Son of Louis Pasteur (1853–1933) who published his first biography in 1884. ALS in French, signed “R. Vallery-Radot,” one page both sides, 4.5 x 7, Institut Pasteur letterhead, December 16, 1894. Untranslated letter to Joseph Bertrand, regarding a legacy of 50,000 francs donated to the Society of the Friends of Science in remembrance of Victor Regnault. In fine condition, with light toning and a slight crease to the upper left. RRAuction COA.