March 20, 1800

Voltaic pile

Volta dates his letter announcing the electric pile to the Royal Society

Volta compared his invention to a weak Leyden-jar battery that mysteriously recharged itself after every shock.

20 March 1800: a letter dated at Como

At Como on 20 March 1800, Alessandro Volta dated a French-language letter to Joseph Banks, president of the Royal Society, announcing results from his experiments with different conducting substances and asking Banks to communicate them to the Society.

He described an apparatus built by repeatedly pairing silver or copper with zinc or tin, the pairs separated by disks of porous material moistened with salt water. He also described a related chain, or crown, of cups.

About twenty stages, a spark, and a shock

Volta explained that roughly 20 repeated metal stages could produce an electrometer reading, a spark, and shocks when a person touched the two ends. He presented the device as resembling a weakly charged Leyden-jar battery, differing in that it could act repeatedly without an external recharge.

His explanation of why it worked did not survive. Volta held that metal-to-metal contact generated the electricity and treated the wet layers chiefly as conductors; modern electrochemistry attributes the sustained current to oxidation and reduction reactions involving the electrolyte.

London got the news in pieces

The date belongs to the letter, not to any lecture or meeting. The communication travelled to London in separate portions, and Banks passed on enough of it for Anthony Carlisle and William Nicholson to build a pile by late April and use it to decompose water in early May.

The Royal Society's archive records the letter as read on 26 June 1800. It then appeared in Philosophical Transactions, pages 403–431, with a folding plate.

Sources

Researched 23 Aug 2026 9 sources 2 audit passes

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

What the sources leave uncertain

March 20 is securely documented as the date written on the letter at Como. It was not the date of a lecture, Royal Society presentation or journal publication.
Accounts indicate that the letter traveled to London in separate portions, so its exact receipt history is more complicated than a single March 20 delivery.