The cannon boring experiment of Count Rumford, where eight kilograms of water were boiled by metal on metal friction, is investigated. Consideration of this dramatic demonstration can enrich classroom discussions of calorimetry, units of measure, elements, and thermodynamics. A section pertaining to use of the article in the classroom appears after the experiment is discussed. The cannon work was one of the Count's many efforts to understand heat and discredit the then solidly entrenched belief that heat was an element, caloric. Joule lauded Rumford's work and mined his data decades later for comparison with his own on the mechanical equivalent of heat. The discussion is laid out in the pattern familiar to students of a laboratory experiment and adds in commentary and context when pertinent. Further support for Joule's work is found in the Count's data. Also mentioned are a number of other discoveries by the Count attacking the caloric theory and thereby supporting Joule in his efforts to establish that a mechanical equivalent of heat even existed. The development of the kinetic theory of gases in the mid-19th century gave a firm grounding to the early controversial idea of the Count that heat is particle motion. Further, it allowed a formal derivation of another early idea, Avogadro's hypothesis. The Count's earnest question "What is heat?" echoes across the centuries and still gives rise to interesting and worthwhile classroom discussions.