Leonardo worked very slowly upon his paintings, because he was never satisfied with a work, and would retouch it day after day. Then, too, he was a man of moods, like most geniuses, and could not work with regularity. The picture of the "Last Supper" was painted in Milan, by order of his patron, the Duke, and there are many picturesque stories written of its production. It was painted upon the refectory wall of a Dominican convent, the Santa Maria delle Grazie; and at first the work went off well, and the artist would remain upon his scaffolding from morning till night, absorbed in his painting. It is said that at such times he neither ate nor drank, forgetting all but his great work. He kept postponing the painting of two heads--Christ and Judas. He had worked painstakingly and with enthusiasm till that point, but deferred what he was hardly willing to trust himself to perform. He had certain conceptions of these features which he almost feared to execute, so tremendous was his purpose. He let that part of the work go, month after month, and having already spent two years upon the picture, the monks began to urge him to a finish. He was not the man to endure much pressure, and the more they urged the more resentful he became. Finally, he began to feel a bitter dislike for the prior, the man who annoyed him most. One day, when the prior was nagging him about the picture, wanting to know why he didn't get to work upon it again, and when would it be finished, Leonardo said suavely: "If you will sit for the head of Judas, I'll be able to finish the picture at once." The prior was enraged, as Leonardo meant he should be; but Leonardo is said actually to have painted him in as Judas. Afterward he painted in the face of Christ with haste and little care, simply because he despaired of ever doing the wonderful face that his art soul demanded Christ should wear. The one bitter moment in Leonardo's life, in all probability, was when he came in dire competition with Michael Angelo. When he removed to Florence he was required to submit sketches for the Town Hall--the Palazzo Vecchio--and Michael Angelo was his rival. The choice fell to Angelo, and after a life of supremacy Leonardo could not endure the humiliation with grace. Added to disappointment, someone declared that Leonardo's powers were waning because he was growing old. This was more than he could bear, and he left Italy for France, where the king had invited him to come and spend the remainder of his life. Francis I. had wished to have the picture in the Milan monastery taken to France, but that was not to be done. Doubtless the king expected Leonardo to do some equally great work after he became the nation's guest. Before leaving Italy, Leonardo had painted his one other "greatest" picture--"La Gioconda" (Mona Lisa)-and he took that wonderful work with him to France, where the King purchased it for $9,000, and to this day it hangs in the Louvre.