(5) The development of the hydrophone for anti-submarine work, both from ships and from shore stations. (6) The introduction of the "Otter" for the protection of merchant ships against mines. (7) A very great improvement in the rapidity of arming merchant ships defensively. (8) The extended and organized use of air craft for anti-submarine work. (9) A great development of the special service or decoy ship. (10) The introduction of a form of net protection for merchant ships against torpedo fire. Other devices followed, many of which were the outcome of work in other Admiralty Departments, particularly the Departments of the Director of Naval Ordnance and the Director of Torpedoes and Mines, working in conjunction with the Anti-Submarine or the Operations Division of the Naval Staff. Some of the new features were the development of depth-charge throwers, the manufacture and use of fast coastal motor-boats for anti-submarine work, the production of mines of an improved type for use especially against submarines, very considerable developments in the use of minefields, especially deep minefields, including persistent mining in the Heligoland Bight and the laying of a complete minefield at varying depths in the Straits of Dover; also, after the United States entered the war, the laying of a very extensive minefield right across the northern part of the North Sea. The provision of "flares" for illuminating minefields at night, and a system of submarine detection by the use of electrical apparatus were also matters which were taken up and pressed forward during 1917. During the year the system of dazzle painting for merchant ships was brought into general use. On the operational side of the Naval Staff the work of dealing with enemy submarines before they passed out of the North Sea was taken in hand by organized hunting operations by destroyers and other patrol craft, and by the more extended use offensively of our own submarines, as vessels became available. Considerable developments were effected in the matter of the control of mercantile traffic, and much was done to train the personnel of the mercantile marine in matters relating to submarine warfare. Taking these subjects in detail, it will be of interest to examine the progress made during the year. HOWITZERS