Leonardo’s debt to Alberti’s theoretical treatise on painting can be recognized in his own notes and studies for a proposed treatise on the subject. Leonardo wrote notes throughout his life on the subject and one can find scattered in the notebooks sections and lists with subject headings for a treatise. However, these were never compiled into any order, perhaps because Leonardo included such an extensive range of subjects to be mastered by the artist that it became an unworkable task. For example, it is clear why he indicated that perspective should be included in such a treatise but less obvious why he also included the system for the branching of trees.
One of the most fruitful collaborations of Leonardo’s career took place during his time in Milan with the mathematician Fra Luca Pacioli, who arrived in the city in 1496. Their meeting became a catalyst for a flourishing of Leonardo’s interest and development in mathematics. Pacioli’s empirical approach was combined with a Platonic reverence for the mystery of mathematical order. This approach matched perfectly with Leonardo’s own understanding of the underlying order of all things. Their collaboration encouraged Leonardo to investigate far more fundamental studies into the mathematical order that had been a silent basis for so much of his previous art and science. Pacioli praised Leonardo’s work on motion, weights, and forces and referred to a book that Leonardo had written ‘on painting and human motions’. Leonardo illustrated Pacioli’s
De Divina Proportione
, which was originally produced and presented to Galeazzo Sanseverino in 1498 (the illustrated treatise was printed in 1509). The treatise describes the geometry of the five regular or ‘Platonic’ solids and the divine proportion of their construction. These five solids are divine in their construction because they are the only ones that are made up from identical faces and that are symmetrical around their vertices. Leonardo’s ability to render these complex structures in solid and skeletal form is a testament to his grasp of complex spatial structures. Leonardo’s fascination with the abstract nature of mathematics continued to develop and is especially apparent in manuscripts I, M, and the Codex Atlanticus.
Although Leonardo listed sculpture before painting in his job application to Ludovico, we know very little about his work in this medium. In his notes on the
Paragone
, a comparison of the arts in which painting reigned supreme in the visual arts, he spoke disparagingly of sculpture as a messy and dusty enterprise. Debate of this kind was popular in the courts and we know that Leonardo took part in one such debate in February of 1498. Leonardo’s notes on the subject are some of the most comprehensive and sophisticated of any of the topics he wrote about. Sometimes repetitive, they can appear to be practice sessions for public debate and would no doubt have been both engrossing and entertaining. No less entertaining and equally creative were the tales and fables Leonardo wrote. They display a deep and fertile imagination—what he termed
fantasia
. We know from his book lists that he owned chivalric romances, imaginative poetry, and collections of tales, fables, and jests.
Fantasia
was also required for the painter. To succeed, the painter needed to establish a union between the
intelletto
, rational understanding, and
fantasia
, imaginative composition. Only through this combination could an artist remake nature.
We do not know how long Leonardo would have stayed in Milan had the French king Louis XII not invaded. The city was taken over in 1499 and Leonardo left with Pacioli. By March he was in Venice to act as a military adviser to the Venetian Republic which was under threat from a Turkish invasion. Leonardo’s analysis resulted in a proposal to use the River Isonzo as a defence barrier. Numerous sheets were devoted to the study of water and its movement. He was fascinated by its force and the way it behaved, its currents and its destructive potential. He drew parallels between the nature of water and air and he compared curls of hair with vortices of water which was all part of the underlying unity of nature. Leonardo’s work with water would continue at a later date.
When Leonardo returned to Florence by April of 1500 he was 48 years old. He appears to have been housed in the church complex of Santissima Annunziata as a guest of the Servite brothers. He consulted on architectural damage that had taken place on the church of San Salvatore dell’Osservanza (San Francesco al Monte) above Florence and on the construction of a campanile for the church of San Miniato. This ad hoc kind of work was an opportunity for Leonardo to earn some money, and he continued to be employed in this way.
Leonardo’s reputation by now was substantial. He oversaw his own busy studio with an array of assistants and pupils. His working method, as ad hoc as his work, is illuminated in a letter from Fra Pietro da Novellara, the head of the Carmelites in Florence, to Isabella d’Este, the great patron of the arts in Mantua with whom Leonardo had stayed some months before. Isabella had asked Fra Pietro to chase Leonardo to make a painting for her and Fra Pietro’s letters to Isabella give us a revealing look into Leonardo in his studio. He reported to Isabella on 3 April 1501 giving a detailed explanation of Leonardo’s activities including a description of a cartoon Leonardo was doing of the Virgin and Child with St Anne and a lamb, which he describes in great detail, noting the symbolic imagery of the lamb. He notes that Leonardo ‘is hard at work on geometry and has no time for the brush’. He also mentions that ‘the life that Leonardo leads is haphazard and extremely unpredictable, so that he only seems to live from day to day’. Although Leonardo had an established workshop with pupils, it was not apparently being run in a businesslike manner. In another letter written on 14 April Fra Pietro again mentions Leonardo’s distractions with ‘mathematical experiments’ and reports that Leonardo was working on a little picture for ‘one Florimond Robertet, a favourite of the King of France’. Fra Pietro goes on to describe the Robertet painting:
The little picture he is doing is of a Madonna seated as if she were about to spin yarn. The Child has placed his foot on the basket of yarns and has grasped the yarnwinder and gazes attentively at the four spokes that are in the form of a cross. As if desirous of the cross he smiles and holds it firm, and is unwilling to yield it to his Mother who seems to want to take it away from him.
This is a description of the
Madonna of the Yarnwinder
which exists today in two versions (in the collection of the Duke of Buccleuch, Scotland and in another private collection). In his letter Fra Pietro notes the symbolism but also recognizes a new form of emotional dynamism being developed by Leonardo. In other words, Leonardo was taking the devotional subject and giving it an emotional narrative. This kind of narrative in devotional paintings was wholly new, and soon to be taken up by Raphael and Michelangelo. Emotion as a fundamental element of narrative painting was something Leonardo wrote about in his notes for the proposed treatise on painting: ‘That which is included in narrative paintings ought to move those who behold and admire them in the same way as the protagonist of the narrative is moved’ (Urb. 61
v
). The
Madonna of the Yarnwinder
stands in the middle of this revolution in narrative painting and is perhaps one reason why it was copied so often (there are at least thirty surviving versions).
As early as May the following year (1502) Leonardo was occupied in a wholly different way. He entered the service of Cesare Borgia, the head of the papal armies, as ‘architect and general engineer’. Cesare’s ambition was to extend the control of his father, the Borgia pope Alexander VI, throughout the Marches and Romagna. Leonardo was continually on the road travelling to Urbino, Cesena, Pesaro, and Rimini as a result. He studied and consulted on military architecture, field defence, and cartography, drawing maps of Tuscany, Umbria, and the Marches, as well as a bird’s-eye-view map of Imola.
Leonardo was back in Florence by March 1503 and by July he was involved in an ambitious and tactical project of the Florentines to divert the River Arno around their enemy Pisa in order to choke them of their vital access. Looking at the quickly drawn yet fluid maps Leonardo produced, one is reminded of his description of rivers as veins which nourish the earth. The project was never fulfilled and one can imagine Leonardo was not surprised that the great force of the river was not to be diverted. He was fascinated with the potential of nature’s forces and would later (
c
.1515) devote a number of drawings and notes to the cataclysmic possibilities of nature unleashed in a series known as the deluge drawings.
As early as 1506 he was engaged in a deep investigation of the nature of water for the notebook known as the Leicester Codex. Leonardo had planned a treatise on water, which, as with his other proposed treatises, was never completed. In the notebook he outlines a series of titles to encompass water in all its aspects (see pp. 18-19). It is typically Leonardesque in the way he attempts to cover everything. Although it was never finished, it is possible to see that he intended to tackle the subject beginning with hydrodynamics then progressing to the geographical study of the earth’s water system and finally addressing questions of military and civil hydraulic engineering. It is an example of some of the most sustained discussions on a subject produced by Leonardo.
As with his other notes for treatises, the Leicester Codex was written for Leonardo’s own reference. It is more detailed than a notebook of free notations, but less complete than a publishable volume. It provides us with a good example of Leonardo’s writing style. Sometimes it is fragmented, sometimes fluent, and at other times rapid or abrupt. Abbreviations are common, as are spelling errors. Leonardo realizes that further work is needed on some areas and so he writes notes to himself on where to expand: ‘Here I shall continue and discuss a little the location of waters, although it seems somewhat out of order, and then put them in order in their places when drawing up the work’ (Leic. 25
v
).
Following the Renaissance Platonic format of a dialogue, Leonardo applies it to technical and scientific subjects. On one side is Leonardo, the scientist who bases his knowledge on experience and on the other side is what Leonardo calls the ‘adversary’, whose beliefs are based on book learning and authoritative texts of the day. Leonardo takes pleasure in gaining debating points through demonstrations of the facts of nature.
One of the challenges Leonardo set himself was the possibility of man achieving flight. This would be the greatest engineering achievement of all. Leonardo spent a great deal of time studying the flight of birds and the possibility of man flying, or as he eventually realized, gliding. In the early 1490s, when he was still in Milan, his notebooks show he was working on a flying machine, which he drew suspended from his studio ceiling and noted a plan to test the machine secretly. He returned to this ambition in Florence when he began the notes now known as the Codex on the Flight of Birds (Turin, Biblioteca Reale). This notebook is his most sustained analysis of the dynamics of bird flight. In understanding the mechanisms and dynamics of flight Leonardo turned to a study of the workings of the human body in an example of comparative anatomy. This study confirmed to him some essential analogies between man and bird in the mechanisms of the bones, tendons, and muscles. Amongst the sketches of soaring birds, there is a reference to the testing of a flying machine at Mount Ceceri (named after the soaring birds found in the area) above Fiesole. He predicted that the success of his experiment would fill the ‘universe with awe’ and bring ‘eternal glory’ to the man who created it. We do not know if the test was ever carried out, as no notes survive that refer to it, successful or not.
Leonardo’s interest in human anatomy was intense. His earlier approaches had been strongly influenced by Mondino de’ Luzzi (
c
.1270-
c
.1326), Galen, the ancient Greek medical writer, and Avicenna, the great Arab philosopher and physician. These were the standard influences during the Renaissance. Leonardo had continued his investigations and in the winter of 1508 he was in Florence where he dissected the corpse of a 100-year-old man (the ‘centenarian’) in the hospital of Santa Maria Nuova. Leonardo wrote a touching description of the old man lying in his hospital bed and gently dying. He then could not help but find out the ‘cause of so sweet a death’ and carried out a dissection of the body. The reason, he discovered, was ‘from the lack of blood for the artery that nourishes the heart and the other parts below it, which I found very dry, thin and withered’ (W. 19027
v
). This appears to be the first description of arteriosclerosis.
Although Leonardo would come to realize that Galen was fundamentally wrong in many of his anatomical depictions, he did share Galen’s awe of nature’s design, ‘the wonderful skill of the creator’ (
On the Function of Parts
, 14. 2. 295) and belief that ‘Nature does nothing in vain . . . the artifice of nature is worked out in every part’ (
Anatomical Procedures
, 2. 2). This idea that everything in nature had a purpose was the underlying basis for Leonardo’s anatomical investigations. It was the structure of the anatomy that would reveal how it worked. Leonardo would take his work in anatomy to its highest level with his later studies of the heart in Rome (
c
.1513-14). These studies are a wonderful example of Leonardo’s ability to take his most developed knowledge of another subject, in this case hydrodynamics, and apply it to his study of blood flow in the heart. Leonardo had studied the cause and behaviour of vortices of water forming in rivers. Looking at the shape of the heart, he worked out that vortices of blood occurred when passing through the valve as the heart pumped, and these vortices in turn caused the valve to shut before the next flow of blood occurred.