JOHN BAPTISTE DU, a very learned French philosopher and writer in the 17th century. At 18 he wrote a treatise, in which he explained in a very simple manner Thcodofius's three books of Spheres; to which he added a tract upon trigonometry, extremely perspicuous, and designed as an introduction to astronomy. Natural philosophy, as it was then taught, was only a collection of vague, puzzling, and barren questions; when our author undertook to establish it upon right principles, and published his Astronomia Physica. In 1666 M. Colbert proposed to Louis XIV. a scheme, which was approved of by his majesty, for establishing a royal academy of sciences; and appointed our author secretary of it. He published a great many books; and died at Paris in 1706, of mere old age, being almost 83. He was regius professor of philosophy, in which he was succeeded by M. Varignon. He wrote Latin with purity and elegance.