Painting by John Collier. James Joule (1818-1889) is best known for his experimental establishment of the mechanical theory of heat. In 1847 Joule met the Scottish physicist William Thomson, Baron Kelvin of Largs (1824-1907), who recognised the importance of Joule's work and went on to collaborate with him on a series of papers. In 1848 Joule became a fellow of the Royal Society. From 1852 Joule and Thomson worked together to try and verify predications made previously by Thomson in relation to thermodynamics. This led to the so-called Joule-Thomson effect, based on a slight deviation from the work on gases by H V Regnault. Following his wife's death in 1854, and then his own declining health from 1872, Joule undertook little work at the end of his life.
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