1756: Jacques Cassini, discoverer of the Cassini Division between the A and B rings of Saturn, died. 1775: Paul Revere began his famous ride from Charlestown to Lexington, MA, warning American colonists that the British were coming. 1838: Lecoq de Boisbaudran, discoverer of gallium, was born. 1906: San Francisco was hit by a disastrous earthquake. 1907: Denmark became the first country to use fingerprinting to identify criminals. 1923: Yankee Stadium opened. 1925: World Amateur Radio Day (WARD) established to commemorate the founding of the International Amateur Radio Union (IARU). The first U.S. commercial transcontinental radio transmission of a radio facsimile was sent from San Francisco to New York City. 1942: An air squadron from the USS Hornet led by Lt. Col. James H. Doolittle raided Tokyo and other Japanese cities. 1945: Sir John Ambrose Fleming, inventor of the diode tube (Fleming valve), died. 1955: Nobel laureate Albert Einstein, died. 1989: Thousands of Chinese students demanding democracy tried to storm Communist Party headquarters in Beijing.