Did industry and commerce affect the concepts, values and epistemic foundations of different sciences? If so, how and to what extent? This book suggests that the most significant influence of industry on science in the two case studies treated here had to do with the issue of realism. Using wave propagation as the common thread, this is the first book to simultaneously analyse the emergence of realist attitudes towards the entities of the ionosphere and of the earth's crust. However, what led physicists and engineers to adopt realist attitudes? This book suggests that a new kind of realism -a realism of social and cultural origins- is the answer: a preliminary, entity realism responding to specific commercial and engineering interests, and a realism that was neither strictly instrumental nor exclusively operational. The book has two parts: while Part I focuses on the study of the ionosphere and how the British radio industry affected ionospheric physics, Part II focuses on the study of the Earth's crust and how the American oil industry affected crustal seismology.