TODAY'S TEACHERS of the history of science are beneficiaries of an explosive growth in the profession over the past two decades. Even a cursory comparison of annual critical bibliographies of Isis-the quarterly journal of the American History of Science Society-reveals starkly that the breadth and depth of our understanding of the history of science have increased enormously over the past 25 years. Moreover, the Isis critical bibliographies show clearly that a much lower percentage of publications in our field now derive from scientists and a much higher percentage from scholars trained as historians of science than was the case 20 to 25 years ago. The profession itself evolved in the early years of this century. Indeed, important studies in the histories of specific sciences occurred in the nineteenth century: even today historians of chemistry ignore at their own peril the scholarship of Kopp and Berthelot on alchemy and early chemistry;1 Mach's work in the history of physics2 still mer-