Leonardo da Vinci (1452-1519) was the natural son of the Florentine notary, Ser Piero Antonio da Vinci. He was placed by his father in the studio of Yerrocchio, and painted the chief figures in that master's picture of the Baptism, now in the Florence Academy. In 1478 Leonardo received his first commission. During this period he was encouraged by Lorenzo de' Medici, and besides numerous records of his other work at this time, there exist studies in the Uffizi and Vatican galleries for an Adoration of the Magi, and a St. Jerome. About 1482 he took service as an engineer with the Sultan of "Babylon," that is, Cairo, and visited Armenia, Cyprus, 'Constantinople, and Egypt. Leonardo's two great works during his first residence at Milan, whither he returned, were the erection of a bronze statue to Francesco Sforza, and the painting of his Last Supper. The Last Supper, which ranks as one of the finest pictures of the world, was painted in oil on the refectory wall of the convent of Santa Maria delle Grazie, at Milan, at the joint expense of the Duke and the Prior. Besides being engaged upon these and minor works, Leonardo was at the head of an academy of arts and sciences, and was studying natural philosophy, geometry, and optics. Early in 1500, or before, he went to Arenice, but in the following year became attached to Caesar Borgia, for whom he travelled as engineer over the greater part of Italy. In 1503 he again settled at Florence, yvhere he was commissioned to paint an altar-piece at Santa Maria dell' Annunziata. The painting was carried out by Filippino Lippi and Perugino. He also began, for the Hall of Council at Florence, The Battle of Anghian, but after several years' work abandoned it. Between 1500 and 1505 two -great portraits were painted, one, that of Ginevra Reuci, now lost, and the Monna Lisa, now in the Louvre. In 1506 Leonardo returned to Milan, where be lived for the next nine years. The two Virgins of the Rocks, one of which is in the National Gallery, belong, however, to this period, as also does the Holy Family in the Louvre. In the autumn of 1514 Leonardo went to Rome, where the brother of his earliest patron, was now Pope. He returned to Milan after a few months, and, after it had fallen to the French, was induced by Francis to return with him across the Alps. Accompanied by Francesco Melzi, he arrived at the Chateau Cloux, near Amboise, which had been assigned him, and here, after living three years, he died in 1519. Although no more than ten of his undoubted pictures remain, Leonardo da Vinci ranks with his rival Michelangelo and the younger Raffaelle, whom he inspired. His drawing, which he did with his left hand (he wrote from right to left), is second only to that of Durer. In the region of science Leonardo was only less great than in that of art. He discovered the construction of the eye, invented the camera obscura and the saw which is still used in the quarries of Carrara, revived the science of hydraulics, and was the founder of the structural classification of plants.