nardo's model was sufficiently advanced to be placed on the piazza of the Castello, under a triumphal arch. Poets and chroniclers hailed the great statue as one of the wonders of the age. They compared Leonardo to Phidias and Praxiteles, and Lodovico to Pericles and Augustus. Luca Pacioli, the famous mathematician, tells us that the monument was twenty-six feet high, and when cast in bronze was expected to weigh 200,000 pounds. Unfortunately, by this time Lodovico's dominions were already threatened by foreign invaders, and financial difficulties put an end to his most cherished schemes. The statue was never cast, and after the fall of Lodovico and the occupation of Milan by the French, Leonardo's model was allowed to perish.
This statue was the chief, but by no means the only work to which Leonardo's time and labors were devoted during the first ten years of his residence at Milan. Whether in the capacity of architect or engineer, of painter or decorator, the Florentine master's services were in continual request. In 1487 he made a model for the cupola of Milan Cathedral. In 1490 he was summoned to Pavia, to give his opinion on the new Duomo in that city, but was hastily recalled to superintend the decorations of the ballroom in the Castello on the occasion of Lodovico's marriage. Later, he was appointed ducal engineer, and, if he did not actually have a share in the famous Martesana canal, he was no doubt consulted by the duke in the construction of the vast scheme of irrigation by which Lodovico fertilized the Lomellina. These varied occupations left Leonardo little time for painting; yet, during the years which he spent in Lodovico's service, several of his most important works of art were executed, and his famous treatise on painting was written. The one genuine easel-picture of this period which remains is 'The Virgin of the Rocks,' now in the Louvre. Further, in the last years of Lodovico's rule Leonardo painted the masterpiece of his life, 'The Last Supper,' in the refectory of Santa Maria delle Grazie.
After the fall of Duke Lodovico, in 1499, Leonardo left Milan; and the next sixteen years of his life were spent in constant journeyings up and down Italy. During fifteen months he remained in Florence, working at a cartoon for the Servite monks, who had commissioned him to paint an altarpiece for their church of the Annunziata. "For a long time," says Vasari, "he kept them waiting and did nothing at all. At last he produced a cartoon with the Madonna, St. Anne, and the Christ, a work which not only filled all the artists with admiration, but brought a continuous procession of men and women, old and young, to the hall in the convent where it was exhibited. The whole town was stirred, and you might have fancied it was a procession on some solemn feast-day." It was without doubt this composition that he afterwards repeated in oils for Francis I., and which is now in the Louvre.
In July, 1502, we find Leonardo at Urbino, inspecting fortifications for Cæsar Borgia, who had taken him into his service as military engineer and architect. He travelled through Romagna,—"the realm of all stupidity," as he calls it in one passage,—sketching fortresses and drawing plans, and not-
