Earle and his associates in the Bureau of Ordnance never doubted final success. They experimented with mines, firing and anchoring devices, and on July 30th announced the development of a new type of mine, particularly adapted to deep waters. A unique feature of this mine was that it did not have to be struck to explode, but would explode if a submarine passed close to it. This was due to the firing apparatus, which was evolved from an electrical device submitted by Mr. Ralph C. Browne, of Salem, Mass., to be used on a submerged gun. Officers of the Bureau concluded this could be adapted to mines, and in May began work to that end. Commander S. P. Fullinwider, chief of the Mine Section, was aided by Mr. Browne, Lieutenant Commander T. S. Wilkinson, Jr., and Commodore S. J. Brown in producing this firing device, and others who assisted in developing the mine were Lieutenant Commanders O. W. Bagby, J. A. Schofield, W. A. Corley, C. H. Wright and H. E. Fischer, Lieutenant S. W. Cook and Lieutenant (junior grade) B. W. Grimes. With this improved mine as an argument, our ordnance officers renewed the proposal of a mine offensive in the North Sea. The memorandum the Bureau submitted was comprehensive, and contained all the essential features of the barrage plan that was later adopted and carried into effect. How could the project be best presented to the British Admiralty again? Admiral Mayo was preparing to sail within a short time for Europe. Just before his departure the entire project was discussed and the operation of the improved mines explained, as he was to bring the whole matter to the attention of the British Admiralty and the Allied Naval Council. To prevent loss of time and further insure the Admiralty's consideration, on August 17th, before Mayo sailed, I cabled Sims: Bureau of Ordnance has developed a mine which it hopes may have decisive influence upon operations against submarines. Utmost secrecy considered necessary. Request that an officer representing the Admiralty, clothed with power to decide, be sent here to inspect and thoroughly test mine, and, if found satisfactory, arrange for coöperation in mining operations. The Allied Naval Conference, held in London September 4th and 5th, which Mayo attended, took up not only the barrage project, but another proposition our Navy Department had suggested months before, a close offensive in German waters. After the meeting Mayo cabled: Conference completed after agreement upon the following points: 1. That close offensive in German waters should be carefully considered by Allies, after which they should indicate to British Admiralty contribution of old war ships they are prepared to furnish should offensive prove practicable.