How it began
Alessandro Volta invented the voltaic pile in 1799. He reported his experiments in a two-part letter, written in French and dated 20 March 1800, to Joseph Banks, president of the Royal Society in London. The letter was published in the Society's Philosophical Transactions in 1800 under the title On the Electricity excited by the mere Contact of conducting Substances of different kinds.
Before it existed
The pile came out of a professional disagreement between Volta and Luigi Galvani. Galvani had argued, from experiments on frogs, for a form of animal electricity. Volta built his electric pile to disprove that idea and to show that the contact of different conducting substances was the source of the electricity.
How it works
The pile consists of alternating discs of copper and zinc, with pieces of cardboard soaked in brine between them. Stacked in this way, the discs produced a steady electric current, unlike earlier sources of electricity. The pile is credited as one of the first electrochemical cells, and understanding of the reactions inside it has changed since Volta's time.
What changed first
The continuous current led quickly to discoveries in electrochemistry. These included electrolysis and the isolation of several chemical elements by scientists such as William Nicholson and Humphry Davy. The voltaic pile powered the electrical work of the 19th century until generators became available. Modern batteries are built on the same principles.
