This study is an outgrowth of our interest in the history of modern chemistry. The paucity of reliable, quantitative knowledge about past science was brought home forcibly to us when we undertook a research seminar in the comparative history of modern chemistry in Britain, Germany, and the United States. That seminar, which took place at the University of Pennsylvania in the spring of 1975, was paralleled by one devoted to the work of the "Annales School". The two seminars together catalyzed the attempt to construct historical measures of change in aspects of one science, or "chem­ ical indicators". The present volume displays our results. Perhaps our labors may be most usefully compared with the work of those students of medieval science who devote their best efforts to the establish­ ment of texts. Only when acceptable texts have been constructed from fragmentary and corrupt sources can scholars move on to the more satisfying business of making history. So too in the modern period, a necessary pre­ liminary to the full history of any scientific profession is the establishing of reliable quantitative information in the form of statistical series. This volume does not offer history. Instead it provides certain element- indicators -- that may be useful to individuals interested in the history of American chemistry and chemical industry, and suggestive for policy.