John Sealy Townsend

John Sealy Townsend

Infobox Scientist
box_width = 300px
name = John Townsend

image_size = 300px
caption = John Sealy Edward Townsend (1868-1957)
birth_date = birth date|1868|6|7|mf=y
birth_place = Galway, County Galway, Ireland
death_date = death date|1957|2|16|mf=y
death_place = Oxford, England
citizenship = United Kingdom of Great Britain and Ireland
fields = Physicist
workplaces = Oxford University
alma_mater = Trinity College, Dublin
Cambridge University
doctoral_advisor =
academic_advisors = J. J. Thomson
doctoral_students = Victor Albert Bailey
Henry Brose
notable_students =
known_for = Townsend discharge
Ramsauer-Townsend effect
Townsend (unit)
author_abbrev_bot =
author_abbrev_zoo =
influences =
influenced =
awards = Hughes Medal (1914)
religion =

footnotes =

John Sealy Edward Townsend (7 June 1868 - 16 February 1957) was a mathematical physicist who conducted various studies concerning the electrical conduction of gases (concerning the kinetics of electrons and ions) and directly measured the electrical charge. He was a Wykeham Professor of physics at Oxford University.


He was born in Galway, County Galway, Ireland, son of Edward Townsend, a Professor of Civil Engineering at Queen's College, Galway. In 1885, he entered Trinity College Dublin and came top of the class in maths with a BA in 1890. He became a Clerk Maxwell Scholar and entered Trinity College, Cambridge where he became a research student at the same time as Ernest Rutherford.At the Cavendish laboratory, he studied under J. J. Thomson. He developed the "Townsend's collision theory". Townsend supplied important work to the electrical conductivity of gases ("Townsend discharge" circa 1897). This work determined the elementary electrical charge with the droplet method. This method was improved later by Robert Andrews Millikan.

In 1900, he became a professor at Oxford. In 1901, he discovered the ionization of molecules by ion impact and the dependence of the mean free path on electrons (in gases) of the energy (and his independent studies concerning the collisions between atoms and low-energy electrons in the 1920s would later be called the Ramsauer-Townsend effect). On June 11, 1903, he was elected to Fellow of the Royal Society (FRS). He was awarded the Hughes Medal in 1914. During World War I, he researched (at Woolwich, London, England) wireless methods for the Royal Navy Air Service. He was knighted in 1941. He died in Oxford, England.

He married May Georgina, also from County Galway, and they had two sons.

Townsend was a laboratory demonstrator when Brebis Bleaney was an undergraduate. Bleaney recounts an occasion when Townsend gathered together all the demonstrators and proceeded to refute both quantum mechanics and relativity.


* "The Theory of Ionisation of Gases by Collision" (1910)
* "Motion of Electrons in Gases" (1925)
* "Electricity and Radio Transmission" (1943)
* "Electromagnetic Waves" (1951)


*"Top 1000 Scientists: From the Beginning of Time to 2000 AD" Philip Barker ISBN 81-7371-210-7
*A. von Engel "John Sealy Edward Townsend. 1868-1957," "Biographical Memoirs of Fellows of the Royal Society", Vol. 3, Nov., 1957, pp. 256-272.
*B. Bleaney, "Two Oxford Science Professors, F. Soddy and J. S. E. Townsend," "Notes and Records of the Royal Society of London," Vol. 56, No. 1, 2002, pp. 83-88

External links

* " [ Papers and correspondence of Sir John Sealy Edward Townsend] , 1868-1957". Bodleian Library, Oxford. ("ed". compiled between 1914-1957.)
* [ Entry in The Townsend (Townshend) Family Records]

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