 Helmholtz acknowledged in his essay that earlier scientists, including Joule, Newton, Bernoulli, and Rumford, had arrived at various forms of the principle of energy conservation. In his history of mechanics, Ernst Mach argues that some form of Helmholtz’s principle was known to “almost all eminent investigators” in history (Mach 1911, 20). In his landmark study of energy conservation, Thomas Kuhn presents the work of Joule, Mayer, and others from the 1830’s, which argues that heat and work can be substituted for each other quantitatively, which is a significant component of Helmholtz’s principle (Kuhn 1969, 321). Kuhn argues that the discovery of the principle of energy conservation is a case in which several scientists lay the experimental and conceptual framework for a principle together. 