Gabrielle Emilie Le Tonnelier De Breteuil Du Chatelet, marchioness, a French authoress, born in Paris, Dec. 17, 1706, died in Luneville, Aug. 10, 1749. She was married at an early age to the marquis du Chatelet-Lomont, and afterward divided her time between science and dissipation. Not even a love affair with the duke de Richelieu could withdraw her from her studies. In 1733 she became the mistress of Voltaire, and the next year removed with him to Monjeu near Autun, and afterward to the chateau of Cirey, in which the marquis du Chatelet also resided. Here they passed several years in unrestrained freedom, actively engaged in literary pursuits, especially in the study of Newton and Locke, and the marchioness composed her Dissertation sur la nature et la propagation du feu, Institutions de physique, a synopsis of Leibnitz's philosophy, and various other essays. During a stay at the court of Stanislas, the ex-king of Poland, at Luneville, she fell in love with the marquis de Saint-Lambert, by whom she had a daughter, and a few days after giving birth to this child she died in the palace of Luneville. Several of her works were published posthumously, including Principes mathematiques de la philosophic naturelle, a translation of Newton's Principia, with a commentary (1756); Doutes sur les religions revelees, adresses a Voltaire (8vo, 1792); and Lettres inedites d M. le comte d'Argental (12mo, 1806).