Leyden jar in a vacuum bell, or ‘luminous matras’

The Leyden jar can be regarded as the first electrical capacitor because it accumulates electricity and produces a charge. The Dutch scientist Pieter van Musschenbroek conceived the first jars in Leyden in 1745. The following year the French physicist Nollet demonstrated the invention to Louis XV by electrifying a chain of 180 royal guards in the Hall of Mirrors at Versailles. The scientist noted that the power of the charge remained constant despite the great number of individuals who received the electrical ‘shock’. He published his observations in Lettres sur l’électricité (Letters on electricity) in 1753. The specificity of this Leyden jar is that it is inside a bell in which a vacuum can be created to study the effects of an electrical charge without air.