Pietro Mengoli

Pietro Mengoli (1626, Bologna – June 7, 1686, Bologna) was an Italian mathematician and clergyman from Bologna, where he studied with Bonaventura Cavalieri at the University of Bologna, and succeeded him in 1647. He remained as professor there for the next 39 years of his life.

Mengoli was pivotal figure in the development of calculus. He established the divergence of the harmonic series nearly forty years before Jacob Bernoulli, to whom the discovery is generally attributed; he gave a development in series of logarithms thirteen years before Nicholas Mercator published his famous treatise ''Logarithmotechnia''. Mengoli also gave a definition of the definite integral which is not substantially different from that given more than a century later by Augustin-Louis Cauchy. Provided by Wikipedia