In the meantime, he was commissioned to paint the portrait of a young girl from a noble family in Milan. At the same time, he began the bronze equestrian statue of Ludovico’s father, Francesco Sforza. For this work, he began an intensive study of horses. Since hunting was the popular sport at the court of the Sforzas, Ludovico owned a stable of the finest Arabian horses, and here Leonardo commenced his drawings. Again, his research for a work of art led him beyond just making preparatory sketches. His studies developed into notes, and his notes into a planned book on the anatomy of the horse.

During these months of waiting for the appointment as military engineer, Leonardo furthered his experiments with cannon. In the course of these experiments, he came across a power that would later revolutionize all industry—steam. He devised—although he attributed the original idea to Archimedes—a water vessel connected to a copper tube which was heated by a fire. The water when flowing into the red-hot tube changed into steam and the pressure of the steam blew out a ball at the mouth of the tube with great force. Leonardo experimented with steam in other ways. He built an apparatus for measuring the transformation of water into vapor. It consisted of a metal box in which was a thin animal bladder partly filled with water. Resting on the top of the bladder was a flat lid attached by a cord hung from two pulleys to a counterweight on the outside. As the water was heated, the steam in the bladder pushed up the lid. As the lid rose both the volume and the pressure could be measured. There were distillation experiments with various condensers, one in particular that anticipated the modern condenser of Leibig, introducing double walls that formed a complete jacket for cooling with water in continual circulation.

Not content with having an idle moment, Leonardo again turned to searching out books that he had not read and trying to fill the gaps in his education. He became especially interested in the German philosopher, Cardinal Cusanus. Cusanus, like himself, had been influenced by Toscanelli and was a man devoted to the natural sciences. Leonardo also studied the philosophy of Aristotle and the writings of St. Augustine. Throughout his life Leonardo believed in an active mind for, as “iron rusts from disuse, stagnant water loses its purity and in cold weather becomes frozen, even so does inaction sap the vigor of the mind.”

Unfortunately, the post of military engineer went to a man named Ambrogio Ferrari. The extent and variety of Leonardo’s proposals were too great for Ludovico to trust. He did not believe that one man could possibly bring all those ideas into being. Ferrari, on the other hand, was a military engineer only, and a man who was content with the customary methods of warfare. Furthermore, Ludovico had at last decided that peaceful negotiations would gain him more than fighting. Thus Leonardo’s chance of recognition was again postponed.

Meanwhile, the money that Leonardo had brought with him from Florence was almost gone. He had been forced to move from his apartment to a single room and now he was barely able to live from day to day. Although the court of Ludovico Sforza was one of the richest in the world, artists were frequently treated as servants; often they were the last to be paid for their services. Also, Leonardo was a foreigner in the city, which meant he was regarded with suspicion.

Because of these reasons, Leonardo finally decided to do what the Milanese artists did—they banded together in groups sharing work and costs. Leonardo had met a young artist of twenty-eight, Giovanni Ambrogio de Predis, at the court of Ludovico. Ambrogio was court painter to the Sforza family and had achieved some success. Ambrogio recognized in the handsome stranger from Florence, however, the touch of genius, and he realized that his own talents would be furthered by learning from Leonardo. The two young men decided to pool their abilities. Ambrogio offered both lodging and a studio; and, in association with his two half-brothers, one a woodcarver, another a miniaturist, and his elder brother, a minter of coins, they would not lack for commissions.

Commissions weren’t long in coming. On April 25, 1483, a contract was signed between Bartolommeo degli Scarlione, a prior of the Fraternity of the Immaculate Conception, and Ambrogio and Leonardo for an altarpiece. The fee was two hundred ducats, with a promise of more if it were delivered on time and was satisfactory to the Fraternity. Delivery date was to be December 8, 1484. Ambrogio was to paint the altar wings and Leonardo the center piece—a picture of the Blessed Virgin and Child.

But when the painting was finished, it was not according to the instructions set forth in the contract. Leonardo had too independent a mind to be bound by conformity. Nor was it completed on time. Indeed, for twenty years the quarrel between the Fraternity and the painters went on. After ten years, Ludovico was asked to intervene for the money owed; after he failed, another ten years went by and the King of France himself was finally asked to settle the dispute. Leonardo wanted his one hundred ducats and the Fraternity offered twenty-five. Eventually, a secret agreement was arrived at and the painting was restored to Leonardo and Ambrogio. Leonardo’s painting, the masterpiece entitled the “Virgin of the Rocks,” now hangs in the museum of the Louvre in Paris.

The day this contract was signed, Leonardo walked back through the city to Ambrogio’s studio near the Ticino gate. He was low in spirits from reading the petty instructions of the contract, and, in this mood, he became aware of the city streets and crowds about him. The noise, the confusion, the smells—yes, the smells were the worst. Garbage, filth, and dust were in heaps where the last rainwater had left them and they buzzed with flies.

Moreover the houses were jammed together and shopkeepers crowded their wares to the edges of the streets, leaving just enough room for the occasional horseman to get through. Latrines were only for the better houses; here, the streets, alleys and even open doorways were toilets. People flung their scraps out of the window and at night in the poorly lit streets could be heard the scurrying of rats. Leonardo stopped, thinking half aloud:

“Two levels. Streets running one above the other—one for pedestrians and one for carts and horses. Yes, and cutting through the whole city a system of canals to carry the city’s waste to a river or to the sea. Why not even ten cities of, say, five thousand houses in each—say, no more than thirty thousand people to a city?”

Intent now on his thoughts he hurried to his home, his mind busy with his visions of new cities.

During the years 1484 and 1485 the bubonic plague swept Italy—the same dreaded Black Death so prevalent in medieval times. Milan was one of the cities most severely stricken. Every courtyard became a hospital and the streets were deserted except for the rumbling carts picking up the dead. On the roads from the city were lines of refugees fleeing to the country. Surrounding cities that had not been infected manned their fortress walls as in wartime to keep the fleeing populations out.

Ludovico at first tried to protect Milan from the spread of the disease; then, frightened, he and his court fled. Even the ruler’s official documents had to be “disinfected” by perfume and then held for a period of time before he would allow them near him.

Leonardo, sensing opportunity, drew out his plans for his new cities. Canals running through them were to be used for barges and the underground conduits greatly resembled those of modern sewage systems. Paths were to have gutters for the adequate drainage of the streets. Public toilets were to be installed. Leonardo even had plans for the control of smoke collecting over the city—by sending it up tall chimneys where it was picked up by fans and driven away over the roofs. The widths of the streets were to be in proportion to the heights of the houses—light and air would circulate freely. Two levels would be connected by graceful ramps—the lower level for the commercial traffic and the upper level for the pedestrians. Where stairs were used they were designed so one could ascend or descend without one person seeing the other. Stables were devised so that animals were fed through openings in their mangers and under these were tunnels of flowing water for the removal of waste.