Died: 2 February 1911 in Dijon, France

Charles Méray studied at the École Normale Supérieure in Paris. He began his studies in 1854 when he was eighteen years old, and graduated in 1857. After graduating, Méray taught at the Lycée of St Quentin for two years but then left teaching for seven years during which time he lived in a small village near Chalon-sur-Saône.

Following these seven years when he chose not to work, Méray took up a teaching position again in 1866, this time lecturing at the University of Lyon for a year before being appointed as Professor of Mathematics at the University of Dijon. He would continue to work in Dijon for the rest of his career.

Robinson writes in [1]:-

In his time he was a respected but not a leading mathematician. Méray is remembered for having anticipated, clearly and with only minor differences of style, Cantor's theory of irrational numbers, one of the main steps in the arithmetisation of analysis.

So here we have a case of a mathematician who produced work which might have made him one of the leading mathematicians in the world. However, as happened many times throughout history, Méray was unlucky for the genius of his work was not recognised at the time. Others (we give details below) published the same ideas and it would be their work rather than that of Méray which influenced the direction of mathematics. All we can do now is to give Méray the credit he deserves for his remarkable work, even if fate did not allow Méray a role of importance in the development of the subject.

In 1869 Méray was the first to publish an arithmetical theory of irrational numbers in his paper Remarques sur la nature des quantités définies par la condition de servir de limites à des variables données. Others such as Martin Ohm (1829), Bolzano (1835) and Hamilton (1833) had published work on irrational numbers but none of these earlier authors gave a rigorous account. Méray's is the earliest coherent and rigorous theory of the irrational numbers to appear in print. His work was not influenced by Weierstrass (whose work was unpublished) or Dedekind who only published his theories after Cantor's important paper appeared in 1872. Méray followed Lagrange's earlier work but gave rigorous proofs of what Lagrange had only conjectured.

Méray published a second important work in 1872. This work is a book Nouveau précis d'analyse infinitésimale which aims to present the theory of functions of a complex variable using power series. It is another rigorous work and in fact between 1872 and 1894 Méray produced a series of papers which remove geometric considerations from analytic proofs. Méray's work consistently follows Lagrange in basing the whole of analysis on the concept of functions written as Taylor series.

We have noted above that Méray's work had no real influence on the development of mathematics despite being almost exactly the same as the work which would transform the direction of mathematics. It was not that Méray's work went unnoticed. His 1872 book Nouveau précis d'analyse infinitésimale was reviewed by Hermann Laurent in 1873. Hermann Laurent, in his review, ignored Méray's irrational numbers [1]:-

1. A Robinson, Biography in Dictionary of Scientific Biography (New York 1970-1990). 
   http://www.encyclopedia.com/doc/1G2-2830902914.html

Articles:

1. P Djugak, The limit concept and irrational numbers: ideas of Charles Méray and Karl Weierstrass (Russian), Studies in the history of mathematics (Moscow, 1973),176-180.
2. P Dugac, Charles Méray (1935-1911) et la notion de limite, Rev. Histoire Sci. Appl. 23 (4) (1970), 333-350.
3. M López Pellicer, Constructions of real numbers (Spanish), in History of mathematics in the XIXth century Madrid, 1993 Vol. 2 (Madrid, 1994), 11-33.
4. J Molk, Nombres irrationels et la notion de limite, Encyclopédie des sciences mathématique pure et appliquées I (Paris, 1904), 133-160.
5. D Vachov, Anniversaries in mathematics history for 1985 (Bulgarian), Fiz.-Mat. Spis. B'lgar. Akad. Nauk. 28(61) (2) (1986), 137-138.