Discovery of the Leyden jar

Artist's conception of the discovery of the Leyden jar by Cunaeus and Muschenbroek, apparently in late 1845. Andreas Cunaeus, a pupil of Pieter von Muschenbroek in Leyden, attempted to "condense" electricity in a glass of water. The rotating glass sphere (right) is an electrostatic machine. The static electricity generated by the hands rubbing on it is transferred through the chain to the suspended metal bar, and from it via the hanging wire into the glass of water. The glass acted as a capacitor; a large charge built up in the water, and an equal charge of the opposite polarity built up in Cunaeus' hand holding the glass. When Cunaeus reached up to pull the wire out of the water, he got a severe shock, much worse than an electrostatic machine could give, because the amount of charge stored was much larger than the terminal of an electrostatic machine could store. Cunaeus took 2 days to recover. Musschenbroek was similarly impressed by the powerful shock he received from the device. Reports of the experiment were widely circulated, and scientists began to investigate the charge storage ability of these "Leyden flasks." Eventually the water was replaced by foil coatings on the inside and outside of the jar to store the charge. (Source: Deschanel AP. Elementary Treatise on Natural Philosophy. Part 3: Electricity and Magnetism. Translated and edited by JD Everett. New York: D. Appleton and Co., 1876:570. Figure 382. Public domain.)