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| - In 1866, the U.S. [Army] Corps of Engineers established the Engineer School of Application at Willets Point, NY. The first commander of this School, Maj. Henry Larcom Abbot, was almost single-handedly responsible for designing and supervising the program of research and development that defined the strategy and tactics for the mine defense of American harbors. Abbot experimented with underwater explosives, fuzes, cabling, and electrical equipment for over a decade before publishing the first manuals on the use of mines in coast defense in 1876–77.
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| abstract
| - In 1866, the U.S. [Army] Corps of Engineers established the Engineer School of Application at Willets Point, NY. The first commander of this School, Maj. Henry Larcom Abbot, was almost single-handedly responsible for designing and supervising the program of research and development that defined the strategy and tactics for the mine defense of American harbors. Abbot experimented with underwater explosives, fuzes, cabling, and electrical equipment for over a decade before publishing the first manuals on the use of mines in coast defense in 1876–77. Then, in 1886, the Endicott Board made its report on harbor defense, giving rise to a vast expansion in the building of modern forts, the installation of new guns, and the preparation of mine defenses. From about 1900 until 1946 the mine defense program grew, until upwards of 10,000 controlled mines were maintained by the U.S. Army's Coast Artillery Corps. In July 1918, the U.S. Army Mine Planter Service (AMPS) was established to maintain U.S. mine defenses. Controlled mines were anchored to the bottom of a harbor, either sitting on the bottom itself (ground mines) or floating (buoyant mines) at depths which could vary widely, from about 20 to 250 feet (6–75 m). These mines were fired electrically through a vast network of underwater electrical cables at each protected harbor. Mines could be set to explode on contact or be triggered by the operator, based on reports of the position of enemy ships. The networks of cables terminated on shore in massive concrete bunkers called mine casemates (see photo, below-right), that were usually buried beneath protective coverings of earth. The mine casemate housed electrical generators, batteries, control panels, and troops that were used to test the readiness of the mines and to fire them when needed. The map of Boston Harbor's mine fields (below, right) shows the harbor mine defenses consisting of 30 groups of mines, with 19 mines per group. Each mine was normally loaded with of TNT. So in Boston's case, a total of 57 tons of explosives guarded the harbor. Each protected harbor also maintained a small fleet of mine planters and tenders that were used to plant the mines in precise patterns, haul them back up periodically to check their condition (or to remove them back to the shore during peacetime), and then plant them again. Each of these harbors also had on-shore facilities to store the mines and the TNT used to fill them, to load and transport the mines (which often weighed over . each when loaded), and to test and repair the electrical cables. Fire control structures were also built that were used first to observe the mine-planting process and fix location of each mine and second to track attacking ships, reporting when specific mines should be detonated (so-called "observed fire"). The preferred method of using the mines was to set them to detonate a set period of time after they had been touched or tipped, avoiding the need for observers to spot each target ship.
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