Copenhagen, Denmark/450

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The inscription: "H. C. ØRSTED HAVDE SIT AUDITORIUM OG SIN BOLIG HER FRA 1819 TIL 1824.
DEN 21 JULI 1820 PAAVISTE HANS CHRISTIAN ØRSTED PROFESSOR VED KJØBENHAVNS UNIVERSITET AT DEN ELEKTRISCHE STRØM VIRKER TIL AT DREJE EN MAGNETNAAL PAA TÆRS AF STRØMMENS RETNING. HAN OPDAGEDE DERMED ELEKTROMAGNETISMEN. GRUNDLAGET FOR TELEFONEN.
Translation: "H.C. Oersted had his lecture room and his residence here from 1819 until 1824. On 21 July 1820 Hans Christian Oersted, professor at the University of Copenhagen, demonstrated that the electric current causes a magnetic (or compass) needle to turn crosswise (perpendicularly) to the direction of the current. He thus discovered electromagnetism. The basis for the telephone."
The date 21 July 1820 was the date of Ørsted's paper; the discovery was made in April 1820, so the information on the inscription is not quite correct. Photograph, courtesy TDC.