Julius Robert Mayer
(1814 - 1878)
after 1867: Julius Robert von Mayer

born: November 25, 1814 in Heilbronn died: March 20, 1878 in Heilbronn German physician and physicist. Travelling as a ship's surgeon he noticed that the colour difference between arterial and veinous blood is smaller in tropical than in moderate climates. He concluded that at elevated temperatures the human body produces less energy by combustion, which lead him to the hypothesis of the equivalence between physical work and heat. He published his thoughts 1842: "Bemerkungen über die Kräfte der unbelebten Natur" (Liebigs "Annalen", Bd. 42, 1842). In this publication he formulates the general law of conservation of energy and calculates the mechanical equivalent of heat. (compare also: S. Carnot , J.P. Joule and H. Helmholtz) A collection of his works was compiled in 1867: "Die Mechanik der Wärme" (Stuttgart, 1867, 3rd ed. with comments by Weyrauch, 1893). Bibliographic information Dühring: "Robert Mayer, der Galilei des 19. Jahrhunderts" (Chemnitz, 1879, 2.Aufl. Leipzig, 1904, 2. Teil, Leipzig, 1895) Weyrauch: "Robert Mayer" (Stuttgart, 1890) Gross: Robert Mayer und Hermann v. Helmholtz (Berlin, 1905)