D'ALEMBERT (Jean le Rond, 1717-1783) was an eminent mathematician. He wrote especially, though not at first exclusively, on mathematical subjects for the "Encyclopaedia." He was, indeed, at the outset, published as mathematical editor of the work. His European reputation in science made his name a tower of strength to the "Encyclopaedia,"--even after he ceased to be an editorial coadjutor in the enterprise. For there came a time when D'Alembert abdicated responsibility as editor and left the undertaking to fall heavily on the single shoulder, Atlantean shoulder it proved to be, of Diderot. The celebrated "Preliminary Discourse," prefixed to the "Encyclopaedia," proceeded from the hand of D'Alembert. This has always been esteemed a masterpiece of comprehensive grasp and lucid exposition. A less creditable contribution of D'Alembert's to the "Encyclopaedia" was his article on "Geneva," in the course of which, at the instance of Voltaire, who wanted a chance to have his plays represented in that city, he went out of his way to recommend to the Genevans that they establish for themselves a theater. This brought out Rousseau in an eloquent harangue against the theater as exerting influence to debauch public morals. D'Alembert, in the contest, did not carry off the honors of the day. D'Alembert's "Eloges," so called, a series of characterizations and appreciations written by the author in his old age, of members of the French Academy, enjoy deserved reputation for sagacious intellectual estimate, and for clear, though not supremely elegant, style of composition. Diderot and D'Alembert are the only men whose names appear on the title-page of the "Encyclopaedia;" but Voltaire, Rousseau, Turgot, Helvetius, Duclos, Condillac, Buffon, Grimm, Holbach, with many besides whom we must not stay even to mention, contributed to the work. The influence of the "Encyclopaedia," great during its day, is by no means yet exhausted. But it is an influence indirectly exerted, for the "Encyclopaedia" itself has long been an obsolete work. There is a legal maxim that the laws are silent when a state of war exists. Certainly, amid the madness of a revolution such as, during the closing years of the eighteenth century, the influence of Voltaire, Rousseau, and the Encyclopaedists, with Beaumarchais, reacting against the accumulated political and ecclesiastical oppressions of ages, precipitated upon France, it might safely be assumed that letters would be silent. But the nation meantime was portentously preparing material for a literature which many wondering centuries to follow would occupy themselves with writing. XIX. MADAME DE STAEL. 1766-1817. In Madame de Stael we encounter a truly redoubtable figure in literature.