Benjamin Thompson was something of a soldier-of-fortune: he was a spy for the British during the Revolutionary War; he used his position of influence in the government to take bribes; and he worked for several countries to advance the science of armamentation, through which he first earned international acclaim. However, he was also a shrewd and intuitive scientist and was almost solely responsible for the acceptance of the concept of heat as a form of motion rather than a fluid. He is better known in the annals of science as Count Rumford.

Benjamin Thompson was born in Woburn, Massachusetts, in 1753. As a teen he worked as an apprentice to a Salem storekeeper. He was apparently a very poor apprentice, viewing himself as destined for greater achievements; in fact, by the age of 17 he had taught himself French, philosophy, and the sport of fencing, all in anticipation of his...