In this first biography of the physicist Sir James Prescott Joule (1818–1889), his friend and collaborator Osborne Reynolds (1842–1912), Professor of Engineering at Owens College, Manchester, is keen to show how Joule, the son of a prosperous Salford brewer, was an 'ordinary' boy, enjoying regular walking trips to Snowdon, the Peaks and the Lakes; at the same time, he was greatly influenced by two years of tuition by John Dalton. His later experiments, observations and published papers are discussed and quoted at length. Reynolds stresses the influence Joule's work on heat and thermodynamics had on his contemporaries, but also that this 'amateur' scientist was often so far ahead of his time that his work was misunderstood or dismissed. Since publication of this book in 1892, only one other biography of Joule has appeared, and so it remains a vital source of first-hand information on his life and work.