This volume is concerned with the geological sciences in the 18th century, with special emphasis on France and French scientists. A first focus is on the pioneering geologist Nicolas Desmarest, whose investigations in Auvergne and Italy (among other places) had important consequences in geological theory and practice. Desmarest emerges as a figure of intriguing complexity and refined methodological convictions, defying facile interpretation in terms of, for instance, a simple polarity between vulcanism and neptunism. Widening his inquiry beyond Desmarest, Professor Taylor also endeavors to recover key elements of the presuppositions and thought-patterns of Enlightenment geologists, and to discern how geological investigation worked during this formative period. In the era that modern geological science was beginning to take form, many of the participants are seen as struggling to define their scientific objectives and procedures by drawing from the competing frameworks of physique or natural philosophy, descriptive natural history, and antiquarian scholarship or developmental history. One of the articles (Reflections on Natural Laws in Eighteenth-Century Geology) appears here for the first time in English.