Scientific papers and reports in various drafts. Also memoranda, correspondence, bibliographies, biographical references on people in geomagnetism, photographs, illustrations, calculations, reprints, and clippings. The focus of the collection is on terrestrial magnetism. Topics include atmospheric electricity, aurora borealis, cosmic rays, sunspots, storms, the ionosphere, compasses, and geomagnetic cartography. The photographs and drawings depict Jean Baptiste Biot, Hermann Ludwig Ferdinand von Helmholtz, Michael Faraday, Alexander von Humboldt, and Thomas Young.