What is heat? The question today is a relatively simple one. The answer would be that heat is a form of energy, not a chemical substance. For centuries however, scientists were puzzled as to the nature of heat, and it was only through the work of such men as Count Rumford that the real answers came to be known.
Benjamin Thompson, who later became Count Rumford, had an interesting life. Born in 1753 in Massachusetts in what is now the U.S.A., Benjamin Thompson had little in the way of formal education. In the American War of Independence he came to Britain, and eventually became Under-Secretary of State in the Ministry for the Colonies. It was about this time that he began his experiments concerning heat. In 1779 he was elected to a fellowship of the Royal Society. Three years later ha was knighted by King George III.
After the end of the war Benjamin Thompson went to Bavaria, Germany, and became Minister of War, helping to reorganize the army there. He made such an impression on the Bavarian authorities that he was given the title of Cunt Rumford.
Later he returned to England, where he helped to found the Royal Institution (1799). After this he went to live in France, and married the widow of the famous chemist Antoine Lavoisier. In 1814 Rumford died at Auteuil, at the age of sixty-one.
The scientist published his investigations into heat in 1798, in a paper read to the Royal Society. He had been astonished at the amount of heat generated when army cannon were bored, and submitted the process to experiment. If heat were actually a substance, as many scientists of that time believed, it was difficult to see how so much of it could be produced during the boring of a metal cannon. It might be argued that the heat had been stored in the solid block of metal all the time, and was released when the block was broken down into filings. But Rumford showed that the amount of heat was not related to the quantity of filings produced. The amount of heat – but not the quantity of filings – was greater when a blunt borer was used. In one spectacular experiment Rumford had the barrel of the cannon bored under water, using horses to move the cannon round. To the amazement of the spectators, the water was made to boil, and continued to do so as long as the machining of the metal carried on. The main conclusion reached by Rumford was that heat could not in fact be a material substance, but was the result of the mechanical energy consumed during the boring operation. The idea, held even by such eminent men as Lavoisier, that heat might be chemical element could no longer be accepted.