Part 3

The 20 years following the announcement of the voltaic-pile invention were years of intense experimental activity with this device. Many new chemical elements were discovered, beginnings were made on the electrochemical series of the elements, the electric arc and incandescent platinum wires suggested the possibilities of electric lighting, and various electrochemical observations gave promise of other practical applications such as metal-refining, electroplating, and quantity production of certain gases. Investigators were keenly aware that all of the available means for measuring and comparing the electrical aspects of their experiments (however vaguely these "electrical aspects" may have been conceived), were slow, awkward, imprecise, and unreliable.

The atmosphere was such that prominent scientists everywhere were ready to pounce immediately on any reported discovery of a new electrical "effect," to explore its potentialities for instrumental purposes. Into this receptive environment came H. C. Oersted's announcement of the magnetic effects of a voltaic circuit, on July 21, 1820.

Oersted's Discovery

Many writers have expressed surprise that with all the use made of voltaic cells after 1800, including the enormous cells that produced the electric arc and vaporized wires, no one for 20 years happened to see a deflection of any of the inevitable nearby compass needles, which were a basic component of the scientific apparatus kept by any experimenter at this time. Yet so it happened. The surprise is still greater when one realizes that many of the contemporary natural philosophers were firmly persuaded, even in the absence of positive evidence, that there must be a connection between electricity and magnetism. Oersted himself held this latter opinion, and had been seeking electromagnetic relationships more or less deliberately for several years before he made his decisive observations.

His familiarity with the subject was such that he fully appreciated the immense importance of his discovery. This accounts for his employing a rather uncommon method of publication. Instead of submitting a letter to a scientific society or a report to the editor of a journal, he had privately printed a four-page pamphlet describing his results. This, he forwarded simultaneously to the learned societies and outstanding scientists all over Europe. Written in Latin, the paper was published in various journals in English, French, German, Italian and Danish during the next few weeks.

In summary, he reported that a compass needle experienced deviations when placed near a wire connecting the terminals of a voltaic battery. He described fully how the direction and magnitude of the needle deflections varied with the relative position of the wire, and the polarity of the battery, and stated "From the preceding facts, we may likewise collect that this conflict performs circles...." Oersted's comment that the voltaic apparatus used should "be strong enough to heat a metallic wire red hot" does not excuse the 20-year delay of the discovery.

Beginnings of Electromagnetic Instrumentation

The mere locating of a compass needle above or below a suitably oriented portion of a voltaic circuit created an electrical instrument, the moment Oersted's "effect" became known, and it was to this basic juxtaposition that Ampere quickly gave the name of galvanometer. It cannot be said that the scientists of the day agreed that this instrument detected or measured "electric current," however. Volta himself had referred to the "current" in his original circuits, and Ampere used the word freely and confidently in his electrodynamic researches of 1820-1822, but Oersted did not use it first and many of the German physicists who followed up his work avoided it for several years. As late as 1832, Faraday could make only the rather noncommittal statement: "By current I mean anything progressive, whether it be a fluid of electricity or vibrations or generally progressive forces."

Nevertheless, whatever the words or concepts they used, experimenters agreed that Oersted's apparatus provided a method of monitoring the "strength" of a voltaic circuit and a means of comparing, for example, one voltaic battery or circuit with another.

It was perfectly clear, from Oersted's pamphlet, that if a compass needle was deflected clockwise when the wire of a particular voltaic circuit lay above it in the magnetic meridian, the same needle would also be deflected clockwise if the wire was turned end-for-end and placed below the compass needle, without changing the rest of the circuit. Anyone perceiving this fact might deduce, as a matter of logic, that if the wire of the circuit was first passed above the needle, in the magnetic meridian, then folded and returned in a parallel path below the needle, the deflecting effect on the needle would be repeated, and a more sensitive indicator would result, assuming that any additional wire introduced has not affected the "circuit" excessively.

Since 1821, historical accounts of the origins of electromagnetism seem to have limited their credit assignments for the conception and observation of this electromagnetic "doubling" effect (or "multiplying" effect, if the folding is repeated) to three persons. Almost without exception, however, these accounts have given no specific information as to precisely what each of these three accomplished, what physical form their respective creations took, what experiments they performed, and what functional understanding they apparently had of the situation. The usual statement is simply that a compass needle was placed in a coil of wire. The main purpose of the present review is to recount some of these details.

The following are the three candidates whose names are variously associated with the "invention" of the first constructed electromagnetic instrument, or "multiplier," or primitive galvanometer.

JOHANN SALOMO CHRISTOPH SCHWEIGGER (1779-1857) in 1820 had already been editor for several years of the Journal fuer Chemie und Physik, and was professor of chemistry at the University of Halle.

JOHANN CHRISTIAN POGGENDORF (1796-1877) in 1820 had only recently entered the University of Berlin as a student following several years as an apothecary's apprentice and a brief period as an apothecary. Four years later, he succeeded Gilbert as editor of the influential Annalen der Physik, a position he held for more than 50 years.

JAMES CUMMING (1771-1861) in 1820 was professor of chemistry at Cambridge University.

Chronology and Priority

The earliest established date in the "multiplier" record is September 16, 1820, when Schweigger read his first paper to the Natural Philosophy Society of Halle. There seems to be no reason to doubt that this report justifies the frequently used label "Schweigger's multiplier."

In an exuberant support of Schweigger's position, Speter with no mention of Cumming and no hint of "invention" details, shows that Poggendorf in 1821 admitted Schweigger's priority, but suffered some lapse of memory 40 years later when writing sections of his biographical dictionary, leaving a distinct suggestion that the invention was his. Further confusion for later generations resulted from some ambiguous entries in the Allgemeine Deutsche Biographie of 1888. The name "multiplier" seems not to have originated with Schweigger himself. Speter credits it to Meineke as "working" editor of Schweigger's Journal, but Seebeck seems to have used it much earlier.

Conceding priority of conception to Schweigger (Cumming has not been a real competitor on this point) does not alter the fact that all three seem to have reached their results independently of one another, that the first work of each on this subject was published within a period of five months, that there were significant differences in their conceptions of the uses and the optimum design of their devices and that between them they provided an adequate foundation for the subsequent development of the galvanometer to become the primary electrical-measuring instrument.

In the matter of publication, Schweigger, as editor of what was popularly called Schweigger's Journal, had an obvious advantage, and presented his experiments beginnings on page 1 of the first volume of his Journal for 1821, published January 1 of that year. Oersted's paper had appeared two volumes previously. He began by referring to Oersted's discovery as "the most interesting to be presented in a thousand years of the history of magnetism." He was, in fact, so impressed with the epochal nature of Oersted's achievement that he commemorated it by giving his Journal a second title so that "volume one" of the new title could begin in the year after Oersted's publication.

Poggendorf, as a relatively junior student, had no such easy access to publicity, but he had a staunch admirer in one of his professors, Paul Erman at the University of Berlin. Erman added a seven-page postscript on Poggendorf's invention to his book Outline of the Physical Aspects of the Electro-chemical Magnetism Discovered by Professor Oersted, published before April 1821, with an introductory paragraph:

Herr Poggendorf, who is one of the most excellent ornaments of the lecture room and laboratory of the University here, carried out a very coherent and well-conceived investigation of electro-chemical magnetism, leading step-by-step to a method of amplifying this activity-phenomenon by means of itself.

The postscript begins by referring to the "condenser [Kondensator] just brought to my attention by Herr Poggendorf" and explains that he cannot release his treatise "without preliminary announcement of this subject of the highest importance." (It can be inferred from the text that the name "condenser" was chosen because of the device's enhancing of magnetic measurements analogously to the enhancing of electric measurements by Volta's electrostatic "condenser.")

Immediately on reading the book, Schweigger published extracts, mainly of the postscript, with indignant comments on Erman's remissness (or worse) in having failed to mention Schweigger's prior work.

However, Erman was not alone in his unawareness, if it was that, of Schweigger's discovery.

Rival editor Gilbert of the Annalen der Physik reviewed Erman at much greater length than Schweigger, reprinting most of the postscript with evident enthusiasm, and stating in his preamble that the invention is attributed to "a young physicist studying here in Berlin, Herr Poggendorf." Only in a footnote is the reader directed to another footnote in the next article in the volume, where Gilbert finally states that he "cannot leave unmentioned the fact that this amplifying apparatus seems to be due to Herr Professor Schweigger." He then quotes rather fully from Schweigger's first two papers. Oersted in 1823 explained the situation thus: "The work of M. Poggendorf, having been mentioned in a book on electromagnetism by the celebrated M. Erman published very shortly after its discovery, became known to many scientists before that of M. Schweigger. This is the reason for the same apparatus carrying different names."

The same confusion is well illustrated by the paper to which Gilbert attached his confessional footnote mentioned above. Written by Professor Raschig of Dresden, on April 3, 1821, the paper is entitled "Experiments with the Electro-magnetic Multiplier," but the device, throughout the paper, is repeatedly referred to in the phrase "Poggendorf's condenser, or rather multiplier," an awkward combination that suggests editorial intervention.

The work of James Cumming at Cambridge is described in two papers which he read to the Cambridge Philosophical Society in 1821, which were then duly published in the Transactions of that Society. The first, "On the Connexion of Galvanism and Magnetism," was read April 2, 1821, and the second, "On the Application of Magnetism as a Measure of Electricity," was read a few weeks later on May 21st.