STIELTJES, THOMAS JAN

born 1856, Zwolle, Neth. died 1894, Toulouse, Fr. Dutch-born French mathematician who made notable contributions to the theory of series. He is remembered as the father of the analytic theory of continued fractions. Stieltjes was the son of a civil engineer and was educated at Delft. After six years of work at the observatory in Leiden, he accepted a position at the University of Groningen. He moved to France in 1885, received a doctorate there in the following year, and became a professor of mathematics at the University of Toulouse, where he remained for the rest of his life. In addition to his studies of divergent and conditionally convergent series, he made advances in the theory of Riemann's function, in number theory, and in the theory of spherical harmonics. He also proposed an important definition of the integral now usually combined with that of Bernhard Riemann and known as the RiemannStieltjes integral.