Teach and Travel: Leiden Observatory and the Renaissance of Dutch Astronomy in the Interwar Years

Visser R. P. W. , “Het ‘Nederlandsch Natuur- en Geneeskundig Congres’ over de relatie natuurwetenschap en samenleving 1887–1900”, in Kloek J. J. Mijnhardt W. W. (eds), Balans en perspectief van de Nederlandse cultuurgeschiedenis: De productie, distributie en consumptie van cultuur (Amsterdam, 1991), 37–48; van Berkel K. , “Natuurwetenschap en cultureel nationalisme in negentiende-eeuws Nederland”, in idem, Citaten uit het boek der natuur: Opstellen over de Nederlandse wetenschapsgeschiedenis (Amsterdam, 1998), 221–39; Willink B. , De tweede gouden eeuw: Nederland en de Nobelprijzen voor natuurwetenschappen 1870–1940 (Amsterdam, 1998).

On Kapteyn, see van der Kruit P. C. van Berkel K. (eds), The legacy of J. C. Kapteyn: Studies on Kapteyn and the development of modern astronomy (Dordrecht, 2000); Blaauw A. , Sterrenkijken bekeken: Sterrenkunde aan de Groningse universiteit vanaf 1614 (Groningen, 1983); Hertzsprung-Kapteyn H. , J. C. Kapteyn, zijn leven en werken (Groningen, 1928; an English translation by Robert E. Paul was published in 1993).

On Leiden Observatory in this period, see van Herk G. Kleibrink H. Bijleveld W. , De Leidse Sterrewacht: Vier eeuwen wacht bij dag en nacht (Zwolle, 1983); Baneke D. , “‘Als bij toverslag’: De reorganisatie en nieuwe bloei van de Leidse Sterrewacht, 1918–1924”, Bijdragen en mededelingen betreffende de geschiedenis der Nederlanden, cxx (2005), 2005–25. See also Röhle S. , “Willem de Sitter in Leiden: Ein Kapitel in der Rezeptionsgeschichte der Relativitätstheorien”, dissertation, Mainz, 2007, esp. chap. 6.

On the history of Leiden Observatory see Kaiser F. , “Geschichte und Beschreibung der Sternwarte in Leiden”, Annalen der Sternwarte in Leiden, i (1868), pp. i–lxxxvi; de Sitter W. , Short history of the observatory of the university at Leiden 1633–1933 (Haarlem, 1933); Van Herk , De Leidse sterrewacht (ref. 3).

van de Sande Bakhuyzen H. G. , annual report of Leiden Observatory, 1888.

Idem, 1898.

Pannekoek A. , Herinneringen (Amsterdam, 1982). This book contains not one but two autobiographies: One concerning his political life (Herinneringen aan de arbeidsbeweging, with an introduction by B. A. Sijes) and one on his astronomical life (Sterrekundige herinneringen, with an introduction by E. P. A. van den Heuvel). Pannekoek always tried to keep the two spheres separated.

On De Sitter, see Röhle , Willem de Sitter in Leiden (ref. 3); Guichelaar J. , Willem de Sitter: Een alternatief voor Einsteins heelalmodel (Amsterdam, 2009). See also the poetic but unfortunately not very detailed biography by his wife: de Sitter-Suermondt E. , Willem de Sitter, een menschenleven (Haarlem, 1948), 37.

de Sitter W. , “On Einstein's theory of gravitation, and its astronomical consequences”, Monthly notices of the Royal Astronomical Society , First Paper: lxxvi, suppl. (1916), 699–728; Second Paper: Lxxvii/2 (1916), 155–84; Third Paper: Lxxviii/1 (1917), 3–28.

De Sitter to Gill, 12 August 1911, Archives of the Royal Geographical Society, DOG 159. See also a portrait of De Sitter as a 24-year-old student by his friend Johan Huizinga, on which he is labelled ‘wiskonstenaar’, mathematician (De Sitter family collection).

De Sitter , Verslag omtrent den staat van den Sterrewacht te Leiden en de aldaar volbrachte waarnemingen in April 1918. A draft of this report can be found in WdS 224.1.

De Sitter , Verslag (ref. 11), 4.

In a first letter to Kapteyn, De Sitter mentioned Ejnar Hertzsprung, Anton Pannekoek and Frits Zernike as other possible candidates. These and other details can be found in a diary De Sitter kept during this period: WdS 223.

According to Schlesinger, De Sitter had got an overdose of aether during an operation in 1914. Guichelaar , Willem de Sitter (ref. 8), 50–1. Before he took this decision, De Sitter had a long conversation with his physician.

De Sitter to the Board of Trustees of Leiden University, 19 April 1918, draft in WdS 224.1.

Most of the related documents can be found in WdS 224. See also De Sitter's correspondence with Kapteyn (WdS 30), Pannekoek (WdS 45) and Hertzsprung (WdS 23 and AH C46) (all in Dutch). A detailed reconstruction of the complications surrounding the appointments based on these sources can be found in Baneke D. , “‘Hij kan toch moeilijk de sterren in de war schoppen’: De afwijzing van Pannekoek als adjunct-directeur van de Leidse Sterrewacht in 1919”, Gewina, xxvii (2004), 1–13.

Hertzsprung to Kapteyn, 17 March 1918; copy in WdS 224.1.

Hertzsprung to De Sitter, 1 May 1918, WdS 224.1.

De Sitter to Hertzsprung, 1 November 1918, AH, C46/10.

Hertzsprung to De Sitter, 3 December 1920, AH, C46/9.

Pannekoek to De Sitter, 15 April 1919, WdS 45.1.

Pannekoek to De Sitter, 29 March 1918, WdS 45.1.

For example Haagse Post, 22 February 1919 and Provinciale Groninger Courant, 2 May 1919. In April 1919, Trustee J. E. Boddaert quoted another article, without mentioning its source. Boddaert to De Sitter, 16 April 1919, WdS 224.2. This folder also contains newspaper clippings of the other articles.

Baneke , “Hij kan toch moeilijk” (ref. 16).

Handelingen van de Tweede Kamer der Staten Generaal , 1919–1920, pp. 489, 495, 497–500, 524–6; and Handelingen van de Eerste Kamer der Staten Generaal, 1919–1920, pp. 414, 419–21, and idem, Bijlagen, 225, 250. This was after several newspapers revived the issue in September 1919, for example Nieuws van de Dag, 9 September 1919 (clipping in WdS 224.2).

Hertzsprung to De Sitter, 1 April 1920, WdS 224.2; Kapteyn to De Sitter, 13 June 1920, WdS 30. Hertzsprung wrote that the idea of asking Kapteyn had occurred to him on 31 March at 7:03 pm. His wife, Kapteyn's daughter Henrietta, claims the idea was hers. Hertzsprung-Kapteyn, J. C. Kapteyn (ref. 2), 157.

Kapteyn to De Sitter , 31 June 1920, WdS 1920.

Knegtmans P. J. , Een kwetsbaar centrum voor de geest: De Universiteit van Amsterdam tussen 1935 en 1950 (Amsterdam, 1998), 29. Among the other scientists to benefit from this were the mathematician Gerrit Mannoury and the historian Jan Romein.

Pannekoek , Herinneringen (ref. 7), 212.

Hertzsprung to Pannekoek, undated draft in AH, C46/10. I am not entirely sure that this letter was actually sent.

Kapteyn to De Sitter, 4 September 1918, and notes by De Sitter in the margins of a letter from Trustee N. C. de Gijselaar, 13 September 1918, WdS 224.2.

Handelingen van de Tweede Kamer der Staten Generaal , 1922–1923, Bijlagen 263.

Kapteyn to J. Oppenheim, 15 March 1918. Leiden University Library, Archive of the Board of Trustees, 1840.

De Sitter , Verslag (ref. 11), and Nota betreffende de formatie van het personeel der Sterrewacht, WdS 234.

de Sitter W. , Toespraak bij de inwijding van de gereorganiseerde Sterrewacht te Leiden (Haarlem, 1924), 8.

De Sitter—Dysen correspondence, WdS 12.

Schaffer S. , “Astronomers mark time: Discipline and the personal equation”, Science in context, ii (1988), 115–45; Smith R. W. , “A national observatory transformed: Greenwich in the nineteenth century”, Journal for the history of astronomy, xxii (1991), 1991–20; De Sitter , Verslag (ref. 11) and Nota (ref. 34).

De Sitter , Nota (ref. 34).

He said so in the speech at the reopening of the Observatory in 1924: De Sitter, Toespraak (ref. 35), 18.

Kapteyn to Newcomb, 22 October 1902, Groningen University archives, archive of the Kapteyn Institute EB91; cf. Kapteyn J. C. , “Het Sterrekundig Laboratorium”, Academia Groningana 1614–1914 (Groningen, 1914), 550–2.

According to an extended version of this story, the Socialist leader F. Domela Nieuwenhuis worked on the CPD while serving his time for insulting the king. Krul suggests that the myth was probably started by a remark from Eddington. Krul W. E. , “Kapteyn and Groningen: A portrait”, The legacy of J. C. Kapteyn (ref. 2), 53–78, p. 72.

De Sitter to Hertzsprung, 29 September 1920, WdS 23.9; Hertzsprung to De Sitter, 8 March 1921, AH, C46/9.

Kapteyn to J. Oppenheim, 15 March 1918. Leiden University library, archive of the Board of Trustees, inv. no. 1840; De Sitter, Verslag (ref. 11).

Correspondence between Weeder and Lorentz in WdS 225.

Obituary of Zwiers H. J. , Hemel en Dampkring, xxii (1924), 37–8.

Sullivan W. T. , “Kapteyn's influence on the style and content of twentieth century Dutch astronomy”, The legacy of J. C. Kapteyn (ref. 2), 229–63, and the article by T. D. Kinman in the same volume.

Katgert-Merkelijn J. K. , “The Kenya expeditions of Leiden Observatory”, Journal for the history of astronomy, xxii (1991), 267–96, and correspondence in WdS 49.

Katgert-Merkelijn , “The Kenya expeditions” (ref. 47).

He was in Johannesburg 1923–25 and in Harvard 1926–27.

van Berkel K. , “Growing astronomers for export: Dutch astronomers in the United States before World War II”, The legacy of J. C. Kapteyn (ref. 2), 151–74, p. 171.

De Sitter-Suermondt , Willem de Sitter (ref. 8), 37.

Guichelaar , Willem de Sitter (ref. 8), 125–6. De Sitter kept a diary during this journey, see WdS 205.

De Sitter to Kapteyn, 26 September 1920, AH, C46/10.

De Sitter , Toespraak (ref. 35), 18.

van Delft D. , Freezing physics: Heike Kamerlingh Onnes and the quest for cold, transl. by Jackson B. (Amsterdam, 2007), 319–36.

Adriaan Blaauw, interview with the author. See also the De Sitter—Hertzsprung correspondence, which was always polite and respectful but never warm or personal. Possibly, their relation was further pressured by the fact that Hertzsprung had fallen out with the Kapteyn family after his divorce from Henrietta in 1923. De Sitter was very close to the Kapteyn family. None of this is mentioned in Herrmann D. B. , Ejnar Hertzsprung: Pionier der Sternforschung (Berlin, 1994), or De Sitter-Suermondt, Willem de Sitter (ref. 8).

Pannekoek , Herinneringen (ref. 7), 247.

Katgert-Merkelijn J. K. , “De opvolging van W. de Sitter”, Leids jaarboekje, 1997, 128–43.

Hertzsprung to De Sitter, 28 January 1931, WdS 23.7. Hertzsprung received the Gold Medal in 1929 and the Bruce Medal in 1937; De Sitter received both prizes in 1931. Oort would receive them in 1946 and 1942, respectively. At Mount Wilson, both Hale and Adams had received the Gold Medal. Hertzsprung wrote that he did not count Michelson's medal, though he did not explain why.

On Voûte and the Bosscha Observatory, see Pyenson L. , Empire of reason: Exact sciences in Indonesia 1840–1940 (Leiden, 1989), 20–82, and Zuidervaart H. , “Joan Voûte 1879–1963: Een reuzentelescoop op de Bosscha-sterrenwacht te Lembang”, in van Delft D. (eds), De telescoop, erfenis van een Nederlandse uitvinding (Amsterdam, 2008), 45–51.

De Sitter to Hertzsprung, 14 May 1920, WdS 23.9.

See the correspondence of De Sitter with Kapteyn and Hertzsprung from this period (De Sitter papers). In reaction to De Sitter's expansionist plans, the Utrecht astronomer J. van der Bilt even proposed to found a new national observatory. Minutes of the meeting of the Nederlandse Astronomenclub on 3 January 1921, Leiden Observatory Archives.

Drafts of the agreement and accompanying correspondence can be found in WdS 230.

Orchiston W. , “From amateur astronomer to observatory director: The curious case of R. T. A. Innes”, Publications of the Astronomical Society of Australia, xviii (2001), 317–27.

H. E. Wood and W. S. Finsen came from South Africa to Leiden before 1940, but I do not know for how long. Finsen W. S. , “Recollections of William S. Finsen, former director of the Republic Observatory”, Monthly notices of the Astronomical Society of South Africa, lxiv (2005), 45–66.

Hertzsprung to De Sitter, 5/6 February 1924, WdS 23.4.

De Sitter to Van Gent, 4 November 1929, WdS 18.

Schlesinger to De Sitter, 14 February and 14 March 1923, WdS 52. Schlesinger had first considered establishing a southern station in New Zealand. Hoffleit D. , Astronomy at Yale 1701–1968 (New Haven, 1992), 118–21.

Hoffleit , Astronomy at Yale (ref. 68). Schilt was considered for the position of Yale astronomer in South Africa, but the appointment never materialized, partly because of some misunderstandings. WdS 18 and the De Sitter—Hertzsprung correspondence of January—February 1925 in WdS 23.4.

De Sitter—Hertzsprung correspondence 1927, WdS 23.5 and AH C46/6.

Schlesinger to De Sitter, 25 April 1927, WdS 52. Schlesinger had strongly advised against it: “I believe he would be harassed even more than most of us by administrative details”.

De Sitter to Wood , 7 May 1930, WdS 67.

See draft budgets in WdS 241.

Kuiper to Hertzsprung, 8 June 1929. Copy in WdS 23.6. Kuiper contemplated going to Java again in 1935; see DeVorkin D. H. , Henry Norris Russell, dean of American astronomers (Princeton, 2000), 318, and Osterbrock D. E. Gustafson J. R. Unruh W. J. Shiloh , Eye on the sky: Lick Observatory's first century (Berkeley, 1988), 202.

Pyenson , Empire of reason (ref. 60), 81.

De Sitter , Nota (ref. 34).

Hertzsprung to De Sitter, 20 January 1926, WdS 23.5. J. Stein cited further praise from Schlesinger in 1928. Stein J. , s.j., “De Nederlandsche Astronomenclub 5 oct. 1918–5 oct. 1928”, Hemel en Dampkring, xxvi (1928), 335–47.

Schlesinger to De Sitter, 6 December 1927, WdS 52. Hertzsprung had just received a tempting offer from Copenhagen; in this letter, Schlesinger explained to De Sitter why he had told Hertzsprung to stay in Leiden.

Shapley to De Sitter, 22 December 1928, WdS 54. The remark that Leiden was the place “where they grow tulips and astronomers for export” is also attributed to Shapley, for example in Van Herk, De Leidse Sterrewacht (ref. 3), 85. The oldest quote of this remark I have found was from the South African minister for education in his speech at the opening of the relocated Leiden Southern Station in 1957. He said that Americans considered gin, tulips and astronomers as the main Dutch exports. “Rede deur sy Edele die Minister van Onderwys, Kuns en Wetenskap, mnr. J. H. Viljoen by geleentheid van die opening van die Leidse Sterrewag te Hartbeespoort”, Hemel en Dampkring, lv (1957), 213–15.

As far as I know, the only Leiden Ph.D. students who pursued a career in astronomy from this period were H. G. and E. F. van de Sande Bakhuyzen, J. A. C. Oudemans, A. Pannekoek and J. Stein. J. G. E. G. Voûte became an astronomer too, but he did not finish his Ph.D. Kapteyn was attached to Leiden observatory in the beginning of his career, but he studied in Utrecht and obtained a Ph.D. in mathematics there.

Lankford J. , American astronomy: Community, careers, and power, 1859–1940 (Chicago, 1997), 75 ff.

Ibid., and Hutchins R. , British university observatories 1772–1939 (Aldershot, 2008).

It was made possible by the new Academisch Statuut (university statute) of 1921. Groen M. , Het wetenschappelijk onderwijs in Nederland van 1915–1980, een onderwijskundig overzicht, vii: Wis- en natuurkunde (Eindhoven, 1986), 82–7.

This described situation is that of after 1921; before that, the doctoraal degree was a combined degree in astronomy and mathematics.

The De Sitter archive contains the lists of students who followed this course in 1927–34, WdS 119.

De Sitter-Suermondt , Willem de Sitter (ref. 8), 32; Hins C. , “In memoriam Willem de Sitter”, Leidsch Dagblad, 22 November 1934.

Almanak van het Leidsch Studentencorps, 1910 and 1911.

Adriaan Blaauw, interview with David DeVorkin (1979), OH.

Hertzsprung to De Sitter, 23 October 1920, WdS 23.2. N. W. Doorn later obtained his Ph.D. in Amsterdam with Pannekoek.

Adriaan Blaauw, interview with the author (2009).

Draft of a letter of Hertzsprung to De Sitter, probably 1918, AH, C46/10. Schlesinger said that Hertzsprung was “a very poor speaker in at least four languages”. Hoffleit , Astronomy at Yale (ref. 68), 142.

Bart Bok and Adriaan Blaauw, interviews with David DeVorkin (1979), OH.

Cf. a conflict between Kapteyn and Kohlschütter and Adams at Mount Wilson. See DeVorkin in The legacy of J. C. Kapteyn (ref. 2), 143–5.

Hertzsprung to De Sitter, 10 October 1919, WdS 23.2. Cf. A. Wesselink, interview with David DeVorkin (1977), OH.

Bart Bok, interview with David DeVorkin (1979), OH; Adriaan Blaauw, interview with the author (2009).

Bart Bok, interview with David DeVorkin (1979), OH.

Hertzsprung to De Sitter, 12 December 1930 and 14 January 1931, WdS 23.7. He referred to recent work by S. I. Bailey (Harvard) and J. Larink (Bergedorf, Bonn).

Bart Bok, interview with David DeVorkin (1979), OH.

Including van de Sande Bakhuyzen H. G. Oudemans J. A. C. Pannekoek A. Stein J. ,

Lankford , American astronomy (ref. 81), 136–9.

De Sitter to the Dutch ambassador in Washington, 7 May 1926, WdS 81.

Hertzsprung to De Sitter, 10 April 1927, WdS 23.5.

Hertzsprung to De Sitter, 22 April 1927, WdS 23.5.

Osterbrock , Eye on the sky (ref. 70), 200–3.

Cf. DeVorkin , Henry Norris Russell (ref. 70), 315, 321.

Herrmann , Ejnar Hertzsprung (ref. 56), 50.

Lankford , American astronomy (ref. 81), 93.

They were called “the generals” by Peter van de Kamp; interview with David DeVorkin (1977), OH.

Hertzsprung to De Sitter, 19 April 1927, WdS 23.5.

Van Rhijn to De Sitter , 27 November 1922, WdS 48.

Bart Bok, interview with David DeVorkin (1979), OH. See also Levy D. H. , The man who sold the Milky Way: A biography of Bart Bok (Tucson, 1995).

van Berkel K. , “Growing astronomers for export: Dutch astronomers in the United States before World War II”, The legacy of J. C. Kapteyn (ref. 2), 151–74; DeVorkin D. , “Internationalism, Kapteyn and the Dutch pipeline”, The legacy of J. C. Kapteyn (ref. 2), 129–50. See also Oort J. , “Jongere Nederlandse sterrekundigen op belangrijke posten in het buitenland”, Hemel en Dampkring, xxxix (1941), 355–63. These lists do not mention Kaj Strand, a Danish astronomer who also studied in Leiden in the 1930s.

Pannekoek , Herinneringen (ref. 7), 270.

Lankford , American astronomy (ref. 81), 361.

Hertzsprung to De Sitter, 20 January 1926, WdS 23.5. Cf. Pannekoek , Herinneringen (ref. 8), 269–70.

Lankford , American astronomy (ref. 81), 136–9.

DeVorkin , Henry Norris Russell (ref. 74), chaps. 20 and 21; see also letters from Kuiper to De Sitter, for example 30 October 1933, WdS 36.

Oosterhoff to De Sitter, 29 June 1934, WdS 84.

DeVorkin , Henry Norris Russell (ref. 74), 330.

Berkel Van , “Natuurwetenschap” (ref. 1); Willink , De tweede gouden eeuw (ref. 1).

The most famous expression of this view was the book by De Sitter's close friend, the eminent historian Huizinga Johan : Amerika levend en denkend (1927). See also Knegtmans P. J. , “De Amerikaanse verleiding: Veranderende oriëntaties in de Nederlandse wetenschapsbeoefening”, in Boterman F. Vogel M. (eds), Nederland en Duitsland in het Interbellum (Hilversum, 2003), 233–49; van Berkel Klaas , “Amerikanisering van de Nederlandse universiteit? De chemicus H. R. Kruyt over Hoogeschool en Maatschappij (1931)”, Tijdschrift voor de geschiedenis der geneeskunde, natuurwetenschappen, wiskunde en techniek, xii (1989), 1989–225; Van Lunteren F. Hollestelle M. , “Paul Ehrenfest and the dilemmas of modernity” (forthcoming).

Cf. the reaction of C. E. St John to De Sitter's request for gifts for the Kapteyn fund in 1924, about how Europeans seemed to regard America as an unlimited source of money. His reaction was forwarded to De Sitter by Hale. WdS 22.

De Sitter to Van Lonkhuyzen, 6 June 1934, WdS 106. He mentioned Berkeley and Harvard (in that order) as the best places to study astronomy in the U.S. His remark on the chances of obtaining a position was motivated by his worries about the “universal infection of nationalism”.

Like many of his fellow Flemish nationalists, Minnaert had welcomed German support for the establishment a Dutch-language university in Molenaar Gent. L. , De rok van het universum: Marcel Minnaert astrofysicus 1893–1970 (Amsterdam, 2003), esp. pp. 136–45.

Heijmans H. G. , Wetenschap tussen universiteit en industrie: De experimentele natuurkunde in Utrecht onder W. H. Julius en L. S. Ornstein 1896–1940 (Rotterdam, 1994).

Molenaar , De rok van het universum (ref. 124), 260.

Trustees of Groningen University to the Minister for Education, 10 April 1929; Groninger Archieven, papers of the Board of Trustees of Groningen University, 52.840. They also added that Van Rhijn had difficulties in getting observations from other observatories, as he did not have the international standing of Kapteyn. Van Rhijn to Trustees, 17 March 1928 and 22 February 1929.

Pannekoek , Herinneringen (ref. 7), 255–64.

Kapteyn J. C. , Openbare les, gehouden bij gelegenheid van de opening van het Sterrenkundig Laboratorium te Groningen, den 16en Januari 1896 (Groningen, 1896), 5.

Address 1923, WdS 229. Signatories were: Van Rhijn (Kapteyn Astronomical Laboratory, Groningen), De Sitter (Leiden Observatory), Nijland (Utrecht Observatory), Julius (Heliophysical Institute, Utrecht), and Pannekoek (Astronomical Institute, Amsterdam).

Minutes of the meeting of the Nederlandse Astronomenclub, 5 October 1918, Leiden Observatory Archives.

Hertzsprung to De Sitter, 16 February 1921, WdS 23.2. The “graceful tomb” remark was first made by Easton, but Hertzsprung fully agreed with this diagnosis.

De Sitter to Hertzsprung, 18 February 1921, WdS 23.9. Around the same time, De Sitter considered publishing Communications from the Observatory in Leiden (in English), but on second thoughts, he deemed it too expensive. Sterrewacht dagboek, WdS 227.

Schlesinger to De Sitter, 21 April 1926, WdS 52.

Hertzsprung to De Sitter, 27 January 1927, WdS 23.5.

Stein , “De Nederlandse Astronomenclub” (ref. 77).

Blaauw A. , History of the IAU: The birth and first half-century of the International Astronomical Union (Dordrecht, 1994), chap. 4; Otterspeer W. tot Peursum-Meijer J. Schuller , Wetenschap en wereldvrede: De Koninklijke Akademie van Wetenschappen en het herstel van de internationale wetenschap in het Interbellum (Amsterdam, 1997).

Blaauw , History of the IAU (ref. 136), 57–61; Otterspeer Schuller , Wetenschap en wereldvrede (ref. 137), 99–117. Around the same time, American and French astronomers criticized Kapteyn for having accepted a high German decoration in 1914. Krul, “Kapteyn and Groningen” (ref. 41), 74–6.

Lankford , American astronomy (ref. 81), chap. 11.

Van Lunteren F. , “De oprichting van het Koninklijk Nederlands Meteorologisch Instituut: Humboldtiaanse wetenschap, internationale samenwerking en praktisch nut”, Gewina, xxi (1998), 216–43; Velghe A. G. , “Adolphe Quetelet, stichter en eerste directeur van de Koninklijke Sterrenwacht”, Mededelingen van de koninklijke Academie voor Wetenschappen, Letteren en Schone Kunsten van België, klasse der Wetenschappen, xxxvii/2 (1975), 5–14.

Pannekoek , Herinneringen (ref. 7), 256–7.

On the expeditions: [ van Gent R. ], De reizende astronoom: Nederlandse sterrenkundige expedities naar de Oost en de West (Leiden, 1993); van Berkel K. , “De Akademie, Indië en de bloei van de sterrenkunde in Nederland: De Eclipscommissie van 1899”, in idem (ed.), De Akademie en de Tweede Gouden Eeuw (Amsterdam, 2004), 107–38. Papers related to the funding of the expeditions can also be found in WdS 215.

Jaarboek Rijksuniversiteit Groningen, 1931.

Kohler R. E. , “The Ph.D. machine: Building on the collegiate base”, Isis, lxxxi (1990), 638–62; Gooday G. , “Precision measurement and the genesis of physics teaching laboratories in Victorian Britain”, The British journal for the history of science, xxiii (1990), 1990–51; van Lunteren F. , “‘Van meten tot weten’: De opkomst der experimentele fysica aan de Nederlandse universiteiten in de negentiende eeuw”, Gewina, xviii (1995), 1995–38.

De Sitter to Hertzsprung, 10 and 28 February 1920, WdS 23.9; Hertzsprung to De Sitter, 12 and 20 February 1920, 23.2. On the role of women in American astronomy, see Lankford , American astronomy (ref. 81), chap. 9. The first Dutch women doctor in astronomy was Etine Imke Smit, who obtained her Ph.D. with Kapteyn in Groningen in 1914, see Krul , “Kapteyn and Groningen” (ref. 41), 71. She did not pursue a career in astronomy.

de Sitter W. , Kosmos (The Hague, 1934). See also correspondence in WdS 91.2.

On Stein, see Daling W. D. , “De tweede gouden eeuw: Pater Stein s.j. (1871–1951)”, Gewina, xvi (2003), 96–114. He became director of the Vatican Observatory in 1931.

The one exception I could find was during an eclipse expedition to Sumatra in 1929. A participating engineer (recommended by Voûte) caused trouble by accusing Minnaert of political agitation. Report of the expedition by J. van der Bilt, WdS 215.6.

Lankford , American astronomy (ref. 81), 401.

Hutchins , British university observatories (ref. 82), esp. pp. 211–13.

Lankford , American astronomy (ref. 81), 397–400.

van Berkel K. , “Kwaliteit en zuinigheid in het wetenschappelijk onderzoek”, in Schuyt K. Taverne E. (eds), 1950: Welvaart in zwart-wit (The Hague, 2000), 331–54.

Blaauw A. , ESO's early history: The European Southern Observatory from concept to reality (Garching, 1991).