Editing Kater's pendulum (section)

=== International Association of Geodesy ===
The 1875 Conference of the [[International Association of Geodesy|European Arc Measurement]]  dealt with the best instrument to be used for the determination of gravity. The association decided in favor of the reversion pendulum and it was resolved to redo in Berlin, in the station where [[Friedrich Bessel|Friedrich Wilhelm Bessel]] made his famous measurements, the determination of gravity by means of devices of various kinds employed in different countries, in order to compare them and thus to have the equation of their scales, after an in-depth discussion in which an American scholar, [[Charles Sanders Peirce]], took part.<ref>{{Cite web|last=Zuerich|first=ETH-Bibliothek|title=Bulletin de la Société des Sciences Naturelles de Neuchâtel|url=https://www.e-periodica.ch//digbib/volumes?UID=bsn-001|access-date=2021-10-25|website=E-Periodica|page=256|language=fr}}</ref> Indeed, as the [[figure of the Earth]] could be inferred from variations of the [[seconds pendulum]] length, the [[United States Coast and Geodetic Survey|United States Coast Survey's]] direction instructed [[Charles Sanders Peirce]] in the spring of 1875 to proceed to Europe for the purpose of making pendulum experiments to chief initial stations for operations of this sort, in order to bring the determinations of the forces of gravity in America into communication with those of other parts of the world; and also for the purpose of making a careful study of the methods of pursuing these researches in the different countries of Europe.<ref>{{Cite web|title=Report from Charles S. Peirce on his second European trip for the Anual Report of the Superintendent of the U. S. Coast Survey, New York, 18.05.1877|url=https://www.unav.es/gep/Informe18.05.1877En.html|access-date=2021-10-25|website=www.unav.es}}</ref>

The determination of gravity by the reversible pendulum was subject to two types of error. On the one hand the resistance of the air and on the other hand the movements that the oscillations of the pendulum imparted to its plane of suspension. These movements were particularly important with the apparatus designed by the Repsold brothers on the indications of Bessel, because the pendulum had a large mass in order to counteract the effect of the viscosity of the air. While [[Emile Plantamour]] was carrying out a series of experiments with this device, [[Adolphe Hirsch|Adolph Hirsch]] found a way to demonstrate the movements of the pendulum's suspension plane by an ingenious process of optical amplification. Isaac-Charles Élisée Cellérier, a mathematician from Geneva and Charles Sanders Peirce would independently develop a correction formula that allowed the use of the observations made with this type of gravimeter.<ref>{{Cite web|last=texte|first=Académie des sciences (France) Auteur du|date=January 1880|title=Comptes rendus hebdomadaires des séances de l'Académie des sciences / publiés... par MM. les secrétaires perpétuels|url=https://gallica.bnf.fr/ark:/12148/bpt6k3047v|access-date=2021-10-25|website=Gallica|pages=1463–1466|language=fr}}</ref><ref>{{Cite book|last=Ibáñez e Ibáñez de Ibero|first=Carlos|title=Discursos leidos ante la Real Academia de Ciencias Exactas Fisicas y Naturales en la recepcion pública de Don Joaquin Barraquer y Rovira|publisher=Imprenta de la Viuda e Hijo de D.E. Aguado|year=1881|location=Madrid|pages=70–73|language=ES}}</ref>

President of the Permanent Commission of the European Arc Measurement from 1874 to 1886, [[Carlos Ibáñez e Ibáñez de Ibero|Carlos Ibáñez Ibáñez de Ibero]] became the first president of the [[International Association of Geodesy|International Geodetic Association]] (1887–1891) after the death of [[Johann Jacob Baeyer]]. Under Ibáñez's presidency, the International Geodetic Association acquired a global dimension with the accession of the [[United States]], [[Mexico]], [[Chile]], [[Argentina]] and [[Japan]]. As a result of the work of the International Geodetic Association, in 1901, [[Friedrich Robert Helmert]] found, mainly by gravimetry, parameters of the [[Geodesics on an ellipsoid|ellipsoid]] remarkably close to reality.<ref>{{Cite book|title=Géodésie in Encyclopedia Universalis|publisher=Encyclopedia Universalis|year=1996|isbn=978-2-85229-290-1|pages=Vol 10, p. 302|language=FR|oclc=36747385}}</ref><ref>{{Cite journal|last=Torge|first=Wolfgang|date=2016|editor-last=Rizos|editor-first=Chris|editor2-last=Willis|editor2-first=Pascal|title=From a Regional Project to an International Organization: The "Baeyer-Helmert-Era" of the International Association of Geodesy 1862–1916|url=https://link.springer.com/chapter/10.1007%2F1345_2015_42|journal=IAG 150 Years|series=International Association of Geodesy Symposia|volume=143 |language=en|location=Cham|publisher=Springer International Publishing|pages=3–18|doi=10.1007/1345_2015_42|isbn=978-3-319-30895-1}}</ref><ref>{{Cite journal|last=Torge|first=W.|date=2005-04-01|title=The International Association of Geodesy 1862 to 1922: from a regional project to an international organization|url=https://doi.org/10.1007/s00190-004-0423-0|journal=Journal of Geodesy|language=en|volume=78|issue=9|pages=558–568|doi=10.1007/s00190-004-0423-0|bibcode=2005JGeod..78..558T |s2cid=120943411 |issn=1432-1394}}</ref><ref>{{Cite journal|last=Soler|first=T.|date=1997-02-01|title=A profile of General Carlos Ibáñez e Ibáñez de Ibero: first president of the International Geodetic Association|url=https://doi.org/10.1007/s001900050086|journal=Journal of Geodesy|language=en|volume=71|issue=3|pages=176–188|doi=10.1007/s001900050086|bibcode=1997JGeod..71..176S |s2cid=119447198 |issn=1432-1394}}</ref>