The final volume of James Clerk Maxwell’s correspondence and manuscript papers begins in 1874, with the formal inauguration of the Cavendish Laboratory at Cambridge, and concludes with his death at the age of 48. As well as his Cambridge Professorship, Maxwell was concerned with directing the Cavendish Laboratory; acting as author and reviewer for the ninth edition of the Encyclopaedia Britannica and editing The Electrical Researches of Cavendish. In this period his letters also show his continuing commitment as a natural philosopher, apparent in his response to innovations in physical theory (by Boltzmann, Gibbs, Lorentz, and van der Waals), and in expanding his work on statistical physics and the kinetic theory of gases. His correspondence shows his influence on the younger generation of physicists whose outlook was shaped by his own style of physical theorising: the emergent Maxwellian physics. This edition is annotated with a full historical commentary.