05/04/2023

In Folha, Viana tells the story of the 'faceless' mathematician.

Reprodução

Reproduction of Marcelo Viana's column in Folha de S. Paulo.

Adrien-Marie Legendre (1752–1833) is one of the great French mathematicians. His works cover diverse areas of mathematics, and concepts bearing his name are found in mathematics textbooks today. He was knighted by Napoleon and is one of the 72 scientists whose names are inscribed on the Eiffel Tower.

However, little is known about his life. The family was wealthy, but their assets were confiscated at the height of the French Revolution, in the same year, 1793, that the revolutionary government closed the Academy of Sciences, their source of income. The only good thing that year was his marriage to Marguerite-Claudine Couhin, his lifelong companion.

Until 2005, only one portrait of Legendre was known, regularly used in history of mathematics textbooks and scattered across the internet. It was in that year that two students from the University of Strasbourg discovered that this portrait was also used to represent another person, the revolutionary politician Louis Legendre (1752–1797), who had the same surname.

The subsequent investigation showed that the image was part of a collection of lithographs of celebrities published in 1833 by the artist François-Séraphin Delpech and that it undoubtedly depicts the politician, not the mathematician. Suddenly, Adrien-Marie no longer had a face!

How could such an error have occurred and persisted for over a century? The first misattribution of the portrait is believed to have happened in a book about the work of scientists published by Alphonse Rebière in 1900. By that time, both Legendre brothers, the mathematician and the politician, had already died, as well as everyone who knew them in life.

The most ironic thing is that, although they were not related, despite sharing the same surname, their lives were connected: Louis played a key role in the closure of academies and scientific societies, which condemned Adrien-Marie to poverty. To give an idea of the character, it suffices to mention that Louis Legendre was the author of the proposal that, in addition to being guillotined, King Louis XVI should have his body quartered into 84 parts, so that each department of France could receive a piece.

Another twist occurred in 2007, when mathematician Gérard Michon discovered, in the Library of the Institut de France – an institution created by Napoleon in 1803 to replace the then-defunct Academy of Sciences – a collection of watercolors by the painter Julien-Léopold Boilly depicting members of the institute.

To read the full text, visit the newspaper's website.