Stefano Selleri
We briefly investigate an experiment carried out by Gian Domenico Romagnosi, in 1802, and concerning the deviation of a compass needle due to galvanic flow, indeed, cited by Ørsted himself, universally acknowledged as the discoverer of this phenomenon, in 1820, and try to understand why the former is unknown even to most of the specialists.
While writing a historical contribution published some time ago, in URSI Radio Science Bulletin [1], the author was browsing through the papers by Francesco Zantedeschi (Dolcè, Verona, Italy, 18 August 1797–Padova, Italy, 29 March 1873) in a search for clues on him possibly anticipating Michael Faraday’s (Southwark, London, United Kingdom, 22 September 1791–Hampton Court, Middlesex, United Kingdom, 25 August 1867) (Figure 1) discovery of the law of magnetic induction. In the event, I stumbled on another interesting piece of information, which tingled my curiosity and made me dig further in search of forgotten researchers.
Figure 1. (a) Francesco Zantedeschi. (b) Michael Faraday.
In a treatise published in 1859 [2], Zantedeschi defended the claims of Gian Domenico Romagnosi (Salsomaggiore Terme, Parma, Italy, 11 December 1761–Milan, Italy, 8 June 1835) on the priority of the discovery, in 1802, of the magnetic effect of the electric current, a discovery universally credited to Hans Christian Ørsted (Rudkøbing, Denmark, 14 August 1777–Copenhagen, Denmark, 9 March 1851), in 1820 [3],[4] (Figure 2).
Figure 2. (a) Gian Domenico Romagnosi. (b) Hans Christian Ørsted.
Actually, there are a few enigmatic lines, written by Ørsted himself in a long voice of an encyclopedia at the lemma “Thermoelectricity” [5], where the name “Romagnosi” is misspelled “Romanesi” (from [5] and Figure 3; the book by Aldini is [6]):
Aldini mentions, at the same place, that a certain Mr. Romanesi at Trent had confirmed the experiment of Mojon, and at the same time observed that galvanism makes the magnetic needle deviate.
Figure 3. A detail of [3, p. 575].
Before getting ahead on this, let’s have a look to Romagnosi’s life in the following section. The “Romagnosi’s Experiment” section will then investigate deeper his unrecognized discovery.
Gian Domenico Romagnosi was born in Salsomaggiore, then a city in the Duchy of Parma and Piacenza, northern Italy, on 11 December 1761. He began his education very young under the tutelage of his father, Bernardino.
From 1775 to 1782, he was at the Alberoni College of San Lazzaro of Piacenza, where he attended philosophy, theology, and morals courses. He eventually graduated in law, in Parma, on 8 August 1786, and became a notary in Piacenza the following 30 December. In those years, he took part in the meetings of the Literary Society of Piacenza, where he held a series of lectures in which he expressed his mission in life: the search for a “peaceful and calm enjoyment of goods of the civil order,” as we read in one of his notes.
In 1791, he published his first systematic work, Genesi del Diritto Penale (Genesis of Criminal Law). He was then an attorney in Trento for few years. From 1803 to 1806, he was a professor of natural and public law at the University of Parma, with little success among the students, who deserted his lessons.
In 1805, he published the Introduzione Allo Studio del Diritto Pubblico Universale (Introduction to the Study of Universal Public Law). In 1807, he was nominated a professor of civil law at the University of Pavia, a position he held for only two years, having then been appointed a professor, and the director, of the “School of high legislation in his relations with the public administration” in Milano.
In 1815, at the end of the Napoleonic Kingdom of Italy, he published, anonymously, Della Costituzione di una Monarchia Nazionale Rappresentativa (On the Constitution of a National Representative Monarchy), in which he outlines the general characteristics of public or political economy, which he would develop in the following years.
With the return of the Austrians to Lombardy, he was among the suspects of a conspiracy and allowed only private teaching in Milan. On 24 September 1822, his teaching permission was revoked.
Starting from 1827, until his death in 1835, he collaborated to produce the Annali Universali di Statistica (Universal Statistical Annals), published, in Milan, by Francesco Lampato. Indeed, Romagnosi proposed to devote himself to the studies of statistics and civil economy “a field in which almost everything remained to be redone” [7].
Editor’s Note
It is an interesting twist in electromagnetics that controversy surrounded the discovery of the two main effects linking electric currents and magnetic fields. One of these effects is the topic of this month’s column, by Stefano Selleri. He describes how the intellectual and jurist Gian Domenico Romagnosi, from Parma, Italy, had, in the early 19th century, proposed that current could have a magnetic effect. This was 15 years before the recognized demonstration by Hans Christian Ørsted, in 1820. The claim of priority for Romagnosi is based on reports in two Italian newspapers, in 1802. Apparently Romagnosi had seen the magnetic needle deflecting near a battery he built. However, Romagnosi neither published this work nor described the apparatus used for further scientific scrutiny. Later, there were similar claims for electromagnetic induction before Faraday’s actual demonstration and report, in 1831 These two instances go to show, once again, that full recognition for a claimed scientific advance normally comes only after full disclosure in recognized publications so that others can verify the claims.
The recognized discoverer of the production of a magnetic field by an electric current, Hans Christian Ørsted, was born in Denmark, on 14 August 1777. Ørsted was educated through a combination of home schooling and private tutors. At an early age, Ørsted helped in his father’s pharmacy and became interested in chemistry. In 1799, he graduated with a Ph.D. A year later, Alessandro Volta announced details of a battery that created a steady flow of electricity for the first time, using materials that were readily obtained. Ørsted entered into this new electrical science enthusiastically, and by 1801, he had published a scientific paper describing a new battery of his own. He was appointed a professor at the University of Copenhagen, in 1806, where he established a comprehensive physics and chemistry program.
Ørsted’s experiment demonstrating that a constant current and magnetism are linked took place during a lecture, on 21 April 1820. In this experiment, an electric current was passed through a wire, which caused a nearby magnetic compass needle to move. Over the next few months, Ørsted undertook further experiments, discovering that electric currents created a circular magnetic field around the wire. He announced his discovery, on 21 July 1820, in a paper written in Latin, with the English title “Experiments on the Effect of a Current of Electricity on the Magnetic Needle.”
Just as Volta’s invention of the battery opened new horizons in physics and chemistry, Ørsted’s discovery of a link between electricity and magnetism further added to the theory of electromagnetism. For his work, the British Royal Society awarded Ørsted the 1820 Copley Medal, which, at the time, was the most prestigious prize in science.
In this month’s column, we hear that electromagnetism was claimed by Francesco Zantedeschi, a Catholic priest and physicist, to have been discovered by Gian Domenico Romagnosi. The investigations by Selleri show that, looking at his method, it is clear Romagnosi’s experiment could not have worked as reported, as it did not have a closed circuit for an electric current. Without current, there can have been no electromagnetic effect. It is thought that the needle deflection in Romagnosi’s experiment was probably due to a buildup of static electric charges on the needle.
In a similar fashion, it has been claimed that electromagnetic induction was discovered earlier, in 1829, by Francesco Zantedeschi and, in 1830, by Joseph Henry. Crucially, neither of them published their findings or described their experimental apparatus immediately for others to verify. However, Michael Faraday did do this, on 29 August 1831, by publishing his results first, and he is credited as discovering electromagnetic induction. Therefore, the magnetic field created by a current is Ørsted’s discovery, and is called Ørsted’s law, and electromagnetic induction is Faraday’s law.
So, what has a jurist, among the highest Italian intellectuals of 18th and 19th centuries, father of many reforms in what would later become the Italian judicial system, to do with electromagnetism?
It happens that in those early days, learned people tended to be polymaths, and they tended to look in all fields that attracted their curiosity. And Romagnosi indeed carried out at least one experiment, which he deemed worthy of publication, a couple of times, although the results were published in obscure local journals [8], [9]. These would have gone unnoticed were it not that Giovanni Aldini (Bologna, Italy, 10 April 1762–Milan, 17 January 1834) reported explicitly, in his treatise Sur le Galvanisme [6] (which he signed as Jean Aldini), that “M. Romanesi [Romagnosi misspelled] physicist in Trento, has observed the galvanism divert the magnetic needle” (Figure 4).
Figure 4. A detail of [6, p. 340].
And it is this sentence by Aldini that Ørsted cites in [3], as mentioned in the preceding. Yet, it is highly improbable that Ørsted could have read Romagnosi’s papers [8], [9], both in Italian and in local journals. Otherwise, he would not have repeated Aldini’s error in spelling Romagnosi’s name. And he would have not credited the work to have happened in 1804, as given in Aldini’s momoir, rather than using the correct date of 1802.
Similar errors can be found in an essay by Joseph Izarn (Cahors, France, 10 January 1766–Paris, France, 22 November 1847) ([10, p. 120]). Both Aldini and Izarn also cite the experiment by Giuseppe Mojon (Genova, Italy, 27 August 1772–Genova, 21 March 1837). The experiment by Mojon consisted, as it is possible to reconstruct from its secondhand descriptions [6], [10], in a closed circuit, where a needle was part of the circuit and the needle, after a certain time, appeared to be magnetized.
Figure 5 reports two excerpts, one from the first paper by Romagnosi [8], who would later publish a second memoire [9], essentially with the same content, and from a book by Gilberto Govi (Mantova, Italy, 21 September 1826–Roma, Italy, 29 June 1889) [11], who published a paper on Romagnosi’s experiment more than 60 years later, quoting large part of [8] and adding explanations and figures.
Figure 5. (a) A part of [8]. (b) A part of [11], with a much more readable text, exactly quoting [8] and with a drawing by the author of [11], clarifying the setup.
It is worth noting, from our modern point of view, that Romagnosi could never have observed what Ørsted would have observed 18 years later because he specifically stated that he was working with an open circuit (from [8] and [11] and Figure 5):
I connected to Volta’s pile a silver chain, the last segment of the chain being in an insulating glass tube and ending in a silver button. I placed a magnetic needle over a glass insulator close to the pile. By holding the chain from the glass tube and getting the silver button to touch for a few seconds the magnetic needle, this latter diverged from the original position for a few degrees, a position in which the needle remained still after the chain was removed.
Hence, there was no current flow and no possible magnetic effect. Notwithstanding some defenses of Romagnosi’s priority over Ørsted [11], Govi, in [12], commented on Giuseppe Belli (Calasca, Domodossola, Italy, 25 November 1791–Pavia, Italy, 1 June 1860) and also stated in [13], and the author believes from the description in [8] and [9], that it is apparent that there was no closed circuit for a current to flow, so whatever Romagnosi observed was not a magnetic effect of currents.
The movement of the needle must have been accidental due to the button’s movements or, at the very best, due to the contact between the silver button and the needle, which brought this latter to the same potential as the button itself, and as the button was moved away, the two metallic objects, at the same potential and hence sharing the same charge, would have repelled each other. This is, anyway, unlikely, due to the minimal capacity of the needle [13], or perhaps the phenomenon could have been due to the glass tubular handler, which could have been electrostatically charged [12]. The needle then resting a few degrees from its original position after the contact with the pile ended due to friction. The same opinion is expressed in a more recent book [14], while another modern researcher relegates Romagnosi to a footnote [15].
Other contemporary authors claim that since Romagnosi writes that he was touching the compass case with his other hand [9], his physical contact was enough to close the circuit and have a current flow [2], [11]. Now, besides the low reliability of the author of [2] and [11] (as shown in [1]), it must be noted that Romagnosi, in [9], states that this contact was made a second time and that its effect was to cancel the deviation, which could very well have been due to a realignment to Earth’s magnetic field if touching transferred some slight movement to the case, sufficient to win the friction among the needle and the supporting pin.
The key point is, even if Romagnosi talks of “Galvanic Flow,” a concept of those early days in electricity, no true closed circuit was present. The effect would not, in any case, have been that observed by Ørsted, where the wire makes a well-closed circuit, never touching the needle, and the effect is perpendicular to the current flow and not a result of repulsion.
A very interesting analysis can be found in a recent paper [16], where an in-depth study of the original papers and letters still available concerning Romagnosi’s experiment is carried out. In that paper, some questions on Romagnosi are answered, but many more are raised. Indeed, Romagnosi’s experiment could not have generated much attention, due to being “too early” [17], but times were indeed ripe, and even if his experiment was not the right one, if it were more widespread, it could have accelerated interest in this area. As Ørsted himself wrote, in 1830 ([3] and Figure 3):
It is, therefore, not surprising, that neither the French Institute, nor the learned societies, nor the numerous natural philosophers took any notice of this observation [Romagnosi’s experiment as reported by Aldini], which would have accelerated the discovery of electromagnetism by sixteen years.
Accelerated in the sense that even an obscurely described experiment could have lit the spark in other researchers and led to success earlier.
It is interesting how even fairly recent events in our history can be difficult to verify, and this Romagnosi experiment is one of these and not the only one [18]. Perhaps if he had described more clearly his setup and published it in more widespread journals, someone else could really have anticipated Ørsted’s 1820 discovery, and the history of electromagnetics could have taken a different path.
Stefano Selleri (stefano.selleri@unifi.it) is an associate professor of electromagnetic fields with the Department of Information Engineering, University of Florence, 50139 Firenze Italy. Besides research, he is also active in the field of telecommunications and electromagnetism history. He is a Senior Member of IEEE.
[1] S. Selleri, “Faraday-Neuman-Lenz law of induction or Zantedeschi-Neuman-Lenz law of induction?” URSI Radio Sci. Bull., vol. 2017, no. 363, pp. 73–76, Dec. 2017, doi: 10.23919/URSIRSB.2017.8409433.
[2] F. Zantedeschi, L’elettromagnetismo Rivendicato a Giandomenico Romagnosi e All’Italia [Electromagnetism Claimed to Giandomenico Romagnosi and Italy] . Trento, Italy: Monauni, 1859.
[3] A. Savini and B. Bowers, “From Oersted to Ampere: 1820, Annus Mirabilis for the electric sciences [Historical Corner] ,” IEEE Antennas Propag. Mag., vol. 62, no. 5, pp. 138–142, Oct. 2020, doi: 10.1109/MAP.2020.3012943.
[4] O. M. Bucci, “Electromagnetism without fields: From Ørsted through Ampère to Weber [Historical Corner] ,” IEEE Antennas Propag. Mag., vol. 62, no. 4, pp. 128–137, Aug. 2020, doi: 10.1109/MAP.2020.2998847.
[5] H. C. Ørsted, “Thermo-electricity,” in Edinburgh Encyclopaedia, vol. 18, D. Brewster, Ed. Edinburgh, U.K.: Blackwood, 1830, pp. 573–589.
[6] J. Aldini, Essai Théorique et Expérimental Sur le Galvanisme Avec Une Série D’Expériences [Theoretical and Experimental Essay on Galvanism With a Series of Experiments] . Paris, France: Imp. De Fournier et Fils, 1804.
[7] R. Ghiringhelli and F. Invernici, Per Conoscere Romagnosi [To Meet Romagnosi] . Milano, Italy: Unicopli, 1982.
[8] G. D. Romagnosi, Articolo Sul Galvanismo [Article on Galvanism] . Trento, Italy: Ristretto de’ Foglietti Universali, Aug. 3, 1802.
[9] G. D. Romagnosi, Articolo Sul Galvanismo [Article on Galvanism] . Rovereto, Italy: Foglietti Universali, Aug. 13, 1802.
[10] J. Izarn, Manuel du Galvanisme [Galvanism Handbook] . Paris, France: Levrault Schoell, 1805.
[11] F. Zantedeschi, “Saggi Dell’Elettromagnetico,” Venezia, Italy: Tip. Armena di San Lazzaro, 1839.
[12] G. Govi, “Romagnosi e l’Elettro-Magnetismo [Romagnosi and Electromagnetism] ,” Atti Della R. Accademia Delle Scienze di Torino, vol. 4, pp. 426–437, Aug. 1869.
[13] G. Belli, “Saggi dell’elettro-magnetico di Francesco Zantedeschi [Essays on Electro-Magnetism by Francesco Zantedeschi] ,” Biblioteca Italiana J., vol. 98, pp. 48–63, Apr. 1840.
[14] R. Appleyard, Pioneers of Electrical Communication. London, U.K.: McMillan, 1930.
[15] R. C. Stauffer, “Speculation and experiment in the background of Oersted’s discovery of electromagnetism,” Isis, vol. 48, no. 1, pp. 33–50, Mar. 1957, doi: 10.1086/348537.
[16] S. Stringari and R. R. Wilson, “Romagnosi and the discovery of electromagnetism,” Rendiconti Lincei. Scienze Fisiche e Naturali, vol. 11, no. 2, pp. 115–136, 2000, doi: 10.1007/BF02904378.
[17] B. Dibner, Oersted and the Discovery of Electromagnetism. New York, NY, USA: Blaisdell, 1963.
[18] G. Pelosi and S. Selleri, “Recent outcomes of the investigations on Guglielmo Marconi supposed experiments in Switzerland,” in Proc. 6th IEEE History Electrotechnol. Conf. (HISTELCON), 2019, pp. 11–13, doi: 10.1109/HISTELCON47851.2019.9040021.
Digital Object Identifier 10.1109/MAP.2022.3223635