This is a comprehensive edition of Maxwell's manuscript papers published virtually complete and largely for the first time. Maxwell's work was of central importance in establishing and developing the major themes of the physics of the nineteenth century: his theory of the electromagnetic field and the electromagnetic theory of light and his special place in the history of physics. His fecundity of imagination and the sophistication of his examination of the foundations of physics give particular interest and importance to his writings. Volume III: 1874-1879 covers the period of Maxwell's direction of the Cavendish Laboratory and documents the espousal of his theories by a wider circle of physicists. During this last period of his life his work began to achieve the pre-eminence in the classical physics of the nineteenth century, which it has retained ever since.