During these years, 1503-1506, Leonardo also resumed (if it is true that he had already begun it before his travels with Cesare Borgia) the portrait of Madonna Lisa, the Neapolitan wife of Zanobi del Giocondo, and finished it to the last pitch of his powers.
In his studio Leonardo worked for several years (about 1470-1477) in the company of Lorenzo di Credi and other less celebrated pupils.
It may be well to explain here that a claim has been set up by his admirers for the celebrated artist, architect and engineer, Leonardo da Vinci, to be regarded as the discoverer of the principles and practice of flight (see Theodore Andrea Cook, Spirals in Nature and Art, 1903).
In the same year, 1490, Leonardo enjoyed some months of uninterrupted mathematical and physical research in the libraries and among the learned men of Pavia, whither he had been called to advise on some architectural difficulties concerning the cathedral.
Again, it must have been the pestilence decimating Milan in1484-1485which gave occasion to the projects submitted by Leonardo to Ludovico for breaking up the city and reconstructing it on improved sanitary principles.
Between the brilliant young sovereign and the grand old sage an immediate and strong sympathy sprang up; Leonardo accompanied Francis on his homeward march as far as Milan, and there determined to accept the royal invitation to France, where a new home was offered him with every assurance of honour and regard.
As to its execution; the conception and style are essentially Florentine, carried out by Leonardo to a point of intense and almost glittering finish, of quintessential, almost overstrained, refinement in design and expression, and invested with a new element of romance by the landscape in which the scene is set - a strange watered country of basaltic caves and arches, with the lights and shadows striking sharply and yet mysteriously among rocks, some upright, some jutting, some pendent, all tufted here and there with exquisite growths of shrub and flower.
Sent messages urgently desiring that Leonardo should await his own arrival in Milan, having seen a small Madonna by him in France (probably that painted for Robertet) and hoping to obtain from him works of the same class and perhaps a portrait.
The Apology and Crito, the Phaedo, Phaedrus and Gorgias of Plato, as well as speeches of Demosthenes and Aeschines, with the Oeconomics, Ethics and Politics of Aristotle, had already been translated by Leonardo Bruni (d.
Michael Scott, the translator of some treatises of Aristotle and of the commentaries of Averroes, Leonardo of Pisa, who introduced Arabic numerals and algebra to the West, and other scholars, Jewish and Mahommedan as well as Christian, were welcome at his court.