Barometric light

Barometric light is a name for the light that is emitted by a mercury-filled barometer tube when the tube is shaken. The discovery of this phenomenon in 1675 revealed the possibility of electric lighting.

The phenomenon and its explanation
The earliest barometers were simply glass tubes that were closed at one end and filled with mercury. The tube was then inverted and its open end was submerged in a cup of mercury. The mercury then drained out of the tube until the pressure of the mercury in the tube — as measured at the surface of the mercury in the cup — equaled the atmosphere's pressure on the same surface.

In order to produce barometric light, the glass tube must be very clean and the mercury must be pure. If the barometer is then shaken, a band of light will appear on the glass at the meniscus of the mercury whenever the mercury moves downward.

When mercury contacts glass, the mercury transfers electrons to the glass. Whenever the mercury pulls free of the glass, these electrons are released from the glass into the surroundings, where they collide with gas molecules, causing the gas to glow — just as the collision of electrons and neon atoms causes a neon lamp to glow.

History
Barometric light was first observed in 1675 by the French astronomer Jean Picard: "Experience fait à l'Observatoire sur la Barometre simple touchant un nouveau Phenomene qu'on y a découvert" [Experiment made at the [astronomical] observatory [in Paris] on a simple barometer concerning a new phenomenon that was discovered there], Le Journal des Sçavans [later: Journal des Savants ], page 112 (Paris edition) or page 126 (Amsterdam edition) (25 May 1676).

Original text: "On sçait que le Barometre simple n’est autre chose qu’un tuyau de verre scellé hermetiquement par le haut & ouvert par le bas, dans lequelle il y a du vif-argent qui se tient ordinairement dans certaine hauteur, le reste au dessus estant vuide. M. Picard en a un à l’Observatoire qui dans l’obscurité, lors qu’on le remuë assez pour faire balancer le vif-argent, fait comme des éclairs & jette une certaine lumiere entrecouppée qui remplit toute la partie du Tuyau où se fait le vuide; mais cela n'arrive à chaque balancement que lors que le vuide se fait, & dans la seule descente du vif-argent. On a tâché de faire la même experience sur divers autres Barometres de même composition; mais on n’a encore reüssi que sur un seul.  Comme on est resolu d’examiner la chose en toute maniere, nous en donnerons plus au long toutes les circonstances qu’on y découvrïra."

Translation: "It is known that the simple barometer is nothing more than a glass tube hermetically sealed at the top and open at the bottom, in which there is some quicksilver which ordinarily stays at a certain height, the remainder above being void. Mr. Picard has one of them at the Observatory, which in the dark, when one moves it enough to make the quicksilver jiggle, flashes like sparks and throws a certain flickering light which fills the entire part of the tube where it is void; but that happens during each swing only when there is a void and only during the descent of the quicksilver. The same experiment has been attempted with various other barometers of the same construction; but it has still been successful only with the one.  As it has been resolved to investigate the matter in every way, we will give in greater length everything that is discovered about it."

Available on-line (in French) here: Le Journal des Sçavans. Reprinted as: "Experience fait a l'observatoire sur le baromètre, touchant un nouveau phenomene que M. Picard y a decouvert" [Experiment performed at the observatory on the barometer, concerning a new phenomenon that Monsieur Picard discovered there], Mémoires de l'Académie Royale des Sciences de Paris, vol. 10, page 566. "Towards the year 1676, Monsieur Picard was transporting his barometer from the Observatory to Port Saint Michel during the night, [when] he noticed a light in a part of the tube where the mercury was moving; this phenomenon having surprised him, he immediately reported it to the sçavans, … "  The Swiss mathematician Johann Bernoulli studied the phenomenon while teaching at Groningen, the Netherlands, and in 1700 he demonstrated the phenomenon to the French Academy. See:
 * Johann Bernoulli, "Nouvelle maniere de rendre les baromètres lumineux" (New way of making barometers luminous), Mémoires de l'Académie Royale des Sciences de Paris for the year 1700. [Note:  This article was taken from a letter that Bernoulli wrote in 1707; however, it was published in the 1700 edition of the Mémoires de l'Académie Royale des Sciences de Paris, which were themselves published only in 1761.]  Available (in French) on-line at:  Institute de France:  Académie des sciences .  A summary of this article and account of Bernoulli's demonstration of the phenomenon before the Académie Royale appeared in:  "Sur la lumière du baromètre" [On the light of the barometer], Histoire de l'Académie Royale des Sciences, pages 5-8 (1700).  See also:  Histoire de l'Académie Royale des Sciences, pages 1-8 (1701).
 * Johann Bernoulli, "Nouveau phosphore" (New phosphorus [i.e., a substance that glows in the dark]), Mémoires de l'Académie Royale des Sciences de Paris, pages 1-9 (1701).
 * "Lettre de M. Bernoulli Professor à Groningue, touchant son nouveau Phosphore" (Letter from M. Bernoulli, professor at Groningen, concerning his new phosphorus), Mémoires de l'Académie Royale des Sciences de Paris, pages 137-146 (1701).
 * Edmund N. Harvey, A History of Luminescence: From the Earliest Times Until 1900 (Philadelphia, Pennsylvania: American Philosophical Society, 1957), pages 120, 271-277, 284, and 291.
 * In his article "Nouvelle maniere … ", Johann Bernoulli said that he learned of Picard's luminous barometer from the book: Joachim d'Alence, Traittez de Barométres, Thermométres, et Notiométres, ou Hygrométres (Amsterdam, Netherlands: Henry Wetstein, 1688), pages 50-52.  After learning of the phenomenon from Bernoulli, the Englishman Francis Hauksbee investigated the subject extensively.  Hauksbee showed that a complete vacuum was not essential to the phenomenon, for the same glow was apparent when mercury was shaken with air only partially rarefied, and that even without using the barometric tube, bulbs containing low-pressure gases could be made to glow via externally applied static electricity.  The phenomenon was also studied by contemporaries of Hauksbee, including the Frenchman Pierre Polinière  and a French mathematician, Gabriel-Philippe de la Hire, and subsequently by many others. Others who investigated barometric light include:


 * 1) Du Tal, "Pièce justificative pour M. Bernoulli contra Messieurs de l'Académie Royale des Sciences en faveur du phosphore, qu'il a proposé à cette Académie" (Evidence supporting Mr. Bernoulli against the gentlemen of the Royal Academy of Sciences in favor of the phosphor that he offered to that academy), Nouvelles de la République des Lettres, vol. 7, pages 243-255 (September 1706).
 * 2) Johann Michael Heusinger, Dissertatio de noctiluca mercuriali sive de luce quam argentum virum in tenebris fundit … (Dissertation on the mercurial night light, or on the light that quicksilver emits in the dark) (Giessen, Germany:  Muller, 1716).
 * 3) Jean-Jacques Dortous de Mairan, "Sur la cause de la lumière des phosphores et des notiluques" (Bordeaux, France: 1717).
 * 4) Wilhelm Bernard Nebel, "Dissertatio physica de mercurio lucente in vacuo sub praesidio J. Bernoulli" [Dissertation on the physics of the mercurial light in vacuum under the patronage of J. Bernoulli] (Basil, Switzerland: 1719).
 * 5) Charles François de Cisternay du Fay, "Sur les barometres lumineux" (On luminous barometers), Histoire de l’Académie Royale des sciences de Paris, pages 13 ff; also printed in: Mémoires de l’Académie Royale des sciences de Paris, pages 295-306 (1723).
 * 6) Anders Celsius (1724) "Observatio de lumine in barometro," Acta Literaria Sueciae, 1 : 601.
 * 7) Johann Heinrich Winkler, Gedanken von den Eigenschaften, Wirkungen und Ursachen der Electricität, nebst einer Beschreibung zwo neuer electrischen Maschinen [Thoughts on the properties, effects, and causes of electricity, together with a description of two new electrical machines] (Leipzig, Germany:  Bernhard Christoph Breitkopfs, 1744).
 * 8) Christian Friedrich Ludolff, le jeune, "Sur l’electricité des barometres," Mémoires de l’Académie Royale des Sciences et des Belles-Lettres de Berlin (Class physique), vol. I.b, pages 3-13 (1745).
 * 9) Abraham Trembley (1746) "Part of a letter from Mr. Trembley, F.R.S. to Martin Folkes, Esq., Pres. R.S. concerning the light caused by quicksilver shaken in a glass tube, proceeding from electricity," Philosophical Transactions of the Royal Society of London, 44 : 58-60.
 * 10) Giovanni Battista Beccaria, Dell'Elettricismo Artificale, e Naturale (Turin, Italy: Filippo Antonio Campana, 1753), p. 182.
 * 11) Franciscus Ulricus Theodorus Aepinus (1768) "De electricitate barometrorum disquisitio," Novi Commentarii Academiae Scientiarum Imperialis Petropolitanae [New Memoirs of the Imperial Academy of Sciences at St. Petersburg], 12 : 303-324.