People from ancient times knew that rubbing certain materials and then touching something caused a spark. Studying what is called electrostatics laid the groundwork for understanding electricity and magnetism. Natural philosophers, scientists, and instrument makers created many ingenious devices to generate electrostatic charges starting in the 1600s. These machines varied in size and technique but all involved rotary motion to generate a charge, and a means of transferring the charge to a storage device for use.
For many years electrostatic machines like this one from Case Institute of Technology were considered essential tools for teaching the basic concepts of electrical science and saw significant use. Though in poor condition, this machine shows the basic components of a typical 19th century cylinder generator. The cylinder is set in wooden hubs and was turned by a direct-drive crank. Shards of material loose inside the cylinder may be remnants of the shellac used to hold the cylinder to the hubs. The leather rubbing pad with cloth flap provided the friction that generated the static charge. A mount post set opposite the rubbing pad held the missing metal collector that gathered the charge for experimental use.
During the 1750s electrical researchers refined the design of electrostatic machines by replacing earlier spherical globes with a glass cylinder, a design used for many years. This change increased the surface area of the glass in contact with the rubbing pad and improved the efficiency of the generator. There are no extant makers marks so we are unable to determine the exact age or origin of this machine.
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