The Solar Element: A Reconsideration of Helium's Early History

Summary

Apart from hydrogen, helium is the most abundant chemical element in the universe, and yet it was only discovered on the Earth in 1895. Its early history is unique because it encompasses astronomy as well as chemistry, two sciences which the spectroscope brought into contact during the second half of the nineteenth century. In the modest form of a yellow spectral line known as D₃, ‘helium’ was sometimes supposed to exist in the Sun's atmosphere, an idea which is traditionally ascribed to J. Norman Lockyer. Did Lockyer discover helium as a solar element? How was the suggestion received by chemists, physicists and astronomers in the period until the spring of 1895, when William Ramsay serendipitously found the gas in uranium minerals? The hypothetical element helium was fairly well known, yet Ramsay's discovery owed little or nothing to Lockyer's solar element. Indeed, for a brief while it was thought that the two elements might be different. The complex story of how helium became established as both a solar and terrestrial element involves precise observations as well as airy speculations. It is a story that is unique among the discovery histories of the chemical elements.

Notes

¹E. Rutherford, Radioactive Transformations (London: Constable & Co., 1906), p. 179, and almost identically in Rutherford, ‘Helium and its Properties’, Nature, 128 (1931), 137–38 (p. 137).

²E. Rutherford, ‘The Amount of Emanation and Helium from Radium’, Nature, 68 (1903), 366–67. W. Ramsay and F. Soddy, ‘Gases Occluded by Radium Bromide’, Nature, 68 (1903), 246.

³E. Rutherford and T. Royds, ‘The Nature of the α Particle from Radioactive Substances’, Philosophical Magazine, 17 (1909), 281–86.

⁴According to the astronomer Edward Maunder, the first glimpse of the helium spectrum may have been caught by ‘[Luigi?] Magrini at Milan, during the total solar eclipse of 1842, July 8’. E.W. Maunder, Sir William Huggins and Spectroscopic Astronomy (London: T.C. & E.C. Jack, 1913), p. 73. I have not been able to confirm this claim.

⁵The change may be illustrated by Alfred Tuckerman's bibliography of spectroscopy, which in its original edition of 1888 included only a single paper in its section on helium. The supplement published in 1902 mentioned 48 papers in the category. A. Tuckerman, Index to the Literature of the Spectroscope (Washington, DC: Smithsonian Institution, 1888) and Index to the Literature of the Spectroscope 1887–1900 (Washington, DC: Smithsonian Institution, 1902).

⁶Augustin Brannigan, The Social Basis of Scientific Discoveries (Cambridge: Cambridge University Press, 1981); Simon Schaffer, ‘Scientific Discoveries and the End of Natural Philosophy’, Social Studies of Science, 16 (1986), 387–420; Timothy L. Alborn, ‘The “End of Natural Philosophy” Revisited: Varieties of Scientific Discovery’, Nuncius, 3 (1988), 227–52. A series of different perspectives on what characterizes a scientific discovery is presented in Thomas Nickles, ed., Scientific Discovery, Logic, and Rationality (Dordrecht: Reidel, 1981).

⁷On coronium, see section 5. For an argument that only entities that actually exist can be discovered, see Peter Achinstein, ‘Who Really Discovered the Electron?’ in Jed Z. Buchwald and Andrew Warwick, eds, Histories of the Electron: The Birth of Microphysics (Cambridge, Mass.: MIT Press, 2001), 403–24.

⁸There is no scholarly work on the overall history of helium. Historical surveys include Clifford W. Seibel, Helium: Child of the Sun (Lawrence: University Press of Kansas, 1968), which emphasizes the early helium gas industry in the United States, and A.M. Arkharov, ‘Helium: History of its Discovery, Technology of its Liquefaction, Areas of its Application’, Chemical and Petroleum Engineering, 31 (1995), 50–60, which focuses on liquefied helium and its applications. For a semi-historical survey of the role played by helium in the development of modern cosmology, see Roger J. Tayler, ‘Helium in the Universe’, Contemporary Physics, 36 (1995), 37–48.

⁹Quoted in Mary E. Weeks and Henry M. Leicester, Discovery of the Elements (Easton: Journal of Chemical Education, 1968), p. 762.

¹⁰Kostas Gavroglu and Yorgos Goudaroulis, eds, Through Measurement to Knowledge: The Selected Papers of Heike Kamerlingh Onnes 1835–1926 (Dordrecht: Kluwer, 1991).

¹¹The history of early spectroscopy is extensive. Klaus Hentschel, Mapping the Spectrum: Techniques of Visual Representation in Research and Teaching (Oxford: Oxford University Press, 2002) includes full references to both the primary and secondary literature.

¹²W. Huggins, ‘The New Astronomy: A Personal Retrospect’, The Nineteenth Century, 41 (1897), 907–29 (p. 911). For the changes the spectroscope brought about in the culture of astronomy, see Simon Schaffer, ‘Where Experiments End: Tabletop Trials in Victorian Astronomy’, in Jed Z. Buchwald, ed., Scientific Practice: Theories and Stories of Doing Physics (Chicago: University of Chicago Press, 1995), 257–99. For early astrospectroscopy, and Huggins’ role in it in particular, see also Barbara J. Becker, ‘Visionary Memories: William Huggins and the Origin of Astrophysics’, Journal for the History of Astronomy, 32 (2000), 43–62.

¹³On astrophysics and solar eclipse expeditions in the second half of the nineteenth century, see Alex Soojung-Kim Pang, Empire and the Sun: Victorian Solar Eclipse Expeditions (Stanford: Stanford University Press, 2002).

¹⁴On the medal and the parallel biographies of Janssen and Lockyer, see David Aubin and Charlotte Bigg, ‘Neither Genius nor Context Incarnate: Norman Lockyer, Jules Janssen and the Astrophysical Self’, in The History and Poetics of Scientific Biography, edited by Thomas Söderqvist (Aldershot: Ashgate, 2007), 51–70. Janssen as an organizer and collector of astronomical knowledge is described in David Aubin, ‘Orchestrating Observatory, Laboratory, and Field: Jules Janssen, the Spectroscope, and Travel’, Nuncius, 17 (2002), 615–33. The best account of Lockyer's life and career is A.J. Meadows, Science and Controversy: A Biography of Sir Norman Lockyer (London: Macmillan, 1972), reprinted by Macmillan in 2008 with a new bibliographical essay by Meadows. See also Thomazine Mary Lockyer and Winifred L. Lockyer, Life and Work of Sir Norman Lockyer (London: Macmillan, 1928) and John North, ‘Sir Norman Lockyer (1836–1920)’, in Some Nineteenth Century British Scientists, edited by Rom Harré (Oxford: Pergamon Press, 1969), 154–202.

¹⁵J.N. Lockyer, ‘Notice of an Observation of the Spectrum of a Solar Prominence’, Proceedings of the Royal Society of London, 17 (1868), 91–92, reprinted in Lockyer, Contributions to Solar Physics (London: Macmillan, 1874), p. 439. Lockyer's book of 1874 is a convenient source as it includes his major communications on solar spectroscopy from the years 1866 to 1873. Some of them are also reproduced in A.J. Meadows, Early Solar Physics (Oxford: Pergamon Press, 1970), which includes a valuable summary account of the early history of solar physics and chemistry.

¹⁶P. Angelo Secchi, ‘Observations Relatives à une Communication Récente de M. Lockyer sur la Constitution Solaire’, Comptes Rendus, 69 (1869), 315–20, and also in Lockyer 1874 (note 15), 502–06. Secchi and Lockyer were in 1869 involved in a dispute concerning the interpretation of certain spectral lines in the chromosphere, but it did not concern the nature or origin of the D₃ line.

¹⁷J. Janssen, ‘Indication de quelques-uns des Résultats Obténus à Guntoor, pendant l’Éclipse du Mois d'AoÛt Dernier’, Comptes Rendus, 67 (1868), 838–39, with English translation in Meadows 1970 (note 15), 117–18.

¹⁸J.N. Lockyer, ‘On Recent Discoveries in Solar Physics Made by Means of the Telescope’, Philosophical Magazine, 38 (1869), 132–58, reprinted with a different title (‘The First Results of the New Method’) in Lockyer 1874 (note 15), 209–39. On the helium lines as celestial hieroglyphics, an allusion to the deciphering of the Rosetta stone, see J.N. Lockyer, ‘The Story of Helium’, Nature, 53 (1896), 319–22, 342–46. Such allusions were common in the period. For example, William Crookes referred explicitly to the Rosetta stone in his interpretation of the spectra of the rare earth metals. These were ‘a series of autograph inscriptions from the molecular world, evidently of intense interest, but written in a strange and baffling tongue. . . . I required a Rosetta stone’. W. Crookes, ‘Address, President of Section on Chemical Science’, Report, British Association of the Advancement of Science (1886), 558–77 (pp. 569–70).

¹⁹J.N. Lockyer, ‘Spectroscopic Observations of the Sun, II’, Philosophical Transactions of the Royal Society, 159 (1869), 425–44, and ‘Spectroscopic Observations of the Sun, III’, Proceedings of the Royal Society of London, 17 (1869), 350–56. Quotations from Lockyer 1874 (note 15), p. 459 and p. 478. The symbols C, F and D refer to the place of the lines in the Fraunhofer absorption spectrum.

²⁰J.N. Lockyer, ‘Spectroscopic Observations of the Sun, III’ (note 19), and Lockyer 1874 (note 15), p. 486. The first part of the series on ‘Spectroscopic Observations of the Sun’ appeared in 1866, an account of the new metod of observing solar prominences. As a further indication of Lockyer's uncertainty with respect to the nature of the D₃ line, in a table of bright lines in the chromosphere he added in a footnote to the D₃ line the single word ‘Hydrogen’, italicized and followed by a question mark (ibid. p. 495).

²¹Letters of 7 April 1869 and 9 September 1872, quoted in Meadows 1972 (note 14), 59–60. See also Colin A. Russell, Edward Frankland. Chemistry, Controversy and Conspiracy in Victorian England (Cambridge: Cambridge University Press, 1996), p. 436. Frankland proposed to use exceedingly long hydrogen tubes to see if the mysterious line would be produced in this way, but apparently these tubes were never constructed. See Lockyer and Lockyer 1928 (note 14), p. 42.

²²Lockyer 1874 (note 15), 381–423 (p. 415). The so-called 1474 line was found by Charles A. Young in the spectrum of the Sun's corona. C.A. Young, ‘On a New Method of Observing Contacts at the Sun's Limb, and Other Spectroscopic Observations during the Recent Eclipse’, American Journal of Sciences and Arts, 48 (1869), 370–78, reprinted in Meadows 1970 (note 15), pp. 125–34. The designation '1474’ refers to Kirchhoff's scale, not the wavelength of the line. Its wavelength was found to be 5317 Å, later to be corrected to 5303 Å (1 Å = 0.1 nm).

²³J.N. Lockyer, The Chemistry of the Sun (London: Macmillan and Co., 1887). Charles H. Hastings, ‘Comparison of the Spectra of the Limb and of the Centre of the Sun’, Nature, 8 (1873), 77, where it is stated that ‘the chromosphere is too transparent to reverse . . . the helium lines’. Lockyer's Studies in Spectrum Analysis (London: C. Kegan Paul & Co., 1878) included a chapter on elements present in the Sun (236–51), but without mentioning helium.

²⁴Lockyer, ‘The Story of Helium’ (note 18), p. 321, and similarly in Lockyer, The Sun's Place in Nature (London: Macmillan, 1897), p. 32 and p. 34.

²⁶W.B. Carpenter, [Presidential Address], Report, British Association for the Advancement of Science (1872), lixx–lxxxiv (p. lxxiv).

²⁵W. Thomson, [Presidential Address], Report, British Asso ciation for the Advancement of Science (1871), lxxxiv–cv (p. xcix).

²⁷On the claims of spurious elements based on spectroscopy or other methods, see Frank A.J. L. James, ‘The Practical Problems of a “New” Experimental Science: Spectro-Chemistry and the Search for Hitherto Unknown Chemical Elements in Britain 1860–1869’, British Journal for the History of Science, 21 (1988), 181–94, and V. Karpenko, ‘The Discovery of Supposed New Elements: Two Centuries of Error’, Ambix, 27 (1980), 77–102. As an exception among historians of science, James states correctly that ‘neither Lockyer nor Frankland formally published on helium until the 1890s when it was found on earth’ (p. 193).

²⁸E. Spée, ‘Sur la Raie Dite de l'Hélium’, Bulletin de l'Academie Royale (de Belgique) des Sciences, des Lettres et des Belles Arts (3), 49 (1880), 379–96 (p. 394). In an article on solar prominences a few years later he repeated his disbelief in helium. Spée, ‘Les Protubérances Solaires’, Ciel et Terre, 6 (1885–86), 409–21, 436–50, 461–74 (p. 443). On Spée and his works in astrophysics, see Auguste Collard, ‘Un Astrophysicien Belge: Mgr. Eugène Spée (1843–1924)’, Ciel et Terre, 42 (1926), 66–72. Crookes 1886 (note 18, p. 562) referred to his ‘able memoir’ on helium.

³⁰H. Kayser, Lehrbuch der Spektralanalyse (Berlin: Springer, 1883), p. 179. This may have been the first time that helium was ascribed the chemical symbol He. On Palmieri and his discovery claim, see below.

²⁹H. Vogel, ‘Resultate Spektralanalytischer Beobachtungen’, Astronomische Nachrichten, 78 (1871), 241–52, with partial translation in Meadows 1970 (note 18), pp. 121–24.

³¹A.C. Young, Die Sonne (Leipzig: Brockhaus, 1883), p. 232, a German translation of the first edition of 1881. Young repeated the assigment of the name to Frankland in the third edition of 1895 (p. 344) which included an appendix on the new discovery of terrestrial helium: A.C. Young, The Sun (New York: Appleton and Company, 1895). The erroneous attribution of helium to Frankland can be found also in the more recent literature, e.g. in Aaron J. Ihde, The Development of Modern Chemistry (New York: Dover Publications, 1984), p. 373.

³²A.C. Young, ‘Spectroscopic Notes: A New Form of Spectroscope’, Nature, 3 (1870), 111–13 (p. 112).

³³G.D. Liveing and James Dewar, ‘Note on the Unknown Chromospheric Substance of Young’, Proceedings of the Royal Society of London, 28 (1879), 475–77.

³⁴P.A. Secchi, Le Soleil, 2 vols. (Paris: Gauthier-Villars, 1875), vol. 1, p. 412 and vol. 2, p. 86.

³⁵L. Palmieri, ‘Della Riga dell'Helium Apparsa in una Recente Sublimazione Vesuviana’, Rendiconto dell'Academia delle Scienze Fisiche e Matematiche (1), 20 (1881), 150–72. The discovery of the D₃ line was mentioned in Nature, 25 (1881), 185. On Palmieri's life and career in geophysics, astronomy and meteorology, see Lorenzo Casertano, ‘The Scientific Life of Luigi Palmieri, 100th Anniversary Commemoration’, Annali di Geofisica, 42 (1999), 581–85. Ramsay became aware of Palmieri's work, but probably only in the summer of 1895: W. Ramsay, J. Norman Collie and Morris Travers, ‘Helium, a Constituent of Certain Minerals’, Nature, 52 (1895), 306–8, 331–34 (p. 306). After Ramsay's discovery of terrestrial helium, Palmieri attempted to draw new attention to his work, arguing that he should be credited with a share of the discovery. See L. Palmieri, ‘A Proposito della Riga dell'Helium’, Rendiconto dell'Academia delle Scienze Fisiche e Matematiche (2), 7 (1895), 13–24.

³⁶John W. Draper, Science in America. Inaugural Address of Dr. John W. Draper, as President of the American Chemical Society (New York: John F. Trow & Son, 1876), p. 13.

³⁷Draper's rhetoric was strikingly similar to that of the strongly religious Maxwell, who at about the same time used astrospectroscopy as an argument for a divine creator. J.C. Maxwell, The Scientific Papers of James Clerk Maxwell, 2 vols, edited by W.D. Niven (New York: Dover Publications, 1965), vol. 2, p. 225.

³⁸Alfred Cornu, ‘Sur le Spectre de l’Étoile Nouvelles de la Constellation du Cygne’, Comptes Rendus, 83 (1876), 1172–74 (p. 1173).

³⁹R. Copeland, ‘Note on the Visible Spectrum of the Great Nebula in Orion’, Monthly Notices of the Royal Astronomical Society, 48 (1888), 360–62. James E. Keeler, ‘On the Spectra of the Orion Nebula and the Orion Stars’, Astronomy and Astro-Physics, 13 (1894), 476–93. On Keeler's work, see Donald E. Osterbrock, James E. Keeler: Pioneer American Astrophysicist (Cambridge: Cambridge University Press, 1984), p. 147 and pp. 213–15, and on the early history of so-called helium stars, Agnes M. Clerke, Problems in Astrophysics (London: Adam & Charles Black, 1903), pp. 229–36. Neither Copeland nor Keeler referred to helium as a chemical element.

⁴⁰J.N. Lockyer, ‘Researches on the Spectra of Meteorites. A Report to the Solar Physics Committee’, Proceedings of the Royal Society of London, 43 (1887–88), 117–56 (p. 139).

⁴¹J.N. Lockyer, ‘Comparison of the Spectra of Nebulae and Stars of Groups I and II with those of Comets and Aurorae’, Proceedings of the Royal Society of London, 47 (1889–90), 28–39 (pp. 30–31).

⁴³Crookes 1886 (note 18), pp. 562–63. For more details, see Robert K. DeKosky, ‘Spectroscopy and the Elements in the Late Nineteenth Century: The Work of Sir William Crookes’, British Journal for the History of Science, 6 (1973), 400–23. The reference to Mr. Clarke is to the American geochemist Frank W. Clarke, who in an article of 1873 advocated evolutionary chemical ideas based on a modified version of Prout's hypothesis. Frank W. Clarke, ‘Evolution and the Spectroscope’, Popular Science Monthly, 2 (1873), 320–26.

⁴²The literature on this tradition in chemical thinking is considerable. See, for example, W.F. Farrar, ‘Nineteenth-Century Speculations on the Complexity of the Chemical Elements’, British Journal for the History of Science, 2 (1965), 297–323, H. Kragh, ‘Julius Thomsen and 19th-Century Speculations on the Complexity of Atoms’, Annals of Science, 39 (1982), 37–60, and David M. Knight, The Transcendental Part of Chemistry (Folkestone, Kent: Dawson, 1978). On Lockyer's ideas of dissociation, see William H. Brock, ‘Lockyer and the Chemists: The First Dissociation Hypothesis’, Ambix, 16 (1969), 81–99, and Matteo Leone and Nadia Robotti, ‘Are the Elements Elementary? Nineteenth-Century Chemical and Spectroscopical Answers’, Physics in Perspective, 5 (2003), 360–83. The best source on Prout's hypothesis is William H. Brock, From Protyle to Proton: William Prout and the Nature of Matter 1785–1985 (Bristol: Adam Hilger, 1985). Many of the primary sources are included in David M. Knight, Classical Scientific Papers: Chemistry, 2 vols (London: Mills & Boon, 1968–70).

⁴⁴Crookes 1886 (note 18), p. 575.

⁴⁵J. Thomsen, Om Materiens Enhed (Copenhagen: University of Copenhagen, 1887), 32.

⁴⁶A.K. Grünwald, ‘On the Remarkable Relationship Between the Spectrum of Water-Vapour and the Line-Spectra of Hydrogen and Oxygen, and on the Chemical Structure of the Two Latter, and their Dissociation in the Sun's Atmosphere’, Philosophical Magazine, 24 (1887), 354–67 (p. 354). The paper also appeared in German, in the Astronomische Nachrichten, 117 (1887), 201–14, and received a detailed review in Science, 11 (1888), 224–25. See also the critical response in H. Kayser, ‘Grünwald's Mathematische Spektralanalyse’, Chemiker-Zeitung, 13 (1889–90), 1655, 1687–88 and 14 (1889–90), 510–11. Kayser found Grünwald's works to be ‘pure nonsense’. See Matthias Dörries and Klaus Hentschel, eds, Heinrich Kayser: Erinnerungen aus meinem Leben (Munich: Institut für Geschichte der Naturwissenschaften, 1996), 136.

⁴⁷A.K. Grünwald, ‘Spectralanalytischer Nachweis von Spuren eines Neuen, der Eilften Reihe der Mendelejeff'schen Tafel Angehörigen Elementes, welches Besonders im Tellur und Antimon, Ausserdem aber auch im Kupfer Vorkommt’, Monatshefte für Chemie, 10 (1889), 829–61. Brauner's discovery claim of austriacum appeared in Chemical News, 29 (1889), 295. For this spurious element, see also Karpenko 1980 (note 27).

⁴⁹D.I. Mendeleev, ‘The Periodic Law of the Chemical Elements’, Journal of the Chemical Society, 55 (1889), 634–56, reprinted in Mendeleev 1891 (note 48), vol. 2 (pp. 435–54). The address can also be found in William B. Jensen, ed., Mendeleev on the Periodic Law. Selected Writings, 1869–1905 (Mineola: Dover Publications, 2005), 162–88 (p. 172). There is little doubt that Mendeleev had Crookes’ address of 1886 in mind.

⁴⁸In his Principles of Chemistry, Mendeleev referred critically to Grünwald's research programme of establishing relations between the spectra of chemical compounds and those of their component elements. D.I. Mendeleev, The Principles of Chemistry, 2 vols. (London: Longmans, Green, and Co., 1891), vol. 2 (p. 565).

⁵⁰Mendeleev 1891 (note 48), vol. 1, p. 561.

⁵¹D.I. Mendeleev, An Attempt Towards a Chemical Conception of the Ether (London: Longmans, Green, and Co., 1904). See also H. Kragh, ‘The Aether in Late Nineteenth Century Chemistry’, Ambix, 36 (1989), 49–65, and Michael D. Gordin, A Well-Ordered Thing: Dmitrii Mendeleev and the Shadow of the Periodic Table (New York: Basic Books, 2004), pp. 209–25.

⁵²Young 1895 (note 31), p. 259. On coronium, see also J.V. Van Spronsen, The Periodic System of the Chemical Elements, the First One Hundred Years (Amsterdam: Elsevier, 1969), 227–29.

⁵³Clerke 1903 (note 39), 60–61. In 1898 Italian scientists thought to have identified coronium in volcanic gases. Raffaello Nasini, Fransisco Anderlini and Roberto Salvadori, ‘Solfatora Gases’, Nature, 58 (1898), 269.

⁵⁴As late as 1919 two American chemists claimed to have detected traces of coronium in helium gas: Hamilton P. Cady and Howard M. Elsey, ‘The Possible Presence of Coronium in Helium from Natural Gas’, Science, 50 (18 July, 1919), 71–72. The mystery of the coronium line was only solved in 1939 when Walter Grotrian and Bengt Edlén independently concluded that the line was due to thirteen-times ionized iron (Fe¹³⁺). See Karl Hufbauer, Exploring the Sun: Solar Science since Galileo (Baltimore, MD: Johns Hopkins University Press, 1991), pp. 112–14.

⁵⁵On Hillebrand, see Frank W. Clarke, ‘Biographical Memoir of William Francis Hillebrand, 1853–1925’, Biographical Memoirs of Members of the National Academy of Sciences, 12 (1925), 43–70.

⁵⁶W.F. Hillebrand, ‘Occurrence of Nitrogen in Uraninite and Composition of Uraninite in General’, American Journal of Science, 40 (1890), 384–94 (p. 393). A more detailed report appeared in W.F. Hillebrand, ‘Occurrence of Nitrogen in Uraninite; Composition of Uraninite in General’, US Geological Survey, Bulletin no. 78 (1890), 43–79.

⁵⁷On the discovery of terrestrial helium, see Lockyer 1896 (note 18), Weeks and Leicester 1968 (note 9), pp. 759–62, and in particular the richly documented account in Morris W. Travers, A Life of Sir William Ramsay (London: Edward Arnold, 1956), written by one of Ramsay's assistants and an active participant in the experimental work on the noble gases. See also William A. Tilden, Sir William Ramsay. Memorials of his Life and Work (London: Macmillan, 1918), 135–40, and M.W. Travers, The Discovery of the Rare Gases (London: Arnold, 1928).

⁵⁹Quoted in Travers 1956 (note 57), p. 145. John Shields, one of Ramsay's collaborators, and Vaughan Harley, a lecturer on pathological chemistry, assisted with the experiments on the new gas that took place in the laboratory in University College, London.

⁵⁸Quoted in Travers 1956 (note 57), pp. 137–38.

⁶⁰Clarke 1925 (note 55), p. 56.

⁶¹M. Berthelot, ‘Nouvelles Recherches de M. Ramsay sur l'Argon et sur l'Hélium’, Comptes Rendus, 120 (1895), 660–62 (p. 661), English translation in Chemical News, 71 (1895), 176. Hillebrand had found that there existed a definite relation between the uranium oxide and the nitrogen, which to Ramsay indicated that argon might be bound chemically in the mineral.

⁶²Clarke 1925 (note 55), p. 59.

⁶³Clarke 1925 (note 55), p. 60.

⁶⁴W. Ramsay, ‘Helium, a Gaseous Constituent of Certain Minerals, Part I’, Proceedings of the Royal Society of London, 58 (1895), 80–89 (p. 84). This paper was received on April 27. In a preliminary note, read on April 25, Ramsay identified the new gas with helium, but without referring to Lockyer. W. Ramsay, ‘On a Gas Showing the Spectrum of Helium, the Reputed Cause of D₃, one of the Lines in the Coronal Spectrum’, Proceedings of the Royal Society of London, 58 (1895), 65–67.

⁶⁵J.N. Lockyer, ‘On the New Gas Obtained from Uraninite’, Proceedings of the Royal Society of London, 58 (1895), 67–70.

⁶⁶W. Crookes, ‘Spectrum of the Gas from Cléveite’, Chemical News, 71 (1895), 151. Five months later he published a much more detailed spectrum, based on helium from a variety of uranium minerals, still with the D₃ line as a singlet. W. Crookes, ‘The Spectrum of Helium’, Nature, 52 (1895), 428–30.

⁶⁷H.A. Deslandres, ‘Comparaison entres les Spectres du Gaz Clèvéite et de l'Atmosphère Solaire’, Comptes Rendus, 120 (1895), 1112–14.

⁶⁸C. Runge, ‘Terrestrial Helium (?)’, Nature, 52 (1895), 128. C. Runge and F. Paschen, ‘On the Constituents of Cleveite Gas’, Philosophical Magazine, 40 (1895), 297–302, and their complete report, including a discussion of solar and stellar spectra, in C. Runge and F. Paschen, ‘On the Spectrum of Cleveite Gas’, Astrophysical Journal, 3 (1896), 4–28.

⁶⁹H. Kayser, ‘Note on Helium and Argon’, Chemical News, 71 (1895), 89.

⁷⁰G.E. Hale, ‘Preliminary Note on the D₃ Line in the Spectrum of the Chromosphere’ and W. Huggins, ‘On the Duplicity of the Solar Line D₃’, appearing as companion articles in Astronomische Nachrichten, 138 (1895), 227–30. Hale also communicated his result to Astrophysical Journal, 2 (1895), 165.

⁷¹Lockyer 1896 (note 18). See letter from Runge to Lockyer of 20 October 1895, quoted in Meadows 1972 (note 14), p. 198 and Lockyer 1896 (note 18), p. 346. As an alternative to ‘asterium’, Lockyer mentioned ‘orionium’ which Runge however found to be ‘rather monstrous philologically’. Still in 1900 Lockyer thought of helium and asterium as two separate elements. See J.N. Lockyer, Inorganic Evolution as Studied by Spectrum Analysis (London: Macmillan and Co., 1900), p. 95.

⁷²Young 1895 (note 31), p. 348.

⁷³August Hagenbach, ‘Ein Versuch, die Beiden Bestandtheile des Cleveitgases durch Diffusion zu Trennen’, Annalen der Physik und Chemie, 60 (1896), 124–33. The name ‘parhelium’ was suggested by G. Johnstone Stoney.

⁷⁴Janne R. Rydberg, ‘The New Elements of Cleveite Gas’, Astrophysical Journal, 4 (1896), 91–96.

⁷⁵W. Ramsay and J. Norman Collie, ‘Sur l'Homogénéité de l'Argon et de l'Hélium’, Comptes Rendus, 123 (1896), 214–16.

⁷⁶Clerke 1903 (note 39), p. 58.

⁷⁷P.T. Cleve, ‘Sur la Présence de l'Hélium dans la Cléveite’, Comptes Rendus, 120 (1895), 834, with English translation in Chemical News, 71 (1895), 212. Since 1874 professor of chemistry in Uppsala, Cleve (1840–1905) worked until about 1885 mostly in inorganic chemistry, specializing in the rare earths. He subsequently focused on organic chemistry and micro-organisms in the oceans. See Hans Euler and Astrid Euler, ‘Per Theodor Clève’, Berichte der deutschen chemischen Gesellschaft, 38 (1905), 4221–38. He is recognized as the discoverer of the elements holmium and thulium, which he obtained in 1879 in the form of oxides, and is sometimes also mentioned as an independent discoverer of helium. The mineral cleveite was first described in 1878 by the Finnish-Swedish mineralogist Adolf Erik Nordenskiöld (1832–1901), who named it after Cleve. N.A. Langlet (1868–1936) obtained his doctorate from Uppsala in 1896 and later worked at the Chalmers Technical University in Gothenburg, first as lecturer and from 1911 as professor of chemistry.

⁷⁸Thorpe passed the letter on to Lockyer, who published it in Nature of 18 April, as P.T. Clève, ‘Terrestrial Helium?’ Nature, 51 (1895), 586.

⁷⁹N.A. Langlet, ‘Om Förekomsten af Helium i Cleveit’, Öfversigt af Kongl. Vetenskaps-Akademiens Handlingar 1895, no. 4 (1895), 207–08, 211–13 (p. 212).

⁸⁰P.T. Clève, ‘Sur la Densité de l'Hélium’, Comptes Rendus, 120 (1895), 1212. More details were given in N.A. Langlet, ‘Über das Atomgewicht des Heliums’, Zeitschrift für allgemeine Chemie, 10 (1895), 289–92, where the Swedish chemist concluded that the density was close to 2.0 (compared with hydrogen gas) and the atomic weight 4.0. English version in Chemical News, 72 (1895), 259.

⁸¹N.A. Langlet, ‘Om Helium’, Svensk Kemisk Tidskrift, 7 (1895), 161–64.

⁸²William Sedgwick, Force as an Entity, with Stream, Pool and Wave Form (London: Low, Marston, Searle & Rivington,1890), 60–69. Sedgwick, ‘The Existence of an Element without Valency of the Atomic Weight of “Argon” Anticipated Before the Discovery of “Argon” by Lord Rayleigh and Prof. Ramsay’, Chemical News, 70 (1895), 139–40. On the predictions of the noble gases, see Van Spronsen 1969 (note 52), pp. 248–51 and Carmen J. Giunta, ‘Argon and the Periodic System: The Piece that Would Not Fit’, Foundations of Chemistry, 3 (2001), 105–28 (p. 120).

⁸³C.J. Reed, ‘A Prediction of the Discovery of Argon’, Chemical News, 71 (1895), 213–15. Reed maintained that he had ‘no desire to claim post-mortem prediction of argon’ (p. 215), and he elaborated his arguments in Reed, ‘Reasons for Predicting the Existence of Argon’, Journal of the Franklin Institute, 140 (1895), 68–76, with abstract in Nature, 52 (1895), 278. R.M. Deelev, ‘Helium and Argon: Their Places Among the Elements’, Chemical News, 72 (1895), 297–98.

⁸⁴P.E. Lecoq Boisbaudran, ‘Remarques sur les Poids Atomique’, Comptes Rendus, 120 (1895), 213–15, and ‘Classification des Élements Chimique’, Comptes Rendus, 120 (1895), 1097–1103, with English translation in Chemical News, 71 (1895), 271–73.

⁸⁵J. Thomsen, ‘Über die Mutmassliche Gruppe Inaktiver Elemente’, Zeitschrift für anorganische Chemie, 8 (1895), 283–88, translated in Chemical News, 77 (1895), 120–21. See also Kragh 1982 (note 42).

⁸⁶B. Brauner, ‘Note on Gases of the Helium and Argon Type’, Chemical News, 7 1 (1895, 271, and ‘Argon, Helium, and Prout's Hypothesis’, Chemical News, 74 (1896), 223–24 (p. 223).

⁸⁷Brauner 1895 (note 86). Cp. also Travers 1956 (note 57), p. 140: ‘Professor Brauner of Prague always claimed to have been the first to see the spectrum of the new gas, and doubtless the claim was a true one’. Cerite is a non-radioactive mineral consisting of cerium, iron, silicium and oxygen. It was later confirmed that cerite contains small amounts of helium. R.J. Strutt, ‘Helium and Radio-Activity in Rare and Common Minerals’, Proceedings of the Royal Society of London, A 80 (1908), 572–94.

⁸⁸E.g. J. Thomsen, ‘Über die Abtrennung von Helium aus einer Natürlichen Verbindung unter Licht- und Wärmeentwicklung’, Zeitschrift für physikalische Chemie, 25 (1898), 112–14, and W. Ternent Cooke, ‘Experiments on the Chemical Behaviour of Argon and Helium’, Proceedings of the Royal Society of London, A 77 (1906), 148–55.

⁸⁹H. Wilde, ‘On Helium and its Place in the Natural Classification of Elementary Substances’, Philosophical Magazine, 40 (1895), 466–72 (p. 471). On the question of argon, helium and the periodic system, see Richard F. Hirsh, ‘A Conflict of Principles: The Discovery of Argon and the Debate over its Existence’, Ambix, 28 (1981), 121–30, Giunta 2001 (note 82) and John H. Wolfenden, ‘The Noble Gases and the Periodic Table: Telling it Like it Was’, Journal of Chemical Education, 46 (1969), 569–76.

⁹⁰On the discovery of hafnium and its relation to Niels Bohr's quantum theory of atoms, see Helge Kragh and Peter Robertson, ‘On the Discovery of Element 72’, Journal of Chemical Education, 56 (1979), 456–59, and Eric R. Scerri, ‘Prediction of the Nature of Hafnium from Chemistry, Bohr's Theory and Quantum Theory’, Annals of Science, 51 (1994), 137–50.

⁹¹According to Meadows 1972 (note 14), Ramsay recalled having heard Lockyer describe helium in a lecture many years before 1895 (p. 196).

⁹²E. Rancke Madsen, ‘The Discovery of an Element’, Centaurus, 19 (1976), 299–313. Of course, none of these requirements are unproblematic. The first requirement is only relevant for periods in which the notion of an element was defined in more or less the way we know today, that is, largely restricted to post-Lavoisier chemistry.

⁹³ Encyclopædia Britannica Online, entry on helium (http://search.eb.com/eb/article-9001713). Lockyer is not mentioned as a discoverer, but Ramsay is recognized as having discovered the element on Earth.

⁹⁴R. Meldola, ‘The State of Chemical Science in 1851’, Report, British Association of the Advancement of Science 1895, 639–55. Meldola (1849–1915) was a former assistant of Frankland and Lockyer. Travers (note 57) called Lockyer the ‘godfather’ of helium, an apt characterization (p. 149).

⁹⁵See R.C. Olby, ‘Rediscovery as an Historical Concept’, in R.P. W. Wisser et al., eds, New Trends in the History of Science (Amsterdam: Rodopi, 1989).

⁹⁶As recounted by Lord Rayleigh at the Ipswich meeting of the British Association. See Chemical News, 72 (1895), 223.

⁹⁷Weeks and Leicester (note 9), p. 761, and similarly in Ihde (note 31), p. 373 and A.A. Matyshev, ‘”Prout's Law” and the Discovery of Argon’, Physics-Uspekhi, 48 (2005), 1265–87 (p. 1265).

⁹⁸Robert K. Merton, ‘The Matthew Effect in Science’, in Merton, The Sociology of Science: Theoretical and Empirical Investigations (Chicago: University of Chicago Press, 1973), 439–59. Regrettably, in an earlier paper I made the error of crediting Cleve as an independent discoverer of helium: H. Kragh, ‘Cosmic Radioactivity and the Age of the Universe, 1900–1930’, Journal for the History of Astronomy, 38 (2007), 393–412 (p. 397).

⁹⁹W. Ramsay, ‘The Rare Gases of the Atmosphere’, in Tore Frängsmyr and Sture Forsén, eds, Nobel Lectures. Chemistry, 1901–1921 (Singapore: World Scientific, 1999), 68–77. Online in http://www.nobel.se. Similarly in Ramsay, The Gases of the Atmosphere: The History of their Discovery (London: Macmillan, 1905), 236.

¹⁰⁰When Ramsay's discovery was reported in the journal of the Swedish Chemical Society, the work of Langlet was briefly mentioned, but only in a footnote and not as an independent discovery. Svensk Kemisk Tidskrift, 7 (1895), 92.