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used their growing knowledge of electrical theory in an attempt to devise a machine that would pinpoint metal. The use of such a device to find ore-bearing rocks would give a huge advantage to any miner who employed it. Early machines were crude, used a lot of battery power, and worked only to a very limited degree. In 1874, the Parisian inventor, Gustave Trouvé, developed a hand-held device for locating and extracting metal objects such as bullets from human patients. Inspired by Trouvé, Alexander Graham Bell developed a similar device to attempt to locate a bullet lodged in the chest of American President James Garfield in 1881; the metal detector worked correctly but the attempt was unsuccessful because the metal coil spring bed Garfield was lying on confused the detector. 26 The Polish Mine Detector was invented by a Signals officer, Lieutenant Józef Stanis ł aw Kozacki (1909 – 1990), serving with the 1st Polish Army Corps, which was eventually stationed in Scotland following the German defeat of Poland in 1939. In 1937, he had been commissioned by the Department of Artillery of the Polish Ministry of National Defence to develop an electrical machine capable of detecting unexploded artillery shells on firing ranges. After successfully developing a machine, he altered the purpose of the machine to detect land mines. According to his fellow officer, Jan Zakrews, Kozacki, was given a laboratory, a workshop, and an aide with whom he completed and perfected the mine detector. Prototypes were built and tested. At the end of 1941, the technical unit of the Polish General Staff in London exhibited a new, improved model to the Ministry of War Production. The British authorities accepted it as the best one of its time and ordered mass production, under the name of Mine Detector Polish Mark 1. Some 500 of these detectors were issued to the 8th Army before the battle of El Alamein, to clear the terrain for Operation Lightfoot to take place. 27 While the Germans dominated mine design and mine laying, the British were the great innovators in clearance techniques, initially as a result of their own short sightedness. 28 The ÂScorpionÊ The mine flail tank idea began in 1941, with Abraham S.J. du Toit, 29 a motor engineer in civilian life and a sergeant in the South African artillery, who developed a novel device that detonated mines by beating the ground with heavy chains or wire ropes driven by a rotating drum. The force of a flail strike above a buried mine mimicked the weight of a person or vehicle causing the mine to detonate, but in a safe manner that did little damage to the flails or the vehicle, 26 E.S. Grosvenor & M. Wesson, Alexander Graham Bell: The Life and Times of the Man Who Invented the Telephone (New York: Harry N. Abrahms, Inc., 1997), p. 107. 27 Tadeusz Modelski , The Polish Contribution to The Ultimate Allied Victory in The Second World War (Sussex: Privately Published, 1988), p. 221. 28 http://www.secretscotland.org.uk/index.php/Secrets/PolishMineDetector 29 Sgt du Toit, soon promoted to Major, was closely involved in the development in Britain of what became the Matilda Baron. Although the Baron never saw combat, it did provide the knowledge and experience that eventually led to the development and fielding of the highly successful Sherman ‘Crab’ flail tank, which General Hobart used during the Normandy landings in 1944.