Editing Benjamin Thompson (section)

===Mechanical equivalent of heat===
{{Main|An Inquiry Concerning the Source of the Heat Which Is Excited by Friction}}
{{see also |Mechanical equivalent of heat}}
Rumford's most important scientific work took place in Munich, and centred on the nature of heat, which he contended in "[[An Inquiry Concerning the Source of the Heat Which Is Excited by Friction]]" (1798) was not the [[Caloric theory|caloric]] of then-current scientific thinking but a form of ''[[motion (physics)|motion]]''. Rumford had observed the frictional heat generated by boring cannon at the arsenal in Munich. Rumford immersed a cannon barrel in water and arranged for a specially blunted boring tool.<ref>{{cite book | last = Rosen | first = William | title = The most powerful idea in the world : a story of steam, industry, and invention | publisher = Random House | location = New York | year = 2010 | isbn = 978-1400067053 |page=274}}</ref> He showed that the water could be boiled within roughly two and a half hours and that the supply of frictional heat was seemingly inexhaustible. Rumford confirmed that no physical change had taken place in the material of the cannon by comparing the specific heats of the material machined away and that remaining.

Rumford 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. Though this work met with a hostile reception, it was subsequently important in establishing the laws of [[conservation of energy]] later in the 19th century.