Electrical machine, c.1762
Demonstrations of electrical effects became more common after the invention around 1747 of the Leiden jar. The jar stored electric charge, and so allowed more impressive demonstrations. This version of an electrical machine was made by George Adams around 1762. The glass cylinder is turned using the handle so that it rubs against a fabric-covered pad and causes a charge to build up. The charge can be conducted away from the brass back plate of the pad and used to make sparks.
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