Alesandro Volta's letter to the Royal Society, 20 March 1800.
© Science Museum / Science & Society Picture Library
Count Alesandro Giuseppe Anastasio Volta (1745-1827) wrote a letter to Sir Joseph Banks of the Royal Society of London which contained a U-shaped voltaic pile, an early battery and the first source of current electricity. It consisted of two different metals, separated by chemicals in order to enable a flow of electricity. Volta developed the theory of current electricity and the electric decomposition of water, and his name is given to the SI (international standard) unit of electrical potential, the volt (V).