After his revolutionary discovery of electromagnetism in 1820 H.C. Oersted quickly published his findings in a small treatise in Latin for the scholars of Europe. Soon after the treatise was translated into French, Italian, German, English and Danish, and reprinted in a number of scientific journals. This new publication contains photographic reproductions of all these texts. Søren Absalon Larsen, professor at the College of Advanced Technology – founded by Oersted in 1829, currently DTU (Technical University of Denmark) – published the texts in facsimile in 1920, the hundred-year anniversary for Oersted’s discovery. It is this 1920 edition which is now reprinted, supplemented by a new postscript by Carl Henrik Koch.