James Prescott Joule

English physicist and brewer (1818-1889)

James Prescott Joule (24 December 181811 October 1889) was an English physicist and brewer. Joule studied the nature of heat, and discovered its relationship to mechanical work.


  • My object has been, first to discover correct principles and then to suggest their practical development.
    • On Electro-magnetic forces (March 10, 1840), in Annals of Electricity, Vol. 4, p. 484.
  • It was in the year 1843 that I read a paper "On the Calorific Effects of Magneto-Electricity and the Mechanical Value of Heat" to the Chemical Section of the British Association assembled at Cork. With the exception of some eminent men, among whom I recollect with pride Dr. Apjohn, the president of the Section, the Earl of Rosse, Mr. Eaton Hodgkinson, and others, the subject did not excite much general attention; so that when I brought it forward again at the meeting in 1847, the chairman suggested that, as the business of the section pressed, I should not read my paper, but confine myself to a short verbal description of my experiments. This I endeavoured to do, and discussion not being invited, the communication would have passed without comment if a young man had not risen in the section, and by his intelligent observations created a lively interest in the new theory. The young man was William Thomson, who had two years previously passed the University of Cambridge with the highest honour, and is now probably the foremost scientific authority of the age.
    • James Prescott Joule (1887). Joint Scientific Papers. The Physical Society of London. p. 215. 

Quotes about Joule

  • If the water flow down by a gradual natural channel, its potential energy is gradually converted into heat by fluid friction, according to an admirable discovery made by Mr Joule of Manchester above twelve years ago, which has led to the greatest reform that physical science has experienced since the days of Newton. From that discovery, it may be concluded with certainty that heat is not matter, but some kind of motion among the particles of matter; a conclusion established, it is true, by Sir Humphrey Davy and Count Rumford at the end of last century, but ignored by even the highest scientific men during a period of more than forty years.
    • William Thomson, Mathematical and Physical Papers, Vol.2 (1884) "On Mechanical Antecedents of Motion, Heat and Light" (original publications 1854, 1855)
  • Mr Joule... fully established the relations of equivalence among the energies of chemical affinity, of heat, of combination or combustion, of electrical currents in the galvanic battery, of electrical currents in magnetoelectric machines, of engines worked by galvanism, and of all the varied and interchangeable manifestations of calorific action and mechanical force which accompany them. These researches, with the theory of animal heat and motion in relation to the heat of combustion of the food, and the theory of the phenomena presented by shooting stars, due to the same penetrating investigator, have afforded to the author of the present communication the chief groundwork for his speculations.
    • William Thomson, Mathematical and Physical Papers, Vol.2 (1884) "On Mechanical Antecedents of Motion, Heat and Light" (original publications 1854, 1855)
Wikipedia has an article about:
Wikisource has original works by or about: