William Jones (mathematician)

William Jones (1675 to 1749) was a Welsh mathematician best known for using the Greek letter pi to stand for the ratio of the circumference of a circle to its diameter. He was a close friend of Isaac Newton and Edmund Halley. Born on Anglesey, the son of a farmer, he attended a charity school at Llanfechell, where the local landowner Lord Bulkeley noticed his talent and found him work in a London merchant's counting-house. He then served at sea, teaching mathematics aboard Navy ships from 1695 to 1702, and published A New Compendium of the Whole Art of Navigation in 1702, applying mathematics to the calculation of position at sea. Back in London he taught in coffee houses and tutored George Parker, the son of the future Earl of Macclesfield. His Synopsis Palmariorum Matheseos of 1706, written for beginners, used pi in this sense, and his Analysis per quantitatum series, fluxiones ac differentias of 1711 introduced the dot notation for differentiation. He became a fellow of the Royal Society in November 1711 and later its vice-president.