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: "Towards the year 1676, Monsieur Picard was transporting his barometer from the Observatory to Port Saint Michel during the night, henhe 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. 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:

# 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).
# 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).
# Jean-Jacques Dortous de Mairan, "Sur la cause de la lumière des phosphores et des notiluques" (Bordeaux, France: 1717).
# Wilhelm Bernard Nebel, "Dissertatio physica de mercurio lucente in vacuo sub praesidio J. Bernoulli" issertation on the physics of the mercurial light in vacuum under the patronage of J. Bernoulli(Basil, Switzerland: 1719).
# 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).
# Anders Celsius (1724
"Observatio de lumine in barometro,"
''Acta Literaria Sueciae'', 1 : 601.
# Johann Heinrich Winkler
''Gedanken von den Eigenschaften, Wirkungen und Ursachen der Electricität, nebst einer Beschreibung zwo neuer electrischen Maschinen''
houghts on the properties, effects, and causes of electricity, together with a description of two new electrical machines(Leipzig, Germany: Bernhard Christoph Breitkopfs, 1744).
# 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).
# 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.
# Giovanni Battista Beccaria, ''Dell'Elettricismo Artificale, e Naturale'' (Turin, Italy: Filippo Antonio Campana, 1753)
p. 182

# Franciscus Ulricus Theodorus Aepinus (1768
"De electricitate barometrorum disquisitio,"
''Novi Commentarii Academiae Scientiarum Imperialis Petropolitanae'' ew Memoirs of the Imperial Academy of Sciences at St. Petersburg 12 : 303-324 .

References

External links

{{EB1911 poster, Barometric Light
History of the development of the concept of the electric charge

Lighting
Luminescence
Meteorological instrumentation and equipment
Mercury (element)
Electrostatics