Volta's crown of cups. Devised in 1800 by Alessandro Volta, inventor of the electric battery, this instrument consists of nine glasses which can be arranged in a horseshoe shape on a black-painted tinplate tray. Forked conductors, with one side zinc and the other copper, fit between each pair of glasses but do not touch inside the glasses. Single strips of zinc and copper are placed in the end glasses to form terminals. When the glasses were filled with water, or preferably brine, a potential difference was set up between the terminals.