BEN MARSDEN is currently Lecturer in Cultural History in the Department of History at the University of Aberdeen, UK. He read mathematics at Cambridge, took his PhD in History of Science at the University of Kent, and held a British Academy Fellowship at the University of Leeds. He subsequently held the British Academy/Royal Society Research fellowship in the History of Science before taking up his present post. He has written extensively for learned journals and published Watt's Perfect Engine: Steam and the Age of Invention (Icon Books, 2002). He is now writing a contextual biography of the Scottish academic engineer W.J.M. Rankine.CROSBIE SMITH is Director of the Centre for History and Cultural Studies of Science at the University of Kent, UK. He is the co-author (with Norton Wise) of Energy and Empire: A Biographical Study of Lord Kelvin (Cambridge University Press, 1989) and author of The Science of Energy (Athlone press and University of Chicago Press, 1998). These books won the History of Science Society's prestigious Pfizer Award in 1990 and 2000 respectively. He edited the British Journal for the History of Science from 1999 until 2004. He is currently Director of 'The Ocean Steamship Project' funded by a 5-year research grant from the Arts and Humanities Research Board.