William Thomson and the heritage of caloric

Summary

William Thomson published between 1849 and 1852 three influential papers on the theory of heat. However, historians of science have already called attention to Thomson's difficulties in reconciling a principle formulated by James Prescott Joule with another principle formulated by Nicolas Leonard Sadi Carnot, and to errors Thomson made in his calculations. In the meantime, Rudolf Julius Emmanuel Clausius reconciled the two principles, and in 1854 he derived an expression for Carnot's principle. The author and collaborators have shown elsewhere that it was fundamental to Clausius' reasoning that he took to its ultimate consequence the meaning of Carnot's principle as a ‘recovery’ condition. Thomson somehow let the meaning of ‘recovery’ escape him. Therefrom came his troubles. He seems to have been so obsessed by his initial difficulties that he put the emphasis on irreversibility and on conservation of energy, missing ‘all the rest’.