Pietro Mengoli

Pietro Mengoli was an Italian mathematician and clergyman from Bologna, born in 1626, where he studied with Bonaventura Cavalieri at the University of Bologna and succeeded him in 1647, remaining as professor there for the next 39 years of his life. He was a pivotal figure in the development of calculus: he established the divergence of the harmonic series nearly forty years before Jacob Bernoulli, gave a development in series of logarithms thirteen years before Nicholas Mercator published Logarithmotechnia, and gave a definition of the definite integral not substantially different from that given more than a century later by Augustin-Louis Cauchy. He was ordained a Catholic priest in 1660 and died on June 7, 1686.