Leyden jar

The Leyden jar was invented twice, within months, by people who had never communicated. In October 1745, German cleric Ewald Georg von Kleist inserted a nail into a medicine bottle filled with alcohol and connected it to an electrostatic generator. When he touched the nail, he received a shock violent enough to make him stagger. In 1746, independently, Dutch scientist Pieter van Musschenbroek in Leiden discovered the same phenomenon and provided the demonstration that would give the device its name.

Both were trying to capture electricity in water—following experiments by Georg Matthias Bose that sent electrical charges through liquid to ignite alcohol vapors. Neither understood why their configurations worked. The key, invisible to them, was the capacitor effect: conductive surfaces separated by an insulating layer can store electrical charge. The glass bottle was the insulator; the water inside and the hand holding it outside were the conductors.

The crucial mistake that enabled discovery was holding the bottle. Previous experimenters had insulated their apparatus as standard practice. Andreas Cunaeus, a lawyer attempting to replicate Musschenbroek's work, ignored this convention. When he held his jar while charging it, he completed the circuit through his body and discovered the device could deliver a shock far exceeding anything previously experienced with static electricity.

Musschenbroek famously wrote that the whole kingdom of France could not compel him to repeat the experience. But others eagerly did. Benjamin Franklin used Leyden jars in his kite experiments. Abbé Nollet demonstrated chains of monks receiving shocks simultaneously, proving instantaneous transmission across distance.

Before the Leyden jar, electricity existed only at the moment of generation. The jar made electricity storable and portable. This capability transformed electrical research from producing sparks to studying properties. The jar was the first capacitor—the component that still stores charge in every electronic device.

Convergent discovery proved the conditions were ripe. Electrostatic generators had become sophisticated enough to produce significant charges. Glass technology provided the insulating material. The theoretical framework, though incomplete, had advanced to the point where storing electricity seemed achievable. Two independent investigators, following similar experimental paths, arrived at the same destination within months.