On the Electricity Excited by the Mere Contact of Conducting Substances of Different Kinds
Stack cells of two metals and brine and, for the first time, electricity flows without end.
For two thousand years electricity had been a spark you could make but never keep. Volta found how to make it flow — and keep flowing.
The big idea
Take two different metals and a cloth soaked in salt water. Where each metal meets the wet cloth, a tiny push on electric charge appears. One such sandwich gives a push too small to notice. But stack the sandwiches — zinc, silver, wet cloth, zinc, silver, wet cloth — all facing the same way, and the little pushes add up. Thirty or forty of them, and you have a steady current strong enough to feel, to spark, to do work. Volta had built the first battery.
The quarrel that built it
It began with a dead frog. In the 1780s the anatomist Luigi Galvani found that a frog’s leg twitched when touched by two different metals, and concluded that animals carry their own “animal electricity.” Volta, a physicist in Como, was fascinated — then sceptical. He suspected the real source was the pair of metals, not the frog.
To prove it, Volta did away with the animal entirely. He replaced the frog with wet cardboard and stacked metal discs until the pile itself gave the shock no frog had ever needed. In March 1800 he wrote it all up in a letter to Sir Joseph Banks, head of the Royal Society in London. The battery was born out of a decade-long argument between two stubborn, brilliant men — and, it turned out, both were partly right.
Why it mattered
A current that lasts is a current you can use. Within weeks, others used Volta’s pile to pull water apart into hydrogen and oxygen, and soon to break open “elements” and discover new ones — chemistry now had electricity as a scalpel. Every battery since, from a torch to an electric car, is the same idea: cells in a row, their voltages adding. We even measure that push in “volts,” named for him.
Like a flight of stairs
Think of one cell as a single low step — too small to matter on its own. A pile is a staircase: each step lifts the charge a little higher, and the whole flight lifts it a long way. The more steps you stack, the higher the climb — which is exactly why more cells mean more volts. A 1.5-volt AA battery is a very short staircase; the pack in an electric car is a tall one, hundreds of steps high.
Where it sits
Volta’s pile is the source the rest of electrical science needed. It let Ørsted and Ampère find the link between current and magnetism, let Ohm (1827) state how current, voltage and resistance relate, and let Faraday (1831) turn magnetism back into electricity. Galvani’s side of the argument — that living tissue makes its own electricity — was vindicated too, and runs through to the Hodgkin–Huxley model of the nerve impulse (1952) in this Library.
Thirty, forty, sixty, or more pieces of copper, or rather silver, applied each to a piece of tin, or zinc, which is much better, and as many strata of water, or any other liquid which may be a better conductor, such as salt water, ley, &c., or pieces of pasteboard, skin, &c., well soaked in these liquids; such strata interposed between every pair or combination of two different metals in an alternate series, and always in the same order of these three kinds of conductors, are all that is necessary for constituting my new instrument…