1821

1799–1825	[maths]	The French mathematician and physicist Pierre-Simon Laplace publishes the five-volume Traité de mécanique céleste/Celestial Mechanics, which applies calculus to the motions of celestial bodies and Isaac Newton's theories of the Solar System to show how its stability is implicit in the law of gravitation.
1800–1850	USA [consumer products]	A revolution in retail and wholesale trade occurs: specialization transforms the urban retail market, replacing the general store with individual stores for hardware, groceries, dry goods, furnishing, books, tobacco, and so on. Cash-only sales policies are instituted around 1806.
1810–1859	USA [agriculture]	US cotton production, the vast majority of which is grown in the southern states, rises from 171,000 bales in 1810 to just under 5.4 million in 1859.
1819–1826	UK [other structures]	Scottish engineer Thomas Telford constructs the 177 m/580 ft Menai suspension bridge over the Menai Straits between Bangor, Wales and the island of Anglesey. The first modern suspension bridge, it uses chains of wrought-iron links suspended from masonry towers at either end. Lacking stiffening girders it is vulnerable to high winds.
1821–1822	France [thought and scholarship]	French Egyptologist Jean-François Champollion deciphers the Egyptian hieroglyphics on the Rosetta Stone.
1821	USA [everyday life]	The world's first natural gas well is sunk at Fredonia, New York. Lead pipes distribute the gas to consumers for lighting and cooking.
1821	France, UK, Italy, Austrian Empire, Germany [statistics and demography]	France has a population of 30.4 million; Britain, 20.8 million (of which Ireland comprises 6.8 million); the Italian states, 18 million; the Austrian Empire, 12 million; the USA, 9.6 million; and the combined populations of Prussia, Bavaria, Saxony, and the duchies, principalities and free cities of Germany, 26.1 million.
1821–1830	USA, UK, Ireland [statistics and demography]	Emigration to the USA from Britain is 27,489, and from Ireland, 54,338.
1821	UK [civic and commercial buildings]	The Brighton Pavilion in England, designed by the English architect John Nash, is completed. Combining Indian and Chinese elements, it epitomizes the Picturesque style.
c. 1821	USA [food and drink]	Coffee is used generally throughout the USA, although it is criticized by temperance advocates and some who believe it to be an aphrodisiac.
1821	England [memoirs]	The English writer Thomas De Quincey publishes his autobiographical Confessions of an English Opium Eater in the The London Magazine.
1821	England [painting]	The English artist John Constable paints The Hay Wain, one of his best-known works, and Salisbury Cathedral from the Bishop's Grounds.
1821	England [physics]	English physicist Michael Faraday builds an apparatus that transforms electrical energy into mechanical energy – the principle of the electric motor. An armature wrapped in wire is placed between the poles of a magnet. When a current is passed though the coils, the armature spins.
1821	Germany [physics]	German physicist Thomas Seebeck discovers thermoelectricity – the conversion of heat into electricity – when he generates a current by heating one end of a metal strip comprising two metals joined together.
23 February 1821	England, Rome [births and deaths]	John Keats, English Romantic lyric poet, dies in Rome, Italy (26).
6 March 1821	Ottoman Empire, Russian Empire, Greece [revolution]	A revolt occurs in the Ottoman province of Moldavia against Turkish rule. The rebels appeal to Tsar Alexander I of Russia for help, and the prospect of a successful Russian-supported revolt while the Ottoman authorities are preoccupied with defeating regional warlords prompts a first (unsuccessful) rebellion in Greece.
5 May 1821	France [births and deaths]	Napoleon I (Napoleon Bonaparte), French general, First Consul 1799–1804, and emperor of France 1804–15, dies in exile on the island of St Helena in the South Atlantic (52).
24 June 1821	Venezuela, Colombia, Spain [wars]	The South American revolutionary leader Simón Bolívar ensures the independence of Venezuela from Spain by defeating the Spanish army of General Miguel de la Torre at Carabobo, near Caracas. A subsequent congress of the republic of Great Colombia (to which Venezuela is now added) at Cúcuta, Colombia, reorganizes the administration of the new republic, constitutionally limiting Bolívar's powers as president.
7 August 1821	UK [political events]	Queen Caroline of Britain dies, ending the dispute over her place in royal society. Her funeral cortege is diverted through the City of London, England, by her supporters, two of whom are killed in clashes with police.
15 September 1821	Guatemala, Spain, Mexico [decolonization]	Guatemala declares itself independent of Spain and aligns itself with Mexico.
11 October 1821	Russia [births and deaths]	Fyodor Mikhailovich Dostoyevsky, Russian novelist best known for Crime and Punishment (1866) and The Brothers Karamazov (1879–80), born in Moscow, Russia (–1881).
28 November 1821	Colombia, Spain, Colombia [decolonization]	Panama declares itself independent of Spain and joins the Republic of Colombia.
1 December 1821	West Indies, Spain [decolonization]	The West Indian colony of San Domingo establishes itself as a republic independent of Spain.
12 December 1821	France [births and deaths]	Gustave Flaubert, French realist novelist best known for Madame Bovary (1857), born in Rouen, France (–1880).
12 December 1821	France [law and government]	Armand du Plessis, duc de Richelieu, is succeeded as French prime minister by Jean Villèle, ending the rule of the right centre and leading to a period of reaction under the ultra-conservatives.