21st August 1770 – James Cook formally claimed eastern Australia for Great Britain, naming it New South Wales. 1831 – Nat Turner led black slaves and free blacks in a rebellion in Southampton County, Virginia. 1879 – The Virgin Mary, along with St. Joseph and St. John the Evangelist, reportedly appeared to the people of Knock, County Mayo, Ireland. Paving the way for lots of little plastic figurines. 1911 – The Mona Lisa was stolen by an employee at the Louvre in Paris. 1968 - Dozens of people were killed in a massive military clampdown in Czechoslovakia. 1983 - Benigno Aquino, the Philippines opposition leader, was murdered just minutes after returning home from exile. 1986 - 1,700 people died when a cloud of lethal gas escaped from a volcanic lake, Lake Nyos, in Cameroon.