On the Mechanical Equivalent of Heat

Cover page of the 1845 article "On the Mechanical Equivalent of Heat" by English physicist James Joule.

In famous publications, “On the Mechanical Equivalent of Heat” was an 1845 paper by English physicist James Joule in which he presented the results that when the temperature of a pound of water is increased by one degree Fahrenheit that an amount of vis viva (kinetic energy) is communicated to the water equal to mechanical work expended by a weight of 890 pounds falling one foot, a value now known as the mechanical equivalent of heat. [1]

In the following years, Joule expanded on his work, via more precise experiments, and published the definitive form of his "On the Mechanical Equivalent of Heat", in nineteen pages, in the transactions of the Philosophical Society of London. [2]

References
1. Joule, James P. (1845). "On the Mechanical Equivalent of Heat", Brit. Assoc. Rep., trans. Chemical Sect, p.31, read before the British Association at Cambridge, June.
2. (a) Joule, James P. (1847). “On the Mechanical Equivalent of Heat: as Determined by the Heat evolved by the Friction of Fluids.” Phil. Mag. Vol. 31, pg. 173-78. Read before the Mathematical and Physical Section of the British Association at Oxford, June.
(b) Joule, James P. (1850). “On the Mechanical Equivalent of Heat.” Philosophical Transactions of the Royal Society of London, 140: 61-82.

Further reading
● Smith, Crosbie W. (1976). “Faraday as Referee of Joule’s Royal Society Paper: ‘On the Mechanical Equivalent of Heat’.” Isis, 67: 444-449.

External links
● On the Mechanical Equivalent of Heat (historical) – Encyclopedia of Earth.

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