In March 1800, Alessandro Volta wrote to the president of the Royal Society describing a device made of stacked discs of two different metals separated by cardboard soaked in brine. Connected at both ends, it produced a steady electric current for as long as the chemicals lasted.
Nothing like it had existed. Within six weeks of the letter being read in London, two English chemists had used a copy of the apparatus to split water into hydrogen and oxygen. Within eight years, another had used a much bigger one to isolate six chemical elements nobody had ever seen.
The pile came out of a quarrel about frogs.
Galvani’s Frogs
Luigi Galvani was professor of anatomy at Bologna, and through the 1780s he investigated the effect of electricity on muscle. Dissected frog legs were his standard preparation, and he found that they twitched when an electrical machine was discharged nearby, and even when no machine was operating at all.
The observation that mattered came when he hung the prepared legs from a brass hook on an iron railing. Whenever the leg touched the iron while hanging from the brass, it contracted. No external source of electricity was involved.
Galvani published his conclusions in 1791. The muscle and nerve, he argued, contain their own electrical fluid, stored much as a Leyden jar stores a charge, and the metal arc simply provides a path allowing it to discharge. He called it animal electricity, and it implied that living tissue is fundamentally electrical.
The claim caused a sensation across Europe, and inspired a good deal of speculation about the electrical nature of life itself, some of it ending up in Mary Shelley’s novel a generation later.
Volta’s Objection
Alessandro Volta, professor of experimental physics at Pavia, repeated the experiments and initially accepted the interpretation. Then he noticed a pattern that Galvani had recorded without emphasising.
The contractions were strongest when the arc consisted of two different metals. With a single metal, the effect was weak or absent.
Volta drew the opposite conclusion. The electricity is not coming from the frog. It is generated at the junction of two dissimilar metals, and the frog’s leg is simply an extraordinarily sensitive detector of it, better than any instrument then available.
He tested the idea on himself, placing a strip of tin on his tongue and a silver coin further back and connecting the two. The result was a distinct sour taste, produced by nothing but two metals and saliva. There is no dead animal in that experiment.
The dispute ran from 1792 until Galvani’s death in 1798 and was conducted, by the standards of scientific controversy, with reasonable civility. Galvani’s decisive counter, performed by his nephew Giovanni Aldini, was to produce contractions using no metal at all, by touching a cut nerve directly to a muscle.
Both men were right. Volta was right that a pile of dissimilar metals generates current without any biological component. Galvani was right that living tissue produces genuine electrical activity, which is what nerve impulses are. Emil du Bois-Reymond demonstrated it conclusively in the 1840s, and electrophysiology became a discipline. The English word galvanise preserves the loser’s name.
The Pile
To prove his case, Volta needed to produce electricity from metals alone, in quantity, with no animal tissue anywhere near it.
He stacked discs in a repeating sequence: zinc, then copper or silver, then a layer of cardboard or leather soaked in brine, then zinc again, and so on, sometimes to a height of thirty or forty repetitions. Each pair of metals contributes a small potential difference, and stacking them adds the contributions together.
He also built a variant he called the crown of cups, a row of bowls of salt solution with a zinc strip and a copper strip in each, connected in series. It works on the same principle and is easier to see into.
The letter describing both, dated 20 March 1800 and addressed to Sir Joseph Banks, was read to the Royal Society in June and printed in the Philosophical Transactions.
Why It Changed Everything
Before the pile, electricity meant static electricity. Machines generated charge by friction and Leyden jars stored it, and the result was a violent discharge lasting a tiny fraction of a second. Franklin’s kite experiments and the entire eighteenth century tradition of electrical demonstration worked with these sudden discharges.
You can study sparks with them. You cannot study what a current does over time, because there is no current, only an instant of transfer.
The pile provided the first continuous, controllable source of electric current in history, and it turned electricity from a spectacle into a laboratory tool. The consequences followed immediately.
- May 1800. William Nicholson and Anthony Carlisle, having read a copy of Volta’s letter before publication, built a pile and passed its current through water. Hydrogen collected at one wire and oxygen at the other, in a two to one volume ratio. Electrolysis, and with it the entire field of electrochemistry, dates from that experiment
- 1807 and 1808. Humphry Davy at the Royal Institution built a battery of some two thousand plates and used it to decompose substances that no chemical reagent could break down. He isolated potassium, sodium, calcium, magnesium, strontium and barium, discovering six elements in about eighteen months
- 1820. Hans Christian Ørsted, lecturing in Copenhagen, noticed that a compass needle deflected when placed near a wire carrying current from a pile. Electricity and magnetism were connected. This discovery is impossible without a steady current, and it opened the field that Ampère, Faraday and Maxwell would spend the century developing
- 1831. Faraday’s work on induction, and his laws of electrolysis, both rest on apparatus powered by piles
The Mechanism Volta Denied
There is a final irony in the story. Volta insisted throughout his life that the electricity was produced by the mere contact of dissimilar metals, and that the moist layer was only there to conduct.
He was wrong. The current comes from chemical reactions at the electrodes: the zinc is oxidised and dissolves, and a reduction reaction occurs at the other metal. The brine is not a passive conductor but a reactant, which is why a battery runs down and why the zinc discs corrode.
The chemical theory was argued for by Davy and Faraday and was settled well before the end of the century. Volta had built the first battery and never accepted the correct explanation of how it worked.
The Man and the Unit
Volta was born in Como in 1745 and worked there and at Pavia. Before the pile he had invented the electrophorus, a device for generating and transferring static charge, and had isolated and studied methane after noticing gas bubbling out of marsh sediments in the lake near his home.
Napoleon summoned him to Paris in 1801 for a demonstration, made him a count in 1810 and a senator of the Kingdom of Italy. He retired to Como and died in 1827.
In 1881, an international congress in Paris named the unit of electrical potential the volt in his honour, which is why the specification on the back of every electrical device carries his name. The pile itself belongs among the instruments that changed what humans could see, since a steady current is what made electrochemistry and the discovery of new elements possible.
The century that followed turned his laboratory curiosity into infrastructure. By the 1890s the argument had moved on to how electricity should be distributed rather than how to produce it, which is the subject of the war of the currents, and the high frequency experiments recorded in Tesla’s own account of his work would have been unthinkable without a reliable source of current to start from.
What the Quarrel Produced
The Galvani and Volta dispute is a useful case because the standard framing, one man right and one man wrong, does not fit it.
Galvani observed a real phenomenon and gave it an explanation that was correct in one context and wrong in the one he was actually testing. Volta identified the error, and in constructing an apparatus to demonstrate it, built something far more consequential than the point he was trying to prove.
He set out to show that frogs were not necessary. He ended up giving chemistry its most powerful tool and physics its route into electromagnetism.
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