Still he did not neglect his painting. He went about the streets of Florence looking for picturesque or beautiful faces, which he transferred to his sketch-book, always carried at his girdle. He attended the execution of criminals to catch the expression of faces or contortion of limbs in agony. Yet so tender-hearted was he, that, Vasari says, "When he passed places where birds were sold, he would frequently take them from their cages, and, having paid the price demanded for them by the sellers, would then let them fly into the air, thus restoring to them the liberty they had lost." He loved art. He said, "In the silence of the night, recall the ideas of the things which you have studied. Design in your spirit the contours and outlines of the figures that you have seen during the day. When the spirit does not work with the hands, there is no artist.... Do not allege as an excuse your poverty, which does not permit you to study and become skilful; the study of art serves for nourishment to the body as well as the soul.... When all seems easy, it is an unerring sign that the workman has but scant ability and that the task is above his comprehension." Enjoying all athletic exercises; so strong that he could bend a horseshoe in his hands; exceedingly fond of horses, of which he owned several,--he still found time to be the life and joy of the brilliant society of Florence; always leading, always fascinating with his intelligent conversation and elegant address. And yet the ambitious Leonardo was not satisfied in Florence. The Medici did not encourage him as they did Michael Angelo. Possibly they felt that he lacked a steady and dominant purpose. He finally made up his mind to try his fortune elsewhere, and wrote the following letter to Lodovico Sforza, Regent of Milan:-- "MY MOST ILLUSTRIOUS LORD,--Having seen and duly considered the experiments of all those who repute themselves masters and constructors of warlike instruments, and that the inventions and operations of the said instruments are not different from those in common use, I will endeavor, without derogating from any one else, to make known to your Excellency certain secrets of my own, and, at an opportune time, I shall hope to put them into execution, if they seem valuable to you. I briefly note these things below:-- "1. I have a method of making very light bridges, fit to be carried most easily, with which to follow the flight of enemies; and others, strong and secure against fire and battle; easy and commodious to lift up and to place in position. I have methods also to burn and destroy those of the enemy. "2. I know, in case of the siege of a place, how to take away the water from the ditches, and to make an infinite variety of scaling-ladders and other instruments pertinent to such an expedition. * * * * *