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ABSTRACT
Today, we take international collaborations as a necessity, but 150 years ago, when travel was not so convenient, it involved an enduring and time-consuming challenge. This paper presents letters and reports written by German physicist Julius Plücker to his wife, Antonie née Altstädten describing his travels to Great Britain and France between 1853 and 1866. These letters provide a view into how international collaboration and communication were developed and maintained as well as how friendships were built within the scientific community during the early industrial age, prior to telegraph, telephone, email, and internet.
KEYWORDS:
Acknowledgement
I would like to express my appreciation to the Canadian National Research Council’s archive and the University of Bonn’s archive for providing easy and fast access to files and documents regarding Julius Plücker in their collections. I am deeply indebted to Ewa Kaminski and Brigitte Roos for their tireless help in deciphering the somewhat challenging handwritings of Plücker and his correspondents. I am also grateful to many people for providing important background information: Wolfgang Alt for discussions about Plücker’s early days at the University of Bonn. Professor David Cahan for his discussion on the relationship between Hermann Helmholtz and Julius Plücker, Roland Jackson for the enlightening and informative discussions about the relationship between Plücker and John Tyndall, Hans Reinhard Koch for information about Plücker’s student days and his brother-in-law August Altstädten, David Rowe for discussions on Plücker’s mathematics; Doris Warnecke for the unpublished reports and notes of her husband (deceased) on the research of both Plücker and Beer in optics. Finally, I want to thank Elizabeth Jo for her careful reading and editing of the manuscript.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Notes
1 Michael Faraday – Julius Plücker letters, ϵpsilon: The Michael Faraday Collection, <https://epsilon.ac.uk/search?sort=date&f1-contributor=Faraday%20Project&expand=correspondent> [accessed 27 February 2022].
2 Michael Wiescher, ‘Julius Plücker, Familie und Studienjahre’, Sudhoffs Archiv, 100 (2016), 52–82.
3 In a letter to John Tyndall from 18 January 1868, one year after Plücker’s death, Helmholtz wrote ‘She [Tyndall’s theory] has been thrown into confusion by such mad heads as Plücker’. (Royal Institution Archive: RI MS JT/H/46). In a letter exchange with the mathematician Rudolf Lipschitz (1832–1903) on the prospect of getting Helmholtz back to Bonn as Plücker’s successor, Helmholtz as well as Lipschitz dismissed Plücker and his scientific achievements on several occasions; Helmholtz characterized Plücker’s position in Bonn in a letter from 7 June 1868, ‘Plücker has apparently let his position go to waste, and must have bored the students to tears, […]. This may suggest that […] he did not like to give lectures, but rather devoted his time to literary works’. Lipschitz responded a day later, ‘since [18]64, he [Plücker] couldn’t think about anything, but his geometry work, everything else he considered a real nuisance’. C.f. Herbert Hörz, Hermann von Helmholtz und die Bonner Universität (Berlin: Wisssenschaftshistorische Manuskripte 3, 1995).
4 Ludwig Immanuel Magnus (1790–1861) was a German Jewish mathematician who, in 1831, published a paper on transformation in a coordinate system, a topic closely related to Plücker’s interests in geometry. For this work, Magnus was honoured in 1834 with an honorary doctorate, sponsored by Diesterweg and conferred on him by the University of Bonn.
5 Plücker did, however, serve as a representative of the University of Bonn when he sat on a committee called by the Prussian ministry. The committee’s task was to reform and liberalize Prussia’s university laws in response to the revolutionary events of 1848. C.f. Verhandlungen der Conferenz zur Berathung von Reformen in der Verfassung und Verwaltung der preußischen Universitäten (Berlin: Besser, 1849).
6 By marrying Helene Glasmacher, Moritz Rudolf Plücker developed close business and personal ties with the two most successful textile manufacturers in Gladbach, Adam Quirin Croon, an uncle of his wife, and her brother-in-law Johann Peter Bölling (Cf. M. Wiescher, ‘The Family of Friederika Margaretha Bölling’, in Jahrbuch 2014 der Westdeutschen Gesellschaft für Familienkunde, ed. by Karl G. Oehms, Bs. 291 (Cologne, 2014), pp. 235–86). These influential relatives were also godparents for the first son of the same name, Moritz Rudolf Plücker (1836–1902), who continued and expanded the company.
7 This emigration attempt was made together with Plücker’s brother-in-law who was more successful, establishing a business trading rare botanical and geological objects with the University of Bonn’s faculty. C.f. Michael Wiescher, ‘Rheinische Bürgersöhne in Texas’, Düsseldorfer Jahrbuch, 87 (2017), 101–52.
8 Plücker’s grasp of English was limited and his pronunciation was poor as commented upon by Helmholtz in a letter to his wife. (C.f. Richard L. Kremer, Letters of Hermann von Helmholtz to his wife – 1847–1859, letter 33, 134.) Faraday’s French was much better than his German, therefore Plücker’s letters were formulated in French.
9 Plücker’s initial goal was to study the so-called ‘cameral sciences’, which summarize practical education in all sorts of applied disciplines with a goal toward becoming a technical administrator in the Prussian government. Mathematics was part of this training programme and Plücker eventually turned entirely to a purely academic career in the field.
10 Fritz Krafft, ,Dokumente zu Julius Plückers Marburger Promotion ‘in absentia‘, in Studien zur Wissenschafts- und Technikgeschichte, ed. by Form, Zahl, Ordnung (Stuttgart: Franz Steiner Verlag, 2004), pp. 415–25.
11 Joseph Dietz, ,Aus dem Tagebuch des Bonner Dozenten Dr. Franz Baumann (1825–1826)‘, Bonner Geschichtsblätter, 25 (1973), 120–98.
12 Journal für die reine und angewandte Mathematik (often simply called Crelle’s Journal, after the first editor) was founded in 1826, in Berlin, by the mathematician August Leopold Crelle (1780–1855). Cf. Wolfgang Eccarius, ,August Leopold Crelle als Förderer bedeutender Mathematiker‘, in Jahresbericht der deutschen Mathematiker-Vereinigung [Annual Report of the German Mathematical Society], 79 (1977), 137–74.
13 W. Eccarius, ,Der Gegensatz zwischen Julius Plücker und Jakob Steiner im Lichte ihrer Beziehungen zu August Leopold Crelle : Hintergründe eines wissenschaftlichen Meinungsstreites‘, Annals of Science 37 (2), (1980), 189–213.
14 Julius Plücker, System der Geometrie des Raumes in neuer analytischer Behandlungsweise, insbesondere die Theorie der Flächen zweiter Ordnung und Classe enthaltend (Düsseldorf: Schaub’sche Buchhandlung, W. H. Schellen, 1846).
15 Mechthild Ulrike Plump, Julius Plücker – Leben und Werk eines analytischen Geometers im 19. Jahrhundert (Doctoral thesis, Wuppertal, 2014).
16 William Rowan Hamilton (1805–1865) published as a young student several mathematical papers in the Transactions of the Royal Irish Academy. He demonstrated that the propagation of light along an optic axis of a crystal depends on the symmetry of the crystal. The beam does not change if the crystal is optically uniaxial. However, if the crystal is optically biaxial then the beam is radically transformed into a conical ring, a phenomenon that was called conical refraction. Cf. J. G. O’Hara, ‘The Prediction and Discovery of Conical Refraction by William Rowan Hamilton and Humphrey Loyd (1832–1833)’, Proceedings of the Royal Irish Academy. Section A, 82 A, 2 (1982), 231–57 and James G. Lunney and Denis Weaire, ‘The ins and Outs of Conical Refraction’, Europhysics News, 37.3 (2006), 26–29.
17 Julius Plücker, ‘Discussion de la forme générale des ondes lumineuses’, Crelle’s Journal d. M. Bd XIX, Hft, 1 (1839), 1–44.
18 August Beer (1825–1863) went to Bonn to study mathematics and the sciences under Julius Plücker, later becoming his assistant. Beer initially concentrated on optics and formulated the law of absorption of light in media; he later expanded to the field of electromagnetism. He published textbooks in both areas, Plücker publishing the latter in Beer’s name after his death. The textbook Einleitung in die höhere Optik (Braunschweig: Vieweg, 1853), provides a detailed summary and mathematical analysis of the laws on reflection and refraction of light waves on complex crystals, in which Beer frequently gives Plücker credit for the mathematical derivations. The postumus published textbook Einleitung in die Elektrostatik, die Lehre vom Magnetismus und die Elektrodynamik (Braunschweig: Vieweg, 1865) gives Plücker considerable credit as well.
19 Roland Jackson, ‘John Tyndall and the Early History of Diamagnetism’, Annals of Science, 72.4 (2015), 435–89.
20 Falk Müller, Gasentladungsforschung im 19. Jahrhundert (Berlin, 2004), 45; Günter Dörfel and Falk Müller, ,Julius Plücker, Heinrich Geißler und der Beginn systematischer Gasentladungsforschung in Deutschland‘ (Basel, 2006), 38 in NTM International Journal of Histoy & Ethics of Natural Sciences, Technology & Medicine, vol. 14, 26–45, and Frank A.J.L. James, ‘The Study of Spark Spectra 1835–1859’, Ambix, 30 (1983), 137–62.
21 Johann Wilhelm Hittorf (1824–1914) was a German physicist who studied in Bonn under the guidance of Julius Plücker and graduated in 1846. A year later, he became Privatdozent at the University of Bonn but, shortly after that, he moved to the Royal Academy of Münster as a teacher. When the school became a university in 1843, he was appointed professor of chemistry and physics. Falk Müller, ‘Johann Wilhelm Hittorf and the Material Culture of Nineteenth-Century Gas Discharge Research’, The British Journal for the History of Science, 44.2 (2011), 211–44.
22 Alfred Clebsch, ,Zim Gedächnis an Julius Plücker (Obituary)‘, Abhandlungen der königlichen Gesellschaft der Wissenschaften zu Göttingen (Göttingen, 1871), 33.
23 This statement actually reflects the view of experimental physicists during the first half of the nineteenth century, who were goal-oriented instrument builders measuring things themselves. Plücker more closely resembles the picture of many modern experimentalists who lead a team, generate funding, head the planning process, and design the necessary instrumentation, while the team does the actual measurement.
24 Klaus Hentschel, Mapping the Spectrum: Techniques of Visual Representation in Research and Teaching (Oxford University Press, 2002).
25 Friedrich Fessel, Beilage zu den Plücker’schen Inductions-Apparaten (Cöln: Friedrich Greven Druck, 1853).
26 Günter Dörfel and Falk Müller, ,1857 – Julius Plücker, Heinrich Geißler und der Beginn systematischer Gasentladungsforschung in Deutschland‘, N.T.M., 14 (2006), 26–45.
27 Archive of the National Research Council of Canada, Ottawa [NRC] Plücker Collection, six volumes.
28 Julius Plücker, ,Über das Ohmsche physicalische Gesetz‘, Journal für Reine und angewandte Physik, 35 (1847), 93–99.
29 Charles Wheatstone, ,Beschreibung verschiedener neuer Instrumente und Methoden zur Bestimmung der Constanten einer Volta’schen Kette‘, Poggendorfs Annalen, 62 (1843), 499–543.
30 Michael Wiescher, ,Julius Plücker: Kaufmann? Nein danke! Der Bonner Mathematiker und Physiker Julius Plücker (1801–1868)‘, Bonner Geschichtsblätter, 67 (2017), 169–206.
31 Johann Adolf Maria Altstädten (1792–1852) was, during the Napoleonic era, in charge developing the cadaster in Bonn and he developed an interest in geometry methods and applications.
32 Richard L. Kremer, Letters of Hermann von Helmholtz to his wife – 1847–1859, letter 28 (Stuttgart: Steiner Verlag, 1990), 107.
33 NRC, vol. 5, letters to his wife 1853–1867.
34 Hermann Helmholtz was still Professor for Physiology in Königsberg at that time. His invention of the ophthalmoscope, two years earlier, brought him recognition while Tyndall’s translation of Helmholtz’s fundamental work on the conservation of force into English made him a well-known figure in Britain. David Cahan, ‘Helmholtz and the British Scientific Elite: From Force Conservation to Energy Conservation’, Notes and Records: the Royal Society Journal of the History of Science, 66 (2012), 55–68.
35 Helmholtz also mentions this meeting in his letters to his wife. At the time he was very interested in leaving Königsberg to find a position in the Rhineland, since he considered the harsh climate conditions of the Baltic to be dangerous for his wife’s lung conditions. It is not clear if this journey provided an opportunity to discuss such an issue. Cf. Richard L. Kremer, Letters of Hermann von Helmholtz to his wife – 1847–1859, letter 32 (Stuttgart: Steiner Verlag, 1990), p. 130.
36 In Swansea, Plücker had attended the BAAS meeting in 1848 and presented his ideas: Julius Plücker, ‘Account of Experiments belonging to a new Magnetic Action’ in Report of the Thirty-Fifth Meeting of the British Association to the Advancement of Science, held in Swansea 1848 (London, 1849), 2.
37 John Phillips (1800–1874) was an English geologist who was instrumental in the mapping of Britain’s geological strata and other features.
38 William Robert Grove (1811–1896) was a professor for experimental philosophy at the London institution. He was broadly interested in a wide range of physical phenomena, developing a first voltaic battery and the first version of incandescent electric light, as well as developing photographic techniques. Prior to Helmholtz, Grove anticipated the general theory of the conservation of energy.
39 Edward Sabine, an army officer and explorer was at that time President of the Royal Society and permanent trustee of the British Association. In 1859 he rose to the rank of Mayor-General.
40 George Gabriel Stokes (1819–1903) was Lucasian Professor of Mathematics at Cambridge and also, to complement the poor pay, he became Professor of Physics at the Government School of Mines in London in 1855. He was instrumental in the development of the mathematical principles of hydrodynamics. In 1852, Stokes also labelled and tried to explain the phenomenon of fluorescence by absorption and emission of light after the illumination of molecules. In 1854, this led him to an explanation of the Fraunhofer lines in the solar spectrum. He suggested these were caused by atoms absorbing certain wavelengths in the Sun’s outer layers. This work may have further stimulated Plücker in his investigations of luminous gases.
41 John Stevelly (1795–1868), Prof of Natural Philosophy at Queen’s College, Belfast.
42 Karl Heinrich Detlev Bödeker (1815–1895) was a German chemist who studied in Göttingen and in Bonn where he was Privatdozent until 1854, before serving as professor and chair for physiological chemistry in Göttingen.
43 Albert Plücker (1838–1901) was the only son of Julius Plücker. Cf. Michael Wiescher, ‘Julius Plücker: Kaufmann? Nein danke! Der Bonner Mathematiker und Physiker Julius Plücker (1801–1868)‘.
44 The phenomenon was first observed in 1778 by the young Dutch student Sebald Justinus Brugmans (1763–1819) that materials like bismuth and antimony – unlike paramagnetic and ferromagnetic materials – were repelled by a magnetic field. In 1845, Michael Faraday also observed the phenomenon on glass and other materials and searched by experiment for a scientific explanation of the phenomenon, which was later called diamagnetism. (c.f. Roland Jackson, ‘John Tyndall and the Early History of Diamagnetism’, Annals of Science 72, 436–38.) The reason for the experiments that Plücker spoke about was study of the origins and nature of diamagnetism, which is, as we know today, a quantum mechanical effect whereby electrons in the material are set in spinning motion, inducing a magnetic field in the opposite direction of the external field. This causes a repulsive force.
45 This is indeed the case since the nature of magnetic characteristics depends on the alignment of the magnetic moment with the external field. The magnetic moment depends on the quantum structure of the materials which can cause different effects and reactions with respect to the external field.
46 ‘Report of the Twenty-Third Meeting of the British Association for the Advancement of Science, held in Hull in 1853’ in Notices and Abstracts (London, 1854), 7–8.
47 Brian Bowers, ‘Sir Charles Wheatstone FRS 1802–1875’, History of Technology, 29 (1975/2001).
48 ,Letter Benzenberg to Plücker 1829‘, NRC vol. 5, 10–12.
49 Michael Wiescher, ,Johann Friedrich Benzenberg als Naturforscher zwischen Revolution und Restauration‘, Düsseldorfer Jahrbuch 89 (2019), 9–65.
50 Julius Plücker, ,Über das Ohmsche physicalische Gesetz‘ Journal für Reine und angewandte Physik, 35 (1847), 93–99.
51 Thomas Graham (1805–1869) was a chemistry professor at the University of London, known for his pioneering work in gas diffusion. In 1862 he won the Copley Medal of the Royal Society.
52 Charles Wheatstone, ‘On Fessel’s Gyroscope’, Proceedings of the Royal Society of London, 7 (1856), 743–48.
53 Abbé François-Napoléon-Marie Moigno (1804–1884) was a French Jesuit priest, as well as a mathematician and physicist who published numerous scientific articles on questions of optics, electricity, and electrotechnical applications. He and Plücker had a good professional and also personal relationship. Cf. Obituary, ’L’Ábbe Moigno’, Nature, 30 (1884), 291–92.
54 Border and custom station.
55 This presumably refers to Bertram Friedrich August Maria Altstädten (1814–?), brother of Plücker’s wife. August emigrated in 1845 with several friends, including Plücker’s younger brother Emil, to the Republic of Texas. He led an adventurous life, joining the Texas Rangers under the command of Colonel Jack Coffee Hays (1817–1883), and was considered killed in the Mexican-American war in 1848. This letter might suggest that Altstädten survived and moved, in 1849 with Colonel Hays, to California to settle there. Unfortunately, the letter does not provide any more detailed information. Cf. Michael Wiescher, ,Rheinische Bürgersöhne in Texas‘, Düsseldorfer Jahrbuch, 87 (2017), 101–52.
56 Indeed, François Arago (1786–1853), French-Catalan mathematician, physicist, astronomer at the École Polytechnique, and lifelong friend of Alexander von Humboldt, died on 2 October 1853, the same day the letter was written.
57 Roland Jackson, The Ascent of John Tyndall (Oxford University Press, 2018), 69.
58 For a more detailed discussion of this debate see Roland Jackson, The Ascent of John Tyndall, 52–108.
59 Another reason may have been France and Great Britain’s involvement in the Crimean War (1853–1856) during this time. However, there is no indication in Plücker’s notes and letters that this distant war – between Britain and France on one side, supporting the Ottoman Empire, with Russia on the other side – was a matter of concern for Plücker.
60 Johann Friedrich Eduard Bobrik (1802–1870) received his habilitation at the University of Bonn in 1829 and taught there at the same time as Plücker. Bobrik served as Privatdozent until he was appointed as Professor of Philosophy in Zürich, where he stayed until 1856.
61 Heinrich Frey (1822–1890) studied medicine with a focus on entomology in Bonn and Göttingen, before moving to Zürich as Professor of Medicine.
62 Anton Schrötter von Kristelli (1802–1875) was an Austrian chemist and mineralogist with great interest in physics. He studied with Liebig and later became one of the co-founders of the Imperial Academy of Science in Austria, which was formed following the example of the Royal Society. Schrötter frequently invited Plücker to Vienna. C.f. Alexander Bauer, Antom Schröter, Ritter v. Kristelli (Wien, Hölder Verlag, 1917).
63 Quoted after Roland Jackson, John Tyndall, 108.
64 ‘Faraday3258’, in ϵpsilon: The Michael Faraday Collection, <https://epsilon.ac.uk/view/faraday/letters/Faraday3258> [accessed 15 April 2022].
65 August Wilhelm von Hofmann (1811–1892) is another example of the strong interaction between British and German scientific communities. He studied chemistry under Justus von Liebig in Gießen and, after earning his PhD in 1841, was nominated as the first director of the new Royal College of Chemistry in London. Hofmann stayed for twenty-three years, building a program in organic chemistry before leaving England to accept a faculty position at Bonn University in 1864. However, only one year later he was appointed Professor for Chemistry at the University of Berlin.
66 John Percy, MD, FRS (1817–1889) was a medical doctor, chemist and metallurgist. Roberts-Austen, ‘W. John Percy, M.D., F.R.S.’, Nature 40 (1889), 206.
67 John Peter Gassiot (1797–1877) was an English entrepreneur and amateur scientist. He was particularly associated with public demonstrations of electrical phenomena and the development of the Royal Society. He maintained a large private laboratory, which was also used by Maxwell to perform many of his experiments.
68 Klaus Kemp and Reinhard Schmoeckel, ,150 Jahre Eisenbahn in Bonn‘, Bonner Geschichtsblätter 34 (1994), 173–224.
69 This is the newly opened train station in Cologne, through which the railway connection between Bonn and Cologne was facilitated <https://de.wikipedia.org/wiki/Rheinuferbahn>.
70 This probably reflects Plücker’s upbringing in a protestant household in Elberfeld. Elberfeld was a conservative town ruled by the principles of the reformed church, which abhorred anything remotely Catholic.
71 Plücker grew up in the Dutch Reformed atmosphere of his father’s family, despite his mother being Lutheran.
72 William Hyde Wollaston, MD, FRS (1766–1828) was a British physician, chemist, and physicist who attributed motion sickness to motion-induced fluctuations in the pressure within cerebral blood vessels, causing dizziness and lightheadedness. Professionally, Plücker was probably more interested in Wollaston’s contributions to crystallography and his chemical secrets for extracting palladium and platinum from minerals.
73 3 April 1858.
74 Faraday was in Brighton at the time, seeking to recover from his health problems. He answered immediately on 7 April and arranged for a meeting with Plücker after his return on Saturday, 10 April, ‘Faraday3414’, in ϵpsilon: The Michael Faraday Collection, accessed 21 March 2022.
75 The Reverend John Barlow (1798–1869) was an Anglican priest and close friend of Michael Faraday, serving as secretary of the Royal Institution from 1843 to 1860. He was known as a socially well-connected person and was instrumental in persuading many of mid-Victorian London’s elite society, from Prince Albert to the Duchess of Northumberland, to join the Royal Institution.
76 This is most likely Marie von Salomon, daughter of university magistrate and judge Friedrich von Salomon (1790–1861) who was known well beyond Bonn for his strictness in disciplining the unruly student community in Bonn.
77 It is argued that the fences were actually mended in 1858, brokered by August Wilhelm von Hofmann, but even in that case, Plücker did not attend any British Association meetings for some time to come. Roland Jackson, The Ascent of John Tyndall, 108.
78 Hermann Helmholtz had moved from Bonn to Heidelberg and was also invited to participate in the British Association meeting. He decided not to attend because he did not want to leave his sick wife alone during the time of the Franco-Austrian war for Italian independence in 1859, David Cahan, Helmholtz: A Life in Science (University of Chicago Press, 2018).
79 Cf. Klaus Hentschel, ed., Unsichtbare Hände (Stuttgart: GNT Verlag, 2008).
80 This was very common in the nineteenth century French science community. Instrument maker’s workshops served as meeting points for scientists, where they could see the latest developments or results and present their own experimental discoveries. Christine Blondel, ‘Electric Instruments in 19th France, between Makers and Users’, History and Technology, 13 (1997), 157–82.
81 In the end, Plücker paid for his travels from his own pocket. Travel reimbursement, as known by the modern scientist, was only possible on the rarest occasion. This involved a long and tedious request process, with arduous justification letters, and had to be personally approved by the Prussian Minister of Education.
82 Moritz Hermann von Jacobi (1801–1874) was a Prussia born scientist working as a Russian Imperial engineer and physicist in St. Petersburg. Jacobi was mainly interested in electricity applications such as galvanoplastics, electric motors, and wire telegraphy, which overlapped closely with Moigno’s scientific interests.
83 Emile Verdet (1824–1866) was a French physicist. He worked in magnetism and optics, editing the works of Augustin-Jean Fresnel. Verdet did much to champion the early theory of the conservation of energy in France.
84 The two names could not be deciphered.
85 Plücker left it open as to whom he was referring but presumably it was one of his co-workers in Bonn, such as Beer or Geißler.
86 Michel Chasles (1793–1880), French geometer and mathematician, winner of the Copley Medal in 1865. He had shown that there was a mistake in Jakob Steiner’s derivations, which presumably very much endeared him to Plücker.
87 Louis Jules Duboscq (1817–1886) was a French instrument maker, inventor, and pioneering photographer. He was known in his time, and is remembered today, for the high quality of his optical instruments.
88 Henri Hureau de Sénarmont (1808–1862) was a French mineralogist and physicist.
89 Louis Nicolas Grandeau (1834–1911) was a French chemist and agronomist living in Interlaken, Switzerland.
90 Claude Auguste Lamy (1820–1878) was a French chemist who discovered the element thallium in 1862, independent of William Crookes.
91 Jules Henri Debray (1827–1888) was a chemist who, at the time, was an instructor at the Lycée Charlemagne. He worked closely with Henri Étienne Sainte-Claire Deville at the École Normale Supérieure where he studied the properties of platinum metals, particularly the melting of platinum and its alloys. In 1860, the two scientists were the first to melt an appreciable quantity of iridium. In 1881, Debray succeeded Deville as professor of chemistry at the École Normale.
92 Henri Étienne Sainte-Claire Deville (1818–1881) was Professor for Chemistry at the École Normale. He worked initially in organic chemistry but had at the time turned to inorganic and thermal chemistry. In 1854, he succeeded in obtaining metallic aluminium and turned it from being a rare precious metal to material for industrial manufacturing. With Debray, Deville worked on the preparation of platinum to serve as a suitable metal for the standard metre, as established by the International Metric Commission which was seated in Paris at the time.
93 Auguste Arthur de la Rive (1801–1873) was a Swiss physicist. He was interested in the development of magnetic fields and the electric discharges in gases.
94 Jean-Baptiste Léopold Alfred Riche (1829–1908) was a French chemist and pharmacist, at the Ecole Supérieure de Pharmacie in Paris, who produced mustard gas in 1854.
95 Could not be identified.
96 The identity of Cousin Louis unfortunately remains unknown.
97 Carlo Matteucci (1811–1868) was an Italian physicist and neurophysiologist who pioneered the study of bioelectricity.
98 Edmond Becquerel (1820–1891) was part of a French scientific dynasty. He was the son of Antoine César Becquerel (1788–1878), a pioneer in the study of electric and luminescent phenomena, and the father of Henri Becquerel who discovered radioactivity. Edmond Becquerel continued his father’s work on luminescence, a topic that was of particular interest to Plücker who had just started his study of luminous gases. Edmond is also credited with the discovery of the photovoltaic effect. In addition, he studied magnetic and diamagnetic materials, which were the topic of the time.
99 This dislike may have been due to the fact that Becquerel had demonstrated, even before Tyndall, that Plücker’s idea about the nature of diamagnetic material was incorrect.
100 Edmond Frémy (1814–1894) was a French chemist who is best known today for Frémy’s salt, a strong oxidizing agent which he discovered in 1845. Frémy’s salt is a long-lived free radical that finds use as a standard in electron paramagnetic resonance spectroscopy.
101 Louis Isidore Duperrey (1786–1865) was a French naval officer and explorer.
102 Henri Victor Regnault (1810–1878) was a French chemist and physicist, best known for his careful measurements of the thermal properties of gases. Regnault played a key role in the emerging field of gas physics and thermodynamics and he is the only nineteenth century scientist to receive both the Rumford and the Copley Medal awarded by the Royal Society as well as the Matteucci Medal.
103 In August 1856, Regnault suffered from a severe fall in his laboratory, which threatened his life for more than a month and involved an especially dangerous twelve-day coma. Biographical notes state that he never fully recovered. Sébastien Poncet, Laurie Dahlberg, 'The legacy of Henri Victor Regnault in the Arts and Sciences', HAL-open science (2012), <https://hal.archives-ouvertes.fr/hal-00678894>.
104 Louis Joseph Lebrun (1809–1889) was a French Army officer of the Second Empire, serving in all of the military campaigns of Napoleon III. In the rank of colonel, Lebrun fought in the Crimean War and served as Chef d’état-major to General Mac Mahon in 1855 in Algeria. Promoted to general in 1858, Lebrun fought in the battles of Turbigon, Magenta, and Solferino in the Second Italian Independence War to which Plücker refers in his letter. Lebrun continued to serve Napoleon III until he was taken prisoner after the French imperial army’s defeat in the battle at Sedan in 1870 against the Prussian army.
105 Hans Heinrich Landolt (1831–1910) was a Swiss chemist who had studied in Berlin with Plücker’s friend Eilhard Mitscherlich and in Heidelberg with Robert Bunsen before receiving, in 1857, a faculty position in Bonn. There, he married Mira Schallenberg in 1859.
106 Lettreu could not be identified, possibly the name was misspelled by Plücker.
107 Julius Plücker, ‘On the Magnetic Induction of Crystals’, Philosophical Transactions of the Royal Society, 148 (1858), 543–87.
108 At that time, August Beer was already suffering from cancer and died only a few years later in 1863.
109 ‘Faraday3612’, in ϵpsilon: The Michael Faraday Collection, <https://epsilon.ac.uk/view/faraday/letters/Faraday3612> [accessed 17 April 2022].
110 ‘Report on the Annual Meeting of the Royal Society, June 5, 1862’, Proceedings of the Royal Society of London, 12 (1863), 133.
111 Miss Trevor must have been either a former English governess in the Plücker household or the wife of an English faculty acquaintance in Bonn. Her name is frequently mentioned in the letters.
112 Eugen Sell (1842–1896) had studied mathematics and physics in Bonn and served from 1860 to 1861 as Plücker’s assistant. He left to continue the study of chemistry in London with August Wilhelm von Hofmann at the Royal College of Chemistry. In fall of 1863, Sell returned to Bonn to receive his PhD.
113 The glassblower and instrument builder Heinrich Geißler was providing gas tubes designed by Plücker for himself as well as for other researchers in Germany, France, and the United Kingdom. The remark suggests that Plücker took Geißler with him to provide the latter with the opportunity for new connections to the British science community.
114 August Wilhelm von Hofmann (1818–1892) was a former student of Justus von Liebig and a leading expert in organic chemistry. After his PhD in 1841, he went to Bonn. In 1845 he participated in a chemistry demonstration attended by Queen Victoria on the occasion of her visit with Prince Albert, who had studied in Bonn. The queen was impressed and Hofmann was recruited to Britain, where he served as the first director of the newly founded Royal College of Chemistry in London. In 1864, Hofmann left England and moved back to Bonn but in 1865, he was appointed Professor of Chemistry at the University of Berlin where he stayed for the rest of his life.
115 Presumably the matter at hand is Hofmann’s return to Germany and a potential faculty position for him in Bonn.
116 William Ladd (1815–1885) operated a business from 1842 or 1843 until 1882, making and selling microscopes and other scientific instruments. He is especially well remembered for his microscope designs and microscope auxiliaries. During his time, Ladd was also known for his pneumatic apparatus and groundbreaking forays into electricity, resulting in the design of Ladd’s dynamo which was most likely an instrument of interest to Plücker. At the time of Plücker’s visit, Ladd’s shop was located at 11–12 Beak Street, near Regent Street in London.
117 Anton Schröter from Vienna was in London as part of the Great World Exposition of the Royal Society of Art in London 1862. There he exhibited his famous collection of rare crystals, which is now part of the gemstone collection of the British Museum.
118 Eleanor Percy née Grosvenor, Duchess of Northumberland (1820–1911) was the wife of Algernon Percy, 4th Duke of Northumberland (1792–1865) who served as the president of the Royal Institution.
119 Henry Bence Jones, FRS (1813–1873) was an English physician and chemist. He is mostly known for identifying the Bence Jones protein in 1847. This is a globulin protein found in blood and urine, suggestive of multiple myeloma or cancer. He was a fellow of the Royal Society of Physicians and a fellow of the Royal Society. From 1860, he held the post of secretary of the Royal Institution, as successor of the Reverend John Barlow.
120 The Reverend John Barlow (1798–1869) was an Anglican priest and close friend of Michael Faraday. Barlow served as secretary of the Royal Institution from 1843 to 1860. He was known as a socially well-connected person and was instrumental in persuading many of the elite of mid-Victorian London society, from Prince Albert to the Duchess of Northumberland, to join the Royal Institution. Bence Jones became his successor at the Royal Society.
121 Sir Roderick Impey Murchison, FRS (1792–1871) was a British geologist who established the Silurian, as a new geological system, and cofounded the Devonian system. Murchison served as director general for the Geological Survey of Great Britain. He also administrated the Geological Society, the Geographical Society, and the British Association for the Advancement of Science.
122 H. G. Schramm was a mechanic in Hamburg who, in 1861, patented a new rotary pump system in London and subsequently moved there. Plücker was looking for new vacuum systems to improve conditions and control gas pressure in the Geißler glass tubes.
123 Sir Henry Holland, 1st Baronet, FRS (1788–1873) was a British physician and travel writer. He had an extensive practice and was Physician in Ordinary to Queen Victoria. He was well travelled, published several travel books, and advised Charles Darwin on the publication of The Voyage of the Beagle.
124 Rosamunde Wilson (1838–1860) was Hofmann’s second of four wives, whom he married in 1856 but who died four years later.
125 William Allen Miller (1817–1870) was professor at Kings College London. In 1867, Miller received the Gold Medal of the Royal Astronomical Society jointly with William Huggins, for their spectroscopic study of the composition of stars.
126 W. Allen Miller, ‘On the Photographic Transparency of Various Bodies, and on the Photographic Effects of Metallic and other Spectra Obtained by Means of the Electric Spark’, Proceedings of the Royal Society of London, 12 (1862–1863), 159–66.
127 This was indeed the last lecture Faraday gave to the Royal Institutions. C.f. Raymond J. Seeger, ‘Michael Faraday and the Art of Lecturing’, Physics Today 21.8 (1968), 30–40.
128 Friedrich Moritz Baumert (1818–1865) was a student of Liebig and Bunsen. From 1853 to 1857 he was extraordinary professor of chemistry in Bonn, but he retired early for health reasons in 1857. On occasion, he would replace Plücker during his absence. Baumert died while travelling to Berlin in 1865.
129 In 1862, Plücker was instrumental in founding the Pharmaceutical Institute in Bonn. Prior to its founding, pharmaceutical students were given final exams in Berlin but with the formation of the new institute, the rights for giving exams were moved to the university. Plücker served as the first director of the newly founded institute. Cf. A. D. Dronke, Julius Plücker – Professor der Mathematik und Physik an der Rhein. Friedrich Wilhelms-Iniversität in Bonn (Bonn: Adolph Marcus, 1871), p. 22, 24–25.
130 Report of the Thirty-Third Meeting of the British Association for the Advancement of Science held at Newcastle-upon-Tyne in August and September 1863 (London, 1864).
131 The topic was ‘On Spectral Analysis’ and Plücker discussed his recent spectral observations of gas discharges with nitrogen and sulphur vapour. Report on the Thirty-Third Meeting of the British Association of Sciences, Notices and Abstracts (London, 1864), p. 15–16.
132 William Armstrong, 1st Baron Armstrong (1810–1900) was a benefactor and president of the British Association who gave the official opening speech at the 1863 meeting in Newcastle. Armstrong owned the Elswick manufacturing concern on Tyneside, which later became the Armstrong Whitworth company through mergers. He was also an eminent scientist, inventor, and philanthropist. He is regarded as the inventor of modern artillery.
133 Thomas J.F. Deacon was an export merchant in Newcastle on Tyne. He was the husband of Caroline Reid (1816–1890), the niece of Michael Faraday’s wife Sarah Bernard (1800–1879). After his death, many of Michael Faraday’s relics were bequeathed to the Royal Institution. Cf. ‘Notes’, Nature 65 (1902), 322.
134 Plücker presumably refers to Thomas William (1844–1872). Thomas was one of the sons of William Watson Pattinson (1814–1895) who was the nephew of Hugh Lee Pattinson (1796–1858), a Tyneside chemical manufacturer who in 1833 patented a process for desilvering lead. With the profits resulting from this invention, Hugh Lee established a chemical works in Felling, Gateshead, in which his son and nephew were partners. In 1866, the extensive chemical works on the south side of the Tyne employed 10,000 workers in the production of sulphuric acid, soda and chlorine.
135 Sir Robert John Kane (1809–1890) was an Irish chemist and educator in Dublin.
136 Alexander William Williamson (1824–1904), Professor of Chemistry at University College, London, President of the Chemical Society.
137 Thomas Andrews (1813–1885) was an Irish chemist and physicist who worked on phase transitions between gases and liquids. He was a longtime professor of chemistry at Queen’s University of Belfast and vice president of the chemistry section of the British Association.
138 John Hall Gladstone (1827–1902) was a British chemist and a student of Justus von Liebig. At the time, Gladstone was a council member of the Royal Society. Then, between 1874 and 1876, he served as President of the Physical Society and from 1877 to 1879 was President of the Chemical Society. In 1858, Gladstone furthered the use of the prism in the qualitative analysis of elements, an aspect that was close to Plücker’s interest.
139 This refers to the Altstädten relatives of his wife, who lived at der Neugasse 986.
140 Dianne Sachko Macleod, ‘Private and Public Patronage in Victorian Newcastle’, Journal of the Warburg ad Courtauld Instituts, 52 (1989), 188–288 (p. 197).
141 Mendelssohn & Co. was one of the leading private banks in nineteenth century Prussia, founded in 1795 by members of the famous Jewish family Mendelssohn.
142 As his return to Bonn grew near, Plücker seemed to be gradually recalling his numerous faculty duties as chair of Mathematics and Physics.
143 C. W. Zenger was Professor for Chemistry in Prag where he used spectroscopical tools to analyze arsenic components.
144 This refers to metempsychosis and magic lantern sessions organized by the flamboyant John Henry Pepper, director of the Polytechnic Institution at the time. The goal was to combine science and metempsychosis, as a new development, in an attempt to popularize modern science; Jeremy Brooker, ‘The Polytechnic Ghost’, Early Popular Visual Culture, 5, 2 (2007), 189–206.
145 Here Plücker refers to Hittorf’s request to get him sulphuric material for extracting arsenic material, on 19 August 1863 (NRC, vol 3, 50–58).
146 Antoine François Jean Claudet (1797–1867) was a French born photographer in London who produced daguerreotypes. (The daguerreotype is named after the inventor, Louis Jacques Mandé Daguerre. Each daguerreotype is a unique image on a silvered copper plate.) Claudet also invented other optical instrumentation to measure the intensity of light and the focal length of the camera. He had several studios at the Colosseum but in 1851, he moved his entire business to 107 Regent Street where he established what he called a ‘Temple to Photography’. It has been estimated that he made 1,800 pictures every year with subjects including famous scientists such as Michael Faraday and Charles Babbage. Claudet was elected a fellow of the Royal Society in 1853 and, in the same year, was appointed as ‘Photographer-in-ordinary’ to Queen Victoria.
147 Cf. Brian Bowers, ‘Sir Charles Wheatstone FRS 1802–1875’, History of Technology 29 (1975/2001), 45–54.
148 <https://www.npg.org.uk/collections/search/portrait/mw08491/Sir-Charles-Wheatstone-and-his-family> [viewed 1 June 2022].
149 In his letters to Plücker on 14 July and 19 August 1863, Hittorf doubted the existence of a new element that Plücker had predicted from his spectral analysis. Unfortunately, Hittorf could not separate it by chemical methods from the arsenic-containing material so as to unanimously confirm its existence.
150 Misdated as 16 September 1863.
151 James Glaisher (1809–1903) was an English meteorologist, aeronaut, and astronomer. Glaisher pioneered balloon journeys all over England, reaching for ever-higher altitudes in order to attain meteorological measurements. Just one year prior to this meeting, he reached a world-record altitude of 10,000 m. Glaisher was very much interested in photography, in order to record his observations, and was elected a member of The Photographic Society in 1854, serving as the society’s president for many years. He was photographed by Claudet at the same time as Plücker.
152 Small meal made without meat and thus permitted on a fasting day.
153 'Les Mondes – Revue Hebdomadaire des Sciences et Leurs Applications Aux Arts et À L’Industrie' was a popular weekly review of scientific developments and their applications in the arts and industry, published and edited by Abbé Moigno who did not hesitate to strongly formulate his personal opinions.
154 The Prussian thaler was the standard monetary coin in northern Germany until 1873 and had a fine silver content of 16.7 g.
155 Association of German Natural Scientists and Physicians, the German counterpart to the British Association for the Advancement of Science.
156 Julius Plücker, ,Auffassung des Raums vermöge der Geraden als Raumelement‘, in Amtlicher Bericht uber die neun und dreißigste Versammlung deutscher Naturforscher und Arzte in Gießen im September 1864, ed. by Wernher und Leuckart (Gießen, 1865) p. 67.
157 Rudolf Friedrich Alfred Clebsch (1833–1872) was a German mathematician who made important contributions to algebraic geometry and invariant theory. He attended the University of Königsberg where he studied mathematical physics and graduated in 1854 on a topic of a fluid dynamics. As a student, Clebsch participated in editing a collection of the mathematical works of Carl Jacobi, one of the supporters of Jakob Steiner and opponents of Plücker. Clebsch moved to Berlin where he continued work on topics of hydrodynamics and elasticity, which earned him a faculty position at the Polytechnicum in Karlsruhe. While there, he established a mathematical seminar. He gradually turned from his applied mathematics efforts to pure mathematics and moved to the University of Giessen in 1863, to pursue his new interests. In Giessen, Clebsch turned his mathematical interests to algebraic geometry, which explains the good relationship he developed with Plücker. Clebsch stayed only five years in Giessen, then accepting in 1868 a faculty position at the University of Göttingen. There Plücker’s last student Felix Klein took a postdoctoral appointment, working with Clebsch on non-Euklidian geometry. Alfred Clebsch died in 1872 at the young age of forty and several faculty positions later, Felix Klein became his successor as chair of mathematics in Göttingen.
158 Emil Plücker (1806–1871) is Julius Plücker’s youngest brother, who has returned to Germany after several failed emigration attempts to Texas. He eventually settled in Düsseldorf with his brother’s help. Cf. Michael Wiescher, ‘Rheinische Bürgersöhne in Texas’.
159 Aussee is a town in the Austrian state of Styria, located at the confluence of the three sources for the Traun River in the Ausseerland region. It is also a spa that offers medicinal brine baths and the Kneipp Cure therapy, which was invented by the German priest Sebastian Kneipp (1821–1897). This therapy was very fashionable in the nineteenth century, combining cold-water treatment, diets, and outdoor exercise to improve the blood and circulatory system.
160 NRC vol. 5, letters to his wife, no. 130.
161 William Spottiswoode (1825–1883) was an English mathematician, physicist, and publisher. He became a fellow of the Royal Society in 1853, treasurer in 1871, and president from 1878 to 1883. He was the first to make wide use of symmetrical determination notation, research in the physics on polarization and electrical discharge through rarefied gases.
162 Arthur Cayley (1821–1895) was a British mathematician and may be considered the inventor of the theory of matrices. He received an honorary doctorate from eight universities and was a Fellow of most European scientific societies, including the Royal Society in 1852. Cayley was probably the most prolific mathematician of his era and was deeply interested in Plücker’s new approach to the geometry of 3-space.
163 Report of the Thirty-Fifth Meeting of the British Association to the Advancement of Science, held in Birmingham 1865 (London, 1866), 4–5, 7.
164 Sir Edward Belcher (1799–1877) served in the British Navy between 1812 and 1871. Between 1825 and 1850, he took part in or commanded many surveys of the Pacific Ocean coasts and the Bering Strait, as well as the north and west coasts of Africa. He also undertook several journeys to China and Borneo. Belcher is most famous for commanding the unsuccessful Arctic expedition of 1853–1854, to rescue the explorer Sir John Franklin and his crew who were lost while in search of the Northwest Passage. Belcher described his Arctic venture in The Last of the Arctic Voyages (1855).
165 James David Forbes (1809–1868) was a Scottish physicist elected to the Royal Society of London in 1832. He was also one of the founders of the British Association. In 1830 he began to investigate radiant heat phenomena and in November 1834, Forbes discovered the polarization of radiant heat. He received the Rumford Medal, awarded by the Royal Society of London, in 1838 for his discoveries. His central interest was in geology although he continued to study heat conduction in solids and various types of soils as well as the effects of the atmosphere on solar radiation. From 1840 to 1851 he served as secretary of the Royal Society of Edinburgh. In 1853, Forbes wrote a peculiar letter to Plücker inquiring about the status of German science as well as the biographies of German scientists, primarily of Carl Friedrich Gauss (1777–1855) in Göttingen. In l860, after Forbes’ election as principal of the United College of St. Andrews, he resigned from his chair at Edinburgh. He held the position at St. Andrews until his death.
166 Humphrey Lloyd (1800–1881) was an Irish scientist. His first important original research together with William Rowan Hamilton was in optics, in particular in the theory of conical refraction. He remained active in the field of terrestrial magnetism throughout his life and succeeded in demonstrating the existence of electricity currents in the earth’s crust as well as calculating their effect on the daily variation in the magnetic field.
167 Thomas Archer Hirst (1830–1892), mathematician who worked on Chasles’ methods.
168 Unidentified.
169 John Scott Russell (1808–1892), CE, FRS.
170 Geheimrath Henri von Dechen (1800–1889), Professor in Bonn, nestor of the geologists in Prussia.
171 Prof. Ferdinand Römer (1818–1891), Privatdozent in Geology and Paleontology in Bonn and after 1855 Professor of Geology at the University of Breslau. He was one of the first explorers to investigate the geological features of Texas in 1845–1847 and may have been acquainted with Emil Plücker who served from 1845–1846 as a guide and a collector of natural specimens in Texas. Cf. Samuel Wood Geiser, ‘Men of Science in Texas, 1820-1880’, Field and Laboratory, 27.4, p. 174, 186–187 (1959) and Ferdinand Roemer, Texas – Mit besonderer Rücksicht auf deutsche Auswanderung und die physischen Verhältnissedes Landes nach eigener Beobachtung geschildert. (Bonn, 1849).
172 Georg Friedrich Wilhelm Rümker (1832–1900) was a German astronomer.
173 Julius Plücker, ‘On a New Method in Geometry’ in Report of the Thirty-Fifth Meeting of the British Association to the Advancement of Science, held in Birmingham 1865 (London, 1866), p. 7.
174 Sarah is presumably one of the English governesses or maids regularly employed by Plücker to help with his son Albert, but also to improve his own English language skills.
175 Angela Georgina Burdett-Coutts, 1st Baroness Burdett-Coutts (1814–1906) was a British philanthropist, daughter of Sir Francis Burdett, 5th Baronet and Sophia, formerly Coutts, daughter of banker Thomas Coutts. In 1837, Burdett-Coutts became one of the wealthiest women in England when she inherited her grandfather’s fortune of around £1.8 million (equivalent to £170,000,000 in 2020). She joined the surnames of her father and grandfather, by royal license, to become Burdett-Coutts. King Edward VII is reported to have described her as, ‘[a]fter my mother, the most remarkable woman in the kingdom’.
176 Cf. Brian Bowers, ‘Sir Charles Wheatstone FRS 1802–1875’, History of Technology 29 (1975/2001), 115-184.
177 CW to JP (16 February 1866) NRC, vol. 1B, Wheatstone item no. 52, series item no. 11 of 14C.
178 This is not a new idea. In 1847, Plücker had already communicated with Ludwig Immanuel Magnus about making wooden models to visualize mathematical descriptions of geometrical features. Cf. NRC, vol. 3A, item 8.
179 Indeed, British mathematicians, such as Cayley and others, took quick notice of this approach. In particular, Thomas Hirst, a former student of Jacob Steiner’s, requested some of these models. After his return to Bonn and some exchange of letters, Plücker sent a model in balsa wood to Hirst’ for display at the Paris world’s fair in 1867, but these were either lost or damaged. Cf. David E. Rowe, ‘Models from the 19th Century used for Visualizing Optical Phenomena and Line Geometry’, arXiv:1912.07138v1 [math.HO], 15 Dec 2019.
180 He refers to a coincidental meeting with his wife’s old friend or governess Miss Trevor, who had in 1862 recommended the hotel to Plücker.
181 Anthony John Mundella (1825–1897) was an English manufacturer and later a Liberal Party MP and Cabinet Minister who sat in the United Kingdom’s House of Commons from 1868 to 1897. He was a partner in the hosiery company Hine & Mundella in Nottingham.
182 August Beer, Einleitung in die Elektrostatik, die Lehre vom Magnetismus und die Elektrodynamik. Nach dem Tode des Verfassers herausgegeben von Julius Plücker (Braunschweig: EA., 1865).
183 Gustave Van der Mensbrugghe (1835–1911), Belgian physicist, editor of Belgium science journals such as Bulletins de l’Académie royale des sciences, des lettres et des beaux-arts de Belgique.
184 NRC, vol. 1B, Item 74.
185 The text of General Sabine’s address is given in a number of different publications, including the Proceedings of the Royal Society of London, XV (1867), 278–80.
186 Brigadier general Idelphonse Favé (1812–1894), expert in artillery weapons and professor of military art at the École. In 1866 he was appointed as president of the school. In 1870, Favé was in charge of the Paris defense against the German armies.
187 Cf. Michael Wiescher, ,Rheinische Bürgersöhne in Texas‘, 101–52.
188 Barbara Jaeckel and Wolfgang Paul, ,Die Entwicklung der Physik in Bonn 1818–1968‘ in Rheinische Friedrich-Wilhelms Universität zu Bonn. Bonner Gelehrte. Beiträge zur Geschichte der Wissenschaften in Bonn, Bd. 9 (Bonn, 1970), 92.
189 As quoted in Wilhelm Ernst and Julius Plücker – Eine zusammenfassende Darstellung seines Lebens und Wirkens als Mathematiker und Physiker auf Grund unveröffentlichter Briefe und Urkunden (Doctoral thesis, University of Bonn, 1933), 38.
190 Gabriel Lamé (1795–1870) contributed to the theory of partial differential equations by using curvilinear coordinates, while Plücker had a fundamental interest in coordinate systems and their transformation and application.
191 Joseph Louis François Bertrand (1822–1900) was a professor at the École Polytechnique and Collège de France. He was a member of the Paris Academy of Sciences and was its permanent secretary for twenty-six years. He worked in several mathematical fields of which differential geometry most likely offered the largest overlap with Plücker’s theories.
192 Joseph Serret (1819–1885) was a French mathematician and astronomer, especially known for differential geometry formulas, which were again of great interest to Plücker.
193 Charles Hermite (1822–1901) did research concerning number theory, quadratic forms, invariant theory, orthogonal polynomials, elliptic functions, and algebra. Many mathematical functions and techniques are named after him.
194 Pierre Ossian Bonnet (1819–1892) made important contributions to the differential geometry of surfaces, which was a topic of great interest to Plücker.
195 Ernest Jean Philippe Fauque de Jonquières (1820–1901) was a French naval officer who made several contributions in geometry. At the time of this meeting, Jonquières commanded a ship of the line (a type of naval warship) after having served from 1849 to 1850 on the staff of the Admiralty in Paris. During this time, Jonquières was associated with Michel Chasles who encouraged him in pursuing mathematics. During his subsequent time at sea, Jonquières continued his mathematical studies and won a place in the Grand Prix of the French Academy of Sciences in 1862. However, by 1867 the collaboration with Chasles had ended and their relationship had become hostile. This may explain his reception of Plücker and Plücker’s comment.
196 Florence Caroline Wheatstone (1850–1926) was the eldest daughter of Charles Wheatstone.
197 Luigi Cremona (1830–1903)
198 ‘The Cholera in Milan in 1867’, in The British and Foreign Medico-Chirurgical Review, 44.87 (1869), 173–75.
199 Letter from Heinrich von Mühler to Albert Plücker dated 8 March 1868, as quoted by Ernst and Plücker, p. 40.
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