21. She was requisitioned on 8 August 1940 as HMSAS " Parktown " and was converted to sweep magnetic mines . 22. A magnetic mine found in 1939 at Shoeburyness, now in Southend, allowed the German magnetic HMS Vernon in Portsmouth. 23. A new weapon was to be used : a large magnetic mine , that implemented a new energy mass-focusing concept. 24. On the morning of 1 January 1942 the Luftwaffe dropped two magnetic mines near Kilmacanogue but they did not explode. 25. In April 1941 " Salvia " was minesweeping in Greece and detonated five magnetic mines near the Port of Piraeus. 26. Kurchatov switched his research first to protecting shipping from magnetic mines , and later to tank armour, and finally to nuclear physics. 27. Farek's specialty in WAVES was " degaussing, " a process that demagnetized the hulls of ships so they wouldn't explode magnetic mines . 28. The British limpet adaptation was not the first magnetic mine and was not the reason why " Zimmerit " coating was developed. 29. The vessels also received degaussing against magnetic mines , and seamen were issued watertight survival suits if the ship had to be abandoned. 30. While she was passing down the Straits of Malacca on 9 September, at 07 : 44 a magnetic mine detonated to starboard.