As early as 600BC it was found that rubbing a piece of amber created a build-up of charge which could attract small pieces of straw. Around 1600 AD the word 'electric' was introduced to describe this effect derived from the Greek word for amber, elektron. Benjamin Franklin demonstrated the electrical origin of lightning in 1745 with his kite-flying experiments during thunderstorms. He suggested the existence of two different charges: positive and negative. In 1800 Alessandro Volta generated a constant electrical current by placing layers of copper and zinc in a saline (salt) solution. His 'Voltaic pile' was the first battery. The next breakthrough was in 1820 when Andre-Marie Ampere established a relationship between electricity and magnetism. The final crucial step was the discovery of electromagnetic induction, in 1831, by Michael Faraday who managed to convert magnetism into electricity by moving a magnet through a coil of wire. This led the way for the development of electrical generators and in 1881 the first public electricity supply was introduced in Godalming in Surrey for street lighting.