The Dome of Brunelleschi and the curse of lightning: a story lasting four centuries
Attracted by the Golden Ball of Verrocchio, dozens of electrical jolts rained down on the Cathedral. Many of these events were recorded in documents, from viewpoints both scientific and superstitious.
Since ancient times, lightning, that very strong electrical discharge produced during storms, has evoked both fear and fascination. The Dome of Florence Cathedral, built by Filippo Brunelleschi between 1420 and 1436, is one of the symbols of Western architecture, well known for its majesty, grandeur and solidity. Yet that character has not been enough to protect it from the devastating electrical phenomena inherent to thunderstorms. Drawn by the enormous amount of copper in the globe placed on the Duomo lantern in 1471, by Andrea del Verrocchio, and counting until 1859, at least 27 significant strikes hit the apex of the Cathedral of Santa Maria del Fiore. In 1859, finally, the first lightning rod was installed, bringing a halt to the devastating electrical rain. Among the strikes recorded, the ones of 1492 and 1601 were the most consequential.
In his Memories, Tribaldo De’ Rossi recounts the events of 5 April 1492:
"When we were in bed and it was three in the morning, small granules of hail began to fall, with a great wind. A terrible thunderbolt came, and everyone was frightened. In the morning it was seen that it had hit the Lantern of Santa Maria del Fiore, which is on the Cupola, and it had brought down more than a third of the Lantern. It fell on the church in many parts, piercing the vault of the church in five places."
Some 120 years later, in 1604, Francesco Bocchi wrote to his colleague Filippo Valori, recalling the ruin of the lantern some years earlier, during a storm on the night of 26 January 1601. "Soon after the fourth hour of night, while terrible conditions persisted, suddenly there broke out a rain mixed with hail accompanied by wind, and in an instant, struck by a bolt of lightning, the tallest pyramid [the cupola lantern] ripped open on one side, with a frightening cleft. The surrounding neighbourhood was awakened by the terrifying roar… and, not without reason, as it seemed that the sky was burning, people feared the destruction of the city of Florence... Thrice, and almost at the same moment, the part of it named for resemblance to a lantern was struck with a terrible roar, and under such violence, huge marbles suddenly shifted from their places, and falling in various parts of the church, miserably deformed the building underlying."
The event recorded by Valori was the most violently damaging ever to occur for the dome. The strike of that night caused the detachment of Verrocchio's copper ball, weighing 1.9 tonnes, the fall of which damaged the lantern below, whose marble pieces tumbled down the slopes of the dome, landing on the vaults of the left lateral nave and the cornice of the northwest tribune. Fortunately, no harm was recorded to persons, but some of the stone landed on buildings and streets nearby, exploding on impact, such that pieces were found as far away as Via de’ Servi.
Anonimous florentine: Il fulmine colpisce la lanterna. Oxford, Ashmolean Museum, n. cat. 770.
The impression of this event on contemporaries is testified not only by the many written memories, but also in iconographic ones. Among these, an anonymous drawing preserved by the Oxford Ashmolean Museum shows a deity, probably Jupiter, God of Thunder, hurling lightning at the lantern, and the dome in the very moment of shattering. This same image also catalogues the shape and number of fallen elements, including the cross and ball of Verrocchio. A second elegant drawing, this one by Alessandro Allori and preserved in the National Library of Florence, captures a moment soon after the cataclysm. In this image the lantern emerges terribly torn, but already clearly subject to careful observation and the first interventions of preservation: a support in brick can be made out, erected in aid of the damaged structure. The restoration was complex, requiring two years of work and the very substantial cost of 16,291 scudi. Allori himself, in a report of the times, noted that "what has been done new agrees and unites very well with the old…”, an assertion which, through our own analysis, we can still confirm today, and demonstrating that even then there was particular attention to correctly preserving the historical-artistic heritage of Florence. The Grand Duke and the officers of the Opera of the Duomo had indeed directed the architects chosen, Giulio Parigi and Gherardo Mechini, "not to renew or change anything of the ancient model."
Alessandro Allori: View of the damaged lantern. Biblioteca Nazionale Centrale di Firenze, II.I 429, c. 33r.
In memory of the tragic event, the famous marble disk - still sought out by tourists and visitors - was placed where the ball had fallen.
The human perceptions raised by such impetuous natural phenomena were rooted in ancient times, and descended in popular traditions and beliefs, among which myths and legends, and because of this the lightning strikes on the Cathedral were also interpreted in prophetic and supernatural key, as omens and signs of misfortune. The strike of 1492, for example, was taken as a harbinger of the death of Lorenzo the Magnificent, occurring only three days later.
Documenting these views, we have the summary report of Ferdinando Del Migliore, published some 200 years later: "On the 5th of April in 1492, there came a [lightning bolt] that, as Giannotti reported, ruined a large part of the Pergamena [cupola lantern], and this was also an omen of future misfortunes, as commented by Amaddio Nicolucci, when he came to the city for the death of Lorenzo de' Medici the Elder.”
Similarly, after the lightning strike of 1601, Grand Duke Ferdinand I asked Pope Clement VIII for a number of relics to be placed in two lead boxes inside the arms of the cross, on the sphere returned to the lantern crown, to prevent further incidents. The aim was to establish a kind of "celestial shield" in protection of the entire cathedral. As Del Migliore, once again writing in the 1600s, lamented, "It truly seems that the sky itself is scornful of such heights [of the cupola of Santa Maria del Fiore], and instructs us of this through experience, by the lightning and thunder that very often strike it…; occult causes, not understood by us, beat and strike the tops of our tallest buildings."
Indeed, the causes of the repeating electrical phenomena were clarified by Benjamin Franklin in the mid-1700s, and with continued scientific progress, in 1859, the order went out for installation of a lightning rod on the Cathedral of Florence: a turning point for the safety of the monument. The new defensive system was very severely tested some years later, in June 1885, as recorded in an extraordinary first-person report preserved in the Cathedral archives:
“In the very fierce storm which prevailed over Florence on the 19th of this June, among the various lightning strikes that fell in different parts of the city, there was one that discharged on the lightning rod of our cathedral dome. That bolt of lightning, in fact, fell on the tip of the electrical conductor that rises from the summit of the cross, situated on the copper sphere of the cupola. And myself and others distinctly saw that dazzling streak of fire, which in the moment enveloped the conductor and even melted the platinum tip in an amount of 15 millimetres. The lightning then discharged into the two ground wells where the conductors terminate, and did not cause any damage to that distinguished structure [Cathedral dome and Lantern]."
Chronology of known lightning strikes:
- 1859: First lightning rod Installed.
Marble disk in memory of the lightning strike of 1601