The US flag is modified to have twenty-three stars, reflecting the addition of two new states: Alabama and Maine.

Debate over slavery in the US heats up; The Missouri Compromise admits Maine into the Union as a free state, with Missouri to enter the next year as a slave state. Slavery is banned north of the 36 30' line of latitude in the Louisiana Territory.

Missouri Compromise Missouri is admitted to the Union as a slave state, Maine as a free state. Slavery is forbidden in any subsequent territories north of latitude .

The Arithmometer was the first commercially successful mechanical calculator patented

The first Christian missionaries arrived in the Hawaiian Islands.

Christian Friedrich Nasse formulated Nasse's law: hemophilia occurs only in males and is passed on by unaffected females.

Gideon Mantell discovers, in England, a fossil trunk of a tree resembling that of a tropical palm, evidence of a much warmer climate.

André-Marie Ampère formulates one of the basic laws of electromagnetism, the right-hand rule for the influence of an electric current on the magnet and demonstrates that two wires that are carrying an electric current will attract or repel each other, depending on whether the occurrence are in opposite where the same directions.

Dominique-François Arago discovers the magnetic effect of electricity passing through a copper wire, demonstrating that iron is not necessary for magnetism.

Augustin-Jean Fresnel invents the so-called Fresnel lens, a lens used in lighthouses.

The science of electrodynamics is born with the announcement of Hans Christian Ørsted's discovery of electromagnetism.

Painting by John Constable: The Hay Wain depicts a rural scene on the River Stour between the English counties of Suffolk and Essex. It hangs in the National Gallery in London and is regarded as "Constable's most famous image" and one of the greatest and most popular English paintings. Painted in oils on canvas, the work depicts as its central feature three horses pulling what in fact appears to be a wood wain or large farm cart across the river. Willy Lott's Cottage, also the subject of an eponymous painting by Constable, is visible on the far left. The scene takes place near Flatford Mill in Suffolk, though since the Stour forms the border of two counties, the left bank is in Suffolk and the landscape on the right bank is in Essex.

Michael Faraday invents the electric motor and generator.

The US flag is modified to have twenty-four stars, reflecting the addition of one new state: Missouri.

Slave Revolt: South Carolina Freed slave Denmark Vesey attempts a rebellion in Charleston. Thirty-five participants in the ill-fated uprising are hanged.

Charles Babbage takes first steps in the construction of machines that would compute numbers

Etienne Geoffroy publishes Anatomical Philosophy discussing similarities between skeletal structures — such as bat wings, paws and hands — that support the evolutionary claims of Lamarck. He also argues that arthropods and vertebrates have similar but inverse body plans, an assertion that will ultimately be widely accepted.

Between 1822-1824, Thomas Andrew Knight, John Goss, and Alexander Seton all independently perform crosses with the pea and observe dominance in the immediate progeny, and segregation of various hereditary characters in the next generation. However, they do not study later generations or determine the numerical ratios in which the characters are transmitted.

William Buckland publishes an account of how ancient hyenas lived and fed in Kirkdale Cave, based on their fossil remains. This is one of the first descriptions of living habits based on fossil evidence.

Omalius d'Halloy names the Cretaceous System, after massive chalk deposits. This time period will later be identified with the last dinosaurs and the first flowering plants.

William Conybeare and William Phillips name the Carboniferous System, a period associated with coal deposits. This time period will also become known as the Mississippian and Pennsylvanian Periods in the United States.

Slavery is abolished in Chile.

Physicist Michael Faraday (1791-1867) describes the liquification of chlorine in On fluid chlorine. Faraday finds that gasses of certain kinds, when kept under constant pressure, will condense until they cool. This latter discovery ushers in the beginning of mechanical methods of refrigeration.

Small-scale drilling for oil begins at Baku, a Russian port city on the west coast of the Caspian Sea, now the capital of Azerbaijan. The drilling marks the beginning of the modern petroleum industry, and by 1900 nearly half the world's oil will come from the Baku oil fields.

Thomas Andrew Knight confirms reports of dominance, recessivity, and segregation in peas, but does not detect regularities.

William Buckland finds a skeleton covered in ocher. Called the Red Lady, it will later be identified as Cro-Magnon (and male).

Mexico outlaws slavery. This decision creates the incentive for Anglo Texans to fight for independence in 1835-1836.

Mexico becomes a republic, three years after declaring independence from Spain.

William Buckland publishes Notice on the Megalosaurus ("giant lizard"), the first dinosaur fossil to be described and named, although the term "dinosaur" doesn't yet exist. Buckland also announces the discovery of the first fossil mammal from the Mesozoic.

Réflexions sur la puissance motrice du feu (On the motive power of fire) by Nicolas Léonard Sadi Carnot shows that work is done as heat passes from a high temperature to a low temperature; defines work; hints at the second law of thermodynamics; and suggests internal combustion engines.

The Diary of Samuel Pepys is published in Britain. Pepys (1633-1703) had been a secretary of the Admiralty, a member of Parliament, and President of the Royal Society, and his Diary presents an important and entertaining picture of London during the Restoration period.

The Erie Canal (from Albany to Buffalo, New York) opens on October 26, connecting the Midwestern U.S. with the Atlantic Ocean, via the Great Lakes, and stimulating the development of Fort Dearborn (know today as Chicago), Cleveland and Columbus Ohio, and upstate New York cities like Rochester, Syracuse and Little Falls.

The first passenger steam railway opens, between Stockton and Darlington, England.

John Quincy Adams becomes the sixth president of the United States.

Father John MacEnery starts digging in Kent's Cave in Devon. He'll eventually find human remains in the same layer as those of extinct mammals, a finding that will be dismissed by Buckland.

Gideon Mantell publishes Notice on the Iguanodon, the second description of a dinosaur and the first description of an herbivorous fossil reptile.

The Last of the Mohicans, by James Fenimore Cooper, is published.

The first photographic images produced by Joseph-Nicéphore Ni pce

Karl Ernst von Baer first demonstrated the mammalian ovum; he regarded the sperm cells as "Entozoa," i.e., parasites, and named them spermatozoa.

Theory of systems of rays by William Rowan Hamilton is a unification of the study of optics through the principle of "varying action". It contains his correct prediction of conical refraction. When his prediction is verified, he becomes a well-known and is knighted.

While studying the behavior of fluids under a microscope, botanist Robert Brown (1773-1858) discovers what is today called "Brownian motion".

A year after discovering the mammalian egg cell, Karl Ernst von Baer publishes Entwickelungsgeschichte der Thiere tracing the developmental history of animals.

Publication of Karl Ernst von Baer's The Embryology of Animals which strongly opposed preformationism.

Adolphe Brongniart publishes Prodrome d'une histoire des Végétaux Fossils, a study of fossil plants. He outlines four distinct phases in plant prehistory: (1) primitive plants from the Coal Measures, (2) the first conifers, (3) domination by cycads and conifers, and (4) flowering plants.

Mary Anning discovers Britain's first recognized pterosaur fossil. (Gideon Mantell has already found pterosaur remains, but has attributed them to a bird).

Chemist Friedrich Wöhler (1800-1882) synthesizes the organic compound urea, a feat previously thought impossible because of the vital force thought to be a part of organic substances.

Chemist James Smithson (1765-1829) bequeaths £100,000 to found the Smithsonian Institution in Washington, D.C. The Institution will be founded in 1846.

The first steam locomotive to operate on a U.S. railroad begins service between Carbondale and Honesdale, Pennsylvania. The engine, "The Stourbridge Lion", has been imported from the Stephenson Engine Works in London.

Andrew Jackson becomes the seventh president of the United States.

Slavery abolished in Mexico.

Philippe-Charles Schmerling discovers a Neanderthal fossil, the partial cranium of a small child. The fossil will not be accurately identified as Neanderthal, however, for a century, though Charles Lyell will illustrate it in Antiquity of Man in 1863.

Jules Desnoyers names the Quaternary System, a time in which humans have lived.

Gustave-Gaspard Coriolis coins the term KINETIC ENERGY in On the calculation of mechanical action.

Joseph Henry shows that passing an electric current through a wire wrapped into coils produces a greater magnetic field than is produced when that same current is passed through a straight wire, and that an insulated wire wrapped around an iron core can produce a powerful electromagnet.