Benjamin Thompson, Count Rumford

Benjamin Thompson was born in 1753 in Woburn, Massachusetts. A Loyalist during the American Revolution, he spied for the British and fled to England when the war turned, abandoning his wife and child. There he rose rapidly, and later entered the service of the Elector of Bavaria, reforming the army, founding workhouses for the poor, and laying out Munich's English Garden. For these services he was made a Count of the Holy Roman Empire in 1791, taking the name Rumford after the New Hampshire town (now Concord) where he had married.

Rumford's most consequential scientific work came from supervising the boring of brass cannon in Munich around 1798. He was struck that the barrels grew hotter the longer the boring continued, apparently without limit. Using a deliberately blunt tool that rubbed rather than cut, and immersing the work in water, he showed that the friction could bring the water to a boil with no fire — and that the heat produced was, as far as he could tell, inexhaustible.

He argued that anything an isolated body can supply without limit cannot be a material substance, directly contradicting the caloric theory's assumption that heat is a conserved fluid. Though the old guard resisted, his experiment, together with Davy's, set the stage for the recognition that heat is a form of motion or energy, confirmed quantitatively by Joule a generation later.

Rumford was also a gifted practical inventor, devising improved fireplaces and chimneys, the double boiler, a drip coffee percolator, and thermal underwear, and he studied the insulating properties of clothing and the convection of heat in fluids. He helped found the Royal Institution in London, settled in France, and married Lavoisier's widow before they separated; he died near Paris in 1814.