Maxwell, James Clerk (1831–1879), British physicist. Maxwell is ranked as the foremost physical scientist of the 19th century. His greatest achievement was the synthesis of the contributions of Faraday, Gauss, and Ampère into a single coherent electromagnetic theory. Of his several academic appointments the most important was the post of professor of experimental physics at Cambridge. He made contributions of fundamental importance to many branches of physics. The maxwell, a unit of magnetic flux, was named in his honor.