Oersted and the Discovery of Electromagnetism
by Frederick Gregory
Department of History
University of Florida
Contemporary historians of science do not all agree that the discovery of electromagnetism by Hans Christian Oersted in 1820 was directly tied to Friedrich Schelling's system of romantic nature philosophy, nor is it clear how one could establish this assertion beyond doubt. What is clear is that Oersted was attracted to certain fundamental tenets of German idealistic thought and, as we shall see, a direct personal link between Schelling and Oersted can be demonstrated. In fact, it was reported later in the nineteenth century that a few years before his death Oersted himself credited Schelling with the stimulus necessary to the discovery of electromagnetism.(1)
One thing is sure: Oersted's approach to nature made him far more appreciative of the categories employed by the members of the Romantic School than were, say, the French scientists of the Académie des Sciences. Oersted's achievement, therefore, demonstrates that, in Robert Stauffer's words, "the intellectual environment can influence the evolution of science along with the basic influence of the internal logic of scientific ideas, and the influence of social political, technological, and economic factors."(2) The reader may not have anticipated that thoughts as abstruse and apparently "unscientific" as Schelling's could constitute an intellectual environment that might contribute to the uncovering of so fundamental a scientific discovery as electromagnetism.
Hans Christian Oersted
Hans Christian Oersted was born in the south central part of Denmark in 1777. He and his younger brother Anders entered the University of Copenhagen in 1793, Hans concentrating on medicine, physics, and astronomy while Anders took up law. The brothers did not confine their attention to these fields, for, as was common in a university education in those days, they dabbled in a wide variety of disciplinary studies. In 1797 Hans earned first prize for an essay on "Limits of Poetry and Prose." In the same year the elder Oersted brother completed a degree in pharmacy with high honors, and two years later he was awarded the degree Doctor of Philosophy with a dissertation entitled "On the Form of an Elementary Metaphysics of External Nature."(3)
Oersted's dissertation was heavily influenced by the thought of the German philosopher Immanuel Kant; in fact, in 1798 he served on an editorial staff of a journal largely given over to Kant. In particular it was Kant' a claim, as enunciated in his Metaphysical Foundations of Natural Science of 1786, that "a rational doctrine of nature deserves the name of natural science only when the natural laws at its foundation are cognized a priori, and are not mere laws of experience" that stayed with Oersted throughout his life.(4)
Indeed, it has been suggested that Oersted's bid in 1803 to acquire a university chair in physics at Copenhagen was rejected because his philosophical interests were so strong.(5)
The period just prior to 1803 was filled largely with travel. Oersted did spend the year 1800 lecturing at the university and running an apothecary shop, but in 1801 he set off on the customary Wanderjahr. He visited Germany first, meeting with the philosophers Fichte and Schlegel in Berlin, and then Schelling and the nature philosopher J.W. Rltter in Jena. While in Jena he discovered an obscure Latin work by a Hungarian named Jakob Joseph Winterl in which it was claimed that all forces of nature ultimately have the same source,(6) a message not unlike that he heard from Schelling.
From Germany it was on to Paris and then to the Netherlands. In France he missed the philosophical spirit that accompanied German science, but he delighted to meet the French scientific luminaries Cuvier ant Bertholet.
Back in Copenhagen in 1803, Oersted failed in his first bid to land the position in physics at the university. He set up private lectures for which an admission was charged. Perhaps because of the large audiences these lectures drew, the university eventually offered him the position he had sought earlier. Although he was not made a full professor until 1817, he was a member of the faculty at Copenhagen from 1806 until he died in 1851, having first lectured in the university in 1800. In November of 1850 Denmark celebrated the jubilee of Oersted's association with the University of Copenhagen by declaring a national holiday, a fitting tribute to a citizen who had by then become one of the country's most famous discoverers.
Oersted's Understanding of Science
As the nineteenth century opened Oersted, like virtually everyone connected with science, was caught up with Alessandro Volta's invention of the galvanic battery. Initial discoveries in electricity beginning in the seventeenth century were made in conjunction with static charges produced in insulated bodies. In 1800 Volta, building on a chance discovery by his countryman Luigi Galvani of "animal electricity," showed that a continuous flow of electricity could be produced. The invention of electric current opened up a new field of research, the observed phenomena of which were grouped originally under the name of galvanism.
As manager of the Lion Pharmacy in the year of Volta's discovery, Oersted managed to perform several galvanic experiments and even developed a new form of Volta's apparatus. During his trip to Germany the following year Oersted was often asked to duplicate his experiment with the new battery, thus reinforcing his already pronounced interest in electrical phenomena.
When later in the same year two Englishmen demonstrated that the passage of an electrical current through water caused water to decompose into hydrogen ant oxygen gas, a connection between electrical "force" and chemical affinity appeared to be established. To one of the Germans Oersted visited during his Wanderjahr, the decomposition of water by galvanic current not only meant that electric force and chemical affinity were identical, but that, contrary to the new chemistry of the French, water was an element rather than a compound. Johann Ritter demanded to know how the two alleged gaseous components of water could travel invisibly through solutions and appear at opposite poles? Hydrogen and oxygen, he claimed, both resulted from water having been acted upon differently by electrical force; i.e., water + electrical force could yield hydrogen or oxygen, depending on the manner of action.
Ritter had come to Jena to study medicine, and had been introduced to the members of the Romantic School by Johann Herder. While at Jena he attended Schelling's lectures, and despite differences with Schelling, retained the mark of the latter's influence throughout his life. In particular, Ritter insisted that there was a unity in the forces of nature, and pointed to the identity of electrical force and chemical affinity as living proof of this basic teaching from Schelling's nature philosophy.(7)
It was Ritter who was responsible for initiating Oersted's interest in experimental work on the relationship between electricity and magnetism. To a nature philosopher a relation was to be expected; specifically, electrical and magnetic forces were to be viewed as different expressions of one primary force of nature. Nature's unity demanded that the common ground resting at the foundation of these two external manifestations of the Urkraft, or primary force, would guarantee that electrical and magnetic force court be related.
That these two forces hat something to do with each other was suspected long before Schelling and his Naturphilosophie. Electrostatic and magnetic attraction and repulsion do, after all, act with similar effects. Seamen had noted that the magnetic needle of a compass was affected when ships were struck by lightning. Benjamin Franklin, the most famous theoretician of electricity of the eighteenth century, had magnetized needles by discharging them through a battery of Leyden Jars.(8)
In 1776 and 1777 the Bavarian Academy of Sciences had even offered a prize for the best essay on the question: Is there a physical analogy between electrical and magnetic force? In 1805, Just after Oersted's contact with Ritter in Jena, experiments involving the earth's magnetic properties were carried out. Hachette and Desormes attempted to determine whether swinging an electric pile within the interior of the earth produced any detectable effect. Finally, Oersted himself proposed in 1808 that a prize be offered for an answer to the question: What is the relation between electricity and magnetism? There is no record, however, that anything came of it.
That Oersted ant others were searching for the connection between electricity and magnetism in the early years of the nineteenth century should not be taken to mean that there was general agreement among scientist that the two phenomena were related. In 1802 the Frenchman Ampere claimed that he would demonstrate that electricity and magnetism resulted from two different fluids acting independently of each other. And Thomas Young in England wrote some five years later that "there is no reason to imagine any immediate connection between magnetism and electricity."(9)
Between 1807 and 1812 Oersted's interests were directed toward chemistry, culminating in 1812 with the publication of his Considerations of the Physical Laws of Chemistry Deduced from the New Phenomena.(10) Oersted's purpose in this work "was to bring the principles of nature philosophy into chemistry and show how they could clarify the problems which chemistry faced in 1813."(11)
While the specific details of Oersted's discussion of chemistry will not be analyzed here, two observations about the book are pertinent, both having to do with the particular principles of nature philosophy that were evident in Oersted's treatment.
One of Oersted's concerns was to uncover the higher principles of understanding under which the laws of chemistry stood. Both Kant and Schelling, as we have already seen, thought that it was necessary to discover a priori principles under which empirical generalizations could stand before the empirical generalizations could become laws of nature. Oersted agreed with Kane and Schelling that this preliminary philosophical task was prerequisite, and he was concerned to "attempt to perfect the chemical theory of nature through the reduction of all chemical actions to the primary forces (Urkräfte) from which they originate. We will then be in a position to derive all chemical properties from these primary forces and their laws. ... Chemistry will then become a theory of force."(12)
The unity of nature, which guaranteed that such primary principles existed, also was responsible for Oersted's conviction that manifestations of the primary forces of nature (static electricity, galvanism, magnetism, chemical affinity) were interrelated.
Electricity, magnetism, and galvanism now also belong to chemistry, as it appears that the very same fundamental forces which produce electrical, magnetic and galvanic effects, produce chemical effects in another form.(13)Secondly, Oersted sought in chemistry the polarity Schelling had claimed was inherent in all of nature. Recognizing that oxidation was a reaction of fundamental importance in chemistry, Oersted assigned it the role of one of two fundamental polar forces in nature. The other, opposite force was combustibility. Every body contained some of both of these forces. If a body possessed more force of combustion than of combustibility, then it burned in oxygen; but if it contained more force of combustibility, then other bodies burned in it.
Before we leave Oersted's Considerations, we ought to note that Oersted did treat magnetism briefly here in 1812. He concluded that the differences between electrical, galvanic, and magnetic action were more of degree than of kind, and suggested that one might be able to uncover an empirically observable connection between galvanic and magnetic force.
The Discovery of Electromagnetism in 1820
We may assume that in the years immediately following publication of Oersted's work on chemistry the Danish scientist continued to pursue his investigations into the elusive forces of electricity, magnetism, and chemical affinity. Interest in electrical phenomena continued to grow rapidly after Volta's discovery in 1820. Between 1800 and 1820, for example, there were at least 68 books, pamphlets, ant notices published in nine countries that were concerned with voltaic electrical experiments.(14)
Oersted's devotion to experimentation in these and subsequent years clearly differentiates him from his intellectual mentor Schelling. Although Schelling defended empirical knowledge(15) one also frequently encountered his unmistakable subjugation of empirical investigation to speculative physics. In Oersted the emphasis was inverted. In spite of Ritter's capacity for flights of imagination, Oersted may well have reinforced his appreciation of the importance of empirical research through his contact with Ritter at Jena.(16)
The actual discovery of electromagnetism was made during a lecture demonstration that Oersted was conducting for advanced students during the spring of 1820. It is perhaps the only case known in the history of science when a major scientific discovery was mate in front of a classroom of students.
Precise details of the discovery are not available. All that we have are three accounts by Oersted himself and scattered remarks of students, none of which agrees at every point with the others. Oersted, for example, speaks in his account from 1821 as if he were deliberately testing the effect of an electric current on a magnetic needle, but a student account asserts that the experiment concerned the heating of some platinum wire by means of an electric current, and that a compass needle happened by chance to be underneath the conducting wire. Another unexplained aspect of the story is Oersted's delay in pursuing the discovery for three months after the lecture. What follows is the earliest account Oersted composed.
Since for a long time I had regarded the forces which manifest themselves in electricity as the general forces of nature, I had to derive the magnetic effects from them also. As proof that I accepted this consequence completely, I can cite the following passage from my Recherches sur l'identité des forces chimiques et électriques, printed at Paris, 1813. "It must be tested whether electricity in its most latent state has any action on the magnet as such." I wrote this during a journey, so that I could not easily undertake the experiments; not to mention that the way to make them was not at all clear to me at that time, all my attention being applied to the development of a system of chemistry. I still remember that, somewhat inconsistently, I expected the predicted effect particularly from the discharge of a large electric battery and moreover only hoped for a weak magnetic effect. Therefore I did not pursue with proper zeal the thoughts I had conceived; I was brought back to them through my lectures on electricity, galvanism, and magnetism in the spring of 1820. The auditors were mostly men already considerably advanced in science; so these lectures and the preparatory reflections led me on to deeper investigations than those which are admissible in ordinary lectures. Thus my former conviction of the identity of electrical and magnetic forces developed with newclarity, and I resolved to test my opinion by experiment. The preparations for this were made on a day in which I had to give a lecture the same evening. I there showed Canton's experiment on the influence of chemical effects on the magnetic state of iron. I called attention to the variations of the magnetic needle during a thunderstorm, and at the same time I set forth the conjecture that an electric discharge could act on a magnetic needle placed outside the galvanic circuit. I then resolved to make the experiment. Since I expected the greatest effect from a discharge associated with incandescence, I inserted in the circuit a very fine platinum wire above the place where the needle was located. The effect was certainly unmistakable, but still it seemed to me so confused that I postponed further investigation to a time when I hoped to have more leisure. At the beginning of July these experiments were resumed and continued without interruption until I arrived at the results which have been published.(17)What is it that Oersted had discovered? Through persistent ant repeated efforts subsequent to the classroom experience Oersted clarified the precise nature of the effect a wire conducting electricity had on a magnetic compass. He found that a wire carrying an electric current affected a magnetic needle located below the wire by causing it to swerve to a position perpendicular to the wire. (Fig. 1)
Oersted's first inclination was to characterize the force affecting the needle as an attraction of some sort. But he found that moving the wire to the left or right, all the while keeping the wire parallel to the needle's original position, did not affect the nature of the deflection. Hence the force could not be an attraction between one pole and the wire, for in that event the attracted pole should follow the wire. (Fig. 2)
The needle did swing in the opposite direction in two situations: 1) when the wire was positioned beneath the needle, or 2) when the current was reversed in the wire. From these and other manipulations of the apparatus Oersted announced his conclusion regarding the force:
It is sufficiently evident from the preceding facts that the electric conflict is not confined to the conductor, but dispersed pretty widely in the circumjacent space. From the preceding facts we may likewise collect that this conflict performs circles; for without this condition it seems impossible that the one part of the uniting wire, when placed below the magnetic pole, should drive it towards the east, and when placed above it towards the west; for it is the nature of a circle that the motions in opposite parts should have an opposite direction.(18)The interaction between electricity and magnetism, referred to by Oersted as a "conflict" was unlike any Newtonian force before uncovered. It acted in circles around the conducting wire! The now familiar right-hand rule specifies the relationship between the direction of current and that of the magnetic lines of force: Grasp the conductor with the right hand so that the thumb points in the direction in which the current flows; the fingers encircle the wire in the direction of the lines of force. (Fig.3)
Oersted's discovery opened up undreamed of possibilities for research. Once this fundamental relationship was known, new theoretical advances and startling developments in electromagnetic technology began to be realized quickly. Electromagnetism is the foundation stone on which are built inventions such as the electromagnet ant the galvanometer. Shortly after Oersted's announcement the principle of electromagnetic induction was formulated by Michael Faraday in England, and this led to the development of the generator and ultimately the electric motor. Later in the century further theoretical discoveries identified light with the propagation of electromagnetic waves, revealing how yet another of the "imponderables" of the eighteenth century was related to the others, a fitting sequel to Oersted's strong belief in the unity of nature.
Ironically, Oersted's discovery had been predicted, and by none other than his old friend Ritter at Jena. In May of 1803 Ritter wrote to Oersted that events on earth could be related to the periodic occurrence of the maximum inclination of the ecliptic. Ritter suggested that when the ecliptic was inclined to its extreme, major discoveries in electricity had and would continue to take place. In 1745 the Leyden Jar had been invented by Kleist; in 1764 Wilcke had come up with the electrophorus; 1782 had produced the condenser; and 1801 was but one year after the discovery of the voltaic pile. He concluded: "You now emerge into a new epoch in which late in the year 1819 or 1820, you will have to reckon. This we might well witness."(19) Although Ritter died in 1810, Oersted not only witnessed the predicted advance, but was himself the perpetrator of it.
Copyright ©1998 Frederick Gregory
1. The report is that of Wilhelm Beetz, who related that Oersted personally told him of his debt to Schelling. Beetz is quoted in Robert Stauffer, "Speculation and Experiment in the Background of Oersted's Discovery of Electromagnetism," Isis, 48 (March, 1957), p. 35, n.8.
2. Ibid., p. 34.
3. The dissertation is discussed in Barry Gower, Speculation in Physics: The History and Practice of Naturphilosophie," Studies in History and Philosophy of Science, 3 (1973), pp. 340ff.
4. Immanue1 Kant, Prolegomena and Metaphysical Foundations. of Natural Science, trans. Belfort Box (London, 1903), p. 138.
5. Bern Dibner, Oersted and the Discovery of Electromagnetism (New York: Blaistell Pub. Co., 1962), p. 21
6. On Winterl, see H.A.M. Snelders, "The Influence of the Dualistic System of Jakob Joseph Winterl (1732-1809) on the German Romantic Era," Isis, 61 (1970), pp. 231-40.
7. On Ritter see Stauffer, op. cit., pp. 40-42; and Gower, op. cit., pp. 327-39.
8. Stauffer, op. cit., p. 40. Stauffer lists three other experimenters who had conducted similar tests, but without consistent results.
9. Ibid., p. 43.
10. This work, publishes in German in Berlin, was translated into French in 1813. A thorough analysis of its contents can be found in Gower, op. cit., pp. 339-49, ant in L. Pearce Williams, The Origins of Field Theory (New York: Random House, 1966), pp. 51-56.
11. Williams, op. cit., p. 51.
12. Quoted from the Considerations of 1812 in Gower, op. cit., p. 342.
14. Dibner, op. cit., p. 16, n.
15. Cf., for example, his Einleitung zu dem Entwurf eines Systems der Naturphilosophie of 1799, where he says: "The assertion that natural science must be able to deduce all its principles a priori is in a measure understood to mean that natural science must dispense with all experience, be able to spin all its principles out of itself - an affirmation so absurd that the very objections to it deserve pity. Not only do we know this or that through experience, but we originally know nothing at all except through experience, and by means of experience, and in this sense the whole of our knowledge consists of the data of experience. These data become a priori when we become conscious of them as necessary." in Sämtliche Werke, (Stuttgart: Cotta'scher Verlag, 1858), III, p. 278. Emphasis his.
16. For Schelling's criticism of Richter's "empirical philistinism, see Stauffer, op. cit., p. 41.
17. Quoted in Stauffer, op. cit., p. 45.
18. "Experiments on the Effect of a Current of Electricity on the Magnetic Needle." Translation of the original Latin account appearing in Annals of Philosophy (July 21, 1821). Pp. 71-76 in Dibner, op. cit., p. 75.
19. Quoted in Dibner, op.cit., p. 21.