1875 in science

Chemistry

• Gallium is discovered spectroscopically by French chemist Paul Emile Lecoq de Boisbaudran. Later in this year he obtains the free metal by electrolysis of its hydroxide and names it. This is the first of Dmitri Mendeleev's predicted elements to be identified.
• Phenylhydrazine is discovered by Hermann Emil Fischer.

  Earth sciences

• March – Challenger expedition first records Challenger Deep.

  Genetics

• Francis Galton publishes The History of Twins, as a criterion of the relative powers of nature and nurture.

  Medicine

• The weekly medical journal, Deutsche Medizinische Wochenschrift, is established in Germany by Paul Börner.

  Metrology

• May 20 – International Bureau of Weights and Measures established by signature of the Metre Convention in Paris.

  Technology

• May 25 – Romanian inventor Petrache Poenaru is granted a French patent for a fountain pen.

  Awards

• Copley Medal: August Wilhelm Hofmann
• Wollaston Medal for geology: Laurent-Guillaume de Koninck

  Births

• January 10 – Issai Schur, Belarusian-born Jewish mathematician
• January 14 – Albert Schweitzer, German-born French medical missionary
• February 4 – Ludwig Prandtl, German physicist
• March 14 – Fran Jesenko, Slovene botanist and plant geneticist
• June 20 – Reginald Punnett, English geneticist
• June 28 – Henri Lebesgue, French mathematician
• July 26 – Carl Jung, Swiss psychiatrist
• September 11 – Edith Humphrey, English chemist
• October 23 – Gilbert N. Lewis, American chemist; first to isolate deuterium
• November 12 – Stanislaus von Prowazek, born Stanislav Provázek, Bohemian parasitologist

  Deaths

• February 22 – Charles Lyell, Scottish-born geologist
• February 28 – Robert Willis, English mechanical engineer, phonetician and architectural historian
• March 7 – John Edward Gray, English taxonomist
• March 31 – Friedrich Julius Richelot, German mathematician
• April 11 – Heinrich Schwabe, German astronomer
• October 19 – Charles Wheatstone, English inventor
• November 27 – Richard Carrington, English astronomer
• Undated – Petrache Poenaru, Romanian inventor