Rumford: heat from friction in cannon boring

1798 Energy and motion observation

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An observation that mechanical motion produces heat without any store of caloric: heat is not a material substance.

Boring cannon barrels in the Munich arsenal, the Anglo-Bavarian physicist Benjamin Thompson (Count Rumford) in 1798 noted that heat could be drawn out for as long as the borer turned, and concluded that all that was transmitted to the barrel was motion.

Contemporaries (W. Henry, T. Thomson) found the caloric theory flexible enough to accommodate the result, and the experiment was not decisive.

Why this date

exact (Phil. Trans. 88, 80-102)

Links under review

• Caloric (calorique) as a weightless conserved fluid

  refuted by · Confidence: medium

  The only sources are Wikipedia articles (citing Fox 1971 and Henry 1802); a verbatim quotation from Fox 1971 or Henry 1802 is needed.

  Rumford's experiment showed unlimited generation of heat by friction, which is incompatible with a conserved fluid; but in Rumford's lifetime this was not taken as a refutation.

  Dispute: Textbooks call Rumford's experiment a "refutation" of caloric; historians (Fox 1971, Cardwell 1971) show that the caloric theory survived comfortably for another half century and that Rumford himself made a "reckless extrapolation" about the inexhaustibility of heat.

  Link sources

  • Wikipedia «An Inquiry Concerning the Source of the Heat...» (2024) Verified 20 Sep 2026

    there was enough uncertainty in the caloric theory to allow its adaptation to account for the new results

  • Wikipedia «Caloric theory» (2024) Verified 20 Sep 2026

    His results were not seen as a 'threat' to caloric theory at the time, as this theory was considered to be equivalent to the alternative kinetic theory.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

• Mechanical equivalent of heat (Joule)

  influenced · Confidence: medium

  The only source is the Wikipedia article 'Caloric theory' (citing Fox 1971); a verbatim quotation from Fox 1971 is needed.

  Rumford's experiment served as a model and motive for Joule's measurements.

  Dispute: No direct quotation from Joule about Rumford has been extracted from the primary source (Phil. Trans. 1850); the claim rests on a secondary source.

  Link sources

  • Wikipedia «Caloric theory» (2024) Verified 20 Sep 2026

    Rumford's experiment inspired the work of James Prescott Joule and others towards the middle of the 19th century.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Four statements on this card (the observation while boring cannon barrels, the argument from apparently inexhaustible heat against caloric, the reaction of contemporaries, and the experiment's influence on Joule) rest on a summary in the Wikipedia article. Verbatim quotations are needed from the works it cites: Cardwell D. S. L., «From Watt to Clausius», 1971, and Henry W., 1802.

Node sources

• Thompson B. (Count Rumford) «An Experimental Enquiry Concerning the Source of the Heat which is Excited by Friction», Phil. Trans. R. Soc. 88, 80-102 (1798)

  IV. An inquiry concerning the source of the heat which is excited by friction. Benjamin Thompson. Phil. Trans. R. Soc. (1798) (88): 80–102.

• Wikipedia «An Inquiry Concerning the Source of the Heat Which Is Excited by Friction» (2024) Verified 20 Sep 2026

  Rumford had observed the frictional heat generated by boring out cannon barrels at the arsenal in Munich.

• Wikipedia «An Inquiry Concerning the Source of the Heat Which Is Excited by Friction» (2024) Verified 20 Sep 2026

  Rumford also argued that the seemingly indefinite generation of heat was incompatible with the caloric theory. He contended that the only thing communicated to the barrel was motion. Rumford made no attempt to further quantify the heat generated or to measure the mechanical equivalent of heat.

• Wikipedia «An Inquiry Concerning the Source of the Heat Which Is Excited by Friction» (2024) Verified 20 Sep 2026

  Most established scientists, such as William Henry, as well as Thomas Thomson, believed that there was enough uncertainty in the caloric theory to allow its adaptation to account for the new results. It had certainly proved robust and adaptable up to that time.

• Wikipedia «An Inquiry Concerning the Source of the Heat Which Is Excited by Friction» (2024) Verified 20 Sep 2026

  However, the experiment inspired the work of James Prescott Joule in the 1840s. Joule’s more exact measurements were pivotal in establishing the kinetic theory at the expense of caloric.

"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Further reading

Not evidence: these carry no quotation and support nothing we wrote. They are books and scans to read next.

• Cardwell D. S. L. «From Watt to Clausius», Heinemann (1971)

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