Benjamin Rumford (Thompson) (26.03.1753—21.08.1814) was an English physicist and a Fellow of the Royal Society (1779). Born in Woburn (USA). In 1776 he moved to England and served as a military man. In 1784–98 he held various state posts in Bavaria. There he became Count Rumford for his services. In 1799 he returned to London, where he became one of the founders of the Royal Institution. From 1802 he lived in Paris.
His work concerned heat, optics and the study of thermal radiation. In 1798 he carried out a series of experiments establishing the relation between friction and the heat released in the boring of cannon barrels. From these experiments he concluded that heat is a special kind of motion — the motion of the particles of matter. This began the investigations which in the middle of the 19th century led to the replacement of the caloric theory by the kinetic theory of heat. He discovered convection in gases and liquids. He determined the emissivity of bodies. Independently of J. Leslie he found that the better a surface reflects heat rays, the less heat it emits. He studied the thermal conductivity of various bodies, in particular of liquids, which he considered to be non-conductors of heat. In 1805 he determined the maximum density of water. He improved the shadow photometer (1794) and the thermoscope, and designed a number of other instruments.
The Royal Society established the B. Rumford Medal in 1800.