Foundation of the Deutsche Geophysikalische Gesellschaft in its international context

. This article describes the international seismological cooperation at the beginning of the last century and how this cooperation changed due to World War I (WWI). These changes were the direct reasons leading to the foundation of the Deutsche Seismologische Gesellschaft (DSG, German Seismological Society) in 1922, which changed its name to the Deutsche Geophysikalische Gesellschaft (DGG, German Geophysical Society) 2 years later. The second part of the article shortly describes the further development of the relationship between German geophysicists and their international colleagues until the beginning of World War II (WWII).


Introduction
In 2022, we celebrated the 100th anniversary of the formation of the Deutsche Geophysikalische Gesellschaft (DGG, German Geophysical Society).The DGG was founded as the Deutsche Seismologische Gesellschaft (DSG, German Seismological Society), which changed its name to the Deutsche Geophysikalische Gesellschaft 2 years later, in 1924.The 100th anniversary of the DGG foundation opened for the opportunity to investigate its wider background.To understand this, one has to look back at the development of the international cooperation in seismology during the decades before World War I (WWI).The following text is the slightly altered, translated version of an article (Schweitzer, 2022) originally published in Germany by the DGG as part of a set of articles under the common title Geophysik im Wandel (Geophysics in Change).

The early roots of international cooperation in seismology
In 1895, shortly before his death, Ernst von Rebeur-Paschwitz (1861-1895, Davison, 1895) published two pathbreaking articles (Rebeur-Paschwitz, 1895a, b), in which he proposed the installation of a worldwide network of seismic stations with common instrumentation, to monitor the seismicity of the Earth and to investigate the Earth's interior.He also proposed the foundation of an international institute (bureau) that should be responsible for collecting and publishing all reports about felt and/or instrumentally observed earthquakes as completely as possible.
Ernst von Rebeur-Paschwitz's ideas were taken up by Georg Cornelius Karl Gerland (1833( -1919( , Sapper, 1940)), who established the Kaiserliche Hauptstation für Erdbebenforschung (Imperial Main Station for Earthquake Research) at the University of Strasbourg and could finally, in 1901, invite seismologists from all over the world to the 1.Internationale Seismologische Konferenz (First International Seismological Conference) in Strasbourg, Alsace, at that time Germany.The main topic of this conference was to establish an institutionalized framework for the international cooperation in seismology.It took two additional International Seismological Conferences and diplomatic negations before Belgium, Bulgaria, Chile, Congo, Germany, Greece, Hungary, Italy, Japan, Mexico, the Netherlands, Norway, Portugal, Romania, Russia, Spain, Switzerland and the United States of America signed an interstate convention for the following 12 years to form the Internationale Seismologische Assoziation (ISA, International Seismological Association).After some changes of the statutes, also Canada, France, UK and Serbia became ISA members in 1907 and Argentina joined in 1913.
Following Ernst von Rebeur-Paschwitz's idea, ISA established a Zentralbureau (central office) in Strasbourg, at Georg Cornelius Karl Gerland's university institute under his directorship, to organize the international seismological data exchange and to publish worldwide bulletins.For an overview of the ISA bulletins see, e.g., Schweitzer and Lee (2003).With this, the global center for the international cooperation in seismology was located in Strasbourg, Alsace. In 1910, after Georg Cornelius Karl Gerland's retirement, Oskar August Ernst Hecker (1864-1938;Kohlschütter, 1938) became the second director of ISA's central office and of the Imperial Main Station.More details about the establishment of ISA, its activities and the work of the Zentralbureau including many additional references can be found in Schweitzer (2003) and Schweitzer and Lay (2019).

ISA becomes a victim of WWI
The political and social "earthquakes" in Europe because of WWI changed everything.Strasbourg, Alsace, became part of France again and with this, the ISA central office became part of the post-war problems between France and Germany.During WWI and until the end of 1918, the central office and the Imperial Main Station in Strasbourg continued working as usual, to the extent possible, but as documented in its published newsletters (ISA, 2023) and the last activity report of Oskar August Ernst Hecker (see de Kövesligethy, 1922), with reduced staff.On 23 December 1918, all German employees of the central office in Strasbourg had to leave the central office and were deported out of France on 6 January 1919, without any possibility of carrying their personal belongings still located in the office with them (Hecker, 1924;Sapper, 1940).The central office and the Imperial Main Station, most of the instrumentation, the scientific material and the libraries of both offices became inaccessible for German seismologists; unfortunately, much of this material got lost forever.
In October 1918, already shortly before the end of WWI, the Royal Society in London had invited representatives of the Allied Nations to an "Inter-Allied Conference on International Scientific Organizations".Participants from eight countries followed the invitation and excluded, in quite an emotional resolution, any future cooperation in international research organizations with colleagues from the Central Powers (Germany, Austria-Hungary, Bulgaria and the Ottoman Empire; Nature, 1918).This statement was the result of strong national feelings after 4 years of war in Europe with never-before-seen cruelties and loss of human lives.However, the statement had far-reaching consequences, because this exclusion of the Central Powers became part of the statutes of the Conseil International des Recherches (International Research Council, IRC) in July 1919, when it was newly founded together with its Unions (e.g., the herein relevant International Union of Geodesy and Geophysics, IUGG) in Brussels and Belgium.Even states that had been neutral during WWI could only join the Council with support by a two-thirds majority of the members.With this construction, the IRC was, as Cock (1983) wrote, "quite openly part of the general post-war policy".

The foundation of the Deutsche Seismologische Gesellschaft (DSG) in 1922
The  , 1922).Then, the delegates journeyed on to meet again for the First General Assembly of the IUGG in Rome, 1 week later, on 2-10 May 1922.There, during this assembly, the new seismology section of the IUGG was established (Rothé, 1922).However, based on the statutes of the IRC, IUGG membership was based on state memberships and the Central Powers were explicitly excluded from joining IRC as members, and no German seismologists were allowed to participate in the assembly.
In the summer of 1922, the German seismologists were internationally isolated and needed a forum for meetings and discussions.Therefore, Emil Wiechert (1861-1928, see, e.g., Mulligan, 2001;Schweitzer and Ritter, 2012;Jacobs and Neunhöfer, 2013) and Oskar August Ernst Hecker invited German seismologists to a special meeting for the afternoon of 19 September 1922, during the yearly conference of the Gesellschaft Deutscher Naturforscher und Ärzte (German Natural Scientists and Physicians), in Leipzig (Wiener and Bauschinger, 1923;Kohlschütter, 1938).During this meeting, Oskar August Ernst Hecker proposed the foundation of the Deutsche Seismologische Gesellschaft (DSG) as the new home for German seismologists and in parallel, a counterweight to the German hostile institutions founded by the IUGG (Hecker, 1922: "zur gleichen Zeit ein Gegengewicht gegen die von der deutschfeindlichen Union géodesique et géophysique begründeten Landesinstitute"), and presented some drafted statutes.The 24 seismologists present spontaneously endorsed the idea and on 21 September they founded this society by adopting its statutes (Jacobs and Börngen, 2019).
There were of course many more people in Germany interested in seismology than the 24 founding members present in Leipzig.Oskar August Ernst Hecker, just elected Geschäftsführende Vorsitzende (acting chair is the secretary) of the DSG, informed colleagues not present in Leipzig by letter about the new society and asked for their support by becoming DSG members (Hecker, 1922).Oskar August Ernst Hecker's letters also contained a copy of §2 of the DSG statutes with the objectives of the society (here translated from German; see also Fig. 1): "The German Seismological Society intends to foster theoretical and applied seismology and related topics.It tries to achieve this by 1. supporting the scientific exchange of ideas between its members, 2. supporting the scientific relations to related corporations, 3. if applicable, editing scientific publications or participating in already exiting publication projects, 4. organizing scientific meetings, 5. promoting all other seismological research and education related interests." The news about the DSG foundation must have been distributed quite fast, and a list of DSG members from 15 December 1922 already contained 46 members (Table 1) of which 7 were registered with addresses outside of Germany (Austria, Canada, Italy, Spain, Switzerland).During the following years, the membership list continued to grow slowly (Table 1).

The development during the following years
For 4-5 October 1923, Oskar August Ernst Hecker had invited the society of German seismologists to the first meeting in Jena, where he had managed the foundation of the new Reichsanstalt für Erdbebenforschung (Imperial Institute for Earthquake Research) as successor to the former Imperial Main Station in Strasbourg (Hecker, 1924) and which had just officially started its work (1 October 1923).The exclusion of the German colleagues from all IUGG activities was of course also true for the other geophysical disciplines, and following a proposal by Carl Mainka (1873-1943;Beiträge zur angewandten Geophysik, 1944), the DSG widened its focus by changing the statutes and renaming the society to the Deutsche Geophysikalische Gesellschaft (DGG) during the second DSG assembly in Innsbruck, Austria (Wiechert, 1925;Jacobs and Neunhöfer, 2013).During the same meeting, the DSG also decided to start the publication of its own scientific journal for its members, the Zeitschrift für Geophysik (ZfG, Journal of Geophysics).Both changes resulted in a jump of DGG memberships after 1924 (Table 1).
In parallel with the negations about a German membership in the League of Nations in Geneva, the general scientific isolation of Germany, Austria, Hungary and Bulgaria became more and more questioned by former neutral states but also by many colleagues from the Allied Nations.Common scientific interests between single German scientists became more important than "old political" problems, and German researchers were issued with invitations to become members of the commissions in the different unions, and it appears as though the IUGG in particular was not part of the strong supporters of the German exclusion.This impression transpires from a 19-page report by Ernst Kohlschütter (1870Kohlschütter ( -1942;;Maurer, 1942) for the German Reichsministerium des Inneren (Imperial Ministry of the Interior), in March 1927, about his international contacts and experiences based on his participation in international conferences (Kohlschütter, 1927).Also, the increasing number of DGG members with foreign addresses shows an improvement in international relations (Table 1).At the end of the 1920s, the DGG had become quite an international society, with more than 30 % of its membership residing outside of Germany (Table 1), contrary to the year 2022, when only 145 (12 %) of the 1202 members had an address outside of Germany.Even foreign colleagues are documented to have participated in the yearly DGG assemblies as, e.g., seen by the entries in the guest book of the Taunus Observatory near Frankfurt am Main (Fig. 2).
However, due to the construction of the statutes, German scientists could officially participate in unions of the IRC only after Germany became an IRC member.Even an individual participation in IUGG bodies as a guest was not supported by the German government and the DGG because the German government was focusing on solving the general problem of a German IRC membership for all adherent unions together with conditions which were politically acceptable for Germany.Such conditions were, e.g., formulated by the DGG and adopted in a resolution during its third assembly in Göttingen in 1925.This resolution was then not only published in the assembly minutes (DGG, 1926) but also sent in March 1926 by Oskar August Ernst Hecker, the DGG Vorsitzender (chair), to (at least) the German Reichskanzler (imperial chancellor) and the Imperial Ministry of the Interior (Hecker, 1926).
From the correspondence of Beno Gutenberg (1889-1960;Schweitzer, 1989;Knopoff, 1998Knopoff, , 1999)), as still stored in the Beno Gutenberg collection of the Caltech Archive (2022), it is known that this problem was still unresolved in 1929.At the beginning of 1929, Beno Gutenberg had been invited by Edmond Rothé (1873Rothé ( -1942;;Perrier, 1942;Rothé, 1949) to become a member in one of the Commissions of the Seismological Section of the IUGG.This invitation initiated a longer correspondence between Beno Gutenberg and the DGG Vorstand (executive board), with the result that Beno Gutenberg https://doi.org/10.5194/hgss-14-15-2023 Hist.Geo Space Sci., 14, 15-22, 2023 Figure 1.Facsimile of the attachment to Oskar August Ernst Hecker's letter (Hecker, 1922) to Carl Wolfgang Lutz (1878-1946;Angenheister, 1987) containing § 2 of the DSG statutes, written in old German handwriting, as adopted on 21 September 1922.followed the wish of the DGG Executive Board and kindly refused the invitation to become a Commission member in a letter to Edmond Rothé from 23 April 1929.However, Beno Gutenberg also wrote that he was willing to enter into private correspondence with the Commission members and that he would like to be informed about the work of the Commission since, somewhen, Germany would become a Union member ("ich gerne zu persönlicher Korrespondenz mit deren Mit-gliedern bereit und würde mich freuen, wenn ich über die Arbeit der Kommission auf dem Laufenden gehalten würde, da doch einmal Deutschland in die Union eintreten wird").The Beno Gutenberg collection also contains a longer correspondence from the same year (1929) between Beno Gutenberg, Kohlschütter, Walter Davis Lambert (1879-1968;Whitten, 1973), who was influential in the Geodesy Section of the IUGG and the Geodesy Section of the American Geophysi-  (1888-1993;e.g., Emmerich and Schweitzer, 1988) on 22 September 1927, but also lists some of the participants at the Fifth DGG annual meeting in Frankfurt am Main, who visited the observatory as part of the conference program on the afternoon of 28 September 1927 (Schmidt, 1927).From this entry we know that at least five of the conference participants came from abroad https://doi.org/10.5194/hgss-14-15-2023Hist.Geo Space Sci., 14, 15-22, 2023 cal Union, and the Secretary General of IUGG and of the IRC Henry George Lyons (1864-1944;Dale, 1944) about discussions on how to solve the persistent problem of a German membership.

Germany becomes an IUGG member
This blocked situation continued until 1930, when for the first time, German researchers participated in the IUGG General Assembly in Stockholm, Sweden, as guests, and the DGG Executive Board decided to prepare together with other disciplines a German IUGG membership.Furthermore, the IRC had moved and already asked the Central Power states to become IRC members.In 1931, after long discussions within the IRC (Cock, 1983), the IRC adopted a major change of its statutes, which resulted in a larger independence of the union with own rights to manage their memberships and a name change to the International Council of Scientific Unions (ICSU), which existed in this form until 2018.
Reports about the ongoing negotiations regarding the German IUGG membership were on the agenda of the DGG membership meetings during the following years.The major issue to be solved was an internal one: the German government had to find a way to finance the yearly IUGG membership fee and the travel costs of the delegates to the IUGG General Assemblies.Therefore, in the following IUGG Assemblies in Lisbon, Portugal (1933), andEdinburgh, UK (1936), German scientists still participated as guests but became more and more involved in IUGG activities.The long-standing DGG Chair, Kohlschütter (1927Kohlschütter ( -1929Kohlschütter ( , 1930Kohlschütter ( -1936)), was directly involved in the discussions and was installed by the German government as Chair of the Deutsche Vereinigung für Geodäsie und Geophysik (German Union for Geodesy and Geophysics).Finally, on 6 February 1937, Kohlschütter could inform the IUGG that Germany is joining the Union (Kohlschütter, 1937).Then, during the following IUGG General Assembly in Washington DC in September 1939, the few German scientists, who made it to the conference despite the start of a new war in Europe, could be specially welcomed as members and no longer guests of the International Association of Seismology (Naumann and Rothé, 1940, p. 226).
The reorganization of the international scientific landscape after World War II (WWII) was then no longer characterized by new exclusion rules for individual countries but by the will to cooperate and communicate.A visible sign of this is, e.g., the foundation of the Federation of European Seismologists in 1950, which, as the European Seismological Commission (ESC), was incorporated in 1951 into the nownamed International Association of Seismology and Physics of the Earth's Interior (IASPEI), and subsequently, in the IUGG; the German Wilhelm Hiller (1899-1980;Schneider, 1980) was its first president from 1951 to 1956.

Outlook
Founded in scientific isolation of Germany in the post-war years of WWI, the DGG has developed into quite an agile centenarian with around 1200 members.I am sure that the 24 founding fathers did not dream of such a successful development when the society was founded in 1922.The initial reasons for a separate national society described here have disappeared over time.What has remained, however, is the desire to have a formal framework for the coordination of joint scientific activities and for the exchange of scientific results.For many German early-career scientists, a first oral or poster presentation during one of the yearly DGG assemblies was often the beginning of a long-lasting career in geophysics and, last but not least, the DGG offers the possibility of regular meetings between colleagues and friends.
However, what already became visible in the 1920s was confirmed during the further development of geophysics: a self-chosen or forced long-term isolation of individual states from the international discourse leads to worse science for everyone involved.New scientific findings in geophysics depend on the (free) exchange of global observations and data.That is why it is important to maintain cross-border contacts and not to let them break off, even when there are political differences between the states.The bridge-building function of scientific exchange in conflict situations has often been documented.The IUGG with its associations and the DGG have also repeatedly contributed to this over the past 100 years.

Additional information. Additional biographical information for
Victor Conrad, Georg Cornelius Karl Gerland, Beno Gutenberg, Inge Lehmann, Carl Mainka, Ernst von Rebeur-Paschwitz and Emil Wiechert can be found in the compilation of geophysicist biographies by Kertz (2022) and for Oskar August Ernst Hecker, Beno Gutenberg and Emil Wiechert in Jacobs and Börngen (2019), who published a collection of biographies for all 24 founding members of the DSG/DGG.

Data availability.
No data sets were used in this article.
Competing interests.The author has declared that there are no competing interests.
Disclaimer.Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Jo Wassermann, for the copies of letters from Carl Wolfgang Lutz's files, Alexander Rudloff, Ellen Gottschämmer, Franz Jacobs and Michael Lindenfeld, for their help in finding old DGG membership lists, Kasper Fischer, for the most recent DGG membership numbers, Myrto Pirli, for a critical review of the text, and two anonymous reviewers, for corrections in the paper.
Review statement.This paper was edited by Roman Leonhardt and reviewed by two anonymous referees.

Figure 2 .
Figure 2.As an example of the international contacts of the DGG, this is a page from the guest book of the Taunus Observatory near Frankfurt am Main from 1927 (courtesy of the Seismology Group, Goethe University Frankfurt).This page not only documents the visit of the Danish seismologist Inge Lehmann(1888-1993; e.g., Emmerich and Schweitzer, 1988)  on 22 September 1927, but also lists some of the participants at the Fifth DGG annual meeting in Frankfurt am Main, who visited the observatory as part of the conference program on the afternoon of 28 September 1927(Schmidt, 1927).From this entry we know that at least five of the conference participants came from abroad (whether it was solely for the conference or another reason for staying in Germany is an open question): VictorConrad (1876Conrad ( -1962;; e.g.,  Hader, 1962)  (Vienna, Austria), Walter Davis Lambert (1879-1968) (Washington DC, USA) here together with his sister Mary B. Lambert (New York City, USA), Pavel Mikhailovich Nikiforov (1884-1944) (Leningrad, Soviet Union),Leo Wenzel Pollak (1888-1964;Kistermann, 1999) (Prague, Czechoslovakia) and Adalbert Prey(1873-1949; Ferrari d'Occhieppo, 1981)  (Prague, Czechoslovakia).
Figure 2.As an example of the international contacts of the DGG, this is a page from the guest book of the Taunus Observatory near Frankfurt am Main from 1927 (courtesy of the Seismology Group, Goethe University Frankfurt).This page not only documents the visit of the Danish seismologist Inge Lehmann(1888-1993; e.g., Emmerich and Schweitzer, 1988)  on 22 September 1927, but also lists some of the participants at the Fifth DGG annual meeting in Frankfurt am Main, who visited the observatory as part of the conference program on the afternoon of 28 September 1927(Schmidt, 1927).From this entry we know that at least five of the conference participants came from abroad (whether it was solely for the conference or another reason for staying in Germany is an open question): VictorConrad (1876Conrad ( -1962;; e.g.,  Hader, 1962)  (Vienna, Austria), Walter Davis Lambert (1879-1968) (Washington DC, USA) here together with his sister Mary B. Lambert (New York City, USA), Pavel Mikhailovich Nikiforov (1884-1944) (Leningrad, Soviet Union),Leo Wenzel Pollak (1888-1964;Kistermann, 1999) (Prague, Czechoslovakia) and Adalbert Prey(1873-1949; Ferrari d'Occhieppo, 1981)  (Prague, Czechoslovakia).
first General Assembly of IUGG was planned in Rome for May 1922.But there was still an unsolved problem with ISA.The original convention from 1904 had been signed for 12 years.The last ISA meeting before WWI had been in Manchester, UK, in 1911.The next meeting was planned for St.Petersburg, Russia, in 1914, butthis meeting had to be canceled because of the outbreak of the war.In 1916, when the contract period of the ISA convention officially ended, ISA member states were fighting on both sides of the WWI fronts and a new convention or a renewal of the expiring one was not possible.Also, because of the London 1918 resolution, there was no general interest to revitalize the ISA after WWI.To formalize the end of the interstate convention, a joint Third General Assembly and Fifth Conference of the Permanent Commission of ISA was organized in Strasbourg, France, on 24-25 April 1922.At the end of this final meeting, ISA was dissolved (de Kövesligethy

Table 1 .
DGG memberships during the first 10 years, regularly published as a separate list or as published in the DGG journal Zeitschrift für Geophysik (ZfG).* Copy existing in the archive of the author.