In June 1847 William Thomson, later Lord Kelvin (1824–1907), met Joule at the Oxford meeting of the British Association for the Advancement of Science, and the encounter led Thomson to study Joule's papers on the mutual convertibility of heat and mechanical work. At the Oxford meeting Joule had read a paper describing his measurement of the temperature change in a fluid agitated by a paddle wheel that was turned by a descending hanging weight; he claimed to have determined the quantitative equivalence between the heat generated by the paddle wheel and the mechanical work required to generate that heat. Thomson found Joule's conclusions astonishing; and he reported Joule's work to his brother James Thomson (1822–92), who confessed that Joule's ‘Views have a slight tendency to unsettle one's mind’. The Thomsons' sense of intellectual disorientation arose from their belief, derived from the work of Sadi Carnot (1796–1832), that heat was conserved in the generation of mechanical work by heat engines. This theory seemed to contradict Joule's claim that heat must be consumed in the generation of work. The unravelling of the apparent contradiction between the theories of Carnot and Joule was to lead to the formulation of the science that in 1854 William Thomson was to term ‘thermo-dynamics’, the theory of the mechanical action of heat.