Museo Galileo
Virtual Museum
Drum electrical machine
    • Setting:
      Room XI
    • Maker:
    • Date:
      ca. 1776
    • Materials:
      mahogany, velvet, glass, iron, brass
    • Dimensions:
      total height 1200 mm, drum 540x660
    • Inventory:
    • Drum electrical machine (Inv. 3408)
    • Drum electrical machine (Inv. 3408)

This is probably the only large drum electrical machine extant. The drum consists of two mahogany disks connected by an internal frame covered in red velvet. It is rotated by a simple crank. The base is made up of a large wooden box with lid to store the accessories. The large cushion with chamois leather cover is supported by two flexible wooden strips secured to two solid glass rods that insulate the cushion from the base. The flexible wooden strips allow the cushion to follow the uneven contour of the drum. The brass knob at the back of the cushion is for the grounding chain, or it can be connected to a conductor to receive negative charges.

Little is known about this remarkable machine, formerly in the Lorraine collections and described in the inventory of the Museo di Fisica e Storia Naturale of 1776. Its frictional design was obviously inspired by Edward Nairne's two large generators in the Museum collection. Although glass was the most popular material for electrical machines, other substances were also tried.