Brunelleschis Dome (22 page)

Only a few days after the cupola was consecrated, the Opera had announced yet another competition, calling for models of machines “for hauling loads up on the great cupola.” Filippo, as usual, rose to the challenge. After building a model for a new hoist, he was promptly granted the commission along with a prize of 100 florins, the same amount with which he had been rewarded for his design for the ox-hoist many years earlier. Work on this new machine began in the summer of 1442 and was completed the following year.

This new hoist was later sketched by Lorenzo Ghiberti’s grandson Buonaccorso. A slightly less complex machine than the ox-hoist, it is nevertheless ingenious in design, featuring multiple pulleys, a counterweight, and a braking system. Buonaccorso’s sketch includes a text written in cipher, albeit a fairly crude one. His code (known as the “Caesar Alphabet” because of the fact that Julius Caesar reputedly invented it) simply replaces each letter in the alphabet with the one that precedes it: B with A, D with C, and so forth. Once decrypted, the text describes the operations of the machine’s various parts. In keeping with his nature, Filippo had probably also attempted to guard the secrets of the hoist, especially after his experience with Antonio di Ciaccheri.

The most interesting of the hoist’s features was its braking system. Since the men powering the hoist would clearly not have the strength and endurance of the oxen that had driven Filippo’s earlier hoist, it was necessary to design a system whereby both the load and counterweight could be suspended in midair if necessary. The vertical gear was therefore fitted with a ratchet wheel and a pawl that allowed the load to be locked into position. The gears were also much smaller than those in the ox-hoist, entailing a slower ascent for each payload.

Work on the lantern was delayed because of a familiar problem: the difficulty of acquiring sufficient quantities of
bianchi marmi
. Quarries were examined near Campiglia as well as at Carrara, but the former proved inadequate because the town of Campiglia failed to provide Filippo’s masons with working facilities. In the end, marble did not begin arriving from Carrara until the summer of 1443. It was brought to Florence by sea, river, and road. Fifteen years after the wreck of
Il Badalone
, Filippo, now sixty-six, appears to have washed his hands of this particular problem, and it was left to Antonio di Ciaccheri to design and build a special cart to carry the marble from Signa to Florence. But Filippo did ensure that, once on the building site, the blocks of marble were protected from the bumps and scrapes of the new hoist by special wooden coverings.

Buonaccorso Ghiberti’s sketch of Filippo’s lantern hoist.

Over the next few years the Piazza del Duomo became so crowded with these blocks of marble — some of which weighed more than 5,000 pounds — that the people of Florence became alarmed at the thought of them stacked on the top of the cupola. Surely it was tempting fate to burden it with so massive a weight? Filippo dismissed these fears, claiming that, far from causing the dome to collapse, the lantern would actually strengthen it by acting as a common keystone for each of the four arches comprising the vault.

Once the blocks of marble had been hoisted to the top of the cupola, they needed to be laid in their places, an operation requiring yet another machine. Construction of a crane for this purpose was begun in 1445. Some 20 feet high and 20 feet wide, this apparatus could not have been raised through the oculus, which was less than 19 feet in diameter; it therefore had to be constructed at the top of the cupola. Walnut logs, pine beams, and bronze pins used to build the crane were all winched into the air and then assembled at the dome’s summit. Although built under the direction of Antonio di Ciaccheri, who was making himself more and more indispensable to the Opera, the crane was, like all of the other machines used on the dome, the product of Filippo’s ingenuity.

As the lantern took shape, it became clear that it was an aesthetic triumph. Most later lanterns, including the one built for St. Peter’s in Rome, would be based on its style. But it also left a more unexpected legacy.

Architectural marvels like Filippo’s dome often become sites of scientific inquiry because their unique structures and dimensions can serve as testing grounds for new theories and technologies. Galileo would drop cannonballs from the Leaning Tower of Pisa in order to provide an ocular demonstration that all falling bodies descend with equal velocity independent of weight. Hundreds of years later Gustave Eiffel studied aerodynamics from the top of his tower (where wind speeds can reach well over 100 miles per hour) and ultimately proved that the suction over the upper surface of an airplane’s wing is more important to its flying ability than the air pressure beneath. The dome of Santa Maria del Fiore likewise aided scientific study, only in this case the knowledge gained was used for transport not through the air but, rather, across the ocean.

Paolo Toscanelli was one of the greatest mathematicians and astronomers of the century. It appears that he met Filippo in about 1425, and he would later call his friendship with the
capomaestro
the greatest association of his life. Like Filippo, Toscanelli was a lifelong bachelor and an unlovely physical specimen, with thick lips, a hooked nose, and a weak chin. Although a wealthy man, he forsook all luxury and lived like a monk, sleeping on a wooden plank beside his worktable and following a vegetarian diet. He had trained as a physician in Padua but spent most of his time gazing at the heavens and performing complex mathematical calculations. He instructed Filippo in the geometry of Euclid, and later the
capomaestro
would repay the favor, albeit unwittingly, by assisting him with his celestial observations. For in 1475, inspired by the height of the dome, Toscanelli climbed to the top and, with the blessing of the Opera del Duomo, placed a bronze plate at the base of the lantern. This was designed so that the rays of the sun would pass through an aperture in its center and fall some 300 feet to a special gauge on the floor of the cathedral, a stone inlaid in the Chapel of the Cross. Santa Maria del Fiore was thus transformed into a giant sundial.

This instrument would prove vital to the history of astronomy. The height and stability of the dome allowed Toscanelli to gain a superior knowledge of what were then thought to be the sun’s motions (only generally accepted as the earth’s orbit around the sun in the seventeenth century), which in turn enabled him to calculate with a much greater accuracy than anyone previously the exact moment of both the summer solstice and the vernal equinox. These calculations served an ecclesiastical purpose in that religious dates such as Easter could be carefully regulated, but they also had more far-reaching applications.

After Prince Henry the Navigator founded his school for mariners at Sagres in 1419, the Portuguese had undertaken a number of voyages of discovery in the eastern Atlantic, using a new type of vessel called the caravel, a light, swift ship designed to sail into the wind. The fruits of these voyages were manifold. Portuguese navigators sponsored by Prince Henry had explored the two remotest islands in the Azores (first discovered in 1427) and traced much of the coast of West Africa. The Cape Verde archipelago was sighted off the coast of Africa in 1456, and fifteen years later Portuguese sailors crossed the equator for the first time. But larger prizes still lurked over the horizon. Islands such as Brasil, Antillia, and Zacton all existed in legend, but no one had yet set eyes on them. The latter of these islands was said to be especially rich in spices.

These voyages into the Atlantic could not have been made without the aid of astronomy, which permitted mariners to navigate uncharted waters and then make maps of their discoveries. Navigation in a relatively small body of water like the Mediterranean was done by means of charts showing a scale of distances and a pattern of twelve rhumb lines (later expanded to sixteen) that radiated from a central point known as the wind rose. The navigator would simply trace a line between two points, then find the corresponding rhumb line — one running north-northeast, for example — and shape his course from it with the help of a magnetic compass. Questions of longitude and latitude could safely be ignored. But when Portuguese seamen ventured south into the uncharted waters along the west coast of Africa, they discovered that this simple method was no longer applicable. The great age of celestial navigation was about to begin.

Crucial to this type of navigation was the astrolabe, an instrument that astronomers used to calculate the position of the sun and other stars with respect to the horizon. By the middle of the 1400s it was being used by mariners to calculate their positions on the ocean. As astronomical determinations of longitude were unreliable, accurate readings of north-south distances — determinations of latitude — were of great importance in both navigation and mapmaking. Mariners calculated their latitude by using the astrolabe to take angle sights on the Pole Star, measuring the angle between its direction overhead and the horizon. As they sailed closer to the equator, however, the Pole Star sank lower in the sky, and this method became impractical. The sun was therefore used instead, the astrolabe measuring its angle above the horizon at midday.

This determination was a simple enough operation except for the fact that the position of the sun, like that of the Pole Star, does not coincide with the celestial pole. In other words, neither of these guides to celestial navigation lies directly on the imaginary extension of the earth’s axis from the North Pole. In order to obtain the latitude of an area, it was therefore necessary to apply a correction to their observed altitudes. A number of tables of declination already compiled by astronomers were used for this purpose, most notably the Alfonsine tables, which had been prepared by Jewish astronomers in Spain in 1252. These tables enabled astronomers and navigators to calculate the positions of the sun and the Pole Star throughout the various seasons, as well as lunar or solar eclipses and the coordinates of any of the planets at any given moment. Two centuries after they were compiled, these tables still contained various inaccuracies and were in need of revision. Toscanelli’s observations of the motions of the sun — observations made with the help of the brass plate at the top of Santa Maria del Fiore — led him to correct and refine the Alfonsine tables, and in doing so he put in the hands of mariners and mapmakers a more accurate tool for plotting their positions.

Toscanelli himself had a particular interest in maps and explorations. In 1459 he interviewed a number of Portuguese sailors familiar with India and the west coast of Africa so that he could create a new and more accurate map of the world. This map then seems to have given rise, in Toscanelli’s acute mind, to a novel and striking idea. Fifteen years later, when he was seventy-seven years old, he wrote to a friend in Lisbon, Fernão Martines, a canon at the court of King Afonso of Portugal. He urged Martines to interest Afonso in a sea route to India, assuring him that the Atlantic Ocean was the shortest road to the spice regions of the Orient — a shorter road, that is, than the overland passage normally taken by merchants. Such a route was now necessary because parts of the overland route to India had been closed to Europeans after the Turks captured Constantinople in 1453. Toscanelli therefore appears to have been the first person in history to entertain the idea of sailing west in order to reach India.

King Afonso could not be persuaded to adopt Toscanelli’s plan. Although the nephew of Henry the Navigator, he was more interested in slaughtering Moors than discovering new islands in the middle of the ocean. But seven years later the astronomer was contacted by a relative of Fernão Martines: an ambitious and high-strung Genoese sea captain named Christopher Columbus. An expert navigator, Columbus had sailed all over the known world, from Greece to Iceland to the Gold Coast of Africa. On his voyage to Africa he had spotted flotsam on the current — the trunks of pine trees, large canes, other pieces of wood — that convinced him of the existence to the west of further unknown lands. When he returned to Portugal, he had seen Toscanelli’s letter to Martines, which so inspired him that he copied it into the flyleaf of one of his books, a treatise on geography that would later accompany him on all four of his voyages to the New World.

Toscanelli wrote back to Columbus, repeating his convictions about the sea route to India. He even sent Columbus a map in which the distance to China was optimistically calculated as being only 6,500 miles — a gross underestimation, of course, but a figure that gave hope to Columbus, in whose mind the map and the letter found fertile soil. However, Columbus had no better luck than Toscanelli in persuading the Portuguese to undertake the venture, and so in 1486 he petitioned for an audience with representatives of King Ferdinand and Queen Isabella of Spain. The rest, of course, is history. Six years later, on August 3, 1492, after funds had been raised and promises of various honors and titles made to Columbus, the tiny fleet of three ships set sail from Cape Palos, near Cartagena, in the hour before dawn. And although Columbus would later claim, with typical arrogance, that neither maps nor mathematics had been of any use to him, it is to be wondered if Europeans would have landed in the New World quite so early and so easily without the maps and tables that Paolo Toscanelli compiled with the help of his observations taken from the dome of Santa Maria del Fiore.