Andrea Del Centina

It is well known that letters of Sophie Germain to Guglielmo Libri are held at the Moreniana Library of Florence. In a short note on Libri’s archives in Florence of 1984, I. Grattan-Guinness remarked, with some regret, that in Sophie Germain’s biography by L.L. Bucciarelli and N. Dworsky these letters were not taken into account. Probably this correspondence was unknown to Bucciarelli and Dworsky so they only referred to the letter that she addressed to Libri on March 1831 which is held at the Bibliothèque Nationale in Paris.

“The letters by Sophie Germain”, wrote Grattan-Guinness in his note, “are the most interesting of the collection [those in the Fondo Palagi Libri] and he reported a few lines of two of them. I went carefully through all the letters and it seemed to me that they deserved to be published in whole. In fact they cast new light on Germain’s personality and her friendship with Libri as well as over some episodes of their life. For instance, I discovered that the (draft of) letter dated July 1819 is not addressed to Libri but to L. Poinsot.

Less known (and probably not known) to the community of historians of mathematics, is also the fact that in the same Library but in the Nuovo Fondo Libri, are preserved many other handwritten documents of Sophie Germain: scientific works, reports of experiments, drafts of letters to C.F. Gauss, A.-M. Legendre and J.-L. Lagrange, remarks on papers by A. Cauchy and C.L. Navier on elasticity, etc., of more than two hundred sheets. Amongst these documents stands out a manuscript of twenty four written pages (of size 335x215 mm) entitled Remarques sur l’impossibilité de satisfaire à l’equation xp+ yp = zp: a version of her work on Fermat’s Last Theorem, that, as is well known, she never published but Legendre inserted in his book on number theory of 1823. This manuscript will be taken into account and studied in a future paper that I intend to devote to Sophie Germain’s contribution in number theory. Here of all this material, of undoubted historical interest and in large part unknown, I present only (part of) the letters she wrote to Legendre [ fig. 1] and Lagrange [fig. 2] other that the one ahe addressed to Poinsot [fig.3].

Sophie Germain was born in Paris in 1776, the middle daughter of a rich silk-merchant. She learned mathematics by herself, studying with great passion and indomitable will in opposition to her parents. She was helped through the correspondence she held with great scholars like Lagrange, Legendre and Gauss, but she never had a normal education, which at that time was available only to men. This marked deeply Sophie Germain’s personality and she felt herself somehow marginalised from the academic world. Although she had earned fame by her work on elasticity, she obtained her best result in number theory producing a proof of the first case of Fermat’s Last Theorem for all primes p less than 100 .


More informations about these letters can be found in the following paper and in the reference cited therein:

A. Del Centina, Letters of Sophie Germain preserved in Florence, submitted to Hist. Math.

For biographies of the mathematicians cited above: http://www-history.mcs.st-andrews.ac.uk/history/index.html