French polymath (1717-1783) known for his contributions in the realms of mathematics, physics, philosophy, and music theory; he served as co-editor of the Encyclopedie until 1759. ALS in French, signed “D'Alembert,” one page, 6.75 x 8.75, August 23, 1761. Untranslated handwritten letter to Abbé Pierre-Joseph Roussier, urging him to ask his brother to come and see him to discuss corrections to be made to a job. In very good condition, with scattered soiling, foxing, and staining, and repaired paper loss to the integral address leaf.
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