were intended to prevent the passage of submarines were not particularly effective. The British navy knew little about mines in 1914; British naval men had always rather despised them as the "weapons of the weaker power," and it is therefore not surprising that the so-called mine barrage at the Channel crossing was not successful. A large part of it was carried away by the strong tide and storms, and the mines were so defective that oysters and other sea growths, which attached themselves to their prongs, made many of them harmless. In 1918, Admiral Sir Roger Keyes reconstructed this barrage with a new type of mine and transformed it into a really effective barrier; but in the spring of 1917, the German U-boats had little difficulty in slipping through, particularly in the night time. And from this point the distance to the trade routes south and west of Ireland was relatively a short one.
Yet, terribly destructive as these U-boats were, the number which were operating simultaneously in this and in other fields was never very large. The extent to which the waters were infested with German submarines was another particularly ludicrous and particularly prevalent misapprehension. Merchant vessels constantly reported that they had been assailed by "submarines in shoals," and most civilians still believe that they sailed together in flotillas, like schools of fish. There is hardly an American doughboy who did not see at least a dozen submarines on his way across the Atlantic; every streak of suds which was caused by a "tide rip," and every swimming porpoise, was immediately mistaken for the wake of a torpedo; and every bit of driftwood, in the fervid imagination of trans-Atlantic voyagers, immediately assumed the shape of a periscope. Yet it is a fact that we knew almost every time a German submarine slunk from its base into the ocean. The Allied secret service was immeasurably superior to that of the Germans, and in saying this I pay particular tribute to the British Naval Intelligence Department. We always knew how many submarines the Germans had and we could usually tell pretty definitely their locations at a particular time; we also had accurate information about building operations in Germany; thus we could estimate how many they were building and where they were building them, and we could also describe their essential characteristics, and the stage of progress they which had reached at almost any day.
