Enlightening Towers: Public Opinion, Local Authorities, and the Reformation of Meteorology in Eighteenth Century Italy
Bertucci, Paola, Transactions of the American Philosophical Society
IN THE SPRING OF 1777 Piazza del Campo at Siena became the site of a collective experiment. One year earlier the Grand Duke of Tuscany, Pietro Leopoldo, ordered that a lightning rod be affixed to the tower of the town hall, the very heart and symbol of the city. His decision prompted the heated reaction of a Siena nobleman, the marquis Alessandro Chigi, who published an attack against the theory that lightning was an electrical phenomenon, claiming that metallic conductors would be ineffective in preventing damages to building and people during thunderstorms.1 Chigi's opposition to lightning rods found quite a few supporters, and when, on April 18, 1777, black clouds darkened the sky above Piazza del Campo, a large crowd gathered in the square to observe the effects of the conductor erected on top of the tower. They saw a bolt of lightning strike the tower and be conducted safely into the ground, channeled by the metallic rod. The professor of physics at the University of Siena, Domenico Bartaloni, examined the tower and the conductor after the storm. Although "the incredulous" expected "a completely different result, almost wishing to see the tower flashing, so as to expose to ridicule the holy laws of physics," Bartaloni declared the complete success of the conductor in protecting the tower. His official report was published in the transactions of the Academy of Siena as well as in the local newspaper. The collective witnessing of the experiment sanctioned the success of lightning rods in the public sphere.2
The Siena episode highlights typical elements that characterized eighteenth century debates on the effectiveness of lightning rods: the involvement of public opinion, the role of local authorities, the experts' engagement in the popularization of their views, and the spectacularly visible setting of the experiments. Towers were main protagonists of the early history of lightning rods. Highly tangible symbols of political, religious, or financial power, towers had always been frequent targets for the fiery meteor of lightning. From the mid-eighteenth century, they became favorite sites for experimenting with lightning conductors. Not only in Siena but also in Florence, Pisa, Milan, Turin, Venice, Genoa, Bologna as well as in smaller towns south of the Alps, natural philosophers affixed metallic conductors on top of the towers of churches, city halls, castles, and palazzi.' In the philosophers' opinion, the pointed conductors would slowly draw the electric fire from tJiunderclouds and channel it into die ground, thereby preventing huge discharges that would damage buildings. Or, they would attract lightning, forcing it to pass through the metal, with the same result. Yet because of their visibility and symbolic significance in the everyday life of Italian cities, towers also became highly debated experimental sites that attracted the inhabitants' attention and made the debate over lightning rods a public concern.
This essay shows that before lightning rods became marketable commodities, they were experimental devices used to substantiate or criticize Franklin s theory of electricity, which held that the matter of lightning and that of artificially produced electric sparks were one and the same. The study of the nature of lightning contributed to the reformation of Aristotelian meteorology in terms of die new science of electricity: each flash of lightning that struck a metallic conductor created the experimental setting for electricians to study the behavioT of such a disruptive natural "meteor." The reports of their observations made up a sort of transnational repository of experimental results on which lightning rods advocates relied to support dieir arguments. Because of their unusually visible setting, however, such experiments acquired a public dimension that obliged electrical experimenters to confront public opinion and local authorities. In some cases, this confrontation brought electricians to engage in campaigns of popularization of electrical science, which aimed at highlighting the public benefits deriving from the installation of lightning rods and from the study of electrical meteorology. …