Leyden jar, early 19th century.
© Science Museum / Science & Society Picture Library
Leyden jars were invented by E G von Kleist in 1745. They are devices for storing static electricity, and consist of two conductors separated by an insulator. This Leyden jar has a tinfoil coating both internally and externally. There is a bras ball conductor on a bras rod which extends through the mahogany lid and joins eight wires which are twisted together to form a cage.