Of the character of Lagrange as a philosopher, no description, in so few words, can be better than that of M. Laplace: “Among the discoverers who have most enlarged the bounds of our knowledge, Newton and Lagrange appear to me to have possessed in the highest degree that happy tact, which leads to the discovery of general principles, and which constitutes true genius for science. This tact, united with a rare degree of elegance in the manner of explaining the most abstract theories, is the characteristic of Lagrange.” This power of generalization distinguishes all that he has written, and the student of the _Mécanique Analytique_ is amazed when he comes to a chapter headed “Equations Différentielles pour la solution de tous les problèmes de Dynamique,” which, on examination, he finds equally applicable, and equally applied, to the vibrations of a pendulum or the motion of a planet. On the exquisite symmetry of his notation and style, we need not enlarge: the mathematician either is acquainted with it, or should become so with all speed; and others will perhaps only smile at the notion of one set of algebraical symbols possessing more elegance or beauty than another. The separate works of Lagrange are—1. _Mécanique Analytique_, the second edition of which he was engaged upon when he died; the first edition was published in 1788. 2. _Théorie des Fonctions Analytiques_, a system of Fluxions on purely algebraical principles; first edition, 1797; second edition, 1813. 3. _Leçons sur le Calcul des Fonctions_; first published separately in 1806. 4. _Résolution des Equations numériques_; three editions, in 1798, 1808, and 1826. To give only a list of his separate memoirs would double the length of this life: they will be found in the _Miscellanea Taurinensia_, tom. i.-v., and 1784–5; _Memoirs of the Berlin Academy_, 1765–1803; _Recueils de l’Académie des Sciences de Paris_, 1773–4, and tom. ix.; _Mémoires des Savans Etrangers_, tom. vii. and x.; _Mémoires de l’Institut_, 1808–9; _Journal de l’École Polytechnique_, tom. ii. _cahiers_ 5, 6, tom. viii. _cahier_ 15; _Seánces des Écoles Normales_; and _Connoissance des Tems_, 1814, 1817. [Illustration: _Engraved by Ja^s. Mollison._ VOLTAIRE. _From an original Picture by Largillière in the collection of the Institute of France._ Under the Superintendance of the Society for the Diffusion of Useful Knowledge. _London, Published by Charles Knight, Pall Mall East._ ] [Illustration] VOLTAIRE.