long radius on the surface, and of slow speed and low capacity submerged. It will be understood that a boat is in an anxious position if she has been diving long and her battery is low when she is near enemy patrols. She has _got_ to come up and charge again, and while charging a low battery she is rather helpless. Every weapon has its weak point, and a knowledge of where the weakness lies means a chance to the opponent. Neither side had any submarines present at the Battle of Jutland, for the simple reason that neither side had at that time any boats fast enough to cruise with the Fleet and so arrive in time at a tactical rendezvous. One boat did arrive at the scene of battle next day--a homeward-bound U-boat who knew nothing of what had happened; she passed through an area of water which was covered with corpses, wreckage, and debris, and which was occasionally marked by the ends of sunken ships standing up above the surface. She cruised about, wondering, for a time, and then hurried on into harbour. If, however, there had been another fleet action during the war, the fast submarine would have been represented in it. The Germans never built anything like our K class boats, and so the war test of the type would have been carried out by us only. Tests in practice had given such good results that the reluctance of the enemy to repeat the Jutland experiment was very disappointing to the K-boat officers, who had two years of waiting for their one chance--a chance which never arrived. A submarine of 2600 tons cannot throw up her tail and slip under in a few seconds as an E boat can do--she must be taken under with due respect for her great length and size, and she cannot therefore be used on the usual Bight patrols. She is built and designed for battle only, and the type, apart from a few "incidents" with enemy submarines while employed on scouting patrols, had to share the fate of the Grand Fleet battleships which never got a fair chance at the enemy. The building of these boats, however, showed us that the big submarine was a working possibility. We designed and built them to a certain specification, and they showed they could improve on that specification in practice, and they gave most valuable data for future design.