Councilors and Tribunal of Venice. This resembled a turtle’s shell with
a raised bump on the center which was the “periscope.” When submerged
the water probably rose to an area just around the “periscope,” but,
again, the information about its air-supply is missing and the only
reference to it is a reminder to close the “l—.” In addition, he
invented a system of screws mounted in tongs with the borer in the
middle for putting holes in the bottoms of enemy ships, and at the same
time he thought of a defense against such an attack by designing the
defending vessels with double hulls.
Among Leonardo’s other maritime devices were designs for boats that
could dredge canals, harbors, and lagoons. What was the result of all
these plans? We do not know. Whether any one of them was used against
the Turks is a mystery.
At any rate, Leonardo and Pacioli left Venice that same spring and
arrived in Florence in April of 1500. One of the purposes of Leonardo’s
journey was to visit his father who was now living on Via Ghibellina
with his fourth wife. Leonardo was now forty-eight. Still tall and
straight with the strength of his youth, his face prematurely aged and
his hair thinning back from his high forehead, Leonardo was more than
ever an outstanding looking man. He still scorned fashionable clothes
and dressed according to his own comfort which made him even more
noticeable among the crowd. His deep-set eyes with their direct and
penetrating glance, framed by his full, reddish beard, never missed a
thing, although he now wore spectacles at his work.
Now that he was back in Florence, Leonardo needed lodgings and a job. He
had banked his small savings, and he did not want to touch that. His
father’s house with the five children of his present wife plus the sons
from his previous marriages was too full to accommodate Leonardo.
Moreover, the relationship between Piero and Leonardo was polite but
distant, as Piero preferred the children of his later marriages.
Luckily, the place to live and the commission Leonardo needed presented
themselves at the same time. The Church of the Annunciation of the
Servite Order of Monks needed an altarpiece, and, as Leonardo’s fame was
great, they offered him and his apprentice quarters in the monastery.
Here, in the solitude of a monastic cell, Leonardo was able to return to
his own researches. His long association with Fra Luca Pacioli continued
as they worked together on Pacioli’s edition of Euclid’s _Elements_. At
the same time, with his absorption in geometry, Leonardo commenced his
studies of the transformation of solids; that is, changing the shape of
something to another shape without diminishing or increasing its
substance.
In his preoccupation with geometry, Leonardo had apparently done little
about the commission which the Servite monks had given him. He finally
yielded to their complaints, however, and commenced to draw the
preliminary study for the subject, which was “St. Anne with the Virgin
and Child.” Again his knowledge of geometry is most apparent in the
finely constructed composition, every gesture of which is as plotted as
a geometric exercise. In April of 1501, the drawing was finished; it
caused an immediate sensation throughout Florence. For two days the
public was allowed to pass in front of it.
But now a change was taking place in Leonardo. He was no longer content
with simply painting. His highly original researches for pictures had
slowly grown to the point where the research was more important than
painting. In a sense the scientist had taken the brush from the artist.
In two letters from Isabella d’Este’s emissary in Florence we learn, “He
is entirely wrapped up in geometry and has no patience for painting.”
This excerpt from a letter dated April 8, 1501, was followed six days
later by another which said in part, “In brief, his mathematical
experiments have made painting so distasteful to him that he cannot even
bear to take up a brush.”
A few months after the completion of the St. Anne drawing, Leonardo
received a letter signed by Cesare Borgia, Duke of Valentinois. Leonardo
frowned and thought back to his last days in Milan. When King Louis XII
of France had entered the city, he had summoned the painter of the “Last
Supper” to an audience. The king had been generous in his praise and had
tried to persuade Leonardo to remain. At that same audience had also
been Cesare Borgia, an ally of the French. Leonardo remembered the man
now—the dark hair and eyes, the black, arched eyebrows, and the face
marked by some old disease. He was a powerful-chested, thin-hipped man
who had originally been made a cardinal by his father, Pope Alexander
VI. But the attractions of secular power soon persuaded him to abandon
this title. With the enthusiastic help of his father, Borgia had fought,
murdered, and deceived his way to a formidable position of authority in
these last years. Leonardo, in the seclusion of the monastery, had
lately heard that Borgia’s army had even been at the gates of Florence.
The letter addressed to Leonardo was an offer to assume the post of
Architect and Military Engineer to His Excellency, Cesare Borgia. He
thought of Ludovico Sforza—defeated and captured at the battle of Novara
just a year ago as he attempted to regain his dukedom. Now the duke was
a prisoner at Loches in Touraine; Leonardo had written of him, “The duke
lost his State, his personal possessions and his liberty, and none of
his enterprises have been completed.” And Leonardo also thought of his
equestrian monument still standing in the castle being used for target
practice by the French archers. Like the duke, nothing of his own had
been completed either. Perhaps this Borgia offer was an opportunity.
Leonardo decided to accept it.
In May of 1502, after having presented himself to Cesare Borgia in Rome,
Leonardo began his hectic travels through Tuscany and Umbria. He was to
inspect the fortresses and cities of Cesare’s new conquests there, and
to make whatever recommendations he felt necessary for their
improvements. Arriving in Piombino, he at once set down a project for
draining the marshes and reclaiming the land. Also, while he was here,
he spent hours by the sea watching the waves curl in from the Adriatic
and studying the crash of water over the beaches. Moving on to Arrezzo,
he drew up the first in a series of remarkable maps for the army of
Vitellozzo which, with the backing of Cesare Borgia, was marching
against Florence. These maps are bird’s-eye views of Tuscany and Umbria,
and somewhat resemble modern aerial photographs. Drawn from Leonardo’s
own observations, the green mountains stand, according to their height,
in relief, with the roads winding over them and down through the
valleys. The streams and their tributaries are in blue and even the
villages and cities are drawn with great exactitude. Indeed Leonardo had
learned his lessons from old Toscanelli well, and he was one of the
first to bring the art of cartography to such perfection.
In July and August Leonardo was in Urbino and Pesaro, and by the 8th of
August he had reached Rimini. Here he strengthened the fortifications
and then rode quickly on to Cesena. Between Cesena, capital of the
Romagna, and Porto Cesanatico, he spent from the middle of August to
September planning a canal between the two, redesigning government
buildings, and drawing up a new quarter to be built for the city of
Cesena. At this time he constructed an instrument for telling him the
speed of water currents in a stream. It told him whether the flow was
swifter at the surface or at the bottom or on one side or the other of
the stream’s bed.
In the meantime, Florence, alarmed at the growing power of Cesare
Borgia, appealed to Charles d’Amboise, Regent of Milan for France, to
come to her aid. Charles responded in the absence of the French King and
helped to protect Florence. The enemies of Cesare took advantage of this
to form an alliance, and soon Cesare was being forced back from his
newly won possessions. Cesare himself then hastened to Milan, and there
he suddenly came face to face again with Louis, the King of France, who
was on his way to Naples. Borgia, who could exert great charm and
influence when he wished, persuaded the king that, all rumors to the
contrary, he, Cesare, was fighting the enemies of France. Again he won
over the French, which greatly strengthened his position. Then, from
Pavia, he issued a decree placing every facility possible at Leonardo’s
disposal. In addition, he instructed all officials to help Leonardo in
every matter, referring to him as “our highly esteemed court architect.”
While Leonardo was in Porto Cesanatico, a delegation from Bayzid II,
Sultan of Turkey, paid a visit to Cesare Borgia. Among other things the
delegation was looking for an engineer to build a bridge between
Constantinople and Pera to replace a temporary wooden structure.
Leonardo designed for them a single-arched bridge with double ramps at
either end (looking very much like a present-day “thruway” entrance). He
provided that it should be approximately twelve hundred feet long,
eighty feet wide, and one hundred and forty feet above the water.
[Illustration: _Da Vinci’s proposed bridge from Constantinople
(Istanbul) to Pera. Looking very much like a modern “thruway”
entrance, it was to have double ramps on both sides._]
In his travels through the countryside, Leonardo could not help but
notice how primitive the mills were. Feeling how strongly the wind blew
in from the sea, he designed a windmill with a roof that turned with the
sails. For the mechanism inside he devised a band brake—a semicircle of
wood into which the large cogwheel of the mill was forced. This mill
resembles the “Dutch” mills of the Netherlands and was among the first
of its type to be brought into existence.
In the fall Leonardo was at Imola. There he created another of his
beautifully rendered maps. He drew this with the help of a magnetic
compass of his own invention. It consisted of a board with an arc on it
and a compass needle, and was probably the first magnetic needle on a
horizontal axis. This time the map was of the city itself, the walls,
the castle and the principal buildings all touched with color and the
river winding through the fields. Drawn in the shape of a circle, it
resembles a view through a telescope from directly above. In Imola, too,
he met Niccolò Machiavelli, the famous historian and political
scientist, who was an emissary from the Signoria, the Council which now
governed Florence. These two men became friends and, later,
collaborators in Leonardo’s scheme to make the Arno river navigable to
the sea.
At this time Cesare Borgia, having achieved great success in his
military campaigns and confident of his conquests, decided to return to
Rome. With the disbanding of Borgia’s headquarters at Imola, Leonardo’s
duties were finished. Together with his new friend Niccolò Machiavelli
and two other Florentines, he left Imola and the service of Cesare
Borgia to return to Florence.
In January of 1503, a mathematician named Giovanni Battista Danti
attempted a flight in a machine that he had designed. This flight was
part of the entertainment at a wedding reception in Perugia. Danti
climbed into his apparatus on top of the tower of St. Mary of the
Virgin. It was pushed off into the air, hovered a few seconds, then
began slowly drifting toward the ground. But suddenly, one of its wings
hit a building projection and it crashed. Danti was carried away with a
broken leg.
The news of the event traveled quickly to Florence.
When Leonardo heard about it, he eagerly questioned all those who had
either seen it or had heard it described first hand. Danti’s attempted
flight excited Leonardo for now he realized that he was no longer alone
in his search. With a sense of urgency he returned to the problems of
flying. He felt now that the solution to flight might be in the swift
gusts of air through the ravines and the spread wings of the eagle
drifting high in the sky.
10
_Shattered Hopes_
Before Leonardo could return to the problem of flight, however, he was
again faced with the necessity of supporting himself and his growing
household. The small fees he received for taking on apprentices hardly
covered the cost of housing and feeding them. Moreover, the equipment he
had to buy for his scientific researches added further to his strained
budget. So, when a servant from Francesco del Giocondo, a rich
Florentine merchant, presented himself at the gate with the request that
Leonardo accept a commission to paint Francesco’s wife, Leonardo was
only too glad to accept. The name of Francesco’s wife was Madonna Lisa,
or Mona Lisa for short. Leonardo painted her portrait on and off for the
next three years. Thus, what started as a minor commission ended as the
one painting—in addition to the “Last Supper”—that most people today
associate with the name of Leonardo da Vinci.
Having secured this work, Leonardo turned back to his studies of birds
in flight and the nature of air. The soaring wings of eagles and hawks
and the way they rode the currents with hardly a dip of their spread
wings guided Leonardo’s thinking from pure mechanics to machines that
act more on the principle of the glider. He proposed to write a treatise
on the nature of birds’ flight, and, with his usual thoroughness, he
began to weigh, dissect, and reconstruct various types of birds and
their wing structure. He realized that one of the main difficulties of
gliding was maintaining balance, or, more accurately, maintaining the
center of gravity. From previous observations Leonardo had noted that
man is capable of making the same motions that a bird does. He had also
measured the strength of a man’s legs and had calculated that man has
twice the power in his leg muscles that he needs for standing.
Consequently he began to redesign his machine making use of man’s arms
and legs to operate or “flap” the wings instead of standing him on a
platform.
The first of Leonardo’s new designs was a sort of harness apparatus
strapped across the shoulders of the flyer who was supposed to be able
to keep himself balanced by moving the lower part of his body. He could
manipulate the flight by handles that were connected to the flexible,
outer parts of the wings. These wings were designed from the webbed
wings of the bat. Surprisingly enough, this device closely resembled the
experimental gliders used by Otto Lilienthal almost four centuries later
in Germany.
Leonardo was now approaching other solutions to pure flight when further
hostilities interrupted his work. Florence and Pisa were in bitter
rivalry, and their struggle had assumed the proportions of a major war.
The Florentine army was now practically at the gates of Pisa. Niccolò
Machiavelli urged the Signoria to enlist the help of Leonardo da Vinci,
who might be able to think of an immediate plan for destroying Pisa and
her army. Never one to think in terms of an immediate battle or a
temporary success, Leonardo put forth a daring and sweeping plan that
would forever reduce the power of Pisa. The plan was as simple as it was
monumental—divert the Arno river from its course into two canals that
would empty into the sea at Leghorn south of Pisa. In this way, Pisa
would lose her water supply and her opening to the sea.
The plan met with immediate approval and by the end of July 1503,
Leonardo was sent out to survey the entire course of the river. He was
accompanied by Giovanni “the Piper,” a man who was frequently employed
on minor engineering projects and who was the official player of the
pipes to the city of Florence. Giovanni was also the father of Benvenuto
Cellini, who became the most famous goldsmith of the Renaissance. As
they made their way to Pisa, Leonardo made some more of his
extraordinary maps of the area, paying particular attention to the
course of the Arno and its tributaries. These maps later inspired him to
plan a whole series showing the main watersheds of Italy.
When he rode into the Florentine camp drawn up before Pisa, Leonardo
designed from his observations and maps, a dam on the Arno to regulate
the course of the river. This bird’s-eye view map is a marvel of
exactness. It shows the flow of the river hitting the dam with its
swirling backwash and overflow. Leonardo’s knowledge of the movement of
water was so great and his craftsmanship in drawing so fine that the
water in this map seems to flow before one’s eyes. One of the main
problems in regulating the Arno was its tendency to continually be
shifting its bed by the deposits of new sediment, and Leonardo realized
it would be a long time before this project could be completed.
When he returned to Florence he presented to the Signoria, as part of
his survey, various machines to hasten the excavation of the Arno. He
had designed a crane that would assist in the digging out of two
different levels at the same time. He also submitted the results of his
calculations on the saving of muscular energy by the use of such
machines. In addition, Leonardo proposed to use the water in the canals
for irrigation purposes and had even calculated what the volume and
velocity of a jet of water would be if projected from an opening in the
bottom of the canal wall into an irrigation ditch. As if this were not
enough, he had invented a practical method of piling as a foundation for
the lock-basins to protect them against the dangers of erosion.
A separate map of this period on the flow of rivers in general was
intended to relate to his treatise on the nature of water. In this
treatise is the first outline of the fundamental principles of
hydrodynamics, as for example:
The velocity of a current increases with the slope and decreases with
the winding of the riverbed.
The volume of a river is in proportion to the width of its bed, the
slope and the depth of the water being equal.
The slope and width being equal, the speed of the current is greatest in
the deepest part of the river.
The excavation force increases at the narrowest section of the river.
Because of the grumbling of the military commanders at what they
considered a waste of time, Machiavelli had to intervene with the
Signoria before Leonardo was sent out again with documents of authority
to continue with his plans. He spent well into the fall surveying the
Arno and in October he was back in Florence.
Meanwhile the fighting between Pisa and Florence had been lessened by
two political changes. In August Pope Alexander VI had died and his son
Cesare Borgia became seriously ill. The Republic of Florence was now
free of its most dangerous enemies—the Borgias. The city relaxed in its
new security and the hostilities between Florence and Pisa died down to
an uneasy armed watch.
Leonardo quickly took advantage of the situation to present an early
dream of his to the Signoria. He again put forth his idea of a
commercial canal to the sea and made mention of the great advantages
there would be for all the mills, lumber yards, forges and other
commercial interests in utilizing the water power that would be
available from his project. Piero Soderini, the governor of the
city-state of Florence, was impressed and thought of the glory it would
bring to Florence and himself. He told Leonardo he would present it to
the Signoria.
Leonardo now plunged into a winter of great activity. Forced to draw
from his savings, he had rejoined the guild of painters in October of
1503, and then applied for the commission of painting the murals in the
council chamber of the Palace of the Signoria. It had been planned to
decorate this great hall with scenes commemorating famous Florentine
victories, and Leonardo chose the battle of Anghiari where the soldiers
of Florence defeated the Milanese in 1440. In addition to working on the
“Mona Lisa” and continuing with the canal project—for which he was now
designing great suction pumps to lift rivers from one level to
another—he turned again to astronomy and geology.
Leonardo, while investigating the course of the upper Arno, had come
across much evidence that the land there had at one time been completely
under water. Various types of ancient ocean life and vegetation lay
scattered in layers along the ridges of the mountains, and these
Leonardo collected and brought back to his studio. He wrote, “above the
plains of Italy where now birds fly in flocks, fishes were wont to
wander in large shoals.” He reread Ptolemy, the ancient Greek geographer
Strabo, and even Sir John Mandeville, an English author of travel books,
in his quest for knowledge of distant places. He talked to travelers,
sailors, and wrote to friends to send him information about the
countries they had seen or lived in. Strabo, in particular, had set
forth the doctrine that the earth’s transformation had taken place by
the forces of volcanoes and water, but the wisdom of these early men had
been obscured by the closed minds of the Middle Ages.
Even in his own time of reawakening knowledge—the Renaissance—Leonardo
had to contend with the combined superstition of the Church and the
ignorance of misguided scholars. For example, the Church believed in the
great flood, as described in the Bible, and the scholars claimed that if
what Leonardo said were true—that the earth was the result of an
evolutionary process—there would have been written records. To this
latter Leonardo responded, “... sufficient for us is the testimony of
things produced in the salt waters and now found again in the high
mountains far from the seas.” But Leonardo’s conception of the evolution
of the earth was mistaken in one respect. He regarded the earth as
organic—living—and the flow of water he believed to be like the flow of
blood in man. Indeed, according to Leonardo, all living creatures were
reflections of a living, breathing earth. It was only when he again
turned his eyes inquiringly toward the moon and the laws of the universe
that he began to realize his error.
It had been the idea that the earth was the center of the universe which
supported Leonardo’s theory of an organic earth. Yet after years of
observation and study he abandoned this theory and, with the eye of a
man centuries ahead of his time, he wrote in his notes, “The moon has
every month a winter and a summer. And it has greater colds and greater
heats and its equinoxes are colder than ours.” He went further and
identified the elements existing on the moon such as “water, air, and
fire,” and described them and their functions as being like those on our
own earth. In so doing he recognized the existence of the moon as a
solid in space, reflecting the light of the sun—one of many “stars” in a
universe. With his acceptance of this concept he realized that the earth
could not be organic.
In May of 1504, the Signoria complained to Leonardo that there had been
no progress on the proposed paintings for their council chamber, even
though he had already been partially paid for them. Accordingly, he was
forced to sign a document that he must be finished by February of next
year or refund all monies paid him. As was his custom he had made many
preliminary drawings. Although he was well acquainted with horses he had
again researched their anatomy and actions. Pages of rearing, frightened
horses and men in combat covered his studio tables. On one of these
pages there are sketches of the heads of a lion, some horses and a
man—all with fierce expressions on their faces. Here Leonardo hinted at
the comparative anatomy of expression in man and animal that Darwin was
to write about almost four hundred years later.