Hans Christian Oersted, a Danish natural philosopher, brother of the preceding, born at Rudkjoping, Aug. 14, 1777, died in Copenhagen, March 0, 1851. He was the son of a druggist. At the university of Copenhagen he look a prize for an essay on "The Limits of Poetry and Prose." He had become imbued with the modern German philosophy through the lectures of Steffens, and on taking his doctor's degree presented a dissertation on the "Architectonics of Natural Metaphysics," a study of the laws of physics and their higher relations as the products of reason. In 1800 he took charge of a pharmacy, devoted his attention to galvanism, and made important discoveries with respect to the action of acids during the production of galvanic electricity. In 1801-3 he studied and travelled in Germany, France, and the Netherlands, and on returning to Copenhagen lectured on electricity and cognate sciences. A selection from his scientific papers written about this time has been published under the title of " The Soul in Nature" (London, 1852). In 1806 he became professor of physics in the university of Copenhagen, and in 1809 published the first edition of his " Manual of Mechanical Physics." In 1812 he revisited Germany, and published at Berlin a work tending to show the identity of magnetism and electricity.

His discovery of this identity was made in the winter of 1819-'20. (See Electro-Magnetism, vol. vi., p. 513.) In July, 1820, Oersted promulgated his discovery in a Latin tract entitled Experi-menta circa Efficaciam Conflictm Electrici in Acum Magneticam. The French institute presented Oersted with a prize worth 3,000 francs; the royal society of London gave him the Copley medal; and by common consent he was elevated to the first rank of scientific men. He made scientific journeys at intervals to various parts of Europe, and founded the magnetic observatory of Copenhagen, and also the Danish society for the diffusion of natural science. In 1844 appeared the second edition of his " Manual of Mechanical Physics," which contained accounts of his experiments on the compressibility of water and air. He also devoted some time to politics and light literature, and published a poem entitled "The Balloon." The 50th anniversary of his connection with the university was celebrated with a national jubilee, Nov. 7, 1850. Throughout his scientific career Oersted labored to show that the laws of nature must harmonize with reason, even representing the practice of science to be a religious worship.

As a lecturer he possessed great merit, and was one of the first to give popular lectures to ladies on scientific subjects, and to urge the establishment of female colleges. A complete edition of his works was published in Copenhagen (9 vols., 1850-'51). Several of them have been translated into foreign languages.