Of course, the torpedo was the usual weapon used. A hit on a big ship, once the destroyer screen has been avoided, is comparatively easy; a hit on a U-boat is mighty difficult. The attacker is looking at his target with his eye (the top prism of the periscope) only a few inches above water-level. His view of the enemy, therefore, is confined to a square-looking conning-tower, with heavy "jumping wires" (sweep deflectors) running down from it to a low grey line of hull. It is therefore difficult to exactly estimate the enemy's speed or course, and the short time at the attacker's disposal for deciding on his deflection and turning to bring his tubes to bear does not allow of an accurate calculation based on bearings of the passing target. In fact, it is usually a case of "make up your mind and shoot quick." In addition to the handicap of the target being small, there is the knowledge that one must be far more careful to show only a little of the periscope during the attack, as submarines are far more on the _qui vive_ for periscopes than big ships are. For one thing, they know what a periscope looks like; and for another, they have more knowledge of what a torpedo can do against craft of small buoyancy. The moral effect of the use of submarine against submarine was probably greater than the direct effect. It discouraged U-boats from coming to the surface to use their guns against merchant ships, and restricted them to their torpedo armament, which was of course limited. A U-boat on the surface had the same sensations as a man would have who fell overboard crossing the Indian Ocean, where the sharks are always keeping station astern of a ship: a feeling of impatience, and anxiety to get back to where he came from. As an instance, I will mention the case of U 81, who, while engaged in the congenial work of pumping shells into an English merchant ship, received two torpedoes amidships from "E 54," who had been following operations through her periscope since U 81 first rose to the surface. "E 54" picked up seven survivors, one of whom was the Captain. The latter officer was somewhat damaged by the explosions, and was in danger of drowning until "E 54's" First Lieutenant dived for him and brought him aboard. Another survivor was the Warrant Officer, who, on being taken below, sent a message by "E 54's" coxswain to Commander Raikes, to the effect that it was advisable to keep a good look-out and to submerge again soon, _as there was another U-boat diving near at hand_. Commander Raikes would no doubt have acted on the second part of this excellent advice had it not been necessary for him to assist the damaged steamer into harbour. If one once begins to quote cases, it is difficult to keep from irrelevance, but I must note here that at the moment of the sinking of U 81, the crew of the steamer had very wisely abandoned ship, and the change from a U-boat in full view to a ditto E boat took place so suddenly that