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Thompson, Benjamin (Count Rumford) (1753–1814)



Benjamin Thompson, born in Woburn, Massachusetts, in 1753, acquired a deep interest in books and scientific instruments as a youth, and matured into a person of great charm and intellect. In 1772 he received a position as a teacher in Concord, New Hampshire, where he soon met and rather quickly married Sarah Walker Rolfe, a wealthy widow fourteen years his senior, who had been charmed by his brilliant mind and dashing manners. Overnight his status changed to that of a country gentleman, managing his wife's estate and helping John Wentworth, the British governor of New Hampshire, with some agricultural experiments.

To reward Thompson, in 1773 Wentworth commissioned him a major in the New Hampshire militia. There Thompson acted as an informant for the British, so arousing the rancor of his fellow colonists that they planned to tar and feather him. He quietly departed for Boston, leaving his wife and baby daughter behind. He never saw his wife again, and only saw his daughter briefly many years later when he was living in France.

In Boston Thompson worked briefly for General Gage, the highest-ranking British officer in the Massachusetts Bay Colony. When the American Revolution began in 1776, his loyalty to the American cause was clearly suspect, and he left for England. Upon arriving in London his obvious talents led to rapid advancement in his career, and eventually he was appointed Undersecretary of State for the colonies. He also had a brief military career with the British Army in America, and retired in 1784 with the rank of Colonel.

In 1784 this freelance diplomat joined the court of Karl Theodor, Elector of Bavaria, and rapidly rose to become head of the ineffectual Bavarian Army. For his contributions to building up Bavaria's defensive strength, in 1793 he was made a Count of the Holy Roman Empire and took the name "Count Rumford," since that was the original name of the New Hampshire town in which he had first taught school.

After returning briefly to London in 1800, Rumford was on the move again, this time to Paris, where in 1805 he married the widow of the great French chemist, Antoine Lavoisier. Rumsford's first wife had passed away by this point. His marriage to Madame Lavoisier was, however, a very stormy affair and two years later, after having ensured a handsome lifetime annuity for himself, he and his wife separated. Rumford then retired to Auteuil, outside Paris, where for the rest of his life he worked energetically and with much success on applied physics and technology.

During his life Count Rumford did much good with the funds he obtained by marrying wealthy widows, and by dazzling the leaders of three European nations with his scientific accomplishments. He established sizable prizes for outstanding scientific research, to be awarded by the American Academy of Arts and Science in Boston, and the Royal Society of London. He designed the lovely English Gardens in Munich, and supervised their construction. Finally he provided the funds to start the Royal Institution in London, which later attained great scientific prestige under the direction of Humphry Davy and Michael Faraday.


During the eighteenth century, the kinetic theory of heat had gradually lost favor and been replaced by the conception of heat as an indestructible fluid, to which Lavoisier had given the name "caloric." In 1798 Rumford, as Minister of War for the Elector of Bavaria, performed pivotal experiments in negating the existence of caloric. While watching the boring of a cannon barrel at the Munich military arsenal, Rumford was struck by the large amount of heat produced in the process. As long as the mechanical boring continued, heat continued to appear. This was hard to explain on the basis of the prevalent caloric theory. It appeared that continued boring was able to produce an inexaustible amount of caloric, which the limited amount of metal in the cannon barrel could not possibly contain.

Rumford decided to try a more controlled experiment. He placed a brass gun barrel in a wooden box containing about nineteen pounds of cold water, and used a team of horses to rotate a blunt steel borer inside the barrel. After 2.5 hours, the water boiled! As Rumford described it, "It would be difficult to describe the surprise and astonishment expressed on the countenances of the bystanders on seeing so large a quantity of cold water heated, and actually made to boil, without any fire."

Rumford suggested that anything that an isolated body can supply without limitationcould not possibly be a material fluid. The only thing that could be communicated in this fashion was motion, in this case the motion of the steel borer that first produced heatin the form of molecular motion of the cannon molecules, which was then passed on to the water as random motion of its molecules. Therefore, according to Rumford heat was a form of random molecular motion. By this and other experiments Rumford had indeed demonstrated that a caloric fluid did not exist, but he had not yet seen the intimate connection that exists between heat, work and energy. That connection was to come later with the research of Sadi Carnot, Julius Robert Mayer, James Joule, and Hermann von Helmholtz.

In addition to this groundbreaking research on work and heat, Rumford made an extraordinary number of important contributions to applied science. He studied the insulating properties of the cloth and fur used in army uniforms, and the nutritive value of various foods and liquids. He decided that thick soup and coffee were the best sources of strength for any army in battle; and introduced the potato as a food into central Europe. He designed a large number of drip-type coffee makers and introduced the first kitchen range, the double boiler, and the pressure boiler found in modern kitchens. Rumford also designed better chimneys and steam-heating systems for houses. His continued interest in the scientific principles behind such devices made Rumford one of the world's first great applied physicists.

Rumford died suddenly at Auteuil in August 1814, leaving his entire estate to Harvard College to endow a professorship in his name. While considered a great scientist and a charming man by the best and brightest of his contemporaries, Rumford was at heart a soldier-of-fortune, and could be arrogant, obnoxious, and cruel to those he considered beneath him. For these reasons, he is less highly respected today as a man than he is as a scientist.

Joseph F. Mulligan


Brown, S. C. (1952). "Count Rumford's Concept of Heat." American Journal of Physics 20:331–334.

Brown, S. C. (1953). "Count Rumford—Physicist and Technologist." Proceedings of the American Academy of Arts and Sciences 82:266–289.

Brown, S. C. (1962). Count Rumford, Physicist Extra-ordinary. Garden City, NY: Anchor Books.

Brown, S. C. (1976). "Thompson, Benjamin (Count Rumford)." In Dictionary of Scientific Biography, ed. C. C. Gillispie, Vol. 13, pp. 350–352. New York: Scribner.

Brown, S. C. (1979). Benjamin Thompson, Count Rumford. Cambridge, MA: MIT Press.

Ellis, G. E. (1871). Memoir of Sir Benjamin Thompson, Count Rumford. Boston: American Academy of Arts and Sciences.

Wilson, M. (1960). "Count Rumford," Scientific American 203 (October): 158–168.

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