to escape. The Russian fleet had had one or two brushes with the Turks, but these were unimportant.
In the North Sea England was having more difficulty. German submarines, from their base at Ostend, had made several successful raids into Dover harbor, on the British coast; three unfortified towns on the coast had been razed by German shells and German aeroplanes had been seen flying about in the vicinity of London.
Huge Zeppelin balloons, upon which, England believed, the German Emperor planned to risk all should other means fail, had been seen over the British Isles, but had been driven off. One had been sunk. After this, England, ever fearful of an air raid, took heart, and agreed with the nobleman who said that a raid by air was not feasible.
Besides the ships of war that had been sunk by the Germans, British merchant vessels had also been sent to the bottom by the enemy’s submarines.
But the main German fleet was cooped up in Heligoland and in the Kiel canal by the British blockade, which, in itself, was proof positive of Great Britain’s naval supremacy. The Kaiser had no mind to give open battle to England on the sea.