Earth Science Concerning the Cause of the General Trade Winds (Hadley) – introduces idea of Hadley cell c. 1740 Biology Bonnet discovers parthenogenesis in aphids 1742 Chemistry Brandt isolates cobalt 1743 Mathematics Traité de dynamique (D’Alembert) Simpson’s rule formulated by Thomas Simpson Physics Théorie de la figure de la terra (Theory of the Shape of the Earth; Alexis Claude Clairaut) – confirms that the Earth is shaped like an oblate spheroid 1744 Physics Maupertuis formulates the principle of least action 1746 Physics Musschenbroek reports his discovery of the Leyden jar 1747 Chemistry Marggraf discovers sucrose in beet 1749 Biology Linnaeus introduces binomial nomenclature in taxonomy 1751 Astronomy Lacaille and Lalande observe lunar parallax Biology Whytt describes and emphasizes the importance of reflex reactions Chemistry Cronstedt discovers nickel Earth Science Guettard observes evidence for ancient volcanic activity Technology La Condamine first reports existence of rubber in Europe 1752 Physics Franklin performs his electrical experiment with a kite in a thunderstorm 1753 Biology Species Plantarum (Linnaeus)

1754 Medicine Lind publishes a cure for scurvy 1756 Chemistry Experiments upon Magnesia Alba, Quicklime, and some other Alcaline Substances (Black) 1757 Biology Monro publishes a work distinguishing clearly between the lymphatic and circulatory systems Physics Black introduces concept of latent heat Carton observes fluctuations in Earth’s magnetic field 1758 Physics Dollond invents achromatic lens system Alexis Claude Clairaut informs the Académie des Sciences in November that Halley’s Comet would be at perihelion on April 13, 1759 (the actual date was March 13) 1759 Biology Wolff presents the thesis that destroyed the preformation theory of development and held instead that organs develop from undifferentiated tissue c. 1760 General The Lunar Society formed by Erasmus Darwin, Mathew Boulton, and William Small in Birmingham, England 1761 Astronomy Nathaniel Bliss observes a transit of Venus enabling him to calculate the horizontal parallax of the Sun as 10.3″ Medicine Auenbrugger publishes his work on chest percussion De sedibus et causis morborum (Morgagni) Physics Black measures latent heat of fusion of ice 1763 General The Royal Society of Edinburgh is founded

1764 Technology Watt repairs a model of a Newcomen steam engine and begins to develop his own improved engine Hargreaves invents the spinning jenny 1765 Astronomy Nevil Maskelyne, fifth Astronomer Royal, first publishes the Nautical Almanac, which uses Greenwich as its prime meridian Physics Cavendish formulates concept of specific heat (unpublished) 1766 Physics Three Papers containing Experiments of Factitious Airs (Cavendish) – distinguishing hydrogen (inflammable air) and carbon dioxide (fixed air) from common air 1767 Biology Spallanzani disproves theory of spontaneous generation in microorganisms 1768 Earth Science Desmarest shows that not all rocks are sedimentary James Cook sets sail in the Endeavour for the South Pacific to observe the planet Venus and chart the coast of New Zealand and E. Australia Mathematics Lambert publishes his proof that π and e are irrational 1769 Technology Arkwright patents his spinning machine 1770 Technology Cugnot builds a two-piston steam boiler for military use, probably the first fuel-driven vehicle 1771 Earth Science (to 1775) Werner develops his theory of neptunism 1772 Astronomy Bode publishes Bode’s law Chemistry Lavoisier experiments on combustion

1774 Chemistry Gahn discovers manganese Priestley discovers oxygen 1776 Anthropology De generis humani variatate nativa (Blumenbach) – classifies humans into five races Chemistry (to 1777) Eléments de chimie théorique et pratique (Guyton de Morveau) – an attempt to quantify chemical affinity 1777 Chemistry Chemical Observations and Experiments on Air and Fire (Scheele) 1779 Botany Ingenhousz shows that plants absorb carbon dioxide and give off oxygen (photosynthesize) in the presence of light 1781 Astronomy Herschel discovers Uranus Chemistry Experiments on Air (Cavendish) – showing that air is oxygen and nitrogen in ratio 1:4 and water is formed of hydrogen and oxygen in ratio 2:1 Hauy discovers the geometrical law of crystallization 1782 Astronomy Goodricke proposes that Algol is an eclipsing binary Chemistry Hjelm discovers molybdenum Müller first isolates the element tellurium 1783 Chemistry Méthode de nomenclature chimique (Lavoisier and others) – proposes new names for elements Lavoisier experiments on formation of water from hydrogen and oxygen D. F. and J. J. D’Elhuyar discover tungsten Physics Saussure invents hair hygrometer Technology Cort patents method of rolling iron into bars using grooved rollers The Montgolfier brothers

demonstrate the first hot-air balloon on June 4 at Annonay In October the first manned flight in a hot-air balloon is made by François de Rozier in Paris 1784 Astronomy Messier publishes first nebula catalog Earth Science Elements of Mineralogy (Kirwan) Technology Cort patents dry-puddling process for converting pig iron into wrought iron 1785 Medicine Withering publishes a report on the use of the foxglove as a source of the drug digitalis Physics Coulomb publishes his inverse square law of electrical attraction and repulsion (Coulomb’s law) Technology Cartwright’s power loom is patented 1786 Astronomy Discovery of Encke’s Comet (orbit computed by Encke in 1819) 1787 Astronomy Herschel discovers Titania and Oberon (satellites of Uranus) Chemistry Hope isolates strontium Physics Charles discovers law governing change in volume of a gas with temperature (Charles’s law) 1788 Biology Linnean Society founded Chemistry Blagden discovers that lowering of freezing point of a solution is proportional to amount of solute (Blagden’s law) Earth Science Hutton first publishes his uniformitarian theory Physics Mécanique analytique (Lagrange) 1789 Astronomy (to 1790) Herschel discovers

Mimas and Enceladus (satellites of Saturn) Biology Genera Plantarum (Jussieu) – classification of plants Chemistry Klaproth discovers zirconium and uranium Traité élémentaire de chimie (Lavoisier) – states law of conservation of mass 1791 Biology Galvani publishes his findings in electrophysiology Chemistry Nicolas Leblanc patents his process for producing soda ash Gregor discovers titanium (not identified as new element until 1795 when isolated by Klaproth) Physics Prévost puts forward his theory of exchanges for heat 1794 Biology Young explains accommodation of the eye Medicine Dalton describes the condition of color blindness 1795 Chemistry Klaproth rediscovers titanium Earth Science Theory of the Earth (Hutton) 1796 Medicine Jenner first uses cowpox vaccine 1798 Biology An Essay on the Principle of Population (Malthus) Chemistry Klaproth discovers chromium Vauquelin discovers chromium and beryllium Physics Cavendish measures density of Earth by torsion-balance experiment Enquiry concerning the Source of Heat excited by Friction (Rumford) 1799 Astronomy (to 1825) Traité de mécanique céleste (Laplace) Chemistry Proust formulates his law of definite proportions

Mathematics Gauss’s proof of fundamental theorem of algebra 1799 General The Royal Institution is founded by Count Rumford at 21 Albemarle St., London 1800 Chemistry Nicholson discovers electrolysis Physics Volta invents voltaic pile – first battery 1801 Astronomy Piazzi discovers Ceres (first minor planet) Chemistry Del Rio discovers vanadium (rediscovered by Sefström in 1830) Dalton reads his paper on the constitution of gas mixtures, which contains the law of partial pressures Clément and Désormes discover carbon monoxide Hatchett discovers the element now known as niobium (originally named columbium) Henry formulates his law for the solubility of gases (Henry’s law) Earth Science Matthew Flinders sets sail in the Investigator to chart the coast of Australia Mathematics Disquisitiones arithmeticae (Gauss) Physics Ritter identifies ultraviolet radiation Wollaston shows that frictional and galvanic electricity are the same 1802 Astronomy Olbers discovers asteroid Pallas Chemistry Ekeberg discovers tantalum Dalton compiles his first table of atomic weights Gay-Lussac establishes GayLussac’s law Earth Science Illustrations of the Huttonian Theory (J. Playfair) – summarizes Hutton’s uniformitarian theory of the Earth

1803 Chemistry Klaproth discovers cerium oxide Hisinger and Berzelius discover cerium Dalton expounds his atomic theory (to 1804) S. Tennant discovers iridium and osmium Physics Young provides evidence for the wave nature of light by demonstrating interference using Young’s slits 1804 Chemistry Wollaston discovers palladium 1805 Chemistry Wollaston discovers rhodium Medicine Sertürner isolates morphine from opium 1806 Biochemistry Vauquelin isolates the first amino acid – asparagine Earth Science Beaufort proposes scale for wind speed (Beaufort scale) 1807 Astronomy Olbers discovers asteroid Vesta 1808 Biology (to 1813) American Ornithology (Wilson) Chemistry A New System of Chemical Philosophy (Dalton) Gay-Lussac formulates his law of combining volumes Physics Malus describes the polarization of light 1809 Biology Philosophie zoologique (Lamarck) – includes theory of evolution by inheritance of acquired characteristics Physics Chladni demonstrates the patterns (Chladni’s figures) formed by vibrations of a plate 1810 Chemistry Davy establishes that chlorine does not contain oxygen and is an element in its own right Physics Zur Farbenlehre (On the Science of Colors; Goethe)

1811 Biology New Idea of Anatomy of the Brain (Charles Bell) Chemistry Avogadro publishes the paper containing Avogadro’s hypothesis Courtois discovers iodine (published 1813) Dulong discovers nitrogen trichloride Earth Science Brongniart and Cuvier first identify rock strata by their fossil content Medicine Bell partly anticipates Magendie in showing functional differentiation of spinal nerve roots (Bell-Magendie law) but does not publish Physics Arago discovers chromatic polarization 1812 Earth Science Mohs introduces a scale of hardness for minerals (Mohs scale) Medicine Parkinson establishes perforation as the cause of death in appendicitis 1813 Biology Théorie élémentaire de la botanique (Candolle) – system of classifying plants Chemistry Clément and Désormes confirm Courtois’s discovery of iodine Physics Brewster formulates a law for polarization by reflection (Brewster’s law) 1814 Physics Fraunhofer observes absorption lines (Fraunhofer lines) in the solar spectrum 1815 Biology (to 1822) Natural History of Invertebrates (Lamarck) – reorganizes the classification of invertebrate animals Chemistry Biot shows that solutions (as well as solids) can show optical activity Prout suggests that the atomic weight of any atom is an exact multiple of the atomic weight

of hydrogen (Prout’s hypothesis) 1816 Chemistry The Davy lamp is produced Medicine Laënnec invents the stethoscope Technology Stirling invents the Stirling engine 1817 Biology Pelletier and Caventou discover chlorophyll Chemistry Strohmeyer discovers cadmium Berzelius discovers selenium (to 1820) Caventou and Pelletier isolate the alkaloids strychnine, brucine, cinchonine, quinine, veratrine, and colchicine Medicine Parkinson publishes his description of Parkinson’s disease 1818 Chemistry Discovery of lithium by J.A. Arfvedson 1819 Biology Chamisso discovers the alternation of generations in mollusks and tunicates Chemistry Mitscherlich formulates his law of isomorphism Dulong and Petit discover the law of atomic heats (Dulong and Petit’s law) Kidd and Garden obtain naphthalene from coal tar Physics Clément and Désormes publish paper on principal specific heats of gases 1820 Physics Arago demonstrates electromagnetic effect to French Academy of Sciences Oersted publishes his discovery of electromagnetism Schweigger invents multiplier (galvanometer) Ampère begins his work on electromagnetism Faraday begins work on electromagnetism 1821 Physics Faraday constructs simple electric motor

1822 Biology Magendie (and, earlier, Charles Bell) discovers that the roots of the anterior nerves of the spinal cord control motion, while the roots of the posterior nerves control sensation Mathematics Théorie analytique de chaleur (Fourier) – introduces the use of Fourier series Medicine Magendie publishes his work on alkaloids, introducing such compounds as morphine, strychnine, and quinine into medical practice Physics Latour discovers the critical state Seebeck discovers thermoelectric effect (Seebeck effect) 1823 Mathematics Babbage designs his analytical engine (computer) Technology Macintosh produces a flexible waterproof material 1824 Biology Flourens publishes his work demonstrating the major roles of different parts of the central nervous system Physics Réflexions sur la puissance motrice du feu (Carnot) – introduces Carnot cycle 1825 Chemistry Faraday discovers benzene Balard discovers bromine Medicine Bretonneau performs the first successful tracheotomy to treat diphtheria Physics Nobili invents astatic galvanometer Ampère deduces law for force between current-carrying conductors (Ampère’s law) Technology Stockton-Darlington railway opened (September 27) 1826 Astronomy Olbers proposes his paradox Discovery of Biela’s comet Biology Müller shows that sensory

nerves can only interpret stimuli in one way Chemistry Unverdorben synthesizes aniline (which he names crystalline) Mathematics Lobachevsky announces his non-Euclidean geometry Technology Niepce produces the first permanent camera photograph General Michael Faraday introduces the Christmas lectures for children at the Royal Institution, London. He also begins the Friday evening discourses, in which leading scientists speak about their work to Royal Institution members 1827 Biology Baer publishes his discovery of the mammalian ovum within the Graafian follicle (to 1838) Birds of America (Audubon) Chemistry Brownian motion first described, by Robert Brown Wöhler synthesizes aluminum Physics Ohm publishes his law relating current and voltage (Ohm’s law) Mémoires sur la théorie mathématique des phénomènes electrodynamiques uniquement déduite de l’expérience (Ampère) Technology Fourneyron constructs his first outward-flow turbine, a six-horsepower unit 1828 Chemistry Wöhler isolates beryllium Berzelius discovers thorium Wöhler synthesizes urea, the first organic compound to be synthesized from inorganic materials Physics Sturgeon constructs first electromagnet Invention of Nicol prism 1829 Chemistry Döbereiner formulates his law of triads Graham publishes a paper on the diffusion of gases, which

contains his law of diffusion (Graham’s law) Physics Nobili makes first thermopile Babinet first suggests that wavelengths of spectral lines could be used as standards of length Henry invents first practical electric motor 1830 Chemistry Sefström discovers vanadium Earth Science The Principles of Geology (Lyell) – establishes Hutton and J. Playfair’s uniformitarian theories Physics On the Improvement of Compound Microscopes (J. J. Lister) – showing how distortions can be reduced by use of achromatic lenses Technology Stephenson’s Rocket wins the Rainhill trials in England 1831 Biology Müller confirms the Bell-Magendie law distinguishing between motor and sensory nerves (to 1836) Expedition of HMS Beagle to South America, with Darwin aboard as naturalist Chemistry Guthrie and Soubeiran independently discover chloroform Physics Mellini and Nobili publish a description of a sensitive thermopile Experimental Researches in Electricity, 1st series (Faraday) Technology Philips patents the contact process for making sulfuric acid General The British Association for the Advancement of Science established in York, with Vernon Harcourt as its first chairman 1832 Astronomy Henderson measures parallax of Alpha Centauri (but does not publish until 1839) Biology Dutrochet demonstrates that gas exchange in plants is via the stomata

Gideon Algernon Mantell discovers the first armored dinosaur, Hylaeosaurus Mathematics Bolyai publishes his version of non-Euclidean geometry Galois outlines his ideas on group theory Medicine T. Hodgkin describes lymphadenoma (Hodgkin’s disease) Physics Faraday performs experiments on electromagnetic induction Henry discovers self-induction 1833 Medicine Observations on the Gastric Juice and the Physiology of Digestion (W. Beaumont) 1834 Chemistry Runge discovers quinoline Dumas and Peligot discover methyl alcohol (methanol) Physics Peltier demonstrates thermoelectric effect (Peltier effect) Lenz discovers law for magnetic induction (Lenz’s law) 1835 Biology Dujardin is able to refute the claim that microorganisms have the same organs as higher animals Earth Science Charpentier first presents his glaciation theory Physics Coriolis describes the inertial Coriolis force Henry develops the electric relay Technology Morse produces a working model of the electric telegraph 1836 Anthropology Lartet discovers fossil ancestors of the gibbon (Pliopithecus) Astronomy Baily observes Baily’s beads during total eclipse Biology Schwann and Cagniard de la Tour independently discover the role of yeast in alcoholic fermentation Schwann prepares the first precipitate of an enzyme (pepsin) from animal tissue

Chemistry The Daniell cell is introduced Gossage improves process for manufacture of alkali Physics Sturgeon designs moving-cell galvanometer and introduces commutator for electric motor 1837 Biology Purkinje locates the Purkinje cells in the brain Chemistry Boussingault begins his experiments proving that leguminous plants are capable of using atmospheric nitrogen Earth Science A System of Mineralogy (Dana) Mathematics Recherches sur la probabilité des jugements (Poisson) – introduces law of large numbers and Poisson distribution Technology Wheatstone and Cooke produce first practical telegraph system 1838 Astronomy Bessel announces detection of parallax of 61 Cygni – first determination of stellar distance Biochemistry Peligot and Bouchardat demonstrate glucose in the urine of diabetics Biology Beiträge zur Phytogenesis (Schleiden) – states that all structures of plants composed of cells or their derivatives Remak shows that nerves are not hollow tubes (to 1843) Flora of North America (A. Gray) 1839 Biology A Naturalist’s Voyage on the Beagle (Darwin) Purkinje discovers the Purkinje fibers in the heart Chemistry Mosander discovers lanthanum Technology Nasmyth designs the steam hammer Daguerre perfects the daguerreotype

1840 Chemistry Hess formulates the law of constant heat summation Schönbein discovers ozone Earth Science Etudes sur les glaciers (Agassiz) – postulates existence of ice ages General William Whewell introduces the terms ‘physicist’ and ‘scientist’ into the English language 1841 Earth Science Essai sur les glaciers (Charpentier) Technology Sir Joseph Whitworth first argues for a unified system of screw threads – the Whitworth system, which becomes the standard for British engineering 1842 Biology Naegeli publishes his observations on cell division during pollen formation, so disproving Schleiden’s theory of cell formation by budding off the nuclear surface Steenstrup publishes his observations of the alternation of generations in certain animals Bowman publishes his work on the Malpighian bodies of the kidneys, which includes a description of the structure and role of the Bowman’s capsules Medicine Braid suggests the use of hypnosis to treat pain, anxiety, and certain nervous disorders Physics Doppler discovers the Doppler effect for wave motions Mayer’s paper containing the law of conservation of energy is published 1843 Astronomy Schwabe announces discovery of sunspot cycle Biology Du Bois-Reymond shows that applying a stimulus to a nerve causes a drop in electrical potential at the point of stimulus Chemistry Mosander discovers erbium and terbium

Medicine Holmes publishes a paper on the contagious nature of puerperal fever General Women first admitted to membership of the British Association for the Advancement of Science 1844 Astronomy Bessel announces that Sirius is a double star system Biology Remak discovers ganglion cells in the heart Chemistry Gerhardt develops his type theory of organic compounds 1845 Astronomy J. C. Adams works out position of Neptune Biology (to 1848) Viviparous Quadrupeds of North America (Audubon) Chemistry Schröder discovers red phosphorus Physics Waterson’s paper on the kinetic theory of gases is rejected by the Royal Society Faraday discovers effect of magnetic field on polarized light (Faraday effect) Kirchhoff formulates his laws for electric circuits (Kirchhoff ’s laws) An Essay on the Application of Mathematics to Electricity and Magnetism (George Green), reissued by Lord Kelvin in Crelle’s Journal thus introducing Green’s theorem, Green’s function, and the notion of electric potential into science 1846 Astronomy Leverrier works out position of Neptune – discovered by Galle Lassell discovers Triton (satellite of Neptune) Harvard College Observatory founded with W. C. Bond as director at Cambridge, Massachusetts Biology Siebold and Stannius publish their textbook of comparative anatomy Hugo von Mohl coins the term protoplasm for the substance surrounding the cell nucleus

Chemistry Sobrero discovers nitroglycerine Schönbein discovers guncotton Earth Science Loomis publishes first synoptic weather map Medicine Morton demonstrates the use of ether inhalation to produce general anesthesia 1847 Biology The first volume of Antiquités celtiques et antédiluviennes (Boucher de Perthes) Ludwig invents the kymograph Chemistry Babo formulates his law for the depression of vapor pressure by a solute (Babo’s law) Medicine J. Y. Simpson introduces chloroform as an anesthetic in hospital operations Semmelweis discovers the nature of puerperal fever and implements a successful preventative policy Physics Über die Erhaltung der Kraft (Helmholtz) – develops the law of conservation of energy Kelvin draws an analogy between an electrostatic field and an incompressible elastic solid 1848 Astronomy W. C. Bond and G. Bond discover Hyperion (satellite of Saturn) Biology Kölliker isolates cells of smooth muscle (to 1854) Untersuchungen über tierische Elektricität (Du BoisReymond) – reports his work on nerve and muscle activity Chemistry Pasteur discovers molecular asymmetry (as cause of optical activity) Physics Joule publishes a paper on the kinetic theory of gases in which he makes the first estimate of the speed of gas molecules Kelvin introduces the absolute temperature scale General American Association for the Advancement of Science

founded with W. C. Redfield as its first president 1849 Chemistry Wurtz synthesizes ethylamine from ammonia Deville discovers nitrogen pentoxide Medicine Addison describes Addison’s disease Physics Fizeau measures the speed of light by a toothed-wheel method On the Mechanical Equivalent of Heat (Joule) 1850 Astronomy W. C. Bond makes first photograph of a star (Vega) and discovers third ring of Saturn (crepe ring) Roche proposes and calculates the Roche limit Lamont announces discovery of magnetic cycle of Earth Earth Science Mallet begins precise experiments to determine speed of earthquake waves Physics Fizeau and Foucault provide experimental support for the wave theory of light by measuring the speed in air and in water Über die bewegende Kraft der Wärme (Clausius) – first formulates the second law of thermodynamics 1851 Astronomy Lassell discovers Ariel and Umbriel (satellites of Uranus) Biology Helmholtz invents the ophthalmoscope Vergleichende Untersuchungen (Hofmeister) – describes discovery of alternation of generations in lower plants and similarities between seedbearing and non-seed-bearing plants Chemistry Thomas Anderson extracts pyridine from bone oil Physics Foucault uses pendulum to demonstrate rotation of Earth 1852 Chemistry Frankland originates the theory of valence

Mathematics Francis Guthrie first notices the map-coloring problem Physics Kelvin sets out the law of conservation of energy (to 1862) Joule and Kelvin investigate the Joule-Kelvin effect 1853 Aeronautics Cayley constructs the first successful man-carrying glider Chemistry Hittorf introduces idea of ionic mobility in electrolysis Cannizzaro discovers the reaction known as Cannizzaro’s reaction Mathematics Hamilton introduces quaternions 1854 Chemistry Berthelot synthesizes fats from glycerin and fatty acids Mathematics The Laws of Thought (Boole) Reimann puts forward his general formulation of Reimannian geometry 1855 Biology Pringsheim confirms the occurrence of sexuality in algae Chemistry Wurtz develops the Wurtz reaction for synthesizing hydrocarbons Deville develops a process for the large-scale production of aluminum 1856 Anthropology Lartet discovers fossil ancestor of apes (Dryopithecus) Biology Pasteur declares that fermentation is caused by living organisms Chemistry Perkin discovers first synthetic dye (mauveine) Medicine Brown-Séquard shows there is a connection between excising the adrenal glands and Addison’s disease Technology Bessemer announces his process for converting pig iron into steel Charles William Siemens and

Friedrich Siemens introduce the regenerator furnace 1857 Astronomy G. Bond shows how stellar magnitude may be calculated from photographs Earth Science Buys Ballot formulates law concerning wind direction 1858 Biology On the Tendency of Varieties to Depart Indefinitely from the Original Type (Wallace) Joint paper by Darwin and Wallace, outlining their theory of evolution by natural selection, read at meeting of Linnean Society Die Cellularpathologie (Virchow) Chemistry Kekulé publishes his paper on bonding in carbon compounds 1859 Astronomy (to 1862) Bonner Durchmusterung (Argelander) – survey of northern stars Biology On the Origin of Species by Means of Natural Selection (Darwin) Physics Tyndall discovers scattering by colloidal suspension (Tyndall effect) Planté invents Planté battery – the first storage battery 1860 Biology Oxford meeting of the British Association for the Advancement of Science, in which T. H. Huxley and others defend Darwin’s theory of evolution Chemistry Bunsen and Kirchhoff publish their paper on spectroscopy – spectroscopic methods enabled Bunsen to discover rubidium and cesium First meeting of the International Chemical Congress at Karlsruhe Graham distinguishes colloids c. 1860 Physics Illustrations of Dynamical Theory of Gases (Maxwell) Technology Lenoir takes out a patent for an internal combustion engine

1861 Astronomy A. G. Clark discovers Sirius B Schiaparelli discovers the asteroid Hesperia Biology H. W. Bates publishes his paper on Batesian mimicry in butterflies Gegenbaur shows that all vertebrate eggs and sperm are unicellular Chemistry Bunsen and Kirchhoff discover rubidium Crookes discovers thallium Technology Solvay patents his process for soda production Massachusetts Institute of Technology (MIT) founded in Boston with William Barton Rogers as its first president 1862 Biology (to 1883) Genera Plantarum (Bentham and Hooker) Chemistry Béguyer de Chancourtois proposes his periodic classification of the elements (telluric screw) 1863 Astronomy Huggins shows the stars to be composed of known elements Biology Helmholtz publishes his theory of hearing Chemistry Reich and Richter discover indium Earth Science Galton publishes his work on weather systems, outlining the modern technique of weather mapping Medicine Leuckart publishes the first volume of his work on the parasites of man Davaine shows that anthrax can be transmitted to healthy cattle by injecting them with the blood of diseased cattle Waldeyer establishes that cancer begins as a single cell General National Academy of Sciences created 1864 Astronomy Donati first observes spectrum of comet – discovers gaseous composition of tails

W. Huggins discovers some nebulae to be gaseous Chemistry Guldberg and Waage discover the law of mass action Newlands publishes his law of octaves Physics Dynamical Theory of the Electric Field (Maxwell) – contains Maxwell’s differential equations describing the propagation of electromagnetic waves 1865 Biology Sachs shows that chlorophyll is confined to discrete bodies – chloroplasts Chemistry Kekulé proposes a ring structure for benzene (to 1885) Baeyer researches indigo Zur Gross der Loftmolecule (On the Magnitude of Air Molecules; Loschmidt) Medicine Villemin shows that tuberculosis is contagious Physics Clausius introduces the term entropy as a measure of the availability of heat 1866 Astronomy Schiaparelli shows meteors follow cometary orbits Biology De Bary shows that a lichen is a close association between an alga and a fungus Mendel publishes the results of his plant-breeding experiments, summarized later as the law of segregation and the law of independent assortment His introduces the microtome Medicine Allbutt invents the short clinical thermometer Physics Kundt develops the Kundt tube to measure the speed of sound Technology Leclanché invents the electrical battery (dry cell) 1867 Biology Handbuch der physiologische Optik (Helmholtz) Medicine Cohnheim publishes his work on inflammation, disproving

Virchow’s theory that pus corpuscles originate at the point of wounding, and demonstrating that swelling is due to the passage of leukocytes from the veins into the wound Joseph Lister introduces the principles of antiseptic surgery into medicine Technology Nobel patents dynamite and the detonating cap in the UK 1868 Anthropology Lartet discovers remains of Cro-Magnon man Astronomy W. Huggins discovers red shift in spectrum of Sirius Lockyer identifies lines of helium in solar spectrum Medicine Wunderlich publishes his investigations into body temperature and disease, so introducing clinical thermometry as an important diagnostic technique 1869 Chemistry Mendeleev proposes his periodic table of the elements T. Andrews publishes his work on the liquefaction of gases, which includes the concept of critical temperature Caro, Graebe, and Liebermann synthesize alizarin, the first natural dye to be synthesized Medicine Joseph Lister uses catgut ligatures instead of silk 1870 Biology Hitzig and Fritsch publish a paper containing the first experimental evidence for cerebral localization Chemistry J. L. Meyer publishes his periodic classification of elements 1871 Biochemistry Miescher announces the discovery of nuclein (later renamed nucleic acid) in cell nuclei Biology Hoppe-Seyler discovers the enzyme invertase Ranvier describes the nodes of Ranvier The Descent of Man (Darwin)

1872 Astronomy H. Draper photographs first stellar spectrum (of Vega) Biology Untersuchungen über Bacterien (Cohn) – provides basis for modern bacterial nomenclature Chemistry Dewar devises the Dewar vacuum flask Wislicenus demonstrates geometrical isomerism in lactic acid Earth Science (to 1876) C. W. Thomson collects evidence for the presence of the Mid-Atlantic Ridge Medicine George Huntington describes Huntington’s chorea Physics E. Abbe invents Abbe condenser lens for microscopes Amagat experiments on behavior of gases at high pressures 1873 Biology Osler discovers the blood platelets Chemistry (to 1876) Gibbs develops the theory of chemical thermodynamics On the Continuity of the Liquid and Gaseous States (van der Waals) – includes the van der Waals equation Medicine Billroth performs first laryngectomy Hansen observes rod-shaped bacilli in the tissues of leprosy patients 1874 Chemistry A Suggestion Looking to the Extension into Space of the Structural Formulae at Present Used in Chemistry (van’t Hoff) – introduces idea of tetrahedral arrangement of bonds to carbon atom Lecoq de Boisbaudran discovers gallium Physics Braun discovers use of semiconducting crystals as rectifiers Technology A. G. Bell’s multiple telegraph is patented

General The Cavendish laboratory opens in Cambridge, England, with Clerk Maxwell as its first director 1876 Biology Geographical Distribution of Animals (Alfred Russell Wallace) Chemistry On the Equilibrium of Heterogeneous Substances (J. W. Gibbs) – work on chemical thermodynamics introducing phase rule Medicine Koch publishes the life cycle of the anthrax bacillus Technology A. G. Bell’s invention of the telephone is patented 1877 Astronomy A. Hall discovers Phobos and Deimos (satellites of Mars) Chemistry Friedel and Crafts discover the Friedel-Crafts reaction for the alkylation or acylation of aromatic hydrocarbons Medicine Manson demonstrates, from his investigations of elephantiasis, that certain diseases are transmitted by insects Physics Cailletet succeeds in producing liquid oxygen Technology Edison invents the phonograph 1878 Chemistry Marignac isolates ytterbium 1879 Biology De Bary coins the term symbiosis to describe the mutually beneficial association between two unrelated organisms Chemistry Cleve discovers thulium Lecoq de Boisbaudran discovers samarium Nilson discovers scandium Fahlberg discovers saccharin Medicine Neisser discovers the gonococcus responsible for gonorrhea Physics Stefan formulates law for heat

radiation (Stefan-Boltzmann law) Swan invents carbon-filament incandescent electric lamp Edwin Hall discovers the Hall effect Technology Edison demonstrates his electric light bulb The Thomas-Gilchrist steelmaking process is demonstrated 1880 Chemistry Skraup synthesizes quinoline Marignac discovers gadolinium Earth Science Milne invents seismograph Medicine Laveran discovers the causative agent of malaria – the Plasmodium parasite Physics P. Curie discovers piezoelectricity Technology Eadweard James Muybridge demonstrates the first moving picture in public using the ‘zoopraxiscope’ 1881 Biology T. W. Engelmann demonstrates chemotactic response of bacteria Medicine Finlay publishes a paper naming the mosquito as the vector of yellow fever Physics Ewing discovers hysteresis 1882 Biology Ants, Bees and Wasps (Lubbock) Zell-substanz, Kern und Zelltheilung (W. Flemming) Chemistry Raoult shows that the depression in freezing point of a solvent is proportional to the mass of substance dissolved divided by the substance’s molecular weight (Raoult’s rule) Earth Science Anthropogeographie (Ratzel, 2nd vol. 1891) – lays foundation for modern study of human geography Medicine Metchnikoff describes phagocytosis Pasteur produces an

attenuated vaccine for anthrax Koch discovers the bacillus responsible for tuberculosis Physics Ritter builds first dry voltaic pile Rowland designs diffraction grating for spectral photography 1883 Biology Galton coins the term eugenics Medicine Kocher demonstrates that operative myxedema (cretinism) following removal of the thyroid can be avoided by leaving a portion of the thyroid in the body Physics Wroblewski and Olszewski achieve liquefaction of large amounts of oxygen 1884 Biology Gram discovers the Gram stain Chemistry Chardonnet’s rayon, the world’s first artificial fiber, is patented Le Chatelier discovers Le Chatelier’s principle Tilden synthesizes isoprene, leading to the production of synthetic rubber Mathematics Die Grundlagen der Arithmetik (Frege) – defines cardinal number and derives properties of numbers Medicine Löffler isolates and cultivates the bacillus responsible for diphtheria Gaffky obtains a pure culture of the typhoid bacillus Koller publishes his experiments on the use of cocaine as a local anesthetic Physics Poynting introduces Poynting’s vector Technology Parsons invents the multistage steam turbine General The International Meridian Conference in Washington adopts a single prime meridian passing through the center of the transit instrument at the Royal Greenwich Observatory

1885 Biology Kossel isolates adenine from his newly discovered nucleic acids Chemistry Winkler discovers germanium Medicine Roux and Yersin show that diphtheria is caused by a toxin released from diphtheria bacteria Pasteur successfully uses a rabies vaccine to cure a rabies victim Physics Balmer discovers formula for series of lines in hydrogen spectrum (Balmer series) Technology Daimler patents the first internal-combustion engine 1886 Biology Eichler publishes his plant classification system Weismann publishes his theory of the continuity of the germ plasm Chemistry Beckmann discovers the Beckmann rearrangement in organic chemistry Moissan isolates fluorine gas C. M. Hall and Héroult independently discover a cheap process for extracting aluminum Lecoq de Boisbaudran discovers dysprosium Physics Boltzmann derives distribution law for energies of gas molecules (Maxwell-Boltzmann distribution) E. Abbe invents apochromatic lens system Goldstein discovers canal rays Technology Benz patents his threewheeled automobile, the first practical automobile powered by an internal-combustion engine 1887 Astronomy Paris Observatory organizes a congress that decides to construct the Carte du Ciel, a photographic map of the whole sky Biology Henson introduces the term plankton

Petri introduces the Petri dish for cultures Chemistry Arrhenius publishes his theory on ionic dissociation in solution Wallach characterizes the terpenes Physics Hertz discovers photoelectric effect Michelson and Morley attempt to detect the ether and obtain negative result (the Michelson-Morley experiment) (to 1888) Lodge discovers propagation of electromagnetic waves along conducting wires Technology Tesla invents the first alternating-current motor 1888 Astronomy New General Catalogue of Nebulae and Clusters of Stars (NGC) (Dreyer) Lick Observatory completed at a site on Mount Hamilton overlooking San José, California Chemistry Baeyer makes the first synthesis of a terpene Earth Science (to 1889) Nansen explores Greenland icecap Mathematics Was sind und was sollen die Zahlen (Dedekind) – the first formulation of the axioms of arithmetic Physics Hertz demonstrates propagation of electromagnetic waves (radio waves) Technology Eastman markets his handheld box camera 1889 Biology Pavlov shows the secretion of gastric juices is prompted by the sight of food Intracellular Pangenesis (de Vries) – the theory that hereditary traits are determined by ‘pangenes’ in the cell nucleus Chemistry F. A. Abel and J. Dewar introduce cordite

Mathematics Peano presents axioms of arithmetic Physics Sur les trois corps et les equations de la dynamique (Henri Poincaré) – discusses the three-body problem Technology Otto Lilienthal publishes Der Vogelflug als Grundlage der Fliegerkunst (Bird Flight as the Basis of Aviation) and builds his first model glider 1890 Astronomy Vogel discovers eclipsing binaries spectroscopically Biology Kitasato and von Behring announce the discovery of diphtheria and tetanus antitoxins Koch formulates Koch’s postulates for establishing that an organism is the cause of a disease Chemistry Guillaume begins work on nickel alloys (invar, elinvar) Beilby patents a process for the synthesis of potassium cyanide Commercial synthetic indigo is produced Computing Herman Hollerith invents a tabulating system using punched cards for the 1890 US census Medicine Grassi, Marchiafava, and Celli show there are a number of protozoan species that can produce malaria Physics Rydberg discovers formula for spectral-line frequencies, involving Rydberg constant 1891 Astronomy Chandler announces discovery of Earth’s Chandler wobble Biology Strasburger demonstrates that physiological rather than physical forces are responsible for the movement of liquids up the plant stem Chemistry E. H. Fischer deduces the configurations of the 16 possible aldohexose sugars Physics Poynting determines the mean density of the Earth

Stoney coins term electron Lippmann produces the first color photograph General The Throop Polytechnic Institute, the forerunner of the California Institute of Technology, is founded in Pasadena, California 1892 Astronomy E. E. Barnard discovers Amalthea (satellite of Jupiter) Biology Ivanovsky, working on tobacco mosaic disease, finds the first evidence of viruses Chemistry Bevan and Cross patent the viscose process of rayon manufacture Crum Brown and Gibson propose Crum Brown’s rule for substitution reactions of benzene compounds Medicine Welch discovers the bacterium that causes gas gangrene Physics (to 1904) Lorentz develops his electron theory 1893 Astronomy Maunder discovers Maunder minimum for sunspot activity Chemistry Kjeldahl develops the Kjeldahl method for determining the amount of nitrogen in organic compounds Mathematics (and 1903) Grundgesetze der Arithmetik (Frege) Physics Wien derives his displacement law for radiation from hot bodies Poynting determines the gravitational constant Technology Diesel demonstrates his first engine 1894 Biology Pfeiffer discovers bacteriolysis Rubner demonstrates that human energy production can be explained by thermodynamics Chemistry Ramsay and Rayleigh discover argon Sulfur is raised from deep underground by means of superheated water – the Frasch process

Medicine Yersin and Kitasato discover the bacterium responsible for bubonic plague Physics Lodge develops his coherer for detecting radio waves Technology Marconi begins experiments on communicating using radio waves 1895 Astronomy Keeler shows the rings of Saturn do not rotate uniformly Chemistry Ramsay and Crookes identify helium Medicine Bruce discovers the trypanosome parasite that causes sleeping sickness Physics Lorentz describes force (Lorentz force) on a moving charged particle in electromagnetic field P. Curie discovers transition temperature for change from ferromagnetic to paramagnetic behavior (Curie point) Röntgen discovers x-rays Psychology Studien über Hysterie (Freud) – beginning of psychoanalysis 1896 Biology The first observation of the fermentation of sugar by cellfree extracts of yeast, proving the process is purely chemical and does not require intact cells Schäfer and Oliver discover that injecting an extract from the adrenal gland increases blood pressure Chemistry Walden discovers the Walden inversion in organic substitution reactions Mathematics Jacques Salomon Hadamard sets out his proof of the prime number theorem (independently of Charles de la Vallée-Poussin) Physics Becquerel discovers radioactivity (in uranium salts) Wien derives a formula for the distribution of energy in

black-body radiation (Wien’s formula) Boltzmann introduces the equation relating entropy to probability Zeeman discovers splitting of spectral lines in magnetic field (Zeeman effect) Technology Marconi patent on radio telegraphy Popov in Russia experiments with radio communication Sperry invents the gyrocompass A plant using the Castner-Kellner process is opened at Niagara Falls General Alfred Nobel dies leaving a fortune and instructions in his will to set up the Nobel Foundation 1897 Astronomy Yerkes Observatory opened under the directorship of G. Hale at Williams Bay, Wisconsin Biology J. J. Abel isolates a physiologically active substance from the adrenal gland – adrenaline (epinephrine) Chemistry Sabatier demonstrates hydrogenation of organic compounds Medicine Ross identifies malaria parasites (plasmodia) in the bodies of Anopheles mosquitoes fed on blood from infected patients Eijkman discovers a cure for beriberi Physics Larmor predicts precession of electron orbits in atoms (Larmor precession) J. J. Thomson discovers the electron Boys determines the gravitational constant 1898 Biology Bordet discovers alexin (complement) Pflanzengeographie auf physiologischer Grundlage (Plant Geography Upon a Physiological Basis; Schimper) Löffler and Frosch demonstrate that viruses can cause diseases in animals

Golgi describes the Golgi apparatus Beijerinck coins the term filterable virus for the causative agent of tobacco mosaic disease Chemistry Lowry describes mutarotation of optically active compounds E. H. Fischer synthesizes purine Ramsay and Travers discover neon, krypton, and xenon Caro discovers Caro’s acid, a powerful oxidizing agent J. Dewar produces liquid hydrogen Medicine Grassi demonstrates that only the Anopheles species of mosquito can transmit malaria to humans Physics M. Curie discovers radium and polonium Townsend measures the charge of the electron 1899 Astronomy W. H. Pickering discovers Phoebe (satellite of Saturn) Chemistry Thiele proposes the idea of partial valence in chemical compounds J. Dewar produces solid hydrogen Physics Rutherford distinguishes alpha and beta rays in radioactivity Technology Marconi achieves first international radio transmission (England-France) 1900 Biology Correns rediscovers Mendel’s work and publishes his own work on crossing experiments confirming Mendel’s results Chemistry The discovery of the Grignard reagents Gomberg obtains triphenylmethyl – a stable free radical Tsvet develops the technique of adsorption analysis, which he later named chromatography Earth Science Oldham clearly identifies primary (P) and secondary (S)

seismic waves for the first time Köppen first formulates his climatic classification Mathematics Hilbert presents list of 23 research problems at International Congress of Mathematicians in Paris Medicine Leishman discovers the protozoan parasite causing kala-azar (now known as leishmaniasis) Grassi and Manson provide evidence that malaria is transmitted by mosquitoes Physics Debierne discovers actinium Rutherford discovers gamma radiation Dorn discovers that radium evolves radioactive gas (radon) Planck publishes paper giving theory of energy distribution in black-body radiation, introducing the idea of quantized energy transfer 1901 Biology Takamine achieves the first isolation and purification of a hormone (adrenaline) from a natural source Hopkins discovers the amino acid tryptophan J. N. Langley finds that extract from adrenal gland stimulates effect of sympathetic nervous system (to 1903) The Mutation Theory (de Vries) – proposes that new species evolve by genetic mutations Chemistry Demarçay discovers europium Earth Science (to 1909) Die Alpen im Eiszeitalter (Penck) – identification of four ice ages Medicine Einthoven develops the electrocardiogram Reed and Carroll establish that yellow fever is caused by a virus Physics Richardson formulates a law to explain the emission of electrons from hot surfaces Technology Marconi makes first transatlantic radio transmission

1902 Biology Landsteiner announces his discovery of the ABO bloodgroup system Bayliss and Starling discover the role of the hormone secretin in digestion Medicine Richet coins the term anaphylaxis to describe the reaction whereby a second injection of an antigen proves fatal Physics Heaviside (and Kennelly) propose the existence of the Kennelly-Heaviside layer in the upper atmosphere 1903 Astronomy Exploration of Cosmic Space by means of Reaction Devices (Tsiolkovsky) Chemistry Zsigmondy and Siedentopf invent the ultramicroscope Birkeland and Eyde develop their process of nitrogen fixation Physics Rutherford and Soddy publish account of radioactive series involving transmutation of elements Technology Wilbur Wright pilots the first powered flight on December 14; Orville Wright pilots the second flight on December 17 1904 Astronomy Moulton and Chamberlin formulate planetismal theory Hartmann finds first evidence of interstellar gas Solar observatory set up on Mount Wilson at the south end of the Sierra Madre range by G. E. Hale Chemistry Ramsay and Whytlaw-Gray codiscover niton (now known as radon) Medicine Aschoff describes inflammatory nodules in heart muscle (Aschoff ’s bodies) Physics Lorentz and Fitzgerald independently propose Lorentz-Fitzgerald contraction Lorentz publishes transformations for space and time coordinates between

frames of reference (Lorentz transformations) J. A. Fleming invents thermionic vacuum tube Barkla observes the polarization of x-rays 1905 Biology Optima and Limiting Factors (Blackman) Elements of Heredity (Johannsen) J. S. Haldane and J. G. Priestley demonstrate the role of carbon dioxide in the regulation of breathing Johannsen introduces the terms genotype and phenotype (to 1909) Lucas formulates allor-none law of nervous stimulation (to 1915) Willstätter works out formulae of chlorophylls a and b Chemistry Goldschmidt introduces his method for the reduction of metallic oxides to metals – the Thermit process Earth Science On the Influence of the Earth’s Rotation on Ocean Currents (Ekman) Medicine Schaudinn and Hoffmann isolate the spirochete that causes syphilis Physics Boltwood demonstrates that lead is final product of uranium decay Rutherford and Soddy publish theory of nuclear transmutation Einstein publishes papers on Brownian motion, the photoelectric effect, and special relativity; relates mass and energy (E = mc2) 1906 Biology The Integrative Action of the Nervous System (Sherrington) (to 1907) Hopkins shows that a diet of proteins, carbohydrates, fats, and salts will not support growth in mice and postulates other essential accessory substances (later to be called vitamins) in the normal diet Chemistry Tsvet coins the term chromatograph for the analytic procedure he developed to separate plant pigments

Earth Science Oldham provides evidence that the Earth has a central core Medicine Wasserman develops a test to diagnose syphilis (the Wasserman test) Physics Nernst formulates the Nernst heat theorem (third law of thermodynamics) Lyman series identified in hydrogen spectrum Technology First music and speech broadcast in America (transmitted on Christmas Eve by Fessenden) 1907 Biology Hopkins and Fletcher demonstrate that lactic acid accumulates in working muscle Harrison develops the technique of tissue culture Chemistry Urbain discovers lutetium (to 1909) Haber demonstrates his process for synthesizing ammonia from nitrogen and hydrogen Medicine Alois Alzheimer diagnoses Alzheimer’s disease Physics Minkowski puts forward concept of 4-dimensional space-time Technology De Forest patents the Audion tube 1908 Astronomy Hale finds first extraterrestrial magnetic field in sunspots Henrietta Leavitt shows that cepheid variables can be used to estimate stellar distances Biology Inborn Errors of Metabolism (Garrod) – introduces the idea of genetic diseases Hardy and Weinberg discover Hardy-Weinberg law Medicine Landsteiner manages to transmit polio from humans to monkeys Physics Kamerlingh-Onnes succeeds in liquefying helium Perrin confirms experimentally Einstein’s

predictions concerning Brownian motion Technology Wilbur Wright first demonstrates powered flight publicly at Le Mans in August; Orville Wright gives a demonstration a few days later at Fort Meyer, Virginia 1909 Biology Ricketts describes the microorganism causing Rocky Mountain spotted fever – an organism intermediate between a bacterium and a virus Correns obtains the first evidence for cytoplasmic inheritance Johannsen introduces the term genes to describe Mendel’s factors of inheritance Chemistry Levene shows that the carbohydrate in yeast nucleic acid is the pentose sugar ribose Bakelite is invented by Baekeland Earth Science Mohorovičić discovers discontinuity between Earth’s mantle and crust (Mohorovičić discontinuity) Charles Dolittle Walcott discovers the Burgess Shale fossils Medicine Nicolle discovers that typhus is carried by the louse Physics Millikan starts series of experiments to determine the charge on the electron 1910 Geology The California Earthquake of April 19, 1906 (Harry Fielding Reid) – formulates the elastic rebound theory Mathematics (to 1913) Principia Mathematica (B. Russell and Whitehead) Medicine Ehrlich finds a chemical – Salvarsan – effective in treating syphilis Psychology Formation of the International Psycho-Analytical Association Technology Claude introduces neon lighting

1911 Biology Krogh shows that movement of oxygen from the lungs is by simple diffusion (no active secretion is involved) T. H. Morgan and colleagues produce the first chromosome maps Medicine Rous shows that cancer in chickens can be transmitted by a virus Physics C. T. R. Wilson invents cloud chamber Rutherford proposes nuclear model of the atom Kamerlingh-Onnes discovers superconductivity (to 1912) V. F. Hess discovers cosmic rays Einstein predicts gravitational field should deflect light General The Kaiser Wilhelm Gesselschaft founded in the Dahlem suburb of Berlin under the directorship of the historian Adolf von Harnack – the forerunner of the Max Planck Institute 1912 Anthropology A. S. Woodward and Dawson find Piltdown man Astronomy Slipher measures velocity of Andromeda Leavitt discovers period-luminosity relation of Cepheid variables Biology Funk suggests that certain diseases are caused by deficiencies of certain ingredients (vitamins) from the diet Physics Von Laue discovers x-ray diffraction by crystals W. L. Bragg formulates Bragg’s law for x-ray diffraction 1913 Astronomy H. N. Russell publishes Hertzsprung-Russell diagram Biology Michaelis and Menten propose the Michaelis-Menten equation to describe the variation in rate found when an enzyme acts on a substrate Sturtevant publishes a linkage map constructed from

data on recombinant frequencies in Drosophila Earth Science Gutenberg identifies the Earth’s core as being liquid from seismological evidence A. Holmes proposes the first quantitative geological time scale Physics Soddy proposes existence of isotopes Stark discovers splitting of spectral lines in strong electric field (Stark effect) On the Constitution of Atoms and Molecules (N. Bohr) – introduces his quantum theory of the atom and atomic spectra Moseley demonstrates characteristic x-ray wavelengths of elements depend on squares of atomic number plus a constant (Moseley’s law) Fajans proposes laws governing products of radioactive decay (independently of Soddy) 1914 Astronomy Nicholson discovers Sinope (satellite of Jupiter) W. S. Adams investigates spectra of stars; leading to stellar parallax method of finding distances Biology Ewins and Dale isolate acetylcholine from ergot Kendall isolates the active ingredient of the thyroid gland Medicine Respiratory Function of the Blood (Barcroft) Physics Frank and G. Hertz demonstrate quantized nature of energy transfer 1915 Astronomy Shapley proposes disk-shaped structure for Galaxy W. S. Adams identifies first white dwarf (Sirius B) Einstein and Grossmann explain advance in the perihelion of Mercury Biology D’Herelle and Twort independently discover the bacteriophage Chemistry Debye gives theory of electron diffraction by gases

Earth Science Die Enstehung der Kontinente und Ozeane (Wegener) – postulates original supercontinent of Pangaea and idea of continental drift Mathematics Fisher describes a solution for the exact distribution of the correlation coefficient in statistics Physics W. H. Bragg constructs first xray spectrometer 1916 Astronomy E. E. Barnard discovers Barnard’s star Schwarzschild introduces the idea of the Schwarzschild radius Biology The Involuntary Nervous System (Gaskell) Physics Sommerfeld proposes elliptical orbits for electrons in atoms N. Bohr formulates correspondence principle Einstein publishes general theory of relativity 1917 Astronomy De Sitter proposes a mathematical model of the universe (de Sitter universe) The 100-inch reflector first used at the Mount Wilson Observatory Chemistry Meitner and Hahn discover protactinium Physics Chapman predicts phenomenon of thermal diffusion of gases 1918 Astronomy 100-inch Hooker telescope in operation at Mount Wilson (largest until 1948) (to 1924) Henry Draper Catalogue (E. C. Pickering and A. Cannon) – records spectra of stars Biology The Correlation between Relatives on the Supposition of Mendelian Inheritance (Fisher) – demonstrates that continuous variations are inherited in Mendelian fashion Meyerhof investigates cellular metabolism – leads to

discovery of Embden-Meyerhof pathway 1919 Astronomy Eddington reports results of observations during solar eclipse, verifying bending of light passing close to Sun, as predicted by general theory of relativity Physics Aston produces his first mass spectrograph Barkhausen discovers that magnetization tends to occur in discrete steps Rutherford identifies first artificial transmutation of a nucleus 1920 Astronomy Baade discovers the asteroid Hidalgo Saha publishes the equation for degree of ionization of atoms in stars Mathematics Thoralf Albert Skolem contributes to the Lowenheim-Skolem theorem and constructs the Skolem paradox inset theory Medicine Goldberger finds a cure for pellagra Physics O. Stern confirms experimentally the phenomenon of space quantization General The Throop Polytechnic Institute in Pasadena, California, is renamed the California Institute of Technology c. 1920 Biology (to c. 1925) Keilin discovers cytochrome 1921 Biology Banting and Best isolate insulin and show its effectiveness in treating diabetes Loewi discovers that chemicals are released from nerve endings when the nerve is stimulated Chemistry Midgley discovers tetraethyl lead as an antiknock additive for fuel Earth Science On the Dynamics of the

Circular Vortex with Applications to the Atmospheric Vortex and Wave Motion (V. Bjerknes) Physics Hahn defines nuclear isomerism Theodor Franz Eduard Kaluza supplements Einstein’s 4dimensional space-time model with a fifth dimension 1922 Biology A. Fleming publishes his discovery of lysozyme Hopkins isolates glutathione Chemistry Kraus develops processes for the commercial production of tetraethyl lead Heyrovský describes polarography Earth Science Weather Prediction by Numerical Process (Richardson) – the first attempt to apply mathematical techniques to weather prediction Physics Friedmann publishes his paper on the expanding universe Technology Sabine publishes his papers on architectural acoustics 1923 Astronomy Wolf devises Wolf diagram for dark nebulae Biology Conant shows that oxyhemoglobin contains ferrous iron Euler-Chelpin works out the structure of the yeast coenzyme Heidelberger and Avery show that certain polysaccharides in the capsules of pneumococci are responsible for specific antigenic properties Hevesy makes first application of a radioactive tracer – 212Pb – to a biological system Whipple reports that liver in the diet increases hemoglobin production Warburg designs instrument (Warburg manometer) to measure uptake of oxygen by human tissue Chemistry Lowry and Brønsted independently formulate a

theory of acids and bases (the Lowry-Brønsted theory) Valence and the Structure of Atoms and Molecules (G. N. Lewis) – proposes octet theory of valence Hevesy and Coster discover hafnium Debye and Huckel publish their theory of electrolytes Physics Zworykin constructs the first iconoscope Compton discovers scattering effect of radiation by electrons (Compton effect) 1924 Archeology Dart describes the Taung skull Astronomy Eddington introduces mass-luminosity relationship for stars Biology Berger makes the first human encephalogram Chemistry Svedberg introduces the ultracentrifuge as a technique for investigating the molecular weights of very large molecules Earth Science The Earth: its Origin, History, and Physical Constitution (Jeffreys) Mathematics Banach and Tarski prove the Banach-Tarski paradox Physics Pauli proposes his exclusion principle De Broglie proposes that particles can behave as waves Appleton establishes experimentally the presence of the Heaviside-Kennelly layer 1925 Astronomy The Draper Extension first published by Harvard College Observatory, Massachusetts Biology Adrian finds that nerve messages are relayed by changes in the frequency of the discharge Chemistry Nieuwland polymerizes acetylene to give divinylacetylene Physics Giauque introduces the method of adiabatic demagnetization for low temperatures

Goudsmit and Uhlenbeck propose electron spin Tuve and Breit use pulseranging to determine the height of the ionosphere Heisenberg formulates matrix mechanics Born and Jordan develop matrix mechanics Auger discovers that an excited atom can emit an electron in reverting to a lower energy state (Auger effect) (to 1926) Schrödinger develops wave mechanics c. 1925 Biology Hecht formulates photochemical theory of visual adaptation 1926 Astronomy The Internal Constitution of the Stars (Eddington) Hubble publishes Hubble’s classification of galaxies Lindblad proposes rotation of Galaxy Biology Introduction to Experimental Biology (de Beer) – disproves germ-layer theory Windaus discovers that ergosterol is a precursor of vitamin D Sumner achieves the first isolation of a pure enzyme (urease) and shows it to be a protein J. J. Abel announces the crystallization of insulin H. J. Muller discovers that xrays can induce mutations Chemistry I. Noddack, W. Noddack, and O. Berg discover rhenium Ingold introduces the concept of mesomerism Medicine Minot and Murphy discover a cure for pernicious anemia Physics Oskar Klein revises Kaluza’s theory of a fifth dimension by formulating the Kaluza-Klein theory Technology Goddard launches first successful liquid-fuel rocket flight Baird demonstrates his apparatus for transmitting images

1927 Astronomy Lemaître provides cosmological model of expanding universe Oort confirms galactic rotation Biology Landsteiner discovers the MN and the P blood-group systems Chemistry Electronic Theory of Valency (Sidgwick) Medicine Stokes manages to transmit yellow fever to the rhesus monkey Physics Wigner introduces parity as a conserved property of nuclear reactions G. Thomson and (independently) Davisson and Germer demonstrate wave property (diffraction) of electrons N. Bohr formulates complementarity principle Heisenberg formulates his uncertainty principle (to 1932) Fock and Hartree show how Schrödinger’s wave equation can be applied to atoms with more than one electron Psychology Practice and Theory of Individual Psychology (Adler) 1928 Astronomy Ira Bowen explains forbidden emission lines in spectra of nebulae Biology Riddle isolates prolactin Griffith discovers bacterial transformation in pneumococci Medicine A. Fleming discovers penicillin Physics Geiger-Müller counter invented Dirac introduces relativity into the Schrödinger wave equations to account for electron spin Raman discovers Raman scattering effect Ernst August Friedrich Ruska produces the first electron microscope 1929 Astronomy Struve shows interstellar matter exists throughout Galaxy

Hubble announces his law that the recessional velocity of galaxies is proportional to their distance (Hubble’s law) Biology Butenandt isolates the first pure sex hormone, estrone Edward Adelbert Doisy isolates the hormone oestrone and soon afterwards, oestradiol (to 1931) Barbara McClintock establishes linkage groups in maize Chemistry Paneth demonstrates the existence of the methyl radical Levene identifies the carbohydrate in thymus nucleic acid as deoxyribose The Constitution of the Sugars (Haworth) – introduces the idea that sugar molecules can exist in ring form H. Fischer synthesizes hemin Eyring and Polyani calculate potential-energy surface for a chemical reaction – Eyring later develops absolute-rate theory of reaction rates Earth Science A. Holmes proposes his convection-current theory to explain continental drift On the Direction of Magnetization of Basalt (Matuyama) – discovery of remnant magnetization Medicine Forssman introduces the technique of cardiac catheterization Physics Bothe uses coincidence method to show cosmic rays are particles (to 1933) Rabi invents the atomic-and molecular-beam magnetic-resonance method 1930 Aeronautics B. N. Wallis invents the geodetic construction Astronomy Tombaugh discovers Pluto Trumpler discovers interstellar absorption Lyot invents the coronagraph Biology Karrer determines the structure of carotene Physics Lawrence begins to construct cyclic particle accelerator (cyclotron) Pauli suggests the existence of the neutrino

Dirac proposes negative energy states for the electron, which led subsequently to the appreciation of antimatter Néel proposes the existence of antiferromagnetism 1931 Biology Goodpasture introduces the method of culturing viruses in fertile eggs Karrer determines the structure of, and synthesizes, vitamin A C. Stern provides experimental evidence for crossing-over between homologous chromosomes Chemistry Carothers produces the first synthetic rubber (neoprene) Urey discovers heavy water (deuterium oxide) Mathematics Gödel proves incompleteness of arithmetic Physics Van de Graaf builds his highvoltage electrostatic generator 1932 Astronomy Jansky publishes his discovery of radio interference from the stars, so founding the new field of radio astronomy Biology J. B. S. Haldane makes the first estimate of mutation rates in humans Krebs and Henselheit introduce the urea cycle King and Szent-Györgi announce their (independent) isolations of vitamin C Chemistry Pauling introduces the idea of resonance hybrids Bergmann discovers the carbobenzoxy method of peptide synthesis Physics Chadwick discovers the neutron Anderson discovers the positron Cockcroft and Walton achieve first artificial nuclear transformation 1933 Biology King determines the formula of vitamin C The first synthesis of a vitamin, vitamin C, by Haworth and Hirst Brachet demonstrates that

both DNA and RNA occur in animal and in plant cells Bernal obtains the first x-ray photograph of a single-crystal protein Mathematics The Foundations of the Theory of Probability (Kolmogorov) Physics Anderson discovers the muon Occhialini and Blackett obtain cloud-chamber tracks of the positron Fermi proposes weak interaction as one of fundamental interactions in physics Walther Meissner and R. Oschenfeld discover the Meissner effect, now used as a routine test for superconductivity General Institute for Advanced Study opens in Princeton, New Jersey 1934 Biology R. R. Williams works out the formula of vitamin B1 Ružička is the first to synthesize a sex hormone, androsterone (to 1935) Theorell gives the first detailed account of enzyme action Chemistry Oliphant and Harteck produce the hydrogen isotope tritium Earth Science (to 1939) On Seismic Waves (Gutenberg and Richter) Physics Casimir and Gorter advance a two-fluid model of superconductivity Cherenkov discovers radiation from fast particles (Cherenkov radiation) Fermi discovers that slow neutrons more readily interact with nuclei Noddack anticipates Frisch in suggesting the hypothesis of nuclear fission I. and P. Joliot-Curie discover artificial radioactivity Goldhaber and Chadwick discover the nuclear photoelectric effect 1935 Biology Dam discovers vitamin K Stanley crystallizes the tobacco mosaic virus and demonstrates the retention of infectivity after crystallization

Von Euler isolates the first of the prostaglandins Chemistry Carothers produces nylon Earth Science Seismological Tables (Jeffreys and Bullen) Richter develops scale for earthquake magnitudes (Richter scale) Mathematics The Concept of Truth in Formalized Languages (Tarski) Medicine Egas Moniz introduces the operation of prefrontal leukotomy Domagk reports on the effectiveness of prontosil against streptococcal infection Physics Yukawa predicts the existence of the pion Can Quantum Mechanical Description of Physical Reality be Considered Complete? (Albert Einstein, Boris Podolsky, and Nathan Rosen) Technology The Detection of Aircraft by Radio Methods (Watson-Watt) 1936 Biology Kuhn synthesizes vitamin B6 Rose discovers the first essential amino acid – threonine Experimentelle Beiträge zu einer Theorie der Entwicklung (Spemann) Dale demonstrates that acetylcholine is released at motor-nerve endings of voluntary muscle Computers Konrad Zuse invents the computer ‘out of laziness’ Earth Science Daly suggests existence of turbidity currents in oceans Physics Wigner and Breit work out the Breit-Wigner formula Mueller invents the fieldemission microscope The Structure of Metals and Alloys (William Hume Rothery) 1937 Biology Gorer discovers the histocompatibility antigens and establishes their control at the genetic level

Williams synthesizes vitamin B1 Electrical Signs of Nervous Activity (Erlander and Gasser) Bawden and Pirie demonstrate that tobacco mosaic virus contains RNA Blakeslee discovers that colchicine induces multiple sets of chromosomes in plants Krebs discovers the tricarboxylic acid cycle (Krebs cycle) Genetics and the Origin of Species (Dobzhansky) Sonneborn discovers sexuality in the protozoa Chemistry Segrè discovers technetium Computers George Robert Stibitz builds his first calculator Earth Science Our Wandering Continents (Du Toit) – suggests separation of Pangaea into Laurasia and Gondwanaland Mathematics On Computable Numbers (Alan Turing) Medicine Bovet develops the antihistamine drug 933F Theiler and Smith announce the development of a vaccine against yellow fever Elvehjem shows active ingredient in pellagrapreventive factor is nicotinic acid Physics Frank and Tamm explain Cherenkov radiation Kapitza discovers the superfluidity of helium Technology Chester Floyd Carlson and Otto Kornei make the first electrostatic (xerographic) copier 1938 Astronomy Nicholson discovers Lysithea and Carme (satellites of Jupiter) Hahn discovers nuclear fission (interpreted by Meitner and Frisch) Physics Alvarez describes K-capture Technology Ladislao and Georg Biró patent the ballpoint pen 1939 Astronomy Introduction to the Study of

Stellar Structure (Chandrasekhar) – introduces idea of Chandrasekhar limit Biology Dam and Karrer isolate vitamin K Doisy synthesizes and characterizes vitamin K Chemistry The Nature of the Chemical Bond (Pauling) Perey discovers francium Earth Science Bergeron-Findeisen theory of precipitation Medicine Ewin’s research team develops the drug sulfapyridine Dubos discovers the antibiotic tyrothricin Florey and Chain extract penicillin Physics Energy Production in Stars (Bethe) Meitner and O. Frisch interpret Hahn’s experiments as evidence of nuclear fission Meitner announces the discovery of light nuclei (fission products) following neutron bombardment of uranium nuclei Luis Walter Alvarez and Felix Bloch make the first measurement of the magnetic moment of the neutron Alvarez demonstrates that tritium is radioactive Boot and Randall develop the cavity magnetron Technology The first jet flight is powered by an engine designed by Hans Joachim Pabst von Ohain 1940 Astronomy Reber publishes first radio map of sky Biology Landsteiner announces his discovery of the rhesus factor Chemistry McMillan and Abelson discover the first transuranic element – neptunium Patent taken out on the insecticide DDT (P. H. Müller) Kamen and Ruben discover the radioisotope carbon-14 Earth Science Rossby discovers long sinusoidal atmospheric waves of large amplitude (Rossby waves)

Physics Hillier builds the first successful American highresolution electron microscope (to 1950) Development of modern theory of quantum electrodynamics by Feynman, Schwinger, and Tomonaga (independently) 1941 Aeronautics The jet engine, designed by Whittle and fitted to a Gloster E28/39 aircraft, makes its first flight (May 15) Astronomy Edlen shows ‘coronium’ to be highly ionized heavy atoms Chemistry Martin and Synge develop partition chromatography Medicine Cournand and Ranges develop cardiac catheterization C. B. Huggins pioneers the use of female sex hormones in treating cancer of the prostate gland Physics (to 1943) Tomonaga develops a quantum field theory consistent with the theory of special relativity 1942 Biology Brachet suggests RNA granules might be the agents of protein synthesis (to 1953) K. E. Bloch and others determine biosynthesis of cholesterol Computers John Vincent Atanasoff and Clifford Berry complete the Atanasoff-Berry Computer (ABC) Earth Science Belousov suggests that Earth movements caused by density of crust Physics First self-supporting nuclearfission chain reaction (Stagg Field, Chicago) Alfvén postulates hydromagnetic waves (Alfvén waves) in plasmas 1943 Astronomy MKK system of stellar classification introduced (by W. W. Morgan, Keenan, and Kellman) Seyfert discovers Seyfert galaxies

Baade introduces Populations I and II classification of stars Biology Luria and Delbrück demonstrate spontaneous mutation in bacteria B. Chance provides experimental evidence for the formation of an enzyme-substrate complex, as proposed by Michaelis Waksman isolates streptomycin from the mold Streptomyces griseus Chemistry Longuett-Higgins suggests that borane contains hydrogen bridges Computers Howard Hathaway Aiken completes the Harvard Mark I or ASCC (Automatic Sequence Controlled Calculator) Technology Luis Walter Alvarez guides a distant plane to land using radar 1944 Biology An artificially produced plant species Ehrharta erecta is established in a natural environment MacLeod, Avery, and McCarty provide evidence that DNA is responsible for bacterial transformation Wyckoff and R. C. Williams develop the metal-shadowing technique to give threedimensional photographs with the electron microscope What is Life? (Schrödinger) Earth Science Principles of Physical Geography (A. Holmes) Physics Veksler invents synchrocyclotron 1945 Biology Beadle and Tatum formulate the one gene-one enzyme hypothesis Alfred Day Hershey demonstrates (independently of Salvador Edward Luria) spontaneous mutations in bacteriophages Computers Mauchly and Eckert complete ENIAC (Electronic Numerator Integrator and Calculator) Physics Atomic bomb first tested (July 16)

General Studies in the Logic of Confirmation (Carl Gustav Hempel) – challenges the foundations of inductive logic 1946 Astronomy Tousey photographs the solar spectrum from above the ozone layer Biology Delbrück and Hershey demonstrate genetic recombination in viruses Von Euler isolates noradrenaline (norepinephrine) Tatum and Lederberg demonstrate occurrence of sexual reproduction in bacteria Cohen introduces radioactive labeling of microorganisms Earth Science Schaefer seeds clouds and produces the first artificial rainfall Physics Bloch and Purcell independently introduce the technique of nuclear magnetic resonance General The Kaiser Wilhelm Gesselschaft in Berlin is renamed the Max Planck Institute 1947 Astronomy Bok discovers Bok globules Ambartsumian introduces idea of stellar association Biology Lipmann discovers coenzyme A Todd synthesizes ADP and ATP Chemistry Libby develops the radiocarbon dating technique Physics Kusch measures the magnetic moment of the electron and finds a discrepancy between the experimental and theoretical values Brattain, Bardeen, and Shockley invent the pointcontact transistor Lamb announces the Lamb shift Occhialini and Powell observe tracks of the pion

1948 Anthropology Sexual Behavior in the Human Male (Kinsey) Astronomy Burnright detects solar x-rays H. D. and H. W. Babcock develop magnetograph and detect solar and stellar magnetic fields Alpher, Bethe, and Gamow publish theory on origin of elements Alpher and Herman first predict cosmic background radiation from big bang The Steady-State Theory of the Expanding Universe (Gold and Bondi) Kniper discovers Miranda (satellite of Uranus) 200-inch Hale telescope in operation at Mount Palomar (largest until 1977) Biology Folkers isolates vitamin B12 The Functional Organization of the Diencephalon (W. H. Hess) Medicine Weller and Neva succeed in growing the rubella virus in tissue culture Duggar discovers chlortetracycline (Aureomycin), the first tetracycline antibiotic Hench introduces cortisone to treat rheumatoid arthritis Physics Shockley develops the junction transistor Gabor invents the technique of holography Richard Feynman’s paper Space-Time Approach to NonRelativistic Quantum Mechanics, in which he introduces path integrals, is turned down by Physical Review General Studies in the Logic of Explanation (Carl Gustav Hempel and Paul Openheim) – proposes the HypotheticoDeductive method 1949 Astronomy Kniper discovers Nereid (satellite of Neptune) Baade discovers asteroid Icarus Biology Enders, Weller, and Robbins cultivate polio virus in vitro on human embryonic tissue

Sir Frank Macfarlane Burnet postulates that immunological tolerance has not yet developed in the embryo stage Murray Llewellyn Barr with Ewart Bertram discover Barr bodies in female somatic cells Chemistry G. Porter and Norrish begin developing methods of flash photolysis Computers Maurice Wilkes builds EDSAC, the first working computer with a stored program Mathematics A Mathematical Theory of Communication (Shannon and Weaver) Medicine Burnet discovers the phenomenon of acquired immunologic tolerance Physics Shull demonstrates antiferromagnetism using neutron diffraction Space-Time Approach to Quantum Electrodynamics (Richard Feynman) – introduces use of Feynman diagrams 1950 Astronomy The Nature of the Universe (Hoyle) Oort proposes comets originate from reservoir far out in solar system (Oort’s cloud) Whipple proposes icy-nucleus theory of comets R. H. Brown plots the first radio map of an external galaxy Biology Pontecorvo and Roper discover the parasexual cycle in fungi Chargaff announces base ratios of DNA, important in the construction of Watson-Crick model of DNA (to 1952) Harris shows that release of pituitary hormones is controlled by the hypothalamus Computers Computing Machinery and Intelligence (Alan Turing) Physics The betatron at the University of Illinois is completed Rainwater suggests his modification to the shell model of nuclear structure (to 1953) Mottelson and A.