From 1821 to 1847, Danish physicist and chemist Hans Christian Ørsted (1777–1851) corresponded with Carl Friedrich Gauss and physicist Wilhelm Weber on topics such as meteorological observations and the compressibility of liquids, but above all on geomagnetism, the establishment of a magnetic observatory in Copenhagen (1835) and the investigations of the Göttingen Magnetic Society. The 34 letters are now available in a new edition, accompanied by an introduction to Ørsted and the scientific exchange between Göttingen and Copenhagen.