A Holy Undertaking
James Joule's story may seem a little hard to believe. He lived near Manchester, England—in the scientific hinterland during much of Joule's career—where his family operated a brewery, making ale and porter. He did some of his most important work in the early morning and evening, before and after a day at the brewery. He had no university education, and hardly any formal training at all in science. As a scientist he was, in every way, an amateur. Like Mayer, who was also an amateur as a physicist, Joule was ignored at first by the scientific establishment. Yet, despite his amateur status, isolation, and neglect, he managed to probe more deeply than anyone else at the time (the early and middle 1840s) the tantalizing mysteries of conversion processes. And (unlike Mayer) he did not suffer prolonged neglect. The story of Joule's rapid progress, from dilettante to a position of eminence in British science, can hardly be imagined in today's world of research factories and prolonged scientific apprenticeships.
The theme that dominated Joule's research from beginning to end, and served as his guiding theoretical inspiration, was the belief that quantitative equivalences could be found among thermal, chemical, electrical, and mechanical effects. He was convinced that the extent of any one of these effects could be assessed with the units of any one of the other effects. He studied such quantitative connections in no less than eight different ways: in investigations of chemical effects converted to thermal, electrical, and mechanical effects; of electrical effects converted to thermal, chemical, and mechanical effects; and of mechanical effects converted to thermal and electrical effects.
At first, Joule did not fully appreciate the importance of mechanical effects in this scheme of equivalences. His earliest work centered on chemical, electrical,