Voltaic pile. Part of a large voltaic pile made by Sir Humphrey Davy in 1808. Seen here is a trough containing 50 zinc plates. These would have been filled with dilute sulphuric acid. A copper plate would have been clipped to each zinc plate, the whole forming an electrochemical cell. Five of these cells made the 'great battery' with which Davy isolated several metals from their salts by electrolysis, discovering potassium, sodium, calcium, magnesium, boron and barium. This artefact is preserved at the Royal Institution, London.