19th century in science Carnot captured some of the ideas of thermodynamics in his discussion of the efficiency of an idealized engine. Sadi Carnot's work provided a basis for the formulation of the first law of thermodynamics—a restatement of the law of conservation of energy—which was stated around 1850 by William Thomson, later known as Lord Kelvin, and Rudolf Clausius. Lord Kelvin, who had extended the concept of absolute zero from gases to all substances in 1848, drew upon the engineering theory of Lazare Carnot, Sadi Carnot, and Émile Clapeyron–as well as the experimentation of James Prescott Joule on the interchangeability of mechanical, chemical,
19th century in ichnology "giant" trackmaker was recognized by paleontologists Joseph Le Conte and Othniel Charles Marsh as a giant ground sloth, possibly of the genus "Mylodon". 1802 1820s Late 1820s 1828 1831 1834 1835 1836 1842 1843 1845 1846 1847 1848 1850 1851 1852 1854 1858 1860 1862 1864 1865 1877 1879 1880 1884 1886 1889 [[:Category:1890s in paleontology|1890s]] [[1894 in paleontology|1894]] [[1895 in paleontology|1895]] [[Category:19th century in paleontology]] [[Category:Ichnology]] [[Category:Paleontology timelines|Ichnology]] 19th century in ichnology The 19th century in ichnology refers to advances made between the years 1800 and 1899 in the scientific study of trace fossils, the preserved record of the