MADAME DE, whose full name was Gabrielle Emilie Le Tonnelier de Breteuil, Marquise du Chastellet, has obtained celebrity by her translation of the Principia of Newton, as well as by being l'Amie de Voltaire. This accomplished lady was mistress of Latin, Italian, and English, and appears to have made great proficiency in mathematics. Her translation was considered worthy of the revision of Clairaut. She was also the author of Institutions de Physique, published in 1740, and so popular as to appear in a second edition at Amsterdam in 1742. The translation of Newton was a posthumous publication, and the labour bestowed on it is said to have caused her death, which took place at Luneville in 1749.