Sir John Sealy Edward Townsend,
FRS (7 June 1868 – 16 February 1957) was an Irish-British
mathematical physicist who conducted various studies concerning the
electrical conduction
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
of gases (concerning the
kinetics
Kinetics ( grc, κίνησις, , kinesis, ''movement'' or ''to move'') may refer to:
Science and medicine
* Kinetics (physics), the study of motion and its causes
** Rigid body kinetics, the study of the motion of rigid bodies
* Chemical kin ...
of
electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have n ...
s and
ions) and directly measured the
electrical charge
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...
. He was a
Wykeham Professor
The University of Oxford has three statutory professorships named after William of Wykeham, who founded New College.
Logic
The Wykeham Professorship in Logic was established in 1859, although it was not known as the Wykeham chair until later. ...
of physics at
Oxford University
Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to the ...
.
The phenomenon of the electron avalanche was discovered by him, and is known as the
Townsend discharge
The Townsend discharge or Townsend avalanche is a gas ionisation process where free electrons are accelerated by an electric field, collide with gas molecules, and consequently free additional electrons. Those electrons are in turn accelerated an ...
.
Career
John Townsend was born at
Galway
Galway ( ; ga, Gaillimh, ) is a City status in Ireland, city in the West Region, Ireland, West of Ireland, in the Provinces of Ireland, province of Connacht, which is the county town of County Galway. It lies on the River Corrib between Lo ...
in
County Galway
"Righteousness and Justice"
, anthem = ()
, image_map = Island of Ireland location map Galway.svg
, map_caption = Location in Ireland
, area_footnotes =
, area_total_km2 = ...
, Ireland, son of Edward Townsend, a Professor of Civil Engineering at
Queen's College Galway and Judith Townsend. In 1885, he entered
Trinity College Dublin
, name_Latin = Collegium Sanctae et Individuae Trinitatis Reginae Elizabethae juxta Dublin
, motto = ''Perpetuis futuris temporibus duraturam'' (Latin)
, motto_lang = la
, motto_English = It will last i ...
, was
elected a Scholar of the College in 1888, and came top of the class in mathematics with a BA in 1890. He became a
Clerk Maxwell Scholar and entered
Trinity College, Cambridge
Trinity College is a constituent college of the University of Cambridge. Founded in 1546 by King Henry VIII, Trinity is one of the largest Cambridge colleges, with the largest financial endowment of any college at either Cambridge or Oxford. ...
, where he became a research student at the same time as
Ernest Rutherford
Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand physicist who came to be known as the father of nuclear physics.
''Encyclopædia Britannica'' considers him to be the greatest ...
. At the
Cavendish laboratory
The Cavendish Laboratory is the Department of Physics at the University of Cambridge, and is part of the School of Physical Sciences. The laboratory was opened in 1874 on the New Museums Site as a laboratory for experimental physics and is named ...
, 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
The Townsend discharge or Townsend avalanche is a gas ionisation process where free electrons are accelerated by an electric field, collide with gas molecules, and consequently free additional electrons. Those electrons are in turn accelerated an ...
" circa 1897). This work determined the
elementary electrical charge with the droplet method. This method was improved later by
Robert Andrews Millikan
Robert Andrews Millikan (March 22, 1868 – December 19, 1953) was an American experimental physicist honored with the Nobel Prize for Physics in 1923 for the measurement of the elementary electric charge and for his work on the photoelectric ...
.
In 1900, Townsend became a
Wykeham Professor
The University of Oxford has three statutory professorships named after William of Wykeham, who founded New College.
Logic
The Wykeham Professorship in Logic was established in 1859, although it was not known as the Wykeham chair until later. ...
of Physics at
Oxford
Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to the ...
. In 1901, he discovered the ionization of molecules by ion impact and the dependence of the mean free path on
electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have n ...
s (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 11 June 1903, he was elected to
Fellow of the Royal Society
Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural knowledge, including mathemati ...
(FRS).
He was awarded the
Hughes Medal
The Hughes Medal is awarded by the Royal Society of London "in recognition of an original discovery in the physical sciences, particularly electricity and magnetism or their applications". Named after David E. Hughes, the medal is awarded wit ...
in 1914. During
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
, he researched, at
Woolwich
Woolwich () is a district in southeast London, England, within the Royal Borough of Greenwich.
The district's location on the River Thames led to its status as an important naval, military and industrial area; a role that was maintained thr ...
,
wireless
Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...
methods for the
Royal Naval Air Service
The Royal Naval Air Service (RNAS) was the air arm of the Royal Navy, under the direction of the Admiralty's Air Department, and existed formally from 1 July 1914 to 1 April 1918, when it was merged with the British Army's Royal Flying Corps t ...
.
Townsend was a laboratory demonstrator when
Brebis Bleaney
Brebis Bleaney (6 June 1915 – 4 November 2006) was a British physicist. His main area of research was the use of microwave techniques to study the magnetic properties of solids. He was head of the Clarendon Laboratory at the University of O ...
was an undergraduate. Bleaney recounts an occasion when Townsend gathered together all the demonstrators and proceeded to refute both quantum mechanics and relativity.
Between the two world wars, Townsend led an effective small group of researchers, often
Rhodes scholar
The Rhodes Scholarship is an international postgraduate award for students to study at the University of Oxford, in the United Kingdom.
Established in 1902, it is the oldest graduate scholarship in the world. It is considered among the world' ...
s, of whom some became distinguished physicists. However, by the 1930s he had become less effective. He was seen as a boring lecturer, a dogmatic supervisor, and out of touch with the wider world of physics. As the 1930s went on, no German refugees sought refuge in his laboratory, while
Lindemann Lindemann is a German surname.
Persons
Notable people with the surname include:
Arts and entertainment
* Elisabeth Lindemann, German textile designer and weaver
*Jens Lindemann, trumpet player
* Julie Lindemann, American photographer
* Maggie ...
, Dr Lee's professor of Physics, gained eight refugee physicists, some of whom gave his department an international reputation in the world of
low temperature physics. In the late 1930s, the University decided to build a new
Clarendon Laboratory
The Clarendon Laboratory, located on Parks Road within the Science Area in Oxford, England (not to be confused with the Clarendon Building, also in Oxford), is part of the Department of Physics at Oxford University. It houses the atomic and ...
Building and looked closely at the relations between Oxford's two physics laboratories. There was a suggestion to convert the Wykeham chair into one for
theoretical physics
Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experim ...
. In 1941, Townsend's career came to an unhappy end. He had refused to support the
war effort
In politics and military planning, a war effort is a coordinated mobilization of society's resources—both industrial and human—towards the support of a military force. Depending on the militarization of the culture, the relative si ...
by teaching service-men, and the university appointed a visitorial board. This found Townsend guilty of misconduct and advised him that he would be dismissed unless he agreed to resign. Townsend, knighted in January 1941, resigned in September, subject to confidentiality.
John Townsend spent his retirement in
Oxford
Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to the ...
, where he died in 1957 in the
Acland Nursing Home
The Acland Hospital (also previously known as the Acland Nursing Home, Acland Home and the Sarah Acland Home for Nurses) was a private nursing home and hospital in central North Oxford, England, located in a prominent position at the southern en ...
.
Townsend married May Georgiana Lambert, also from County Galway, and they had two sons. His wife took an interest in politics, became a city councillor, and was twice
Mayor of Oxford
The earliest recorded Mayor of Oxford in England was Laurence Kepeharm (1205–1207?).
On 23 October 1962 the city was granted the honour of electing a Lord Mayor. Notable figures who have been Lord Mayor of Oxford include J. N. L. Baker (196 ...
.
Works
* ''The Theory of Ionisation of Gases by Collision'' (1910)
* ''Motion of Electrons in Gases'' (1925)
* ''Electricity and Radio Transmission'' (1943)
* ''Electromagnetic Waves'' (1951)
See also
*
Townsend Building of the Clarendon Laboratory in Oxford
References
Further reading
*
*
External links
*
* "
Papers and correspondence of Sir John Sealy Edward Townsend 1868–1957''".
Bodleian Library
The Bodleian Library () is the main research library of the University of Oxford, and is one of the oldest libraries in Europe. It derives its name from its founder, Sir Thomas Bodley. With over 13 million printed items, it is the sec ...
, Oxford. (''ed''. compiled between 1914 and 1957.)
Entry in The Townsend (Townshend) Family Records
{{DEFAULTSORT:Townsend, John Sealy
1868 births
1957 deaths
Alumni of Trinity College, Cambridge
Alumni of Trinity College Dublin
British physicists
Electrical breakdown
Fellows of New College, Oxford
Fellows of the Royal Society
Knights Bachelor
People associated with electricity
People from Galway (city)
Scholars of Trinity College Dublin
Wykeham Professors of Physics