César François Cassini de Thury

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César François Cassini de Thury

César François Cassini de Thury (born June 17, 1714 in Thury-sous-Clermont , † September 4, 1784 in Paris ; also called Cassini III. ) Was a French geodesist and astronomer .

Life

César François Cassini was the son of Jacques Cassini and the grandson of Giovanni Domenico Cassini , which is why he was also known as Cassini III. referred to as. César assisted his father in surveying northern France in 1733 and 1734, in order to clarify the then controversial question of whether the earth was flattened at the poles or at the equator .

The Cassinis held the erroneous view that the polar radius was greater than the Earth's radius at the equator, a view vehemently disputed by Isaac Newton and other scientists such as Maupertuis . The Cassini data, which they obtained during the national survey, seemed to support a flattening at the equator, but it was shown that neither the one nor the other theory could be proven due to the inaccuracies of the measurements at the time. In order to clarify the matter, expeditions were sent to Peru ( Pierre Bouguer , Charles Marie de La Condamine , Louis Godin ) and Lapland (Maupertuis). While Jacques Cassini never deviated from his view, César Cassini later switched to Newton's correct view.

In 1739 and 1740 he carried out further, very precise surveys of the land and published his results in 1740, now convinced that the earth was flattening at the poles. After additional triangulations, in 1744 he created the Nouvelle Carte Qui Comprend les principaux Triangles qui servent de Fondement à la Description Géométrique de la France Levée par ordre du Roy par Messrs. Maraldi et Cassini de Thury, de l'Académie Royale des Sciences ( New Map, which contains the essential triangles that form the basis of the geometrical description of France, carried out according to the order of the king by Messrs Maraldi and Cassini de Thury, (members) of the Académie Royale des Sciences ), which he presented to the Académie in 1745. For the first time, it summarized all triangulations. Their scale was approximately 1: 1,799,000.

In 1747 Cassini de Thury published a map that no longer only contained the triangles, but also represented places and rivers ( Carte qui comprend tous les lieux de la France qui ont été déterminés par les opérations géométriques ( map containing all the places in France that measured with geometric means )). It consisted of 18 sheets of 141 × 126 cm; their scale was 1: 878,000.

For military reasons, King Louis XV. Cassini in the same year to map France much more precisely, on a scale of 1: 86,400. The duration of this project was estimated at 20 years, but after six years state funding was stopped. Cassini then decided - with the King's consent - to issue the cards himself. An association of fifty high-ranking personalities raised the necessary funds. Because of these difficulties, the measurement and production of the maps dragged on, so that he could no longer see the completion of his life's work. His son Dominique Cassini completed the production of the 182 sheets of the Carte de Cassini .

In 1761 and 1762 he made two extensive trips to Vienna to connect the French network from Strasbourg by triangulations with the Vienna meridian arc from Brno to Varaždin and the Wiener Neustädter baseline measured by Joseph Liesganig at the time . This trip took him to numerous places in southern Germany and Austria (including Mannheim , Würzburg , Bamberg , Bayreuth , Nuremberg , Munich , Passau , Linz , St. Pölten ).

In 1783 his memorandum gave the impetus to Anglo-French trigonometric measurement .

Since 1746 he was a foreign member of the Prussian Academy of Sciences . In 1751 he was elected a member ( Fellow ) of the Royal Society . In 1761 Cassini was made an honorary member of the Bavarian Academy of Sciences .

Like his father and grandfather, Cassini III was. from 1771 director of the Paris observatory , which at that time suffered from a considerable lack of money, which is why he was unable to give astronomy any new impulses.

Honors

The asteroid (24103) Dethury was named after him. The projection method he developed for displaying maps is the name giver for the Cassini Glacier .

Fonts (excerpt)

  • La Méridienne de Paris verifiée ... avec des Observations d'Histoire Naturelle, faites the les Provinces traversées par la Méridienne, par le Monnier . In: Académie Royale des Sciences (ed.): Histoire de l'Académie royale des sciences ... avec les mémoires de mathématique & de physique ... Hippolyte-Louis Guerin, Jacques Guerin, Paris 1740 (580 p., Digitized on Gallica ).
  • For the description of the geometry of France . In: Académie Royale des Sciences (ed.): Histoire de l'Académie royale des sciences ... avec les mémoires de mathématique & de physique ... Imprimerie Royale, Paris 1745, p. 553-560 ( digitized on Gallica ).
  • Description geométrique de la France . J. Ch. Desaint, Paris 1783, doi : 10.3931 / e-rara-1214 (207 pp.).
  • Relation de deux voyages faits en Allemagne par ordre du Roi . Durand, Paris 1763 ( full text in the Google book search).

literature

  • Pierre Demours (Red.): List Chronologique des Observations & Mémoirs de M. Cassini de Thury ... depuis l'année 1731 jusqu'à l'année 1740 inclusivement . In: Académie Royale des Sciences (ed.): Table générale des matières contenues dans l '"Histoire" et dans les "Mémoires de l'Académie royale des sciences". T5 (1731-1740) . tape 5 . Compagnie des Libraires, Paris 1747, p. 77-79 ( digitized on Gallica ).
  • Pierre Demours (Red.): List Chronologique des Observations & Mémoires de M. Cassini de Thury ... depuis l'année 1741 jusqu'à l'année 1750 inclusivement . In: Académie Royale des Sciences (ed.): Table générale des matières contenues dans l '"Histoire" et dans les "Mémoires de l'Académie royale des sciences". T6 (1741-1750) . tape 6 . Compagnie des Libraires, Paris 1758, p. 124–125 ( digitized on Gallica ).
  • Pierre Demours (Red.): List Chronologique des Observations & Mémoires de M. Cassini de Thury ... depuis l'année 1761 jusqu'à l'année 1770 inclusivement . In: Académie Royale des Sciences (ed.): Table générale des matières contenues dans l '"Histoire" et dans les "Mémoires de l'Académie royale des sciences". T8 (1761-1770) . tape 8 . Panckoucke, Paris 1774, p. 161–162 ( full text in Google Book Search).
  • Pierre Demours (Red.): List Chronologique des Observations & Mémoires de M. Cassini de Thury ... 1771–1780 . In: Académie Royale des Sciences (ed.): Table générale des matières contenues dans l '"Histoire" et dans les "Mémoires de l'Académie royale des sciences". T9 (1771-1780) . tape 9 . De Moutard, Paris 1786, p. 155–156 ( digitized on Gallica ).
  • Ludovic Drapeyron: La vie et les travaux geographiques de Cassini de Thury. In: Ludovic Drapeyron: Revue de geographie. 20th year, October 1896. CH. Delagrave, Paris 1896, pp. 241-254 Digitized on Gallica
  • René Taton: Cassini de Thury, César-François (Cassini III) . In: Charles Coulston Gillispie (Ed.): Dictionary of Scientific Biography . tape 3 : Pierre Cabanis - Heinrich von Dechen . Charles Scribner's Sons, New York 1971, p. 107-109 .

Web links

Individual evidence

  1. ↑ a b L. Gallois: L'Académie des Sciences et les origines de la Carte de Cassini . In: Paul Vidal de La Blache, L. Gallois, Emmanuel de Margerie (eds.): Annales de geographie . tape 18 . Armand Colin, Paris 1909, p. 289-310 ( digitized on Gallica ).
  2. ↑ Carte qui comprend touts les lieux de la France qui ont été déterminés par les opérations géométriques digitized on Gallica
  3. ↑ partnership agreement, Acte d'association Visant à rassembler les fonds nécessaires au levé de la carte générale de France de Cassini dite "carte de l'Académie". In: Service historique de l'Armée de Terre, Direction des Archives, Répertoire numérique détaillé de la Sous-série 3 M, Archives du Dépôt général de la Guerre ; Service géographique de l'Armée, pp. 91-96
  4. ^ Relation de deux Voyages faits en Allemagne par ordre du Roi
  5. ^ Mémoire sur la jonction de Douvres à Londres. In: Concerning the Latitude and Longitude of the Royal Observatory at Greenwich; With Remarks on a Memorial of the Late M. Cassini de Thury. By the Rev. Nevil Maskelyne, DDFRS and Astronomer Royal. In: Philosophical Transactions of the Royal Society of London (1776-1886).
  6. ^ Members of the previous academies. César François Cassini de Thury. Berlin-Brandenburg Academy of Sciences , accessed on March 6, 2015 .
  7. ^ Charles Wolf: Histoire de l'Observatoire de Paris, de sa fondation à 1793 . Gauthier-Villars, Paris 1902 ( digitized on Gallica ).
personal data
SURNAME Thury, César François Cassini de
ALTERNATIVE NAMES Cassini III.
BRIEF DESCRIPTION French geodesic
DATE OF BIRTH June 17, 1714
PLACE OF BIRTH Thury-sous-Clermont
DATE OF DEATH September 4, 1784
Place of death Paris