Manuscripts on permanent magnets and harmonic analysis, miscellaneous correspondence, papers, sketches and photographs, together with his own books, pamphlets and collected manuscripts. Included among the manuscripts are two fourteenth century manuscripts of Petrus Peregrinus, Epistola De Magnete, and Sacrobosco, De Spera. Thompson also collected letters and autographs of scientists ranging from von Guericke and Ampr̈e to the electrical inventors such as Swan and Siemens who wrote to Thompson himself. These are bound in two albums with each letter mounted on a page faced by an engraving, photograph or cartoon of the writer.