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 armaments, 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...