Pieter (Petrus) van Musschenbroek
born on 14 March 1692 in Leiden, Netherlands
died on 19 September 1761 in Leyden

Dutch physicist Pieter van Musschenbroek discovered "capacitance". He invented the Leyden jar, a device that stored electric charge, was constructed by placing water in a metal container suspended by insulating silk cords, and placing a brass wire through a cork into the water. The same device was invented independently by von Kleist at about the same time, but not published.

Pieter van Musschenbroek was born on 14 March 1692 in Leiden, Netherlands, where his father Johann Joosten van Musschenbroek (1660-1707) was a maker of physical apparatus. At the time of Petrus' (Pieter's) birth the family was turning to the making of scientific instruments (air pumps, microscopes, and telescopes) which may explain in part his interest in science.

Petrus van Musschenbroek passed the Latin school in 1708, speaking Greek, Latin, French, English, high German, Italian and Spanish. He studied at the University of Leyden (Leiden) where he was a pupil and friend of W.J. Gravesande. Petrus van Musschenbroek received his degree in medicine in 1715 with a dissertation De aeris praesenhia in humoribus animalium. Subsequently he went to London where he followed lectures of Desagulier and Isaac Newton. He finalized his study in Philosophy (physics) in 1719. From 1719 to 1723 he was professor in Mathematics and Philosophy in Duisberg (Germany) where he worked with Fahrenheit. In 1721 he was also appointed as professor in Medicine. In 1731 Musschenbroek declined an invitation to Copenhagen, and was promoted to the chair of astronomy at Utrecht in 1732. Finally, he succeeded Willem Jacob Gravesande and accepted the mathematical chair at Leiden in 1739, where, declining all offers from abroad, he remained till his death. Musschenbroek was elected a Fellow of the Royal Society of London in 1734, and member of the French Academy of Sciences in the same year. Also, he was a member of Societies of Sciences in Montpellier, Berlin and Stockholm. In 1754 he was appointed as honorary professor at the Imperial Academy of Science in St. Petersburg.

Petrus van Musschenbroek was married on 16 July 1724 with Adriana van de Water (born 19 January 1694, died Utrecht 8 May 1732; daughter of Willem and Maria Ouzeel). Second time he was married again in 1738 with Helena Alstorphius (born 12 July 1692, died in Leiden 3 December 1760 in Leiden). From this marriage he had two children: Maria van Musschenbroek (born Utrecht 1 May 1725, married to Prof. Rev. Herman van Alphen, died in Hanau 25 January 1767) and Jan Willem van Musschenbroek

Petrus van Musschenbroek

Adriana van de Water, the first wife


Petrus van Musschenbroek provided the first approach to scientific study of electrical charge and its properties. In 1729, he used the word "physics" which had never been used before (William Whewell of England coined the terms science, physicist/physics in 1840). Also, Petrus van Musschenbroek made contributions in magnetism and cohesion of bodies and invented a pyrometer.

Friction machines were the only means of artificially producing electricity early in the eighteenth century, and although several men had suspected that the sparks and flashes of the friction machines were similar to lightning, no one had demonstrated the relation. Dutch and German scientists, like others of the time, had produced electricity by friction but like the others were unable to collect and retain it.

Workers in electricity in the eighteenth century wanted a convenient way to trap and accumulate as much charge as possible on a substance, but were without a convenient or simple way to do this. A condenser (capacitor) is a device of two flat metal plates fixed parallel and with a small separation or distance between them. The separation between the two plates is created by some dielectric or insulation substance (e.g. glass, mica, paper). Such a device can maintain an electrical charge that is varied by its size and material construction. In 1745-1746, research in electricity was facilitated by the creation of a device capable of storing energy and to conserve quantities of charge for later use. Today, this device of 1745-1746 is recognized as the first condenser (capacitor), but historically it is known as the Leyden jar. The Leyden jar was an immediate sensation to both scientists and nonscientists throughout the world. The invention of the Leyden jar was perhaps the greatest single advance in electricity of the eighteenth century, and furnished a new tool for physicians to use as a fresh approach to using electricity in treatments of disease and to electrical experimentation.

Historically, claims of creation or invention are often related to timing or circumstances; such may be the case here. The problem in crediting the invention of the Leyden jar is related to the date of the event and how it was perceived by others at the time and ever since.

Before 1745, Bose in Germany had the idea of drawing sparks or electrical fire from water in a glass vessel that was electrified, but nothing ever resulted other than an idea. Musschenbroek may have followed up on a method used by Andreas Gordon of Scotland. Gordon had described an experiment in which he connected a prime conductor with a metal wire to a jar filled with water.

Musschenbroek working with Leyden jar

With his friction machine Musschenbroek began investigating the force of electricity and observed that charged substances soon lost their electricity in open air. He reasoned that nonconducting materials surrounding charged substances were responsible for the loss of electrical charge. In one experiment he poured water into a glass jar for the purpose of studying charged substances such as the jar. No results were obtained until Musschenbroek apparently changed places with Andreas Cunaeus (an assistant) who was holding the end of a piece of brass wire dipped into the water filled glass vase. While examining the device with his left hand, and using his right hand as a rubber for producing friction by rapidly rotating the glass globe of an electrical machine, the left hand caused the jar to discharge. He had made connection between the two surfaces of the jar (closing the electrical circuit).


Discharging Leyden jar

In their attempts of November 1745 to produce sparks and flashes by friction that Gilbert, von Guericke, Hauksbee, and Du Fay had previously done experimentally, professors Petrus (Pieter) Musschenbroek and Jean Allamand of the University of Leyden and friend Cunaeus experimented with a glass jar connected to an friction electrical machine. Musschenbroek had suspected that a nonconductor vessel (glass) would be helpful to them so on this occasion in January 1746 he partly filled a bottle with water. He knew that water was a conductor of electricity. Musschenbroek, while holding the jar with his right hand and a piece of wire with his left hand had one of his assistants connect it to the friction electrical machine, and then turn its glass globe, but nothing occurred until Cuneus placed one end of the wire into the water while Musschenbroek, grounded, was still holding the wire. A violent shock was felt which Musschenbroek described. The jar device had accumulated the electricity produced by the static machine and then all at once it discharged to Musschenbroek.

Van Musschenbroek stated that he suffered through a terrible experience when receiving a shock of electricity produced by human hands. He further stated that the event could hardly be expressed and that the whole kingdom of France could not get him to receive another shock. He was shocked in his arms, shoulders, and chest,  and lost his breath in this laboratory event. The professor, assisted by Cunaeus (a student or lawyer friend) and Allamand (natural philosopher assisting), had just invented the Leyden jar (named later by Abbe Nollet of France in Musschenbroek's honor and city of residence in Leiden, the Netherlands). Because van Musschenbroek continued to experiment with electricity and the famous jar, he no doubt is rewarded historically for his persistence, thus invention of the Leyden jar. Musschenbroek observed, what von Kleist had not, that only the person holding the jar or conductor (wire) received the shock, and that his right hand served as a conductor (later replaced with a conductive coating on the outside of the jar), and that the jar had to be grounded (person holding jar had to have feet on the ground).

Musschenbroek immediately reported his experiment and events to Rene Reaumur of Paris who was his appointed correspondent to the Paris Academy of Sciences. Musschenbroek's vague letter written in Latin to Reaumur in January 1746, and was translated by Abbe J.A. Nollet. Joseph Priestley's account (The History and Present State of Electricity) credits Musschenbroek, but was written 20 years after the discovery and was told to him by an unknown source. Heilbron claimed that the experiments of Musschenbroek set the stage for the invention.

Musschenbroek announced the discovery in January, 1746.  However, a letter dated February 4, 1745, appearing in Philosophical Transactions suggests that the jar existed in Musschenbroek's laboratory almost a year before that date.  There is still some controversy about this but  the generally held opinion is:  "Trembley, the editor, or the composter of the letter in PT either misdated the letter, or failed to translate properly into the new style (NS).  Until 1752 the English began their legal year on March 25 so that, roughly speaking, their dates were a year behind continental ones for the first quarter of every continental year." This makes sense because there would be no reason for Musschenbroek and his staff to delay announcing for 11 months, especially given the potential claim to prior discovery by Von Kleist. Trembley's letter is fascinating as it is one of the earliest first-hand accounts of this new discovery. He happened to be in  Holland about the time of the discovery and his letter was the first word to England of the marvelous new jar.

In April 1746, Musschenbroek's experiment was presented to members of the Paris Academy by Reaumur. Reaumur was cautious enough to confirm the authenticity of Musschenbroek's experiment before presenting it to the Academy.

Leyden Jars are primitive capacitors. They could store several sparks from an electric machine. The charge would then be released later, all at one time, giving a much greater shock than a single spark from the machine could. Actually, the Leyden jar was a glass container, with water on the inside and von Musschenbroek's hand on the outside. This was later changed to a glass container with metal foil on the inside and outside.

The credit for creation of the Leyden jar has varied. Some writers give credit to Ewald Jurgen von Kleist, a German, while others claim that van Musschenbroek, a Dutch physicist, was the real inventor. A few authors give credit to both personalities as well as to others. If dates could settle this issue (4 Nov. 1745 vs. Jan. 1746, respectively) then von Kleist would be the inventor, and van Musschenbroek would be the first to develop a working model of the first electrical storage devise. These men, working independently, discovered that electricity produced by an electrostatic machine could be accumulated. Both men were horrified and surprised when their newly created device discharged stunning them with a strong electrical shock.

Heilbron stated that Musschenbroek was not a creative type of experimenter, since his experiments were replications of those by his contemporaries and predecessors. Musschenbroek, following his usual experimental style, is alleged to have been repeating an experiment suggested by G.M. Bose in his Tentamina at the time of the discovery.

Heilbron offers the version that Cunaeus was assisting Musschenbroek in the experiment. In trying to repeat Bose's experiment Cunaeus accidentally created the Leyden jar. The water inside the glass jar should have been electrified with the jar resting on some type of insulation. Cunaeus ignored the insulation and accidentally grounded the outside surface of the glass jar which thus created the terrific shock.

The Leyden jar under such circumstances became the first condenser (capacitor). The electrical shocks received by von Kleist and van Musschenbroek from their condensers were probably not as strong as they described. Electricity was still mystical and not well understood at the time let on that no one had ever received an electrical shock with as much amplitude. The event was a complete surprise to each investigator and neither had ever felt as much current at one time. Some exaggeration had to be included in their claims and descriptions, since the strangeness and suddenness of the occurrence was unexpected by all.

Essai de Physique...  Vol I. Title Page and Frontispiece

Although Petrus van Musschenbroek is usually mentioned as the inventor of the Leyden Jar (capacitor), his role in history was mainly to spread the empirical (Newtonian) views in physics in Europe through his books. His book Elementa Physica (1726) was reprinted many times and translated in Swedish, Spanish, Italian, German and English. Other works are: Dissertationes physicae experimentalis et geometricae de magnete (1729); Tentamina experimentorum naturalium in Accademia del Cimento (1731); Institutiones physicae (1734 and later); The aeris praestantia in humoribus corporis humani (1739); Institutiones logicae (1764).

Musschenbroek's book "Elementa Physicae" with illustrations showing scientific instruments of that time

Petrus van Musschenbroek died in Leyden on 19 September 1761 and was buried in the grave of his second wife Helena Alstorphius in the Pieterskerk in Leiden.

This text has been compiled from the biographies of Musschenbroek available in the Internet:
( 1, 2, 3, 4, 5, 6, 7, 8, 9 )

(updated & corrected on May 22, 2004)