Sir Benjamin Thompson, count von Rumford was an American-born British physicist and inventor who was a founder of the Royal Institution of Great Britain. One of the leading figures in the history of thermodynamics, his work rejected the popular belief that heat is a liquid form of matter and laid down the modern theory that heat is a form of motion. A prolific designer and inventor, Benjamin Thompson also improved the efficiency of fireplaces and chimneys and designed the Rumford photometer, an instrument which measures the intensity of light.
Benjamin Thompson was born in Woburn, Massachusetts on March 26 in 1753. His father, Benjamin Thompson was a farmer and his mother was Ruth Simonds. His father died when he was an infant. Benjamin received a village school education and was later educated by the family minister. He showed excellent ability algebra, geometry, astronomy and mathematics. To obtain a trade, aged fourteen, Benjamin joined a store as an apprentice and carried out engraving work. While working, he also enjoyed experiments in chemistry and mechanics. Benjamin Thompson moved to Boston to become an apprentice clerk in 1769. The following year, he attended medical and astronomy lectures to further his knowledge.
At nineteen, in 1772, Thompson married a rich widow named Sarah Walker and they lived in Rumford, New Hampshire. The marriage produced one daughter, Sarah, in 1774. The American Revolution was by now well underway. Thompson sided with the British. He received a commission as a major and later also spied for the British Army.
When the British evacuated Boston in 1776, Thompson returned to England. He then worked for the British government and also continued his scientific interests. He was made a member of the Royal Society in 1779 due to his extraordinary scientific accomplishments. He was knighted in 1784.
Thompson moved to Bavaria in 1785 as military commander for the elector of Bavaria. He spent eleven years in Bavaria reorganizing the army and making technical improvements. He also established workhouses for the poor and introduced a nutritious soup for the poor, Rumford soup. In recognition of his civilian and military services, he was given the title of Count in 1791 and chose the name Count Rumford.
Thompson returned to England in 1798 and he helped establish the Royal Institution of Great Britain in 1799.
His first wife now having died, Thompson married he second wife, Marie-Anne Lavoisier, in Paris in 1804. Thompson died near Paris in 1814. He was 61 years old. His only daughter, Sarah Thompson inherited his title.
Contributions and Achievements:
During the American Revolution, Thompson conducted experiments on the force of gunpowder and this was published in the Philosophical Transactions of the Royal Society (in 1781).
Thompson became interested in the concept of heat while serving for the military in 1798. He watched the process of boring cannons. This process used a large slow turning drill which bored out a hole from a solid piece of metal. The metal turned red hot and even boiled the water used to keep it cool. The old explanation was that, if the metal is broken to pieces, the caloric is liberated from the metal. This gives rise to heat.
Thompson rejected this because, when the metal is not filed / bored away, heat is still emitted by simple friction. Thompson’s view was that the heat was due to the mechanical motion of the borer. He showed that the quantity of heat was equal to the motional energy of the borer. He made it clear that heat is a form of energy. Thompson attempted to assess how much heat was produced by a given amount of motion. He was the first scientist to measure the “mechanical equivalent of heat (MEH)” . This would later become known as the heat capacity or thermal capacity.
Thompson also examined the insulating properties of objects such as wool, fur and feathers. He correctly deduced that insulation occurs because the convection of air is inhibited. He is credited with inventing thermal underwear as a result of his observations.
Interested in illumination, Thompson designed the Rumford photometer, an instrument which measures the intensity of light comparing different light sources.
Thompson also designed inventions of a domestic nature. He improved the efficiency of fireplaces and chimneys by introducing the smoke shelf, the throat, and the damper. He designed a tall, shallow fireplace (the Rumford fireplace) with angled sides and backs to reflect more heat into the room. He also invented a kitchen range, drip coffeepot and the double boiler.