French mathematician, physicist, and philosopher of science (1854-1912) who famously formulated the 'Poincare Conjecture,' which went unsolved for nearly a century. Scarce ALS in French, signed “Poincare,” one page, 4.5 x 7, no date. Letter to a lady, in full (translated): "Please excuse me if I have taken so long to answer you. I find your letter already quite ancient coming back returning from a trip that has been delayed more than I had predicted. I am very happy to be able to be agreeable to you. Please believe me dear lady on my entire devotion." In fine condition.
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