born in Belfast, who became professor of natural philosophy at Glasgow University in 1846. He carried out important experimental and theoretical work on electromagnetism, inventing the mirror galvanometer, contributing to the development of telegraphy, and pioneering theoretical work by expressing electricity and magnetism in terms of fields. He also worked with James Joule on the Joule–Thomson effect. His main theoretical work was in thermodynamics, in which he stressed the importance of the conservation of energy (see conservation law). He also introduced the concept of absolute zero and the Kelvin temperature scale based on it. In 1896 he was created Baron Kelvin of Largs.