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 Princeton were considered essential tools for teaching the basic concepts of electrical science and saw significant use. This table model is unmarked and of fairly crude workmanship. The wood frame holds a glass cylinder turned by a direct-drive crank although the handle is missing. Wooden hubs hold the cylinder in the frame. No rubbing pad or charge collector remain on this unit. 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.
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