John Wallis

John Wallis (1616-1703) was an English mathematician, theologian, and a prominent figure in the development of calculus. He is best known for his work in representing numbers and functions using infinite series, and he contributed to the fields of algebra, geometry, and physics. Wallis is often credited with the introduction of the concept of limits and the use of the integral sign, which resembles an elongated 'S', to denote sums.