Room XV presents an important collection of air pumps and hydraulic devices. After Torricelli's famous experiment in 1644, air pumps were among the most important instruments available to natural philosophers. They were used with a series of accessories for performing a wide range of experiments in a vacuum. Among the oldest and more interesting are those described, toward the mid-eighteenth century, by the French abbot Jean-Antoine Nollet and by the Dutchman Willem Jacob 's Gravesande. Others dating from the early nineteenth century remained in use—at least for teaching purposes—until the early twentieth century. Hydraulics is represented by many demonstrational devices such as the Archimedean screw, hydraulic pumps, and fountains of various kinds, which—like the model attributed to Hero—were invariably included in the scientific cabinets of the eighteenth and nineteenth century. A particularly curious apparatus is Carlo Castelli's pump, used in the early nineteenth century, of which this is one of the very few surviving copies.