Ayrton's improved gold leaf electroscope, 1890.
© Science Museum / Science & Society Picture Library
The first electroscope was devised by Abraham Bennet in 1786. This improved version was developed by William Ayrton (1847-1908), who was responsible for inventing numerous prototypes of modern electrical measuring instruments. Gold leaf electroscopes are used to indicate and measure small electric charges. They usually consist of two gold leaves which diverge because of the repulsion of like charges.