FraSkidenstrædeTilHCØrstedInstitutet

magnetism, are presented in four pictures. Before the announce- ment of his discovery (July 21, 1820) Oersted had been working on and piepaiing his experiments keeping a journal o f his research work. The latter was put before the six men after having been thoroughly informed. In 1820 Oersted formulated his discovery of electromagnetism, a Nobel Prize Effect in modern terminology. A portrait o f Oer­ sted made at that time is shown in a frontispiece. The voltaic bat- tery which forms the background of the picture is made up some of the 20 exterior copper electrodes which also serve as acid recei­ ver to an interior zinc electrode in his direct current source. For his discovery Oersted also made use of a wire connected to the two terminals of the battery, and he gave an accurate description of the various effects produced when this wire was held in various ways in relation to the compass on the table in the right-hand side of the picture. Under the marking I-IV Oersted’s explanation of his discovery is commented on in connection with his frontispiece portrait. H. C. Oersted discovered piperin 1819 in Nørregade. 6 Other H. C. Oersted, publications, 1820. On the very day o f Oersted’s Latin report (on 21’ July, 1820) he issued two notices o f his discovery to the Danish press. They are shown in facsimile. It has often been said that Oersted’s discovery was made “by acci­ dent” . It would be more correct to say that the discovery was made “unexpectedly” . Oersted did not work haphazardedly. He worked extremely carefully and systematically. One has, however, to keep a watchful eye on any unexpected possibility. Professor Pasteur mentions this, and stresses the importance of being able to snatch and catch “the unexpected” , and he points to Oersted’s discovery as an example, in his inaugural leeture at “La 229 7 Pasteur’s and Håber s evaluation of Oersted’s discovery.