WILLIAM JACOB, a distinguished Dutch geometer and natural philosopher, was descended of an ancient and honourable family, and born at Bois-le-dur, in Holland, Sept. 27, 1688. The name of his family was properly Storm van s'Gravesande. He studied the civil law at Leyden; but the mathematics were his favourite pursuit. When he had taken his doctor's degree in 1707, he settled at the Hague, where he practised at the bar, and cultivated the acquaintance of learned men. In May 1713 he, with some other young men distinguished for their acquirements, organized a review entitled Le Journal Litteraire, which was continued without interruption till 1722. In 1715 s'Gravesande, in the capacity of secretary of legation, accompanied the deputies of the states-general sent to London to compliment George I. on his accession to the throne, and there, through the influence of Dr Burnet, Bishop of Salisbury, was admitted a member of the Royal Society. He returned the following year to the Hague, and in 1715 was appointed ordinary professor of mathematics and astronomy in the academy of Leyden. During the vacations of 1721 and 1722, s'Gravesande made two journeys to Cassel to visit the landgrave of Hesse, a prince who showed an enlightened taste for experimental philosophy, and generously furthered its advancement. In 1724 he resigned the rectorship of the academy, to which he had previously been promoted, and on this occasion pronounced a discourse De Ecidentia, which has been prefixed to the third edition of his Elements of Physics. In 1730 he added to his ordinary course civil and military architecture, which he taught in Dutch; and in 1734 he was also appointed to teach philosophy, including logic, metaphysics, and ethics. S'Gravesande died Feb. 28, 1742, at the age of fifty-five. His principal works are: Essai de Perspective, Hague, 1711; Physics Elementa Mathematica, experimentis confirmata, sive Introductio ad Philosophiam Newtonianam, Hague, 2 vols. 4to, 1720-1742; Philosophia Newtoniana Institutiones in usus academici, an abridgement of the preceding, Leyden, 1723, 1728, and 1744; Matheseos Universalis Elementa, quibus accedunt, specimen commentarii in Arithmetica universalem Newtoni et de determinanda forma seriei infinitae absunta: Nova Regula, Leyden, 1727, in 8vo; Introductio ad Philosophiam, Metaphysicam et Logicam continens, Leyden, 1736, 1737. In the Dictionnaire Historique of Prosper Marchand may be found a detailed biography of s'Gravesande by Allemand, the editor of the work, who was intimately connected with s'Gravesande and his family. There is also an elaborate life of him in the Biog. Univers., by De Gerando.