Room XI—the logical continuation of Room V—showcases important instruments made for the astronomical observatory of the Museo di Fisica e Storia Naturale of Florence (the "Specola") and the Arcetri Observatory. They illustrate the changes that took place in the eighteenth and nineteenth centuries in the design, construction, and scientific use of telescopes. These are impressive, complex machines, with ingenious steering systems. By contrast with Room V, reflecting telescopes outnumber refracting telescopes here. There is a burning lens, a gift from Benedetto Bregans to Cosimo III de' Medici. It was used in 1814 by Humphrey Davy for his research on the chemical nature of diamonds. Also worth noting are the high-quality telescopes built by Giovan Battista Amici, director of the Specola.