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,
Italian Neoclassical and 19th-century art much of their work in these wild areas. This sense of the name also identified the artists with outlaws, reflecting the traditionalists' view that new school of artists was working outside the rules of art, according to the strict laws defining artistic expression at the time. In its early years the new movement was ridiculed. Many of its artists died in penury, only achieving fame towards the end of the 19th century. Today the work of the Macchiaioli is much better known in Italy than elsewhere; much of the work is held, outside the public record, in private collections there.