1784 in science

• September 10 – Edward Pigott identifies the variable star Eta Aquilae from York, England. • October 19 – John Goodricke begins his observations of the variable star Delta Cephei from York. ==Biology==

• Publication of the Annals of Agriculture edited by Arthur Young begins in Great Britain. • Peter Simon Pallas begins publication of Flora Rossica, the first Flora of Russia. ==Chemistry==

• L'Abbé René Just Haüy states the geometrical law of crystallization. • Antoine Lavoisier pioneers stoichiometry. • Citric acid is first isolated by Carl Wilhelm Scheele, who crystallizes it from lemon juice. • Cholesterol is isolated. ==History of science==

• Publication of David Bourgeois' ''Recherches sur l'art de voler, depuis la plus haute antiquité jusque'a ce jour'' in Paris, the earliest work on the history of flight. ==Mathematics==

• Carl Friedrich Gauss, at the age of seven, pioneers the field of summation with the formula summing 1:n as (n(n+1))/2. ==Medicine==

• 11 February – Royal College of Surgeons in Ireland chartered. • 12 March — Appointment of the French Royal Commission on Animal Magnetism (the Commission's Report was presented to King Louis XVI on 11 August 1784). • Madame du Coudray, pioneer of modern midwifery in France, retires. • Benjamin Franklin makes the first known specific reference (in a letter) to the wearing of bifocal spectacles. • John Hunter first describes the condition phlebitis. ==Paleontology==

• The first description of a Pterodactylus fossil is made by Cosimo Alessandro Collini, although he is unable to determine what kind of creature it is. ==Physics==

• January 15 – Henry Cavendish's paper to the Royal Society of London, Experiments on Air, reveals the composition of water. • Jean-Paul Marat publishes ''Notions élémentaires d'optique (Elementary Notions of Optics'') ==Surveying==

• William Roy measures the baseline for the Anglo-French Survey (1784–1790) linking the observatories of Paris and Greenwich. The measurement is accurate to within a few inches in a distance of over 280,000 ft., an unprecedented accuracy for this time. Roy is awarded the Copley Medal in the following year. ==Technology==

• April 28 – James Watt receives a British patent for his parallel motion and other improvements to the steam engine. • June 4 – Élisabeth Thible becomes the first woman passenger in a hot-air balloon, at Lyon, France. • August 21 – Joseph Bramah receives his first lock patent in London. • Rev. Dr. Edmund Cartwright designs his first power loom in England. • Henry Cort of Funtley, England, applies the coal-fired reverbatory furnace to the puddling process for conversion of cast to wrought iron. ==Awards==

• Copley Medal: Edward Waring ==Births==

• March 12 – William Buckland, English geologist and paleontologist (died 1856) • June 3 – William Yarrell, English zoologist and bookseller (died 1856) • June 17 – Andrew Crosse, English 'gentleman scientist', pioneer experimenter in electricity (died 1855) • July 22 – Friedrich Bessel, German mathematician (died 1846) • September 1 – Thomas Frederick Colby, English cartographer (died 1852) ==Deaths==

• May 12 – Abraham Trembley, Genevan naturalist (born 1710) • September 1 – Jean-François Séguier, French astronomer and botanist (born 1703) • September 4 – César-François Cassini de Thury, French astronomer (born 1714) ==References==