Celebrated Scottish chemist, born in Glasgow, where in 1830 he became professor of Chemistry in the Andersonian University; seven years later he was appointed to a similar chair in University College, London; in 1855 he resigned his professorship on succeeding Herschel as Master of the Mint; his name is honorably associated with important researches relating to the diffusion of gases and liquids, and with contributions to the atomic theory of matter (1805-1869).