James Clerk Maxwell (13.07.1831 — 5.02.1879) was an English physicist and a Fellow of the Royal Society of Edinburgh (1855) and of the Royal Society of London (1861). He was born in Edinburgh. He studied at the Universities of Edinburgh (1847 — 50) and Cambridge (1850 — 54). On finishing the latter he taught for a short time at Trinity College; in 1856—60 he was professor at the University of Aberdeen, in 1860 —65 at King's College London, and from 1871 the first professor of experimental physics at Cambridge. Under his direction the well-known Cavendish Laboratory in Cambridge was built, and he headed it to the end of his life. His work concerned electrodynamics, molecular physics, general statistics, optics, mechanics and the theory of elasticity. Maxwell's most substantial contribution was to molecular physics and electrodynamics. In the kinetic theory of gases, of which he is one of the founders, he established in 1859 the statistical law describing the distribution of the molecules of a gas over velocities (the Maxwell distribution). In 1866 he gave a new derivation of the distribution function of molecules over velocities, based on the consideration of direct and inverse collisions, developed the theory of transport in a general form, applying it to the processes of diffusion, thermal conduction and internal friction, and introduced the concept of relaxation time. In 1867 he was the first to show the statistical nature of the second law of thermodynamics (“Maxwell's demon”), and in 1878 he introduced the term “statistical mechanics”. Maxwell's greatest scientific achievement is the theory of the electromagnetic field, which he created in 1860 — 65 and formulated as a system of several equations (Maxwell's equations) expressing all the basic regularities of electromagnetic phenomena (the first differential equations of the field were written down by Maxwell in 1855—56). In his theory of the electromagnetic field Maxwell used (1861) a new concept, the displacement current, gave (1864) a definition of the electromagnetic field and predicted (1865) an important new effect: the existence in free space of electromagnetic radiation (electromagnetic waves) and its propagation in space with the speed of light. The latter gave him grounds for holding (1865) that light is one of the kinds of electromagnetic radiation (the idea of the electromagnetic nature of light) and for revealing the connection between optical and electromagnetic phenomena. He calculated the pressure of light theoretically (1873). He established the relation ε = n2 (1860). He predicted the Stewart — Tolman and Einstein — de Haas effects (1878) and the skin effect. He also formulated a theorem in the theory of elasticity (Maxwell's theorem), established relations between the basic thermophysical parameters (Maxwell's thermodynamic relations), developed the theory of colour vision and studied the stability of Saturn's rings, showing that the rings are neither solid nor liquid but are a swarm of meteorites. He designed a number of instruments. He was a well-known populariser of physics. He was the first to publish (1879) the manuscripts of H. Cavendish's works.