12. Januar

He died in Castres, where he sat on the Chambre de l’Édit, the court for cases between Catholics and Protestants. His papers and his annotated Diophantus passed to his eldest son, Clément-Samuel.

Fermat was a lawyer and a councillor of the Parlement of Toulouse, and did mathematics in his spare time. He shared results by letter, often through the friar Marin Mersenne in Paris, usually as challenges and almost never with proofs. He published next to nothing.

J Harlen Bretz had argued since 1923 that a single catastrophic flood carved eastern Washington. At the Geological Society of Washington the establishment dismissed it. Glacial Lake Missoula was later found to be the source, and Bretz received the Penrose Medal in 1979, aged 96.