SMITHSONIAN PRESS MUSEUM OF HISTORY AND TECHNOLOGY Contributions From the Museum of History and Technology Papers 34-44 On Science and Technology SMITHSONIAN INSTITUTION · WASHINGTON, D.C. 1966 Publications of the United States National Museum The scholarly and scientific publications of the United States National Museum include two series, Proceedings of the United States National Museum and United States National Museum Bulletin . In these series, the Museum publishes original articles and mon

The history of the early stages of electromagnetic instrumentation is traced here through the men who devised the theories and constructed the instruments. Despite the many uses made of voltaic cells after Volta’s announcement of his “pile” invention in 1800, two decades passed before Oersted discovered the magnetic effects of a voltaic circuit. As a result of this and within a five-month period, three men, apparently independently, announced the invention of the “first” electromagnetic instrume