During the 1830s and 1840s, traditional caloric theory of heat began losing favour to "dynamical" alternatives, which posit that heat is a kind of motion. Brewer and amateur scientist James Prescott Joule was one of the proponents of the latter. Joule's intricate experiments—the most successful of which involved heating water with paddle wheels—making full use of his skill in temperature control as a brewer, demonstrated decisively the reality of the "mechanical equivalent of heat." What would later become known as the "conservation of energy" was pursued by many other workers approaching the subject from a variety of backgrounds, from medicine and physiology to physics and engineering. Another notable contributor to this development was the German researcher Hermann von Helmholtz, who gave an essentially Newtonian, that is, mechanical, account. William Thomson (later Lord Kelvin) received the works of Joule and Helmholtz positively, embracing them as providing support for the emerging "science of energy." In the late 1840s to the 1850s, Kelvin, his friend William John Macquorn Rankine, and the German Rudolf Clausius published a steady stream of papers concerning heat engines and an absolute temperature scale. Indeed, the commercial value of new science had already become apparent by this time; some businessmen were quite willing to offer generous financial support for researchers. Rankine spoke confidently of the new science of "thermodynamics", a term Kelvin coined in 1854, whose fundamental principles came to be known as the First and Second Laws and whose core concepts were "energy" and "entropy." Kelvin and Peter Guthrie Tait's "Treatise on Natural Philosophy" (1867) was an attempt to reformulate physics in terms of energy. Here, Kelvin and Tait introduced the phrase "kinetic energy" (instead of 'actual'), now in standard usage. The phrase "potential energy" was promoted by Rankine.