– Russian troops occupy Tampere in Finland. March 13 – Upon the death of Christian VII, Frederick VI becomes king of Denmark. The next day (March 14), Denmark declares war on Sweden. March 19 – Charles IV of Spain abdicates in favor of his son, Ferdinand VII. March 22 Russian troops occupy Turku in Finland. English Wars: Battle of Zealand Point – British ships defeat those of Denmark and Norway. April–June April A volcano erupts from an unknown location in the western Pacific. This causes a localized drop in marine air temperatures during this year and a worldwide drop in marine air temperature for the following decade. Prussian philosopher Johann Gottlieb Fichte publishes his Addresses to the German Nation, having delivered them over the winter at the Prussian Academy of Sciences in Berlin before crowded audiences. April 6 – John Jacob Astor incorporates the American Fur Company. April 15 – Hubert Robert acclaimed oil painter, his painting Péché Cardinal (ca.1799) is thought to be lost or destroyed in a fire. Born 22 May 1733, Paris France, dies at the age of 74. April 16 – Troops under Colonel Carl von Döbeln clash with Russian troops in Pyhäjoki, Finland. May 2 – Peninsular War: Dos de Mayo Uprising – The people of Madrid rise up against the French troops. May 3 Finnish War: The fortress of Sveaborg is lost by Sweden to Russia. The Madrid rebels who rose on May 2 are executed near the hill of Príncipe Pío (Goya paints the fight and the execution in 1814). May 6 – Ferdinand is forced to abdicate as King of Spain by Napoleon. This effectively ends the Anglo-Spanish War (1796–1808) as the United Kingdom allies with Spain and Portugal against the French in the Peninsular War. June 12 – Finnish War: A landing of Swedish troops at Ala-Lemu, near Turku, fails. June 15 – August 14 – Peninsular War: First siege of Zaragoza – Spanish resist the French. June 19 – Finnish War: A second landing of Swedish troops at Ala-Lemu fails. June 30 Finnish War – Battle of Turku: The Swedish archipelago fleet defeats the Russians. English chemist Humphry Davy informs the Royal Society of London of his isolation and discovery of two elements by electrolysis. From lime, he has produced calcium and established that lime is calcium oxide; by heating boric acid and potassium in a copper tube, he creates