hour, and under the surface it made little more than seven or eight. If the destroyer once discovered its presence, therefore, it could reach its prey in an incredibly short time. It could attack with its guns, and, if conditions were favourable, it could ram ; and this was no trifling accident, for a destroyer going at thirty or forty miles could cut a submarine nearly in two with its strong, razor-like bow. In the early days of the war these were the main methods upon which it relied to attack, but by the time that I had reached London, another and much more frightful weapon had been devised. This was the depth charge, a large can containing about three hundred pounds of TNT, which, if it exploded anywhere within one hundred feet of the submarine, would either destroy it entirely or so injure it that ' the victim usually had to come to the surface and surrender.
I once asked Admiral Jellicoe who was the real inventor of this annihilating missile.
"No man in particular," he said. "It came into existence almost spontaneously, in response to a pressing need. Gunfire can destroy submarines when they are on the surface, but you know it can accomplish nothing against them when they are submerged. This fact made it extremely difficult to sink them in the early days of the war. One day, when the Grand Fleet was cruising in the North Sea, a submarine fired a torpedo at one of the cruisers. The cruiser saw the periscope and the wake of the torpedo, and had little difficulty in so manoeuvring as to avoid being struck. She then went full speed to the spot from which the submarine had fired its torpedo, in the hope of ramming it. But by the time she arrived the submarine had submerged so deeply that the cruiser passed over her without doing her any harm. Yet the officers and crew could see the submerged hull; there the enemy lay in full view of her pursuers, yet perfectly safe! The officers reported this incident to me in the presence of Admiral Madden, second in command.
"’Wouldn't it have been fine,' said Madden, 'if they had had on board a mine so designed that, when dropped overboard, it would have exploded when it reached the depth at which the submarine was lying?'
"That remark," continued Admiral Jellicoe, "gave us the germinal idea of the depth charge. I asked the
