"No one interested in the history of optics, the history of eighteenth- and nineteenth-century physics, or the general phenomenon of theory change in science can afford to ignore Jed Buchwald's well-structured, highly detailed, and scrupulously researched book. . . . Buchwald's analysis will surely constitute the essential starting point for further work on this important and hitherto relatively neglected episode of theory change."—John Worrall, Isis