An electroscope is made to establish an electric charge. Its working is based on the repulsion of similar charges. An electric charge applied at the top will spread over the conductor, which causes two thin gold leaves at the inside of the electroscope to move apart. This type, mainly intended for atmospheric electricity, was first described in 1887 by the Austrian natural scientist Franz Exner. Characteristic are the two sideward rods with which two protection plates can be pushed against the gold leaves at the inside. This makes the apparatus easy to transport. This specimen, made by Jilles van Waveren (Teylers Museum's own instrument maker), can be sucked vacuum with an air pump to prevent leaking of charge through the air.
Gold leaf electroscope
pre 1859