By Rafe Calder
The Leyden jar is named for a Dutch city. Whether it was invented there is a matter on which the sources disagree. This piece sets out what three of them say, in the order of the dates they give.
What the thing is
Wikipedia calls the Leyden jar an early electrical storage device and the original form of the capacitor. It holds a high-voltage charge between conductors on the inside and outside of a glass jar. Britannica describes it as a device for storing static electricity and as a prototype of the capacitors used in radios, televisions and other equipment.
How it is built
Both sources describe two stages. The earliest form was a partly water-filled glass vial or bottle closed with a cork, with a wire or nail through the cork dipping into the water. Wikipedia says the experimenter’s hand acted as the outer conductor in those early versions. Britannica says the exposed wire was touched to a friction device to charge it.
The later form, according to Wikipedia, is a glass jar with metal foil on the inner and outer surfaces, the foil stopping short of the rim to prevent arcing, and a metal rod through a non-conductive stopper joined to the inner foil, usually by a hanging chain. Britannica’s present form is much the same: an insulating jar with foil on the inside and outside, the outer coating connected to earth and the inner one to a central brass rod that projects from the mouth.
Wikipedia says the inner electrode is charged from an electrostatic generator while the outer foil is grounded, so that the two surfaces hold equal and opposite charges.
Who gets the credit
Wikipedia and Britannica both say the German cleric Ewald Georg von Kleist developed it independently in 1745, using a bottle with a nail in the cork, and that Pieter van Musschenbroek at the University of Leiden investigated it in 1746.
Britannica gives a shorter version: Kleist developed it independently in 1745, and Musschenbroek, a Dutch physicist at the University of Leiden, discovered it accidentally and investigated it in 1746. Britannica does not mention Cunaeus.
Credit for the invention is disputed between Kleist and the Leiden experimenters.
The name
Wikipedia says the Abbé Jean-Antoine Nollet, who sold Musschenbroek’s instruments in France, gave the device the name Leyden jar and promoted it. It lists the alternative names Leiden jar and Kleistian jar. The Musschenbroek article also says Nollet named it. Britannica says only that the device is linked to the University of Leiden, where Musschenbroek worked. The name therefore points to the place where the experiment became widely known and not, on this evidence, to the first discovery.
Dates in order
- 1745: Kleist develops the device independently, according to Wikipedia and Britannica.
- 1746: Musschenbroek investigates it in Leiden, according to Britannica.
Questions a buyer would ask
Is a jar sold today a Leyden jar? The sources describe a design, a glass jar lined inside and out with foil and fitted with a rod, and not a trademark. How old is an old one? These pages do not date any object, and a specialist or a museum is the right route.
Quick answers
- Who invented the Leyden jar? Credit is disputed. Britannica says Kleist developed it independently in 1745 and Musschenbroek investigated it in Leiden in 1746.
- Why is it called a Leyden jar? Wikipedia says the Abbé Nollet gave it the name and promoted it. Britannica ties the device to the University of Leiden.
- What was the first jar made of? Both Wikipedia and Britannica describe a partly water-filled glass bottle with a nail or wire through a cork.
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