WILLIAM JACOB, was descended of an ancient and honourable family, and born at Delft, in Holland, on the 27th of September 1688. The name of his family was properly Storm van s'Gravesande. He studied the civil law at Leyden; but the mathematics, for which he had evinced an early inclination, 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 the month of May 1713, he, in conjunction with a society of young men distinguished for their acquirements, undertook the composition of a periodical review entitled Le Journal Litteraire, which was continued without interruption until the year 1722. In 1715, 'sGravesande, 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 having there Gravesend formed a connection with Dr Burnet, bishop of Salisbury, he 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, 'sGravesande made two journeys to Cassel to visit the landgrave of Hesse, a prince who showed an enlightened taste for experimental philosophy, and generously promoted 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 Evidentia, 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. 'sGravesande died on the 28th of February 1742, at the age of fifty-five, after a period of protracted suffering, during which he preserved unimpaired all his characteristic vivacity. His principal works are as follow, viz. 1. Essai de Perspective, Hague, 1711; 2. Physices Elementa Mathematica, experimentis confirmatae, sive Introductio ad Philosophiam Newtonianam, Hague, in two vols. 4to; 3. Philosophiae Newtonianae Institutiones in usu academico, an abridgment of the preceding, Leyden, 1723, 1728, and 1744; 4. Matheseos Universalis Elementa, quibus accedunt, specimen commentarii in Arithmeticam universalem Newtoni, et de determinanda forma serierii infinite adeuntes Nova Regula, Leyden, 1727, in 8vo; 5. Introductio ad Philosophiam, Metaphysicam et Logicam continens, Leyden, 1736, 1737. In the Dictionnaire Historique of Prosper Marchand may be found a detailed biography of 'sGravesande by Allemand, the editor of the work, who was intimately connected with 'sGravesande and his family.