Part 4

Finally, Leonardo made a small wax model of the proposed statue and showed it to Ludovico. The nobleman was impressed by its originality. Most of the ideas contributed by other sculptors were mere variations of what had already been done many times. Also, the other plans called for bronze of not more than two thousand pounds, while Leonardo envisioned a statue fifty times that size! Ludovico awarded the commission to Leonardo.

Leonardo was to work on this commission for ten years and it was destined never to be immortalized in bronze, for reasons that will be explained later. His energies, as usual, were poured into many schemes. Growing out of his work on the monument he planned one book on the subject of casting in bronze and another on the anatomy of the horse. But the one subject, which he began to study in this period and which would occupy the remainder of his life, was the study of human anatomy. So Leonardo, in the midst of all his other activities, wrote in his notes, “On the second day of April 1489 the book entitled _Of the Human Figure_.”

The sources of anatomical study up to Leonardo’s day had been the Greeks—Hippocrates and Galen—and the Arab—Avicenna. Books on this subject were few, and the anatomical diagrams were crude and inaccurate. Galen, for example, had based his studies on the dissection of monkeys. Renaissance anatomists had explained his errors by pointing out that man had probably changed since Galen’s time. The Church had stepped in during the fourteenth century with an edict that was interpreted as a prohibition against dissection of the human body. In Italy, however, there were some dissections. They could only use, for this purpose, the bodies of criminals, slaves, and people of foreign birth. In Florence, anatomy was studied by the artists, and Leonardo had undoubtedly watched Pollaiuolo at work on a corpse that that artist had dissected.

In 1489 Leonardo, from the results of his own investigation, produced drawings of the skull and backbone whose careful attention to detail are—even today—classics in art and anatomy. With infinite patience and with a saw of his own invention he had halved a skull and drew for the first time with accuracy the curves of the frontal and sphenoid bones. He drew the lachrymal (tear) canal, and he was the first to show the cavity in the superior maxillary bone—not discovered again until 1651, by Highmore—now named “the antrum of Highmore.” He was the first to demonstrate the double curvature of the spine and its accompanying vertebrae, the inclination of the sacrum, the shape of the rib cage, and the true position of the pelvis. He planned a whole series of books that would include from head to foot and from inside to outside every section of the human apparatus.

Meanwhile he had been working on the monument, redesigning it to conform to the practical needs of casting. Now it had reached an even grander scale—a colossus that would require two hundred thousand pounds of bronze! He recorded in his notes the very day that this work was started, “On the twenty-third day of April 1490 I commenced this book and recommenced the horse.” The “horse,” of course, was the monument and “this book” referred to still another subject which had grown out of his studies of anatomy and perspective.

The title of the proposed book was to be _Light and Shade_. It would include the subject of optics or the mechanism of the eye, the problems of reflection and refraction and it would lead him eventually to a re-examination of his studies of the sun and moon.

In Leonardo’s day, and even for a long while afterwards, the popular belief of vision was one that had originally been put forth by the Platonic school and expanded by Euclid and Ptolemy. This belief was that the eye sent forth rays that brought back the image to the soul. Leonardo, in his younger days, had believed in the same theory. Not content with what had been written on the subject, however, he began to experiment for himself.

These experiments led him to an examination of the eye itself. He noted the various parts of the eye—the optic foramen or opening, the pigment layer, and the iris. These were already known by the Arabs. Leonardo discovered, however, the crystalline area of the eye. He explained binocular vision, or three-dimensional images, by correctly noting the positions of the two eyes in the head. He described the variations in the diameter of the pupil according to the surrounding light. Further experiments with light brought him to the conclusion that light and images are received by the eye. He took a piece of paper, for example, and pierced it with a small hole. With this he looked at the source of light. He noted the cone shape of the rays funneling into the tiny hole and then when the paper was held next to a white wall he noted that the rays spread out again. He established that light travels in straight lines. He constructed the first “camera obscura”—a box with a small hole in it. Inside the box an object was placed near the hole and behind that a lighted candle. When the box was closed the image of the object was cast on the wall. Leonardo was already acquainted with lenses, and he placed a magnifying lens over the hole to create an enlarged image.

He also demonstrated various laws relative to optical illusion, such as irradiation—when a metal rod is made red-hot at one end, that end seems thicker than the other. A brightly lit object seems larger than one exactly like it that is dimly lit; a dark object placed against a light background seems smaller than it is; a light object seems larger than its real size when placed against a dark background; and the illusion of a light swung in a circle appears as a complete circle of light.

Many years before Newton, Leonardo described the experiment of breaking up a ray of white light into the solar spectrum. Also he compared two sources of light and measured their intensity by the depth of their shadows accompanied by a drawing that was the forerunner of Rumford’s photometer three centuries later! He stated the law of reflection—that is, that the angle of reflection is always equal to the angle of incidence.

About this time Leonardo left the studio of Ambrogio de Predis and moved into the Sforza Castle. Ludovico had put at his disposal a studio in the Corte Vecchia and the use of a room in one of the towers—which Leonardo always kept locked. To his growing list of work, Leonardo now had to add the preparations for the delayed wedding reception of Ludovico’s nephew, Gian Galeazzo Sforza.

On a cold winter evening of January 1490 the guests assembled again. Silks, satins and gold brocade, diamonds, rubies and pearls glittered in the brilliant lights. Princes of the Church mingled with ambassadors of foreign lands. Music and perfume filled the air and as the party quieted down the entertainment began. There were dances in gay costumes. Poetry was recited that flattered the bride and groom. There were allegorical processions. The jokes and antics of the court jester made the audience laugh.

Then, at midnight, the curtain that hung from wall to wall at the end of the ballroom was raised. Applause and cries of delight greeted the spectacle. The rising curtain revealed a room in which there was a hemisphere surrounded by the signs of the zodiac and the planets. While the planets in their niches flickered with concealed lights and the signs of the zodiac glowed, lines were spoken in honor of the house of Sforza to the accompaniment of a choir. The ancient gods swept down from the heavens, and the Virtues and Graces moved across the scene with nymphs waving lanterns. The music drowned out the sound of the mechanism. This was the kind of mechanics that Ludovico could understand and appreciate.

The success of this entertainment so pleased Ludovico that Leonardo was encouraged to present another amusing idea. This one was an “alarm clock” and it utilized what we call today the mechanical relay principle. When a small power is suddenly switched over, the power is reinforced. The “alarm” clock worked by placing a shallow basin of water at one end of a tubed lever. At the other end was another empty basin. Water was led drop by drop into the second basin and as this slowly filled the increasing weight lowered the lever. The shallow basin of water at the first end was suddenly emptied and the immediate switch in weight flipped the lever up and this in turn pushed up the sleeper’s feet.

Leonardo decided to withdraw from the competition for the cathedral dome. Although the cathedral authorities were pleased with his design, they could not decide to whom the commission should be awarded. In the summer of 1490 Ludovico was called upon to settle the issue and he decided in favor of Antonio Amadeo from Milan. But the work that Leonardo had done so impressed Ludovico that he sent him to Pavia in company with an architect from Siena, Francesco di Giorgio Martini, to inspect the work on the cathedral of that city. Leonardo, who had his own workshop and apprentices now, took along one of them, Marco d’Oggionno, a young boy of twenty.

In Pavia one of the greatest libraries in all of Italy was in the ducal palace. Here Leonardo wandered among shelves of books and illuminated manuscripts bound in rich velvets and gold-embossed leather all bound to their places with silver chains. One book that he records in his notes was written in the thirteenth century by Witelo, a Polish scholar, who wrote extensively on perspective. Leonardo, by the necessity of his art, had solved many problems in perspective. He had invented a pair of proportional compasses, the forerunners of those used today for the transfer of a drawing from one scale to duplicate the same drawing in a larger scale. Leonardo had also designed in very careful detail a parabolic compass for drawing a parabola in one continuous movement. He now determined to write his own book on perspective and, as the subject was so close to his studies of the eye, he would entitle it _Introduction to Perspective, or the Function of the Eye_.

Leonardo submitted a number of plans for the completion of the cathedral to the authorities in Pavia and then returned to Milan. He worked through the rest of the summer on the equestrian statue and at the same time he continued to expand his notes on anatomy, light and shade, and perspective.

Late on a cold December night in 1490, Leonardo lit his lamp. This was a very special lamp that he had invented. It had already created a great deal of comment. It was so unusual, he had received an order from the court for another which he made with a richly carved pedestal. Candles, torches, and oil lamps, the only methods of artificial illumination in those days, were poor substitutes for light. They flickered, smoked, went out, and frequently caused damage with their hot drippings. As a side result of his experiments in light, Leonardo had put a glass cylinder in the middle of a larger glass globe. A wick in olive oil was placed in the cylinder and the outside globe was then filled with water. The result was a bright, steady light magnified by the water in the globe.

He sat down by the small fire and arranged his papers in front of him. Then, with a glance at his lamp, he picked up his goose-quill pen and wrote, “No substance can be comprehended without light and shade; light and shade are caused by light.”

7 _Success_

It was January of 1491, and a light snow had fallen in Milan, edging with white all the roofs, the massive spires of the cathedral and the red battlements of the Sforza castle. Soon Ludovico was to be married to Beatrice d’Este of the ducal house of Ferrara.

Once more the streets of Milan echoed to the carpenters’ hammers. Messengers rode to and from the castle and endless carts full of provisions pushed through the crowded city. Guests began to arrive from all the allied courts of Italy with their bodyguards and servants. The rooms of the castle, the palaces of the nobles, and even the inns were filling with the royal processions.

Leonardo was again summoned by the court to prepare the decorations, the costumes for the masquerades, and the arena for the jousting tournaments. An invitation had been sent to all the friendly courts to attend these contests-at-arms. So, accompanying each new party’s arrival was a band of armored knights, their breast-plates, helmets, and shields glistening in the winter sun.

Leonardo enjoyed designing mechanical toys and entertaining the guests with them. One of these was a mechanical drum. Ordinarily most of the entertainment began with normal drum rolls, but Leonardo’s rolls were made on a kind of wheelbarrow. On it was mounted an enormous drum. When the “wheelbarrow” was pushed, it put into motion a cogged wheel geared to the axle. This wheel in turn was geared to two rotary cylinders with pegs mounted around the top. The pegs moved against five drumsticks on either side of the drum and thumped out a rhythm according to the position of the pegs.

Ludovico’s marriage to Beatrice d’Este, a girl of little more than fifteen years, further isolated Leonardo from the court. Being almost a child, Beatrice loved parties and festivities, and she surrounded herself with people who catered to her frivolous whims. As a result so serious a man as Leonardo was forced into the background of the court life. He was called upon more and more to act as stage-designer while his more important work went unnoticed. Because these entertainments were easy for Leonardo to design, they did give him more time to work on his giant equestrian monument of Francesco Sforza. Working one day on the scaffolding surrounding the clay figure of his statue, Leonardo heard a knock at his studio door.

“Come in,” he shouted as he climbed down. “The door’s open.”

Three peasants cautiously entered the room and quickly took off their caps. One of them was holding a carefully wrapped bundle.

“Master Leonardo, we have brought you some shells we found on a ridge of Monferrato. Remember, you asked us to bring anything we found that was unusual?”

“Yes, Pietro. Thank you. Put them here on the table.”

Leonardo opened the bundle. He smiled when he saw the shells. He remembered how, as a young boy, he had found seashells like these high in the mountains. Leonardo questioned Pietro and his companions as to where they had been found and under what circumstances. He gave them some coins and, when they had gone, he looked among his growing collection of notes and drawings on the shelves. It took some time for him to find what he wanted, for the pages were in such confusion. Finally, he sat down at the table with several of the sheets and, putting the seashells in front of him, he began to make notes.

The shells were fossil shells but, thought Leonardo, their presence on the high mountains of Lombardy could hardly be attributed to the great flood as described in the Bible. In his notes, Leonardo cited the case of the cockle which, out of water, is like the snail. It makes a furrow in the sand and can travel in this furrow about three to four yards a day. By such means, he calculated, it could not possibly have reached Monferrato from the Adriatic in forty days (which was supposed to have been the duration of the flood)—a distance of 250 miles. Nor were these simply dead shells deposited by the waves—for the living creatures are recognized by being in pairs, and these in front of him had certainly been traveling in pairs. Consequently, they could have been left there only when they were alive and the mountains were covered by the primeval oceans. Moreover, Leonardo also described how living matter in prehistoric times fell into the mud and died, and how this mud, as the waters receded and years had passed, was changed into rock forming a mold about the fossil—literally making a cast of its original living appearance.

By such deductive reasoning and the testing of the evidence before him against the common beliefs, Leonardo struggled to free the minds of men from medieval superstitions and beliefs. Indeed, these medieval superstitions existed everywhere. Astrologers, or men who told fortunes by the position of the stars at a given moment; and necromancers, those who by tricks of magic claimed to be able to talk to departed spirits—these men profited from the ignorant. The Church, with its preaching of devils and hells, provided the background against which these fakers flourished.

Ludovico Sforza was himself a believer in such things. His own physician and astrologer was a man by the name of Ambrogio da Rosate, who had such influence over the court that he was given a post in the University of Pavia, and his fame was so great that he was called upon to predict the future of Pope Innocent VIII! Leonardo’s dislike of these men was intense. He scorned the supernatural and asked men to look about them at the real world and the real heavens. Observation and experiment—these were Leonardo’s key words. But he was a lonely figure in his thinking—like a man awake while the rest of the world slept.

At last the full-size model of the Sforza monument was nearing completion. Ludovico had ordered it ready for exhibition in the courtyard of the castle for yet another marriage festival that was soon to take place. This time it was the marriage of his niece Bianca Maria to Maximilian I of Germany. Leonardo and his assistants were busy with the finishing touches on the monument, and with building a wagon on which to carry it from the studio to the courtyard.

During these last months Leonardo had had to struggle with all kinds of heavy loads. Already he had improved on pulleys by inventing a new kind of tackle, and he also had utilized many kinds of levers. One of his simpler discoveries for raising heavy weights was a jack which, in appearance and principle, was the forerunner of our own automobile jack.

In 1493 when the clay model of the Sforza monument was completed, it was put on the cart and wheeled to its place of exhibition where a curtain was thrown around it. Again Milan was the host to a gathering of noble courts, and this time Ludovico outdid himself in the display of luxury. Tapestries hung from the buildings and rich carpets were laid down the steps of the cathedral. Everything that Milan had to show was on exhibition—even a crocodile.

But the most impressive sight of all was the unveiling of Leonardo’s colossal statue. It rose in majesty against the red walls of the castle. The name of Leonardo da Vinci was suddenly on everyone’s lips. As the word of his artistic achievement spread from city to city, messages of praise came pouring in. And, for a while the years of frustration and failure to gain recognition melted away. Leonardo at forty-one had at last achieved some success.

Now there was a breathing spell, and Leonardo returned to some of his own projects. For a long time he had continued his observations of his two favorite elements—air and water. To him they were related in their movements. The birds flying in the currents of air and the fish swimming in the flow of water seemed very similar to him. He had already designed various instruments to tell him about the direction of wind and its velocity, and he had also commenced to analyze the wing structure of birds and bats. To soar through the air like a bird was an ancient dream of man, yet for Leonardo it had become a passion. Ceaselessly, he sketched the flights of birds, the flutterings of butterflies and analyzed their flying patterns.

But to Leonardo, understanding the _dynamics_, or motion, of air was the most important thing. He built an _anemoscope_, an instrument like a weather-vane for telling the direction of the wind; and, he also constructed several types of _anemometers_ for measuring the velocity or force of the wind. One of these latter consisted of a thin rectangle of metal hanging straight down in front of an upward-curving wooden arc. This arc was marked off in units of measurement. When the wind blew, it pushed the thin rectangle up the arc; thus, by noting at which gradation it stopped, Leonardo could tell the velocity.

In addition, Leonardo at this time constructed a device which has been compared to the modern instrument used for testing the weight-carrying capacity of airplane wings. He fashioned a wing resembling a bird’s wing and attached it to a lever so that it would be possible to lower the wing by pushing rapidly down on the lever. This wing in turn was mounted on a plank that was in weight equal to that of a human being. He then calculated that two wings of this kind would have to be about twelve meters wide and twelve meters long to raise a man and his machine together. Another device resembling those found in airplanes today that Leonardo constructed was an inclination gauge. He made this by suspending a heavy ball on a cord within a glass bell. This ball was then supposed to guide the flyer by telling him whether he was flying level, diagonally, up, or down.

To Leonardo, water was also a phenomenon that from his youth never failed to excite his curiosity. The use of water power to run machines, to irrigate fields and to carry boats inland was a subject that he never ceased investigating. Out of his experiments at this time he constructed a device for raising water to high levels. It was based on the geometric spiral of Archimedes. He took a piece of gut, inflated it, and let it dry. Then, covering it with a coat of wax to make it waterproof, he wound it around a thin staff in a spiral. He put one end in a stream and attached it by gears to a cogged water wheel; this set the long screw to turning, and he was able to raise water from a low level to any height he desired. With a multiple system of these screws he could raise water in continuous circulation to the reservoirs on the highest towers.

In the year 1494, King Charles VIII of France crossed the Alps at the head of an army of twenty-five thousand men. Now Ludovico, by a series of diplomatic maneuvers, had allied himself with Charles and had, by secret negotiation, actually invited the invasion. By such an alliance he hoped to use Charles’ army to overcome the forces of the Pope which stood in the path of Ludovico’s ambition to become the most powerful ruler in Italy. Outwardly Charles was asserting his rights to the Kingdom of Naples, but inwardly he dreamt of leading a crusade against the infidels in the Holy Land. At the same time young Gian Galeazzo Sforza, Duke of Milan, was dying. Ludovico desired this title for himself; however, until Galeazzo was out of the way, he could not have it. There were ugly rumors that young Sforza had been poisoned. Moreover, in 1494, the Medicis—another powerful obstacle—were expelled from Florence, and a republic was established.

Soon young Gian Galeazzo died, leaving a son, Francesco. This son was the rightful heir to the Dukedom of Milan but Ludovico usurped the boy’s claim and declared himself Duke of Milan. Now Ludovico was in a position to await the impending battle between Charles and the Pope.