William Thomson, Lord Kelvin
British physicist contributed to many fields of physics; he taught at Glasgow for a long time. He is one of the founders of thermodynamics, as is commemorated in the name of the unit of absolute temperature.
However, he did not accept Clausius's notion of entropy which may extend to the case of diffusion of matter; Kelvin tried to substitute the notion of "dissipation of energy" in its stead, but this does not cover all of irreversible procecces. This produced some grave misundertandings among British physicists, including even Maxwell; but Maxwell corrected his misunderstanding by virtue of Gibbs's apt comment.
Kelvin's contribution in the theory of electricity and magnetism is also important.