Person: Cassini (3), Dominique
Dominique Cassini (Cassini IV) was a French mathematician and surveyor who worked on his father's map of France.
Mathematical Profile (Excerpt):
- Dominique Cassini is also known as Cassini IV.
- Dominique received his early education in the Paris Observatory, then he attended the Collège du Plessis in Paris and the Collège Oratorien run by the Congregation of the Oratory at Juilly.
- In the same year of 1770, actually on 23 July, Cassini was elected to the Académie des Sciences.
- Only two sheets of Brittany required completion but the project was not finished until 1790 when Cassini presented the map to the National Assembly.
- The Government appointed Cassini as a commissioner, along with Legendre and Méchain, to triangulate the French side.
- Cassini had Méchain as his assistant but he took control and made the measurements with the repeating circle while Méchain was given the task of checking the results with older equipment.
- They forced Cassini to take them into the cellars beneath the building but they found nothing of use to them.
- Although Cassini de Thury had surveyed almost exactly this in 1740, it was the invention of the Borda repeating circle which made the Academy confident that a new much more accurate measurement could be achieved.
- In April 1791 the Academy appointed Cassini, Legendre and Méchain to carry out the task.
- On 19 June Cassini, Legendre, Méchain, and Borda had an audience with King Louis XVI.
- Cassini felt deep loyalty to the King, but none to the revolutionary forces now in control of France.
- Things were becoming more and more difficult for Cassini who was completely out of sympathy with the Revolution.
- Cassini was horrified and the two men, once cordial, never spoke again.
- The second student, a young man of astronomical talent named Jean Perny, returned drunk to the Observatory late one night after a meeting of his Revolutionary club and banged on his patron's door with the butt of his sword, shouting, "Cassini the aristocrat must be killed! He had to be subdued and taken to bed.
- The third student, Alexandre Ruelle, a youthful deserter from a dragoon regiment, whom Cassini had harboured and trained until his amnesty came through, became his benefactor's most bitter enemy.
- The students in the Observatory accused Cassini of publishing their work under his own name without giving them credit.
- Cassini had always acknowledged their work but truth had no place in France during this period.
- The National Assembly changed things at the Observatory by making four posts of Professor, one of which went to Cassini but on half his previous salary, while his students were appointed to the other three professorships.
- Cassini was humiliated and resigned on 6 September 1793.
- The Académie des Sciences had already been disbanded in August 1793, despite Cassini's best efforts to prevent this happening, so he could not turn there for help.
- The National Assembly then took the Cassini map as their own property and when he complained he was arrested and imprisoned on 14 February 1794.
Born 30 June 1748, Paris, France. Died 18 October 1845, Thury, France.
View full biography at MacTutor
Tags relevant for this person:
Astronomy
Thank you to the contributors under CC BY-SA 4.0! 
- Github:
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- non-Github:
- @J-J-O'Connor
- @E-F-Robertson
References
Adapted from other CC BY-SA 4.0 Sources:
- O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive
