[3] Joule was tutored as a young man by the famous scientist John Dalton and was strongly influenced by chemist William Henry and Manchester engineers Peter Ewart and Eaton Hodgkinson.

Joule captured the output of the alternative methods in terms of a common standard, the ability to raise a mass weighing one pound to a height of one foot, the foot-pound.

[citation needed] However, Joule's interest diverted from the narrow financial question to that of how much work could be extracted from a given source, leading him to speculate about the convertibility of energy.

Supporters of the caloric theory readily pointed to the symmetry of the Peltier–Seebeck effect to claim that heat and current were convertible in an, at least approximately, reversible process.

[b] He announced his results at a meeting of the chemical section of the British Association for the Advancement of Science in Cork in August 1843 and was met by silence.

The fact that the values obtained both by electrical and purely mechanical means were in agreement to at least two significant digits was, to Joule, compelling evidence of the reality of the convertibility of work into heat.

[10] In the paper he was forthright in his rejection of the caloric reasoning of Carnot and Émile Clapeyron, a rejection partly theologically driven:[citation needed] I conceive that this theory ... is opposed to the recognised principles of philosophy because it leads to the conclusion that vis viva may be destroyed by an improper disposition of the apparatus: Thus Mr Clapeyron draws the inference that 'the temperature of the fire being 1000 °C to 2000 °C higher than that of the boiler there is an enormous loss of vis viva in the passage of the heat from the furnace to the boiler.'

[citation needed] In June 1845, Joule read his paper On the Mechanical Equivalent of Heat to the British Association meeting in Cambridge.

[12] In 1850, Joule published a refined measurement of 772.692 foot-pounds force per British thermal unit (4,150 J/Cal), closer to twentieth century estimates.

Such precision was certainly uncommon in contemporary experimental physics but his doubters may have neglected his experience in the art of brewing and his access to its practical technologies.

[16][17] Also in 1847, another of Joule's presentations at the British Association in Oxford was attended by George Gabriel Stokes, Michael Faraday, and the precocious and maverick William Thomson, later to become Lord Kelvin, who had just been appointed professor of natural philosophy at the University of Glasgow.

Marital enthusiasm notwithstanding, Joule and Thomson arranged to attempt an experiment a few days later to measure the temperature difference between the top and bottom of the Cascade de Sallanches waterfall, though this subsequently proved impractical.

[citation needed] Though Thomson felt that Joule's results demanded theoretical explanation, he retreated into a spirited defence of the Carnot–Clapeyron school.

In his 1851 paper, Thomson was willing to go no further than a compromise and declared "the whole theory of the motive power of heat is founded on two propositions, due respectively to Joule, and to Carnot and Clausius".

The collaboration lasted from 1852 to 1856, its discoveries including the Joule–Thomson effect, and the published results did much to bring about general acceptance of Joule's work and the kinetic theory.

Joule was a pupil of Dalton and it is no surprise that he had learned a firm belief in the atomic theory, even though there were many scientists of his time who were still skeptical.

Some modern writers have criticised this approach on the grounds that Rumford's experiments in no way represented systematic quantitative measurements.

His gravestone is inscribed with the number "772.55", his climacteric 1878 measurement of the mechanical equivalent of heat, in which he found that this amount of foot-pounds of work must be expended at sea level to raise the temperature of one pound of water from 60 °F to 61 °F.