William Jones | |
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Born | 1675 |

Died | 3 July 1749 (aged 73–74)
London, England |

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mathematical constant π |
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3.1415926535897932384626433... |

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**William Jones**,
FRS (1675 – 1 July 1749^{
[1]}) was a Welsh
mathematician, most noted for his use of the symbol π (the
Greek letter *
Pi*) to represent
the ratio of the circumference of a circle to its diameter. He was a close friend of Sir
Isaac Newton and Sir
Edmund Halley. In November 1711, he became a Fellow of the
Royal Society, and was later its vice-president.^{
[2]}

William Jones was born the son of Siôn Siôr (John George Jones) and Elizabeth Rowland in the parish of
Llanfihangel Tre'r Beirdd, about 4 miles (6.4 km) west of
Benllech on the
Isle of Anglesey in Wales. He attended a
charity school at
Llanfechell, also on the Isle of Anglesey, where his mathematical talents were spotted by the local landowner Lord Bulkeley, who arranged for him to work in a merchant's counting-house in
London.^{
[3]} His main patrons were the
Bulkeley family of north
Wales, and later the
Earl of Macclesfield.^{
[4]}

Jones initially served at sea, teaching mathematics on board Navy ships between 1695 and 1702, where he became very interested in navigation and published *A New Compendium of the Whole Art of Navigation* in 1702,^{
[3]} dedicated to a benefactor
John Harris.^{
[5]} In this work he applied mathematics to navigation, studying methods of calculating position at sea. After his voyages were over he became a mathematics teacher in London, both in coffee houses and as a private tutor to the son of the future Earl of Macclesfield and also the future
Baron Hardwicke. He also held a number of undemanding posts in government offices with the help of his former pupils.^{[
citation needed]}

Jones published *Synopsis Palmariorum Matheseos* in 1706, a work which was intended for beginners and which included theorems on
differential calculus and
infinite series. This used π for the ratio of circumference to diameter, following earlier abbreviations for the Greek word *periphery* (περιφέρεια) by
William Oughtred and others.^{
[6]}^{
[7]}^{
[8]}^{
[9]}^{
[10]} His 1711 work *Analysis per quantitatum series, fluxiones ac differentias* introduced the dot notation for
differentiation in calculus.^{
[11]}

He was noticed and befriended by two of Britain's foremost mathematicians –
Edmund Halley and
Sir Isaac Newton – and was elected a fellow of the Royal Society in 1711. He later became the editor and publisher of many of Newton's manuscripts and built up an extraordinary library that was one of the greatest collections of books on science and mathematics ever known, and only recently fully dispersed.^{
[12]}

He married twice, firstly the widow of his counting-house employer, whose property he inherited on her death, and secondly, in 1731, Mary, the 22-year-old daughter of cabinet-maker George Nix, with whom he had two surviving children. His son, also named
William Jones and born in 1746, was a renowned
philologist who established links between Latin, Greek and Sanskrit, leading to the concept of the
Indo-European language group.^{
[13]}

**^**Roberts, Gareth Ffowc (2020).*Cyfri'n Cewri*. University Press Wales. p. 57. ISBN 978-1786835949.**^**"Library and Archive catalogue". Royal Society. Retrieved 1 November 2010.^{[ permanent dead link]}- ^
^{a}^{b}"Jones biography". University of St. Andrews. Retrieved 12 December 2010. **^***Cyfri'n Cewri*by Gareth Ffowc Roberts; University of Wales Press (2020); p. 14.**^**William Jones (1702).*A New Compendium of the Whole Art of Navigation*. Retrieved 3 February 2011.**^**Jones, William (1706).*Synopsis Palmariorum Matheseos : or, a New Introduction to the Mathematics*. pp. 243, 263.**^**Rothman, Patricia (7 July 2009). "William Jones and his Circle: The Man who invented Pi".*History Today*. Retrieved 6 October 2017.**^**Roberts, Gareth Ffowc (14 March 2015). "Pi Day 2015: meet the man who invented π".*The Guardian*. ISSN 0261-3077. Retrieved 6 October 2017.**^**Bogart, Steven. "What is pi, and how did it originate?".*Scientific American*. Archived from the original on 6 October 2017. Retrieved 6 October 2017.**^**Archibald, R. C. (1921). "Historical Notes on the Relation ".*The American Mathematical Monthly*.**28**(3): 121. doi: 10.2307/2972388. JSTOR 2972388.It was probably suggested to Jones by Oughtred who employed the symbol in a different sense.

**^**Garland Hampton Cannon (1990).*The life and mind Oriental Jones*. Retrieved 3 February 2011.**^**"How a farm boy from Wales gave the world pi". The Conversation. Retrieved 14 March 2017.**^**Roberts, Gareth Ffowc (14 March 2015). "Pi Day 2015: meet the man who invented π".*The Guardian*. Retrieved 14 March 2015.

- William Jones and other important Welsh mathematicians
- William Jones and his Circle: The Man who invented Pi
- Pi Day 2015: meet the man who invented π