'Trough' battery, early 19th century.
© Royal Institution / Science & Society Picture Library
Voltaic battery, an improvement on Volta's original 'pile'. The copper-zinc pairs are mounted on separate compartments in a wooden box, forming a horizontal series of 50 pairs. The cells are filled with a solution of common salt, or with dilute acid. This type of battery retained its charge much longer than the original Volta pile type.