London: Baldwin, Cradock & Joy, 1820. 1st Edition. FIRST EDITION IN ENGLISH OF OERSTED’S 1820 DISCOVERY OF ELECTROMAGNETISM, opening “a new epoch in the history of physics” (DSB, 10, 185). “Its importance cannot be overestimated” (Norman, Part III, 1221). Hans Christian Oersted's paper, first published in 1820 as a small Latin pamphlet Experiemnta circa effectum conflictus electrici in acum magneticum, laid the foundation for the subsequent revolution in physics and the work of Ampère, Faraday, and then Maxwell's theory of electromagnetic radiation. Within a few months of publication, the paper was translated into several languages. Realizing the importance of the English translation, Oersted did the translation himself.
In 1820 and although most scientists thought electricity and magnetism were not related, there were some reasons to think there might be a connection. For instance, it had long been known that a compass, when struck by lightning, could reverse polarity. Oersted had previously noted a similarity between thermal radiation and light, though he did not determine that both are electromagnetic waves and seems to have believed that electricity and magnetism were forces radiated by all substances.
“During a lecture demonstration, on April 21, 1820, while setting up his apparatus, Oersted noticed that when he turned on an electric current by connecting the wire to both ends of the battery, a compass needle held nearby deflected away from magnetic north, where it normally pointed… The audience didn’t even notice.
But it was clear to Oersted that something significant was happening. “Some have suggested that this was a totally accidental discovery, but accounts differ on whether the demonstration was designed to look for a connection between electricity and magnetism, or something else entirely. Certainly Oersted was well-prepared to observe such an effect, with the compass needle and the battery (or “galvanic apparatus,” as he called it) on hand.
“Whether completely accidental or at least somewhat expected, Oersted was intrigued by his observation. He didn’t immediately find a mathematical explanation, but he thought it over for the next three months, and then continued to experiment, until he was quite certain that an electric current could produce a magnetic field (which he called an “electric conflict”).
“His battery, a voltaic pile using 20 copper rectangles, probably produced an emf of about 15-20 volts. He tried various types of wires, and still found the compass needle deflected. When he reversed the current, he found the needle deflected in the opposite direction. He experimented with various orientations of the needle and wire [noting] that the effect couldn’t be shielded by placing wood or glass between the compass and the electric current.
“On July 21, 1820, Oersted published his results in a pamphlet… His results were mainly qualitative, but the effect was clear–an electric current generates a magnetic force.
“The publication caused an immediate sensation… Others began investigating the newly found connection between electricity and magnetism… Ampère developed a mathematical law to describe the magnetic forces between current carrying wires… A decade after Oersted’s discovery, Faraday demonstrated essentially the opposite of what Oersted had found–that a changing magnetic field induces an electric current. Following Faraday’s work, Maxwell developed Maxwell’s equations, formally unifying electricity and magnetism” (APS Portal). Item #687
CONDITION & DETAILS: London: Baldwin, Cradock & Joy. Bears the armorial bookplate of the University Library of Edinburgh, “Presented by Professor A. Crum Brown”; no other library marks inside or out. Brown did pioneering work in the design of a system representing chemical compounds in diagrammatic form. 4to. vii, [Errata], 480 pages, . 5 plates. Solidly bound in half-calf over brown cloth boards; light rubbing and scuffing at the edges of the boards and spine. Five raised bands at the spine, blind tooled and black ruled. Red morocco, gilt-lettered label. Occasional toning and foxing; largely bright and clean throughout.