Spreading the Gospel: A Popular Book on the Bohr Atom in its Historical Context

Summary

The emergence of quantum theory in the early decades of the twentieth century was accompanied by a wide range of popular science books, all of which presented in words, and a few in images, new scientific ideas about the structure of the atom. The work of physicists such as Ernest Rutherford and Niels Bohr, among others, was pivotal to the so-called planetary model of the atom, which, still today, is used in popular accounts and in science textbooks. In an attempt to add to our knowledge about the popular trajectory of the new atomic physics, this paper examines one book in particular, co-authored by Danish science writer Helge Holst and Dutch physicist and close collaborator of Niels Bohr, Hendrik A. Kramers. Translated from Danish into four European languages, the book not only explained contemporary ideas about the quantum atom, but also discussed unresolved problems. Moreover, the book was quite explicit in identifying the quantum atom with the atom as described by Bohr's theory. We argue that Kramers and Holst's book, along with other ‘atomic books’, was a useful tool for physicists and science popularisers in trying to understand the new quantum physics.

Notes

¹Michael Whitworth, ‘The Clothbound Universe: Popular Physics Books, 1919–39’, Publishing History, 40 (1996), 53–82; Peter J. Bowler, Science for All: The Popularization of Science in Early Twentieth-Century Britain (Chicago: University of Chicago Press, 2009).

²As for Einstein, he was keenly interested in popularising his theory of relativity, as shown, for example, by his early semipopular presentation Über die Spezielle und die allgemeine Relativitätstheorie (Braunschweig: Vieweg & Sohn, 1917), translated into English as Relativity: The Special and General Theory (New York: Hartsdale House, 1920). Although Einstein had spared no pains in his ‘endeavour to present the main ideas in the simplest and most intelligible form’, the book presumed ‘a standard of education corresponding to that of a university matriculation examination’ (preface, p. v). On Einstein as a popular science writer, see Elke Flatau, ‘Albert Einstein als wissenschaftlicher Autor’, Max Planck Institute for the History of Science, Preprint 293 (2005).

³Jonathan R. Topham et al., ‘Focus: Historizicing “Popular Science”’, Isis, 100 (2009), 310–368. For a historiographical discussion of popular science and its relation to ‘history of science proper’, see Roger Cooter and Stephen Pumfrey, ‘Separate Spheres and Public Places: Reflections on the History of Science Popularization and Science in Popular Culture’, History of Science, 32 (1994), 237–267, who deplore ‘the reluctance of historians of all kinds to commit themselves to inquiry into popular science’ (p. 246).

⁴Arne Schirrmacher, ‘Der lange Weg zum neuen Bild des Atoms: Zum Vermittlungssystem der Naturwissenschaften zwischen Jahrhundertwende und Weimarer Republik’, in Wissenschaft und Öffentlichkeit as Ressourcen füreinander: Studien zur Wissenschaftgeschichte im 20. Jahrhundert, edited by Sybilla Nikolow and Arne Schirrmacher (Frankfurt am Main: Campus Verlag, 2007), 39–73. Schirrmacher traces the connection between the popularisation of science and the presentation of world views to the nineteenth century, referring to Andreas Daum, Wissenschaftspopularisierung in 19. Jahrhundert: Bürgerliche Kultur, naturwissenschaftliche Bildung und die deutsche Öffentlichkeit (München: R. Oldenbourg Verlag, 1998).

⁵Sybilla Nikolow and Christina Wessely, ‘Öffentlichkeit als epistemologische und politische Ressource für die Genese umstrittener Wissenschaftkonceptze’, in Nikolow and Schirrmacher 2007 (note 4), 273–285. On the political uses of popular science, see also: Stephen Hilgartner, ‘The Dominant View of Popularisation: Conceptual Problems, Political Uses’, Social Studies of Science, 20 (1990), 519–539.

⁶The editions are: Helge Holst and H. A. Kramers, Bohrs Atomteori Almenfatteligt Fremstillet (Copenhagen: Gyldendal, 1922); H. A. Kramers and H. Holst, The Atom and the Bohr Theory of its Structure: An Elementary Presentation translated by Robert B. Lindsay and Rachel T. Lindsay, and with a foreword by Ernest Rutherford (London: Gyldendal, 1923); H. A. Kramers and H. Holst, Das Atom und die Bohrsche Theorie seines Baues. Gemeinverständlich dargestellt, translated by Fritz Arndt, a professor of chemistry at the University of Breslau (Berlin: Springer, 1925); H. A. Kramers and H. Holst, El Átomo y su Estructura Según la Teoria de N. Bohr, translated by Tomás R. Bachiller, a Spanish mathematician (Madrid: Revista de Occidente, 1925); H. A. Kramers and H. Holst, De Bouw der Atomen, translated by Henri C. Brinkman, a Dutch physicist who in 1932 completed his PhD in quantum physics at the University of Utrecht under the supervision of Kramers (Amsterdam: D. B. Centen, 1927). The Dutch edition was reprinted in 1930, and in 1949 it was published in an expanded version under the title De Bouw der Atomen en Moleculen.

⁷Historical comments on the Kramers-Holst book include Max Dresden, H. A. Kramers: Between Tradition and Revolution (Berlin: Springer, 1987), pp. 132–134, and Arne Schirrmacher, ‘Bohrsche Bahnen in Europa: Bilder und Modelle zur Vermittlung des Modernen Atom’, in Atombilder: Ikonographie des Atoms in Wissenchaft und Öffentlichkeit des 20. Jahrhunderts, edited by Charlotte Bigg and Jochen Hennig (Munich: Deutsches Museum, 2009), 73–82. Dresden finds it ‘not inappropriate to describe the book by Kramers and Holst as a truly missionary venture to spread the gospel according to Bohr’ (134). As we shall see, although it can indeed be described as missionary, the authors did not hide the provisional and incomplete nature of Bohr's theory.

⁸Helge Kragh, Niels Bohr and the Quantum Atom: The Bohr Model of Atomic Structure 1913–1925 (Oxford: Oxford University Press, 2012).

⁹Niels Bohr, ‘On the Constitution of Atoms and Molecules’, Philosophical Magazine, 26 (1913), 1–25, 476–502, 857–875. For historical analyses of Bohr's atomic theory, see Jagdish Mehra and Helmut Rechenberg, The Historical Development of Quantum Theory, vol. 1 (New York: Springer, 1982), Olivier Darrigol, From c-Numbers to q-Numbers: The Classical Analogy in the History of Quantum Theory (Berkeley: University of California Press, 1992, and Kragh 2012 (note 8). For a more accessible review and a full biography of Bohr, see Abraham Pais, Niels Bohr's Times, in Physics, Philosophy, and Polity (Oxford: Clarendon Press, 1991).

¹⁰James Jeans, ‘Discussion on Radiation’, Report, British Association for the Advancement of Science (London: J. Murray, 1914), 376–386 (379). This was the meeting at which Bohr's theory was first discussed in public and also the occasion for the first mention of it in the press. Reporting from the meeting, The Times of London briefly mentioned on 13 September Jeans's account of ‘Dr. Bohr's ingenious explanation of the hydrogen spectrum’.

¹¹On the British opposition, and the one of Nicholson in particular, see Helge Kragh, ‘Resisting the Bohr Atom: The Early British Opposition’, Physics in Perspective, 13 (2011), 4–35.

¹²Bowler 2009 (note 1); Schirrmacher 2007 (note 4); Hilgartner 1990 (note 5). The idea of a continuum of expository practices is found in: Michel Cloître and Terry Shinn, ‘Expository Practice: Social, Cognitive and Epistemological Linkages’, in Expository Science: Forms and Functions of Popularisation, Sociology of the Sciences. A Yearbook, vol. IX, edited by Terry Shinn and Richard Whitley (Dordrecht: Reidel, 1985), 31–60; Massimiano Bucchi, Science and the Media: Alternative Routes to Science Communication (London and new York: Routledge, 1998).

¹³Arthur S. Eve, ‘Modern Views on the Constitution of the Atom’, Science, 40 (1914), 115–121.

¹⁴G. Walter Stewart, ‘The Content and Structure of the Atom’, Science, 40 (1914), 661–663.

¹⁵On the representation of atomic theory in Germany from the turn of the century to the establishment of the Weimar republic in 1919, see Schirrmacher 2007 (note 4).

¹⁶Rudolf Seeliger, 'Moderne Anschauungen über die Entstehung der Spektrallinien und der Serienspektren’, Die Naturwissenschaften, 2 (1914), 285–290, 309–314 (313). Die Naturwissenschaften, founded in 1913 and published by the Springer Verlag, was until 1935 edited by the physicist Arnold Berliner. Associated with the Kaiser Wilhelm Gesellschaft, the magazine was subtitled Wochenschrift für die Fortschritte der Naturwissenschaften, der Medizin und der Technik (Weekly Publication for the Advances in the Natural Sciences, Medicine and Technology). It was in many ways the German equivalent to the British Nature and the US Science.

¹⁷Ernest Rutherford, ‘The Constitution of Matter and the Evolution of the Elements’, Popular Science Monthly, 87 (August 1915), 104–142 (139–140). The magazine was at the time about to change its profile. While the existing version was still of a rather scholarly nature, often with extensive articles written by recognised scientists, by the end of 1915 the journal changed to a format with numerous small and easy to read articles written by its reporters. At the same time the number of illustrations grew dramatically. The magazine became popular in a sense different from the older one, such as we discuss in our introduction.

¹⁸Schirrmacher 2007 (note 4), 50. On images and material models of atomic structures, see also Arne Schirrmacher, ‘Looking into (the) Matter: Scientific Artifacts and Atomistic Iconography’, in Illuminating Instruments, edited by Peter J. T. Morris and Klaus Staubermann (Washington: Smithsonian Institution Scholarly Press, 2009), 131–155.

¹⁹Schirrmacher 2007 (note 4), 62.

²⁰Leo Graetz, Die Atomtheorie in ihrer neuesten Entwickelung (Stuttgart: J. Engelhorns Nachf., 1918), 78. The book must have sold well, for in 1922 there was a fourth print run and the same year it appeared in a Russian translation. Graetz justified his publication by the general interest in atomic theory he had experienced ‘not only from physicists and chemists, but also from most scientifically educated laypersons’. Preface dated August 1918.

²¹This was a remnant of the ‘electromagnetic world view’ according to which the mass of a charged spherical particle was of electromagnetic origin, varying as the square of the charge over the radius. It follows that the radius of the electron must be nearly 2000 times as great as that of the proton. Bohr did not accept this interpretation and never spoke of the size of electrons.

²²Paul Kirchberger, Die Entwicklung der Atomtheorie, gemeinverständlich dargestellt (Karlsruhe: C. F. Müller, 1922), preface dated October 1921. A second revised edition appeared in 1929.

²³Arnold Sommerfeld, Atombau und Spektrallinien (Braunschweig: Vieweg & Sohn, 1919). Sommerfeld to Einstein, June 1918, in Arnold Sommerfeld. Wissenschaftlicher Briefwechsel, edited by Michael Eckert and Karl Märker, vol. 1 (Berlin: Verlag für Geschichte der Naturwissenschaften und der Technik, 2000), 597. While the first edition of Atombau had a length of 550 pages, the fourth edition had expanded to 862 pages.

²⁴The first book ever which referred to Bohr's atomic model was actually English: George W. C. Kaye, X rays: An Introduction to the Study of Röntgen Rays (London: Longmans, Green and Co., 1914), preface dated February 1914 (18).

²⁵Albert C. Crehore, The Atom (New York: Van Nostrand, 1920), preface 14 June 1919 (2). His exposition of the Bohr atom appeared on pp. 24–30. For Crehore and his views of atomic structure, see Kragh 2011 (note 11).

²⁶According to a Catalogue of British Scientific and Technical Books issued by the British Science Guild, in 1925 there were only 3 scientific books on quantum topics (a subgroup under ‘Spectra and Molecular Physics’) published in England, out of a total of 318 physics books. The corresponding figures for 1921 were 1 and 269. See Raykumari Williamson, The Making of Physicists (Bristol: Adam Hilger, 1987), 10.

²⁷Edward N. da C. Andrade, The Structure of the Atom (London: G. Bell and Sons, 1923); N. Robert Campbell, The Structure of the Atom (Cambridge: Cambridge University Press, 1923).

²⁸John W. N. Sullivan, Atoms and Electrons (London: Hodder and Stoughton, 1923), 121, reviewed in Nature, 113 (1924), 379–380. On Sullivan as a science writer, see Whitworth 1996 (note 1), who also mentions a few other English popular books dealing with atoms, including Oliver Lodge, Atoms and Rays: An Introduction to Modern Views on Atomic Structure and Radiation (New York: George H. Doran, 1924).

²⁹Bertrand Russell, The Autobiography of Bertrand Russell, vol. 2 (London: Allen and Unwin, 1968), 152.

³⁰Bertrand Russell, The ABC of Atoms (London: Kegan Paul, Trench, Trubner & Co., 1927), 63. The first edition from the summer of 1923 was sold at 4s 6d and printed in 3000 copies (Whitworth 1996, note 1). Russell also wrote a popular book on relativity theory, The ABC of Relativity (London: Kegan Paul, Trench, Trubner & Co., 1925), the first edition of which was printed in 2000 copies.

³¹Alfred N. Whitehead, Science and the Modern World (London: Macmillan, 1925), 114.

³²Helge Kragh, Peter C. Kjærgaard, Henry Nielsen and Kristian Hvidtfelt Nielsen, Science in Denmark: A Thousand-Year History (Aarhus: Aarhus University Press, 2008), 425.

³³John Heilbron, ‘The Earliest Missionaries of the Copenhagen Spirit’, Revue d'historie des sciences, 38 (1985), 195–230; Mara Beller, ‘Jocular Commemorations: The Copenhagen Spirit’, Osiris, 14 (1999), 252–273. On the role of charisma in the sciences, see: Charles Thorpe and Steven Shapin, ‘Who was J. Robert Oppenheimer? Charisma and Complex Organization’, Social Studies of Science, 30 (2000), 545–590.

³⁴This section is based on Finn Aaserud, ‘Niels Bohr (Physics 1922): “I Know how Little I have Deserved This …”’, in Neighboring Nobel: The History of Thirteen Danish Nobel Prizes, edited by Henry Nielsen and Keld Nielsen (Aarhus: Aarhus University Press, 2001), 272–312.

³⁵This section is based on Finn Aaserud, ‘Niels Bohr (Physics 1922): “I Know how Little I have Deserved This …”’, in Neighboring Nobel: The History of Thirteen Danish Nobel Prizes, edited by Henry Nielsen and Keld Nielsen (Aarhus: Aarhus University Press, 2001), 289.

³⁶N. Bohr, ‘Atom’, Encyclopaedia Britannica, 13th ed., Suppl., vol. 1 (1926), 262–267. Bohr made various attempts to present modern atomic physics to a general audience, but mostly in the post-1925 period. See Finn Aaserud, ed., Niels Bohr Collected Works, vol. 12 (Amsterdam: Elsevier, 2007).

³⁷N. Bohr, The Theory of Spectra and Atomic Constitution, translated by A. D. Udden (Cambridge: Cambridge University Press, 1922); Drei Aufsätze über Spektren und Atombau (Braunschweig: Vieweg & Sohn, 1922); Les spectres et la structure de l'atome: trois conférences, translated by A. Corvisy (Paris: J. Hermann & Cie., 1923). A second English and German edition, slightly revised and provided with a couple of appendices, came out in 1924.

³⁸Bohr 1922 (note 37, English edition), vi.

³⁹Ralph H. Fowler, ‘The Structure of the Atom’, Nature, 111 (1923), 523–525 (523).

⁴⁰The standard biography of Kramers is Dresden 1987 (note 7). The expression ‘disciple’ comes from Heilbron 1985 (note 33). For Bohr's appreciation of Kramers, see the memorial address in Nederlandsch Tijdschrift voor Natuurkunde, 18 (1952), 161–166, reproduced in Aaserud 2007 (note 36), 355–360. Remarkably, neither in this address nor at any other occasion did Bohr mention the Kramers-Holst book.

⁴¹Peter Robertson, The Early Years: The Niels Bohr Institute 1921–1930 (Copenhagen: Akademisk Forlag, 1979), 51, 95–97. Kramers to Bohr, 12 March 1917, in Niels Bohr Collected Works, vol. 3, edited by J. Rud Nielsen (Amsterdam: Elsevier, 1976), 654. Kramers quickly learned to speak and write Danish.

⁴²Hans M. Hansen, ‘Helge Holst’, Fysisk Tidsskrift, 43 (1945), 1–4 (in Danish).

⁴³On popular science in Denmark in the early twentieth century, see Kragh et al. 2008 (note 32), 357–383.

⁴⁴Holst to Bohr, four letters of 1919, in Archive for History of Quantum Physics (AHQP), Bohr Scientific Correspondence (film 3, section 4). See also Holst to Kramers, 5 July 1921, AHQP, Kramers Correspondence M/f no. 8a Section 6–025. The information about Holst and the theory of relativity is in part based on an unpublished Master Thesis (Aarhus University) from 1998 by Jonas Cilieborg.

⁴⁵The title was Bohrs Atomteori Almenfatteligt Fremstillet, meaning ‘Bohr's Atomic Theory, a Popular Exposition’. The Danish term ‘almenfattelig’ corresponds to the German ‘gemeinverständlich’ or literally ‘commonly intelligible’. In the Danish editions of 1922 and 1929 Holst appeared as a first author, while the order of the authors in the international editions was Kramers and Holst, presumably because Kramers was better known than Holst. The Danish editions of 1922 and 1929 were both printed in 2000 copies. This should be seen in relation to the population of the country, which in the 1920s was about 3.3 million, and may be compared with the number of copies (3000) of Russell's ABC of Atoms (note 30).

⁴⁶During his stay in Copenhagen, R. Bruce Lindsay worked under Bohr and Kramers, and the latter asked him to undertake the translation, much of which was actually done by Mrs. Lindsay. Apparently Kramers was himself involved in the translation. ‘I have used the last two weeks on … the English translation of my book with Holst’, he wrote to Bohr on 11 October 1923. See Rud Nielsen 1976 (note 41), 661.

⁴⁷Bohr did write a foreword to a later popular book on atomic physics coming from his institute and written by two of his collaborators, Christian Møller and Ebbe Rasmussen. This book, Atomer og Andre Småting [Atoms and Other Small Things] (Copenhagen: Hisrchsprung, 1938) followed the general structure of the Kramers-Holst book, but of course extended with aspects of quantum mechanics, nuclear physics and other post-1925 developments.

⁴⁸Kramers and Holst (note 6).

⁴⁹Kramers contemplated writing a Dutch translation as early as 1923, which appears from Holst to Kramers, 29 July 1923, AHQP, M/f No. 8a, Sect. 6–026.

⁵⁰This is what Walther Grotrian suggested in a review of 1925: W. Grotrian, Die Naturwissenschaften, 13 (1925), 952–953.

⁵¹The book contained colour plates of spectra produced by Bunsen and Kirchhoff. These plates of spectra, going back to the early 1860s, were reprinted in numerous texts on spectrum analysis. According to Klaus Hentschel, ‘it was the most frequently reprinted scientific illustration in the second half of the nineteenth century’. K. Hentschel, Mapping the Spectrum: Techniques of Visual Representation in Research and Teaching (Oxford: Oxford University Press, 2002), 48.

⁵³Kramers and Holst 1923 (note 6, English edition), 130–131. Other aspects of correspondence between quantum and classical theory mentioned in the book included the formal agreement between the Balmer-Ritz formula for the hydrogen spectrum and Bohr's quantisation postulate, the quantum theory-based derivation of the Rydberg constant, and the calculation of ‘more complicated electron motions than those which appears in the unperturbed hydrogen atom’ (141).

⁵²Kramers and Holst 1923 (note 6, English edition), 139.

⁵⁴Kramers and Holst 1923 (note 6, English edition), 141.

⁵⁵The acoustical analogy was due to Holst, who in a paper from the spring of 1922 introduced it to illustrate Bohr's idea of emission of radiation. H. Holst, ‘Om Niels Bohrs Værk’, Tilskueren (May 1922), 281–287.

⁵⁶Kramers and Holst 1923 (note 6), 120.

⁵⁷O. Klein, ‘Glimpses of Niels Bohr as Scientist and Thinker’, in Niels Bohr: His Life and Work as Seen by his Friends and Colleagues, edited by Stefan Rozental (Amsterdam: North-Holland, 1967), 74–93 (77).

⁵⁸Kramers and Holst 1923 (note 6), p. 132.

⁵⁹On these problems, see Helge Kragh, ‘Conceptual Objections to the Bohr Atomic Theory – Do Electrons Have a Free Will?’, European Physical Journal H, 36 (2011), 327–352.

⁶⁰Kramers and Holst 1923 (note 6), 133. According to Bohr, his atomic theory ‘does not attempt an “explanation” in the usual sense of this word, but only the establishment of a connexion between facts which in the present state of science are unexplained’. Bohr 1922 (note 37, English edition), v.

⁶³Kramers and Holst 1923 (note 6), 137–138.

⁶¹Kramers and Holst 1923 (note 6), 136.

⁶²Rutherford to Bohr, 20 March 1913, in Kragh 2012 (note 8), 70.

⁶⁴Kramers and Holst 1923 (note 6), 138.

⁶⁵Kramers and Holst 1923 (note 6), 142.

⁶⁶Much has been written about the BKS theory and its role in the final phase of the old quantum theory. See, for example, Dresden 1987 (note 7), 41–78, 159–215 and Sandro Petruccioli, Atoms, Metaphors and Paradoxes: Niels Bohr and the Construction of a New Physics (Cambridge: Cambridge University Press, 1993), 111–133. According to Dresden, the treatment of the BKS theory in the Kramers-Holst book ‘is without much doubt the most understandable exposition of the BKS ideas’ (195).

⁶⁷Kramers and Holst 1925 (note 6, German edition), 123–140. The idea that stellar energy is rooted in processes violating energy conservation was later taken up by Bohr, who advocated it from about 1929 to 1933. Well aware that the idea was speculative, Kramers did not expound it in any of his scientific publications. Indeed, one of the functions of popular works is that scientists have greater liberty in suggesting ideas of a speculative nature that would not be found acceptable in scientific articles.

⁶⁸Schirrmacher 2009 (note 18), 148. However, atomic iconography was not absent from the literature prior to 1918. See, for example, J. J. Thomson, Electricity and Matter (London: Constable & Co., 1904) and J. Newton Friend, The Theory of Valency (New York: Longmans, Green, and Co., 1909).

⁶⁹Schirrmacher 2009 (note 18) and Schirrmacher 2009 (note 7).

⁷⁰Kramers and Holst 1923 (note 6), 192.

⁷¹H. A. Kramers, ‘Das Korrespondenzprinzip und der Schalenbau des Atoms’, Naturwissenschaften, 11 (1923), 550–559. The Niels Bohr Archive in Copenhagen possesses a number of glass slides from the period with atomic pictures, but it is unknown whether these are the originals used by Bohr or reproductions from the Kramers-Holst book.

⁷²Schirrmacher 2009 (note 7), 74, suggests that the exclusion of images in the 1927 Dutch edition of Kramers and Holst's book was due to the development of quantum mechanics, which made such images obsolete.

⁷³Bohr admitted his mistake in an appendix to the second (1924) edition of Bohr 1922 (note 37, 138). Whereas the symmetric structure of the carbon atom was carefully described in the 1922 edition of the Kramers-Holst book, it was not mentioned in the later editions.

⁷⁴Holst to Kramers, 29 July 1923, AHQP, M/f No. 8a, Sect. 6–026. See also Holst to Kramers, 7 May 1925, AHQP, M/f No. 8a, Sect. 6–027, concerning the plates in the Spanish edition.

⁷⁵Kramers 1923 (note 71), 556. Reference to the plates and the Kramers-Holst book was also made by the Dutch physicist Dirk Coster in his contribution to the special issue. Characteristically, Coster worked at the time at Bohr's institute.

⁷⁶John C. McLennan, ‘On the Origin of Spectra’, Report, British Association of the Advancement of science (London: J. Murray, 1924), 25–58.

⁷⁷E. Andrade, ‘The Structure of the Atom’, in Chemistry in the Twentieth Century, edited by Edward F. Armstrong (London: Ernest Benn, 1924), 43–55 (53).

⁷⁸Lars Vegard, Stoffets Opbygning og Atomenes Indre (Kristiania: Olaf Norlis Forlag, 1924), who reproduced the pictures of H, He, Li, C, Ne and Na. On Vegard and his contributions to atomic theory, see H. Kragh, ‘Lars Vegard, Atomic Structure, and the Periodic System’, Bulletin for the History of Chemistry 37 (2012), 42–49.

⁷⁹Maria C. Boscá, ‘Some Notes on the Popularization of Quantum and Atomic Physics in Spain, 1914–1927’, in Communicating Science in the 20th Century, edited by Arne Schirrmacher (Max Planck Institute for the History of Science, Preprint 385, 2009), 61–74.

⁸⁰We have this information from an unpublished talk of 2007 by Arne Schirrmacher, see slide 22 of the power point presentation included in http://quantum-history.mpiwg-berlin.mpg.de/eLibrary/hq1_talks/old-qt/06_schirrmacher.

⁸¹H. Kamerlingh Onnes, ‘Rapports sur de nouvelles expériences avec les supraconducteurs’, Communications from the Physical Laboratory of the University of Leiden, 1924, Supplement 50a. For Kamerlingh Onnes's interest in atomic models, see Tilman Sauer, ‘Einstein and the Early Theory of Superconductivity’, Archive for History of Exact Sciences, 61 (2007), 159–211.

⁸²Pauli to Sommerfeld, 6 December 1924, in Kragh 2012 (note 8), 343.

⁸³Pauli to Bohr, 12 December 1924, in Kragh 2012 (note 8), 344.

⁸⁴Review essay, ‘Science for the People’, Nature, 113 (1924), 378–380, of Kramers and Holst 1923 (note 6) and Sullivan 1923 (note 28). The assessment that the book, although of a popular nature, was valuable to scientists because of its authoritative statements of Bohr's views, was repeated in a review by Frank Hoyt, a US physicist who knew Kramers from his stay in Copenhagen 1922–1924: Astrophysical Journal, 61 (1925), 453.

⁸⁵ Journal of the American Chemical Society, 46 (1924), 1318–1319.

⁸⁶Otto Halpern, Monatshefte für Mathematik, 35 (1925), 32–33. The other review, of the English edition, was R. D. Carmichael, Bulletin of the American Mathematical Society, 30 (1924), 374.

⁸⁷Grotrian 1925 (note 50). Dresden 1987 (note 7), 134, refers to a 1924 review by Max von Laue, also in Naturwissenschaften. This is puzzling, for no such review exists and yet Dresden quotes from it!

⁸⁸Harold C. Brown, ‘The Material World – Snark or Boojum?’ Journal of Philosophy, 22 (1925), 197–214 (203), based on an address delivered to the American Philosophical Association on 28 November 1924. The revolutionary passage that aroused the philosopher's attention appeared in Kramers and Holst 1923 (note 6), 133–134.

⁸⁹Whitworth 1996 (note 1); Bowler 2009 (note 1); Schirrmacher 2007 (note 4).

⁹⁰Hilgartner 1990 (note 5); D. Paul, ‘Spreading Chaos: The Role of Popularizations in the Diffusion of Scientific Ideas’, Written Communication, 21 (2004), 32–68.

⁹¹Bohr's speech at the Nobel banquet in 1922, cited from Robertson 1979 (note 41), 65.

⁹²Kramers and Holst 1923 (note 6), ix.

⁹³Nikolow and Wessely 2007 (note 5).