J. S. E. Townsend

For other people named John Townsend, see John Townsend (disambiguation).

Sir John Townsend FRS
Born	John Sealy Edward Townsend (1868-06-07)7 June 1868 Galway, Ireland, UKGBI
Died	16 February 1957(1957-02-16) (aged 88) Oxford, England, UK
Alma mater	Trinity College Dublin (BA) Trinity College, Cambridge (MA)
Known for	Townsend discharge Ramsauer–Townsend effect
Spouse	Mary Lambert ​ (m. 1911)​
Children	2
Awards	Hughes Medal (1914)
Scientific career
Fields	Electromagnetism
Institutions	University of Oxford (1900–1941)
Academic advisors	J. J. Thomson
Doctoral students	Victor Albert Bailey (1923) Henry Brose (1925) Robert Van de Graaff (1928)
Signature

Sir John Sealy Edward Townsend (7 June 1868 – 16 February 1957) was a British physicist who conducted various studies concerning the electrical conduction of gases (concerning the kinetics of electrons and ions) and directly measured the electric charge of the electron. He served as the first Wykeham Professor of Physics at the University of Oxford from 1900 until 1941.

Education

John Sealy Edward Townsend was born on 7 June 1868 in Galway, Ireland, the son of Judith (née Townsend) and Edward Townsend, Professor of Civil Engineering at Queen's College Galway. His parents were distant cousins.

In 1885, Townsend entered Trinity College Dublin, where he was elected a Scholar in 1888 and graduated with first place in Mathematics in 1890. He was then admitted to Trinity College, Cambridge, as a research student of J. J. Thomson in the Cavendish Laboratory. There, he supplied important work to the electrical conductivity of gases, now known as the Townsend discharge. This work determined the elementary charge with the droplet method; this method was improved later by Robert Millikan. He was made a Clerk Maxwell Scholar in 1898 and was elected a Fellow of Trinity College the following year. He obtained an M.A. in 1903.

Career in Oxford

In 1900, Townsend was appointed to the newly established Wykeham Professorship of Physics at the University of Oxford.

In 1901, Townsend discovered the ionisation 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).

During the First World War, Townsend researched wireless methods for the Royal Naval Air Service.

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.

Between the two world wars, Townsend led an effective small group of researchers, often Rhodes scholars, 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 Professor Frederick Lindemann gained 8 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 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.

In 1941, Townsend's career came to an unhappy end; he had refused to support the war effort by teaching service-men, and the university appointed a visitorial board. This found him guilty of misconduct and advised him that he would be dismissed unless he agreed to resign. He was knighted in January and resigned in September, subject to confidentiality.

Personal life and death

On 5 June 1911 in Dublin, Townsend married Mary Georgiana Lambert, with whom he had two sons; Edward (born 7 August 1912) and John (born 7 June 1914). The family lived at 20 Merton Street in Oxford.

Townsend died on 16 February 1957 in Oxford at the age of 88.

Recognition

Memberships

Country	Year	Institute	Type	Ref.
United Kingdom	1903	Royal Society	Fellow

Awards

Country	Year	Institute	Award	Citation	Ref.
United Kingdom	1914	Royal Society	Hughes Medal	"For his researches on electric induction in gases"

Chivalric titles

Country	Year	Monarch	Title	Ref.
United Kingdom	1941	George VI	Knight Bachelor

Commemorations

The Townsend Building of the Clarendon Laboratory at the University of Oxford is named after him, as well as the townsend unit.

Books

• Townsend, J. S. (1910). The Theory of Ionisation of Gases by Collision. Constable & Co., London.

• Townsend, J. S. (1915). Electricity in Gases. Clarendon Press, Oxford.

• Townsend, J. S. (1925). Motion of Electrons in Gases. OCLC 499998759.

• Townsend, J. S. (1943). Electricity and Radio Transmission. OCLC 2196307.

• Townsend, J. S. (1951). Electromagnetic Waves. OCLC 5691111.

Further reading

• Barker, Philip (2002). Top 1000 Scientists: From the Beginning of Time to 2000 AD. Universities Press. ISBN 81-7371-210-7.
• McCartney, & Whitaker (2003). Physicists of Ireland. Taylor & Francis. ISBN 0-7503-0866-4.

External links

• J. S. E. Townsend at the Mathematics Genealogy Project
• "Papers and correspondence of Sir John Sealy Edward Townsend, 1868–1957". Bodleian Library, Oxford. (ed. compiled between 1914 and 1957.)
• Entry in The Townsend (Townshend) Family Records