Iron wires. The Seguin brothers and suspension bridges in the Grand Duchy of Tuscany and the Kingdom of Sardinia

The French scientific and production scenario played a “foreign enchantment” on the technicians and government staff of the Grand Duchy of Tuscany and the Kingdom of Sardinia, showing the evident influence of the Grande Nation on these countries. In the second half of 1820s these states pushed for the first time in Italy some significant experiments of an innovative type of bridge—the wire-cable suspension bridge—which had been introduced in France, just a few years before, by Marc Seguin. This was one of the prerequisites for the construction of two important bridges over the Arno which were designed and built by the Seguin’s company: the San Leopoldo and San Ferdinando bridges. As for the Kingdom of Sardinia, the fascination for the technological progress beyond the Alps led to the network of relationships that the emerging Savoy entrepreneurship established with French and Swiss companies. This favored in Piedmont the design of first iron wire-cable suspension bridges by the Seguin brothers and the General Dufour. Piedmont’s designs for suspension bridges never materialized, but the three most important bridges—La Caille, Casale, and Turin—were constructed just 15 years later, at the dawn of the 1940s. Through the research of archival sources, the paper aims to retrace the events that accompanied the construction of first wire-cable suspension bridges in Piedmont and Tuscany, to identify the features that characterized their diffusion in these countries and the role that Seguin brothers played both in terms of promotion of the construction typology and technological support.