Leyden Jar (1745): The First Device to Store Electricity

The Leyden jar, invented independently in 1745 and 1746 in Germany and the Netherlands, was the first device able to store a substantial electric charge and release it at will. Named after the Dutch university town of Leiden, it gave eighteenth-century scientists a powerful new tool and produced shocks strong enough to astonish the public. It is the direct ancestor of the capacitor found in electronic circuits today.

Background: electricity before the jar

In the early eighteenth century electricity was studied with friction machines: spinning glass globes or tubes rubbed by a hand or a pad. They could make sparks and attract light objects, but the charge leaked away quickly into the air.

Researchers such as Stephen Gray in England and Charles du Fay in France had shown that some materials conduct electricity while others insulate it, and that there seemed to be two kinds of electrical effect. Several experimenters wondered whether charge could be “bottled” in water inside a glass container.

Two independent discoveries

The first known success came from Ewald Georg von Kleist, a Lutheran cleric and dean of the cathedral chapter at Kammin (now Kamień Pomorski, Poland). On 11 October 1745 he charged a medicine bottle containing a nail and found that touching the nail gave a powerful shock. His letters describing the effect were not clear enough for others to repeat it easily.

In Leiden, the physicist Pieter van Musschenbroek and his circle, including Jean-Nicolas-Sébastien Allamand and Andreas Cunaeus, made the same discovery around the turn of 1746. Cunaeus, a lawyer who assisted with experiments, held a glass of water in one hand while it was charged from a machine, then touched the wire with the other and received a violent shock.

On 20 January 1746 Musschenbroek wrote to the French scientist René-Antoine Ferchault de Réaumur describing the experience. He said, in a well-known passage, that he had thought his life was over and would not take another such shock for the whole kingdom of France. The letter was read to the Paris Academy of Sciences, and Jean-Antoine Nollet named the device the “Leyden bottle”.

How it works

A Leyden jar is a glass container with conducting material on both sides of the glass. Early jars held water; within a few years experimenters such as William Watson and John Bevis in England lined the jar inside and out with metal foil, which worked better. A metal rod or chain through the stopper touched the inner coating.

When the inner coating is connected to a friction machine, it gathers charge, and the outer coating, held in the hand or connected to the ground, gains an equal and opposite charge. The glass keeps the two charges apart. When a conductor, including a human body, bridges the two coatings, the stored charge equalises in a single spark.

In Philadelphia, Benjamin Franklin showed in the late 1740s that the charge was bound to the glass rather than to the water or metal. He took a charged jar apart, handled the coatings, reassembled it and found it still charged.

Spectacle and experiment

The jar spread through Europe within months. Nollet staged famous demonstrations in 1746, discharging jars through a chain of 180 royal guards in the presence of Louis XV and through a long line of Carthusian monks in Paris, all of whom jumped at the same instant. Accounts of the number of monks vary, with around 200 most often cited.

Travelling lecturers used jars to kill small animals, light alcohol and give paying audiences shocks. The Danzig physicist Daniel Gralath linked several jars together in 1746 to increase the force, and Benjamin Franklin later called such groups a “battery”. During his kite experiment of 1752, Franklin used a Leyden jar to collect charge drawn from a thundercloud.

Legacy

For half a century the Leyden jar was the main way of storing electricity and measuring its effects. Large batteries of jars were used by researchers including Joseph Priestley and Henry Cavendish, and physicians tried electric shocks as therapy.

The jar could only release its charge in one burst. A steady current became possible only with Volta’s pile in 1800, which followed debates sparked by Galvani’s work on animal electricity. Leyden jars nevertheless remained in use in laboratories, early radio transmitters and teaching demonstrations into the twentieth century, and their principle survives in the modern capacitor.

Myths and facts

Myth: Musschenbroek alone invented the Leyden jar. Kleist reached the same result a few months earlier, and in Leiden the first shock was received by Cunaeus. Musschenbroek’s role was to report it to the wider scientific world.

Myth: the jar stores electricity in the water. Franklin’s experiments showed that the glass, not the water, was essential: the opposite charges gather on its two faces and the glass keeps them apart. Water simply served as a convenient conductor until metal foil replaced it.

Timeline

• 1745, 11 October: Ewald Georg von Kleist records the shock from a charged bottle.
• 1746, January: Cunaeus and Musschenbroek obtain the same effect in Leiden.
• 1746, 20 January: Musschenbroek describes the experiment in a letter to Réaumur.
• 1746: Nollet stages mass shock demonstrations in France; Gralath links jars together.
• 1747: Watson and Bevis improve the jar with metal foil coatings.
• 1752, June: Franklin charges a Leyden jar from a thundercloud with his kite.
• 1800: Volta’s pile provides the first continuous electric current.

Why it matters

The Leyden jar turned electricity from a fleeting curiosity into something that could be stored, measured and studied. It made possible the experiments that linked electricity with lightning and prepared the way for the electrical science of the nineteenth century.