1787: German physicist Joseph von Fraunhofer, who was the first to study the dark lines in the solar spectrum (Fraunhofer lines), was born. 1834: The city of York in Upper Canada was incorporated as Toronto. 1899: Felix Hoffmann trademarked "Aspirin," ('A' in acetyl chloride, "spir" in spiraea ulmariaand the 'in' was a then familiar name ending for medicines). 1900: Gottlieb Daimler, German engineer and pioneer automobile manufacturer, died. 1913: Niels Bohr first wrote of his idea for the atomic model in a paper to Rutherford. 1929: Auto manufacturer David Buick died. 1932: American conductor John Philip Sousa died. 1937: Soviet cosmonaut Valentina Tereshkova, who was the first woman to fly in space, and is the only solo woman astronaut, was born. 1939: Ferdinand von Lindemann, who first proved that p is transcendental, died. 1981: Walter Cronkite signed off for the last time as principal anchorman of "The CBS Evening News." 1990: The SR-71 Blackbird set a transcontinental record, flying 2,404 miles in 1h:08m:17s. 1992: The long-anticipated, much-feared "ticking time bomb" Michelangelo virus struck around the world, but ended up being relatively harmless.