This is a book about some of the unexpected people and places involved in cultivating knowledge of the natural world and of scientific apparatus around 1800. It takes readers across continental Europe from the Enlightenment to the onset of academic professionalisation. The authors widen the horizon of inquiry by looking beyond the scientific elite of academies and prestigious science sponsored by princely courts, the focus of previous major studies of this time period. They consider people of diverse professions and occupations who advanced scientific knowledge through practical means by devoting their spare time and personal resources, thereby crossing geographic, linguistic, and societal barriers. The case studies together demonstrate that such individuals contributed substantially to the spread of new knowledge and found ways to promote technical innovations in society. The present volume is dedicated to these people: the devotees of science.