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,
Diseases and epidemics of the 19th century 19th century. It is most prevalent in tropical-like climates, but the United States was not exempted from the fever. New Orleans was plagued with major epidemics during the 19th century, most notably in 1833 and 1853. At least 25 major outbreaks took place in the Americas during the 18th and 19th centuries, including particularly serious ones in Santo Domingo in 1803 and Memphis in 1878. Major outbreaks occurred repeatedly in Gibraltar; outbreaks in 1804, 1814, and again in 1828. Barcelona suffered the loss of several thousand citizens during an outbreak in 1821. Urban epidemics continued in the United States until